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Solution and crystalline state photochemistry of 2,3-diacyl-substituted benzobarrelenes Yap, Melvin Peng-Kwun 1992

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SOLUTION AND CRYSTALLINE STATE PHOTOCHEMISTRY OF 2,3-DIACYL-SUBSTITUTED BENZOBARRELENES by M e l v i n Peng-Kwun Yap B . S c , U n i v e r s i t y o f B r i t i s h C o l u m b i a , Canada, 1986 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES (DEPARTMENT OF CHEMISTRY) We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t he r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA A p r i l 1992 © M e l v i n Peng-Kwun Yap, 1992 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of O^BMlSlil'^f The University of British Columbia Vancouver, Canada DE-6 (2/88) ABSTRACT A s e r i e s o f 2 , 3 - d i a c y l - s u b s t i t u t e d b e n z o b a r r e l e n e s was s y n t h e s i z e d and t h e i r p h o t o c h e m i s t r y i n v e s t i g a t e d i n the c r y s t a l l i n e s t a t e and i n s o l u t i o n media. The d i f f e r e n c e s i n p h o t o r e a c t i v i t y and p r o d u c t s e l e c t i v i t y between t h e s e compounds i n the two phases were d e t e r m i n e d , and s t r u c t u r e -r e a c t i v i t y c o r r e l a t i o n s were e s t a b l i s h e d b a s e d on X - r a y c r y s t a l l o g r a p h i c d a t a . The p h o t o c h e m i s t r y o f the t i t l e s e r i e s i s m u l t i p l i c i t y - d e p e n d e n t ; b e n z o c y c l o o c t a t e t r a e n e i s formed t h r o u g h t h e s i n g l e t e x c i t e d s t a t e and b e n z o s e m i b u l l v a l e n e s a r e p r o d u c t s o f the t r i p l e t e x c i t e d s t a t e . R e g i o i s o m e r i c b e n z o s e m i b u l l v a l e n e s a r e d e r i v e d from t h e d i f f e r e n t "di - T T -me th a n e " r e a r r a n g e m e n t pathways t a k e n . S o l u t i o n phase, t r i p l e t - s t a t e p h o t o i s o m e r i z a t i o n s o f a number o f s y m m e t r i c a l l y d i s u b s t i t u t e d b e n z o b a r r e l e n e s gave two b e n z o s e m i b u l l v a l e n e s -1 , 2 - d i s u b s t i t u t e d and 2 a , 6 c - d i s u b s t i t u t e d . S e l e c t i v i t y i s c o n t r o l l e d p r e d o m i n a n t l y by e l e c t r o n i c e f f e c t s . The use o f a b e n z o y l s u b s t i t u e n t as one o f t h e a c y l groups enhances i n t e r s y s t e m c r o s s i n g , t h e r e b y e n a b l i n g the s u b s t r a t e t o a c h i e v e t h e t r i p l e t e x c i t e d s t a t e t h r o u g h d i r e c t i r r a d i a t i o n . P h o t o l y s e s o f s e v e r a l u n s y m m e t r i c a l b e n z o y l / e s t e r b e n z o b a r r e l e n e s i n the s o l i d s t a t e gave s t r i k i n g l y u n u s u a l r e g i o s e l e c t i v i t i e s between the 1 , 2 - d i s u b s t i t u t e d and the 2 a , 5 c - d i s u b s t i t u t e d p r o d u c t s . The p r e s e n c e o f s p e c i f i c l a t t i c e i n t e r a c t i o n s was d e t e r m i n e d t o be t h e major f a c t o r r e s p o n s i b l e ; e l e c t r o n i c e f f e c t s were shown t o p l a y a much l e s s s i g n i f i c a n t r o l e . P h o t o c h e m i c a l i n v e s t i g a t i o n o f the b e n z o y l / m e t h y l e s t e r system was a l s o c o n d u c t e d i n polymer m a t r i x media t o show v a r i a t i o n i n p r o d u c t s e l e c t i v i t y . Ammonium and m e t a l i o n s a l t s o f b e n z o b a r r e l e n e - 2 , 3 - d i c a r b o x y l i c a c i d were p h o t o l y z e d i n s o l u t i o n and t h e c r y s t a l l i n e phase; t h e i r t r i p l e t p r o d u c t s e l e c t i v i t i e s were r e c o r d e d t o f u r t h e r s u p p o r t the dominance o f s p e c i f i c l a t t i c e i n t e r a c t i o n e f f e c t s o v e r e l e c t r o n i c e f f e c t s . D i s c o v e r y o f a r a r e " t r i - T T - m e t h a n e " rearrangement i n some d i b e n z o -b a r r e l e n e s prompted the d e s i g n and s y n t h e s i s o f d i m e t h y l 1 , 4 - d i h y d r o -1 , 4 , 5 , 8 - t e t r a m e t h y l - 1 , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l a t e . T h i s s u c c e s s f u l l y underwent the tri- T T-methane r e a r r a n g e m e n t i n b o t h s o l u t i o n and s o l i d s t a t e s . The n o v e l s e l e c t i v i t y was r a t i o n a l i z e d i n terms o f i n t r a m o l e c u l a r s t e r i c e f f e c t s r a t h e r t h a n on the b a s i s o f e l e c t r o n i c s t a b i l i z i n g e f f e c t s . Many b e n z o s e m i b u l l v a l e n e p h o t o p r o d u c t s were f o u n d t o undergo [1,3] s h i f t s from a s e c o n d a r y p h o t o l y s i s ; c o i n c i d e n t a l l y , t h e s e r e a r r a n g e m e n t s l e a d t o r e g i o i s o m e r i c b e n z o s e m i b u l l v a l e n e s . As a r e s u l t , many e x i s t i n u n u s u a l p h o t o s t a t i o n a r y s t a t e s . I t was f o u n d t h a t b e n z o s e m i b u l l v a l e n e s r e q u i r e a c a r b o n y l s u b s t i t u e n t a d j a c e n t t o t h e bond c l e a v e d i n o r d e r f o r the [1,3] s h i f t r e a c t i o n t o t a k e p l a c e . TABLE OF CONTENTS TITLE PAGE i ABSTRACT i i TABLE OF CONTENTS i v LIST OF FIGURES v i ACKNOWLEDGEMENT x l i i DEDICATION x i v INTRODUCTION 1 I . H i s t o r y 2 I I . The E x c i t e d S t a t e 3 I I I . The Di - T T-Methane Rearrangement 8 IV. The T o p o c h e m i c a l P r i n c i p l e 17 V. S o l i d S t a t e R e a c t i v i t y 19 V I . P h o t o c h e m i c a l [1,3] S i g m a t r o p i c S h i f t s 27 V I I . P h o t o c h e m i s t r y o f B e n z o b a r r e l e n e s 32 V I I I . O b j e c t o f R e s e a r c h 38 RESULTS AND DISCUSSION 44 PART I . P r e p a r a t i o n o f S t a r t i n g M a t e r i a l s 45 PART I I . C h a r a c t e r i z a t i o n o f D i s u b s t i t u t e d B e n z o s e m i b u l l v a l e n e P h o t o p r o d u c t s 57 PART I I I . P h o t o c h e m i s t r y o f S y m m e t r i c a l l y D i s u b s t i t u t e d B e n z o b a r r e l e n e s 73 A. P h o t o c h e m i s t r y o f D i m e t h y l 1,4-Dihydro-1,4-etheno-n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l a t e (29) 73 B. P h o t o c h e m i s t r y o f 1 , 4 - D i h y d r o - 1 , 4 - e t h e n o n a p h t h a l e n e -2 , 3 - d i c a r b o x y l i c A c i d (40) 82 C. P h o t o c h e m i s t r y o f 1, 4 - D i h y d r o - 1 , 4 - e t h e n o n a p h t h a l e n e -2 , 3 - d i c a r b o x y i c A n h y d r i d e (41) 94 D. P h o t o c h e m i s t r y o f 2 , 3 - D i b e n z o y l - 1 , 4 - d i h y d r o - 1 , 4 -e t h e n o n a p h t h a l e n e (42) 102 PART IV. P h o t o c h e m i s t r y o f U n s y m m e t r i c a l l y D i s u b s t i t u t e d B e n z o b a r r e l e n e s 109 A. P h o t o c h e m i s t r y o f M e t h y l 2 - B e n z o y l - l , 4 - d i h y d r o - l , 4 -e t h e n o n a p h t h a l e n e - 3 - c a r b o x y l a t e (43) 109 B. P h o t o c h e m i s t r y o f E t h y l 2 - B e n z o y l - 1 , 4 - d i h y d r o - 1 , 4 -e t h e n o n a p h t h a l e n e - 3 - c a r b o x y l a t e (44) 129 C. P h o t o c h e m i s t r y o f I s o p r o p y l 2 - B e n z o y l - l , 4 - d i h y d r o -l , 4- e t h e n o n a p h t h a l e n e - 3 - c a r b o x y l a t e (45) 135 PART V. P h o t o c h e m i s t r y o f B e n z o b a r r l e n e S a l t s (48-54) 147 PART V I . P h o t o c h e m i s t r y o f D i m e t h y l 1,4,5,8-Tetramethyl-1,4-d i h y d r o - 1 , 4 - e t h e n o n a p t h a l e n e - 2 , 3 - d i c a r b o x y l a t e ( 4 7 ) . 157 PART V I I . P h o t o c h e m i c a l [1,3] S h i f t s i n B e n z o s e m i b u l l v a l e n e s . . 171 EXPERIMENTAL 172 G e n e r a l P r o c e d u r e s 175 I . S y n t h e s i s o f S t a r t i n g M a t e r i a l s 179 I I . P h o t o c h e m i s t r y o f S u b s t r a t e s 205 A-D. P h o t o c h e m i s t r y o f S j m i m e t r i c a l l y D i s u b s t i t u e d B e n z o b a r r e l e n e s 205 E-G. P h o t o c h e m i s t r y o f U n s y m m e t r i c a l l y D i s u b s t i t u t e d B e n z o b a r r e l e n e s 222 H. 1 , 4 - D i h y r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l a t e S a l t s 245 I . D i m e t h y l 1 , 4 , 5 , 8 - T e t r a m e t h y l - 1 , 4 - d i h y d r o - 1 , 4 - e t h e n o -n a p h t h a l e n e -2,3- d i c a r b o x y l a t e 246 I I I . Quantum Y i e l d S t u d i e s 252 REFERENCES 255 LIST OF FIGURES INTRODUCTION F i g u r e 0.01 Energy Diagram f o r S e l e c t e d T r a n s i t i o n s 4 F i g u r e 0.02 Energy Diagram f o r G e n e r a l M o l e c u l a r P h o t o p h y s i c a l P r o c e s s e s 5 F i g u r e 0.03 l - B e n z o y l - 4 - ( a - n a p h t h y l ) - b i c y c l o [ 2 . 2 . 2 ] -o c t a n e (3) and a R i g i d Benzophenone-Naphthalene D o n o r - A c c e p t o r System (4) 7 F i g u r e 0.04 Di - 7 r-Methane Mechanism R e p r e s e n t e d i n 1,4-Pentadiene (6) 9 F i g u r e 0.05 Examples o f A c y c l i c Di-ir-Methane Systems 10 F i g u r e 0.06 Examples o f C y c l i c Di - 7 r -Methane Systems 11 F i g u r e 0.07 Examples o f I n i t i a l Bond F o r m a t i o n S e l e c t i v i t y i n the Di-w-Methane Rearrangement 14 F i g u r e 0.08 Examples o f Secondary Bond C l e a v a g e S e l e c t i v i t y i n the Di - 7 r-Methane Rearrangement 16 F i g u r e 0.09 P h o t o c h e m i s t r y o f Trans C i n n a m i c A c i d i n S o l u t i o n and C r y s t a l l i n e S t a t e s 18 F i g u r e 0.10 Cohen's Concept o f the R e a c t i o n C a v i t y 20 F i g u r e 0.11 Example o f a U n i m o l i c u l a r S o l i d S t a t e R e a c t i o n 22 F i g u r e 0.12 P h o t o d i m e r i z a t i o n o f B e n z y l i d e n e c y c l o -pentanone (17) 23 F i g u r e 0.13 E n a n t i o s e l e c t i v e T r a n s f o r m a t i o n o f D i b e n z o -b a r r e l e n e D i i s o p r o p y l E s t e r (18) 24 F i g u r e 0.14 L a t t i c e E nvironment o f D i b e n z o b a r r e l e n e D i i s o p r o p y l E s t e r 18 26 F i g u r e 0.15 Symmetry Diagrams D e s c r i b i n g t h e Woodward-Hoffmann Theory o f O r b i t a l O v e r l a p f o r [1,3] S h i f t s 28 F i g u r e 0.16 P h o t o c h e m i c a l [1,3] S h i f t s 29 F i g u r e 0.17 P h o t o c h e m i c a l [1,3] S h i f t s 30 F i g u r e 0.18 Some B e n z o s e m i b u l l v a l e n e s S t u d i e d f o r t h e [1,3] S i g m a t r o p i c S h i f t 31 F i g u r e 0.19 F e a s i b l e I n i t i a l B o n d i i n g S i t e s i n the P h o t o c h e m i s t r y o f D i b e n z o b a r r e l e n e s 32 F i g u r e 0.20 P o s s i b l e pathways i n the P h o t o c h e m i s t r y o f 2 , 3 - D i s u b s t i t u t e d M o n o b e n z o b a r r e l e n e s 34 F i g u r e 0.21 P h o t o t r a n s f o r m a t i o n s o f the U n s u b s t i t u t e d B e n z o b a r r e l e n e 35 F i g u r e 0.22 L i s t o f Some S u b s t i t u t e d B e n z o b a r r e l e n e s P r e v i o u s l y S t u d i e d 36 F i g u r e 0.23 P h o t o c h e m i s t r y o f l - C y a n o - 2 , 3 - b e n z o b i c y c l o -[ 4 . 2 . 0 ] o c t a - 2 , 4 , 7 - t r i e n e 38 F i g u r e 0.24 S y m m e t r i c a l D i s u b s t i t u t e d B e n z o b a r r e l e n e s S t u d i e d 39 F i g u r e 0.25 U n s y m m e t r i c a l B e n z o b a r r e l e n e s S t u d i e d 40 F i g u r e 0.26 S a l t s o f B e n z o b a r r e l e n e D i c a r b o x y l i c A c i d 41 F i g u r e 0.27 B r i d g e h e a d M e t h y l a t e d B a r r e l e n e D i m e t h y l E s t e r s 42 PART I . PREPARATION OF STARTING MATERIALS F i g u r e 1.01 S y n t h e s i s o f B e n z o b a r r e l e n e D i e s t e r 29 from a D i e l s - A l d e r R e a c t i o n 45 F i g u r e 1.02 D e r i v a t i o n o f B e n z o b a r r e l e n e D i m e t h y l E s t e r 29 46 F i g u r e 1.03 NMR S p e c t r a o f B e n z o b a r r e l e n e 29 and P a r t i a l l y D e u t e r a t e d B e n z o b a r r e l e n e 29-D 48 F i g u r e 1.04 P r e p a r a t i o n o f 2 , 3 - D i b e n z o y l - l , 4 - d i h y d r o -1,4-ethenonaphthalene (42) 49 F i g u r e 1.05 S p e c t r a o f S y m m e t r i c a l B e n z o b a r r e l e n e s 40 and 41 51 F i g u r e 1.06 a) P r e p a r a t i o n o f B e n z o y l E s t e r s 43, 44, and 45. b) M o n o d e u t e r a t e d B e n z o y l M e t h y l E s t e r (43-D) 53 F i g u r e 1.07 NMR S p e c t r a o f B e n z o y l E s t e r s 43 and 45 54 F i g u r e 1.08 S y n t h e s i s o f T e t r a m e t h y l B e n z o b a r r e l e n e D i m e t h y l E s t e r 47 56 PART I I . CHARACTERIZATION OF DISUBSTITUTED BENZOSEMIBULLVALENE PHOTOPRODUCTS F i g u r e 2.01 a) S t r u c t u r e o f P e n t a l e n e . b) S t r u c t u r e o f B e n z o s e m i b u l l v a l e n e o r 2a,2b,6b,6c-T e t r a h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e 58 F i g u r e 2.02 NMR S p e c t r a o f 2 a , 6 c - D i s u b s t i t u t e d B e n z o s e m i b u l l v a l e n e s 29a and 40a 59 F i g u r e 2.03 NMR S p e c t r a l E x p a n s i o n s o f 2 a , 6 c - D i s u b s t i t u t e d B e n z o s e m i b u l l v a l e n e s 29a and 40a 60 F i g u r e 2.04 NMR S p e c t r a l E x p a n s i o n s o f 1 , 6 c - D i s u b s t i t u t e d B e n z o s e m i b u l l v a l e n e s 29b and 43c 62 F i g u r e 2.05 NMR S p e c t r a l E x p a n s i o n s o f 1 , 2 - D i s u b s t i t u t e d Benzo-s e m i b u l l v a l e n e s 40b and a M i x t u r e o f 43d and 43e... 64 F i g u r e 2.06 M e t h y l 2 - B e n z o y l C i s - 2 - b u t e n e - 3 - c a r b o x y l a t e ( 6 5 ) . . . 65 F i g u r e 2.07 C o m p l e x a t i o n o f 1 , 2 - D i s u b s t i t u t e d B e n z o s e m i b u l l v a l e n e s t o E u ( h f c ) 3 66 F i g u r e 2.08 P l o t s o f Change i n C h e m i c a l S h i f t (Au) A g a i n s t the Mole % o f E u ( h f c ) 3 Added f o r Compounds 43d and 43e 67 F i g u r e 2.09 NMR Spectrum and E x p a n s i o n o f M e t h y l 6c-B e n z o y l - 2a,2b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] -p e n t a l e n e - 6 b - c a r b o x y l a t e ( 4 3 f ) 69 F i g u r e 2.10 X - r a y C r y s t a l S t r u c t u r e o f Compound 4 3 f 70 F i g u r e 2.11 a) NMR S p e c t r a l E x p a n s i o n o f M e t h y l 6 c - B e n z o y l -2 a , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e -2 b - c a r b o x y l a t e ( 4 3 g ) . b) D e c o u p l i n g a t 4.52 ppm 71 PART I I I PHOTOCHEMISTRY OF SYMMETRICALLY DISUBSTITUTED BENZOBARRELENES F i g u r e 3.01 P h o t o c h e m i s t r y o f Compound 29 R e p o r t e d by G r o v e n s t e i n e t a l . i n 1969 73 F i g u r e 3.02 M e c h a n i s t i c Study f o r B e n z o c y c l o o c t a t e t r a e n e 29c F o r m a t i o n , P e r f o r m e d by Bender and Brooks i n 1975 74 F i g u r e 3.03 Complete P h o t o c h e m i s t r y o f B e n z o b a r r e l e n e 29 76 F i g u r e 3.04 Mechanism o f B e n z o s e m i b u l l v a l e n e 29a and 29b F o r m a t i o n 77 F l g u r e 3.05 Mechanism o f B e n z o s e m i b u l l v a l e n e 29e F o r m a t i o n from B e n z o c y c l o o c t a t e t r a e n e 29c 79 F i g u r e 3.06 NMR Spectrum o f Compound 29c R e a c t i o n M i x t u r e Showing S i g n a l s o f C y c l o b u t e n e 29d 80 F i g u r e 3.07 P h o t o p r o d u c t s from 1,4-Dihydro-1,4-etheno-n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c A c i d (40) 82 F i g u r e 3.08 P r o t o n NMR s p e c t r a o f a) 41d i n DMSO-dg. b) 41d-D i n DMSO-dg 85 F i g u r e 3.09 Mechanisms o f B e n z o s e m i b u l l v a l e n e s 40a and 40b F o r m a t i o n 86 F i g u r e 3.10 a) R e a c t i o n M i x t u r e P r o t o n NMR S p e c t r a o f Benzophenone S e n s i t i z a t i o n o f 40-D 88 b) T a b l e o f Bond "a" and "b" L e n g t h s from X - r a y A n a l y s i s 90 F i g u r e 3.11 a) S o l i d S t a t e I n f r a r e d Spectrum o f D i a c i d 40. b) S i m p l e R e p r e s e n t a t i o n o f the R e a c t i o n C a v i t y o f D i a c i d 40 Showing the Hydrogen Bond Anch o r s 92 F i g u r e 3.12 Hydrogen B o n d i n g E f f e c t s on the P h o t o c h e m i s t r y o f 66 93 F i g u r e 3.13 P h o t o c h e m i s t r y o f B e n z o b a r r e l e n e A n h y d r i d e 41 95 F i g u r e 3.14 NMR Spectrum o f A n h y d r i d e 41 R e a c t i o n M i x t u r e from D i r e c t P h o t o l y s i s 96 F i g u r e 3.15 P l o t o f A n h y d r i d e P h o t o p r o d u c t C o m p o s i t i o n as a F u n c t i o n o f S t a r t i n g M a t e r i a l C o n v e r s i o n 97 F i g u r e 3.16 Pathways t o P h o t o p r o d u c t F o r m a t i o n from A n h y d r i d e 41 99 F i g u r e 3.17 P h o t o c h e m i s t r y o f D i b e n z o y l B e n z o b a r r e l e n e 42 103 F i g u r e 3.18 C h a r a c t e r i z a t i o n o f D i b e n z o y l B e n z o s e m i b u l l -v a l e n e 42c i n a M i x t u r e w i t h 42a, by NMR 104 F i g u r e 3.19 Mechanisms t o P h o t o p r o d u c t F o r m a t i o n f r o m D i b e n z o y l B e n z o b a r r e l e n e 42 105 F i g u r e 3.20 Graph o f Quantum Y i e l d ($) o f 42a v e r s u s S t a r t i n g M a t e r i a l 42 C o n v e r s i o n 106 PART IV. PHOTOCHEMISTRY OF UNSYMMETRICALLY DISUBSTITUTED BENZOBARRELENES F i g u r e 4.01 P o s s i b l e Di - 7 r-Methane Rearrangement Pathways f o r 2 - B e n z o y l 3 - E s t e r B e n z o b a r r e l e n e s 110 F i g u r e 4.02 P h o t o c h e m i s t r y o f B e n z o y l M e t h y l E s t e r B e n z o b a r r e l e n e 43 112 F i g u r e 4.03 NMR S p e c t r a l E x p a n s i o n s o f Compound 43 R e a c t i o n M i x t u r e from D i r e c t S o l u t i o n P h o t o l y s i s i n C D C I 3 . . . 113 F i g u r e 4.04 P l o t s o f Quantum Y i e l d v e r s u s C o n v e r s i o n f o r the F o r m a t i o n o f Compounds 43a and 43h 117 F i g u r e 4.05 NMR S p e c t r a l E x p a n s i o n s o f the C r y s t a l l i n e R e a c t i o n M i x t u r e o f B e n z o b a r r e l e n e 43 119 F i g u r e 4.06 Tri- T T-Methane Mechanism t o Form Benzo-s e m i b u l l v a l e n e 43f 121 F i g u r e 4.07 R a d i c a l S t a b i l i z a t i o n A pproach t o 1 , 2 - D i s u b s t i t u t e d B e n z o s e m i b u l l v a l e n e F o r m a t i o n i n the S o l i d S t a t e . . . 123 F i g u r e 4.08 X - r a y C r y s t a l S t r u c t u r e Diagram D i s p l a y i n g the C o n f o r m a t i o n o f B e n z o b a r r e l e n e 43 124 F i g u r e 4.09 M o t i o n s R e q u i r e d f o r B e n z o s e m i b u l l v a l e n e s 43d and 43h F o r m a t i o n 125 F i g u r e 4.10 P a c k i n g Diagram f o r Compound 43 127 F i g u r e 4.11 P h o t o c h e m i s t r y o f B e n z o b a r r e l e n e 44 129 F i g u r e 4.12 Graph o f Quantum Y i e l d v e r s u s C o n v e r s i o n f o r Compounds 44a and 44c i n Benzene 131 F i g u r e 4.13 C r y s t a l l i n e C o n f o r m a t i o n o f Compound 44 fro m X - r a y A n a l y s i s 133 F i g u r e 4.14 P a c k i n g Diagram o f B e n z o b a r r e l e n e 44 Showing I n t e r m o l e c u l a r C o n t a c t s 135 F i g u r e 4.15 P h o t o c h e m i s t r y o f B e n z o y l I s o p r o p y l E s t e r B e n z o b a r r e l e n e 45 136 F i g u r e 4.16 Graph o f Quantum Y i e l d v e r s u s C o n v e r s i o n f o r Compounds 45a and 45c i n Benzene 139 F i g u r e 4.17 C r y s t a l l i n e C o n f o r m a t i o n o f Compound 45 from X - r a y A n a l y s i s 140 F i g u r e 4.18 M o t i o n s R e q u i r e d i n R e l e v a n t Di-w-Methane Pathways, H o l d i n g the C a r b o n y l S u b s t i t u e n t s F i x e d 142 F i g u r e 4.19 P a c k i n g Diagrams o f B e n z o b a r r e l e n e 45 from X - r a y A n a l y s i s 144 F i g u r e 4.20 T a b l e Summarizing S o l u t i o n and S o l i d S t a t e R a t i o s i n th e P h o t o c h e m i s t r y o f Compounds 43, 44, and 45 145 PART V. PHOTOCHEMISTRY OF BENZOBARRELENE SALTS F i g u r e 5.01 P h o t o c h e m i s t r y o f B e n z o b a r r e l e n e S a l t s 149 F i g u r e 5.02 P h o t o p r o d u c t R a t i o s from S o l u t i o n Phase P h o t o c h e m i s t r y o f B e n z o b a r r e l e n e S a l t s 150 F i g u r e 5.03 NMR E x p a n s i o n s o f S a l t 48 B e f o r e and A f t e r R e a c i d i f i c a t i o n , i n C D C I 3 153 F i g u r e 5.04 P h o t o p r o d u c t R a t i o s from t h e S o l i d S t a t e S t u d y o f B e n z o b a r r e l e n e S a l t s 154 PART V I PHOTOCHEMISTRY OF DIMETHYL 1,4,5,8-TETRAMETHYL-1,4-ETHENO-NAPHTHALENE-2,3-DICARBOXYLATE (47) F i g u r e 6.01 P h o t o c h e m i s t r y o f Compound 47 158 F i g u r e 6.02 NMR S p e c t r a ( C D C I 3 ) and C r y s t a l l o g r a p h i c R e p r e s e n t a t i o n s o f B e n z o s e m i b u l l v a l e n e s 47a and B e n z o c y c l o o c t a t e t r a e n e 47b 160 F i g u r e 6.03 NMR S p e c t r a o f Compounds 47 and 47c i n C D C I 3 161 F i g u r e 6.04 P r o p o s e d S t r u c t u r e f o r 47d w i t h A n a l o g y 163 F i g u r e 6.05 P r o p o s e d Mechanisms t o P h o t o p r o d u c t F o r m a t i o n from B e n z o b a r r e l e n e 47 165 F i g u r e 6.06 Quantum Y i e l d Graphs f o r the F o r m a t i o n o f P h o t o p r o d u c t s 47a and 47b i n Benzene and i n a 1:1 M i x t u r e o f A c e t o n i t r i l e and Benzene 167 F i g u r e 6.07 C r y s t a l S t r u c t u r e o f B e n z o b a r r e l e n e 47 w i t h L i s t o f Bond Lengths and A n g l e s 168 F i g u r e 6.08 G e o m e t r i c Requirements f o r t h e F o r m a t i o n o f [2+2] C y c l o a d d i t i o n P r o d u c t s from 47 170 PART V I I . PHOTOCHEMICAL [1,3] SHIFTS IN BENZOSEMIBULLVALENES F i g u r e 7.01 Mechanism o f [1,3] S h i f t P h o t o c o n v e r s i o n 171 F i g u r e 7.02 B e n z o s e m i b u l l v a l e n e s S t u d i e d f o r Photo-s t a t i o n a r y S t a t e s 172 ACKNOWLEDGEMENTS I w i s h t o s i n c e r e l y thank my r e s e a r c h s u p e r v i s o r , P r o f e s s o r J o h n R. S c h e f f e r , f o r h i s s u p p o r t and g u i d a n c e t h r o u g h o u t t h e y e a r s ; h i s n o v e l i d e a s and c o n s t r u c t i v e s u g g e s t i o n s e n a b l e d me t o overcome b a r r i e r s t h a t I n e v e r t h o u g h t I c o u l d . H i s e n d l e s s p a t i e n c e , f r i e n d s h i p , and encouragement were i n v a l u a b l e i n m a i n t a i n i n g my e n t h u s i a s m i n t h e program. I w o u l d a l s o l i k e t o thank Dr. M i g u e l G a r c i a - G a r i b a y and Dr. J i a n x i n Chen f o r t h e i r a s s i s t a n c e i n the e a r l i e r p a r t o f t h e r e s e a r c h , a n s w e r i n g q u e s t i o n s and r e s p o n d i n g t o i d e a s no m a t t e r how r i d i c u l o u s t h e y may be. The warm s u r r o u n d i n g s p r o v i d e d by my c o - w o r k e r s made i t a d e l i g h t t o be i n g r a d u a t e s c h o o l . A l s o , I hope t o some day r e t u r n f a v o r s t o Anna-dora G u d m u n s d o t t i r and Mardy L e i b o v i t c h f o r p r o o f r e a d i n g t h i s t h e s i s . S p e c i a l t h a n k s t o Dr. James T r o t t e r , Dr. S t e v e R e t t i g , Dr. P h a n i Raj P o k k u l u r l , and Dr. Ray Jones f o r t h e i r d e t a i l e d c r y s t a l l o g r a p h i c work i n t h i s t h e s i s . I g r e a t l y a p p r e c i a t e the h e l p and k i n d a s s i s t a n c e from t h e s t a f f o f t h e NMR, mass s p e c t r o m e t r y , and e l e m e n t a l a n a l y s i s l a b o r a t o r i e s . F i n a n c i a l s u p p o r t from the U n i v e r s i t y o f B r i t i s h C o l umbia i s g r a t e f u l l y acknowledged. To my f a t h e r and mother INTRODUCTION I . H i s t o r y The s t u d y o f o r g a n i c p h o t o c h e m i s t r y began about two c e n t u r i e s ago-'- w i t h t h e use o f s u n l i g h t as t h e i r r a d i a t i o n s o u r c e . The p o p u l a r i t y o f t h i s t o p i c grew c o n s i d e r a b l y i n the e a r l y 1900s w i t h the development o f t h e mercury b r o a d band a r c lamp as an a r t i f i c i a l l i g h t s o u r c e . T h i s meant t h a t d u r a t i o n s o f p h o t o l y s i s were r e d u c e d t o mi n u t e s and h o u r s as opposed t o days and weeks. P r i o r t o t h i s , l e n g t h s o f p h o t o l y s i s depended n o t o n l y on t h e a b s o r p t i o n and r e a c t i v i t y o f t h e compound b u t on the weather and s e a s o n as w e l l . O r g a n i c p h o t o c h e m i s t r y i s s t i l l e x p a n d i n g i n many d i r e c t i o n s ; one i s i n the r e g i o n o f o r g a n i z e d media.^ The i n t e r a c t i o n o f p hotons w i t h o r g a n i c m o l e c u l e s t o cause a c h e m i c a l r e a c t i o n i n an a n i s o t r o p i c e n v i r o n m e n t i s a more d e f i n i t i v e term o f the s u b j e c t . Types o f o r g a n i z e d media u s e d i n p h o t o c h e m i s t r y a r e c r y s t a l s , p o l y m e r m a t r i c e s , z e o l i t e s , c y c l o d e x t r i n s , m i c e l l e s , and m o n o l a y e r s . The u n i q u e c h a r a c t e r i s t i c common t o t h e s e systems i s t h e i r a b i l i t y t o d r a m a t i c a l l y a l t e r , w i t h r e s p e c t t o the s o l u t i o n s t a t e , t h e s e l e c t i v i t y o f p h o t o p r o d u c t f o r m a t i o n from r e g i o i s o m e r s t o s t e r e o i s o m e r s as w e l l as from u n i m o l e c u l a r t o b i m o l e c u l a r p r o c e s s e s . I n t e r e s t i n g l y , t he f i r s t example o f a r e a c t i o n i n an o r g a n i z e d medium was n o t by p h o t o c h e m i c a l means, even though i t i s c u r r e n t l y the most w i d e l y u s e d t e c h n i q u e ; i n 1828, F r i e d r i c h Wohler s y n t h e s i z e d u r e a from ammonium c y a n a t e i n a t h e r m a l s o l i d s t a t e r e a c t i o n . - ^ R e s e a r c h i n o r g a n i z e d media d i d n o t bloom u n t i l about t h i r t y y e a r s ago w i t h the development o f n u c l e a r m a g n e t i c r e s o n a n c e s p e c t r o s c o p y , i n f r a r e d s p e c t r o s c o p y , and most i m p o r t a n t l y , X - r a y c r y s t a l l o g r a p h y . Modern X - r a y c r y s t a l l o g r a p h y a l l o w s c h e m i s t s t o overcome two b a r r i e r s i n s t u d i e s o f p h o t o c h e m i c a l s t r u c t u r e - r e a c t i v i t y r e l a t i o n s h i p s . The f i r s t i s i n the c o n f i r m a t i o n o f p h o t o p r o d u c t s t r u c t u r e s . The s econd and more v i t a l i s i t s use i n the d e t a i l e d v i s u a l i z a t i o n o f the m o l e c u l a r r e a c t i o n c a v i t y . Of t h e v a r i o u s o r g a n i z e d media r e p r e s e n t e d , t h e most e x t e n s i v e work has been done w i t h t h e use o f t h e c r y s t a l l i n e phase. M o l e c u l e s i n a c r y s t a l a r e o r g a n i z e d i n s u c h a manner t h a t t h e y a r e e v e n l y c l o s e - p a c k e d among t h e i r n e i g h b o r s . F o r most c a s e s , t h e s y s t e m a t i c r e p e a t i n g o f each u n i t c e l l a l l o w s each m o l e c u l e t o f e e l t h e same c o n s t r a i n i n g e n v i r o n m e n t as i t s n e i g h b o r s , t h u s t h e r e a c t i n g m o l e c u l e i n t h e l a t t i c e w o u l d f e e l t h e same e n v i r o n m e n t a l i n f l u e n c e so l o n g as the l a t t i c e remains i n t a c t . T h i s f i e l d o f s t u d y was opened i n the e a r l y t w e n t i e t h c e n t u r y by p i o n e e r i n g s c i e n t i s t s l i k e C i a m i c i a n , K o h l s h u t t e r , Stobbe, and S e n i e r . ^ A l t h o u g h the p r o g r e s s o f o r g a n i c s o l i d s t a t e p h o t o c h e m i s t r y has advanced c o n s i d e r a b l y s i n c e t h e n and many r e v i e w a r t i c l e s have r e c e n t l y been p u b l i s h e d , ^ s o l i d s t a t e p h o t o c h e m i s t r y i s s t i l l i n t h e " d i s c o v e r - a n d - e x p l a i n " s t a g e as opposed t o b e i n g used as a f u l l y p r e d i c t i v e s y n t h e t i c t o o l . T h i s i s due p r i m a r i l y t o the f a c t t h a t c r y s t a l p a c k i n g i s u n i q u e t o the m o l e c u l e and c a n n o t be p r e d i c t e d . I t i s t h o u g h t t h a t , u l t i m a t e l y , medium dependent p h o t o c h e m i s t r y w i l l have i t s main a p p l i c a t i o n s i n the a r e a s o f asymmetric s y n t h e s i s , m a t e r i a l s s c i e n c e , and computers. I I . The E x c i t e d S t a t e There a r e many a s p e c t s t o the m o l e c u l a r e x c i t e d s t a t e , and a c o m p l e t e summary woul d f i l l t h i s t e x t . The f o l l o w i n g w i l l b r i e f l y t o u c h on some o f the more r e l e v a n t a r e a s o f t h i s t o p i c . D e t a i l e d r e v i e w s can be f o u n d i n p u b l i c a t i o n s by T u r r o ^ and de Mayo^. E l e c t r o n s i n a m o l e c u l a r ground s t a t e e x i s t i n p a i r s a c c o r d i n g t o t h e i r e l e c t r o n s p i n ( S Q ) . Upon a b s o r p t i o n o f a pho t o n , u l t r a v i o l e t o r v i s i b l e r a d i a t i o n , an e l e c t r o n from the h i g h e s t o c c u p i e d m o l e c u l a r o r b i t a l (HOMO) i s t r a n s f e r r e d t o the l o w e s t u n o c c u p i e d m o l e c u l a r o r b i t a l (LUMO) ( F i g u r e 0.01). T h i s e x c i t a t i o n p u t s the m o l e c u l e i n the s i n g l e t e x c i t e d s t a t e (Sj^) ; s p i n - o r b i t c o u p l i n g a l l o w s an e l e c t r o n t o s p i n f l i p t o the u n p a i r e d t r i p l e t e x c i t e d s t a t e (T^^) . Most p h o t o c h e m i c a l r e a c t i o n s o c c u r from e i t h e r t he Sj^ o r Tj^ e x c i t e d s t a t e s . F i g u r e 0.01 Energy Diagram f o r S e l e c t e d T r a n s i t i o n s . The i n t e n t i o n o f the p h o t o c h e m i s t i s t o i r r a d i a t e w i t h low energy photons t o s e l e c t i v e l y e x c i t e a HOMO e l e c t r o n t o the LUMO. The use o f b r o a d band h i g h e nergy photons w o u l d e x c i t e the HOMO t o o t h e r u n o c c u p i e d o r b i t a l s ( S 2 , S 3 , ...) c a u s i n g a ca s c a d e o f d e c o m p o s i t i o n modes. C o n j u g a t e d m o l e c u l e s o r m o l e c u l e s t h a t p o s s e s s h e t e r o a t o m s w i t h non-bonded e l e c t r o n s have l o w e r HOMO / LUMO energy gaps and a r e t h e r e f o r e e a s i e r t o s e l e c t i v e l y e x c i t e . LEGEND A b s o r p t i o n I n t e r n a l c o n v e r s i o n SINGLETS S i n g l e t R e a c t i o n hv IC IC TRIPLETS ISC ISC / ZI / * \ T r i p l e t R e a c t i o n F l u o r e s c e n c e I n t e r s y s t e m C r o s s i n g Phosphorescence F i g u r e 0.02 Energy Diagram f o r G e n e r a l M o l e c u l a r P h o t o p h y s i c a l P r o c e s s e s . I n the S i s t a t e , m o l e c u l e s have s e v e r a l methods o f energy r e l e a s e . They can undergo: a) I n t e r s y s t e m c r o s s i n g - s p i n f l i p t o the l o w e r e n e r g y t r i p l e t s t a t e (T]^) ; t h i s i s f o r b i d d e n b u t o c c u r s t h r o u g h s p i n - o r b i t c o u p l i n g . b) F l u o r e s c e n c e - r e l e a s e energy i n the form o f l i g h t and r e t u r n back t o SQ; t h i s p r o c e s s i s a l l o w e d , and o c c u r s a t a r a t e o f 10^ - l O ' ^ ^ s e c - 1 . c) I n t e r n a l c o n v e r s i o n - r e l e a s e v i b r a t i o n a l e n e r g y i n the form o f h e a t and r e t u r n t o SQ", t h i s i s a l l o w e d as the s p i n s o f the two s t a t e s a r e the same. d) R e a c t i o n t o g i v e p h o t o p r o d u c t ( s ) . M o l e c u l e s i n t h e t r i p l e t (T]^) s t a t e a l s o have s e v e r a l modes o f e nergy r e l e a s e . They can undergo: a) P hosphorescence - r e l e a s e e nergy i n t h e form o f l i g h t and r e t u r n t o SQ; t h i s i s s p i n d i s a l l o w e d b u t o c c u r s t h r o u g h s p i n - o r b i t c o u p l i n g a t a r a t e o f lO"-*- - 10^ sec'-'-. b) I n t e r s y s t e m c r o s s i n g - r e l e a s e v i b r a t i o n a l e n e r g y i n t h e form o f h e a t and r e t u r n t o SQ; t h i s i s s p i n f o r b i d d e n b u t o c c u r s t h r o u g h s p i n - o r b i t c o u p l i n g . c) R e a c t i o n t o g i v e p h o t o p r o d u c t ( s ) . These commonly e n c o u n t e r e d p h o t o p h y s i c a l p r o c e s s e s a r e shown i n F i g u r e 0.02. Quantiim y i e l d ($) i s t h e measure o f p r o c e s s e f f i c i e n c y . Once a m o l e c u l e i s i n an e x c i t e d s t a t e , t h e p r o b a b i l i t y t h a t a s e l e c t e d decay r o u t e i s t a k e n i s d e f i n e d by t h e quantum y i e l d . The sum o f p o s s i b l e quantum y i e l d s f o r a d e f i n e d s t a t e must e q u a l one. F o r example, i f a m o l e c u l e i s i n t h e S i s t a t e o f F i g u r e 0.02, the ^ f l o u r e s c e n c e • ' ^ r e a c t i o n - ^ i n t e r s y s t e m c r o s s i n g ' " ^ i n t e r n a l c o n v e r s i o n ™ust add t o one. However, c h a i n - r e a c t i o n p r o c e s s e s ca n have v a l u e s g r e a t e r t h a n one. A n o t h e r phenomenon w o r t h m e n t i o n i n g i s w i t h t r i p l e t - t r i p l e t (T]^-T]^) energy t r a n s f e r ( t r i p l e t s e n s i t i z a t i o n ) . T h i s i s the t r a n s f e r o f e x c i t e d t r i p l e t e n ergy from one system t o a n o t h e r . The p r o c e s s u s u a l l y o c c u r s i n t e r m o l e c u l a r l y and a few c r i t e r i a must be s a t i s f i e d . F i r s t l y , t he e n e r g y l e v e l o f the e x c i t e d donor t r i p l e t must be h i g h e r t h a n the a c c e p t o r t r i p l e t . S e c o n d l y , the donor and a c c e p t o r must p h y s i c a l l y come t o g e t h e r f o r energy t o t r a n s f e r . The e f f i c i e n c y o f the second f a c t o r i s u l t i m a t e l y dependent on the c o l l i s i o n r a t e o f the donor t o the a c c e p t o r and the l i f e t i m e o f the e x c i t e d t r i p l e t donor. F i g u r e 0.03 l - B e n z o y l - 4 - ( a - n a p h t h y l ) - b i c y c l o [ 2 . 2 . 2 ] o c t a n e (3) and a R i g i d Benzophenone-Naphthalene D o n o r - A c c e p t o r System ( 4 ) . K e l l e r e t a l . ^ i n 1968 i n v e s t i g a t e d t h i s e nergy t r a n s f e r i n t r a m o l e c u l a r l y t o d e t e r m i n e the e f f e c t o f d i s t a n c e on the e f f i c i e n c y o f e n e r g y t r a n s f e r . The b e n z o y l - n a p h t h y l system ( 3 ) , ben z o p h e n o n e - n a p h t h y l system (4) ( F i g u r e 0.03), and o t h e r systems were s t u d i e d . Compound 3 was p h o t o l y z e d (A > 350 nm) such t h a t o n l y the b e n z o y l group was e x c i t e d (n-7r*) ; the chromophore t h e n t r a n s f e r r e d i t s energy t h r o u g h space t o t h e n a p h t h y l system where phosphorescence was o b s e r v e d . The e f f i c i e n c y o f energy t r a n s f e r r e d was d e t e r m i n e d t o be 100% w i t h a c a l c u l a t e d 7 Â s e p a r a t i o n between the donor and a c c e p t o r . The benzophenone group o f compound 4 was s e l e c t i v e l y e x c i t e d and the o b s e r v e d p h o s p h o r e s c e n c e o f t h e n a p h t h a l e n e m o i e t y was compared t o t h e d e c r e a s e i n p h o s p h o r e s c e n c e o f the benzophenone group. A 35% e f f i c i e n c y i n the t r i p l e t s e n s i t i z a t i o n o v e r a c a . 15 Â space was c o n c l u d e d . T h i s t h r o u g h d i s t a n t e x c i t e d s t a t e e nergy t r a n s f e r was a l s o r e c e n t l y s t u d i e d by G a r c i a - G a r i b a y i n a s o l i d s t a t e KBr medium and t h e s e n s i t i z a t i o n d i s t a n c e was d e t e r m i n e d t o be 12 Â.^ I I I . The Di - T T-Methane Rearrangement One o f the most t h o r o u g h l y s t u d i e d u n i m o l e c u l a r r e a r r a n g e m e n t s i n o r g a n i c p h o t o c h e m i s t r y i s the di - 7 r -me thane rearrangement.-*-^ W i t h o u t v a r i a t i o n , t h i s i s the s u b j e c t r e a c t i o n o f t h e t h e s i s . The r e a c t i o n was so named from the r e q u i r e d p r e s e n c e o f two w-bonds s e p a r a t e d by an s p ^ h y b r i d i z e d o r "methane" c a r b o n . A r e p r e s e n t a t i o n o f the r e a c t i o n i s shown w i t h one o f the s i m p l e s t o f di - 7 r-methane systems, 1,4-pentadiene (6),-'--'- i n F i g u r e 0.04. Howard Zimmerman-*-^ p r o p o s e d a s t e p w i s e mechanism w i t h an i n i t i a l bond f o r m a t i o n a c r o s s Q,^ ^'^^ ^° g^^^ c y c l o p r o p y l i n t e r m e d i a t e 6a. T h i s i s f o l l o w e d by e i t h e r bond c l e a v a g e o f a, g i v i n g back s t a r t i n g m a t e r i a l , o r c l e a v a g e o f b, p r o c e e d i n g t o 1 , 3 - b i r a d i c a l 6b. S i m p l e r i n g c l o s u r e o f b i r a d i c a l 6b g i v e s the v i n y l c y c l o p r o p a n e p r o d u c t 6c. More r e c e n t l y , Paquette-*--^ p r o p o s e d a v i a b l e a l t e r n a t i v e t o t h i s mechanism b a s e d on h i s s t u d y o f s u b s t i t u t e d b e n z o n o r b o r n a d i e n e s . He s u g g e s t e d a [1,2] s h i f t o f one u n s a t u r a t e d group f o l l o w e d by r i n g c l o s u r e t o g i v e the p r o d u c t . The o n l y d i f f e r e n c e between t h i s mechanism and Zimmerman's i s t h a t b i r a d i c a l 6b i s formed i n o n l y one s t e p i n s t e a d o f two, as shown by t h e t r a n s i t i o n s t a t e i n F i g u r e 0.04. A t t h i s p o i n t , i t can o n l y be s t a t e d t h a t b i r a d i c a l 6a i s s i m p l y a r e p r e s e n t a t i o n and may n o t be a t r u e i n t e r m e d i a t e ; a l s o i n some c a s e s , the s t e p s may merge t o a c o n c e r t e d p r o c e s s . F i g u r e 0.04 Di - 7 r-Methane Mechanisms R e p r e s e n t e d i n 1 , 4 - P e n t a d i e n e ( 6 ) . The m u l t i p l i c i t y o f t h i s r e a c t i o n i s f o u n d t o be dependent on the type o f di-ir-methane system. C y c l i c compounds undergo the di - T T-methane rearrangement e f f i c i e n t l y t h r o u g h t h e i r t r i p l e t e x c i t e d s t a t e and i n e f f i c i e n t l y t h r o u g h t h e i r s i n g l e t s t a t e s . On the o t h e r hand, a c y c l i c systems r e a r r a n g e v i a t h e i r s i n g l e t e x c i t e d s t a t e s more e f f i c i e n t l y t h a n t h e i r t r i p l e t s t a t e s . Compound 7 ( F i g u r e 0.05) i s a t y p i c a l example t o the r u l e ; d i r e c t p h o t o l y s i s r e s u l t s i n a di - 7 r-methane r e a r r a n g e m e n t t o v i n y l c y c l o p r o p a n e 7a. A l t e r n a t i v e l y , t r i p l e t s e n s i t i z a t i o n o f 7 g i v e s the t r a n s - i s o m e r i n a r e v e r s i b l e p h o t o s t a t i o n a r y s t a t e . •'•^  L i k e w i s e , d i e n e 8 r e a r r a n g e s upon d i r e c t p h o t o l y s i s b u t i s n o t r e a c t i v e from t r i p l e t s e n s i t i z a t i o n . •'-^  F i g u r e 0.05 Examples o f A c y c l i c Di-w-Methane Systems. B a r r e l e n e (9) ( F i g u r e 0.06) i s a c y c l i c di-?r-methane system t h a t r e a r r a n g e s t o b u l l v a l e n e (9a) upon t r i p l e t - s e n s i t i z e d p h o t o l y s i s . - ^ ^ However, when d i r e c t l y i r r a d i a t e d , b a r r e l e n e undergoes [2+2] c y c l o a d d i t i o n f o l l o w e d by a t h e r m a l r i n g o p e n i n g t o g i v e c y c l o o c t a t e t r a e n e ( 9 b ) . B e n z o n o r b o r n a d i e n e (10) a l s o undergoes the di-w-methane r e a r r a n g e m e n t upon t r i p l e t e x c i t a t i o n t o g i v e t h e t e t r a c y c l i c compound 10a.^'^ D i r e c t p h o t o l y s i s y i e l d s the s t r a i n e d [2+2] p r o d u c t ( 1 0 b ) , w h i c h r e a d i l y r e v e r t s back t o s t a r t i n g m a t e r i a l . ( r e f . 19) ( r e f . 20) F i g u r e 0.06 Examples o f C y c l i c Di-7r-Methane Systems. The m u l t i p l i c i t y d i f f e r e n c e i n r e a c t i v i t y was explained on the basis of the "free-rotor" e f f e c t . A c y c l i c systems do not rearrange through t h e i r t r i p l e t excited states because the double bond t w i s t i n g permitted i n non-rigid structures allows for f a s t t r i p l e t deactivation back to t h e i r ground states (Sg).^*^ The t r i p l e t states of r i g i d systems deactivate more slowly, thus f a c i l i t a t i n g e f f i c i e n t rearrangements. Although the r u l e applies i n most cases, there have been reported instances where the opposite was true, i . e . , c y c l i c compounds that rearrange through t h e i r s i n g l e t excited states and a c y c l i c compounds through t h e i r t r i p l e t states.^-^^ Mentioned e a r l i e r i n the mechanism to product formation was that the f i r s t intermediate can e i t h e r proceed to product or revert back to s t a r t i n g material. This r e v e r s i b i l i t y i s discussed i n a review by Zimmerman.^^^^ He concluded from a study of azo barrelenes that triplet-mediated di-x-methane rearrangements tend to not be r e v e r s i b l e . In s i t u a t i o n s where more than one di-T-methane system e x i s t s with the same chromophore, opportunity a r i s e s for s e l e c t i v i t y . I n i t i a l bonding can occur from d i f f e r e n t s i t e s g i v i n g d i f f e r e n t photoproducts. However, t h i s i n i t i a l bonding i s u s u a l l y d i r e c t e d to the most stable intermediate as the energy b a r r i e r to i t s formation would most l i k e l y be lower. In many cases, t h i s i s the r a t e - l i m i t i n g step of the rearrangement. Compound 11 (Figure 0.07) can rearrange from e i t h e r i n i t i a l benzo-benzo bonding or i n i t i a l benzo-vinyl bonding. However, the former pathway i n t e r f e r e s with the aromaticity of two phenyl rings as opposed to the d i s r u p t i o n of only one aromatic r i n g occurring i n benzo-vinyl bonding. Consistent with the model, photoproduct l i e i s the only product observed. This r e s u l t exemplifies the competition between pathways i n which the d i s r u p t i o n of aromaticity disfavors one but not the other. A l t e r n a t i v e l y , cyclohexadiene d e r i v a t i v e 12 (Figure 0.07) s e l e c t s the route through 12a over 12d on the r a t i o n a l e that the benzyl r a d i c a l on 12a can d e l o c a l i z e through the aromatic ring.^*^ Dibenzobarrelene ester 13 (Figure 0.07) has four i n i t i a l bonding p o s s i b i l i t i e s . Based on the r e s u l t s of compound 11, benzo-benzo i n i t i a l bonding may be excluded from the l i s t of choices. This reduces the number of i n i t i a l paths to two, with i n i t i a l benzo-vinyl bonding on the ester side or on the unsubstituted side. The path through 13a, with a r a d i c a l s t a b i l i z e d by the ester carbonyl, i s preferred, g i v i n g dibenzosemi-bullvalene 13c as the only product. Flgure 0.07 Examples of I n i t i a l Bond Formation S e l e c t i v i t y i n the Di-TT-Methane Rearrangement. S e l e c t i v i t y o f the re a r r a n g e m e n t i s n o t s o l e l y i n c o r p o r a t e d i n t he i n i t i a l s t e p . I n t e r e s t i n g l y , i n the se c o n d b i r a d i c a l f o r m a t i o n o f Zimmerman's mechanism, the b o n d - b r e a k i n g s t e p p r o v i d e s a n o t h e r o p p o r t u n i t y f o r s e l e c t i v i t y . The t h e o r y f o r p r e d i c t i n g the f a v o r e d r e a c t i o n pathway i s as f o l l o w s : the bond b r o k e n i s dependent on t h e r e l a t i v e e n e r g y l e v e l s o f t h e two b r a n c h - p o i n t p r o d u c t s . •'-^  From Zimmerman's n o t a t i o n , t h e more s t a b l e o f the two b i r a d i c a l s formed fr o m bond c l e a v a g e w i l l be p r e f e r r e d . The b a s i s o f t h i s r u l e stems from the t h e o r y t h a t r a d i c a l s t a b i l i t y i s dependent on e f f i c i e n c y o f T T - d e l o c a l i z a t i o n . The p r o p o s e d i n t e r m e d i a t e 14a ( F i g u r e 0.08) formed from the e x c i t a t i o n o f 14 c a n c l e a v e any one o f t h e t h r e e bonds a, b, o r c. I f bond c i s b r o k e n t h e n s t a r t i n g m a t e r i a l w i l l be r e g e n e r a t e d , b u t i f bond a o r b i s c l e a v e d , the r e a c t i o n w i l l p r o c e e d t o r e s p e c t i v e p r o d u c t s . I n 14a, owing t o d e l o c a l i z a t i o n t h r o u g h the p h e n y l r i n g , t h e b e n z y l r a d i c a l i s l e s s r e a c t i v e t h a n the c y c l o h e x y l r a d i c a l . As a r e s u l t , bond b i s c l e a v e d t o g i v e compound 14c as the o n l y p r o d u c t . ^ 3 xhe 1,4-diene 7 ( F i g u r e 0.05) i s s i m i l a r t o bond a o f t h e p r o p o s e d b i r a d i c a l 7c f a v o r e d f o r c l e a v a g e . C o n s e q u e n t l y , p h o t o p r o d u c t 7a i s the o n l y di - 7 r-methane product.-*-^ I n c l u d i n g the p r e v i o u s example, Zimmerman p u t f o r t h a t h o r o u g h i n v e s t i g a t i o n i n t o s u b s t i t u e n t e f f e c t s o f t h e bond c l e a v a g e s t e p i n the di - 7 r-methane r e a r r a n g e m e n t . C o m p o u n d s e r i e s 15 ( F i g u r e 0.08) r e p r e s e n t s o n l y some o f the many a c y c l i c s u b s t i t u t e d 1,4-dienes u s e d i n h i s s t u d y . A m e t h o x y l group i n the meta p o s i t i o n o f a d i s u b s t i t u t e d a r o m a t i c r i n g i s e l e c t r o n w i t h d r a w i n g , b u t i f i n v o l v e d i n resona n c e ( i . e . i n the o r t h o o r p a r a p o s i t i o n ) a c t s as an e l e c t r o n donor. The d o n a t i n g c h a r a c t e r i s t i c o f the p a r a s u b s t i t u t e d m e t h o x y l group o f p-15a re d u c e s the a b i l i t y o f the a r y l r a d i c a l t o d e l o c a l i z e . As a r e s u l t , p h o t o p r o d u c t p-15b from the h o m o l y t i c c l e a v a g e o f bond a o c c u r s w i t h about t h r e e t i m e s t h e e f f i c i e n c y as compound p-15c from t h e b r e a k i n g o f bond b. On the o t h e r hand, the i n d u c t i v e l y e l e c t r o n - w i t h d r a w i n g e f f e c t o f th e m e t h o x y l group i n the meta p o s i t i o n s l i g h t l y s t a b i l i z e s t h e a r o m a t i c r a d i c a l i n m-15a o v e r t h e u n s u b s t i t u t e d p h e n y l . Now the p h e n y l chromophore i s l e s s s t a b l e c a u s i n g a s l i g h t p r e f e r e n c e f o r the c l e a v a g e o f bond b o v e r bond a. R e s u l t s show a m-15c t o m-15b quantum y i e l d r a t i o o f 0.086 : 0.072.25 H e ( r e f . 23) c -c leave / \ Ar Ph Ph Ar ArPh Ph 15 15a 0) 0) a-cleavage b-cleavage product product PJ5 (Ar = p-MeOPh) m-15 (Ar = m-MeOPh) 0.075 0.072 0.022 0.086 15b 15c ( r e f . 25) F i g u r e 0.08 Examples o f Secondary Bond C l e a v a g e S e l e c t i v i t y i n t h e Dl-;r-Methane Rearrangement. IV. The T o p o c h e m i c a l P r i n c i p l e T h i s c o n c e p t o r i g i n a t e d i n the e a r l y days o f s o l i d s t a t e c h e m i s t r y when K o h l s h u t t e r ^ ^ p r o p o s e d i n 1918 t h a t " r e a c t i o n s i n s o l i d s a r e dependent on t h e c o n s t r a i n i n g t h r e e d i m e n s i o n a l e n v i r o n m e n t i n w h i c h t h e m o l e c u l e s e x i s t " . However, i t t o o k j u s t o v e r f o r t y y e a r s b e f o r e t h i s p o s t u l a t e was f o l l o w e d up. W i t h t h e i n t r o d u c t i o n o f modern X - r a y c r y s t a l l o g r a p h y , G e r h a r d Schmidt and c o - w o r k e r s r e i n v e s t i g a t e d many s o l i d s t a t e r e a c t i o n s u s i n g modern X - r a y c r y s t a l l o g r a p h i c t e c h n i q u e s . ^ ' ' The a c c u m u l a t e d e x p e r i m e n t a l r e s u l t s a l l o w e d them t o e s t a b l i s h some f u n d a m e n t a l p a r a m e t e r s f o r s o l i d s t a t e r e a c t i v i t y . Of the systems r e i n v e s t i g a t e d by Schmidt e t a l . , perhaps the most i n t e r e s t i n g i s t h e i r s t u d y o f t r a n s - c i n n a m i c acid.-'-^ U n s u b s t i t u t e d t r a n s - c i n n a m i c a c i d (5) i s t r i m o r p h i c ( F i g u r e 0.09) i n t h a t i t p o s s e s s e s t h r e e known c r y s t a l l i n e p a c k i n g arrangements ( a , /8, and 7 ) . P h o t o l y s i s o f t r a n s - c i n n a m i c a c i d i n s o l u t i o n r e s u l t s i n c i s / t r a n s i s o m e r i z a t i o n ; whereas p h o t o l y s i s o f c r y s t a l s o f t h e a-form g i v e s the [2+2] c y c l o a d d i t i o n p r o d u c t 5b. The d i s t a n c e between th e two d o u b l e bonds ( c e n t e r - t o - c e n t e r ) was e s t a b l i s h e d t o be i n t h e range o f 3.6-4.1 Â from a n a l y s i s o f the u n r e a c t e d c r y s t a l . The ;3-form p h o t o l y z e s t o g i v e a d duct 5c w i t h a r e a c t i o n d i s t a n c e r a n g i n g between 3.9-4.1 Â. The 7 - f o r m on the o t h e r hand, i s u n r e a c t i v e as the d e t e r m i n e d s e p a r a t i o n i s between 4.7-5.1 Â. W i t h o u t p r e j u d i c e t o the s o l i d s t a t e , a l m o s t a l l modern media-dependent c h e m i s t r y r e l i e s on t h i s p r i n c i p l e i n i t i a l l y p r o p o s e d by K o h l s h u t t e r and r e v i t a l i z e d by Schmidt. •'•^  As i t w i l l be seen, many o f the t h e o r i e s l a t e r d i s c u s s e d a r e b a s e d on the T o p o c h e m i c a l P r i n c i p l e . Ph \ — Ph "^COOH ^ S o l u t i o n ^ COOH Ph Ph HOOC^^^^^^ hv HOOC COOH ~ ^ ^ ( COOH \ a-form | Ph Ph 5fe ^ \ Ph P h ^ \ o o „ — 1 / ^ 1 \ p-form f COOH COOH 5c Ph HOOC ' \ hv COOH • NO REACTION \ T-form d > 4.7 A F i g u r e 0.09 P h o t o c h e m i s t r y o f Trans Cinnamic A c i d i n S o l u t i o n and C r y s t a l l i n e S t a t e s . V. S o l i d State R e a c t i v i t y Throughout t h e h i s t o r y o f c h e m i s t r y , s c i e n t i s t s have r e c o g n i z e d t h e o r g a n i c c r y s t a l l i n e phase as a means o f r e a c t i o n work-up. Compounds c a n be p u r i f i e d by r e c r y s t a l l i z a t i o n and a r e o f t e n s t o r e d as c r y s t a l s , an e a s i l y h a n d l e d , i n e r t form. I n a p a r a l l e l manner, t h e p r o p e r t i e s o f c r y s t a l s a r e u s e d i n compound i d e n t i f i c a t i o n t h r o u g h t h e i r d i f f e r e n t a p pearances and m e l t i n g p o i n t s , and known compounds may be compared t o t h e i r l i t e r a t u r e v a l u e s f o r s t r u c t u r a l c o n f i r m a t i o n . Now i t i s becoming w e l l a c c e p t e d t h a t t h e c r y s t a l l i n e phase c a n a l s o p l a y an a c t i v e r o l e i n c h e m i c a l r e a c t i o n s . W i t h the a d v e n t o f modern X - r a y c r y s t a l l o g r a p h y , 29 h i g h r e s o l u t i o n s o l i d s t a t e •'-•^C NMR,-^ ^ d i f f e r e n t i a l s c a n n i n g c a l o r i m e t r y , a n d o t h e r t e c h n i q u e s , the probe i n t o s o l i d s t a t e c h e m i s t r y has f a c i l i t a t e d many new f i n d i n g s . The e x t e r n a l c r y s t a l appearance i s g o v e r n e d i n p a r t by t h e i n t e r n a l p a c k i n g arrangement. M o l e c u l e s i n a c r y s t a l a r e s y s t e m a t i c a l l y s t a c k e d i n s u c h a manner t h a t e v e r y m o l e c u l e f e e l s the same i n t e r m o l e c u l a r e n v i r o n m e n t , b u t e x c e p t i o n s do e x i s t . The r e p e a t i n g u n i t o f m o l e c u l e s ( u n i t c e l l ) i s c l a s s i f i e d a c c o r d i n g t o i t s symmetry, and t h i s c l a s s i f i c a t i o n i s c a l l e d the "space group". There a r e 230 p o s s i b l e space groups o f w h i c h 65 a r e c h i r a l . Each r e p e a t i n g u n i t i n a c h i r a l space group f e e l s the same u n s y m m e t r i c a l e n v i r o n m e n t as opposed t o a s y m m e t r i c a l e n v i r o n m e n t . As a r e s u l t , c r y s t a l l i n e c h i r a l m o l e c u l e s must adopt c h i r a l space groups due t o t h e i r i n h e r e n t l a c k o f symmetry, and a c h i r a l m o l e c u l e s u s u a l l y do n o t b u t may a l s o have c h i r a l space groups. A m o l e c u l e w i t h i n a c r y s t a l l a t t i c e p r e v e n t s n e i g h b o r i n g m o l e c u l e s from i n f r i n g i n g on i t by b a s i c s t e r i c i n t e r a c t i o n s . T h i s i s where the atoms o f a d j a c e n t m o l e c u l e s f e e l each o t h e r ' s e l e c t r o s t a t i c c h a r g e s and r e p e l . Through t h e s e i n t e r a c t i o n s the m o l e c u l e has d e s i g n e d i t s own volume o f s p a c e , molded t o one o f i t s c o n f o r m a t i o n a l e n ergy minima. W i t h i n t h i s s p a c e , s o l i d s t a t e p h o t o c h e m i c a l r e a c t i o n s c a n o c c u r . Cohen termed t h i s space the " r e a c t i o n c a v i t y " . F i g u r e 0.10 Cohen's Concept o f t h e R e a c t i o n C a v i t y . I n 1975, Cohen-^2 s u g g e s t e d t h a t as a m o l e c u l e r e a c t s i n a c r y s t a l , the p h y s i c a l geometry o f the s p e c i e s changes w h i l e p r o c e e d i n g from r e a c t a n t t h r o u g h t r a n s i t i o n s t a t e ( s ) t o p r o d u c t . T h i s i s r e p r e s e n t e d by the s t r u c t u r e s o f F i g u r e 0.10. Those r e a c t i o n s w i t h m i n i m a l changes i n geometry w i l l p r o c e e d w i t h o u t much i n t e r f e r e n c e from the c a v i t y w a l l s ( p a t h a ) . However, r e a c t i o n s w i t h t r a n s i t i o n s t a t e g e o m e t r i e s i n c o m p a t i b l e w i t h the r e a c t i o n c a v i t y w i l l be s l o w e d o r even f o r b i d d e n t o o c c u r ( p a t h b ) . T h i s i n t u r n w i l l g i v e r i s e t o r e a c t i o n s e l e c t i v i t y d i f f e r i n g f rom the s o l u t i o n phase. The u n d e r l y i n g f a c t o r s r e s p o n s i b l e f o r c r y s t a l l i n e s t a t e s e l e c t i v i t y d i f f e r from r e a c t a n t t o r e a c t a n t d e p e n d i n g on s p e c i f i c i n t e r a c t i o n s o f t h e s u b s t r a t e w i t h the l a t t i c e . These i n t e r a c t i o n s may e i t h e r be d i r e c t , where a s p e c i f i c l a t t i c e group i n h i b i t s t h e movement o f a s u b s t r a t e appendage r e q u i r e d f o r r e a c t i o n , o r i n d i r e c t l y , where the l a t t i c e g e o m e t r i c a l l y p o s i t i o n s an atom o r group o f atoms p r o p e r l y f o r r e a c t i o n by l o c k i n g the m o l e c u l e i n t h e r e q u i r e d c o n f o r m a t i o n . C o n s e q u e n t l y , i n t h i s a p p roach t o u n d e r s t a n d i n g s o l i d s t a t e s e l e c t i v i t y , t h e r e a c t a n t X - r a y c r y s t a l s t r u c t u r e d a t a i s examined f o r the p r e s e n c e o r absence o f s p e c i f i c s t e r i c i n t e r a c t i o n s t o e x p l a i n any enhanced o r r e t a r d e d p r o d u c t f o r m a t i o n . T h i s " s t r u c t u r e -r e a c t i v i t y c o r r e l a t i o n " i s t h e most commonly u s e d method o f a n a l y s i s , employed by l e a d i n g s o l i d s t a t e p h o t o c h e m i s t s such as Lahav,-^-^ McBride,-^^ S che f f e r , 3 5 and Ramamur t h y . ^ ^ I n a s t u d y by S c h e f f e r e t a l . , - ^ ^ i t was f o u n d t h a t ; S , 7 - u n s a t u r a t e d k e t o n e 16 p h o t o l y z e s i n benzene t o g i v e t e t r a c y c l i c d i k e t o n e 16c. A l t e r n a t i v e l y , p h o t o l y s i s i n t h e c r y s t a l l i n e phase g i v e s t h e t r i c y c l i c i s o m e r 16e as the o n l y p r o d u c t . Compound 16c was p o s t u l a t e d t o come from a t h r e e - s t e p p r o c e s s , i n i t i a l C 4 t o C 5 b o n d i n g t o g i v e 16a. The Cg r a d i c a l on 16a, owing t o i t s c o n f o r m a t i o n a l a l i g n m e n t w i t h t h e C 2 - C 3 d o u b l e bond, b r i d g e s w i t h C 2 t o g i v e 16b, and the r e a r r a n g e m e n t i s c o m p l e t e d w i t h a 1 , 2 - s h i f t o f t o C 3 y i e l d i n g the s o l u t i o n p r o d u c t ( 1 6 c ) . A l t e r n a t i v e l y , t h e s o l i d s t a t e p r o d u c t 16e i s d e r i v e d from i n i t i a l C 3 t o C 5 b o n d i n g , f o l l o w e d by the a b s t r a c t i o n o f t h e h y d r o g e n atom on Cy by the C2 r a d i c a l . I t was r e a s o n e d t h a t 4 , 5 - b o n d i n g i s f a v o r e d o v e r 3 , 5 - b o n d i n g i n s o l u t i o n because the r e a c t a n t i s an oxa-di - 7 r -me thane system; "^ ^ s u c h systems e a s i l y undergo i n i t i a l b i r a d i c a l f o r m a t i o n t o p r o c e e d t o 16c. However, the l a r g e m o t i o n needed t o form the C 2 - C 5 bond f o r b i d s c o n t i n u a t i o n o f t h i s r e a c t i o n i n the c r y s t a l l i n e phase. The i n i t i a l 3,5-bonding r o u t e has m i n i m a l t o p o c h e m i c a l r e q u i r e m e n t s and i s t h e r e f o r e a l l o w e d . Me ( r e f . 37) I Me F i g u r e 0.11 Example o f a U n i m o l e c u l a r S o l i d S t a t e R e a c t i o n . I t i s n o t uncommon f o r a compound t h a t i s r e a c t i v e p h o t o c h e m i c a l l y i n s o l u t i o n t o be r e a c t i v e i n the s o l i d phase as w e l l . U s u a l l y s o l i d s t a t e p h o t o p r o d u c t c o n v e r s i o n i s l i m i t e d . As a m o l e c u l e i s c o n v e r t e d to p r o d u c t i n the l a t t i c e , many r e a c t e d s p e c i e s r e t a i n o r have an enhanced a b i l i t y t o absorb l i g h t , t h e n the b u l k w i l l be u n r e a c t e d due t o poor photon p e n e t r a t i o n t h r o u g h the c r y s t a l . A n o t h e r common d e t e r r e n t t o b u l k r e a c t i v i t y i s t h a t once a s u b s t r a t e i s r e a c t e d , t h i s new m o l e c u l e has a t h r e e d i m e n s i o n a l geometry d i f f e r e n t from the r e a c t a n t and, as a r e s u l t , g e n e r a t e s a d e f e c t i n the l a t t i c e . T h i s d e f e c t promotes the s c a t t e r i n g o f l i g h t b ack t o the s u r f a c e and i n h i b i t s the b u l k o f the c r y s t a l from r e a c t i n g . I n most c a s e s , p r o l o n g e d p h o t o l y s e s r e s u l t i n the c r y s t a l f o r m i n g c r a c k s , becoming c l o u d y , and even m e l t i n g on the s u r f a c e . T h i s p r o b l e m i s p a r t i a l l y a l l e v i a t e d by i r r a d i a t i o n i n the t a i l o f the a b s o r p t i o n band t o f a c i l i t a t e deeper p e n e t r a t i o n o f l i g h t i n t o t he c r y s t a l . T h i s b u l k v e r s u s s u r f a c e r e a c t i v i t y has been d i s c u s s e d i n a r e c e n t s t u d y by S c h e f f e r and co-workers.-^^ Upon i r r a d i a t i o n , some c r y s t a l s c a n c o n v e r t c o m p l e t e l y t o a s i n g l e p h o t o p r o d u c t w i t h o u t l o s s o f t h e i r c r y s t a l l i n e appearance. T h i s phenomenon i s known as a " t o p o t a c t i c " o r s i n g l e c r y s t a l - t o - s i n g l e c r y s t a l r e a c t i o n . ( r e f . 41) 11 lia F i g u r e 0.12 P h o t o d i m e r i z a t i o n o f B e n z y l i d e n e c y c l o p e n t a n o n e . Of the known b i m o l e c u l a r p h o t o c h e m i c a l p r o c e s s e s , by f a r the most commonly o b s e r v e d i s the i n t e r m o l e c u l a r [2+2] c y c l o a d d i t i o n r e a c t i o n . I n 1980, Jones and Thomas e t al.'^-'- s t u d i e d t h e s o l i d s t a t e p h o t o c h e m i c a l b e h a v i o r o f b e n z y l i d e n e c y c l o p e n t a n o n e 17. P h o t o l y s i s o f c r y s t a l l i n e compound 17 r e s u l t s i n the co m p l e t e c o n v e r s i o n o f s t a r t i n g m a t e r i a l t o the [2+2] adduct 17a w i t h the r e t e n t i o n o f m o l e c u l a r c r y s t a l l i n i t y . C r y s t a l l o g r a p h i c a n a l y s e s o f compounds 17 and 17a r e v e a l a r e m a r k a b l e s i m i l a r i t y i n c r y s t a l p a c k i n g and c e l l d i m e n s i o n s a l l o w i n g f o r f a v o r a b l e i n t e r c o n v e r s i o n o f pentanone d e r i v a t i v e 17 t o p r o d u c t 17a. Asymmetric s y n t h e s i s i s a n o t h e r a s p e c t t o the s t u d y o f the o r g a n i c s o l i d s t a t e . As mentioned e a r l i e r , 65 o f the p o s s i b l e 230 c r y s t a l space groups p o s s e s s c h i r a l i t y . C h i r a l c r y s t a l l a t t i c e s e x e r t an a s y m m e t r i c a l environment on the m o l e c u l e . F o r p h o t o r e a c t i o n s w h i c h g e n e r a t e a new c h i r a l c e n t e r ( s ) , t h i s temporary l a t t i c e c h i r a l i t y may i n f l u e n c e a s o l i d s t a t e r e a c t i o n i n such a manner t h a t the p r o d u c t a c q u i r e s t h i s c h i r a l i t y i n e n a n t i o m e r i c e x c e s s . F i g u r e 0.13 E n a n t i o s e l e c t i v e P h o t o t r a n s f o r m a t i o n o f D i b e n z o b a r r e l e n e D l i s o p r o p y l E s t e r 18. M o l e c u l a r c h i r a l i t y i s n o t mandatory f o r c r y s t a l l i z a t i o n i n t o a c h i r a l space group. S c h e f f e r , T r o t t e r , and c o - w o r k e r s ^ ^ n o t i c e d t h a t d i b e n z o b a r r e l e n e 18 has two c r y s t a l l i n e m o r p h o l o g i e s . R e c r y s t a l l i z a t i o n f r o m e t h a n o l g i v e s p r i s m s w i t h t h e a c h i r a l space group Pcba. However, i f t h e compound i s c o o l e d from t h e m e l t , c r y s t a l s h a v i n g t h e c h i r a l space group P2]^2]^2]^ appear. P h o t o l y s i s o f r e a c t a n t 18 i n s o l u t i o n o r i n a s i n g l e Pcba c r y s t a l g i v e s a r a c e m i c m i x t u r e o f d i b e n z o s e m i b u l l v a l e n e 18a t h r o u g h t h e di - 7 r-methane r e a r r a n g e m e n t . The i n t e r e s t i n g a s p e c t o f t h i s s t u d y i s w i t h t h e s i n g l e c r y s t a l p h o t o l y s i s o f the c h i r a l P2]^2]^2]^ morphology; t h i s l e a d s t o t h e f o r m a t i o n o f 18a w i t h 100% e n a n t i o m e r i c e x c e s s . The d i r e c t i o n o f o p t i c a l r o t a t i o n v a r i e s from r u n t o r u n d e p e n d i n g on t h e handedness o f t h e c h i r a l c r y s t a l chosen. The r e a c t i o n pathways d i f f e r i n the l o c a t i o n o f i n i t i a l b o n d i n g . I n F i g u r e 0.14, i f i n i t i a l b o n d i n g forms on the M s i d e from the a n t e r i o r benzo group t o the v i n y l group o f the m o l e c u l e ( d o t t e d l i n e ) , one e n a n t i o m e r i s o b t a i n e d ; and, i f the b o n d i n g i s on the P s i d e from the a n t e r i o r benzo t o t h e v i n y l , the o t h e r e n a n t i o m e r i s o b t a i n e d . C r y s t a l l o g r a p h i c a n a l y s i s ( F i g u r e 0.14) shows the s t e r i c c r o w d i n g o f t h e l a t t i c e on t h e l a t t e r b o n d i n g r o u t e (P s i d e ) w h i l e l e a v i n g t h e M s i d e b o n d i n g ( d o t t e d l i n e ) r e l a t i v e l y open. F i g u r e 0.14 L a t t i c e E nvironment o f D i b e n z o b a r r e l e n e D i i s o p r o p y l E s t e r 18. Through the advancement o f computer hardware and s o f t w a r e , s o p h i s t i c a t e d c a l c u l a t i o n s a r e now p o s s i b l e t o a s s i s t i n the u n d e r s t a n d i n g o f m o l e c u l a r p r o c e s s e s . A l l i n g e r ' s d e s i g n o f the M o l e c u l a r M e c h a n i c s I I (MM2) c a l c u l a t i o n s a l l o w e d c h e m i s t s t o l o c a t e minimum ene r g y c o n f o r m a t i o n s i n m o l e c u l e s and i n t e r m e d i a t e s . ^ - ^ From t h i s and o t h e r programs t h a t stem from t h i s d e s i g n , m o l e c u l a r c a l c u l a t i o n s have opened a new passage t o the f o r m u l a t i o n o f t h e o r i e s i n s o l i d s t a t e r e a c t i v i t y . I n a r e c e n t p u b l i c a t i o n , Zimmerman and Zuraw'^'^ e s t a b l i s h e d t h r e e p a r a m e t e r s u s i n g the MacroModel program*^^ t o p r e d i c t c r y s t a l l i n e phase r e a c t i o n s e l e c t i v i t y . Concerned were the s t a r t i n g m a t e r i a l geometry, l a t t i c e d i m e n s i o n s , and the geometry o f the i n t e r m e d i a t e s o r p r o d u c t s d i r e c t l y f o l l o w i n g the b r a n c h p o i n t i n the r e a c t i o n pathway (termed the b r a n c h - p o i n t s p e c i e s ) . Change i n m o t i o n (AM) was the f i r s t p a r a m e ter. T h i s was c a l c u l a t e d by s u p e r i m p o s i n g the b r a n c h - p o i n t i n t e r m e d i a t e o v e r the s t a r t i n g m a t e r i a l and a d d i n g a l l the non-hydrogen a t o m i c d i s p l a c e m e n t d i s t a n c e s . I n t u i t i v e l y , the l a r g e r the d i s p l a c e m e n t sum, the l e s s e f f i c i e n t t h e s o l i d s t a t e r e a c t i o n . Volume r e q u i r e m e n t (AV) was the n e x t p a r a m e t e r . The b r a n c h - p o i n t s p e c i e s i s s u p e r i m p o s e d o v e r t h e r e a c t a n t i n a c a l c u l a t e d b e s t f i t geometry and the n o n - o v e r l a p p i n g volume o f the b r a n c h - p o i n t s p e c i e s was r e p o r t e d as a p e r c e n t a g e o f t h e r e a c t a n t volume. T h e r e f o r e , s m a l l AV v a l u e s s h o u l d f a v o r s o l i d s t a t e r e a c t i v i t y . The t h i r d p a r a m e t e r was t h e l a t t i c e i n t e r f e r e n c e ( A S ) ; t h i s was d e t e r m i n e d by s u p e r i m p o s i n g the b r a n c h - p o i n t s p e c i e s o v e r the r e a c t a n t m o l e c u l e i n t h e l a t t i c e and removing the r e a c t a n t . The amount o f o v e r l a p w i t h the c r y s t a l l a t t i c e was t h e n c a l c u l a t e d and r e c o r d e d as a p e r c e n t a g e o f the volume o f l a t t i c e segment used. The volume o f l a t t i c e segment chosen must be l a r g e enough t o c o n t a i n the e n t i r e s u p e r i m p o s e d s p e c i e s . A g a i n , s m a l l AS v a l u e s f a v o u r s o l i d s t a t e r e a c t i v i t y . X - r a y c r y s t a l s t r u c t u r e c o o r d i n a t e s were u s e d wherever p o s s i b l e . These c a l c u l a t i o n s were p e r f o r m e d on a s e r i e s o f u n s y m m e t r i c a l di - 7 r-methane systems t o g i v e e n c o u r a g i n g r e s u l t s ; however, more examples a r e needed t o b e t t e r e s t a b l i s h the g e n e r a l i t y o f t h i s a p p r o a c h . V I . P h o t o c h e m i c a l [1,3] S i g m a t r o p i c S h i f t s S i g m a t r o p i c r e a r r a n g e m e n t s a r e r e a c t i o n s where a sigma bond i s c l e a v e d and r e f o r m e d e l s e w h e r e a l o n g a c o n j u g a t e d c a r b o n c h a i n . These r e a c t i o n s c a n be i n i t i a t e d e i t h e r t h e r m a l l y o r p h o t o c h e m i c a l l y . The movement o f the bond i s d e s c r i b e d i n a [x,y] n o t a t i o n ; the two c h a i n s a r e numbered s t a r t i n g from the atoms a d j a c e n t t o the b r o k e n bond. S y s t e m a t i c a l l y x and y denote the p o s i t i o n s a l o n g the c h a i n s where the new bond i s formed. Such t h e r m a l and p h o t o c h e m i c a l r e a c t i o n s a r e t h o u g h t t o be c o n c e r t e d p e r i c y c l i c p r o c e s s e s whereby the bonds form and b r e a k s i m u l t a n e o u s l y w i t h no d e t e c t a b l e i n t e r m e d i a t e s . A s e t o f o r b i t a l symmetry r u l e s was p r o p o s e d by Woodward and Hoffmann^^ f o r p r e d i c t i n g w h i c h s i g m a t r o p i c r e a r r a n g e m e n t s a r e f a v o u r e d and w h i c h d i s f a v o r e d . T r a n s i t i o n s o c c u r from t h e h i g h e s t o c c u p i e d m o l e c u l a r o r b i t a l (HOMO). I n t h e r m a l r e a c t i o n s , the [1,3] s h i f t i s f o r b i d d e n t o o c c u r a l o n g the same s u r f a c e as the symmetry o f the i n t e r a c t i n g l o b e s must match. However, t h r o u g h i n v e r s i o n o f c o n f i g u r a t i o n , t h i s symmetry r e q u i r e m e n t i s s a t i s f i e d . P h o t o c h e m i c a l a c t i v a t i o n i n v o l v e s a s l i g h t l y d i f f e r e n t s c e n a r i o ; a e l e c t r o n i s promoted t o the n e x t o r b i t a l a l t e r i n g the symmetry o f the HOMO ( F i g u r e 0.15). Now o r b i t a l symmetry a l l o w s [1.3] s i g m a t r o p i c s h i f t s t o p r o c e e d w i t h r e t e n t i o n o f c o n f i g u r a t i o n . I n l i g h t o f these p r e d i c t i o n s , r e t e n t i o n o f c o n f i g u r a t i o n s h o u l d a l s o o c c u r w i t h [1,7] s h i f t s p h o t o c h e r a i c a l l y and [1,5] s h i f t s t h e r m a l l y . HOMO of HOMO of ground state excited state F i g u r e 0.15 Symmetry Diagrams D e s c r i b i n g the Woodward-Hoffmann Theory o f O r b i t a l O v e r l a p f o r [1,3] S h i f t s . As m e n t i o n e d e a r l i e r , s i g m a t r o p i c s h i f t s a r e f r e q u e n t l y a n a l y z e d as c o n c e r t e d p e r i c y c l i c r e a c t i o n s ; however, w i t h p h o t o c h e m i c a l [1,3] s h i f t s t h e r e have been many r e p o r t s o f b i r a d i c a l p r o c e s s e s . A t y p i c a l s e t o f examples has been f o u n d w i t h / 3 , 7 - u n s a t u r a t e d c a r b o n y l compounds. I r r a d i a t i o n o f compound 20 ( F i g u r e 0.16) l e a d s t o b i r a d i c a l 20a w h i c h t h e n p r o c e e d s t o g i v e t h e [1,3] s h i f t p r o d u c t 20b i n c o m p e t i t i o n w i t h a d i s p r o p o r t i o n a t i o n r e a c t i o n . ' ^ ^ D i r e c t p h o t o l y s i s o f compound 21 r e s u l t s i n a - c l e a v a g e t o g i v e [1,3] s h i f t p r o d u c t 21a and r a d i c a l c o m b i n a t i o n p r o d u c t s , 21b and 2 1 c . T h e s e / 9 , 7 - u n s a t u r a t e d c a r b o n y l s r e a r r a n g e e i t h e r t h r o u g h t h e S;j^(n-7r*) o r T 2 ( n - 7 r * ) e x c i t e d s t a t e s . ( r e f . 48) ( r e f . 50) 21b F i g u r e 0.16 P h o t o c h e m i c a l 11,3] S h i f t s . The p h o t o c h e m i c a l m u l t i p l i c i t y o f t h e s e r e a c t i o n s i s p r e d o m i n a n t l y s i n g l e t , b u t t r i p l e t s t a t e s a r e n o t uncommon. T h i s i s e x e m p l i f i e d i n t h e t r i p l e t s e n s i t i z a t i o n o f b i c y c l i c k e t o n e 22 ( F i g u r e 0.17) t o g i v e [1,3] s h i f t p r o d u c t 22d t h r o u g h b i r a d i c a l 2 2 c . I n c o n t r a s t , d i r e c t p h o t o l y s i s o f compound 22 l e a d s t o isom e r 22b r e v e r s i b l y t h r o u g h k e t e n e 22a. T h i s k e t e n e 22a i s s t a b l e below -180 °C and g i v e s an i n f r a r e d band a t 2118 cm'^, c h a r a c t e r i s t i c o f k e t e n e s . ^ ^ F i g u r e 0.17 P h o t o c h e m i c a l [1.3] S h i f t s . T u r n i n g t o the b e n z o s e m i b u l l v a l e n e system, Bender and Wilson^-^ i n 1976, u n c o v e r e d a p h o t o c h e m i c a l [1,3] s h i f t r e a c t i o n w i t h compound 23. T h i s i n t e r e s t i n g v i n y l c y c l o p r o p a n e t o v i n y l c y c l o p r o p a n e rearrangement p r o c e e d e d w i t h d i r e c t o r a c e t o n e s e n s i t i z e d p h o t o l y s i s . The a u t h o r s s u g g e s t e d a t r i p l e t p r o c e s s , and no c o n c l u s i o n was made as t o whether a c o n c e r t e d p r o c e s s was i n v o l v e d . Bender e t a l . , i n a f o l l o w - u p t o t h i s d i s c o v e r y , s y n t h e s i z e d l a b e l l e d b e n z o s e m i b u l l v a l e n e 24 and d i m e t h y l b e n z o s e m i b u l l v a l e n e 25 ( F i g u r e 0.18) i n an a t t e m p t t o o b s e r v e a s i m i l a r [1,3] s h i f t r e a c t i o n . D i r e c t o r s e n s i t i z e d p h o t o l y s i s o f e i t h e r compounds 24 o r 25 y i e l d e d no v i n y l c y c l o p r o p a n e t o v i n y l c y c l o p r o p a n e r e a r r a n g e m e n t p r o d u c t s . These r e s u l t s were r a t i o n a l i z e d by the n e c e s s i t y t o have e l e c t r o n w i t h d r a w i n g groups on b o t h s i d e s o f the c l e a v e d 0 2 ^ - 0 5 ^ , bond i n o r d e r f o r t h e r e a c t i o n t o o c c u r . F i g u r e 0.18 Some B e n z o s e m i b u l l v a l e n e D e r i v a t i v e s S t u d i e d f o r the [1,3] S i g m a t r o p i c S h i f t . V I I . P h o t o c h e m i s t r y o f B e n z o b a r r e l e n e s I n t h e s t u d y o f t h e di-w-methane r e a r r a n g e m e n t o f d i b e n z o b a r r e l e n e d e r i v a t i v e s , S c h e f f e r e t a l . ^ ^ have f o u n d t h a t some o f t h e s e rearrangement pathways v a r y w i t h the phase o f t h e r e a c t i n g d i b e n z o b a r r e l e n e . D i b e n z o b a r r e l e n e systems c a n g i v e d i f f e r e n t p r o d u c t s d e p e n d i n g on w h i c h o f the f o u r i n i t i a l b o n d i n g modes i s f o l l o w e d ; n o t e t h a t the two i n i t i a l benzo-benzo b o n d i n g pathways a r e o m i t t e d as t h e y do n o t g i v e f e a s i b l e p r o d u c t s . C o n s e q u e n t l y , the f o u r p o s s i b l e p r o d u c t s a r e a l l d i b e n z o s e m i b u l l v a l e n e d e r i v a t i v e s , two r e g i o i s o m e r s and t h e i r e n a n t i o m e r s . F i g u r e 0.19 F e a s i b l e I n i t i a l B onding S i t e s i n t h e P h o t o c h e m i s t r y o f D i b e n z o b a r r e l e n e s . The f o c u s o f t h e p r e s e n t i n v e s t i g a t i o n i s on d i s u b s t i t u t e d d e r i v a t i v e s o f monobenzobarrelene. Di - 7 r-methane r e a r r a n g e m e n t s i n mono-b e n z o b a r r e l e n e d e r i v a t i v e s a r e much more c o m p l i c a t e d t h a n i n i t s d i b e n z o c o u n t e r p a r t ; t h e r e a r e now s i x f e a s i b l e i n i t i a l b o n d i n g s i t e s ( F i g u r e 0.20). A l s o i n the s e c o n d b o n d - b r e a k i n g s t e p o f the r e a r r a n g e m e n t , i t i s an e n e r g e t i c r e q u i r e m e n t f o r d i b e n z o b a r r e l e n e s t o r e g a i n a r o m a t i c i t y ; w i t h m o n o b e n z o b a r r e l e n e s , t h a t f a c t o r i s n o t always p r e s e n t . As a r e s u l t , the mono form may b r a n c h i n the second s t e p t o g i v e a n o t h e r h o s t o f p o s s i b l e p h o t o p r o d u c t s . The d i v e r s i t y o f pathways a v a i l a b l e make t h i s s t u d y more i n t e r e s t i n g and more c h a l l e n g i n g t h a n the d i b e n z o b a r r e l e n e systems. Some o f t h e p r o d u c t s o f F i g u r e 0.20 may be s t r u c t u r a l l y e q u i v a l e n t b u t be formed by d i f f e r e n t mechanisms. I t must a l s o be c o n s i d e r e d t h a t p r o d u c t s may a r i s e from non-di-jr-methane r e a c t i o n s as w e l l as from s e c o n d a r y p h o t o r e a c t i o n s . The p h o t o c h e m i s t r y o f monobenzobarrelenes has been l i t t l e s t u d i e d compared t o the d i b e n z o s e r i e s . I n 1963, K i t a h o n o k i and Takano^^ f i r s t r e p o r t e d t h e p h o t o c h e m i s t r y o f u n s u b s t i t u t e d b e n z o b a r r e l e n e (26) ( F i g u r e 0.21) by p h o t o l y z i n g i t t o b e n z o s e m i b u l l v a l e n e (28) i n a c e t o n e . Four y e a r s l a t e r , F r i e d m a n ^ ^ showed t h a t b e n z o b a r r e l e n e g i v e s b e n z o c y c l o -o c t a t e t r a e n e (27) upon d i r e c t i r r a d i a t i o n . The mechanisms t o t h e s e p h o t o p r o d u c t s were e l u c i d a t e d i n a c l a s s i c a l d e u t e r i u m l a b e l l i n g e x p e r i m e n t by Zimmerman e t a l . , ^ ^ i n 1968. They c o n c l u d e d t h a t t h e t r i p l e t b e n z o s e m i b u l l v a l e n e p r o d u c t i s d e r i v e d from a di-7r-methane r e a r r a n g e m e n t w i t h i n i t i a l v i n y l - v i n y l b o n d i n g ( F i g u r e 0.21), and the c y c l o o c t a t e t r a e n e comes from a s i n g l e t - m e d i a t e d [2+2] b e n z o - v i n y l c y c l o a d d i t i o n f o l l o w e d by an e l e c t r o c y c l i c r i n g o p e n i n g . F i g u r e 0.20 P o s s i b l e Pathways i n t h e P h o t o c h e m i s t r y o f 2 , 3 - D i s u b s t i t u t e d M o n o b e n z o b a r r e l e n e s . 2Z not isolated F i g u r e 0.21 P h o t o t r a n s f o r m a t i o n s o f the U n s u b s t i t u t e d B e n z o b a r r e l e n e ( 2 6 ) . Congruent w i t h the i n v e s t i g a t i o n o f compound 26 , G r o v e n s t e i n e t a l . ^ ^ r e p o r t e d an i n v e s t i g a t i o n o f the d i m e t h y l e s t e r d e r i v a t i v e 29, Brewer and Heaney^-'^ s t u d i e d the t e t r a f l u o r o a n a l o g 30, and Bender^^ s t u d i e d n a p h t h o b a r r e l e n e s 31 and 32 ( F i g u r e 0.22). Bender u l t i m a t e l y d e d i c a t e d h i s c a r e e r t o the s t u d y o f b e n z o b a r r e l e n e d e r i v a t i v e s and t h e i r p h o t o p r o d u c t s a t t h e U n i v e r s i t y o f L e t h b r i d g e , Canada. Many o f h i s t e c h n i q u e s a r e c r e a t i v e and e l e g a n t i n p i o n e e r i n g s t u d i e s i n t h i s s e r i e s . B e n z o b a r r e l e n e s 31-37 ( F i g u r e 0.22) a r e j u s t some o f the compounds s y n t h e s i z e d and p h o t o l y z e d by Bender t h r o u g h the y e a r s . ( r e f . 60) ( r e f . 62) ( r e f . 63) ( r e f . 64) ( r e f . 65) ( r e f . 65) ( r e f . 66) F i g u r e 0.22 L i s t o f Some S u b s t i t u t e d B e n z o b a r r e l e n e s P r e v i o u s l y S t u d i e d . The e s t a b l i s h e d t r e n d s a r e t h a t b e n z o c y c l o o c t a t e t r a e n e s come fr o m the s i n g l e t e x c i t e d s t a t e . The i n i t i a l i n t r a m o l e c u l a r [2+2] c y c l o a d d i t i o n i s between t h e chromophore and the most e a s i l y d i s r u p t e d jr-system. F o r example, the chromophore o f b e n z o b a r r e l e n e 26 i s t h e benzo-system; t h e r e f o r e , i n i t i a l b o n d i n g i s b e n z o - v i n y l . S i m i l a r l y , the d i e s t e r v i n y l i s the chromophore f o r compound 34 and i n i t i a l b o n d i n g i s d i e s t e r v i n y l -v i n y l . Di -7 r-methane r e a r r a n g e m e n t s o f b e n z o b a r r e l e n e s o c c u r t h r o u g h t h e t r i p l e t e x c i t e d s t a t e t o g i v e b e n z o s e m i b u l l v a l e n e s . U n l i k e the b e n z o c y c l o o c t a t e t r a e n e s , i n i t i a l b o n d i n g i s between t h e two most e a s i l y b r o k e n d o u b l e bonds. The l o n g e r t r i p l e t l i f e t i m e s a l l o w f o r i n t e r n a l e n e rgy t r a n s f e r t o t h e two l e s s s t a b l e 7r-systems f o r i n i t i a l bond f o r m a t i o n . Use o f s e n s i t i z e r s a l s o p r o v o k e s t h e same i n i t i a l b r i d g i n g . R e c a l l t h a t t r i p l e t s e n s i t i z a t i o n o f b e n z o b a r r e l e n e 26 ( F i g u r e 0.21) g i v e s i n i t i a l v i n y l - v i n y l b o n d i n g i n s t e a d o f b o n d i n g t o t h e benzo chromophore. W i t h u n s y m m e t r i c a l b e n z o b a r r e l e n e s , t h e s i d e o f i n i t i a l di - T T-methane b o n d i n g must a l s o be c o n s i d e r e d ; the s i d e w h i c h ca n p r o v i d e more s t a b i l i z a t i o n t o the r a d i c a l s formed i s t h e s i d e t h a t i s f a v o u r e d . T h i s i s e x e m p l i f i e d w i t h the 2-cyano d e r i v a t i v e 33 ( F i g u r e 0.22). The i n i t i a l b o n d i n g i s v i n y l - v i n y l on t h e s i d e o p p o s i t e t o the cyano group so t h a t t h e cyano group ca n r e s o n a n c e s t a b i l i z e one o f the two newly formed r a d i c a l s . O n l y a s m a l l number o f d e r i v a t i v e s has been s t u d i e d . T h e r e f o r e , t h e r e i s s t i l l much to be u n d e r s t o o d w i t h r e s p e c t t o t h e s o l u t i o n b e h a v i o r o f b e n z o b a r r e l e n e s . These p r o p o s e d t r e n d s have y e t t o be f u l l y t e s t e d . I n a d d i t i o n , the many s e c o n d a r y p h o t o p r o d u c t s formed have opened new a r e a s o f r e s e a r c h as Bender has r e a l i z e d i n h i s r e c e n t s t u d i e s . ' One o f h i s l a t e s t i n v e s t i g a t i o n s i s w i t h the p h o t o c h e m i s t r y o f 2 , 3 - b e n z o b i c y c l o [ 4 . 2 . 0 ] o c t a - 2 , 4 , 7 - t r i e n e d e r i v a t i v e 39,^^ a p h o t o p r o d u c t o f b e n z o c y c l o o c t a t e t r a e n e 38a, w h i c h i n t u r n i s a s i n g l e t p h o t o p r o d u c t o f a b e n z o b a r r e l e n e 38. Compound 39 undergoes a t r i p l e t di-;r-methane r e a r r a n g e m e n t t o a f f o r d b e n z o s e m i b u l l v a l e n e 39a. ( r e f . 68) F i g u r e 0.23 P h o t o c h e m i s t r y o f l - C y a n o - 2 , 3 - b e n z o b i c y c l o [ 4 . 2 . O ] o c t a -2 , 4 , 7 - t r i e n e ( 3 9 ) . V I I I . O b j e c t o f R e s e a r c h I n t h i s t h e s i s , d i s u b s t i t u t e d b e n z o b a r r e l e n e s a r e s y n t h e s i z e d and i r r a d i a t e d t o a s s i s t i n a b e t t e r u n d e r s t a n d i n g o f s o l u t i o n phase b e n z o b a r r e l e n e p h o t o c h e m i s t r y and, more i n t e r e s t i n g l y , t o p r o v i d e the f i r s t r e p o r t s ^ ^ o f monobenzobarrelene p h o t o c h e m i s t r y i n the c r y s t a l l i n e phase as w e l l as i n polymer medium. For c l a r i t y , the R e s u l t s and D i s c u s s i o n s e c t i o n i s d i v i d e d i n t o s e v e n p a r t s . The p r e p a r a t i o n o f the s t a r t i n g m a t e r i a l s i s d e s c r i b e d i n P a r t I o f t h i s t h e s i s . The f u n d a m e n t a l s t e p i n the s y n t h e s i s o f the b e n z o b a r r e l e n e r i n g system stems from a D i e l s - A l d e r a d d i t i o n o f a n a p h t h a l e n e t o an a c e t y l e n e d e r i v a t i v e . S u b s t i t u e n t a l t e r a t i o n s can be done p r i o r o r subsequent t o t h i s a d d i t i o n . One u n i q u e f e a t u r e a s s o c i a t e d w i t h t h i s di - 7 r-methane s t u d y i s t h a t a l l t h e p r o d u c t s a r e d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s ( F i g u r e 0.20). N u c l e a r m a g n e t i c reson a n c e s p e c t r o s c o p y (NMR) o f t h e s e p h o t o p r o d u c t s i s e x t r e m e l y i n f o r m a t i v e , as the f o u r p r o t o n s on the d i s u b s t i t u t e d s e m i b u l l v a l e n e s k e l e t o n p o s s e s s d i s t i n c t i v e c h e m i c a l s h i f t s and c o u p l i n g p a t t e r n s . P a r t I I o f t h i s t h e s i s d e t a i l s the a s s i g n m e n t o f benzosemi-b u l l v a l e n e r e g i o i s o m e r s from s p e c t r o s c o p i c t e c h n i q u e s . P a r t I I I o f t h i s t h e s i s d e a l s i n i t i a l l y w i t h d i m e t h y l 1 , 4 - d i h y d r o -l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l a t e (29, F i g u r e 0.24). The p h o t o c h e m i s t r y o f t h i s compound was i n v e s t i g a t e d by G r o v e n s t e i n i n 1969.^^ He r e p o r t e d the f o r m a t i o n o f a b e n z o c y c l o o c t a t e t r a e n e d e r i v a t i v e upon d i r e c t p h o t o l y s i s and a 5 : 3 : 2 r a t i o o f t h r e e u n i d e n t i f i e d p r o d u c t s from a c e t o n e s e n s i t i z a t i o n . I n t h i s s t u d y , i t was c o n s i d e r e d e s s e n t i a l t o d e t e r m i n e the n a t u r e o f t h e s e t h r e e t r i p l e t p h o t o p r o d u c t s i n o r d e r t o become f a m i l i a r w i t h t h i s system and t o p r o c e e d i n t o t h e s o l i d phase. F i g u r e 0.24 S y m m e t r i c a l D i s u b s t i t u t e d B e n z o b a r r e l e n e s S t u d i e d . S e v e r a l o t h e r s y m m e t r i c a l d i s u b s t i t u t e d b e n z o b a r r e l e n e s a r e a l s o i n v e s t i g a t e d i n P a r t I I I t o a s c e r t a i n the e f f e c t s o f d i f f e r e n t s u b s t i t u e n t p a t t e r n s on b e n z o b a r r e l e n e p h o t o c h e m i s t r y . The s u b s t r a t e s a r e shown i n F i g u r e 0.24. F a v o r a b l e t o the i n t e n t i o n s , the l a s t s y m m e t r i c a l s y s t e m i n v e s t i g a t e d , 2 , 3 - d i b e n z o y l b e n z o b a r r e l e n e 42, u n l i k e the o t h e r s , e f f i c i e n t l y i n t e r s y s t e m c r o s s e s t o g i v e o n l y t r i p l e t p r o d u c t s i n s o l u t i o n and the s o l i d s t a t e . The u n s y m m e t r i c a l b e n z o b a r r e l e n e s s t u d i e d i n P a r t IV o f t h i s t h e s i s a r e r e l a t e d t o d i b e n z o y l d e r i v a t i v e 42. The o b s e r v a t i o n o f i t s ease i n i n t e r s y s t e m c r o s s i n g makes t h i s an i d e a l system. I f one o f t h e b e n z o y l groups i s r e p l a c e d w i t h an e s t e r , t h e a l k o x y group o f t h e e s t e r can e a s i l y be a l t e r e d t o l i t t l e a f f e c t the s o l u t i o n p h o t o c h e m i s t r y b u t d r a m a t i c a l l y r e o r g a n i z e the c r y s t a l p a c k i n g . T h i s i n t u r n w i l l h o p e f u l l y d e m o n s t r a t e t h e e f f e c t s o f v a r y i n g t h e c r y s t a l l a t t i c e on s o l i d s t a t e s e l e c t i v i t y . Upon n o t i n g the s t r i k i n g s e l e c t i v i t y d i f f e r e n c e s f ound i n g o i n g from s o l u t i o n t o the s o l i d s t a t e , the s e r i e s was a l s o s t u d i e d i n p o lymer m a t r i x media. F i g u r e 0.25 U n s y m m e t r i c a l B e n z o b a r r e l e n e s S t u d i e d . V a r y i n g t h e s u b s t i t u e n t s on a m o l e c u l e u n d o u b t e d l y changes the c r y s t a l p a c k i n g , w h i c h i s what i s d e s i r e d i n t h i s s t u d y . P a r t V d e m o n s t r a t e s t h e use o f s a l t s t o a l t e r c r y s t a l p a c k i n g f o r e s s e n t i a l l y t he same m o l e c u l e . I n t h e o r y , the s o l u t i o n p h o t o c h e m i s t r y s h o u l d n o t be a f f e c t e d s i g n i f i c a n t l y by s i m p l y a l t e r i n g t he c o u n t e r i o n . D i f f e r e n t o r g a n i c and i n o r g a n i c s a l t s o f b e n z o b a r r e l e n e d i c a r b o x y l i c a c i d 40 were s y n t h e s i z e d and p h o t o l y z e d b o t h i n s o l u t i o n and i n the s o l i d s t a t e . The e f f e c t s o f the d i f f e r e n t c r y s t a l l a t t i c e e n v i r o n m e n t s on the s o l i d s t a t e r e a c t i o n s can be d i r e c t l y measured from the d i f f e r e n t r a t i o s o f t r i p l e t p r o d u c t s formed. I n a d d i t i o n , some s a l t s a r e s y n t h e s i z e d i n an a t t e m p t t o d e l i b e r a t e l y a f f e c t i n t e r s y s t e m c r o s s i n g t o enhance the f o r m a t i o n o f t r i p l e t p h o t o p r o d u c t s . F i g u r e 0.26 S a l t s o f B e n z o b a r r e l e n e D i c a r b o x y l i c A c i d . The d i s c o v e r y o f an u n u s u a l tri- T T-me t h a n e ' " r e a r r a n g e m e n t i n S c h e f f e r ' s group w i t h t h e s t u d y o f 9 , 1 0 - d i m e t h y l d i b e n z o b a r r e l e n e 46^ -'-( F i g u r e 0.27) i n s p i r e d an i n v e s t i g a t i o n o f the g e n e r a l i t y o f t h i s r e a r r a n g e m e n t t o o t h e r b a r r e l e n e systems. A t r i - T T - m e t h a n e r e a r r a n g e m e n t i s a r e a c t i o n w h i c h u n d e r s t a n d a b l y i n v o l v e s t h r e e jr-systems s e p a r a t e d by a s a t u r a t e d c a r b o n . I n P a r t V I , t h e monobenzobarrelene a n a l o g o f compound 46, d i m e t h y l 1 , 4 - d i h y d r o - l , 4 , 5 , 8 - t e t r a m e t h y l - 1 , 4 - e t h e n o n a p h t h a l e n e -2 , 3 - d i c a r b o x y l a t e ( 4 7 ) , was s y n t h e s i z e d and i r r a d i a t e d . F i g u r e 0.27 B r i d g e h e a d M e t h y l a t e d B a r r e l e n e D i m e t h y l E s t e r s . C u m u l a t i v e l y , t h r o u g h t h i s s t u d y i t was n o t i c e d t h a t many o f the b e n z o s e m i b u l l v a l e n e p h o t o p r o d u c t s e f f i c i e n t l y underwent s e c o n d a r y p h o t o c h e m i c a l [1,3] s h i f t s . A l t h o u g h p h o t o c h e m i c a l [1,3] s h i f t s a r e f a r from uncommon, few have been r e p o r t e d i n the b e n z o s e m i b u l l v a l e n e system. P a r t V I I b r i e f l y a s s e s s e s t h e s e [1,3] s h i f t s i n c o n j u n c t i o n w i t h t h e p h o t o s t a t i o n a r y s t a t e s i n w h i c h t h e y a r e f o u n d t o f r e q u e n t l y e x i s t . RESULTS AND DISCUSSION PART I. PREPARATION OF STARTING MATERIALS The basic structure of the s t a r t i n g materials possess the formal nomenclature of "1,4-dihydro-1,4-ethenonaphthalene," and the numbering i s shown in Figure 1.01. The o r i g i n of t h i s nomenclature stems from the naphthalene ring system, however, the skeleton i s known more commonly as "benzobarrelene". Throughout the th e s i s , the two names w i l l be used interchangeably. Following the method of Grovenstein et a l . , ^ ^ dimethyl 1,4-dihydro-1,4-ethenonaphthalene-2,3-dicarboxylate (29) was prepared by the addition of dimethyl acetylenedicarboxylate to naphthalene i n a thermal [4+2] cycloaddition reaction (Diels-Alder r e a c t i o n ) . F i g u r e 1.01 S y n t h e s i s o f B e n z o b a r r e l e n e D i e s t e r 29 from a D i e l s - A l d e r R e a c t i o n . I t has been w e l l r e c o g n i z e d t h a t n a p h t h a l e n i c systems a r e poor d i e n e s f o r D i e l s - A l d e r a d d i t i o n . The p r e p a r a t i o n o f compound 29 above r e q u i r e s h e a t i n g i n a s e a l e d tube f o r 72 h o u r s , and t h e r e p o r t e d y i e l d o f 25% i s c o n s i d e r e d t o be good. I n l i g h t o f t h i s , many b e n z o b a r r e l e n e s s t u d i e d h e r e were p r e p a r e d t h r o u g h d e r i v a t i z a t i o n o f d i e s t e r 29. S y n t h e s i s o f 1 , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c a c i d (40) i s a c h i e v e d t h r o u g h the s a p o n i f i c a t i o n o f d i e s t e r 29 ( F i g u r e 1.02). E x t e n d i n g from t h i s , 1 , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c a n h y d r i d e 41 i s p r e p a r e d i n a 24 hour d e h y d r a t i o n o f d i a c i d 40 u s i n g o x a l y l c h l o r i d e . A l l t h r e e compounds (29, 40, and 41) a r e s o l i d s and c a n be e a s i l y p u r i f i e d by r e c r y s t a l l i z a t i o n . F i g u r e 1.02 D e r i v a t i z a t i o n o f B e n z o b a r r e l e n e D i m e t h y l E s t e r 29. The p a r t i a l l y d e u t e r a t e d v e r s i o n s o f t h e s e s t a r t i n g m a t e r i a l s were a l s o p r e p a r e d . The r e p l a c e m e n t o f a bromo group w i t h d e u t e r i u m i n a G r i g n a r d r e a c t i o n gave 1 - d e u t e r i o n a p h t h a l e n e ^ ^ from 1-bromo-n a p h t h a l e n e , i n a c a . 95% i s o t o p i c p u r i t y . The 1 - d e u t e r i o n a p h t h a l e n e was u s e d i n p l a c e o f n a p h t h a l e n e i n the s y n t h e t i c r o u t e s d e s c r i b e d i n F i g u r e s 1.01 and 1.02. As a r e s u l t , d e u t e r i u m i s e v e n l y d i s t r i b u t e d o v e r t h e 1,4,5, and 8 p o s i t i o n s o f t h e b e n z o b a r r e l e n e r i n g . The NMR s p e c t r a o f n o n - d e u t e r a t e d and s e l e c t i v e l y d e u t e r a t e d b e n z o b a r r e l e n e 29 a r e p r o v i d e d i n F i g u r e 1.03. N o t i c e t h a t t h e C^ ^ and C 4 p o s i t i o n s and t h e C 5 and C 3 p o s i t i o n s a r e m a g n e t i c a l l y e q u i v a l e n t owing t o the p l a n e o f symmetry p r e s e n t i n the m o l e c u l e . u ' J " " " " ' J 7 ^ 'I 3 ppm 1/4D 1/4D CO2CH3 C O o C H , 1MD ppm F i g u r e 1.03 NMR S p e c t r a o f B e n z o b a r r e l e n e 29 and P a r t i a l l y D e u t e r a t e d B e n z o b a r r e l e n e 29-D i n C D C I 3 . S y n t h e s i s o f 2 , 3 - d i b e n z o y l - 1 , 4 - d i h y d r o - 1 , 4 - e t h e n o n a p h t h a l e n e (42) was a c c o m p l i s h e d t h r o u g h the D i e l s - A l d e r r e a c t i o n o f d i b e n z o y l -a c e t y l e n e (57) w i t h n a p h t h a l e n e ( F i g u r e 1.04). A f t e r 1 1/2 hours o f h e a t i n g i n a s e a l e d tube (180 °C), the a l k y n e was d e p l e t e d t o g i v e a 19% y i e l d o f 42 a f t e r chromatography. D i b e n z o y l a c e t y l e n e (57) was s y n t h e s i z e d from the p r o c e d u r e o f R.E. L u t z i n 1951. Stemming from f u m a r y l c h l o r i d e , two e q u i v a l e n t s o f benzene a r e added i n a F r i e d e l - C r a f t s r e a c t i o n , c a t a l y z e d by anhydrous aluminum t r i c h l o r i d e , t o g i v e t r a n s - 1 , 4 - d i p h e n y l - 2 - b u t e n e - l , 4 - d i o n e (55). The v i n y l group o f e n e - d i o n e 55 i s t h e n r e a c t e d w i t h bromine t o g i v e good y i e l d s o f meso 2 , 3 - d i b r o m o - l , 4 - d i p h e n y l b u t a n e - l , 4 - d i o n e (56), and f i n a l l y , 1 , 4 - d i p h e n y l - 2 - b u t y n e - 1 , 4 - d i o n e (57) i s p r e p a r e d from d i b r o m i d e 56 by the a d d i t i o n o f t r i e t h y l a m i n e i n an e l i m i n a t i o n r e a c t i o n . F i g u r e 1.04 P r e p a r a t i o n o f 2 , 3 - D i b e n z o y l - 1 , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e ( 4 2 ) . The -"-H NMR s p e c t r a o f s y m m e t r i c a l b e n z o b a r r e l e n e s 40 and 41 a r e shown i n F i g u r e 1.05. I n t e r e s t i n g l y , t h e b e n z o b a r r e l e n e s k e l e t o n c a r r i e s a u n i q u e s e t o f s i g n a l s . The b r i d g e h e a d (C^^ and C 4 ) p r o t o n s r e s o n a t e between 5-6 ppm w i t h a d o u b l e t o f d o u b l e t s c o u p l i n g p a t t e r n ; t h i s m u l t i p l i c i t y comes from a s t r o n g (5 Hz) c o u p l i n g t o i t s v i n y l n e i g h b o r a l o n g w i t h a weaker (2 Hz) f o u r bond d i s t a n t c o u p l i n g t o t h e o p p o s i t e v i n y l . The v i n y l p r o t o n s r e s o n a t e i n the a r o m a t i c r e g i o n ; however, t h e y c a n be d i s t i n g u i s h e d from t h e a r o m a t i c s by t h e c o u p l i n g c o n s t a n t s . I n a d d i t i o n , the two groups o f a r o m a t i c p r o t o n s a r e e a s i l y d i f f e r e n t i a t e d by NMR i n t e g r a t i o n o f the d e u t e r i u m l a b e l l e d compounds shown i n F i g u r e 1.03. F i g u r e 1.05 H NMR S p e c t r a o f S y m m e t r i c a l B e n z o b a r r e l e n e s 40 (DHSO-dg) and 41 ( C D C I 3 ) . The s y n t h e s i s o f u n s y m m e t r i c a l b e n z o y l m e t h y l e s t e r b e n z o b a r r e l e n e 43 was a c h i e v e d t h r o u g h f u r t h e r m a n i p u l a t i o n o f t h e s y m m e t r i c a l b e n z o b a r r e l e n e a n h y d r i d e 41 ( F i g u r e 1.06). The a n h y d r i d e r i n g was opened by r e a c t i o n w i t h d r y m e t h a n o l , and work-up gave 1 , 4 - d i h y d r o - l , 4 -e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c a c i d monomethyl e s t e r ( 5 8 ) . T h i s a c i d e s t e r was r e a c t e d w i t h o x a l y l c h l o r i d e t o g i v e a c y l c h l o r i d e e s t e r 59; t h i s was i m m e d i a t e l y r e a c t e d w i t h benzene i n a F r i e d e l - C r a f t s a c y l a t i o n c a t a l y z e d by anhydrous aluminum t r i c h l o r i d e t o y i e l d t h e d e s i r e d b e n z o b a r r e l e n e 43. The e s t e r s i d e - c h a i n can be e a s i l y a l t e r e d u nder a c i d i c c o n d i t i o n s t o g i v e the c o r r e s p o n d i n g e t h y l and i s o p r o p y l e s t e r s (44 and 45, r e s p e c t i v e l y ) . These b e n z o y l e s t e r s a r e h i g h l y c r y s t a l l i n e making them i d e a l f o r s o l i d s t a t e s t u d i e s . S e l e c t i v e l y d e u t e r a t e d b e n z o y l m e t h y l e s t e r 43 was a l s o p r e p a r e d . T h i s was done by t a k i n g the 1,4,5,8 - l a b e l l e d a n h y d r i d e 41 t h r o u g h the d e s c r i b e d s y n t h e t i c r o u t e ( F i g u r e 1.06). The r e s u l t i n g b e n z o y l m e t h y l e s t e r 43 was a m onodeuterated m i x t u r e w i t h the d e u t e r i u m p l a c e d i n t h e C]^, C 4 , C 5 , and C 3 p o s i t i o n s . F o r s i m p l i c i t y , t h i s m i x t u r e i s r e p r e s e n t e d d i a g r a m m a t i c a l l y as a s i n g l e m o l e c u l e w i t h a 0.25 d e u t e r a t i o n on t h e C^ ,^ C 4 , C 5 , and Cg p o s i t i o n s (43-D). a) 41 o 43 O EtOH A , H+ M O 7 ~ P h MeOH MCI. Benzene Je O 52 O O C H 3 OH Oxalyl Chloride CH2CI2 O - O C H . Cl 53 O b) F i g u r e 1.06 a) P r e p a r a t i o n o f B e n z o y l E s t e r s 43, 44, and 45. b) Monodeuterated B e n z o y l M e t h y l E s t e r (43-D). The NMR s p e c t r a o f u n s y m m e t r i c a l b e n z o b a r r e l e n e s a l s o c o n t a i n a u n i q u e p a t t e r n o f s i g n a l s a s s o c i a t e d w i t h the s k e l e t o n ( F i g u r e 1 . 0 7 ) . The b r i d g e h e a d (Cj^ and C 4 ) p r o t o n s a r e no l o n g e r e q u i v a l e n t and r e s o n a t e as two a d j a c e n t d o u b l e t o f d o u b l e t s between 5-6 ppm. Due t o t h e l a c k o f symmetry, the a r o m a t i c and v i n y l p r o t o n s i g n a l s o v e r l a p as a complex m u l t i p l e t between 6.9-7.6 ppm and a r e t h e r e f o r e l e s s i n f o r m a t i v e . F i g u r e 1.07 NMR S p e c t r a o f B e n z o y l E s t e r s 43 and 45 i n CDCl The amine s a l t s o f 1 , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 -d i c a r b o x y l i c a c i d (40) were p r e p a r e d by d i s s o l v i n g t h e a c i d w i t h a s t o i c h i o m e t r i c amount o f an amine i n e t h y l a c e t a t e o r a c e t o n i t r i l e . The s o l u t i o n was s t i r r e d under r e f l u x f o r a p p r o x i m a t e l y one ho u r and the c o r r e s p o n d i n g s a l t forms a p r e c i p i t a t e w h i c h can be e a s i l y f i l t e r e d . W i t h amine dou b l e s a l t s , a s l i g h t e x c e s s o f t h e amine was used, and f o r i n o r g a n i c s a l t s , a s t o i c h i o m e t r i c amount o f t h e c a t i o n as a h y d r o x i d e i n w a t e r was added t o the d i a c i d i n a c e t o n i t r i l e . C r y s t a l s o f the d e r i v e d s a l t s were grown from s u i t a b l e s o l v e n t s . The s a l t s p r e p a r e d , shown i n F i g u r e 0.26, were c h a r a c t e r i z e d by a n a l y t i c a l t e c h n i q u e s s u c h as NMR, IR, MS-DCI, C-H a n a l y s i s , and mp. The n e x t s u b s t r a t e i n v e s t i g a t e d i n the t h e s i s , d i m e t h y l 1,4-d i h y d r o - 1 , 4 , 5 , 8 - t e t r a m e t h y l - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l a t e (47) was p r e p a r e d from t h e D i e l s - A l d e r a d d i t i o n o f d i m e t h y l a c e t y l e n e -d i c a r b o x y l a t e (DMAD) t o 1 , 4 , 5 , 8 - t e t r a m e t h y l n a p h t h a l e n e (64) ( F i g u r e 1.08). DMAD i s c o m m e r c i a l l y a v a i l a b l e , b u t , n a p h t h a l e n e d e r i v a t i v e 64 i s n o t . The method d e v i s e d by W.L. Mosby^^ i n 1952 was u s e d t o s y n t h e s i z e compound 64. The f i r s t s t e p i n v o l v e s t h e r e a c t i o n o f anhydrous p - x y l e n e w i t h 7 - v a l e r o l a c t o n e i n the p r e s e n c e o f anhydrous aluminum t r i c h l o r i d e . The y i e l d o f t h e r e s u l t i n g 4 - ( 2 , 5 - d i m e t h y l p h e n y l ) - p e n t a n o i c a c i d (60) was 90%. Compound 60 i s t h e n t r e a t e d w i t h p y r o p h o s p h o r i c a c i d f a c i l i t a t i n g a d e h y d r a t i o n r i n g c l o s u r e t o g i v e 2 , 3 - d i h y d r o - 4 , 5 , 8 - t r i m e t h y l - 1 -n a p h t h a l o n e ( 6 1 ) . The c a r b o n y l group o f k e t o n e 61 was r e a c t e d w i t h m e t h y l l i t h i u m , g i v i n g 1 , 2 , 3 , 4 - t e t r a h y d r o - 1 , 4 , 5 , 8 - t e t r a m e t h y l -1 - n a p h t h o l (62) i n 88% y i e l d . T h i s crude n a p h t h o l i s t h e n s t i r r e d a t room t e m p e r a t u r e i n a c i d i f i e d t e t r a h y d r o f u r a n (THF) t o g i v e 1 , 2 - d i h y d r o - 1 , 2 , 5 , 8 - t e t r a m e t h y l n a p h t h a l e n e (63) i n a d e h y d r a t i o n r e a c t i o n . F i n a l l y , the 1 , 4 , 5 , 8 - t e t r a m e t h y l n a p h t h a l e n e (64) i s formed from a c a t a l y z e d h i g h t e m p e r a t u r e d e h y d r o g e n a t i o n o f compound 63. The y i e l d i n t h i s l a s t s t e p i s 17%. S i n c e 1952, s e v e r a l o t h e r s y n t h e t i c r o u t e s t o n a p h t h a l e n e d e r i v a t i v e 64 have been r e p o r t e d . H o w e v e r , due t o s i m p l e a v a i l a b i l i t y o f r e a g e n t s , the method o f Mosby was used. F i g u r e 1.08 S y n t h e s i s o f T e t r a m e t h y l B e n z o b a r r e l e n e D i m e t h y l E s t e r 47. PART I I . CHARACTERIZATION OF DISUBSTITUTED BENZOSEMIBULLVALENE PHOTOPRODUCTS Most o f the p h o t o p r o d u c t s s y n t h e s i z e d i n t h i s t h e s i s a r e b e n z o s e m i b u l l v a l e n e s , e i t h e r from t he di-7r-methane r e a r r a n g e m e n t o r from a l t e r n a t i v e mechanisms. B e f o r e embarking on d i s c u s s i o n s o f e l a b o r a t e r e a c t i o n mechanisms, a s t r o n g f o u n d a t i o n must be e s t a b l i s h e d w i t h r e s p e c t t o t h e s t r u c t u r a l a s s i gnment o f t h e s e p h o t o p r o d u c t s . B e n z o s e m i b u l l v a l e n e has the b a s i c s k e l e t o n d e p i c t e d i n F i g u r e 2.01. The p r o p e r C h e m i c a l A b s t r a c t s name i s t a k e n from t he p e n t a l e n e s t r u c t u r e . P e n t a l e n e , i n a d d i t i o n t o a numbering system t o d e s c r i b e t he c a r b o n s , has an a l p h a b e t i c a l system t o r e p r e s e n t t h e d i f f e r e n t c a r b o n - c a r b o n bonds o f the r i n g system. The p r o p e r C h e m i c a l A b s t r a c t s name f o r b e n z o s e m i b u l l v a l e n e i s 2 a , 2 b , 6 b , 6 c - t e t r a h y d r o b e n z o [ a ] c y c l o -p r o p a [ c d ] p e n t a l e n e . The " 2 a , 2 b , 6 b , 6 c - t e t r a h y d r o " d e s c r i b e s t he p o s i t i o n and number o f the hydrogens on t h e p e n t a l e n e s k e l e t o n . The " b e n z o [ a ] " i n d i c a t e s a benzo group a t the a bond, and the " c y c l o p r o p a [ c d ] " denotes t h a t t he c and d bonds a r e i n v o l v e d i n a c y c l o p r o p y l r i n g . ^ * ^ S u b s t i t u e n t d e s c r i p t i o n s a r e p r e c e d e d by a number i n d i c a t i n g t h e i r l o c a t i o n on the b e n z o s e m i b u l l v a l e n e s k e l e t o n . The d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s a r e most i n f o r m a t i v e l y c h a r a c t e r i z e d by n u c l e a r magnetic r e s o n a n c e , i n f r a r e d s p e c t r o s c o p y , and mass s p e c t r o m e t r y . The NMR p r o t o n r e s o n a n c e s on t h e benzo-s e m i b u l l v a l e n e s k e l e t o n o c c u r between 3.0 and 6.5 ppm; T h i s r e g i o n i s r e l a t i v e l y c l e a r i n the NMR spectrum, as the s a t u r a t e d h y d r o c a r b o n s i g n a l s u s u a l l y appear u p f i e l d o f 3 ppm and a r o m a t i c p r o t o n s appear d o w n f i e l d o f 7 ppm. As a r e s u l t , s e m i b u l l v a l e n e peaks a r e e a s i l y d i s t i n g u i s h e d and seldom s u f f e r from o v e r l a p w i t h o t h e r s i g n a l s . Where p o s s i b l e , m e l t i n g p o i n t s and e l e m e n t a l a n a l y s e s were t a k e n . X - r a y a n a l y s e s were p e r f o r m e d o n l y i n s i t u a t i o n s where the s t r u c t u r e s c o u l d n o t be f i r m l y a s s i g n e d from NMR t e c h n i q u e s . Pentalene Benzosemibullvalene F i g u r e 2.01 a) S t r u c t u r e o f P e n t a l e n e . b) S t r u c t u r e o f B e n z o s e m i b u l l v a l e n e o r 2 a , 2 b , 6 b , 6 c - T e t r a h y d r o -b e n z o [ a ] c y c l o p r o p a t c d ] p e n t a l e n e . A. C h a r a c t e r i z a t i o n o f 2 a , 6 c - D i s u b s t i t u t e d - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o -p r o p a [ c d ] p e n t a l e n e . The p r o t o n NMR s p e c t r a o f some 2 a , 6 c - d i s u b s t i t u t e d benzosemi-b u l l v a l e n e s a r e shown i n F i g u r e s 2.02 and 2.03. The s k e l e t a l p r o t o n s o f the 2 a , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s a l l have s i m i l a r c o u p l i n g and c h e m i c a l s h i f t p a t t e r n s . The most s h i e l d e d a r e and Hg},, g i v i n g r i s e t o a s i n g l e t and a d o u b l e t ( J = 3 H z ) , r e s p e c t i v e l y . The n e x t most s h i e l d e d s i g n a l comes from the C2 v i n y l p r o t o n as a d o u b l e t ( J = 5 H z ) , and the most d e s h i e l d e d p r o t o n on the s e m i b u l l v a l e n e s k e l e t o n i s on C]^, a d o u b l e t o f d o u b l e t s ( J = 5,3 H z ) . The f o u r a r o m a t i c p r o t o n s r e s o n a t e as a complex m u l t i p l e t above 7 ppm. The c h e m i c a l s h i f t s from compound t o compound v a r y s l i g h t l y b u t the p a t t e r n and c o u p l i n g c o n s t a n t s r e m a i n s i m i l a r . H '2b H, 6b PPM •.4 4.1 ppm F i g u r e 2.03 P r o t o n NMR E x p a n s i o n s o f 2 a , 6 c - D i s u b s t i t u t e d Benzosemi-b u l l v a l e n e s 29a i n C D C I 3 and 40a i n DMSO-dg. B. C h a r a c t e r i z a t i o n o f 1 , 6 c - D i s u b s t i t u t e d - 2 b , 6 b ( 2 a H ) - d i h y d r o b e n z o [ a ] -c y c l o p r o p a [ c d ] p e n t a l e n e s . The NMR s p e c t r a l d a t a f o r some 1 , 6 c - d i s u b s t i t u t e d benzosemi-b u l l v a l e n e s a r e shown i n F i g u r e 2.04. P a r a l l e l t o t h e s i t u a t i o n o f t h e 2 a , 6 c - d i s u b s t i t u t e d a n a l o g s , the p r o t o n s on t h e s e m i b u l l v a l e n e r i n g r e s o n a t e between 3.0 and 6.5 ppm, c l e a r o f t h e a r o m a t i c and s a t u r a t e d h y d r o c a r b o n p r o t o n r e s o n a n c e s . The s e m i b u l l v a l e n e NMR p a t t e r n o f 1 , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e systems i s a l s o v e r y c h a r a c t e r i s t i c . Most s h i e l d e d i s the Q^a. P h o t o n d o u b l e t o f d o u b l e t s ( J = 8,3 H z ) . Next i s the C2b p r o t o n d o u b l e t ( J = 8 Hz) f o l l o w e d by t h e p r o t o n o f Cg|3 as a s i n g l e t . C o n s i d e r a b l y d o w n f i e l d i s the C2 v i n y l p r o t o n d o u b l e t ( J = 3 Hz) a t about 6 ppm. The a r o m a t i c p r o t o n s o f the benzo group r e s o n a t e as a complex m u l t i p l e t above 7 ppm. F i g u r e 2.04 NMR S p e c t r a l E x p a n s i o n s o f 1 , 6 c - D i s u b s t i t u t e d Benzosemi-b u l l v a l e n e s 29b and 43c i n CDClo. c. C h a r a c t e r i z a t i o n o f 1 , 2 - D i s u b s t i t u t e d - 2 a , 2 b , 6 b , 6 c - t e t r a h y d r o b e n z o -[ a ] c y c l o p r o p a [ c d ] p e n t a l e n e s . NMR s p e c t r o s c o p y p r o v e d t o be e s s e n t i a l i n t h e c h a r a c t e r i z a t i o n o f t h i s s e t o f p h o t o p r o d u c t s . Shown i n F i g u r e 2.05 a r e t h e NMR s p e c t r a l e x p a n s i o n s o f some 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s . The p r o t o n c o u p l i n g p a t t e r n o f t h i s s e m i b u l l v a l e n e s k e l e t o n i s c o n s i s t e n t l y u n i q u e . The most s h i e l d e d p r o t o n s i g n a l i s a d o u b l e t o f d o u b l e t s . However, the c o u p l i n g s t r e n g t h t o each o f i t s n e i g h b o r s (C2b and Cg^,) i s the same ( J == 6 H z ) ; as a r e s u l t , t he s i g n a l appears as a t r i p l e t . The d o u b l e t o f d o u b l e t s o f t h e 02^ p r o t o n a l s o appears as a t r i p l e t from i d e n t i c a l c o u p l i n g t o i t s n e i g h b o r s ( J = 6 H z ) , s l i g h t l y d o w n f i e l d o f €2^. The d o u b l e t o f d o u b l e t o f d o u b l e t s s i g n a l from the Cg^, p r o t o n a l s o has t h e same c o u p l i n g s t r e n g t h ( J = 6 Hz) t o a l l t h r e e o f i t s n e i g h b o r s , r e s u l t i n g i n a q u a r t e t f u r t h e r d o w n f i e l d from the two t r i p l e t s . F i n a l l y , t he Cg^, p r o t o n d o u b l e t ( J = 6 Hz) i s most d e s h i e l d e d , a t about 4.3 ppm. 2b 2a CO,H 6b COjH H 2a 5.5 5. 0 4. 5 COPh 43d — I — ^ — 4. 0 pprt COPh •CO2CH3 43e 43d 43d+43e 43e 3.5 43d 43d — I — 5. 0 43e 43e 43e 43d I ' ' I I I I T I I I • . U J 4. 2 4. 0 i. 8 ' ' I ' ' ' ' I 3 . 6 I ' ' I ' 3 4 3 . 2 I I I I I I I ' I I I I I i 0 PPM F i g u r e 2.05 NMR S p e c t r a l E x p a n s i o n s o f 1 , 2 - D l s u b s t i t u t e d Benzosemi-b u l l v a l e n e s 40b and a m i x t u r e o f 43d and 43e. The 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s 43d and 43e a r e i n s e p a r a b l e by column chromatography, and an e x p a n s i o n o f the p r o t o n NMR i s shown i n F i g u r e 2.05. From r e l a t i v e s i n g l e p r o t o n s i g n a l i n t e n s i t i e s , t he peaks o f one compound c a n be e a s i l y d i s t i n g u i s h e d from t h o s e o f the o t h e r . The s i g n a l p a t t e r n s o f the two compounds c l e a r l y i n d i c a t e t h a t t h e y a r e b o t h 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e d e r i v a t i v e s . However, a m b i g u i t y a r i s e s w i t h r e s p e c t t o the r e l a t i v e p o s i t i o n s o f the m e t h y l e s t e r and the b e n z o y l g r o u p s . E = methoxyl B = phenyl 2a B(E) H E(B) 2.08 ppm o o 5.95 ppm I OCH3 - 9 8.40 ppm CH3 r 1.98 ppm O C H 3 substituted region of benzosemibullvalene S5a 65b F i g u r e 2.06 R e l a t i v e D e s h i e l d i n g C a p a c i t i e s o f t h e B e n z o y l and t h e M e t h y l E s t e r Groups Determined f r o m Compounds 65a and 65b. The a s s i g n m e n t was b a s e d on NMR c h e m i c a l s h i f t d a t a . I t was n o t i c e d t h a t the c h e m i c a l s h i f t s o f and Hg^^ on the two b e n z o s e m i b u l l v a l e n e s were d i s t i n c t l y d i f f e r e n t . One group has a s t r o n g e r d e s h i e l d i n g e f f e c t on the n e i g h b o r i n g methine p r o t o n (H2a o r Hg^j) t h a n the o t h e r . T h e r e f o r e , the d e t e r m i n a t i o n o f the r e l a t i v e d e s h i e l d i n g s t r e n g t h between the b e n z o y l and the e s t e r w i l l p r o v i d e the answer. A model s e t o f compounds (65a and 65b, F i g u r e 2.06) was u n c o v e r e d from a l i t e r a t u r e s e a r c h t h e m a g n etic e n v i r o n m e n t o f t h e s e compounds i s v e r y s i m i l a r t o the s u b s t i t u t e d r e g i o n o f t h e benzosemi-b u l l v a l e n e s . The r e p o r t e d NMR o f t h e s e compounds r e v e a l t h a t the b e n z o y l group has s t r o n g e r d e s h i e l d i n g p r o p e r t i e s ; the m e t h y l a d j a c e n t t o the b e n z o y l on 65a i s 0.10 ppm d o w n f i e l d o f t h e m e t h y l a d j a c e n t t o the e s t e r on 65b. Based on t h i s r e s u l t , the s t r u c t u r e s compounds 43d and 43e were a s s i g n e d as shown i n F i g u r e 2.05. A n o t h e r i n t e r e s t i n g p r o b l e m w i t h the c h a r a c t e r i z a t i o n o f 1,2-d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s i s t h e assignment o f t h e arid C2]-, p r o t o n s . R e c a l l t h a t b o t h s i g n a l s g i v e r i s e t o one p r o t o n t r i p l e t s and have s i m i l a r b u t n o t i d e n t i c a l c h e m i c a l s h i f t s . T h i s p r o b l e m i s s o l v e d by the use o f a l a n t h a n i d e s h i f t r e a g e n t ( E u ( h f c ) 3 ) . I t was r e a s o n e d from a s i m i l a r s t u d y w i t h c y c l o o c t a t e t r a e n e d e r i v a t i v e s ^ - ^ t h a t the benzosemi-b u l l v a l e n e w o u l d complex t o the s h i f t r e a g e n t as shown i n F i g u r e 2.07. The C2a and p r o t o n s a r e v e r y c l o s e t o each o t h e r and have s i m i l a r o r i e n t a t i o n s . S i n c e the € 2 3 p r o t o n i s n e a r e r t o the s i t e o f c o m p l e x a t i o n . F i g u r e 2.07 C o m p l e x a t i o n o f 1 , 2 - D i s u b s t i t u t e d B e n z o s e m i b u l l v a l e n e s t o E u ( h f c ) 3 . i t s h o u l d be more s e n s i t i v e t o a d d i t i o n s o f t h e s h i f t r e a g e n t . From s u c c e s s i v e a d d i t i o n s o f t h e s h i f t r e a g e n t t o a maximum o f 30 mole %, the changes i n c h e m i c a l s h i f t s o f each s i g n a l were r e c o r d e d . These c h e m i c a l s h i f t changes (Au) a r e p l o t t e d f o r b o t h compounds, 43d and 43e, i n F i g u r e 2.08. F i g u r e 2.08 P l o t s o f Change i n C h e m i c a l S h i f t (Au) A g a i n s t t h e Mole % o f E u ( h f c ) 3 Added f o r Compounds 43d and 43e. The s l o p e s on the graphs o f F i g u r e 2.08 show l a r g e d i f f e r e n c e s i n s e n s i t i v i t y t o t h e s h i f t r e a g e n t . T h i s a l l o w s f o r t h e a s s i g n m e n t o f t h e more s e n s i t i v e t r i p l e t t o and t h e l e s s s e n s i t i v e t r i p l e t t o ii2h- '^^^ c o n f i d e n c e i n t h i s a s s i gnment i s s u p p o r t e d by t h e p o s i t i v e c o r r e l a t i o n between the o t h e r s l o p e s t o t h e i r e s t a b l i s h e d a s s i g n m e n t s . C o n s e q u e n t l y , the s i g n a l s a r e more s h i e l d e d t h a n the H2b s i g n a l s i n t h e s e 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s . D. C h a r a c t e r i z a t i o n o f O t h e r D i s u b s t i t u t e d B e n z o s e m i b u l l v a l e n e s . The NMR s p e c t r u m and e x p a n s i o n o f m e t h y l 6 c - b e n z o y l - 2 a , 2 b - d i h y d r o -benzo [a] c y c l o p r o p a [ c d ] p e n t a l e n e - 6 b - c a r b o x y l a t e ( 4 3 f ) a r e shown i n F i g u r e 2.09. The s e m i b u l l v a l e n e s k e l e t o n o f 6 b , 6 c - d i s u b s t i t u t e d benzo-s e m i b u l l v a l e n e 43f a l s o has an i n f o r m a t i v e p a t t e r n o f s i g n a l s . The f o l l o w i n g s i g n a l s a r e d e s c r i b e d g o i n g from most s h i e l d e d t o l e a s t s h i e l d e d i n p r o g r e s s i v e o r d e r . The H2a d o u b l e t o f d o u b l e t s ( J = 8,3 Hz) i s t h e most s h i e l d e d f o l l o w e d c l o s e l y by the H2b d o u b l e t ( J = 8 H z ) . R e s o n a t i n g f u r t h e r d o w n f i e l d i s the v i n y l H2 d o u b l e t o f d o u b l e t s ( J = 5,3 Hz) and t h e v i n y l B.-^ d o u b l e t ( J = 5 Hz) . The a r o m a t i c p r o t o n s r e s o n a t e above 7 ppm. These a s s i g n m e n t s were a l s o s u p p o r t e d by d e c o u p l i n g e x p e r i m e n t s . A l t h o u g h , the s p e c t r o s c o p i c e v i d e n c e from NMR l e d t o the a s s i g n m e n t o f a 6 b , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s k e l e t o n , the u n c e r t a i n t y as t o whether the p o s i t i o n o f the s u b s t i t u e n t s a r e c o r r e c t l y a s s i g n e d o r r e v e r s e d s t i l l r emained. Owing t o the c r y s t a l l i n e n a t u r e o f the m o l e c u l e , an X - r a y a n a l y s i s was p e r f o r m e d by Dr. P o k k u l u r i t o c o n f i r m the p o s i t i o n o f the s u b s t i t u e n t s ; an ORTEP^^ d i a g r a m o f t h e s t r u c t u r e i s shown i n F i g u r e 2.10. F i g u r e 2.09 NMR Spectrum and E x p a n s i o n o f M e t h y l 6 c - B e n z o y l - 2 a , 2 b - d i h y d b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 6 b - c a r b o x y l a t e ( 4 3 f ) i n CDClo. F i g u r e 2.10 S t e r e o d l a g r a m o f M e t h y l 6 c - B e n z o y l - 2 a , 2 b - d i h y d r o b e n z o [ a ] c y c l o -p r o p a [ c d ] p e n t a l e n e - 6 b - c a r b o x y l a t e ( 4 3 f ) from X - r a y A n a l y s i s . The NMR s p e c t r u m i n F i g u r e 2.11 i s t h a t o f m e t h y l 6 c - b e n z o y l -2 a , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 2 b - c a r b o x y l a t e ( 4 3 g ) . The s e m i b u l l v a l e n e r i n g system shows ^2a most s h i e l d e d s i g n a l a p p e a r i n g as a d o u b l e t ( J - 3 Hz) ; n e x t i s the Hg^, d o u b l e t ( J - 2 Hz) . The o t h e r two s i g n a l s a r e f u r t h e r d o w n f i e l d . The p r o t o n on C 2 i s a d o u b l e t o f d o u b l e t s ( J = 5,3 H z ) ; T h i s i s s l i g h t l y u p f i e l d o f the d o u b l e t o f d o u b l e t s ( J = 5,2 Hz) from the Ci p r o t o n . A g a i n , the a r o m a t i c s r e s o n a t e above 7 ppm. Through an u n d e r s t a n d i n g o f the [1,3] p h o t o c h e m i c a l s h i f t s p r e s e n t i n many o f t h e s e b e n z o s e m i b u l l v a l e n e s y s tems, and the f a c t t h a t t h i s compound (43g) i s a p r o d u c t o f compound 4 3 f , the r e l a t i v e p o s i t i o n s o f the e s t e r and the b e n z o y l groups c a n be a s s i g n e d w i t h o u t a n o t h e r X - r a y a n a l y s i s . ' M I I I I I I I I I I ' • I I I I I I I I I I I I I ' I I I I I I I ' • ' ' I • ' ' ' I I I ' I — ~ i 1 - 1 r -5 , 8 5 . 6 1.1 5 . 3 5 0 * B - î B • ^ ppm F i g u r e 2.11 a) NMR S p e c t r a l E x p a n s i o n o f M e t h y l 6 c - B e n z o y l - 2 a , 6 b - d i h y d r o -b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 2 b - c a r b o x y l a t e (43g) i n C D C I 3 . b) D e c o u p l i n g a t 4.52 ppm. From e x a m i n a t i o n o f the many d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s p e c t r a i n t h i s s e c t i o n , t h e s u b s t i t u e n t l o c a t i o n s g i v e r i s e t o c h a r a c t e r i s t i c p a t t e r n s o f s i g n a l s i n a c l e a r r e g i o n o f t h e NMR spectrum. A l t h o u g h t h e s u b s t i t u e n t s may be d i f f e r e n t , t he l o c a t i o n o f t h e s e s i g n a l s and t h e i r c o u p l i n g c o n s t a n t s s t a y r e l a t i v e l y unchanged. T h i s p r o v i d e s a v i t a l a s s e t i n the s t u d y o f the b e n z o b a r r e l e n e s y stems, as NMR c a n be u s e d t o deduce the s t r u c t u r e o f the p h o t o p r o d u c t s e a s i l y . As an e x t e n s i o n , NMR i s u s e d i n many s t u d i e s f o r d i r e c t l y d e t e r m i n i n g p h o t o p r o d u c t r a t i o s . The s i n g l e p r o t o n s i g n a l s o f the d i f f e r e n t s e m i b u l l v a l e n e compounds r a r e l y s u f f e r from o v e r l a p w i t h each o t h e r ; t h e r e f o r e , i t i s p o s s i b l e t o o b t a i n a c l e a r i n t e g r a t i o n o f t h e s i g n a l s . Q u a n t i t a t i v e a n a l y s i s by NMR has been w e l l e s t a b l i s h e d t o be v e r y a c c u r a t e w i t h p r o j e c t e d i n t e g r a t i o n e r r o r s o f + 3% on b a s e l i n e - s e p a r a t e d s i g n a l s . •'-'^^ T h i s a s p e c t p r o v e d t o be q u i t e e f f e c t i v e because o f the i n h e r e n t i n s t a b i l i t y t h a t many o f t h e s e b e n z o s e m i b u l l v a l e n e s have t o t h e h i g h t e m p e r a t u r e GC columns. PART I I I . PHOTOCHEMISTRY OF SYMMETRICALLY DISUBSTITUTED BENZOBARRELENES A. P h o t o c h e m i s t r y o f D i m e t h y l 1 , 4 - D i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 -d i c a r b o x y l a t e ( 2 9 ) . The s o l u t i o n p h o t o c h e m i s t r y o f the t i t l e compound, d i m e t h y l 1 , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l a t e ( 2 9 ) , was f i r s t i n v e s t i g a t e d by G r o v e n s t e i n , C a m p b e l l , and Shibat a ^ * ^ o v e r 20 y e a r s ago. They d i s c o v e r e d t h a t d i r e c t p h o t o l y s i s o f b e n z o b a r r e l e n e 29 g i v e s complete c o n v e r s i o n o f s t a r t i n g m a t e r i a l t o d i m e t h y l b e n z o c y c l o -o c t a t e t r a e n e - 7 , 8 - d i c a r b o x y l a t e (29c) and t h a t a c e t o n e - s e n s i t i z e d p h o t o l y s i s g i v e s t h r e e u n i d e n t i f i e d p r o d u c t s i n a 5 : 3 : 2 r a t i o . Three Products 5 : 3 : 2 F i g u r e 3.01 P h o t o c h e m i s t r y o f Compound 29 R e p o r t e d by G r o v e n s t e i n e t a l . i n 1969. I n 1975, Bender and B r o o k s ^ ^ r e i n v e s t i g a t e d t h i s compound i n o r d e r t o d e t e r m i n e the mechanism o f c y c l o o c t a t e t r a e n e 29c f o r m a t i o n . Shown i n F i g u r e 3.02 a r e two p o s s i b l e r o u t e s , b o t h i n i t i a t e from a p h o t o c h e m i c a l [2+2] i n t r a m o l e c u l a r c y c l o a d d i t i o n f o l l o w e d by a t h e r m a l r i n g o p e n i n g . However, the r o u t e s d i f f e r w i t h r e s p e c t t o the doubl e bonds i n v o l v e d . S t a r t i n g from 2 - d e u t e r i o n a p h t h a l e n e , t h e y p r e p a r e d b e n z o b a r r e l e n e 29 w i t h d e u t e r i u m l a b e l s a t the Cy and Cg p o s i t i o n s . P h o t o l y s i s o f t h i s d e u t e r a t e d b e n z o b a r r e l e n e gave b e n z o c y c l o o c t a t e t r a e n e 29c w i t h l a b e l s s o l e l y a t the C 2 and Cg p o s i t i o n s , c o r r e s p o n d i n g t o the i n i t i a l v i n y l - v i n y l b r i d g i n g r o u t e . No m e n t i o n was made o f the a c e t o n e - s e n s i t i z e d p h o t o r e a c t i o n . not observed F i g u r e 3.02 M e c h a n i s t i c Study f o r B e n z o c y c l o o c t a t e t r a e n e 29c F o r m a t i o n P e r f o r m e d by Bender and Brooks®^ i n 1975. I n o r d e r t o e x t e n d t h i s i n v e s t i g a t i o n t o the s o l i d s t a t e , the s o l u t i o n p h o t o c h e m i s t r y must be f u l l y u n d e r s t o o d f i r s t . I n a c c o r d a n c e w i t h t h e p r e v i o u s s t u d i e s , d i r e c t p h o t o l y s i s (A > 290 nm) was f o u n d t o y i e l d b e n z o c y c l o o c t a t e t r a e n e 29c as t h e o n l y p r o d u c t . However, benzophenone s e n s i t i z a t i o n , where the benzophenone a b s o r b s e s s e n t i a l l y a l l the i n c i d e n t r a d i a t i o n (A > 330 nm), g i v e s complete c o n v e r s i o n t o a 78% y i e l d o f a d i f f e r e n t p r o d u c t . T h i s was s u b s e q u e n t l y c h a r a c t e r i z e d as d i m e t h y l 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 2 a , 6 c - d i c a r b o x y l a t e 29a. T h i s a s s i g n m e n t i s b a s e d m a i n l y on the NMR s p e c t r a l d a t a ( F i g u r e s 2.02 and 2.03) . B e n z o s e m i b u l l v a l e n e 29a was p h o t o l y z e d d i r e c t l y and under a c e t o n e s e n s i t i z a t i o n t o g i v e a n o t h e r p r o d u c t a t a maximum c o n v e r s i o n o f 52% by GC. T h i s compound was d e t e r m i n e d , a f t e r c h r o m a t o g r a p h i c s e p a r a t i o n , t o be d i m e t h y l 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o [ c d ] p e n t a l e n e -1 , 6 c - d i c a r b o x y l a t e 29b w i t h the NMR s p e c t r u m shown i n F i g u r e 2.04. F i g u r e 3.03 Complete P h o t o c h e m i s t r y o f B e n z o b a r r e l e n e 29. B e i n g aware o f the p o s s i b i l i t y o f s e c o n d a r y p h o t o p r o d u c t s , t h e s o l u t i o n phase p h o t o c h e m i s t r y o f b e n z o c y c l o o c t a t e t r a e n e 29c was a l s o i n v e s t i g a t e d . D i r e c t p h o t o l y s i s o f compound 29c l e d t o no d e t e c t a b l e p h o t o p r o d u c t s by GC. On the o t h e r hand, a c e t o n e - s e n s i t i z e d p h o t o l y s i s o f compound 29c g i v e s , a f t e r work-up, 71% o f a n o t h e r p r o d u c t . Based m a i n l y on NMR d a t a , t h i s compound was i d e n t i f i e d as d i m e t h y l 2b,6b-d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 2 , 6 c ( 2 a H ) - d i c a r b o x y l a t e (29e) . Racemic b e n z o s e m i b u l l v a l e n e 29a i s s u g g e s t e d t o a r i s e v i a a t r i p l e t - m e d i a t e d di - 7 r-methane p h o t o r e a r r a n g e m e n t . The s e l e c t e d p a t h i s t h r o u g h an i n i t i a l v i n y l - v i n y l b o n d i n g f o l l o w e d by c l e a v a g e o f bond a ( F i g u r e 3.04). R i n g c l o s u r e o f t h i s s e c o n d b i r a d i c a l p r o d u c e s the o b s e r v e d s p e c i e s . R e f l e c t i n g on the o t h e r di-jr-methane r e a r r a n g e m e n t p o s s i b i l i t i e s o f F i g u r e 0.20, o n l y t h e d e s c r i b e d r o u t e l e a d s t o compound 29a. I t can be s u g g e s t e d t h a t bond f o r m a t i o n a c r o s s t h e two v i n y l s i s e n e r g e t i c a l l y l e s s demanding t h a n the d i s r u p t i o n o f a r o m a t i c i t y from i n i t i a l b e n z o - v i n y l b o n d i n g . W i t h r e s p e c t t o the second b o n d - b r e a k i n g s t e p , c l e a v a g e o f bond a g i v e s a 1 , 3 - b i r a d i c a l w i t h one r a d i c a l t h a t c a n be c o m f o r t a b l y d e l o c a l i z e d o n t o an e s t e r c a r b o n y l and the o t h e r onto the benzene r i n g . On the o t h e r hand, c l e a v a g e o f bond b g i v e s a 1 , 3 - b i r a d i c a l w i t h one r a d i c a l t h a t can be d e l o c a l i z e d o n t o the benzene r i n g b u t the o t h e r r a d i c a l s i t s on a methylene p o s i t i o n w i t h o u t any resonance s t a b i l i z a t i o n . As a r e s u l t , bond c l e a v a g e o f a t o form the more s t a b l e 1 , 3 - b i r a d i c a l i s f a v o r e d . T h i s l e a d s t o b e n z o s e m i b u l l v a l e n e 29a as the o n l y o b s e r v e d p r o d u c t . I n a d d i t i o n , p h o t o p r o d u c t s o f t h i s n a t u r e from s i m i l a r b e n z o b a r r e l e n e s a r e known. F i g u r e 3.04 Mechanism o f B e n z o s e m i b u l l v a l e n e 29a and 29b F o r m a t i o n . B e n z o s e m i b u l l v a l e n e 29b i s s u g g e s t e d t o come from a p h o t o c h e m i c a l [1,3] s h i f t o f 29a. The C2a-C6c ^o^^à o f 29a i s c l e a v e d and r e f o r m e d between the C^-Cç^ç. p o s i t i o n s . The f o r m a t i o n o f p h o t o p r o d u c t 29b a t a l i m i t i n g c o n v e r s i o n o f 52% l e d t o the s u s p i c i o n o f an i n t e r e s t i n g p h o t o s t a t i o n a r y s t a t e . Pure benzosemi-b u l l v a l e n e 29b was p h o t o l y z e d d i r e c t l y i n a c e t o n i t r i l e (A > 260 nm) as w e l l as from s e n s i t i z a t i o n by a c e t o n e (A > 290 nm) and benzene (A > 260 nm); a l l t h r e e p h o t o l y s e s gave i s o m e r 29a, and once a g a i n , a l i m i t i n g c o n v e r s i o n was o b t a i n e d . However, the i n t e r c o n v e r s i o n was n o t i c e a b l y s l o w e r i n a c e t o n i t r i l e t h a n i n the o t h e r two s o l v e n t s . The p h o t o s t a t i o n a r y s t a t e r a t i o s i n ace t o n e and benzene were i n v e s t i g a t e d w i t h a s e r i e s o f a n a l y t i c a l p h o t o l y s e s . Degassed samples o f pur e compound 29a, compound 29b, and m i x t u r e s o f the two were p h o t o l y z e d . The r e a c t i o n s were m o n i t o r e d by GC t o a s t e a d y s t a t e component r a t i o . These r a t i o s were c a l i b r a t e d u s i n g an i n t e r n a l s t a n d a r d ( o c t a d e c a n e ) . A f t e r 13 r u n s , the a r r i v e d r a t i o o f 29a : 29b i n benzene i s 7 + 1 : 3 + 1^^ and a f t e r t h r e e r u n s , the r a t i o o f 29a : 29b i n acetone i s 8 : 2. T h i s p h o t o r e a c t i o n i s v e r y l i k e l y t r i p l e t - m e d i a t e d . W i t h a c e t o n e (T]^ = 79-82 k c a l / m o l e ) o r benzene (Ti = 84.3 k c a l / m o l e ) s e n s i t i z a t i o n , ^ 5 ^he r e a c t i o n p r o c e e d s f a s t e r t h a n from d i r e c t p h o t o l y s i s i n a c e t o n i t r i l e . However, Benzophenone (T^^ = 69 k c a l / m o l e ) i s i n e f f e c t i v e as a s e n s i t i z e r . A c c o r d i n g t o t h e l i t e r a t u r e , m o s t p h o t o c h e m i c a l [1,3] s h i f t s o c c u r t h r o u g h t h e s i n g l e t e x c i t e d s t a t e , however, some [1,3] s h i f t s have been r e p o r t e d t o med i a t e t h r o u g h the T 2 e x c i t e d s t a t e . The o b s e r v a t i o n t h a t t h i s r e a c t i o n i s enhanced upon use o f h i g h e r energy s e n s i t i z e r s and r e t a r d e d w i t h l o w e r energy s e n s i t i z e r s s u g g e s t s a T 2 m e d i a t e d p r o c e s s . hv F i g u r e 3.05 Mechanism o f B e n z o s e m i b u l l v a l e n e 29e F o r m a t i o n from Benzo-c y c l o o c t a t e t r a e n e 29c. B e n z o s e m i b u l l v a l e n e 29e i s b e l i e v e d t o be a t e r t i a r y p h o t o p r o d u c t o f b e n z o b a r r e l e n e 29. Upon d i r e c t e x c i t a t i o n o f t h e b e n z o c y c l o -o c t a t e t r a e n e p h o t o p r o d u c t 29c, c y c l o l s u t e n e 29d i s d e t e c t e d . Compound 29d i s s u g g e s t e d t o come from a [2+2] i n t r a m o l e c u l a r c y c l o a d d i t i o n , and upon t r i p l e t s e n s i t i z a t i o n o f t h i s compound, p h o t o p r o d u c t 29e c a n be a r r i v e d a t from a di-7r-methane r e a r r a n g e m e n t ( F i g u r e 3.05). The sequence o f r e a c t i o n s t o form 29e i s n o t a l l t o g e t h e r unknown; Bender^^ i s a c t i v e l y i n v e s t i g a t i n g t h i s p r o c e s s w i t h d i m e t h y l and cyano s u b s t i t u t e d c y c l o o c t a t e t r a e n e s . I n t e r e s t i n g l y , t h e c y c l o b u t e n e 29d i s t h e r m a l l y u n s t a b l e and r e a d i l y r e v e r t s back t o c y c l o o c t a t e t r a e n e 29c, thus a c c o u n t i n g f o r the i n a b i l i t y t o d e t e c t i t s f o r m a t i o n from GC m o n i t o r i n g . However, when compound 29c was p h o t o l y z e d and d i r e c t l y a n a l y z e d by NMR, the spectrum ( F i g u r e 3.06) showed t h e f o r m a t i o n o f a new s i g n a l p a t t e r n c o r r e s p o n d i n g t o the c y c l o b u t e n e . ^ ^ aromatic 29c 29c PPM 29d 29d 29d 7.0 6.0 CO2CH3 CO2CH3 2M 29d — I — 5 0 2Sâ 2M 2§E 4 0 F i g u r e 3.06 NMR Spectrum o f Compound 29c R e a c t i o n M i x t u r e Showing S i g n a l s o f C y c l o b u t e n e 29d. G r o v e n s t e i n ' s p h o t o l y s i s ^ ^ o f b e n z o b a r r e l e n e 29 i n ace t o n e was r e p e a t e d i n l i g h t o f the t h r e e i d e n t i f i e d p h o t o p r o d u c t s (29a, 29b, and 2 9 e ) . The r e a c t i o n (0.013 M) was m o n i t o r e d by GC f o r the f o r m a t i o n o f the t h r e e p h o t o p r o d u c t s . A t low c o n v e r s i o n s , compounds 29a and 29e are formed i n e q u a l amounts. As c o n v e r s i o n i n c r e a s e s the s i g n a l o f 29b s t e a d i l y r o s e . C o n v e r s e l y , the p h o t o i n s t a b i l i t y o f 29e slowed i t s f o r m a t i o n a t h i g h e r c o n v e r s i o n s . The p h o t o l y s i s was d i s c o n t i n u e d a f t e r a l l b e n z o b a r r e l e n e 29 had r e a c t e d and t h e f i n a l r a t i o o f 29a : 29e : 29b was 65 : 25 : 9. I t was a l s o n o t i c e d from a s e r i e s o f s i m i l a r a n a l y t i c a l p h o t o l y s e s t h a t the r a t i o s v a r i e d n o t o n l y w i t h c o n v e r s i o n b u t w i t h the c o n c e n t r a t i o n o f s t a r t i n g m a t e r i a l . R e a s o n i n g t h a t b e n z o s e m i b u l l v a l e n e 29e comes from an i n i t i a l s i n g l e t p r o c e s s and the o t h e r s from t r i p l e t p r o c e s s e s , h i g h e r c o n c e n t r a t i o n s o f s t a r t i n g m a t e r i a l w i l l a l l o w f o r more d i r e c t a b s o r p t i o n o f i n c i d e n t r a d i a t i o n by t h e s u b s t r a t e , g i v i n g more s i n g l e t -m e d i a t e d compound 29e. B e n z o b a r r e l e n e 29 i s a l m o s t t r a n s p a r e n t t o w a v e l e n g t h s above 330 nm; as a r e s u l t , benzophenone s e n s i t i z a t i o n u s i n g t h e s e l o n g w a v e l e n g t h s g i v e s no compound 29e. C r y s t a l s o f 29 were p h o t o l y z e d w i t h a medium p r e s s u r e mercury lamp (A > 290 nm) and a n i t r o g e n l a s e r (A = 337 nm). B e n z o c y c l o o c t a -t e t r a e n e 29c i s the o n l y p r o d u c t formed a t a maximum c o n v e r s i o n o f 30% i n b o t h c a s e s . E x t ended p h o t o l y s i s r e s u l t s i n y e l l o w i n g and s u r f a c e m e l t i n g o f t h e c r y s t a l s . The f o r m a t i o n o f b e n z o c y c l o o c t a t e t r a e n e 29c d i s p l a y s c r y s t a l l i n e s t a t e r e a c t i v i t y ; however, t h i s i s the same p r o d u c t seen i n d i r e c t s o l u t i o n p h o t o l y s e s , v i a a s i n g l e t - m e d i a t e d [2+2] c y c l o a d d i t i o n . The c e n t e r - t o - c e n t e r d i s t a n c e o f t h e two v i n y l groups i s 2.46 Â from X - r a y c r y s t a l a n a l y s i s ^ ^ and t h i s i s w e l l w i t h i n t h e e s t a b l i s h e d l i m i t i n g d i s t a n c e o f 4.1 Â f o r i n t e r m o l e c u l a r [2+2] c y c l o a d d i t i o n s . S o l u t i o n i n t r a m o l e c u l a r [2+2] c y c l o a d d i t i o n s f o r a c y c l i c n o n - c o n j u g a t e d d i e n e s have a l i m i t i n g d o u b l e bond s e p a r a t i o n t o 1 , 7 - d i e n e s . G r e a t e r d i e n e s e p a r a t i o n s r e s u l t i n o n l y c i s / t r a n s i s o m e r i z a t i o n . B. P h o t o c h e m i s t r y o f 1 , 4 - D i h y d r o - l , 4 - e t h e n o n a p h t h a I e n e - 2 , 3 - d i c a r b o x y I i c A c i d ( 4 0 ) . D i r e c t s o l u t i o n p h o t o l y s i s o f d i a c i d 40 g i v e s complete c o n v e r s i o n t o b e n z o c y c l o o c t a t e t r a e n e - ? , 8 - d i c a r b o x y l i c a c i d (40c) as the o n l y p r o d u c t . However, t h i s d i a c i d p h o t o p r o d u c t r e a d i l y l o s e s w a t e r i n s o l u t i o n a t room t e m p e r a t u r e t o g i v e the c o r r e s p o n d i n g a n h y d r i d e ^ ^ (41d, F i g u r e 3.07). F i g u r e 3.07 P h o t o p r o d u c t s from 1 , 4 - D i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 -d i c a r b o x y l l c A c i d ( 4 0 ) . D i a c i d s a r e t o o p o l a r t o pass t h r o u g h t h e GC columns i n t h e l a b o r a t o r y . T h e r e f o r e , t h e r e a c t i o n m i x t u r e s were m o n i t o r e d by NMR f o r the l o s s o f s t a r t i n g m a t e r i a l . The r e a c t i o n m i x t u r e was c o n c e n t r a t e d under m i l d t e m p e r a t u r e s (T < 60 °C, t o reduc e a n h y d r i d e f o r m a t i o n ) and t h e two c y c l o o c t a t e t r a e n e s s e p a r a t e d by r e c r y s t a l l i z a t i o n from e t h y l a c e t a t e . D i a c i d 40c forms c l e a r y e l l o w n e e d l e s and a n h y d r i d e 41d forms red-brown r o d s . The d e h y d r a t i o n o f d i a c i d 40c c a n be e a s i l y d e t e c t e d , as the s o l u t i o n changes c o l o r from y e l l o w t o red-brown. A n h y d r i d e 41d was s y n t h e s i z e d t h r o u g h d i a c i d 40c by G r o v e n s t e i n ^ ^ i n e f f o r t t o c h a r a c t e r i z e d i e s t e r 29c. However, o n l y the r e s u l t s o f a c a r b o n - h y d r o g e n a n a l y s i s was p r o v i d e d i n h i s r e p o r t . The two c y c l o o c t a t e t r a e n e s were s u b s e q u e n t l y c h a r a c t e r i z e d by s p e c t r o s c o p i c t e c h n i q u e s . An i n t e r e s t i n g f e a t u r e o f t h i s a n h y d r i d e f o r m a t i o n was n o t i c e d d u r i n g the m e l t i n g p o i n t d e t e r m i n a t i o n o f the d i a c i d 40c. H e a t i n g ( r a t e = 1 °C/min) t o 122 °C r e s u l t s i n t h e f o r m a t i o n o f brown s p o t s i n the y e l l o w c r y s t a l . A t 130 °C, the c r y s t a l becomes c o m p l e t e l y red-brown and b u l g i n g i s seen on t h e s u r f a c e . No f u r t h e r change i s seen u n t i l t he c r y s t a l m e l t s a t 210 °C (•"Panhydride = 210-212 °C) . T h i s i s a t h e r m a l s o l i d s t a t e r e a c t i o n , and a l t h o u g h r e a c t i o n s o f t h i s n a t u r e a r e known, t h e y a r e r a t h e r uncommon. P a u l and Curtin^-*"^ p r o p o s e d i n a r e v i e w o f t h e r m a l o r g a n i c s o l i d s t a t e r e a c t i o n s t h a t g e n e r a l l y , r e a c t i o n s w h i c h o c c u r i n i n e r t s o l v e n t a t a r e a s o n a b l e r a t e 60-100 °C below the m e l t i n g p o i n t o f the r e a c t a n t , c a n be made t o o c c u r i n t h e s o l i d . T h i s p r o p o s a l h o l d s t r u e f o r the above d e h y d r a t i o n . B e n z o p h e n o n e - s e n s i t i z e d p h o t o l y s i s (A > 330 nm) o f d i a c i d 40 l e d t o the f o r m a t i o n o f two p h o t o p r o d u c t s . A g a i n t h e r e a c t i o n s were m o n i t o r e d by NMR f o r t h e l o s s o f s t a r t i n g m a t e r i a l . These two p r o d u c t s were s u b s e q u e n t l y i d e n t i f i e d as 2 a , 2 b , 6 b , 6 c - t e t r a h y d r o b e n z o [ a ] c y c l o -p r o p a [ c d ] p e n t a l e n e - l , 2 - d i c a r b o x y l i c a c i d (40b) and 2 b , 6 b - d i h y d r o b e n z o -[ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 2 a , 5 c - d i c a r b o x y l i c a c i d (40a, F i g u r e 3.08) i n a r a t i o o f 92 : 8, r e s p e c t i v e l y . Owing t o t h e i n a b i l i t y o f c a r b o x y l i c a c i d s t o e l u t e from s i l i c a g e l columns, t h e m i x t u r e was t r e a t e d w i t h diazomethane and the r e s u l t i n g d i m e t h y l e s t e r s (29a and 2 9 f ) s e p a r a t e d and c h a r a c t e r i z e d . The NMR spe c t r u m o f d i m e t h y l e s t e r 29a i s i d e n t i c a l t o the r e p o r t e d r e s u l t s ( F i g u r e 2.02). L i k e w i s e , t h e s p e c t r o -s c o p i c d a t a f o r b e n z o s e m i b u l l v a l e n e 29f i s c o n s i s t e n t w i t h the d a t a f o r t h i s compound o r i g i n a l l y r e p o r t e d by G r o v e n s t e i n e t a l . ^ * - * i n 1969. Once s e p a r a t e d , t h e d i e s t e r s were h y d r o l y z e d under b a s i c c o n d i t i o n s t o g i v e the c o r r e s p o n d i n g pure d i a c i d s f o r c h a r a c t e r i z a t i o n . The NMR s p e c t r a f o r compounds 40a and 40b a r e shown i n F i g u r e s 2.02 and 2.05, r e s p e c t i v e l y . W i t h r e g a r d t o the mechanism o f b e n z o c y c l o o c t a t e t r a e n e f o r m a t i o n , an e x p e r i m e n t s i m i l a r t o t h a t o f Benders^-^ was p e r f o r m e d . B e n z o b a r r e l e n e d i a c i d 40 w i t h d e u t e r i u m l a b e l s on the C-^, C 4 , C 5 , and C 3 p o s i t i o n s was p h o t o l y z e d . S i m i l a r t o the s i t u a t i o n i n F i g u r e 3.02, t h e r e a r e two p o s s i b l e r o u t e s t o t h e f o r m a t i o n o f b e n z o c y c l o o c t a t e t r a e n e 40c. Owing t o the f a c i l e i n t e r c o n v e r s i o n o f d i a c i d 40c t o the a n h y d r i d e 41d, t h i s a n h y d r i d e was i s o l a t e d and r e c r y s t a l l i z e d f o r NMR a n a l y s i s . The r e s u l t i n g s p e c t r u m ( F i g u r e 3.08) showed d e u t e r i u m l a b e l s i n the p o s i t i o n s s u p p o r t i n g o n l y t h e i n i t i a l v i n y l - v i n y l b o n d i n g r o u t e . Assignment o f t h e v i n y l p r o t o n s were b a s e d on a s h i f t r e a g e n t s t u d y p e r f o r m e d by Bender^-^ on t h e d i m e t h y l a n a l o g ( 2 9 c ) . a) 4H 1 5+10 1+4 2+3 2H J 6+9 2H v J / L 6.5 E l 1 10 9 O DMSO 5.» .,5 ,:, 5., J , , , , , , ^ , ^ ppm b) 2H 3H{1D) 2H _1 /V_ • 4L. , o ,Mn / O 1/4D DEUTERATED 41d DMSO ' ••• ' 5 7.1 e.1 I t s.s 4,5 * C Î 5 Î -ppm F i g u r e 3.08 P r o t o n NMR s p e c t r a o f a) Compound 41d i n DMSO-dg. b) D e u t e r i u m L a b e l l e d 41d i n DMSO-dg. B e n z o s e m i b u l l v a l e n e 40a ( F i g u r e 3.09) i s s u g g e s t e d t o come from a di-7r-methane rearrangement w i t h i n i t i a l v i n y l - v i n y l b o n d i n g t o g i v e a c y c l o p r o p y l b i r a d i c a l ( p a t h i ) . T h i s i s f o l l o w e d by c l e a v a g e o f bond a t o g i v e the p r o d u c t . T h i s mechanism i s the o n l y di - T T-methane r o u t e t o 2 a , 6 c - d i s u b s t i t u t i o n ( F i g u r e 0.20) o f b e n z o s e m i b u l l v a l e n e . S u p p o r t a l s o comes from s i m i l a r r e s u l t s d i s c u s s e d w i t h the d i m e t h y l a n a l o g s e c t i o n (PART I I I A ) . 40b ( heavy circled carbons denote locations of deuterium label ) F i g u r e 3.09 Mechanisms t o B e n z o s e m i b u l l v a l e n e s 40a and 40b. B e n z o s e m i b u l l v a l e n e 40b, however, has two p o s s i b l e di-w-methane r o u t e s t o i t s f o r m a t i o n . The f i r s t p o s s i b i l i t y i s t h r o u g h i n i t i a l v i n y l - v i n y l b o n d i n g ( p a t h i , F i g u r e 3.09), f o l l o w e d by r a d i c a l c l e a v a g e o f bond b, and b i r a d i c a l r e c o m b i n a t i o n g i v e s compound 40b. The o t h e r r o u t e i s from i n i t i a l b e n z o - v i n y l b o n d i n g ( p a t h i i ) f o l l o w e d by the r e g e n e r a t i o n o f a r o m a t i c i t y i n the s e c o n d s t e p ; subsequent b i r a d i c a l r i n g c l o s u r e a l s o g i v e s p r o d u c t 40b. I n o r d e r t o d e t e r m i n e w h i c h p a t h i s t a k e n , b e n z o b a r r e l e n e 40 was d e u t e r i u m l a b e l l e d i n t h e Ci, C 4 , C 5 , and Cg p o s i t i o n s ( F i g u r e 3.09) and p h o t o l y z e d under benzophenone s e n s i t i z a t i o n . NMR a n a l y s i s ( F i g u r e 3.10a) o f t h e r e s u l t i n g m i x t u r e shows the d i m i n u t i o n o f t h e H213 (0.75H) s i g n a l s u p p o r t i n g p a t h i as the e x c l u s i v e r o u t e t o compound 40b. T h i s i s r e a s o n a b l e as the d i s r u p t i o n o f a r o m a t i c i t y i n p a t h i i w o u l d r e q u i r e much more energy. n " I 1 1 1 1 . 1 , r-4.0 3.8 3.6 3.4 3.2 3.0 ppm F i g u r e 3.10a R e a c t i o n M i x t u r e P r o t o n NMR S p e c t r a from Benzophenone S e n s i t i z a t i o n o f D e u t e r a t e d Compound 40 i n DMSO-dg. I t i s i n t e r e s t i n g t o n o t e t h e i n c r e a s e i n 1 , 2 - d i s u b s t i t u t e d benzo-s e m i b u l l v a l e n e d i a c i d f o r m a t i o n compared t o i t s 2 a , 6 c - d i s u b s t i t u t e d c o u n t e r p a r t under t r i p l e t s e n s i t i z a t i o n . R e c a l l t h a t the m e t h y l e s t e r a n a l o g f a v o r s t h e 2 a , 6 c - d i s u b s t i t u t e d p r o d u c t e x c l u s i v e l y o v e r t h e 1 , 2 - d i s u b s t i t u t e d p r o d u c t . H a v i n g e s t a b l i s h e d t h a t t h e compounds b o t h come from i n i t i a l v i n y l - v i n y l b r i d g i n g ( p a t h i . F i g u r e 3.09), th e r e a s o n s f o r t h e i n c r e a s e o f bond b c l e a v a g e must be a d d r e s s e d . The b r a n c h i n g s t e p i n v o l v e d comes from the f i r s t b i r a d i c a l t o the second b i r a d i c a l . F a c t o r s d e t e r m i n i n g s e l e c t i v i t y a r e n o t c l e a r l y u n d e r s t o o d as methods t o measure b i r a d i c a l a c t i v a t i o n and s t a b i l i t y have n o t been w e l l e s t a b l i s h e d . However, th e f o l l o w i n g d i s c u s s i o n i s an a t t e m p t t o shed l i g h t on some p o s s i b l e c o n s i d e r a t i o n s . E x a m i n a t i o n o f t h e second b i r a d i c a l s (BRI and BR2, F i g u r e 3.09) shows BR3 has b o t h r a d i c a l s l o c a t e d on d e l o c a l i z a b l e c e n t e r s whereas BR2 has o n l y one o f the two r a d i c a l s on a d e l o c a l i z a b l e c e n t e r . As a r e s u l t , t h i s a p p r o a c h f a v o r s the f o r m a t i o n o f t h e 2 a , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e ( 4 0 a ) . I n a c c o r d a n c e w i t h t h i s a p p r o a c h , d i m e t h y l e s t e r 29 forms t h e 2 a , 6 c - d i s u b s t i t u t e d p r o d u c t e x c l u s i v e l y from t r i p l e t s e n s i t i z a t i o n . However, Weedon e t a l . ^ - * - ^ have f o u n d no p r e f e r e n c e i n a s t u d y o f [2+2] p h o t o c y c l o a d d i t i o n s f o r the f o r m a t i o n o f a c y l r a d i c a l s . C r i s t o l ^'^c ^ on the o t h e r hand, r e p o r t e d f i n d i n g s o f a c y l r a d i c a l s e l e c t i v i t y i n t h e di - 7 r-methane rearrangement o f d i b e n z o b a r r e l e n e s . The major d i f f e r e n c e between c a r b o x y l i c a c i d s and e s t e r s i n t h i s s i t u a t i o n i s t h a t c a r b o x y l i c a c i d s a r e l e s s e f f i c i e n t a t s t a b i l i z i n g a d j a c e n t r a d i c a l s as the c a r b o n y l s a r e i n v o l v e d i n h y d r o g e n b o n d i n g . T h e l o w e r e d e f f i c i e n c y o f r a d i c a l s t o r e s o n a t e onto t h e a c i d c a r b o n y l s h o u l d r e n d e r b o t h second i n t e r m e d i a t e s (BR2 and BR3) comparable i n t h e i r a b l l l t i e s t o form. I n a d d i t i o n , bond b may p o s s i b l y be more e a s i l y c l e a v e d t h a n bond a. I t has been r e p o r t e d t h a t e x c i t e d c a r b o n y l s a d j a c e n t t o c y c l o p r o p a n e r i n g s , s i m i l a r t o BRI, t e n d t o f a v o r ^ - c l e a v a g e (bond b) when o t h e r f a c t o r s a r e n o t p r e s e n t . • The o n l y f l a w i n u s i n g t h i s model i s t h a t the b i r a d i c a l c o n s i d e r e d (BRI) i s i n the ground s t a t e . A n o t h e r i d e a t h a t may be me n t i o n e d comes from c r y s t a l l o g r a p h i c a n a l y s e s o f o t h e r 2 , 3 - d i a c y l b e n z o b a r r e l e n e s . I t was c o n s i s t e n t l y n o t i c e d t h a t bond b i s s u b s t a n t i a l l y l o n g e r t h a n bond a ( F i g u r e 3.10b).95 T h i s i s a good i n d i c a t i o n o f r e l a t i v e c o v a l e n t bond s t r e n g t h . However, the major drawback i s t h a t i t i s u n c l e a r whether the r e l a t i v e bond s t r e n g t h s w i l l r e m a i n unchanged i n BRI. O Compound X = Y = O C H 3 29 X = Ph, Y = OMe 43 X = Ph, Y = OEt 44 X = Ph, Y = O i P r 45 X = Y == O C H 3 47 ( C l , C 4 , C 5 , Cg = C H 3 ) bond a (Â) bond b (Â) 1.520(1) 1.542(8) 1.519(2) 1.536(2) 1.517(3) 1.532(3) 1.522(3) 1.536(3) 1.530(4) 1.540(3) F i g u r e 3.10b T a b l e o f Bond " a " and "b" Lengths from X - r a y A n a l y s i s . I n a s o l i d s t a t e p h o t o c h e m i c a l s t u d y , c r y s t a l s o f b e n z o b a r r e l e n e 40 were p h o t o l y z e d u n t i l they became y e l l o w w i t h s l i g h t m e l t i n g on the s u r f a c e (4 and 15 h o u r s ) . The r e s u l t i n g NMR s p e c t r a o f the d i s s o l v e d c r y s t a l s showed no p h o t o p r o d u c t s . A l t h o u g h UV a n a l y s i s and t h e change i n p h y s i c a l appearance c o n f i r m t h a t p hotons have been a b s o r b e d , no s i n g l e t o r t r i p l e t p h o t o p r o d u c t s were d e t e c t e d . The e x c i t e d e nergy i s s u g g e s t e d t o have d i s s i p a t e d from i n t e r n a l c o n v e r s i o n , g e n e r a t i n g h e a t . F l u o r e s c e n c e may have a l s o c o n t r i b u t e d t o the d e a c t i v a t i o n as w e l l . Many a c i d s e x i s t i n d i m e rs t h r o u g h h y d r o g e n b o n d i n g ^ ^ and as e v i d e n c e d i n t h e s o l i d s t a t e i n f r a r e d s p e c t r u m o f the s t a r t i n g m a t e r i a l ( F i g u r e 3.11a), compound 40 a l s o i s h y d r o g e n bonded. R a t h e r t h a n a s i n g l e a b s o r p t i o n i n the c a r b o n y l r e g i o n , t h e r e a r e s e v e r a l a b s o r p t i o n bands a r i s i n g from the symmetric and asymmetric s t r e t c h i n g f r e q u e n c i e s o f t h e d imer. I n a c r y s t a l l i n e e n v i r o n m e n t , r e s t r i c t i n g the p o r t i o n o f t h e m o l e c u l e t h a t moves most i n a r e a c t i o n w i l l i n t u r n h i n d e r the r e a c t i o n . I t i s r e a s o n a b l e t o assume t h a t the p o r t i o n s o f b e n z o b a r r e l e n e 40 t h a t move the most a r e the c a r b o x y l i c a c i d s u b s t i t u e n t s . A l t h o u g h , X - r a y c r y s t a l d a t a i s n o t a v a i l a b l e , i t c a n be r e a s o n a b l y p r o p o s e d t h a t the s t r o n g i n t e r m o l e c u l a r h y d r o g e n b o n d i n g b i n d s the c a r b o n y l appendages t o t h e l a t t i c e s u c h t h a t r e a c t i o n c a n n o t t a k e p l a c e . T h i s s i t u a t i o n i s d e p i c t e d i n F i g u r e 3.11b, where the a n c h o r i n g o f t h e a c i d groups p r e v e n t s bond f o r m a t i o n between the two v i n y l s . Figure 3.11 a) S o l i d State Infrared Spectrum of Diacid AO. b) Simple Representation of the Reaction Cavity of Diacid 40 Showing the Hydrogen Bond Anchors. S u p p o r t f o r t h i s argument comes from a r e c e n t p u b l i c a t i o n by S c h e f f e r e t a l . ^ ^ on the p h o t o c h e m i s t r y o f e s t e r / a c i d v i n y l d i s u b s t i t u t e d d i b e n z o b a r r e l e n e 66 ( F i g u r e 3.12). F o c u s s i n g on the di - T T-methane r e a r r a n g e m e n t , t h e y f ound t h a t i n t e r m o l e c u l a r H-bonding o f the a c i d e s s e n t i a l l y p r e v e n t s i n i t i a l b o n d i n g on the a c i d s i d e ( p a t h i i ) i n the s o l i d s t a t e . The H-bonds a n c h o r i n g the a c i d group r e s t r i c t s the m o t i o n r e q u i r e d i n i n i t i a l bond f o r m a t i o n on the a c i d s i d e . As a r e s u l t , p r o d u c t 66b from the i n i t i a l e s t e r s i d e b o n d i n g ( p a t h i ) i s f a v o r e d 95 : 5. I n s o l u t i o n , however, i n t e r m o l e c u l a r H-bonding p l a y s a l e s s s i g n i f i c a n t r o l e . fîga Ratio ggjj a) in Solid State 5 : 95 b) 0.01 M in benzene 72 : 27 c) in NaHCOg 90 ; 10 F i g u r e 3.12 Hydrogen Bonding E f f e c t s on the P h o t o c h e m i s t r y o f Benzo-b a r r e l e n e 66. C. P h o t o c h e m i s t r y o f 1 , 4 - D l h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c A n h y d r i d e ( 4 1 ) . A n h y d r i d e s a r e u n s t a b l e t o c h r o m a t o g r a p h i c s e p a r a t i o n on s i l i c a g e l . I n the p h o t o c h e m i c a l s t u d y o f a n h y d r i d e 41, n u c l e a r m a g n e t i c r e s o n a n c e was the key f a c t o r i n t h e a s s ignment o f p h o t o p r o d u c t s t r u c t u r e and r a t i o . On an a n a l y t i c a l s c a l e , a n h y d r i d e 41 was p h o t o l y z e d i n e t h y l a c e t a t e and benzene t o g i v e complete c o n v e r s i o n t o t h r e e p r o d u c t s , i n d e p e n d e n t o f s o l v e n t . These t h r e e p h o t o p r o d u c t s were c h a r a c t e r i z e d as 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e -2 a , 6 c - d i c a r b o x y l i c a n h y d r i d e ( 4 1 a ) , n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c anhydride^-^ ( 4 1 b ) , and 2a, 2b, 6b, 6c - t e t r a h y d r o b e n z o [ a] c y c l o p r o p a [ c d ] -p e n t a l e n e - 1 , 2 - d i c a r b o x y l i c a n h y d r i d e (41c, F i g u r e 3.13) by NMR and GC-MS o f the r e a c t i o n m i x t u r e . The NMR s p e c t r u m o f t h e r e a c t i o n m i x t u r e i s shown i n F i g u r e 3.14. No b e n z o c y c l o o c t a t e t r a e n e 41d was d e t e c t e d . I n o r d e r t o c o n f i r m the i n i t i a l NMR a s s i g n m e n t s , a p r e p a r a t i v e s c a l e p h o t o l y s i s was p e r f o r m e d and t h e r e s u l t i n g m i x t u r e o f a n h y d r i d e s was c o n v e r t e d t o t h e i r c o r r e s p o n d i n g d i m e t h y l e s t e r s by r e a c t i n g the p h o t o l y s a t e f i r s t w i t h m e t h a n o l , t h e n w i t h diazomethane. The t h r e e d i e s t e r s were s e p a r a t e d by column chromatography on s i l i c a g e l and i n d e p e n d e n t l y c h a r a c t e r i z e d as b e n z o s e m i b u l l v a l e n e 29a, d i m e t h y l n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l a t e , ^ ' ^ and b e n z o s e m i b u l l v a l e n e 29f ( F i g u r e 3.13). F l g u r e 3.13 P h o t o c h e m i s t r y o f B e n z o b a r r e l e n e A n h y d r i d e 41. F i g u r e 3.14 NMR Spectrum o f A n h y d r i d e 41 R e a c t i o n M i x t u r e f r o m D i r e c t P h o t o l y s i s . The r e a c t i o n r a t i o s were n o t i c e d t o f l u c t u a t e w i t h the c o n v e r s i o n as some p h o t o p r o d u c t s undergo p h o t o d e c o m p o s i t i o n more r a p i d l y t h a n o t h e r s . D i r e c t quantum y i e l d measurement o f t h e s e a n h y d r i d e p r o d u c t s i s too d i f f i c u l t as the p r o d u c t s c o u l d n o t be p u r i f i e d f o r GC s t a n d a r d i z a t i o n . The n e x t most e f f e c t i v e method o f a c c u r a t e p h o t o p r o d u c t r a t i o d e t e r m i n a t i o n i s t o c a r e f u l l y m o n i t o r the r e a c t i o n r a t i o s as a f u n c t i o n o f c o n v e r s i o n . T l i i s was done by GC and the r e s u l t i n g 20 r e a d i n g s were p l o t t e d i n F i g u r e 3.15. GC i n t e g r a t i o n r a t i o s o f 41a, 41b, and 41c were s t a n d a r d i z e d by NMR t o be r o u g h l y 1 : 1 : 1 , r e s p e c t i v e l y . A t h i g h e r c o n v e r s i o n s , the e r r o r i n GC i n t e g r a t i o n may be s u b s t a n t i a l l y g r e a t e r as the s i g n a l t r a c e o f 41b appears v e r y b r o a d and o v e r l a p s w i t h t h e o t h e r two s i g n a l s . A r e l a t i v e r a t e o f f o r m a t i o n o f p r o d u c t s 41a, 41b, and 41c was d e t e r m i n e d t o be 25 : 19 : 56 from the graph o f F i g u r e 3.15 a t low c o n v e r s i o n ( c a . 1 0 % ) . F i g u r e 3.15 P l o t o f A n h y d r i d e P h o t o p r o d u c t C o m p o s i t i o n as a F u n c t i o n o f S t a r t i n g M a t e r i a l C o n v e r s i o n . T r i p l e t s e n s i t i z a t i o n u s i n g a c e t o n e gave c o m p l e t e c o n v e r s i o n o f s t a r t i n g m a t e r i a l t o b e n z o s e m i b u l l v a l e n e s 41a and 41c. However, compound 41c r a p i d l y decomposes upon f u r t h e r p h o t o l y s i s . The r a t i o o f t h e two a t a low c o n v e r s i o n ( c a . 12%) i s 36 : 64 o f 41a t o 41c, by GC. The c o n f i d e n c e i n t h i s d e t e r m i n e d r a t i o i s much g r e a t e r as t h e r e i s no i n t e r f e r e n c e o f compound 41b i n t h e GC. S i m i l a r t o t h e o t h e r systems, the two b e n z o s e m i b u l l v a l e n e s i n t h i s s t u d y a r e s u g g e s t e d t o come from the t r i p l e t - m e d i a t e d di - 7 r-methane r e a r r a n g e m e n t ( F i g u r e 3.16). B e n z o s e m i b u l l v a l e n e 41a comes from i n i t i a l v i n y l - v i n y l b o n d i n g ( p a t h i ) f o l l o w e d by bond a c l e a v a g e . R e c a l l t h a t 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s c a n be formed from two di - T T-methane r o u t e s , v i n y l - v i n y l b r i d g i n g ( p a t h i ) o r b e n z o - v i n y l b r i d g i n g ( p a t h i i ) . S e l e c t i v e l y l a b e l l e d (Cj^, C 4 , C 5 , and Cg p o s i t i o n s ) s t a r t i n g m a t e r i a l was p h o t o l y z e d t o d e t e r m i n e t h e p r e f e r e n c e between the two r o u t e s . A g a i n the l a b e l l e d p o s i t i o n s o f compound 41c i n d i c a t e t h a t i n i t i a l v i n y l - v i n y l b o n d i n g i s t h e o n l y pathway t a k e n . F i g u r e 3.16 Pathways t o P h o t o p r o d u c t F o r m a t i o n from A n h y d r i d e 41. I n b o t h d i r e c t and t r i p l e t - s e n s i t i z e d p h o t o l y s e s , benzo-s e m i b u l l v a l e n e 41c i s formed a p p r o x i m a t e l y t w i c e as f a s t as the b e n z o s e m i b u l l v a l e n e 41a. The r e l a t i v e amount o f 1 , 2 - d i s u b s t i t u t e d p r o d u c t (41c) formed i s even h i g h e r t h a n i n the d i a c i d s t u d y . B o t h 41a and 41c come from t h e same i n i t i a l b i r a d i c a l ( B R I ) . The s t a b i l i t y between the two s e c o n d a r y b i r a d i c a l s (BR2 and BR3) base d on b o t h r a d i c a l d e l o c a l i z a t i o n and from MM2 c a l c u l a t i o n s ^ ^ ^ f a v o r BR3, l e a d i n g t o the minor 2 a , 6 c - d i s u b s t i t u t e d p r o d u c t ( 4 1 a ) . I t i s s u s p e c t e d t h a t t h e r e i s a v e r y d e l i c a t e b a l a n c e between the f o r m a t i o n o f t h e s e two benzosemi-b u l l v a l e n e s and s u b t l e f a c t o r s c a n d r a s t i c a l l y a l t e r p r o d u c t s e l e c t i v i t y . A l s o , the n o t i o n t h a t the p r e c u r s o r (BRI) and b o t h immediate b r a n c h - p o i n t s p e c i e s (BR2 and BR3) a r e b i r a d i c a l s f u r t h e r c o m p l i c a t e the u n d e r s t a n d i n g o f t h i s s e l e c t i v i t y . Anyhow, some s u g g e s t i o n s a r e f o r w a r d e d i n a t t e m p t t o r a t i o n a l i z e t h e i n c r e a s e i n 1 , 2 - d i s u b s t i t u t e d p r o d u c t f o r m a t i o n . R e c a l l i n PART I I I B o f t h i s t h e s i s t h a t t h e t e n d e n c y f o r bond b c l e a v a g e t o BR2 maybe i n c r e a s e d b a s e d on the o b s e r v e d /9-cleavage o f c y c l o -propane r i n g s a d j a c e n t t o e x c i t e d c a r b o n y l s ^ ^ . 9 8 ^ ^ d on r e l a t i v e l e n g t h s o f bond a and b i n a nalogous compounds ( F i g u r e 3.10b). One major d i f f e r e n c e between t h i s c y c l i c a n h y d r i d e (41) and t h e d i m e t h y l e s t e r compound (29) i s t h a t the c a r b o n y l s o f the a n h y d r i d e a r e e f f i c i e n t l y c o n j u g a t e d t o each o t h e r by the r i g i d five-membered r i n g . On t h e o t h e r hand, the two m e t h y l e s t e r s o f 29 a r e shown from X - r a y a n a l y s i s t o be t o o b u l k y f o r s i m u l t a n e o u s c o n j u g a t i o n t o t h e a d j a c e n t v i n y l . Perhaps t h e s t a b i l i z a t i o n a t t a i n e d by t h e r e g e n e r a t i o n o f t h i s c o n j u g a t i o n i n BR2 f o r m a t i o n c o n t r i b u t e s t o the i n c r e a s e i n 41c f o r m a t i o n . T u r n i n g t o the f o r m a t i o n o f n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c a n h y d r i d e ( 4 1 b ) , i t was n o t e d t h a t t h i s p r o d u c t i s n o t o b s e r v e d from t h e t r i p l e t s e n s i t i z a t i o n o f b e n z o b a r r e l e n e 41; t h i s i n d i c a t e s a s i n g l e t -m e d i a t e d p r o c e s s . The b e n z o b a r r e l e n e s i n t h i s s t u d y were s y n t h e s i z e d by a D i e l s - A l d e r c y c l o a d d i t i o n o f an a c e t y l e n e t o a n a p h t h a l e n e ; t h e r e f o r e , i t seems r e a s o n a b l e t h a t t h i s n a p h t h a l e n e d e r i v a t i v e i s formed from a r e v e r s e [4+2] c y c l o a d d i t i o n a l o n g w i t h a c e t y l e n e . Owing t o i t s v o l a t i l i t y , a c e t y l e n e was n o t i s o l a t e d . However, e x a m i n a t i o n o f t h e NMR s p e c t r u m i n F i g u r e 3.14 shows a 2 - p r o t o n ( r e l a t i v e t o t h e s i g n a l I n t e g r a t i o n o f n a p h t h a l e n e d e r i v a t i v e 41b) s i n g l e t a t 2.20 ppm. T h i s s i g n a l may l i k e l y be from a c e t y l e n e (2.3 ppm) . •'-'^•^  U n c e r t a i n t y a r i s e s as the s o l v e n t a c e t o n e has a s i n g l e t a t 2.07 ppm. R e v e r s e D i e l s - A l d e r r e a c t i o n s have been known t o o c c u r p h o t o c h e m i c a l l y i n o t h e r b a r r e l e n e systems.-^^^ C r y s t a l s o f a n h y d r i d e 41 were p h o t o l y z e d (A > 260 nm) t o g i v e two p r o d u c t s , b e n z o s e m i b u l l v a l e n e s 41a and 41c (13 h o u r s ) ; t h e c r y s t a l appearance changed from l i g h t y e l l o w t o c l o u d y d a r k y e l l o w w i t h c r a c k s . NMR a n a l y s i s o f the r e a c t i o n m i x t u r e showed a 38 : 62 r a t i o o f 41a t o 41c a t 8% c o n v e r s i o n . A g a i n compound 41c i s formed i n a l m o s t t w i c e the abundance o f compound 41a. Thus t h e r e i s l i t t l e s o l i d s t a t e s e l e c t i v i t y i n b e n z o s e m i b u l l v a l e n e f o r m a t i o n . A l t h o u g h no X - r a y a n a l y s i s o f t h e s t a r t i n g m a t e r i a l was p e r f o r m e d , i t can be s u g g e s t e d t h a t the a n h y d r i d e p o r t i o n o f the m o l e c u l e does n o t p r o t r u d e f r o m the b a r r e l e n e s k e l e t o n enough t o be a f f e c t e d by t h e l a t t i c e upon r e a c t i o n . I t i s i n t e r e s t i n g t o n o t e t h a t the n a p h t h a l e n e d e r i v a t i v e 41b was n o t d e t e c t e d i n the s o l i d s t a t e r u n s . A p o s s i b l e r e a s o n i s t h a t the e l i m i n a t e d a c e t y l e n e i s u n a b l e t o l e a v e the cage o f t h e c r y s t a l l a t t i c e . The l a t t i c e i s t i g h t enough t o h o l d the e l i m i n a t e d s p e c i e s i n p l a c e f o r r e c o m b i n a t i o n t o the n a p h t h a l e n e . T h i s "cage e f f e c t , "•'-^ ^ o r i g i n a l l y a p p l i e d t o s o l u t i o n systems a l s o has r e l e v a n c e i n t h e c r y s t a l l a t t i c e . F o r example, many Type I c l e a v a g e s a r e made c o m p e t i t i v e l y u n f a v o r a b l e o r d r a s t i c a l l y a l t e r e d because the f r a g m e n t s a r e u n a b l e t o l e a v e the r e a c t i o n c a v i t y . •'-^^ I n f a c t o n l y a few d e c a r b o n y l a t i o n r e a c t i o n s from the Type I p r o c e s s have been r e p o r t e d i n t h e s o l i d s t a t e and t h e s e a r e shown t o have s t r o n g l a t t i c e cage e f f e c t s . D. P h o t o c h e m i s t r y o f 2 , 3 - d i b e n 2 o y l - l , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e ( 4 2 ) . I n t h e s t u d y o f 2 , 3 - d i a c y l - s u b s t i t u t e d b e n z o b a r r e l e n e s , the i d e a i s t h a t 2 a , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s a r e g e n e r a l l y f a v o r e d i n s o l u t i o n ; however, the f o r m a t i o n 1 , 2 - d i s u b s t i t u t e d benzo-s e m i b u l l v a l e n e s i s i n c r e a s e d from c a r b o n y l s w i t h weaker r a d i c a l s t a b i l i z i n g p r o p e r t i e s o r from the c y c l i c a n h y d r i d e where th e c a r b o n y l s a r e r i g i d l y f i x e d i n a c o n j u g a t e d system t o the a d j a c e n t v i n y l . I t i s n e c e s s a r y t o s y n t h e s i z e a n o t h e r system t o f u r t h e r i n v e s t i g a t e t h i s . So f a r , two c a r b o n y l systems t h a t i n c r e a s e 1 , 2 - d i s u b s t i t u t e d p r o d u c t f o r m a t i o n and o n l y one c a r b o n y l system t h a t g i v e s o n l y 2 a , 6 c - d i s u b s t i t u t e d p r o d u c t f o r m a t i o n have been s t u d i e d . I t w o u l d be a p p r o p r i a t e t o have a n o t h e r s u b s t r a t e t h a t has b u l k y c a r b o n y l s i d e - c h a i n s and c a n e f f i c i e n t l y d e l o c a l i z e a d j a c e n t r a d i c a l s t o enhance 2 a , 6 c - d i s u b s t i t u t e d p r o d u c t f o r m a t i o n . A l s o e f f i c i e n t i n t e r s y s t e m c r o s s i n g t o the t r i p l e t i s p r e f e r r e d as the s u b j e c t r e a c t i o n i s t r i p l e t - m e d i a t e d . D i r e c t p h o t o l y s i s t o t h e t r i p l e t e x c i t e d s t a t e w i l l a l s o a l l o w t h e s e di - 7 r-raethane r e a c t i o n s t o be i n v e s t i g a t e d i n t h e s o l i d s t a t e . As a r e s u l t , 2 , 3 - d i b e n z o y l - 1 , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e (42) was s y n t h e s i z e d . The b e n z o y l group i s s i m i l a r t o acetophenone, a known t r i p l e t s e n s i t i z e r t h a t a b s o r b s r a d i a t i o n above 330 nm. The i n t e n t i o n i s t o e x c i t e the b a r r e l e n e system t o the t r i p l e t s t a t e t h r o u g h the b e n z o y l chromophore f o r a di-7r-methane r e a c t i o n . D i r e c t p h o t o l y s i s (A > 330nm) o f b e n z o b a r r e l e n e 42 i n benzene o r a c e t o n i t r i l e gave 2 a , 6 c - d i b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] -p e n t a l e n e (42a) as the o n l y p r o d u c t i n d e p e n d e n t o f s o l v e n t ( F i g u r e 3.17). However, h i g h e r r e a c t i o n c o n v e r s i o n s l e d t o the f o r m a t i o n o f 1 , 6 c - d i b e n z o y l - 2 b , 6 b ( 2 a H ) - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e (42c) as a s e c o n d a r y p h o t o p r o d u c t from compound 42a. Compound 42a and 42c a r e c h r o m a t o g r a p h i c a l l y i n s e p a r a b l e ; t h e r e f o r e , b e n z o s e m i b u l l v a l e n e 42c was c h a r a c t e r i z e d i n a m i x t u r e w i t h compound 42a. The NMR s p e c t r a l e x p a n s i o n o f the m i x t u r e i s shown i n F i g u r e 3.18. The p r o t o n p a t t e r n i n t he NMR s p e c t r u m o f the s e m i b u l l v a l e n e r i n g a g rees w i t h the r e f e r e n c e p a t t e r n s shown i n PART I I . On the o t h e r hand, b e n z o s e m i b u l l v a l e n e 42a was c h a r a c t e r i z e d t h r o u g h a b e n z o p h e n o n e - s e n s i t i z e d r e a c t i o n . An 18-molar e x c e s s o f the s e n s i t i z e r ( a b s o r b s c a . 75% o f i n c i d e n t r a d i a t i o n ) t o b e n z o b a r r e l e n e 42 gave complete c o n v e r s i o n t o compound 42a w i t h o n l y t r a c e 42c d e t e c t e d . Benzophenone was removed e a s i l y by column chromatography. F i g u r e 3.17 P h o t o c h e m i s t r y o f D i b e n z o y l B e n z o b a r r e l e n e 42. F i g u r e 3.18 C h a r a c t e r i z a t i o n o f D i b e n z o y l B e n z o s e m i b u l l v a l e n e 42c i n M i x t u r e w i t h 42a, by NMR. S i m i l a r t o the p r e v i o u s s t u d i e s , the 2 a , 6 c - d i s u b s t i t u t e d benzo-s e m i b u l l v a l e n e 42a i s s u g g e s t e d t o form from a di-7r-methane rearrangement t h r o u g h i n i t i a l v i n y l - v i n y l b o n d i n g f o l l o w e d by bond a c l e a v a g e ( F i g u r e 3.19). T h i s i s formed as the o n l y p r i m a r y p h o t o p r o d u c t from s o l u t i o n p h o t o l y s i s s u p p o r t i n g the i d e a t h a t c a r b o n y l s on 2,3-disub-s t i t u t e d b e n z o b a r r e l e n e s t h a t can e f f i c i e n t l y s t a b i l i z e a d j a c e n t r a d i c a l s enhance the 2 a , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e f o r m a t i o n o v e r 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s . The quantum y i e l d f o r the f o r m a t i o n o f compound 42a i s 0,10 ( s t d . dev. = 0.04), d e t e r m i n e d from l i n e a r r e g r e s s i o n c a l c u l a t i o n s o u t l i n e d i n the e x p e r m e n t a l s e c t i o n and graphed i n F i g u r e 3.20. F i g u r e 3.19 Mechanisms t o P h o t o p r o d u c t F o r m a t i o n f r o m D i b e n z o y l B e n z o b a r r e l e n e ( 4 2 ) . B e n z o s e m i b u l l v a l e n e 42c comes from a [1,3] p h o t o c h e m i c a l s h i f t o f compound 42a, and a g a i n the two a r e i n a p h o t o s t a t i o n a r y s t a t e . The o b s e r v a t i o n t h a t t h i s i n t e r c o n v e r s i o n does n o t p r o c e e d w i t h benzophenone s e n s i t i z a t i o n i n d i c a t e s t h a t t h i s s h i f t may be e i t h e r a s i n g l e t o r a h i g h e r energy t r i p l e t p r o c e s s . The 42a t o 42c p h o t o s t a t i o n a r y s t a t e was d e t e r m i n e d t o be 6 : 4. 0.3 0.2 <D = 0.10 ( std. dev. = 0.04 ) 0.1 X X 0 X X 0 5 10 15 % conversion F i g u r e 3.20 Graph o f Quantum Y i e l d ($) o f 42a v e r s u s S t a r t i n g M a t e r i a l (42) C o n v e r s i o n . C r y s t a l s o f b e n z o b a r r e l e n e 42 were p h o t o l y z e d (A > 290 nm) f o r 15 and 45 h o u r s ; the r e s u l t i n g u nmelted y e l l o w c r y s t a l s were a n a l y z e d by NMR t o show a 1 : 1 r a t i o o f b e n z o s e m i b u l l v a l e n e s 42a and 4Zb a t 8% and 14% c o n v e r s i o n , r e s p e c t i v e l y . Compound 42b was o b t a i n e d p u r e from a p r e p a r a t i v e s c a l e p h o t o l y s i s . C r y s t a l s o f b e n z o b a r r e l e n e 42 were c r u s h e d p r i o r t o p h o t o l y s i s t o a c h i e v e a h i g h e r c o n v e r s i o n ( 3 8 % ) . A f t e r the r e a c t i o n , the p h o t o l y s a t e was p a s s e d t h r o u g h t h r e e s u c c e s s i v e chromatography columns, t h e l a s t o f w h i c h y i e l d e d 9% o f p u r e 42b. B e n z o s e m i b u l l v a l e n e 42b i s s u g g e s t e d t o come from a di-jr-methane r e a r r a n g e m e n t w i t h i n i t i a l v i n y l - v i n y l b o n d i n g f o l l o w e d by bond b c l e a v a g e as shown i n F i g u r e 3.19. The i n t e r e s t i n g f e a t u r e o f t h e s o l i d s t a t e r e a c t i v i t y h e r e i s t h a t compound 42b i s n o t o b s e r v e d i n s o l u t i o n . Two approaches t o e x p l a i n i n g t h e r e s u l t s c a n be t a k e n . The f i r s t a p p r o a c h r e l a t e s t o the s o l u t i o n d e t e r m i n a n t s o f p h o t o p r o d u c t f o r m a t i o n - e l e c t r o n i c e f f e c t s . The b u l k y b e n z o y l groups i n t h e c r y s t a l l a t t i c e c o u l d be o u t o f c o n j u g a t i o n w i t h the a d j a c e n t c a r b o n - c a r b o n d o u b l e bond, thus l o w e r i n g the a b i l i t y o f t h e s e groups t o d e l o c a l i z e the r a d i c a l d u r i n g r e a c t i o n . T h i s f a c t o r c o u l d e x p l a i n t h e f o r m a t i o n o f compound 42b i n the s o l i d s t a t e . The second a p p r o a c h i n v o l v e s the p r e s e n c e o f s p e c i f i c i n t e r a c t i o n s w i t h the c r y s t a l l a t t i c e t h a t c a n d e t e r o r enhance e i t h e r o f the two pathways; i t i s r e a s o n a b l e t o imagine t h a t the l a r g e b e n z o y l groups a r e r e q u i r e d t o move s u b s t a n t i a l l y d u r i n g the r e a c t i o n . As a r e s u l t , s e l e c t i v i t y c o u l d be a f f e c t e d by the c r y s t a l l a t t i c e . As d e s c r i b e d i n the I n t r o d u c t i o n s e c t i o n , t h i s i s t h e most w i d e l y u s e d method o f e x p l a i n i n g c r y s t a l l i n e s t a t e r e a c t i v i t y . No X - r a y c r y s t a l d a t a was a v a i l a b l e i n t h i s c a s e t o t e s t t h e v a l i d i t y o f t h e s e two appr o a c h e s . However, a more d e t a i l e d i n v e s t i g a t i o n i n t o t he s o l i d s t a t e b e h a v i o r o f 2 , 3 - d i s u b s t i t u t e d benzo-b a r r e l e n e w i l l be d i s c u s s e d , u s i n g t h e s e two a p p r o a c h e s , i n PART IV o f t h i s t h e s i s . C o n c l u d i n g the s o l u t i o n s t u d y o f b e n z o s e m i b u l l v a l e n e f o r m a t i o n from t h e di - 7 r-methane r e a r r a n g e m e n t , i n i t i a l b r i d g i n g o f the 2 , 3 - d i c a r b o n y l b e n z o b a r r e l e n e i s e x c l u s i v e l y v i n y l - v i n y l i n n a t u r e , as t h e d i s r u p t i o n o f a r o m a t i c i t y i n b e n z o - v i n y l b o n d i n g r e q u i r e s t o o much energy. More s u b t l e i s the s e l e c t i v i t y e x h i b i t e d i n t h e second b o n d - b r e a k i n g s t e p o f the r e a c t i o n pathway. G e n e r a l l y , f o r m a t i o n o f 2 a , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s a r e f a v o r e d o v e r the 1 , 2 - d i s u b s t i t u t e d p r o d u c t s ; however, f o r m a t i o n o f the l a t t e r p r o d u c t i s i n c r e a s e d when c a r b o n y l s i n e f f i c i e n t a t d e l o c a l i z i n g a d j a c e n t r a d i c a l s o r a c y c l i c a n h y d r i d e a r e u s e d as s u b s t i t u e n t s . PART IV. PHOTOCHEMISTRY OF UNSYMMETRICALLY DISUBSTITUTED BENZOBARRELENES A. P h o t o c h e m i s t r y o f M e t h y l 2 - B e n z o y l - 1 , 4 - d i h y d r o - 1 , 4 - e t h e n o n a p h t h a l e n e -3 - c a r b o x y l a t e ( 4 3 ) . Suc c e s s i n a c h i e v i n g t r i p l e t p r o d u c t s from d i r e c t p h o t o l y s i s a l o n g w i t h some i n t e r e s t i n g t r i p l e t - m e d i a t e d s o l i d s t a t e p h o t o c h e m i s t r y i n t h e d i b e n z o y l system, i n s p i r e d t he d e s i g n o f t h e n e x t system f o r i n v e s t i g a t i o n . The o b j e c t i v e was t o s t u d y a s i m i l a r system whereby s u b s t i t u e n t s c a n be e a s i l y a l t e r e d y e t r e t a i n t he a b i l i t y t o e f f i c i e n t l y i n t e r s y s t e m c r o s s t o t h e t r i p l e t e x c i t e d s t a t e upon d i r e c t i r r a d i a t i o n . As a r e s u l t , m e t h y l 2 - b e n z o y l - 1 , 4 - d i h y d r o - 1 , 4 - e t h e n o -n a p h t h a l e n e - 3 - c a r b o x y l a t e (43) was s y n t h e s i z e d . A b e n z o y l group i s r e t a i n e d and the e s t e r can e a s i l y be a l t e r e d t o s t u d y s u b s t i t u e n t e f f e c t s on the di - T T-methane rearrangement. However, i t must be r e c o g n i z e d t h a t t h i s i s now an u n s y m m e t r i c a l b e n z o b a r r e l e n e , p r e p a r e d i n r a c e m i c form. F u r t h e r m o r e , d i f f e r e n t r e g i o i s o m e r s can a l s o a r i s e d e p e n d i n g on t h e d i r e c t i o n o f i n i t i a l b o n d i n g ; t h i s i n e f f e c t d o u b l e s the number o f p o s s i b l e b e n z o s e m i b u l l v a l e n e p r o d u c t s from the di - T T-methane r e a r r a n g e -ment ( F i g u r e 4.01). A g a i n , the s o l u t i o n p h o t o c h e m i s t r y o f t h i s system must be u n d e r s t o o d f i r s t b e f o r e the b e h a v i o r i n the c r y s t a l l i n e s t a t e c a n be p r o b e d . B Initial Benzo-Vinyl Bridging Figure 4.01 Possible Di-7r-Methane Rearrangement Pathways for the 2-Benzoyl 3-Ester Benzobarrelene. D i r e c t p h o t o l y s i s o f b e n z o b a r r e l e n e 43 i n benzene, m e t h a n o l , a c e t o n i t r i l e , o r hexanes gave s i x p r o d u c t s i n d e p e n d e n t o f s o l v e n t . O v e r l a p p i n g o f s i g n a l s and t h e r m a l d e c o m p o s i t i o n o f the p r o d u c t s from u s i n g the DB-1 and carbowax columns p r e v e n t e d a c c u r a t e r e a c t i o n p r o d u c t r a t i o d e t e r m i n a t i o n by GC. However, the s i n g l e p r o t o n s i g n a l s o f t h e s e m i b u l l v a l e n e p r o d u c t s i n the NMR a r e s u f f i c i e n t l y s e p a r a t e d f o r r a t i o d e t e r m i n a t i o n by i n t e g r a t i o n ; t h i s i s shown i n F i g u r e 4.03, and t h e a s s i g n m e n t s a r e c o r r e l a t e d w i t h the s p e c t r a o f pure samples. The photo-p r o d u c t r a t i o s were t h u s d e t e r m i n e d t o be 50 : 25 : 17 : t r a c e : 8 : t r a c e o f compounds 43a, 43b, 43h, 43c, 43d, and 43e. I s o l a t e d from d i r e c t p h o t o l y s i s by column chromatography a r e m e t h y l 2 a - b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 6c -c a r b o x y l a t e (43a) and m e t h y l 6 c - b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o -p r o p a [ c d ] p e n t a l e n e - l ( 2 a H ) - c a r b o x y l a t e ( 4 3 b ) ; s p e c t r a l d a t a a r e c o n s i s t e n t w i t h the e s t a b l i s h e d p a t t e r n s f o r t h e s e s t r u c t u r e s . Benzo-s e m i b u l l v a l e n e 43a was n o t i c e d t o p o s s e s s two c r y s t a l l i n e m o r p h o l o g i e s , n e e d l e s and p r i s m s , v e r i f i e d by t h e i r marked d i f f e r e n c e s i n m e l t i n g p o i n t s and c a r b o n y l s t r e t c h i n g f r e q u e n c i e s ( n e e d l e s , MP = 106-107 °C, IR: e s t e r C=0 1733 cm^^, b e n z o y l C=0 1674 cm'^ and p r i s m s , MP = 113-114 °C, IR: e s t e r C=0 1723 cm''^, b e n z o y l C=0 1677 cm'^) . F i g u r e 4.02 P h o t o c h e m i s t r y o f B e n z o y l M e t h y l E s t e r B e n z o b a r r e l e n e 43. F i g u r e 4.03 NMR S p e c t r a l E x p a n s i o n s o f the B e n z o y l M e t h y l E s t e r Benzo b a r r e l e n e 43 R e a c t i o n M i x t u r e from D i r e c t S o l u t i o n P h o t o l y s i s i n C D C I 3 . T r i p l e t - s e n s i t i z e d p h o t o l y s i s o f b e n z o b a r r e l e n e 43 was done on an a n a l y t i c a l s c a l e w i t h a 1 0 - f o l d m o l a r e x c e s s o f benzophenone as t h e s e n s i t i z e r ( a b s o r b s c a . 85% o f i n c i d e n t r a d i a t i o n ) . The p h o t o l y s i s (A > 330 nm) was m o n i t o r e d by GC t o show the i n i t i a l f o r m a t i o n o f two major p h o t o p r o d u c t s , b e n z o s e m i b u l l v a l e n e 43a and m e t h y l 6 c - b e n z o y l - 2 b , 6 b - d i h y d r o -b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 2 a - c a r b o x y l a t e ( 4 3 h ) . As t h e c o n v e r s i o n i n c r e a s e d , compound 43h began t o d i m i n i s h and o t h e r p h o t o p r o d u c t s were o b s e r v e d . E x t e n d e d p h o t o l y s i s r e s u l t s i n a s i m i l a r GC t r a c e t o d i r e c t s o l u t i o n p h o t o l y s i s . B e n z o s e m i b u l l v a l e n e 43h was i s o l a t e d from a d i f f e r e n t e x p e r i m e n t , p h o t o l y s i s i n polymer m a t r i x media. On an a n a l y t i c a l s c a l e , s t a r t i n g m a t e r i a l 43 was d i s s o l v e d t o g e t h e r w i t h a 1 0 - f o l d w/w e x c e s s o f medium m o l e c u l a r w e i g h t p o l y [ m e t h y l m e t h a c r y l a t e ] (PMMA) i n a minimiim amount o f methylene c h l o r i d e . T h i s m i x t u r e was s p r e a d o v e r t h e s u r f a c e o f t h r e e P y r e x m i c r o s c o p e s l i d e s and t h e s o l v e n t a l l o w e d t o e v a p o r a t e . The r e s i d u a l c l e a r f i l m h o u s i n g t h e r e a c t a n t was p h o t o l y z e d (A > 290 nm) a t room t e m p e r a t u r e and c o n v e r s i o n was m o n i t o r e d by GC u n t i l no s t a r t i n g m a t e r i a l remained. The r e s u l t i n g r a t i o was 34 : 12 : 30 : 12 : 12 o f 43a, 43b, 43h, 43d, and 43e. The e x p e r i m e n t was r e p e a t e d a t -50°C t o g i v e a much s l o w e r r e a c t i o n t o the same r a t i o . The p r e p a r a t i v e s c a l e p r o c e d u r e was same as above e x c e p t t h a t the i n n e r s u r f a c e o f a l a r g e P y r e x tube was used as the s u p p o r t f o r the f i l m . F l a s h column chromatography gave compound 43a i n the f i r s t band f o l l o w e d by b e n z o s e m i b u l l v a l e n e 43h i n the s e c o n d band. The t h i r d band c o n t a i n e d an i n s e p a r a b l e m i x t u r e o f i s o m e r s 43d and 43e. I n t e r e s t i n g l y , no compound 43b c o u l d be i s o l a t e d , a l t h o u g h t h i s compound was d e t e c t e d i n t h e GC o f t h e r e a c t i o n m i x t u r e . T h i s i s because compound 43h t h e r m a l l y r e a r r a n g e s i n the GC above 200 °C t o g i v e 43b; i n j e c t i o n s a t 200 °C gave o n l y p a r t i a l r e a r r a n g e m e n t t o 43b, and t h e r e f o r e the GC d e t e c t i o n o f 43b i s an a r t i f a c t o f 43h d e c o m p o s i t i o n . B e n z o s e m i b u l l v a l e n e s 43b and 43h were i n t e r c o n v e r t e d by p h o t o l y s i s (A > 290 nm) i n benzene and a c e t o n i t r i l e t o c o n f i r m the e x i s t e n c e o f a p h o t o s t a t i o n a r y s t a t e . The 8 : 2 r a t i o o f compounds 43b and 43h i s i n d e p e n d e n t o f s o l v e n t . S i m i l a r l y , b e n z o s e m i b u l l v a l e n e 43a was p h o t o l y z e d (A > 290 nm) i n benzene, a c e t o n i t r i l e , and a c e t o n e t o g i v e a maximum c o n v e r s i o n o f 20% by GC ( c o r r e c t e d f o r d e t e c t o r r e s p o n s e by NMR) t o m e t h y l l - b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 6 c ( 2 a H ) -c a r b o x y l a t e ( 4 3 c ) , shown i n F i g u r e 4.02. The r e a c t i o n i s s o l v e n t i n d e p e n d e n t , b u t the r a t e o f c o n v e r s i o n i n a c e t o n e was n o t i c e d t o be s l o w e r . P h o t o p r o d u c t 43c was i s o l a t e d from a l a r g e r s c a l e p h o t o l y s i s i n benzene f o l l o w e d by two s u c c e s s i v e c h r o m a t o g r a p h i c s e p a r a t i o n s . Independent p h o t o l y s e s o f compound 43c gave compound 43a w i t h t h e same 8 : 2 r a t i o o f 43a t o 43c. Compound 43a comes from a t r i p l e t - m e d i a t e d di-jr-methane r e a r r a n g e m e n t v i a i n i t i a l v i n y l - v i n y l b r i d g i n g on the b e n z o y l s i d e o f t h e dou b l e bond ( p a t h i i , F i g u r e 4.01). T h i s i s f o l l o w e d by the c l e a v a g e o f bond a t o g i v e the o b s e r v e d p r o d u c t . S i m i l a r l y , b e n z o s e m i b u l l v a l e n e 43h comes from a di - 7 r-raethane r e a r r a n g e m e n t w i t h i n i t i a l v i n y l - v i n y l bond f o r m a t i o n on the e s t e r s i d e ( p a t h i ) ; subsequent c l e a v a g e o f bond a g i v e s the p r o d u c t . Compound 43b i s a p h o t o c h e m i c a l [1,3] s h i f t p r o d u c t o f b e n z o s e m i b u l l v a l e n e 43h, from i n i t i a l c l e a v a g e o f C2g^-C^^ bond. The r e a c t i o n p r o c e e d s on d i r e c t p h o t o l y s i s and a c e t o n e s l o w s the r e a c t i o n as i t competes w i t h the s u b s t r a t e f o r r a d i a t i o n . T h e r e f o r e , t h i s i s p r o b a b l y a s i n g l e t - m e d i a t e d p r o c e s s . L i k e w i s e , b e n z o s e m i b u l l v a l e n e 43c comes from a s i m i l a r p h o t o c h e m i c a l [1,3] s h i f t o f compound 43a. The r e a c t i o n was a l s o n o t i c e d t o be s l o w e r i n a c e t o n e , i n d i c a t i n g a s i n g l e t r e a c t i o n . The s u g g e s t e d mechanisms a r e s u p p o r t e d by a d e u t e r i u m l a b e l l i n g e x p e r i m e n t ; p h o t o l y s i s o f b e n z o b a r r e l e n e 43 w i t h d e u t e r i u m l a b e l s p l a c e d on t h e C-^, C 4 , C 5 , and Cg p o s i t i o n s r e d i s t r i b u t e s t h e l a b e l s t o the C2h' ^3' '^6' Cg^^ p o s i t i o n s on b e n z o s e m i b u l l v a l e n e 43a. T h i s a g r e e s w i t h t h e p r o p o s e d r o u t e i n F i g u r e 4.01. From the same NMR s p e c t r u m o f t h e r e a c t i o n m i x t u r e , the l a b e l d i s t r i b u t i o n on compound 43b (^2h' ^3' ^6' ^^'^ ^6h^ a l s o s u p p o r t s the r e a c t i o n sequence p r o p o s e d . I n c o n t r a s t , the 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s (43d and 43e) a r e formed i n t r a c e amounts from d i r e c t p h o t o l y s i s o f b e n z o b a r r e l e n e 43. T h i s a g r e e s w i t h the f i n d i n g s i n PART I I I t h a t c a r b o n y l s u b s t i t u e n t s s u c h as b e n z o y l and e s t e r f a v o r the c l e a v a g e o f bond a ( F i g u r e 4.01, p a t h s i and i i ) t o form 2 a , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s o v e r t h e c l e a v a g e o f bond b t o g i v e the 1 , 2 - d i s u b s t i t u t i o n . The key method t o a s s i g n i n g the r e l a t i v e s u b s t i t u e n t p o s i t i o n s on compounds 43a and 43h comes n o t from NMR, b u t from IR a n a l y s i s o f t h e i r [1,3] s h i f t i s o m e r s . C a r b o n y l s t r e t c h i n g f r e q u e n c i e s o f a,y8-unsaturated e s t e r s a r e about 30 wavenumbers l o w e r t h a n t h e i r s a t u r a t e d counterparts.-*-^^ S a t u r a t e d e s t e r s have c a r b o n y l s t r e t c h i n g f r e q u e n c i e s a t about 1730 cm"-*-; the e s t e r o f compounds 43a, 43c, and 43h have s t r e t c h i n g f r e q u e n c i e s a t 1723 cm'-'-, 1726 cm'^, and 1718 cm"^, r e s p e c t i v e l y . However, the e s t e r c a r b o n y l o f compound 43b s t r e t c h e s a t 1703 cm"-*^  i n d i c a t i n g the p r e s e n c e o f a , / 9 - u n s a t u r a t i o n . Quantum y i e l d s ($) f o r the f o r m a t i o n o f p r i m a r y p h o t o p r o d u c t s 43a and 43h were d e t e r m i n e d a t d i f f e r e n t c o n v e r s i o n s and graphed ( F i g u r e 4.04). The r e s u l t s were e x t r a p o l a t e d t o z e r o c o n v e r s i o n u s i n g l i n e a r l e a s t s q u a r e s c a l c u l a t i o n s t o o b t a i n the r e p o r t e d v a l u e s . U s i n g v a l e r o p h e n o n e a c t i n o m e t r y , the quantum y i e l d s f o r f o r m a t i o n o f b e n z o s e m i b u l l v a l e n e s 43a and 43h a r e 0.14 ( s t d . dev. 0.01) and 0.13 ( s t d . dev. 0.02), r e s p e c t i v e l y . The quantum y i e l d v a l u e s f o r the two di - T T-methane rearrangement p r o d u c t s a r e w e l l w i t h i n e r r o r l i m i t s o f each o t h e r , i n d i c a t i n g a l a c k o f p r e f e r e n c e between the b e n z o y l s i d e and the e s t e r s i d e f o r s o l u t i o n phase i n i t i a l b o n d i n g . 0.3 0.2 0.1 compound 43a 4> = 0.138 (std. dev. = 0.012] 0.3 0.2 -^x 0.1 compound 43tl «I> = 0.127 ( std. dev. = 0.023 ) 0 1 2 3 4 5 6 % conversion 1 2 3 4 5 % conversion F i g u r e 4.04 P l o t s o f Quantum Y i e l d v e r s u s C o n v e r s i o n o f S t a r t i n g M a t e r i a l f o r t he F o r m a t i o n o f B e n z o s e m i b u l l v a l e n e s 43a and 43h i n Benzene. H a v i n g e s t a b l i s h e d the s o l u t i o n phase p h o t o c h e m i c a l b e h a v i o r o f b e n z o b a r r e l e n e 43, t h i s i n v e s t i g a t i o n c a n now be e x t e n d e d t o the s o l i d s t a t e . C r y s t a l s o f b e n z o b a r r e l e n e 43 were p h o t o l y z e d and th e r e s u l t i n g m i x t u r e a n a l y z e d by GC t o show the f o r m a t i o n o f t h r e e p h o t o p r o d u c t s . NMR a n a l y s i s o f t h e r e a c t i o n m i x t u r e showed a 17% c o n v e r s i o n t o compounds 43d, 43e, and 4 3 f i n a r a t i o o f 50 : 30 : 20. NMR e x p a n s i o n s o f t h i s m i x t u r e a r e shown i n F i g u r e 4.05. H i g h e r c o n v e r s i o n s ( c a . 20%) l e d t o s u r f a c e m e l t i n g and d e t e c t a b l e amounts o f compound 43a began t o form. On a p r e p a r a t i v e s c a l e , c r y s t a l s o f 43 were p h o t o l y z e d (A > 290 nm) u n t i l t he c r y s t a l s were y e l l o w b u t showed no s i g n o f m e l t i n g ( c a . 18% c o n v e r s i o n ) . The r e s u l t i n g m i x t u r e was chromatographed to g i v e t h r e e p a r t i a l l y o v e r l a p p i n g bands; the f i r s t was r e c h r o m a t o g r a p h e d to g i v e m e t h y l 6 c - b e n z o y l - 2 a , 2 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e -6 b - c a r b o x y l a t e ( 4 3 f , 5% y i e l d ) . T h i s i s the f i r s t e n c o u n t e r w i t h b e n z o s e m i b u l l v a l e n e s o f t h i s s u b s t i t u t i o n p a t t e r n and t h e r e f o r e r e q u i r e d e x t r a e f f o r t f o r i t s c o n v i c t i o n . The NMR s p e c t r u m a l o n g w i t h d e t a i l s o f t h e a s s i g n m e n t a r e p r e s e n t e d i n PART I I o f t h i s t h e s i s . The s t r u c t u r e was c o n f i r m e d by an X - r a y c r y s t a l a n a l y s i s ( F i g u r e 2.10). ~! i i i I 1 1 I i 1—I— r - r 43f 43 __JA. . 43f lIlL ' 1 ' I I I I I ' i I I I I I I [ I I I 4 ppm 3 -i r r 43 ï'« s.'* 3 ^ ' s'o' 43d / 43e 43f - i ~ — — ^ 1 — ppm F i g u r e 4.05 NMR S p e c t r a l E x p a n s i o n s o f the R e a c t i o n M i x t u r e from P h o t o l y s i s o f B e n z o b a r r e l e n e 43 i n the S o l i d S t a t e . The s e c o n d c h r o m a t o g r a p h i c band was r e c o v e r e d s t a r t i n g m a t e r i a l . The t h i r d band was r e c h r o m a t o g r a p h e d t o g i v e an i n s e p a r a b l e m i x t u r e o f 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s 43d and 43e. C o n s e q u e n t l y , the two were c h a r a c t e r i z e d t o g e t h e r . The NMR s p e c t r u m o f t h i s m i x t u r e i s shown i n F i g u r e 2.05 and d e t a i l s o f t h i s a s s i g n m e n t a r e p r o v i d e d i n PART I I o f the t h e s i s . B e n z o s e m i b u l l v a l e n e 4 3 f undergoes a p h o t o c h e m i c a l [1,3] s h i f t i n s o l u t i o n t o g i v e compound 43g; t h e y a l s o e x i s t i n a p h o t o s t a t i o n a r y s t a t e ( F i g u r e 4.02). The r a t i o o f 43f t o 43g i s 2 : 8. V a r y i n g the s o l v e n t (benzene, a c e t o n i t r i l e , o r a c e t o n e ) i n a s e r i e s o f a n a l y t i c a l p h o t o l y s e s does n o t a f f e c t t h e r a t i o ; however, t h e r e a c t i o n was n o t i c e d t o p r o c e e d s l o w e r w i t h a c e t o n e , i n d i c a t i n g a s i n g l e t - m e d i a t e d r e a c t i o n . As shown i n F i g u r e 4.01 and men t i o n e d p e r i o d i c a l l y t h r o u g h o u t t h e t h e s i s , 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s (43d and 43e) can come from two t y p e s o f di - 7 r-methane r e a r r a n g e m e n t , e i t h e r i n i t i a l v i n y l - v i n y l o r i n i t i a l b e n z o - v i n y l b o n d i n g . F o r b o t h c a s e s , i n i t i a l b r i d g i n g on the b e n z o y l s i d e o f the d o u b l e bond l e a d s t o compound 43e ( p a t h s i i and i l l ) , and b r i d g i n g on t h e e s t e r s i d e g i v e s compound 43d ( p a t h s i and i v ) . D e u t e r i u m l a b e l s on C^ j^  and C4 o f the s t a r t i n g m a t e r i a l w i l l e v e n t u a l l y f i n d t h e i r way t o the ^23. Cg^ p o s i t i o n s i f i n i t i a l b e n z o - v i n y l b o n d i n g o c c u r s . S i m i l a r l y , the l a b e l s w i l l be l o c a t e d i n the C^IQ and Cg^ p o s i t i o n s o f p h o t o p r o d u c t s 43d and 43e i f i n i t i a l v i n y l - v i n y l b o n d i n g i s t a k e n . A f t e r two s u c c e s s i v e c h r o m a t o g r a p h i c s e p a r a t i o n s o f t h e d e u t e r a t e d r e a c t i o n m i x t u r e , NMR s p e c t r a were r u n i n b o t h CDCI3 and benzene-dg; the l a t t e r s o l v e n t was u s e d t o a l l e v i a t e an o v e r l a p p i n g s i g n a l . The r e s u l t s show i n i t i a l v i n y l - v i n y l b r i d g i n g was the o n l y r o u t e t a k e n ( l a b e l s on C2b and Cg^^). The 6b,ôc-disubstituted b e n z o s e m i b u l l v a l e n e 4 3 f i s s u g g e s t e d t o come from an u n u s u a l r o u t e , a "tri-7r-methane" rearrangement;^-'- t h i s r e a c t i o n r e q u i r e s t h r e e v i n y l groups s e p a r a t e d by two methane c a r b o n s t o p r o c e e d , shown i n F i g u r e 4.06. I n s t e a d o f a bond b e i n g b r o k e n a f t e r i n i t i a l b o n d i n g ( r o u t e o f the di-;r-methane r e a r r a n g e m e n t ) , a n o t h e r b r i d g e 431 O F i g u r e 4.06 Tri-w-Methane Rearrangement Mechanism t o Form Benzosemi-b u l l v a l e n e 4 3 f . i s formed t o the t h i r d d o u b l e bond. F i n a l l y , bond c o f t h i s p o l y c y c l i c b i r a d i c a l i s c l e a v e d t o d i r e c t l y g i v e the o b s e r v e d p r o d u c t ( 4 3 f ) . The C]^ and C 4 l a b e l l e d b e n z o b a r r e l e n e 43 r e a r r a n g e d t o the and C^j^ p o s i t i o n s o f the p r o d u c t s u p p o r t i n g t h i s t r i - 7 r - m e t h a n e mechanism. However, t h e r e i s s t i l l u n c e r t a i n t y as t o whether i n i t i a l bond f o r m a t i o n i s v i n y l - v i n y l ( p a t h i , F i g u r e 4.06), o r b e n z o - v i n y l ( p a t h i i ) . The l i k e l i h o o d t h a t b o t h bonds form a t t h e same time i s s m a l l , as Zimmerman has c a l c u l a t e d t h a t such p r o c e s s i s e n e r g e t i c a l l y d i s f a v o r e d f o r b a r r e l e n e i t s e l f . - ' - ' ' The o b s e r v e d s o l i d s t a t e r e s u l t s a r e v e r y I n t e r e s t i n g from th e f a c t t h a t no 2 a , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s a r e formed. R e c a l l t h a t t h e r e a c t i o n pathways t o 2 a , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s d i f f e r from the 1 , 2 - d i s u b s t i t u t i o n i n the s e cond b o n d - c l e a v a g e s t e p ( F i g u r e 4.01). Two approaches a r e f o r w a r d e d t o r a t i o n a l i z e t h i s o b s e r v a t i o n . The f i r s t a p p r o a c h r e l a t e s t o t h e r e l a t i v e s t a b i l i t y o f t h e two s e c o n d a r y 1 , 3 - b i r a d i c a l i n t e r m e d i a t e s (BR2 and BR3, F i g u r e 4.07). I f a c a r b o n y l group i s c o n f o r m a t i o n a l l y a l i g n e d t o s t a b i l i z e the a d j a c e n t r a d i c a l o f the i n i t i a l i n t e r m e d i a t e (BRI) by d e l o c a l i z a t i o n , t h e n the system t h a t r e t a i n s t h i s d e l o c a l i z a t i o n a f t e r t h e s econd bond c l e a v a g e s t e p w i l l be more s t a b l e (BR2) t h a n the system t h a t l o s e s t h i s d e l o c a l i z a t i o n (BR3), As a r e s u l t , the 2 a , 6 c - d i s u b s t i t u t e d p r o d u c t from BR2 w i l l be f a v o r e d . However, i f the c a r b o n y l i s h e l d o u t o f c o n j u g a t i o n , t h e n d e l o c a l i z a t i o n o f the a d j a c e n t r a d i c a l w i l l n o t be p o s s i b l e and the 1 , 2 - d i s u b s t i t u t e d p r o d u c t s h o u l d a l s o be formed, v i a BR3. T h i s r a t i o n a l e has s e v e r a l s h o r t - f a l l s ; i f the c a r b o n y l s i n t h e c r y s t a l were i n d e e d out o f c o n j u g a t i o n , b o t h 2 a , 6 c - d i s u b s t i t u t e d and 1 , 2 - d i s u b s t i t u t e d r e g i o i s o m e r s s h o u l d be formed, s i m i l a r t o t h e d i b e n z o y l 42 s o l i d s t a t e r e s u l t s . O n l y 1 , 2 - d i s u b s t i t u t i o n p r o d u c t s a r e seen h e r e . F u r t h e r m o r e , X - r a y c r y s t a l a n a l y s i s o f the s t a r t i n g m a t e r i a l shows the b e n z o y l c a r b o n y l i s n o n - c o n j u g a t e d w i t h the v i n y l group b u t the e s t e r i s n i c e l y a l i g n e d f o r c o n j u g a t i o n ( F i g u r e 4.08). T h i s a n a l y s i s w o u l d p r e d i c t the f o r m a t i o n o f 1 , 2 - d i s u b s t i t u t e d 43d from i n i t i a l b e n z o y l s i d e b r i d g i n g and the f o r m a t i o n o f 2 a , 5 c - d i s u b s t i t u t e d 43a from i n i t i a l e s t e r s i d e b r i d g i n g . A l t h o u g h t h i s f i r s t a p p r o a c h seemed p l a u s i b l e i n the r a t i o n a l i z a t i o n t o the s o l i d s t a t e r e s u l t s o f the d i b e n z o y l s y s t e m ( 4 2 ) , I t i s n o t s u p p o r t i v e o f the o b s e r v a t i o n h e r e . F i g u r e 4.07 R a d i c a l S t a b i l i z a t i o n A p p r o a c h t o 1 , 2 - D i s u b s t i t u t e d Benzo-s e m i b u l l v a l e n e F o r m a t i o n i n the S o l i d S t a t e . F l g u r e 4.08 X - r a y C r y s t a l S t r u c t u r e S t e r e o d l a g r a m D i s p l a y i n g the C o n f o r m a t i o n o f B e n z o b a r r e l e n e 43. The second approach t o r a t i o n a l i z i n g the s o l e f o r m a t i o n o f 1,2-o v e r 2 a , 6 c - d i s u b s t i t u t i o n i n the s o l i d s t a t e i s from s p e c i f i c i n t e r a c t i o n s o f the s u b s t r a t e w i t h the c r y s t a l l a t t i c e . As a u n i m o l e c u l a r r e a c t i o n p r o c e e d s from s t a r t i n g m a t e r i a l t h r o u g h I n t e r m e d i a t e ( s ) t o p r o d u c t , the t h r e e - d i m e n s i o n a l geometry o f the s p e c i e s changes w i t h i n the l a t t i c e . Such changes t h a t conform t o the l a t t i c e e n v i r o n m e n t w i l l be a l l o w e d and t h o s e t h a t do n o t , d i s a l l o w e d . F i r s t , the d i f f e r e n c e s between the g e o m e t r i c r e q u i r e m e n t s o f the two r e a c t i o n pathways must be u n d e r s t o o d . F i g u r e 4.09 shows, b a s e d on m o l e c u l a r models, the m o t i o n s r e q u i r e d f o r the f o r m a t i o n o f compounds 43d ( 1 , 2 - d i s u b s t i t u t e d ) and 43h (2a,6c-d i s u b s t i t u t e d ) , from i n i t i a l e s t e r - s i d e b r i d g i n g . I n o r d e r t o emphasize the g e o m e t r i c changes w i t h m o l e c u l a r m o t i o n , the models a r e drawn w i t h the b e n z o - p l a n e f i x e d f o r r e f e r e n c e . The key i t e m s t o w a tch f o r are the movements o f the l a r g e c a r b o n y l appendages, as t h e y a r e i n t i m a t e l y a s s o c i a t e d w i t h t o the bond-making and b o n d - b r e a k i n g p o r t i o n o f the F i g u r e 4.09 M o t i o n s R e q u i r e d f o r B e n z o s e m i b u l l v a l e n e s 43d and 43h F o r m a t i o n . m o l e c u l e . These appendages a r e most l i k e l y t o s u f f e r from l a t t i c e i n t e r f e r e n c e s . C l e a v a g e o f bond b t o form compound 43d c a u s e s a s l i g h t s h i f t o f b o t h e s t e r and b e n z o y l groups t o t h e l e f t . C l e a v a g e o f bond a t o g i v e compound 43h m a i n t a i n s the b e n z o y l i n t h e f r o n t a l downward p o s i t i o n b u t p i v o t s t h e e s t e r t r e m e n d o u s l y upward and t o t h e r i g h t , sweeping o u t a l a r g e volume o f space. C l e a r l y , f o r m a t i o n o f t h e f a v o r e d s o l u t i o n p r o d u c t s ( 2 a , 6 c - d i s u b s t i t u t e d p r o d u c t s ) r e q u i r e s more movement t h a n i t s 1 , 2 - d i s u b s t i t u t e d c o u n t e r p a r t . However, one must be aware t h a t the d e s c r i b e d m o t i o n s may be e x a g g e r a t e d , as t h e movements o f the b e n z o - r i n g a r e n o t c o n s i d e r e d . The n e x t s t e p i s t o examine t h e c r y s t a l l a t t i c e o f t h e s t a r t i n g m a t e r i a l f o r c l o s e c o n t a c t s w h i c h may h i n d e r o r a s s i s t the r e q u i r e d m o t i o n s . The v a l i d i t y o f the r e p r e s e n t a t i o n u s i n g t h e benzo r i n g as a f i x e d p o i n t o f r e f e r e n c e i s s u p p o r t e d ; from the t a b l e o f i n t e r m o l e c u l a r d i s t a n c e s l e s s t h a n 3.60 Â, t h e r e a r e many c o n t a c t s above and b e l o w the benzo r i n g l i m i t i n g i t s a l l o w e d m o t i o n d u r i n g r e a c t i o n . I n a s s o c i a t i o n w i t h t h e c a r b o n y l appendages, f o u r i n t e r m o l e c u l a r c o n t a c t s a r e f o u n d t h a t w o u l d c l e a r l y i n h i b i t the upward and o u tward movement o f the two appendages w i t h r e s p e c t t o the b e n z o - p l a n e ; t h e s e a r e shown w i t h d o t t e d l i n e s i n F i g u r e 4.10. These i n t e r a c t i o n s a r e s u g g e s t e d t o d e t e r t h e f o r m a t i o n o f 2 a , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s i n t h e s o l i d s t a t e . F i r s t the b e n z o y l c a r b o n y l oxygen i s i n v o l v e d i n an H-•-Q c o n t a c t (2.70 Â)-*-^^ w i t h the o r t h o - p r o t o n o f a n e i g h b o r i n g b e n z o y l p h e n y l group. T h i s i n t e r a c t i o n p r e v e n t s the o r t h o - p r o t o n and oxygen o f t h e b e n z o y l group f r o m moving upward and o u tward t o form compound 43a. On the o t h e r s i d e , t h e e t h e r oxygen and the c a r b o n y l c a r b o n on the e s t e r a r e i n v e r y c l o s e p r o x i m i t y t o an a r o m a t i c hydrogen o f an a d j a c e n t m o l e c u l e , a t 2.78 Â and 2.82 Â, r e s p e c t i v e l y . The sum o f v a n der Waals r a d i i f o r H-•-0 i s 2.72 Â and f o r C---H i s 2.90 Â.'" The d i r e c t i o n a l i n f l u e n c e o f these c o n t a c t s r e s t r i c t s t he upward and outward movements r e q u i r e d f o r the f o r m a t i o n o f compound 43h. As a r e s u l t , the l e s s motion-demanding f o r m a t i o n o f compounds 43d and 43e becomes c o m p e t i t i v e l y f a v o r a b l e . These d e s c r i b e d d i s t a n c e s a r e v e r y s i g n i f i c a n t , as the c l o s e r the c o n t a c t , the b e t t e r the c o n t r o l i n s e l e c t i v i t y . F i g u r e 4,10 P a c k i n g S t e r e o d l a g r a m f o r B e n z o y l M e t h y l E s t e r Benzo-b a r r e l e n e 43. B e n z o s e m i b u l l v a l e n e 4 3 f i s the f i r s t o b s e r v a t i o n o f a t r i - j r - m e t h a n e r earrangement i n t h i s s t u d y . I n f a c t , v e r y few tri-7r-methane r e a r r a n g e m e n t s have e v e r been o b s e r v e d . P h o t o p r o d u c t 43f i s formed o n l y i n the s o l i d s t a t e , thus some s p e c i f i c l a t t i c e e f f e c t must be e n h a n c i n g the f o r m a t i o n o f t h i s p r o d u c t . R e c a l l , the s u b s t i t u t e d v i n y l on the e s t e r s i d e i s r e q u i r e d t o bond t o the b e n z o - r i n g i n t h e d e s c r i b e d mechanism ( F i g u r e 4.06). Upon e x a m i n a t i o n o f the above i n t e r m o l e c u l a r c o n t a c t s , t h e e s t e r c a r b o n y l c a r b o n i s 2.82 Â away from an a r o m a t i c h y d r o g e n o f an a d j a c e n t m o l e c u l e . T h i s i s w e l l below t h e sum o f v a n d e r Waals r a d i i f o r C---H d i s t a n c e o f 2.90 Â.''^ The d i r e c t i o n a l i t y o f t h i s i n t e r a c t i o n encourages the e s t e r group t o move to w a r d the benzo r i n g . T h i s i n t e r a c t i o n c o u l d , i n t u r n , l o w e r t h e a c t i v a t i o n p a r a m e t e r s r e q u i r e d f o r b e n z o - v i n y l b r i d g i n g , r e s u l t i n g i n t h e f o r m a t i o n o f t h e t r i - T T - m e t h a n e p r o d u c t 4 3 f i n the s o l i d s t a t e . A s i m i l a r i n t e r a c t i o n i s n o t p r e s e n t on the b e n z o y l s i d e and t h e r e f o r e , t h e r e c i p r o c a l p r o d u c t i s n o t o b s e r v e d . B. P h o t o c h e m i s t r y o f E t h y l 2 - B e n z o y l - l , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e -3 - c a r b o x y l a t e ( 4 4 ) . The s i m p l e r e p l a c e m e n t o f a m e t h y l group w i t h an e t h y l group was done t o s t u d y the e f f e c t o f the c r y s t a l l a t t i c e on a s l i g h t l y d i f f e r e n t m o l e c u l e . B e f o r e the s o l i d phase s e l e c t i v i t y can be i n v e s t i g a t e d , the s o l u t i o n p h o t o c h e m i s t r y o f e t h y l 2 - b e n z o y l - 1 , 4 -d i h y d r o - 1 , 4 - e t h e n o n a p h t h a l e n e - 3 - c a r b o x y l a t e (44) must be t h o r o u g h l y u n d e r s t o o d f i r s t ( F i g u r e 4.11). F i g u r e 4.11 P h o t o c h e m i s t r y o f E t h y l 2 - B e n z o y l - 1 , 4 - d i h y d r o - 1 , 4 - e t h e n o -n a p h t h a l e n e - 3 - c a r b o x y l a t e ( 4 4 ) . S i m i l a r t o t h e m e t h y l a n a l o g , d i r e c t p h o t o l y s e s i n benzene o r a c e t o n i t r i l e l e d t o two major and f o u r minor p h o t o p r o d u c t s , i n d e p e n d e n t o f s o l v e n t . These were l a t e r i d e n t i f i e d by NMR t o be compounds 44a, 44b, 44c, 44d, 44e, and 4 4 f i n a r a t i o o f 45 : 32 : 10 : 10 : 3 : t r a c e by NMR ( F i g u r e 4.11). On a p r e p a r a t i v e s c a l e t h r e e bands were i s o l a t e d f r o m column chromatography. The f i r s t two bands were e t h y l 2 a - b e n z o y l -2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 6 c - c a r b o x y l a t e (44a) and e t h y l 6 c - b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - l ( 2 a H ) -c a r b o x y l a t e ( 4 4 b ) , r e s p e c t i v e l y . The s p e c t r a l p a t t e r n s o f t h e s e compounds were c o r r e l a t e d t o p a t t e r n s i n PART I I f o r t h e i r a s s i g n m e n t . The t h i r d band was a 1 : 7 : 2 i n s e p a r a b l e m i x t u r e o f b e n z o s e m i b u l l v a l e n e s 44c, 44d, and 44e; t h e l a t t e r two compounds were c h a r a c t e r i z e d from t h i s m i x t u r e . A g a i n , t h e i r a s s i g n m e n t s were b a s e d on NMR d a t a . T r i p l e t - s e n s i t i z e d p h o t o l y s i s o f compound 44 u s i n g an 8 0 - f o l d m o l a r e x c e s s o f benzophenone ( a b s o r b s c a . 92% o f i n c i d e n t r a d i a t i o n ) gave two major p r o d u c t s , b e n z o s e m i b u l l v a l e n e s 44a and 44c i n a r a t i o o f 48 : 52 by GC. Compound 44c was i s o l a t e d from column chromatography f o r c h a r a c t e r i z a t i o n . The p h o t o s t a t i o n a r y s t a t e between b e n z o s e m i b u l l v a l e n e s 44c and 44b was c o n f i r m e d from i n d e p e n d e n t p h o t o l y s e s o f the two. The r a t i o o f 44b t o 44c i s 8 : 2 by NMR. T h i s i n t e r c o n v e r s i o n i s i n d e p e n d e n t o f s o l v e n t . L i k e w i s e , b e n z o s e m i b u l l v a l e n e 44a p h o t o l y z e s (A > 290 nm) t o g i v e the [1,3] s h i f t p r o d u c t 44f i n a p h o t o s t a t i o n a r y s t a t e r a t i o o f 9 : 1 = 44a : 4 4 f by NMR. B e n z o s e m i b u l l v a l e n e 4 4 f , however, c o u l d n o t be s e p a r a t e d from 44a and was, t h e r e f o r e , c h a r a c t e r i z e d i n a m i x t u r e . These [ 1 , 3 ] - p h o t o c h e m i c a l s h i f t s i n i t i a t e t h r o u g h t h e c l e a v a g e o f the C2a-Cgp bond. T h i s i s l i k e l y a s i n g l e t p r o c e s s as p r o d u c t s a r e n o t formed from the benzophenone s e n s i t i z a t i o n (A > 330 run); a l s o , the use o f acet o n e as a s e n s i t i z e r (A > 290 nm) sl o w s the r e a c t i o n . B e n z o s e m i b u l l v a l e n e s 44a, 44c, 44d, and 44e a r e a l l p r o d u c t s o f the di - T T-methane rearrangement ( F i g u r e 4.01). Compound 44a comes from i n i t i a l v i n y l - v i n y l b r i d g i n g on the b e n z o y l s i d e ( p a t h i ) f o l l o w e d by c l e a v a g e o f bond a; s i m i l a r l y , compound 44e comes from the c l e a v a g e o f bond b. I n i t i a l v i n y l - v i n y l b r i d g i n g on the e s t e r s i d e ( p a t h i ) f o l l o w e d by c l e a v a g e o f bond a g i v e s compound 44c, a l t e r n a t i v e l y , c l e a v a g e o f bond b g i v e s compound 44d. S i m i l a r t o i t s m e t h y l e s t e r c o u n t e r p a r t , i n i t i a l b o n d i n g p r e f e r e n c e s between the e s t e r s i d e ( p a t h i ) and the b e n z o y l s i d e ( p a t h i i ) were d e t e r m i n e d t o be e s s e n t i a l l y the same from quantum y i e l d measurements f o r the f o r m a t i o n o f compounds 44a and 44c, 0.072 ( s t d . dev. = 0.004) and 0.064 ( s t d . dev. = 0.015), r e s p e c t i v e l y . 0.2 0.1 compound 44a 0 1 2 3 4 5 6 % conversion 0.2 4> = 0.072 ( std. dev. = 0.004 ) O X 0.1 compound 44c <!> = 0.064 (std. dev. = 0.015) 0 1 2 3 4 5 6 % conversion F i g u r e 4.12 Graph o f Quantum Y i e l d v e r s u s C o n v e r s i o n f o r Compounds 44a and 44c i n Benzene. I n t h e s o l i d s t a t e s t u d y , c r y s t a l s o f b e n z o b a r r e l e n e 44 were p h o t o l y z e d (A > 290 nm) u n t i l the c r y s t a l s were s l i g h t l y y e l l o w b u t showed no s i g n o f m e l t i n g (2 h o u r s ) . NMR a n a l y s i s o f t h e r e a c t i o n m i x t u r e shows t h e f o r m a t i o n o f compounds 44a, 44c, 44d, and 44e a t a r a t i o o f 54 : 8 : 23 : 15, r e s p e c t i v e l y a t a c o n v e r s i o n o f c a . 47%. I n a n o t h e r e x p e r i m e n t , c r y s t a l s were p h o t o l y z e d f o r a l o n g e r p e r i o d (5 h o u r s ) t o show a s i m i l a r r a t i o , 64 : 9 : 18 : 9 o f 44a, 44c, 44d, and 44e a t c a . 46% c o n v e r s i o n . The i n t e r e s t i n g f e a t u r e o f t h i s s t u d y i s the d i f f e r e n c e i n s o l i d s t a t e p r o d u c t s e l e c t i v i t y from the m e t h y l a n a l o g . R e c a l l t h e m e t h y l a n a l o g gave o n l y 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s from the di - 7 r-methane r e a r r a n g e m e n t . I n t h i s c a s e , a 2 a , 6 c - d i -s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e (44a) i s t h e major p r o d u c t o v e r t h e o t h e r t h r e e di-7r-methane r e a r r a n g e m e n t p r o d u c t s . Two approaches t o r a t i o n a l i z i n g t h e o b s e r v e d r e s u l t s a r e d i s c u s s e d ; t h e f i r s t a p p r o a c h c o n s i d e r s t h e r e l a t i v e a b i l i t y o f t h e c a r b o n y l groups t o r e s o n a n c e s t a b i l i z e the i n i t i a l r a d i c a l s formed. The b a s i s o f t h i s argument i s d e s c r i b e d i n PART I I I B . X - r a y a n a l y s i s o f s t a r t i n g m a t e r i a l 44 ( F i g u r e 4.13) shows t h a t the e s t e r i s i n c o n j u g a t i o n w i t h the v i n y l group and t h a t the b e n z o y l group i s c o m p l e t e l y out o f c o n j u g a t i o n . A p p l y i n g t h i s a p p r o a c h , i n i t i a l v i n y l - v i n y l b o n d i n g on the b e n z o y l s i d e w i l l a l l o w t h e r a d i c a l n e x t t o t h e e s t e r c a r b o n y l t o be d e l o c a l i z e d , f a v o r i n g the 2a,6c-d i s u b s t i t u t e d p r o d u c t 44a. On the o t h e r hand, i n i t i a l v i n y l - v i n y l b o n d i n g on the e s t e r s i d e w i l l l e a v e b o t h r a d i c a l s w i t h o u t r e s o n a n c e s t a b i l i z a t i o n ; t h i s , t h e r e f o r e , s h o u l d g i v e b o t h compounds 44d and 44c. The o b s e r v e d r e s u l t s seem q u i t e c o n s i s t e n t w i t h t h i s p r e d i c t i o n as compound 44a i s t h e major p r o d u c t o v e r 44e from b e n z o y l - s i d e b r i d g i n g , and compounds 44c and 44d a r e b o t h formed from e s t e r - s i d e b r i d g i n g . F i g u r e 4.13 C r y s t a l l i n e C o n f o r m a t i o n o f Compound 44 f r o m X - r a y A n a l y s i s . The a l t e r n a t i v e approach comes from c o n s i d e r i n g s p e c i f i c s t e r i c i n t e r a c t i o n s o f the s u b s t r a t e w i t h the c r y s t a l l a t t i c e ; the fewer i n t e r a c t i o n s d u r i n g r e a r r a n g e m e n t , the more f a v o r a b l e the p r o d u c t . The g e o m e t r i c r e q u i r e m e n t s f o r t h e s e r e a c t i o n s a r e the same as f o r the b e n z o y l m e t h y l e s t e r compound (43) d e s c r i b e d i n F i g u r e 4.09. F o r m a t i o n o f 2 a , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s 44a and 44c r e q u i r e s an upward and outward movement o f the appendage on the s i d e o f i n i t i a l b o n d i n g , and the f o r m a t i o n o f 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s 44d and 44e r e q u i r e s o n l y a s l i g h t sideways s h i f t o f the appendages away from the s i d e o f i n i t i a l b o n d i n g . The ben z o - p l a n e i s assumed t o be f i x e d i n thes e d e s c r l p t i o n s f o r s i m p l i c i t y ; however, i t must be k e p t i n mind t h a t the whole m o l e c u l e c a n move d u r i n g r e a c t i o n . C o n s i s t e n t w i t h the model, e x a m i n a t i o n o f i n t e r m o l e c u l a r d i s t a n c e s l e s s t h a n 3.60 Â shows 13 o f the t o t a l 19 i n t e r a c t i o n s a r e a s s o c i a t e d w i t h t h e benzo r i n g . T h i s s h o u l d , i n e f f e c t , r e s t r i c t movement o f the benzo r i n g d u r i n g r e a c t i o n . A p a c k i n g d i a g r a m o f t h e s t a r t i n g m a t e r i a l i s shown i n F i g u r e 4.14; r e l e v a n t c o n t a c t s t o t h e appendages a r e drawn w i t h d o t t e d l i n e s . The e s t e r c a r b o n y l oxygen i s i n v o l v e d i n two c o n t a c t s , w i t h t h e e s t e r - s i d e b r i d g e h e a d p r o t o n (2.59 Â) and t h e e s t e r - s i d e v i n y l p r o t o n (2.72 Â) o f an a d j a c e n t m o l e c u l e . The sum o f v a n d e r Waals r a d i i f o r the 0-•-H d i s t a n c e i s 2.72 Â.^^ -phe d i r e c t i o n a l i t y o f t h e s e i n t e r a c t i o n s i n h i b i t s t h e upward and outward movement o f the e s t e r r e q u i r e d f o r f o r m a t i o n o f compound 44c ( F i g u r e 4.09). As a r e s u l t , v e r y l i t t l e compound 44c i s p r o d u c e d i n the s o l i d s t a t e . On the o t h e r hand, t h e r e a r e no s u c h i n t e r a c t i o n s p r e v e n t i n g the upward and o u t w a r d movement o f t h e b e n z o y l group, r e q u i r e d i n the f o r m a t i o n o f compound 44a. I n f a c t , e x a m i n a t i o n o f t h e p a c k i n g arrangement r e v e a l s two n e i g h b o r i n g c o n t a c t s p r e s s i n g on the m e t a - p r o t o n o f the b e n z o y l , one from the b i c y c l i c b r i d g i n g c a r b o n on the e s t e r - s i d e (2.86 Â) and the o t h e r from the b e n z o - c a r b o n b e s i d e i t (2.92 Â) . R e c a l l t h a t the sum o f v a n der Waals r a d i i f o r t h e C---H d i s t a n c e i s 2.90 Â.^^ These c o n t a c t s a r e b e n e a t h the b e n z o y l and a s s i s t i n t h e upward and outward movement g i v i n g enhanced compound 44a f o r m a t i o n r e l a t i v e t o the l e s s motion-demanding 1 , 2 - d i s u b s t i t u t e d p r o d u c t s (44d and 4 4 e ) . R e c a l l , m o t i o n s r e q u i r e d f o r compound 44d f o r m a t i o n a r e d e p i c t e d i n F i g u r e 4.09. A g a i n , t h i s a p p roach e f f e c t i v e l y e x p l a i n s t h e o b s e r v e d s o l i d s t a t e s e l e c t i v i t y . Figure 4.14 Packing Stereodlagram o f B e n z o b a r r e l e n e 44 Showing Selected I n t e r m o l e c u l a r Contacts. C. P h o t o c h e m i s t r y of Isopropyl 2-Benzoyl-l,4-dihydro-1,4-ethenonaphthalene-3-carboxylate (45). The i s o p r o p y l d e r i v a t i v e was a l s o s t u d i e d w i t h t h e i d e a t h a t s o l i d s t a t e p h o t o r e a c t i v i t y may e x p e r i e n c e g r e a t e r l a t t i c e c o n t r o l by the use o f a more b u l k y s i d e - c h a i n group. A g a i n , the s o l u t i o n p h o t o -c h e m i s t r y must be i n v e s t i g a t e d f i r s t t o ensure the c o m p l e t e n e s s o f the s tudy. D i r e c t p h o t o l y s e s (A > 330 nm) i n benzene, a c e t o n i t r i l e , o r methanol showed two major p r o d u c t s and t h r e e minor p r o d u c t s i n d e p e n d e n t o f s o l v e n t ( F i g u r e 4.15). The p r o d u c t s were s u b s e q u e n t l y i d e n t i f i e d as F l g u r e 4.15 P h o t o c h e m i s t r y o f B e n z o y l I s o p r o p y l E s t e r B e n z o b a r r e l e n e 45. compounds 45a, 45b, 45c, 45d, and 45e i n a r a t i o o f 50 : 30 : 8 : 8 : 4 , r e s p e c t i v e l y by NMR i n t e g r a t i o n o f the r e a c t i o n m i x t u r e . The p h o t o l y s i s was r e p e a t e d on a l a r g e r s c a l e and from column chromatography, i s o p r o p y l 2 a - b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 6 c -c a r b o x y l a t e (45a) was i s o l a t e d i n the f i r s t band f o r c h a r a c t e r i z a t i o n . NMR a n a l y s i s a g r e e s w i t h the t y p i c a l p a t t e r n f o r t h e s e s t r u c t u r e s , e s t a b l i s h e d i n PART I I . The second band c o n t a i n e d a 7 : 3 m i x t u r e o f compounds 45b and 45c; t r a i l i n g t he second band were compounds 45d and 45e i n a n o t h e r m i x t u r e . T r i p l e t - s e n s i t i z e d p h o t o l y s i s (A > 330 nm) was done u s i n g a 3 7 - f o l d m o l a r e x c e s s o f benzophenone as s e n s i t i z e r ( a b s o r b s c a . 93% o f i n c i d e n t r a d i a t i o n ) . T h i s i s t o p r e v e n t t h e f o r m a t i o n o f compound 45b, a s e c o n d a r y p h o t o p r o d u c t . C h r o m a t o g r a p h i c s e p a r a t i o n gave t h r e e bands; compound 45a e l u t e d f i r s t (47% y i e l d ) . I s o p r o p y l 6 c - b e n z o y l - 2 b , 6 b -b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 2 a - c a r b o x y l a t e (45c) was i s o l a t e d i n the second band f o r c h a r a c t e r i z a t i o n (37% y i e l d ) . The t h i r d band was a 3 : 1 i n s e p a r a b l e m i x t u r e o f compounds 45d and 45e ( 9 % y i e l d ) . The s t r u c t u r e s o f b o t h compounds 45d and 45e were e a s i l y a s s i g n e d by c o m p a r i s o n w i t h the NMR and IR s p e c t r a o f the o t h e r 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s d e s c r i b e d i n PART I I o f t h i s t h e s i s . P h o t o l y s e s o f b e n z o s e m i b u l l v a l e n e 45c i n benzene, a c e t o n i t r i l e , o r a c e t o n e gave compound 45b t o a maximum c o n v e r s i o n o f 87% ( 9 : 1 = 45b : 4 5 c ) , in d e p e n d e n t o f s o l v e n t . The r e m a i n i n g 45c was i n s e p a r a b l e by column chromatography, t h e r e f o r e , i s o p r o p y l 6 c - b e n z o y l - 2 b , 6 b -d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 1 ( 2 a H ) - c a r b o x y l a t e (45b) was c h a r a c t e r i z e d i n t h i s m i x t u r e . These two compounds a r e i n t e r c o n v e r t e d by a [1,3] s h i f t from i n i t i a l c l e a v a g e o f the C2a-Cg^ bond. A s i n g l e t e x c i t e d s t a t e i s s u g g e s t e d , as t h e r e i s no i n t e r c o n v e r s i o n w i t h benzophenone (Ej- = 69 k c a l / m o l e ) ^ ^ and the r a t e o f r e a c t i o n i s s l o w e d from a c e t o n e p h o t o l y s i s . B e n z o s e m i b u l l v a l e n e 45a was a l s o f o u n d t o e x i s t i n a p h o t o s t a t i o n a r y s t a t e w i t h compound 4 5 f . The p h o t o l y s e s (A > 290 nm) were p e r f o r m e d i n benzene, a c e t o n i t r i l e , o r a c e t o n e t o a f f o r d a 9 : 1 r a t i o o f 45a t o 45f in d e p e n d e n t o f s o l v e n t . The two compounds a r e a l s o i n s e p a r a b l e by column chromatography; as a r e s u l t , i s o p r o p y l 1 - b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] -p e n t a l e n e - 6 c ( 2 a H ) - c a r b o x y l a t e ( 4 5 f ) was c h a r a c t e r i z e d by NMR from t h e m i x t u r e . These two compounds a r e a l s o i n t e r c o n v e r t e d by a s i n g l e t - m e d i a t e d p h o t o c h e m i c a l [1,3] s h i f t b a s e d on the same r e a s o n i n g as above. R e f e r r i n g t o t h e di-ir-methane pathways l i s t e d i n F i g u r e 4.01, t h e r o u t e s t o p h o t o p r o d u c t f o r m a t i o n c a n be e a s i l y d e s c r i b e d . Benzosemi-b u l l v a l e n e s 45a and 45e b o t h come from i n i t i a l v i n y l - v i n y l b o n d i n g on the b e n z o y l s i d e ( p a t h i i ) ; bond a c l e a v a g e g i v e s compound 45a and bond b c l e a v a g e g i v e s 45e. S i m i l a r l y , b e n z o s e m i b u l l v a l e n e s 45c and 45d come from i n i t i a l v i n y l - v i n y l b o n d i n g on the e s t e r s i d e ( p a t h i ) ; the r e s u l t i n g c l e a v a g e o f bond a g i v e s 45c and c l e a v a g e o f bond b y i e l d s 45d. I n i t i a l b e n z o - v i n y l b o n d i n g c a n a l s o g i v e b e n z o s e m i b u l l v a l e n e s 45d and 45e ( p a t h s i i i and i v ) . However, d e u t e r i u m s t u d i e s o f a n a l o g o u s compounds i n t h i s t h e s i s showed i n i t i a l b e n z o - v i n y l b o n d i n g i s t o o e n e r g e t i c a l l y u n f a v o r a b l e t o o c c u r . Quantum y i e l d v a l u e s f o r the f o r m a t i o n o f compounds 45a and 45c were d e t e r m i n e d t o be 0.072 ( s t d . dev. - 0.007) and 0.071 ( s t d . dev. = 0.006), r e s p e c t i v e l y ( F i g u r e 4.16). T h i s i n d i c a t e s no p r e f e r e n c e i n the s i d e o f i n i t i a l b o n d i n g , whether i t i s on t h e b e n z o y l s i d e ( p a t h i i . F i g u r e 4.01) o r the e s t e r s i d e ( p a t h i ) . compound 45a compound 45c 0.2 0.1 0.2 4> = 0.072 ( std. dev. = 0.007 ) 0 1 2 3 4 5 6 % conversion 0.1 ^ = 0.071 ( std. dev. = 0.006 ) x X X X — — J T 0 1 2 3 % conversion F i g u r e 4.16 Graph o f Quantum Y i e l d v e r s u s C o n v e r s i o n f o r Compounds 45a and 45c i n Benzene. I n the s o l i d s t a t e s t u d y , c r y s t a l s o f B e n z o b a r r e l e n e 45 were p h o t o l y z e d (A > 290 nm and A > 330 nm) and the r e s u l t i n g u nmelted sample was a n a l y z e d by NMR. Three compounds were d e t e c t e d , 45a, 45d, and 45e w i t h a r a t i o o f 10 : 45 : 45 a t c a . 32% c o n v e r s i o n . P h o t o l y s e s t o h i g h e r c o n v e r s i o n s ( c a . 73%) ca u s e s s u r f a c e m e l t i n g ; t h i s i s accompanied by an i n c r e a s e i n compound 45a f o r m a t i o n . I t i s i n t e r e s t i n g t o see a g a i n here the l a r g e d i f f e r e n c e i n c r y s t a l l i n e phase r e a c t i o n s e l e c t i v i t y compared t o s o l u t i o n . The f o r m a t i o n o f 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s i s h i g h l y f a v o r e d i n the s o l i d s t a t e . I n an e f f o r t t o e x p l a i n the o b s e r v e d r e s u l t s , t h e same two ap p r o a c h e s , used i n PART IV-A and PART IV-B, are advanced and c r i t i c a l l y d i s c u s s e d . R e c a l l t h a t t he f i r s t a p p r o a c h stems from c o n f o r m a t i o n a l e l e c t r o n i c e f f e c t s , more s p e c i f i c a l l y the degree o f c o n j u g a t i o n t h a t the c a r b o n y l has t o the a , / 9 - u n s a t u r a t i o n . I f the c a r b o n y l i s c o - p l a n a r t o the v i n y l t h e n i t can e f f i c i e n t l y s t a b i l i z e an a d j a c e n t r a d i c a l by d e l o c a l i z a t i o n . As a r e s u l t , bond a o f the f i r s t i n t e r m e d i a t e w i l l be c l e a v e d ( F i g u r e 4.01), g i v i n g 2 a , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s (45a and 4 5 c ) . C a r b o n y l s out o f c o n j u g a t i o n s h o u l d g i v e bond b c l e a v a g e t o form 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s (45d and 45e) as w e l l as t h e i r 2 a , 6 c - d i s u b s t i t u t e d c o u n t e r p a r t s . F i g u r e 4.17 C r y s t a l l i n e C o n f o r m a t i o n o f B e n z o b a r r e l e n e 45 f r o m X - r a y A n a l y s i s . The c r y s t a l l i n e c o n f o r m a t i o n o f b e n z o b a r r e l e n e 45 i s shown i n F i g u r e 4.17. The e s t e r c a r b o n y l i s i n c o n j u g a t i o n w i t h the v i n y l and the b e n z o y l c a r b o n y l i s a l m o s t c o m p l e t e l y out o f c o n j u g a t i o n w i t h the v i n y l . As a r e s u l t , t h i s a p p r o a c h w o u l d f a v o r t h e 2a,6c-d i s u b s t i t u t e d p r o d u c t (45a) from p a t h i ( F i g u r e 4.01) and t h e 1 , 2 - d i s u b s t i t u t e d p r o d u c t (45d) from p a t h i i . The o b s e r v e d r e s u l t s do somewhat show t h i s t r e n d ; compound 45d i s formed w i t h no o b s e r v a t i o n o f i t s c l e a v a g e c o m p e t i t o r 45c, and compounds 45a and 45e a r e b o t h formed. However, iso m e r 45e i s formed f o u r t i m e s as much as 45a, o p p o s i t e t o t h e p r e d i c t i o n . The a l t e r n a t i v e a p p r o a c h i s t o examine the g e o m e t r i c demands o f e ach r e a c t i o n p a t h and c o r r e l a t e t h e s e r e q u i r e d m o t i o n s w i t h s p e c i f i c c r y s t a l l a t t i c e i n t e r a c t i o n s from X - r a y d a t a . H o l d i n g t h e b e n z o - p l a n e f i x e d , the movements o f t h e b u l k y appendages a r e m o d e l l e d i n F i g u r e 4.08. However, e x a m i n a t i o n o f t h e c r y s t a l p a c k i n g i n t h i s s t r u c t u r e r e v e a l s many c o n t a c t s o f the b u l k y i s o p r o p y l s i d e - c h a i n t o t h e c r y s t a l l a t t i c e and r e l a t i v e l y few a s s o c i a t e d w i t h the b e n z o - r i n g . I n f a c t , t h e t a b l e o f i n t e r m o l e c u l a r d i s t a n c e s l e s s t h a n 3.60 Â shows a l l 25 i n t e r a c t i o n s a r e a s s o c i a t e d w i t h t h e two c a r b o n y l appendages and o n l y 2 i n v o l v e t h e benzo r i n g . F o r t h i s r e a s o n i t i s more r e a l i s t i c t o model th e l a r g e s t r e g i o n ( c a r b o n y l groups) f i x e d and o b s e r v e motions o f t h e n e x t l a r g e s t r e g i o n ( b e n z o - r i n g ) . These m o t i o n s a r e shown i n F i g u r e 4.18. The f o r m a t i o n o f 1 , 2 - d l s u b s t i t u t e d p r o d u c t s r e q u i r e s o n l y a s l i g h t s i d e w a y s movement o f the r i n g away from the s i d e o f i n i t i a l b o n d i n g . F o r m a t i o n o f 2 a , 6 c - d i s u b s t i t u t e d p r o d u c t s , on t h e o t h e r hand, r e q u i r e s a l a r g e upward t w i s t o f the b e n z o - r i n g on t h e o p p o s i n g s i d e t o i n i t i a l b o n d i n g . T h i s s i m p l e change o f r e f e r e n c e s t i l l i n d i c a t e s t h a t the m o t i o n r e q u i r e m e n t s f o r 1 , 2 - d i s u b s t i t u t e d benzo-s e m i b u l l v a l e n e f o r m a t i o n a r e much l e s s t h a n f o r i t s 2 a , 6 c - d i s u b s t i t u t e d c o u n t e r p a r t . - 1 A 2 -F i g u r e 4.18 M o t i o n s R e q u i r e d i n R e l e v a n t Di-jr-Methane Pathways, H o l d i n g the C a r b o n y l S u b s t i t u e n t s F i x e d . E x a m i n a t i o n o f t h e b e l o w 3.60 Â l a t t i c e i n t e r a c t i o n s t o the benzo-r i n g shows no s i g n i f i c a n t c l o s e c o n t a c t s . The s o l i d l i n e o f F i g u r e 4.19 r e p r e s e n t s a CHO h y d r o g e n bond (2.37 Â) between t h e two n e i g h b o r i n g b e n z o y l g r o u p s . F u r t h e r a n a l y s i s o f the p a c k i n g d i a g r a m i n F i g u r e 4.19 shows t h e i s o p r o p y l group o f an a d j a c e n t m o l e c u l e i s p o s i t i o n e d d i r e c t l y above the b e n z o - r i n g . The d o t t e d l i n e s i l l u s t r a t e t h e r e l a t i v e p o s i t i o n s o f t h e two components t h e m e t h y l s a r e measured by X - r a y a n a l y s i s t o be 3.64 Â and 4.51 Â from the b e n z o - p l a n e . R e c a l l the sum o f v a n d e r Waals r a d i i f o r t h e C H 3 • • • C d i s t a n c e i s 3.70 kJ^ The l o c a t i o n and d i s t a n c e s o f t h e s e m e t h y l groups w i l l c l e a r l y impede t h e upward t w i s t i n g m o t i o n o f the b e n z o - r i n g r e q u i r e d i n 2 a , 6 c - d i s u b s t i t u t e d p r o d u c t f o r m a t i o n (compounds 45a and 4 5 c ) . On the o t h e r hand, the r o u t e t o 1 , 2 - d i s u b s t i t u t e d p r o d u c t f o r m a t i o n (compounds 45d and 45e) w i l l n o t s h i f t the b e n z o - r i n g towards the i s o p r o p y l group, f a v o r i n g i t s f o r m a t i o n . T h i s a p p r o a c h n i c e l y r a t i o n a l i z e s t h e o b s e r v e d s e l e c t i v i t y f o r compounds 45d and 45e. F i g u r e 4.19 X - r a y P a c k i n g Arrangement o f B e n z o b a r r e l e n e 45 Shown f Two D i f f e r e n t F a c e s . The t a b l e i n F i g u r e 4.20 summarizes the r e s u l t s g a t h e r e d i n t h i s PART o f the t h e s i s . The s o l u t i o n p h o t o c h e m i c a l b e h a v i o r o f the t h r e e s u b s t r a t e s i s v e r y s i m i l a r . A l l f a v o r t h e 2 a , 6 c - d i s u b s t i t u t e d benzo-s e m i b u l l v a l e n e s g r e a t l y o v e r the 1 , 2 - d L s u b s t i t u t e d p r o d u c t s . F a c t o r s c o n t r o l l i n g s e l e c t i v i t y a r e c o n s i s t e n t w i t h t h e r a t i o n a l e b a s e d on e l e c t r o n i c s t a b i l i z i n g e f f e c t p r o v i d e d by the c a r b o n y l s , s u g g e s t e d i n PART I I I o f the t h e s i s . From the d e t e r m i n e d quantum y i e l d s , S t a r t i n g M a t e r i a l E B initial benzoyl-side bridging B E I' A T I initial ester-side bridging initial ester-side bridging B initial benzoyl-side bridging 43 E= COgMe B = benzoyl 44 B = benzoyl E = COgEt compound # 43a ( 4 3 c ) * 43h ( 4 3 b ) * 43d 43e 4 3 f s o l u t i o n (%) 34 42 12 12 0 s o l i d s t a t e (%) 0 0 50 30 20 (17% c o n v e r s i o n ) compound # 44a ( 4 4 f ) * 44c ( 4 4 b ) * 44d 44e s o l u t i o n (%) 45 42 10 3 s o l i d s t a t e (%) 54 8 23 15 (47% c o n v e r s i o n ) 45 E= C02iPr B = benzoyl compound # 45a ( 4 5 f ) * 45c ( 4 5 b ) * s o l u t i o n (%) 50 s o l i d s t a t e (%) 10 (32% c o n v e r s i o n ) 38 0 45d 45 45e 4 45 * the [1,3] shift product is included in this value. Tri-Jt-methane product. F i g u r e 4.20 T a b l e Summarizing S o l u t i o n and S o l i d S t a t e P r o d u c t R a t i o s i n t h e P h o t o c h e m i s t r y o f Compounds 43, 44, and 45. p r o d u c t s from i n i t i a l e s t e r s i d e b r i d g i n g and i n i t i a l b e n z o y l s i d e b r i d g i n g a r e formed a t about the same r a t e . W i t h r e s p e c t t o t h e t h r e e s o l i d s t a t e s t u d i e s i n t h i s PART o f the t h e s i s , i t i s i n t e r e s t i n g t o o b s e r v e t h a t a l l t h r e e , m e t h y l , e t h y l , and i s o p r o p y l d e r i v a t i v e s , p o s s e s s b a s i c a l l y t he same c r y s t a l l i n e c o n f o r m a t i o n . C o n s e q u e n t l y , the approach u s i n g c o n f o r m a t i o n a l e l e c t r o n i c e f f e c t s p r e d i c t s t h a t a l l t h r e e s u b s t r a t e s s h o u l d show s i m i l a r p r o d u c t d i s t r i b u t i o n s . T h i s i s n o t o b s e r v e d ; o n l y the e t h y l d e r i v a t i v e b o r e c o n s i s t e n c y w i t h the model. On the o t h e r hand, t h e l a t t i c e i n t e r a c t i o n a p p roach e x p l a i n e d the r e s u l t s q u i t e e f f e c t i v e l y i n a l l t h r e e c a s e s . I t i s i n t e r e s t i n g t o see t h a t e l e c t r o n i c e f f e c t s , though dominant i n s o l u t i o n c h e m i s t r y , p l a y a s e c o n d a r y r o l e i n p r o d u c t d e t e r m i n a t i o n t o s p e c i f i c l a t t i c e i n t e r a c t i o n s i n s o l i d s t a t e s e l e c t i v i t y . F u r t h e r t o t h i s m a t t e r , s u c h d i r e c t c o m p a r i s o n s have had r e c e n t l i t e r a t u r e p r e c e d e n c e . S c h e f f e r , T r o t t e r e t al.-'-^''' a l s o f o u n d t h i s i n a s t u d y o f u n s y m m e t r i c a l l y s u b s t i t u t e d d i b e n z o b a r r e l e n e s . PART V. PHOTOCHEMISTRY OF BENZOBARRELENE SALTS The t h r e e s u b s t r a t e s s t u d i e d i n t h e p r e v i o u s p a r t o f t h i s t h e s i s a l l p o s s e s s d i f f e r e n t l a t t i c e e n v i r o n m e n t s as shown from X - r a y a n a l y s i s . L a t t i c e i n t e r a c t i o n s i n a s s o c i a t i o n w i t h the r e q u i r e d r e a c t i o n geometry was d e t e r m i n e d t o be the major f a c t o r g o v e r n i n g r e a c t i o n s e l e c t i v i t y between t h e 1 , 2 - d i s u b s t i t u t e d and 2 a , 6 c - d i s u b s t i t u t e d di - 7 r-methane p r o d u c t s i n t h e s o l i d s t a t e . E x a m i n a t i o n o f the g e o m e t r i c r e q u i r e m e n t s f o r t h e s e two r e g i o i s o m e r s ( F i g u r e s 4.09 and 4.18) r e v e a l s t h a t the 2 a , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e r e q u i r e s much g r e a t e r m o t i o n f o r f o r m a t i o n t h a n i t s 1 , 2 - d i s u b s t i t u t e d c o u n t e r p a r t . R e f l e c t i n g on the o r i g i n a l c o n c e p t by Cohen,^2 d i s c u s s e d i n t h e I n t r o d u c t i o n , t h o s e r e a c t i o n s w i t h m i n i m a l changes i n geometry w i l l p r o c e e d w i t h o u t much i n t e r f e r e n c e from the s u r r o u n d i n g l a t t i c e and v i c e - v e r s a . T h e r e f o r e , the l i k e l i h o o d o f a di-jr-methane r e a r r a n g e m e n t t o 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s s h o u l d be g r e a t e r t h a n t o i t s m o t i o n demanding 2 a , 6 c - d i s u b s t i t u t e d c o m p e t i t o r . I n o r d e r t o a c c u m u l a t e e v i d e n c e t o s u p p o r t o r r e f u t e t h i s , i t woul d be i d e a l t o d e s i g n a method t o a c h i e v e many d i f f e r e n t c r y s t a l arrangements w h i l e a v o i d i n g t e d i o u s s y n t h e t i c r o u t e s and c o m p l i c a t e d s e p a r a t i o n s o f i s o m e r s . The s a l t s o f 1 , 4 - d i h y d r o - 1 , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c a c i d (40) seem a l o g i c a l c h o i c e . These compounds, shown i n F i g u r e 5.01, can be p r e p a r e d by s i m p l y r e f l u x i n g s t o i c h i o m e t r i c amounts o f d i a c i d 40 w i t h an amine o r m e t a l h y d r o x i d e . S t a n d a r d methods such as NMR, IR, and c a r b o n - h y d r o g e n a n a l y s e s were u s e d t o c h a r a c t e r i z e t h e s e compounds. C o n v e n i e n t l y , most o f t h e s e compounds a r e c r y s t a l l i n e w i t h h i g h m e l t i n g t e m p e r a t u r e s . A g a i n , t h e s o l u t i o n s t a t e p h o t o c h e m i s t r y must be i n v e s t i g a t e d f i r s t t o e n s u r e t h e c o m p l e t e n e s s o f t h e s t u d y . P h o t o p r o d u c t c h a r a c t e r i z a t i o n i s e a s i l y a c c o m p l i s h e d by c o n v e r s i o n t o t h e i r c o r r e s p o n d i n g a c i d s f o r r e f e r e n c e . R e c a l l t h a t i n the d i r e c t s o l u t i o n p h o t o l y s i s o f d i a c i d 40 ( F i g u r e 3.08), t h e s i n g l e t - m e d i a t e d [2+2] c y c l o a d d i t i o n p r o d u c t (40c) i s formed as t h e o n l y p r o d u c t and t r i p l e t p r o d u c t s (40a and 40b) a r e formed o n l y from s e n s i t i z a t i o n . C r y s t a l l i n e compound 40 g i v e s no d e t e c t a b l e p r o d u c t s from p h o t o l y s i s . The g e n e r a l p r o c e d u r e u s e d i n the s t u d y o f the s a l t s was t o p h o t o l y z e them i n a s u i t a b l e s o l v e n t and a n a l y z e the c o r r e s p o n d i n g r a t i o o f p h o t o p r o d u c t s by NMR s i g n a l i n t e g r a t i o n . P h o t o p r o d u c t c h a r a c t e r i z a t i o n i s e a s i l y a c c o m p l i s h e d by c o n v e r s i o n t o t h e i r c o r r e s p o n d i n g d i a c i d s f o r r e f e r e n c e . I n a s i m i l a r f a s h i o n , s o l i d s t a t e s t u d i e s were c a r r i e d out i n n i t r o g e n f i l l e d NMR tub e s and the p h o t o p r o d u c t r a t i o s were d e t e r m i n e d by NMR a n a l y s i s o f t h e d i s s o l v e d r e a c t i o n m i x t u r e . Figure 5.01 Photochemistry of Benzobarrelene S a l t s . The s o l u t i o n r e s u l t s a r e l i s t e d i n F i g u r e 5.02 t o show the r e l a t i v e r a t i o s o f c y c l o o c t a t e t r a e n e 40c, b e n z o s e m i b u l l v a l e n e 40a, and benzosemi-b u l l v a l e n e 40b s a l t s . The p h o t o l y s e s were c a r r i e d o u t t o i n c o m p l e t e c o n v e r s i o n i n o r d e r t o m i n i m i z e f o r m a t i o n o f s e c o n d a r y p h o t o p r o d u c t s . I t was n o t i c e d t h a t a g r e a t e r p r o p o r t i o n o f t r i p l e t p r o d u c t s a r e formed from d i r e c t p h o t o l y s i s o f the amine s a l t s t h a n from d i r e c t p h o t o l y s i s o f d i a c i d 40. Compound T r i a l S o l v e n t % s t a r t i n g m a t e r i a l 0 % COT 0 % 1.2-sub % 2a.6c A8 1 C D C I 3 54 36 10 0 ( e x t r a c t e d ) (35) (55) (10) (0) 2 C D C I 3 63 30 7 0 3 C D C I 3 56 53 11 0 49 1 C D C I 3 43 47 10 0 ( e x t r a c t e d ) (19) (70) (11) (0) 2 C D C I 3 64 31 5 0 50 1 C D C I 3 37 53 10 0 ( e x t r a c t e d ) (15) (70) (15) (0) 2 C D C I 3 62 31 7 0 51 1 DMSO-dg 69 8 20 3 ( e x t r a c t e d ) (61) (8) (27) (4) 2 DMSO-dg 40 9 45 6 52 1 D2O 83 11 0 2 ( e x t r a c t e d ) (87) (11) (0) (2) 2 D2O 72 28 0 0 53 1 D 2 O 81 19 0 0 ( e x t r a c t e d ) (79) (21) (0) (0) 2 D2O 58 42 0 0 54 1 C D C I 3 15 61 22 2 ( e x t r a c t e d ) (9) (83) (8) (0) 2 C D C I 3 79 7 14 0 F i g u r e 5.02 P h o t o p r o d u c t R a t i o s from the S o l u t i o n Phase P h o t o c h e m i s t r y o f B e n z o b a r r e l e n e S a l t s . I t has been r e p o r t e d t h a t c a r b o n y l s o f s a l t s have a l e s s e r c a p a c i t y to resonan c e s t a b i l i z e an a d j a c e n t r a d i c a l t h a n the c a r b o n y l s o f c a r b o x y l i c a c i d s . 9 ^ T h i s i s because the c a r b o n y l s a r e more i n v o l v e d i n d e l o c a l i z a t i o n o f the e x i s t i n g n e g a t i v e c h a r g e . An example o f t h i s e f f e c t i n p h o t o c h e m i s t r y i s shown i n F i g u r e 3.12 w i t h a c i d / e s t e r 66.^^ P h o t o l y s i s o f the sodium s a l t o f 66 i n c r e a s e s the f o r m a t i o n o f 66b, t h e p r o d u c t from a di-7r-methane pathway t h a t does n o t p l a c e a r a d i c a l a d j a c e n t t o the c a r b o n y l o f the s a l t . The r e d u c e d a b i l i t y t o resona n c e s t a b i l i z e an a d j a c e n t r a d i c a l s h o u l d , from t h e r a t i o n a l f o r w a r d e d i n PART I I I o f t h i s t h e s i s , i n c r e a s e 1 , 2 - d i s u b s t i t u t e d p r o d u c t f o r m a t i o n r e l a t i v e t o 2 a , 6 c - d i s u b s t i t u t e d p r o d u c t f o r m a t i o n . The r a t i o o f 1,2- t o 2 a , 6 c - d i s u b s t i t u t i o n s h o u l d be g r e a t e r t h a n t h a t o f t h e d i a c i d (4 : 6 ) . The t a b l e o f r e s u l t s ( F i g u r e 5.02) shows t h a t s e l e c t i v i t y between the two t r i p l e t p r o d u c t s i s c o n s i s t e n t w i t h the model by f a v o r i n g the 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e o v e r t h e 2 a , 6 c - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e i n a l l c a s e s . These r e s u l t s , i n t u r n , f u r t h e r s u p p o r t the p r o p o s e d r a t i o n a l i n PART I I I o f t h i s t h e s i s . I n an e f f o r t t o reduce the amount o f s i n g l e t p r o d u c t formed from d i r e c t p h o t o l y s i s , m o n o - s a l t 54 was s y n t h e s i z e d w i t h t h e i d e a t h a t a b e n z o y l a n a l o g c o u l d be s e l e c t i v e l y e x c i t e d and i n t e r n a l l y t r a n s f e r t r i p l e t e n ergy t o t h e b a r r e l e n e r e a c t a n t . W i t h some s u c c e s s , p h o t o l y s i s (A > 330 nm) gave enhanced t r i p l e t p r o d u c t f o r m a t i o n . L a r g e m e t a l c a t i o n s have s t r o n g s p i n - o r b i t c o u p l i n g e f f e c t s and can a s s i s t i n i n t e r s y s t e m c r o s s i n g t o the t r i p l e t e x c i t e d s t a t e . •'-^^ I n l i g h t o f t h i s , heavy m e t a l s a l t s 52 and 53 were a l s o s y n t h e s i z e d and c r y s t a l l i z e d f o r p h o t o l y s i s ; however, p r o d u c t r a t i o s r e v e a l a v e r y low p e r c e n t a g e o f t r i p l e t p r o d u c t f o r m a t i o n i n c o m p a r i s o n t o the amine s a l t s . T h i s shows t h a t the l a r g e m e t a l c a t i o n s u s e d h e r e a r e i n e f f e c t i v e i n f a c i l i t a t i n g i n t e r s y s t e m c r o s s i n g t o the t r i p l e t o f the s u b s t r a t e s . I n o r d e r t o c o n f i r m the p h o t o p r o d u c t a s s i g n m e n t s , t h e r e a c t i o n m i x t u r e was r e - a c i d i f i e d , the c o u n t e r c a t i o n e x t r a c t e d , and the r e s u l t i n g d i a c i d m i x t u r e a n a l y z e d by NMR. F i g u r e 5.02 shows t h a t t h e p r o d u c t r a t i o changes v e r y l i t t l e f r om p r e - e x t r a c t i o n t o p o s t - e x t r a c t i o n . A t y p i c a l NMR e x p a n s i o n o f the r e a c t i o n m i x t u r e and e x t r a c t e d m i x t u r e i s shown i n F i g u r e 5.03. T h i s r e g i o n shows t h a t t h e p r o t o n s i g n a l s o f t h e f o u r compounds a r e w e l l s e p a r a t e d a l l o w i n g f o r a c l e a r i n t e g r a t i o n t o e s t a b l i s h component r a t i o s . T u r n i n g t o the u n d e r l y i n g r e a s o n f o r t h i s i n v e s t i g a t i o n , c r y s t a l s o r powders o f a l l t h e s a l t s were p h o t o l y z e d w i t h a medium p r e s s u r e mercury lamp. A g a i n , t h e r a t i o s were d e t e r m i n e d by NMR and th e s i g n a l s c a n e a s i l y be i d e n t i f i e d by c o m p a r i s o n w i t h the s o l u t i o n r e s u l t s . a) 7*s 7.1 i . r . s .ê h.i s .a ppm b) aromatic J 41d 4fîb 4Û '••s ^Ti r» s's 7i 7i 71 Til ZI 7i 71 7~, 1^  ppm F i g u r e 5.03 NMR S p e c t r a o f the S a l t 48 R e a c t i o n M i x t u r e i n C D C I 3 : a) B e f o r e E x t r a c t i o n . b) A f t e r R e - a c i d i f i c a t i o n . o c s ©ïiCox ^ ™ % s t a r t i n g Compound Phase m a t e r i a l % COT % 1.2-sub % 2a.6c-sub comment 48 c r y s t a l 85 12 3 0 brown, (mp = 164°C) 74 21 5 0 no m e l t 70 21 9 0 49 c r y s t a l 88 4 8 0 brown, (mp = 187°C) 84 4 12 0 no m e l t 50 c r y s t a l 67 20 13 0 brown, (decomp.= 90°C) 66 22 12 0 m e l t e d 51 c r y s t a l 88 10 0 2 brown, (mp = 238°C) 88 7 0 5 no m e l t 52 c r y s t a l 87 12 1 0 brown. (mp > 300°C) 83 15 2 0 no m e l t 53 c r y s t a l 73 27 0 0 brown. (mp > 300°C) 14 86 0 0 no m e l t 54 s o l i d 96 0 4 0 brown. (mp = 113°C) 97 0 3 0 no m e l t F i g u r e 5.04 P h o t o p r o d u c t R a t i o s from t h e S o l i d S t a t e S t u d y o f Benzo-b a r r e l e n e S a l t s . The s o l i d s t a t e p h o t o r e a c t i v i t y o f t h e s e s a l t s does s u p p o r t the h y d r o g e n b o n d i n g t h e o r y o f d i a c i d 40 o u t l i n e d i n PART I I I - B o f t h i s t h e s i s . R e c a l l t h a t d i a c i d 40 g i v e s no d e t e c t a b l e p h o t o p r o d u c t s i n the s o l i d s t a t e and t h a t the p r o p o s e d r e a s o n f o r t h i s stems from the a n c h o r i n g o f t he a c i d p r o t o n s t o the l a t t i c e t h r o u g h h y d r o g e n b o n d i n g ( F i g u r e 3.11). T h i s hydrogen b o n d i n g i s r e d u c e d i n m o n o - s a l t s and removed i n d i s a l t s ; as a r e s u l t , t h e r e i s more movement a l l o w e d i n t h e c r y s t a l l a t t i c e f o r r e a c t i o n . F i g u r e 5.04 shows t h a t the c r y s t a l l i n e s a l t s s t u d i e d a r e a l l r e a c t i v e i n t h e s o l i d s t a t e . A l t h o u g h c r y s t a l a n a l y s i s d a t a i s n o t a v a i l a b l e f o r c o m p a r i s o n , the f i n d i n g t h a t 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e f o r m a t i o n i s f a v o r e d o v e r i t s 2 a , 6 c - d i s u b s t i t u t e d i s o m e r i n a l m o s t a l l c a s e s i s v e r y s u p p o r t i v e t o Cohen's h y p o t h e s i s e ^ t h a t l e s s m o t i o n demanding r e a c t i o n pathways a r e g e n e r a l l y f a v o r e d o v e r more m o t i o n demanding ones i n the s o l i d s t a t e . S a l t s w i t h the most i n t e r e s t i n g s o l i d s t a t e b e h a v i o r a r e t h o s e w i t h e t h y l e n e d i a m i n e (51) and 3'-aminoacetophenone ( 5 4 ) ; I n s o l u t i o n , b e n z o b a r r e l e n e 51 forms t h e 1 , 2 - d i s u b s t i t u t e d p r o d u c t s e v e n t i m e s more e f f i c i e n t l y t h a n the 2 a , 6 c - d i s u b s t i t u t e d compound ( F i g u r e 5.02); however, the s o l i d s t a t e e x c l u s i v e l y f a v o r s t h e f o r m a t i o n o f the l a t t e r ( F i g u r e 5.04). W i t h o u t t h e a i d o f an X - r a y a n a l y s i s , i t i s i m a g i n e d t h a t s p e c i f i c l a t t i c e i n t e r a c t i o n s a r e r e s p o n s i b l e f o r t h e r e a c t i o n t o s e l e c t the more m o t i o n pathway o v e r the l e s s e r m o t i o n r o u t e . The c h r o m o p h o r i c amino s a l t (54) was d e s i g n e d t o i n t e r n a l l y t r i p l e t s e n s i t i z e t h e r e a c t i o n . A l t h o u g h a r e l a t i v e l y l a r g e r amount o f t r i p l e t p r o d u c t s i s formed from s o l u t i o n p h o t o l y s i s , the major p r o d u c t i s s t i l l t he s i n g l e t -m e d i a t e d s a l t o f c y c l o o c t a t e t r a e n e 40c. I n t h e s o l i d s t a t e , however, th e o n l y o b s e r v e d p r o d u c t i s the t r i p l e t 1 , 2 - d i s u b s t i t u t e d p r o d u c t . I t i s s t i l l n o t c l e a r as t o whether the cause o f t h i s t r i p l e t s e l e c t i v i t y i s from i n t e r n a l s e n s i t i z a t i o n o r f rom t h e l a t t i c e f o r b i d d i n g the s i n g l e t [2+2] r e a c t i o n i n the s o l i d s t a t e . As seen c u m u l a t i v e l y from t h i s and o t h e r s t u d i e s i n t h i s t h e s i s , t h e b e n z o b a r r e l e n e system p r o v i d e s a s e n s i t i v e measure o f l a t t i c e e f f e c t s i n s o l i d s t a t e r e a c t i o n s . S l i g h t s t e r i c f a c t o r s c a n e a s i l y f a v o r one r e a c t i o n pathway o v e r a n o t h e r . Such a s y s t e m i s u s e f u l f o r f u r t h e r s t r u c t u r e - r e a c t i v i t y s t u d i e s t o e n a b l e s c i e n t i s t s t o d e v e l o p a g e n e r a l system o f q u a n t i t a t i v e l y p r e d i c t i n g t h e degree o f s o l i d s t a t e s e l e c t i v i t y f r o m a l a t t i c e d e s i g n . PART VI. PHOTOCHEMISTRY OF DIMETHYL 1,4-DIHYDRO-l,4,5,8-TETRAMETHYL-l.4-ETHENONAPHTHALENE-2,3-DICARBOXYLATE (47) The r e c e n t o b s e r v a t i o n o f a t r i - 7 r - m e t h a n e ^ ^ r e a r r a n g e m ent i n b r i d g e h e a d s u b s t i t u t e d d i b e n z o b a r r e l e n e s ^ u r g e d t h e s t u d y o f t e t r a m e t h y l b e n z o b a r r e l e n e 47 f o r the p r e s e n c e o f t h i s r e a r r a n g e m e n t . The r e p l a c e m e n t o f b r i d g e h e a d p r o t o n s o f some d i b e n z o b a r r e l e n e s w i t h o t h e r groups such as C H 2 C I , CI, m e t h y l , o r p h e n y l r e s u l t s i n t h i s u n u s u a l b e h a v i o r . P h o t o p r o d u c t s o b s e r v e d from t h e tri-^r-methane r e a r r a n g e m e n t o f d i b e n z o b a r r e l e n e s a r e shown i n F i g u r e 0.27, p r o d u c t s a r e c y c l o o c t a t e t r a e n e s w i t h C2 axes o f symmetry and p e n t a l e n e - l i k e compounds. The u n d e r l y i n g r e a s o n f o r t h i s i s o m e r i z a t i o n b e i n g f a v o r e d o v e r t he di-7r-me thane r e a r r a n g e m e n t was s u g g e s t e d t o be due t o s t e r i c e f f e c t s combined w i t h r a d i c a l s t a b i l i z a t i o n f rom t h e added t e r t i a r y c e n t e r s ; however, c o n f i d e n c e i n t h e s e r a t i o n a l e s demands s u p p o r t . I n an e f f o r t t o b e t t e r u n d e r s t a n d t h i s phenomenon, t h e mono-benzo a n a l o g was s y n t h e s i z e d t o d e t e r m i n e t he g e n e r a l i t y o f t h i s r e a c t i o n . The s y m m e t r i c a l 1 , 4 , 5 , 8 - t e t r a m e t h y l -n a p h t h a l e n e was u s e d i n s t e a d o f 1 , 4 - d i m e t h y l n a p h t h a l e n e as t h e d i e n e i n t h e D i e l s - A l d e r s y n t h e s i s o f the b r i d g e h e a d - s u b s t i t u t e d s t a r t i n g m a t e r i a l . T h i s compound was chosen i n o r d e r t o i n c r e a s e t he y i e l d o f t h e d e s i r e d a d d u c t and t o a v o i d a t e d i o u s c h r o m a t o g r a p h i c s e p a r a t i o n ; d i m e t h y l n a p h t h a l e n e w o u l d p r e s u m a b l y add t o d i m e t h y l a c e t y l e n e d i c a r b o x y l a t e t o g i v e a m i x t u r e o f two r e g i o i s o m e r s . D i r e c t p h o t o l y s i s o f compound 47 (À > 290 nm) i n benzene o r a c e t o n i t r i l e t o complete c o n v e r s i o n l e d t o two maj o r p h o t o p r o d u c t s . (47a and 47b, F i g u r e 6.01). However, a s e c o n d a r y p h o t o p r o d u c t (47c) from compound 47b i s o b s e r v e d a t h i g h e r c o n v e r s i o n s ( c a . 4 5 % ) . T h i s r e a c t i o n b e h a v i o r i s ind e p e n d e n t o f s o l v e n t . The t h r e e compounds were s u b s e q u e n t l y i s o l a t e d by column chromatography from a p r e p a r a t i v e s c a l e p h o t o l y s i s . F i g u r e 6.01 P h o t o c h e m i s t r y o f D i m e t h y l T e t r a m e t h y l b e n z o b a r r e l e n e D i e s t e r ( 4 7 ) . P r e v i o u s b e n z o s e m i b u l l v a l e n e r i n g systems d e s c r i b e d i n t h i s t h e s i s were e a s i l y c h a r a c t e r i z e d by t h e i r s i g n a l p a t t e r n s i n the NMR spectrum. However, the r e p l a c e m e n t o f t h e s e p r o t o n s w i t h m e t h y l s d e s t r o y s the c o u p l i n g , r e s u l t i n g i n a s e r i e s o f s i n g l e t s . I d e n t i f i c a t i o n i s , t h e r e f o r e , more c h a l l e n g i n g . The NMR s p e c t r a o f the b e n z o b a r r e l e n e s t a r t i n g m a t e r i a l and i t s p h o t o p r o d u c t s a r e shown i n F i g u r e s 6.02 and 6.03. V a r i o u s NMR t e c h n i q u e s s u c h as APT and NOE were employed; however, t h e s t r u c t u r e o f 47a was c o n f i r m e d t o be d i m e t h y l 2 a , 2 b - d i h y d r o - 1 , 2 b , 3 , 6 - t e t r a m e t h y l b e n z o [ a ] c y c l o p r o p a [ c d ] -p e n t a l e n e - 6 b , 6 c - d i c a r b o x y l a t e and 47b was c o n f i r m e d t o be d i m e t h y l 1 , 4 , 6 , 9 - t e t r a m e t h y l b e n z o [ a ] c y c l o o c t e n e - 5 , 1 0 - d i c a r b o x y l a t e from X - r a y a n a l y s e s . P h o t o l y s e s o f c y c l o o c t a t e t r a e n e 47b i n benzene o r a c e t o n e (A > 290 nm) l e d t o co m p l e t e c o n v e r s i o n t o b e n z o s e m i b u l l v a l e n e 47c. The r e a c t i o n i n a c e t o n e was n o t i c e d t o be much f a s t e r . W i t h knowledge o f the p r e c u r s o r s t r u c t u r e and f a m i l i a r i t y w i t h the r e a c t i o n sequence i n v o l v e d , compound 47c was a s s i g n e d by NMR ( F i g u r e 6.03) t o be d i m e t h y l 2 a , 6 c - d i h y d r o - l , 2 a , 3 , 6 -t e t r a m e t h y I b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 2b, 6 b - d i c a r b o x y l a t e . T h i s compound i s s u g g e s t e d t o be a t e r t i a r y p h o t o p r o d u c t o f b e n z o b a r r e l e n e 47 and a s e c o n d a r y p h o t o p r o d u c t o f b e n z o c y c l o o c t a t e t r a e n e 47b. A p r o b a b l e r e a c t i o n sequence i s t h a t compound 47b undergoes an i n i t i a l i n t r a m o l e c u l a r [2-t-2] c y c l o a d d i t i o n t o form a c y c l o b u t e n e ( F i g u r e 6.05). T h i s c y c l o b u t e n e i s a di-jr-methane system, and t h r o u g h a b s o r p t i o n o f a n o t h e r p h o t o n , undergoes the t r i p l e t - m e d i a t e d r e a c t i o n t o the p r o d u c t . R e c a l l t h i s r e a c t i o n sequence has been r e p o r t e d w i t h many o f Bender's s t u d i e s ^ ^ ' ' ' •'-•'-^  as w e l l as b e i n g o b s e r v e d w i t h b e n z o c y c l o o c t a t e t r a e n e 29d i n PART I I I A o f t h i s t h e s i s . F i g u r e 6.03 NMR S p e c t r a o f B e n z o b a r r e l e n e 47 and B e n z o s e m i b u l l v a l e n e 47c i n C D C I 3 . T r i p l e t - s e n s i t i z a t i o n o f b e n z o b a r r e l e n e 47 u s i n g a t w o - f o l d m o l a r e x c e s s o f benzophenone (A > 330 nm, s u b s t r a t e i s t r a n s p a r e n t i n t h i s r e g i o n ) gave c o m p l e t e c o n v e r s i o n o f s t a r t i n g m a t e r i a l t o two p r o d u c t s i n an a p p r o x i m a t e r a t i o o f 1 : 1.5 = 47a : 47d. Compound 47d was u n i d e n t i f i e d as i t i s i n s e p a r a b l e by column chromatography and r e a d i l y decomposes t o o t h e r unknown compounds upon s t a n d i n g . GC-MS on t h e r e a c t i o n m i x t u r e shows the same p a r e n t mass as 47; however, a t t e m p t s t o q u a n t i f y i t u s i n g NMR on t h e m i x t u r e were u n s u c c e s s f u l . I t i s t h o u g h t t h a t t h i s unknown t r i p l e t p r o d u c t (47d) may p o s s i b l y be m e t h y l 2 b , 6 b - d i h y d r o -2b , 3 , 6 , 6 b - t e t r a m e t h y l b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 2 a , 6 c - d i c a r b o x y l a t e ( F i g u r e 6.04), the e x p e c t e d 2 a , 6 c - d i s u b s t i t u t e d p r o d u c t from a di - T T-methane r e a r r a n g e m e n t . I t s a p p a r e n t i n s t a b i l i t y i s u n d e r s t a n d a b l e n o t o n l y from t h e i n t e r n a l s t e r i c s t r a i n o f the two p a i r s o f m e t h y l s u b s t i t u e n t s F i g u r e 6.04 b u t S c h e f f e r ' s r e s e a r c h group-'--'-^ has f o u n d t h a t s e m i b u l l v a l e n e s w i t h s u b s t i t u e n t s on a l l t h r e e a v a i l a b l e p o s i t i o n s o f the c y c l o p r o p y l r i n g ( F i g u r e 6.04) r e a d i l y undergo s e c o n d a r y p r o c e s s e s . T h i s i n h e r e n t i n s t a b i l i t y may a l s o be due t o i n t e r n a l s t e r i c s t r a i n . M o l e c u l a r m o d e l l i n g calculations-'--'-^ show the C---C d i s t a n c e s o f the s u b s t i t u t e n t s on the r i n g t o be v e r y s h o r t ( F i g u r e 6.04), i n d i c a t i n g a tremendous s t r a i n . 3.06A E = C O 2 C H 3 F i g u r e 6.04 P r o p o s e d S t r u c t u r e f o r 47d w i t h A n a l o g y Showing I n h e r e n t I n s t a b i l i t y o f Such B e n z o s e m i b u l l v a l e n e s B e a r i n g Three S u b s t i t u t e n t s on t h e C y c l o p r o p y l R i n g . C r y s t a l l i n e phase p h o t o l y s i s o f compound 47 u s i n g e i t h e r a medium p r e s s u r e mercury lamp o r a n i t r o g e n l a s e r (A = 337 nm) gave two p r o d u c t s ; compound 47a was formed as the major p r o d u c t , 10 : 1 (by NMR) o v e r compound 47b a t a c a . 11 % c o n v e r s i o n . H i g h e r c o n v e r s i o n s r e s u l t i n s u r f a c e m e l t i n g o f the c r y s t a l . B e n z o s e m i b u l l v a l e n e 47a i s s u g g e s t e d t o come from the i n t e r e s t i n g t r i - T T - m e t h a n e rearrangement shown i n F i g u r e 6.05. R e c a l l t h a t t h i s p r o d u c t i s a n a l o g o u s t o a minor p r o d u c t ( 4 3 f ) formed i n t h e s o l i d s t a t e p h o t o l y s i s o f b e n z o b a r r e l e n e 43 ( F i g u r e 4.06), b u t t h i s t i m e i t i s a major p r o d u c t from d i r e c t , t r i p l e t - s e n s i t i z e d , and c r y s t a l l i n e phase p h o t o l y s i s o f t h e s t a r t i n g m a t e r i a l . As t h i s p r o d u c t i s formed i n c o n j u n c t i o n w i t h d i f f e r i n g p h o t o p r o d u c t s under b o t h d i r e c t p h o t o l y s i s and t r i p l e t s e n s i t i z a t i o n , i t c a n be s u g g e s t e d t h a t the r e a c t i o n p r o c e e d s t h r o u g h b o t h t h e s i n g l e t and t r i p l e t e x c i t e d s t a t e s . The i n i t i a l b r i d g e f o r m a t i o n , v i n y l - v i n y l o r b e n z o - v i n y l , i s s t i l l u n c e r t a i n . However, b o t h bonds a r e n o t l i k e l y t o form a t t h e same time as Zimmerman-*-^ has p o i n t e d o u t t h a t the energy r e q u i r e m e n t f o r s u c h p r o c e s s e s a r e h i g h l y u n f a v o r a b l e i n the case o f b a r r e l e n e i t s e l f . There a r e s e v e r a l d i f f e r e n c e s between t h e t r i - T T - m e t h a n e r e a r r a n g e m e n t s o f monobenzobarrelenes and d i b e n z o b a r r e l e n e s . P r i m a r i l y , u n s y m m e t r i c a l d i b e n z o c y c l o o c t a t e t r a e n e s and p e n t a l e n e - l i k e compounds a r e t h e p r o d u c t s from d i b e n z o b a r r e l e n e s ( F i g u r e 0.27); c o r r e s p o n d i n g l y , b e n z o s e m i b u l l v a l e n e s a r e formed from m o n o b e n z o b a r r e l e n e s ( F i g u r e 6.05). T h i s i s e a s i l y r a t i o n a l i z e d ; once the t r i - T T - m e t h a n e b r i d g e s a r e formed, t h e subsequent s t e p s a r e s e l e c t e d a l o n g the p o t e n t i a l e nergy s u r f a c e s u c h t h a t , b r a n c h by b r a n c h , t h e most e n e r g e t i c a l l y f a v o r a b l e i n t e r m e d i a t e s a r e formed. Two bond c l e a v a g e s t o r e g e n e r a t e a r o m a t i c i t y i n the two benzo groups o f t h e d i b e n z o - r e a c t i o n a r e e s s e n t i a l i n the second s t e p ( F i g u r e 0.27). The r e s u l t i n g b i r a d i c a l can t h e n b r a n c h t o g i v e b o t h t h e u n s y m m e t r i c a l c y c l o o c t a t e t r a e n e and the p e n t a l e n e - l i k e compound. I n c o n t r a s t , o n l y one bond i s r e q u i r e d t o b r e a k t o r e g a i n a r o m a t i c i t y i n t h e c a s e o f t h e mono-benzo system as t h e r e i s o n l y one a r o m a t i c r i n g d i s r u p t e d ; i n the same s t e p , the r a d i c a l s can e a s i l y p a i r t o form a b e n z o s e m i b u l l v a l e n e . A two bond c l e a v a g e t o g i v e the d i b e n z o - t y p e p r o d u c t s r e q u i r e s too much energy. The o t h e r major p h o t o p r o d u c t from d i r e c t p h o t o l y s i s , b e n z o c y c l o -o c t a t e t r a e n e 47b, comes from a b e n z o - v i n y l [2+2] i n t r a m o l e c u l a r c y c l o a d d i t i o n f o l l o w e d by a t h e r m a l r i n g o p e n i n g ( F i g u r e 6.05). T h i s r e a c t i o n i s s i n g l e t - m e d i a t e d as the compound i s n o t o b s e r v e d under t r i p l e t s e n s i t i z a t i o n . No c y c l o o c t a t e t r a e n e from the v i n y l - v i n y l [2+2] r e a c t i o n was d e t e c t e d . F i g u r e 6.05 Proposed Mechanisms t o P h o t o p r o d u c t F o r m a t i o n f r o m Benzo-b a r r e l e n e 47. Two r a t i o n a l e s can be f o r w a r d e d t o e x p l a i n the p r e f e r e n c e f o r t h e t r i - I T - m e t h a n e r e a r r a n g e m ent o v e r t h e di - 7 r-methane r e a c t i o n . The f i r s t r a t i o n a l e i s b a s e d on t h e p o s s i b i l i t y o f a c h a r g e - t r a n s f e r p r o c e s s whereby a w - e l e c t r o n o f t h e benzo group donates t o t h e d i s u b s t i t u t e d v i n y l a c c e p t o r . T h i s i n e s s e n c e w o u l d e x p l a i n t h e s e l e c t e d b e n z o - v i n y l b r i d g i n g o v e r v i n y l - v i n y l b r i d g i n g ; u n s u b s t i t u t e d v i n y l s a r e e x t r e m e l y p o o r e l e c t r o n donors ^ I f i n d e e d a c h a r g e - t r a n s f e r was i n v o l v e d , t h e r e a c t i o n may be s o l v e n t dependent. •'-•'•^  Quantiam y i e l d s f o r the f o r m a t i o n o f compounds 47a and 47b were d e t e r m i n e d i n b o t h benzene and a 1 : 1 m i x t u r e o f a c e t o n i t r i l e and benzene ( F i g u r e 6.06) and showed no dependency t o s o l v e n t p o l a r i t y . Charge - t r a n s f e r complexes commonly have c h a r a c t e r i s t i c a b s o r p t i o n bands above 400 nm.-'--'-^  An u l t r a v i o l e t a b s o r p t i o n s t u d y u s i n g a range o f s u b s t r a t e c o n c e n t r a t i o n s e x h i b i t e d no bands above 400 nm. A l s o c h a r g e - t r a n s f e r complexes c a n have c h a r a c t e r i s t i c f l u o r e s c e n c e s p e c t r a , a b r o a d f e a t u r e l e s s band i n t h e n e a r U V - v i s i b l e r e g i o n . •'-•'-^  F l u o r e s c e n c e s t u d i e s were a l s o c o n d u c t e d t o show a v e r y weak e m i s s i o n bands a t 335 nm, 350 nm, 367 nm, f o l l o w e d by a t a i l t o 480 nm from e x c i t a t i o n a t 281 nm. The p r e s e n c e o f a c h a r g e -t r a n s f e r remains u n s u p p o r t e d . in Benzene in Benzene and Acetonitrile (1:1 ) 0) 0.2 0.1 <t> = 0.135 ( std. dev. = 0.008 ) -©-<l> = 0.11 ( std. dev. = 0.01 ) 4Zb 2 4 6 % conversion 0.2 0.1 0 = 0.125 ( std.dev. = 0.009 ) X ^ J O o <ï> = 0.100 ( std. dev. = 0.006 ) 4Zb -o 0 2 4 6 % conversion Figure 6.06 Quantxim Y i e l d Graphs for the Formation of P h o t o p r o d u c t s 47a and 47b i n Benzene and a 1:1 M i x t u r e o f A c e t o n i t r i l e and Benzene. The second approach i s from s t e r i c c o n s i d e r a t i o n s . T h i s i s one o f the methods used t o r a t i o n a l i z e the d i b e n z o r e s u l t s . A l t h o u g h s t e r i c e f f e c t s were not emphasized i n t h e i r r a t i o n a l e , t h i s a p p r o a c h i s t h o u g h t t o p l a y a v e r y l a r g e r o l e toward p r o d u c t s e l e c t i v i t y i n t h i s s i t u a t i o n . X - r a y a n a l y s i s o f the s t a r t i n g m a t e r i a l shows t h a t the b r i d g e h e a d methyls and the benzo m e t h y l s a r e i n t r a m o l e c u l a r l y pushed a g a i n s t each o t h e r ( F i g u r e 6.07). The d e t e r m i n e d C-C d i s t a n c e f o r Cj j^^  t o Cj^g i s 2.963(5) Â and C]^g t o is 3.013(6) Â. These a r e r e m a r k a b l y l e s s than the sum o f t h e i r v a n d e r Waals r a d i i (3.40 Â ) . ^ ^ T h i s s t r a i n was f i r s t n o t i c e d from the a n g l e s o f the me t h y l s on t h e a r o m a t i c r i n g , b e n t a w a y f r o m t h e b r i d g e h e a d m e t h y l s . A n a d d e d c o n s e q u e n c e o f t h i s s t r a i n i s t h e l e n g t h e n i n g o f t h e C ^ - C g ^ a n d t h e b o n d s , 1 . 3 6 6 ( 3 ) A a n d 1 . 5 6 1 ( 3 ) Â . A t y p i c a l l e n g t h f o r a n s p ^ - s p - ^ b o n d i s 1 . 5 ^ .". ; s p ^ - . s p ' ' bo::d.s a r e e v e n s h o r t c - r . 1 , 5 0 A . ^ ' - F r o m m o l e c u l a r models, the t w i s t i n g o f the m o l e c u l e i n tri-n--methane b r i d g i n g r e d u c e s the s t e r i c s t r a i n on the m e t h y l s . C r y s t a l l o g r a p h i c a n a l y s i s o f t he r e s u l t i n g p r o d u c t (47a) shows t h a t t h e m e t h y l s a r e n o t as s t r a i n e d ; o n l y one m e t h y l - m e t h y l i n t e r a c t i o n i s p r e s e n t , between the m e t h y l s on C21, and C 3 ( d i s t . = 3.187(7) Â, F i g u r e 6.02). I n t r a m o l e c u l a r A t o m i c D i s t a n c e s bond d i s t a n c e (Â) C i - C 2 1.538(3) C^-Cga 1.566(3) Cx-Cg 1.530(4) C ^ - C i i 1.521(4) C 3 - C 4 1.540(4) C 4 - C 4 3 1.561(3) C 4 - C 1 0 1.530(4) C 4 - C 1 6 1.531(4) C5-Ci^7 1.501(5) Cg-C i s 1.504(4) I n t r a m o l e c u l a r A n g l e s a n g l e degi rees C4a C 4 C 1 6 120 .0(2) C4a C 5 C l 7 127 .3(3) C7 C8 ^18 116 .4(2) C8a C8 ^18 127 .4(2) C8a C l Cu 118 .5(2) Cg C l C l l 110 .2(2) ^10 C 4 C 1 6 110 .2(3) F i g u r e 6.07 C r y s t a l S t r u c t u r e o f B e n z o b a r r e l e n e 47 Showing S e l e c t e d Bond Le n g t h s and A n g l e s . S i m i l a r l y , t h e s e m e t h y l - m e t h y l i n t e r a c t i o n s a r e t h o u g h t t o be r e s p o n s i b l e f o r f o r m a t i o n o f the o b s e r v e d b e n z o c y c l o o c t a t e t r a e n e ( 4 7 b ) . A l t h o u g h v i n y l - v i n y l c y c l o a d d i t i o n does n o t d i s r u p t b e n z o - a r o m a t i c i t y , i t w i l l , from m o l e c u l a r m o d e l l i n g c a l c u l a t i o n s , ^ - ' - ^ t h r u s t t h e b r i d g e h e a d m e t h y l s towards t h e a r o m a t i c m e t h y l s t h e r e b y i n c r e a s i n g t e n s i o n ( p a t h i , F i g u r e 6.08). T h i s i n c r e a s e d t e n s i o n c o u l d e a s i l y d e t e r t h e r e a c t i o n by i n c r e a s i n g the r e q u i r e d a c t i v a t i o n e n e r g y f o r p r o d u c t f o r m a t i o n . B e n z o - v i n y l c y c l o a d d i t i o n , on t h e o t h e r hand, w i l l r e l i e v e some s t e r i c s t r a i n ( p a t h i i ) . C o n s i s t e n t w i t h c r y s t a l l o g r a p h i c d a t a , the c a l c u l a t e d m e t h y l - m e t h y l d i s t a n c e s from t h e m o d e l l i n g program-'--'-^ a r e about 3.0 Â. G o i n g t o t h e v i n y l - v i n y l b r i d g e d s p e c i e s , the c a l c u l a t e d m e t h y l - m e t h y l d i s t a n c e s a r e r e d u c e d t o about 2.9 Â; whereas, b e n z o - v i n y l b r i d g i n g i n c r e a s e s the c a l c u l a t e d m e t h y l - m e t h y l d i s t a n c e s t o about 3.1 Â. T h i s r e a s o n a b l y e x p l a i n s the s o l e f o r m a t i o n o f the b e n z o - v i n y l a d d i t i o n p r o d u c t (47b) o v e r the v i n y l - v i n y l a d d i t i o n p r o d u c t . F l g u r e 6.08 G e o m e t r i c Requirements f o r t h e F o r m a t i o n o f [2+2] C y c l o -a d d i t i o n P r o d u c t s from B e n z o b a r r e l e n e 47. PART VII. PHOTOCHEMICAL [1.3] SHIFTS IN BENZOSEMIBULLVALENES D e p a r t i n g s l i g h t l y from the main f o c u s o f t h i s t h e s i s , an i n t e r e s t i n g phenomenon was n o t i c e d t h r o u g h o u t the p h o t o c h e m i c a l i n v e s t i g a t i o n o f b e n z o b a r r e l e n e s . The s e c o n d a r y p h o t o p r o c e s s whereby the b e n z o s e m i b u l l v a l e n e undergoes a [1,3] s h i f t t o a n o t h e r b e n z o s e m i b u l l v a l e n e f r e q u e n t l y o c c u r r e d . A g e n e r a l d e s c r i p t i o n o f t h e s e s h i f t s was g i v e n i n S e c t i o n V I o f t h e I n t r o d u c t i o n . However, the i n t e r e s t i n g f e a t u r e h e r e i s t h a t t h e s e s h i f t s a r e fo u n d t o be p h o t o c h e m i c a l l y r e v e r s i b l e r e s u l t i n g i n u n u s u a l p h o t o s t a t i o n a r y s t a t e s . Shown i n F i g u r e 7.02 a r e some b e n z o s e m i b u l l v a l e n e s s t u d i e d f o r t h i s s h i f t . C o n s i s t e n t w i t h the l i t e r a t u r e , •'-•^^ t h e s e r e a c t i o n s p r o c e e d e i t h e r t h r o u g h t h e i r s i n g l e t (Sj^) or h i g h e r energy t r i p l e t ( T 2 ) e x c i t e d s t a t e s . These [1,3] s h i f t s come about from c l e a v a g e o f the C2a'^6c bond f o l l o w e d by r e c o m b i n a t i o n between the C^-C^^ p o s i t i o n s o f the i n i t i a l l y c l e a v e d s p e c i e s ( F i g u r e 7.01). F i g u r e 7.01 Mechanism o f [1,3] S h i f t P h o t o c o n v e r s i o n 29a 42a Ma 44£ 45a 45c hv X = X = X = X = hv X . Y = C O 2 C H 3 X , Y = COPh X = C O 2 C H 3 , Y = COPh X = C O P h , Y = C O 2 C H 3 C O 2 C H 2 C H 3 , Y = COPh C O P h , Y = C O 2 C H 2 C H 3 C 0 2 C H ( C H 3 ) 2 , Y = COPh C O P h , Y = C 0 2 C H ( C H 3 ) 2 Ratio 29b -< 42c 6 4 43c 8 2 43b 2 8 441 9 1 44b 2 8 45Î 9 1 45b 1 : 9 7 : 3 (benzene sens.) 8 : 2 (acetone sens.) 29c X , Y = C O 2 C H 3 43£J X = C O 2 C H 3 , Y = COPh 43Ê X = C O P h , Y = C O 2 C H 3 F i g u r e 7.02 P h o t o s t a t i o n a r y S t a t e s o f Some B e n z o s e m i b u l l v a l e n e s S t u d i e d . I t i s i n t e r e s t i n g t o n o t e t h a t t h e [1,3] s h i f t o f benzosemi-b u l l v a l e n e 29e l e a d s t o an i d e n t i c a l compound; t h e i n t e r c o n v e r s i o n i s d e g e n e r a t e . A l s o n o t e w o r t h y i s t h e f i n d i n g t h a t p h o t o l y s i s o f 1 , 2 - d i s u b s t i t u t e d b e n z o s e m i b u l l v a l e n e s gave no s u b s t a n t i a l c o n v e r s i o n . J u d g i n g from the o b s e r v e d r e s u l t s a l o n g w i t h some o t h e r benzosemibullvalenes-'-^O s t u d i e d by o t h e r g r o u p s , t h e [1,3] s h i f t o f b e n z o s e m i b u l l v a l e n e s r e q u i r e s a c a r b o n y l - c o n t a i n i n g s u b s t i t u t e n t a d j a c e n t t o t h e bond c l e a v e d . T h i s i s u n d e r s t a n d a b l e s i n c e a f t e r i n i t i a l bond c l e a v a g e , a r a d i c a l o f the i n t e r m e d i a t e can be r e s o n a n c e s t a b i l i z e d by t h e a d j a c e n t c a r b o n y l . I n s i t u a t i o n s where the c a r b o n y l s u b s t i t u t e n t i s a t the Cg^, p o s i t i o n , i s o m e r i z a t i o n s t i l l r e t a i n s t h i s c a r b o n y l on th e Cgj, p o s i t i o n f o r a r e v e r s e p h o t o c o n v e r s i o n . T h i s , i n t u r n , s u g g e s t s an e x p l a n a t i o n f o r the p h o t o s t a t i o n a r y s t a t e s o b s e r v e d . EXPERIMENTAL GENERAL PROCEDURES Melting Points (MP) M e l t i n g p o i n t s i n degrees C e l s i u s (°C), were d e t e r m i n e d on a F i s h e r - J o h n s h o t s t a g e a p p a r a t u s and are u n c o r r e c t e d . Infrared Spectra (IR) I n f r a r e d s p e c t r a were measured on a P e r k i n - E l m e r 1710 F o u r i e r t r a n s f o r m i n f r a r e d s p e c t r o p h o t o m e t e r . O i l y samples were p r e p a r e d as a l i q u i d f i l m on a sodium c h l o r i d e p l a t e , b a c k g r o u n d c o r r e c t e d f o r sodium c h l o r i d e . S o l i d samples were p r e p a r e d as p e l l e t s w i t h p o t a s s i u m bromide ( K B r ) , b a c k g r o u n d c o r r e c t e d w i t h a f r e s h l y p r e p a r e d b l a n k p o t a s s i u m bromide p e l l e t . P e l l e t s were p r e p a r e d by g r i n d i n g a p p r o x i m a t e l y 2 mg o f sample w i t h 100 mg o f KBr and p r e s s i n g the m i x t u r e i n a P e r k i n - E l m e r 186-0002 e v a c u a t e d d i e w i t h a C a r v e r Model B l a b o r a t o r y p r e s s a t 17,000 pounds p e r s q uare i n c h ( p s i ) . A l l major peaks were r e p o r t e d . A b s o r p t i o n maxima (^max^ r e p o r t e d i n r e c i p r o c a l c e n t i m e t e r s (cm"-'-) f o l l o w e d by s i g n a l i n t e n s i t y and a s s i g n m e n t ( i f made) i n p a r e n t h e s i s . A b b r e v i a t i o n s : v s = v e r y s t r o n g , s = s t r o n g , m = medium, b r = b r o a d . Nuclear Magnetic Resonance Spectra (NMR) P r o t o n n u c l e a r m a g n e t i c re s o n a n c e (-'-H NMR) s p e c t r a were r e c o r d e d on B r u k e r AC-200 (200 MHz), V a r i a n XL-300 (300 MHz), and B r u k e r WH-400 s p e c t r o m e t e r s . The c h e m i c a l s h i f t s were r e c o r d e d i n the S s c a l e i n p a r t s p e r m i l l i o n (ppm) w i t h t e t r a m e t h y l s i l a n e (TMS) as the i n t e r n a l s t a n d a r d a t 0 ppm. D e u t e r i o c h l o r o f o r m ( C D C I 3 ) was u s e d as the s o l v e n t u n l e s s o t h e r w i s e s t a t e d . S i g n a l m u l t i p l i c i t y , number o f p r o t o n s , c o u p l i n g c o n s t a n t ( s ) ( J ) , and a s s i g n m e n t a r e g i v e n i n p a r e n t h e s i s . A b b r e v i a t i o n s : s = s i n g l e t , d = d o u b l e t , t = t r i p l e t , q = q u a r t e t , dd = d o u b l e t o f d o u b l e t s , m = m u l t i p l e t . Carbon n u c l e a r m a g n e t i c re s o n a n c e (•'-^C NMR) s p e c t r a were r e c o r d e d on t h e f o l l o w i n g i n s t r u m e n t s : B r u k e r AC-200 a t 50 MHz, V a r i a n XL-300 a t 75 MHz, and B r u k e r WH-400 a t 100 MHz f o r b r o a d band p r o t o n (BB) d e c o u p l e d and a t t a c h e d p r o t o n t e s t (APT) e x p e r i m e n t s . C h e m i c a l s h i f t s i n ppm were r e p o r t e d from the s i g n a l s o f the BB d e c o u p l e d s p e c t r a . The s o l v e n t was C D C I 3 u n l e s s o t h e r w i s e s t a t e d . Assignment ( i f made) i s i n p a r e n t h e s i s f o l l o w i n g each 5. Mass Spectra (MS) Low and h i g h r e s o l u t i o n mass s p e c t r a were r e c o r d e d w i t h a K r a t o s MS-50 i n s t r u m e n t . Gas chromatography mass s p e c t r a (GC-MS), low r e s o l u t i o n and h i g h r e s o l u t i o n , were c a r r i e d o u t on a K r a t o s MS-80RFA i n s t r u m e n t . I o n i z a t i o n f o r the above was a c h i e v e d by e l e c t r o n bombardment a t 70 e l e c t r o n v o l t s ( E I ) . D e s o r p t i o n c h e m i c a l i o n i z a t i o n (DCI) s p e c t r a were done on a D e l s i Nermag RlO-lOC s p e c t r o m e t e r u s i n g ammonia as t h e CI gas. F a s t atom bombardment (FAB) s p e c t r a were r e c o r d e d on an AEI MS-9 mass s p e c t r o m e t e r w i t h Xenon bombardment on t o an o - n i t r o b e n z o i c a c i d m a t r i x o f t h e sample. Mass t o c h a r g e r a t i o s (m/z) a r e r e p o r t e d w i t h r e l a t i v e i n t e n s i t i e s i n p a r e n t h e s i s . U l t r a v l o l e t spectra (UV) U l t r a v i o l e t s p e c t r a were measured on a P e r k i n - E l m e r Lambda-4B UV/Vis s p e c t r o p h o t o m e t e r i n a c e t o n i t r i l e ( C H 3 C N ) . The A^^^ r e p o r t e d i n nanometers f o l l o w e d by t h e e x t i n c t i o n c o e f f i c i e n t ( e ) . A b b r e v i a t i o n s : sh = s h o u l d e r . Elemental Analyses (EA) A l l e l e m e n t a l a n a l y s e s were p e r f o r m e d by the d e p a r t m e n t a l m i c r o a n a l y s t , Mr. P. Borda. Crystallographic Analyses A l l X - r a y c r y s t a l s t r u c t u r e s were d e t e r m i n e d on a R i g a k u 4 - c i r c l e d i f f r a c t o m e t e r by e i t h e r Dr. J . T r o t t e r , Dr. S.J. R e t t i g , Dr. P.R. P o k k u l u r l , o r Dr. R. Jones o f t h e UBC Department o f C h e m i s t r y . Chromatography Gas c h r o m a t o g r a p h i c (GC) a n a l y s e s were p e r f o r m e d on a H e w l e t t P a c k a r d 5890 i n s t r u m e n t f i t t e d w i t h a fl a m e i o n i z a t i o n d e t e c t o r . S i g n a l i n t e g r a t i o n was done w i t h a H e w l e t t P a c k a r d 3392A a t t a c h m e n t . Three f u s e d s i l i c a c a p i l l a r y columns were used, a 15m X 0.25mm DB-1 column (J&W S c i e n t i f i c I n c . ) , a 15m x 0.25mm DB-17 column (J&W S c i e n t i f i c I n c . ) , and a 20m x 0.21mm carbowax column ( H e w l e t t P a c k a r d ) . P r e p a r a t i v e column c h r o m a t o g r a p h i e s were done by t h e F l a s h method-'-^l u s i n g 230-400 mesh s i l i c a g e l (Merck) . E l u t i n g s o l v e n t s are s p e c i f i e d i n each p r e p a r a t i o n . T h l n l a y e r chromatography (TLC) was p e r f o r m e d p r i o r t o each p r e p a r a t i v e column on p r e - c o a t e d s i l i c a g e l p l a t e s ( t y p e 5554, M e r c k ) . Solvents and Reagents S p e c t r a l grade s o l v e n t s were u s e d f o r p h o t o c h e m i c a l e x p e r i m e n t s w i t h o u t f u r t h e r p u r i f i c a t i o n u n l e s s o t h e r w i s e s t a t e d . O t h e r s o l v e n t s were p u r i f i e d a c c o r d i n g t o known procedures-'-22 p r i o r t o use. Reagents were u s e d d i r e c t l y w i t h o u t f u r t h e r p u r i f i c a t i o n u n l e s s o t h e r w i s e s t a t e d . Photochemical Light Sources P h o t o l y s e s were c a r r i e d o u t w i t h e i t h e r a 450 Watt H a n o v i a medium p r e s s u r e mercury lamp or a PRA UV-12 n i t r o g e n l a s e r (337 nm) The d e s i r e d w a v e l e n g t h s f o r the lamp were a c h i e v e d by u s i n g Corex (A > 260 nm), P y r e x (A > 290 nm), o r u r a n i u m g l a s s (A > 330 nm) f i l t e r s l e e v e s . Solution Photolyses A n a l y t i c a l p h o t o l y s e s were c o n d u c t e d i n 0.2 ml q u a r t z o r P y r e x tubes and some p r e p a r a t i v e p h o t o l y s e s were p e r f o r m e d i n 10 ml P y r e x t u b e s , b o t h s e a l e d w i t h ground g l a s s c a p s . Samples were de g a s s e d by r e p e a t i n g t h e freeze-pump-thaw c y c l e t w i c e and s e a l i n g under n i t r o g e n . L a r g e r s c a l e p r e p a r a t i v e p h o t o l y s e s were c a r r i e d out i n an i m m e r s i o n well-^-^^ w i t h the sample s o l u t i o n d e g a s s e d by b u b b l i n g w i t h n i t r o g e n f o r 1/2 h p r i o r t o and d u r i n g p h o t o l y s i s . S o l i d S t a t e P h o t o l y s e s A n a l y t i c a l s t u d i e s (4-10 mg) were c o n d u c t e d i n NMR tubes e v a c u a t e d and f i l l e d w i t h n i t r o g e n p r i o r t o p h o t o l y s i s . P r e p a r a t i v e p h o t o l y s e s were c o n d u c t e d i n 10 ml P y r e x p h o t o t u b e s e v a c u a t e d and f i l l e d w i t h n i t r o g e n f o r c r y s t a l l i n e p h o t o l y s e s . F o r l a r g e r c o n v e r s i o n s , the c r y s t a l s were c r u s h e d between two P y r e x m i c r o s c o p e s l i d e s as a s a n d w i c h and p h o t o l y z e d w i t h o u t a n i t r o g e n atmosphere ( i n a l l s o l i d s t a t e p h o t o l y s e s p e r f o r m e d i n t h i s t h e s i s , t h e p r e s e n c e o r absence o f a n i t r o g e n atmosphere makes no d i f f e r e n c e t o t h e o b s e r v e d r e a c t i v i t y o r p r o d u c t r a t i o s ) . I . SYNTHESIS OF STARTING MATERIALS D i m e t h y l 1 , 4 - D i h y d r o - l , 4 - e t h e n o n a p t h a l e n e - 2 , 3 - d i c a r b o x y l a t e ( 2 9 ) " " F o l l o w i n g the p r o c e d u r e o f G r o v e n s t e i n e t A l . ^ ^ , a m i x t u r e o f n a p h t h a l e n e (108 g, 0.84 m o l e ) , d i m e t h y l a c e t y l e n e d i c a r b o x y l a t e (56 g, 0.44 m o l e ) , and h y d r o q u i n o n e (3 g, 27 mmoles) was s e a l e d under vacuum i n 8 hea-vy w a l l e d P y r e x tubes such t h a t each tube was l e s s t h a n h a l f f u l l . The t u b e s were h e a t e d a t 170-180 °G f o r 3 days i n an e x p l o s i o n -p r o o f oven. The d a r k brown r e a c t i o n m i x t u r e was d i s s o l v e d i n 500 ml o f c h l o r o f o r m and chromatographed on s i l i c a g e l u s i n g e t h y l a c e t a t e and p e t r o l e u m e t h e r (30-60 °C) (5 : 95 v/v) as t h e e l u t i n g s o l v e n t . The f i r s t band was n a p h t h a l e n e , and t h e s e c o n d band was the d e s i r e d compound 29. R e c r y s t a l l i z a t i o n f r o m methanol gave 14.5 g o f c o l o r l e s s p r i s m s ( y i e l d 1 2 % ) . MP: 105-106 °C ( l i t . ^ ^ 105.0-105.5 °C). IR (KBr) v^^y^: 3070 (m, C-H), 1718 ( v s , C=0) , 1437 ( s ) , 1307 ( s ) , 1245 ( v s , C-0), 1052 ( s ) cm-1. ^H NMR (400 MHz) 5: 7.4-6.9 (m, 6H, a r o m a t i c and v i n y l ) , 5.25 (dd, 2H, J = 4,3 Hz, b r i d g e h e a d ) , 3.78 ( s , 6H, m e t h y l ) ppm. l ^ C NMR (75 MHz) 6: 165.83 (C=0), 147.39, 144.59, 138.96, 124.37, 123.02, 52.15, 50.20 ppm. MS ( E I ) m/e: 270 (M+, 3 0 ) , 238 ( 1 6 ) , 210 ( 9 6 ) , 183 ( 6 7 ) , 152 ( 1 0 0 ) , 128 ( 5 5 ) . UV (CH3CN): 230 sh (e 5460), 275 (e 1300) nm. A n a l . c a l c d . f o r Ci6H]^404: C, 71.10; H, 5.22. Found: C, 71.22; H, 5.30. The s t r u c t u r e o f t h i s compound was c o n f i r m e d by an X - r a y d i f f r a c t i o n a n a l y s i s . The c r y s t a l d a t a were as f o l l o w s : C]^gH]^404, t e t r a g o n a l , space group 14, a = 18.572(4)Â, c = 7.957 (7)Â, V = 2744 ( 2 ) Â 3 , Z = 8, = 1.31 g/ml, R = 0.034. D e t a i l s were p u b l i s h e d i n a p a p e r by J . T r o t t e r . 1 , 4 - D i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c A c i d (40) To a s o l u t i o n o f 29 (21 g, 81 mmole) i n 150 ml o f e t h a n o l was added 650 ml o f 9.6 M NaOH^^q). The r e s u l t i n g s o l u t i o n was r e f l u x e d f o r 2 h, c o o l e d t o room t e m p e r a t u r e , and washed w i t h 200 ml o f d i e t h y l e t h e r t o remove u n r e a c t e d s t a r t i n g m a t e r i a l . The b a s i c aqueous l a y e r was t h e n n e u t r a l i z e d w i t h c o n c e n t r a t e d HCl^^q) t o g i v e a w h i t e p r e c i p i t a t e . T h i s was c o o l e d t o room t e m p e r a t u r e a g a i n and e x t r a c t e d t w i c e w i t h 500 ml o f d i e t h y l e t h e r . The combined e x t r a c t s were washed t w i c e w i t h 200 ml o f w a t e r , d r i e d o v e r MgSO^, and e v a p o r a t e d under r e d u c e d p r e s s u r e t o g i v e 17.0 g o f d i a c i d 40 as a w h i t e s o l i d ( y i e l d 87%) . R e c r y s t a l l i z a t i o n from a c e t o n i t r i l e gave c o l o r l e s s p r i s m s . MP: 204-205 °C. IR (KBr) Un,ax: 3100-2300 ( b r , OH), 1700-1450 ( s , C=0) , 1279 ( s , C-0) c m ' l . ^H NMR (400 MHz, DMSO-dg) 5: 10.00 ( b r s, 2H, OH), 7.4-6.9 (m, 6H, a r o m a t i c and v i n y l ) , 5.26 (dd, 2H, J = 4,3 Hz, b r i d g e h e a d ) ppm. ^H NMR (400 MHz, acetone-dg) 5: 7.4-6.9 (m, 6H, a r o m a t i c and v i n y l ) , 5.79 (dd, 2H, J = 4,3 Hz, b r i d g e h e a d ) ppm. ^H NMR (400 MHz, CDCI3) 5: 7.4-6.9 (m, 6H, a r o m a t i c and v i n y l ) , 5.79 (dd, 2H, J = 4,3 Hz, b r i d g e h e a d ) ppm. l ^ C NMR (75 MHz, DMSO-dg) 5: 167.14 (0=0), 147.27 ( C ) , 145.68 ( C ) , 139.51 (CH), 124.34 (CH), 123.20 (CH), 50.16 (CH) ppm. MS ( E I ) m/e: 242 (M+, 3 0 ) , 224 ( 3 2 ) , 198 ( 1 6 ) , 180 ( 3 7 ) , 152 ( 1 0 0 ) , 128 ( 3 8 ) . E x a c t mass c a l c u l a t e d f o r CI^HIQOI^: 242.0579, f o u n d 242.0576. UV (CH3CN): 228 (e 5700), 290 sh (e 800) nm. A n a l . c a l c d . f o r Cn^ttiQO^: C, 69.42; H, 4.16. Found: C, 69.40; H, 4.26. I , 4 - D i h y d r o - 1 , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y 1 i c A n h y d r i d e (41) To a s o l u t i o n o f 40 (13.0 g, 53.7 mmoles) d i s s o l v e d i n 500 ml o f f r e s h l y d i s t i l l e d methylene c h l o r i d e was added o x a l y l c h l o r i d e (17.4 ml, 0.20 m o l e ) . The s o l u t i o n was r e f l u x e d f o r 15 h i n a n i t r o g e n atmosphere. The s o l v e n t and e x c e s s o x a l y l c h l o r i d e were e v a p o r a t e d and t h e r e m a i n i n g s o l i d was r e c r y s t a l l i z e d f r om a 1:4 m i x t u r e o f benzene : hexanes t o g i v e 10.0 g o f t h e p r o d u c t ( y i e l d 83%) as p a l e y e l l o w n e e d l e s . MP: 129-130 «G. IR (KBr) Umax^ 1^38 ( s , C=0), 1767 ( s , C=0) cm'^. NMR (CDCI3) 5: 7.4-7.0 (m, 6H, a r o m a t i c and v i n y l ) , 5.29 (dd, 2H, J = 4,3 Hz, b r i d g e h e a d ) ppm. (CDCI3) 5: 160.30 ( C ) , 159.92 (C) , 143.67 ( C ) , 139.58 (CH), 125.17 (CH), 124.40 (CH), 45.39 ( b r i d g e h e a d CH) ppm. MS ( E I ) m/e: 224 (M+, 4 0 ) , 180 ( 3 8 ) , 152 ( 1 0 0 ) , 128 ( 4 0 ) , 76 ( 4 5 ) . E x a c t mass c a l c u l a t e d f o r CI^HQO^: 224.0473, f o u n d 224.0472. UV (CH3CN): 246 (e 17500) nm. A n a l . c a l c d . f o r C14H8O3: C,75.00; H, 3.60. Found: C, 75.13; H, 3.60. I , 4 - D i p h e n y l - 2 - b u t e n e - l , 4 - d i o n e (55)''^c F o l l o w i n g t h e method o f R.E. Lutz,'^5c ^ benzene (180 ml) and anhydrous A I C I 3 (35 g, 0.26 mole) s o l u t i o n , under n i t r o g e n , was added 15.3 g (11 ml, 0.10 mole) o f f u m a r y l c h l o r i d e ( f r o m A l d r i c h ) t h r o u g h a d r o p p i n g f u n n e l a t a r a t e o f 1-2 drops p e r second. The r e a c t i o n m i x t u r e was h e a t e d t o 50-60 °C a t a l l t i m e s . A f t e r a d d i t i o n , the s o l u t i o n was r e f l u x e d f o r 10 min and t h e n p o u r e d i n t o an e q u a l volume o f a c i d i f i e d c r u s h e d i c e . The benzene l a y e r was washed 4 t i m e s w i t h warm w a t e r , d r i e d o v e r Na2S04, f i l t e r e d , and e v a p o r a t e d . The r e m a i n i n g p r o d u c t was r e c r y s t a l l i z e d from e t h a n o l t o g i v e 12.4 g o f b r i g h t y e l l o w n e e d l e s ( y i e l d 5 3 % ) . MP: 108-110 °C ( l i t 7 5 c 109-110 «C) . IR (KBr) v^^^: 1650 (m, C=0), 1446 (m), 1323 (m), 1294 ( s ) , 705 ( s ) NMR ( 3 0 0 M H z ) 5: 8.09 (m, 4H, o r t h o - a r o m a t i c ) , 8.01 ( s , 2H, v i n y l ) , 7.66-7.60 (m, 2H, p a r a - a r o m a t i c ) , 7.56-7.49 (m, 4H, m e t a - a r o m a t i c ) ppm. MS ( E I ) m/e: 236 (M+, 2 2 ) , 105 ( 1 0 0 ) , 77 ( 4 2 ) . 2,3 - D i b r o m o - 1 , 4 - d i p h e n y I b u t a n e - 1 , 4 - d l o n e ( 5 6 ) ^ ^ ^ C r y s t a l s o f compound 55 (10.8 g, 45.8 mmoles) were d i s s o l v e d i n 115 ml o f d r y c h l o r o f o r m and t o t h i s was added d r o p w i s e an e q u i m o l a r amount o f bromine (7.32 g, 2.53 ml) under n i t r o g e n . The r e a c t i o n was s t i r r e d a t room t e m p e r a t u r e f o r an a d d i t i o n a l 45 min and e v a p o r a t e d t o a w h i t e s o l i d . R e c r y s t a l l i z a t i o n f rom e t h a n o l : c h l o r o f o r m (1 : 5) gave 14.6 g o f c o l o r l e s s p r i s m s ( y i e l d 8 1 % ) . MP: 176-179 °C form, l i t . ^ ^ b 3^ 79 OQ decomp.). IR (KBr) v^^^: 1681 ( s , C=0), 1596 (m), 1446 (m), 1289 ( s ) cm'^. ^H NMR (300 MHz, Benzene-dg) 5: 7.86-7.78 (m, 4H, o r t h o -a r o m a t i c ) , 7.05-7.01 (m, 2H, p a r a - a r o m a t i c ) , 6.98-6.90 (m, 4H, m e t a - a r o m a t i c ) , 6.15 ( s , 2H, HCBr) ppm. MS ( E I ) m/e: 316 ( 0 . 1 , M+ - B r ) , 236 (19, M+ - B r 2 ) , 208 ( 1 1 ) , 105 (100) , 77 (79) . MS (DCI, NH3) m/e: 414 (8, M + NH4+)_ 397 (7, M+ + 1 ) , 254 ( 1 5 ) , 237 ( 2 7 ) , 105 ( 1 0 0 ) , 77 ( 2 3 ) . l , 4 - D i p h e n y l - 2 - b u t y n e - l , 4 - d i o n e ( 5 7 ) ' ^ ^ D i b r o m i d e 56 (13.5 g, 34.1 mmoles), t r i e t h y l a m i n e (11.1 ml, 80 mmoles), and 108 ml o f d r y benzene were r e f l u x e d under n i t r o g e n f o r 4.5 h. The r e a c t i o n was c o o l e d t o room t e m p e r a t u r e and the c o l o r l e s s c r y s t a l s o f t r i e t h y l a m m o n i u m bromide were f i l t e r e d o f f . The r e s u l t i n g brown s o l u t i o n was e v a p o r a t e d t o a s o l i d and p r o m p t l y r e c r y s t a l l i z e d ( t o a v o i d p o l y m e r i z a t i o n ) from m e t h a n o l t o g i v e 4.4 g o f brown c r y s t a l s ( y i e l d 5 5 % ) . MP: 110-111 °C ( l i t . 7 5 a n o - m IR (KBr) Uj^ax^ 16^6 ( s , C=0) , 1592 (m) , 1449 (m) , 1317 (m) , 1261 ( s ) cm-1. NMR (300 MHz) 5: 8.22-8.16 (m, 4H, o r t h o - a r o m a t i c ) , 7.73-7.66 (m, 2H, p a r a - a r o m a t i c ) , 7.58-7.51 (m, 4H, raeta-aromatic) ppm. MS ( E I ) m/e: 234 ( 7 1 , M+), 206 ( 1 1 ) , 178 ( 5 0 ) , 129 ( 4 9 ) , 105 ( 1 0 0 ) , 77 ( 8 7 ) . 2 , 3 - D i b e n z o y l - 1 , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e (42) I n a t h i c k w a l l e d vacuum s e a l e d P y r e x tube was p l a c e d compound 18 (500 mg, 2.14 mmoles), n a p h t h a l e n e (4.0 g, 31 mmoles), and h y d r o q u i n o n e (150 mg). The tube was h e a t e d t o 180 °C f o r 1.5 h, c o o l e d t o room t e m p e r a t u r e , d i s s o l v e d i n c h l o r o f o r m , and chromatographed u s i n g an e l u t i n g m i x t u r e o f d i e t h y l e t h e r and hexanes (1 : 9 v / v ) . The f i r s t band was u n r e a c t e d n a p h t h a l e n e . Next came the d e s i r e d p r o d u c t as a brown o i l . T h i s o i l was t r e a t e d w i t h a c t i v a t e d c h a r c o a l and c e l i t e i n d i e t h y l e t h e r , f i l t e r e d , and e v a p o r a t e d t o a f f o r d 146 mg o f a c o l o r l e s s o i l ( y i e l d 1 9 % ) . S o l i d i f i c a t i o n f rom s c r a t c h i n g i n hexanes and r e c r y s t a l l i z a t i o n f r om benzene : hexanes ( 1 : 5 v/v) gave c o l o r l e s s p r i s m s . MP: 102-103 °C. IR (KBr) v^^^: 1649 ( s , C=0), 1594 (m), 1273 ( s ) cm'^. NMR (300 MHz) 5: 7.45-7.00 (m, 16H, a r o m a t i c and v i n y l ) , 5.42 (dd, 2H, J = 4,3 Hz, b r i d g e h e a d ) ppm. NMR (50 MHz) 5: 194.52 (C=0), 153.94 ( C ) , 145.02 ( C ) , 139.46 (CH), 137.87 ( C ) , 132.77 (CH), 128.50 (CH), 128.21 (CH) , 124.68 (CH), 123.41 (CH), 51.94 (CH, b r i d g e h e a d ) ppm. MS ( E I ) m/e: 362 (M+, 4 9 ) , 257 ( 3 6 ) , 128 ( 5 5 ) , 105 100), 77 ( 6 0 ) . E x a c t mass c a l c u l a t e d f o r C26H]^802: 362.1307, f o u n d 362.1305. UV (CH3CN): 255 (e 21500) nm. A n a l , c a l c d . f o r C26H]^802 : C, 86.17; H, 5.01. Found: C, 85.97; H, 5.00. I , 4 - D i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c A c i d Monomethyl E s t e r (58) A s o l u t i o n o f a n h y d r i d e 41 (9.1 g, 40.6 mmoles) i n 300 ml o f d r y methanol was r e f l u x e d under n i t r o g e n f o r 2 h. The methanol was e v a p o r a t e d and the r e s u l t i n g y e l l o w o i l was d i s s o l v e d i n 100 ml o f me t h y l e n e c h l o r i d e and washed t w i c e w i t h 75 ml o f w a t e r . The o r g a n i c l a y e r was d r i e d o v e r MgSO^, f i l t e r e d , and e v a p o r a t e d under r e d u c e d p r e s s u r e t o a f f o r d 10.8 g o f a v i s c o u s o i l ( y i e l d 1 0 0 % ) . IR ( l i q u i d f i l m ) v^^^: 3400-2500 ( b r , OH), 1719 ( s , C=0), 1637 ( s ) , 1278 (C-0) cm-1. NMR (300 MHz) 5: 7.3-6.9 (m, 6H, a r o m a t i c and v i n y l ) , 5.89 (dd, IH, J = 5,2 Hz, b r i d g e h e a d ) , 5.60 (dd, IH, J = 5,2 Hz, b r i d g e h e a d ) , 4.00 ( s , 3H, m e t h y l ) ppm. l ^ C NMR (75 MHz) 5: 166.50 (C=0), 166.05 (C=0), 148.25 ( C ) , 146.19 ( C ) , 145.38 ( C ) , 145.26 ( C ) , 139.47 (CH), 139.25 (CH), 124.29 (CH), 124.25 (CH), 123.15 (CH), 123.11 (CH), 52.20 (CH3), 49.94 (CH), 49.79 (CH) ppm. MS ( E I ) m/e: 256 (M+, 2 5 ) , 212 ( 3 1 ) , 196 ( 2 0 ) , 179 ( 1 8 ) , 152 ( 1 0 0 ) , 128 ( 3 0 ) . E x a c t mass c a l c u l a t e d f o r Ci^Hu'^h- 256.0736, f o u n d 256.0728. M e t h y l 2 - B e n z o y l - l , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 3 - c a r b o x y l a t e (43) To a s o l u t i o n o f a c i d - e s t e r 58 (5.5 g, 22 mmoles) i n 180 ml o f anhydrous methylene c h l o r i d e was added d r o p w i s e o x a l y l c h l o r i d e (5.6 m l , 64 mmoles) and the r e a c t i o n was r e f l u x e d f o r 1 h. The s o l v e n t was e v a p o r a t e d under r e d u c e d p r e s s u r e and t h e c r u d e a c y l c h l o r i d e , a y e l l o w o i l , was r e d i s s o l v e d i n 2.4 l i t e r s o f d r y benzene. Then a p p r o x i m a t e l y 4.4 g (33 mmoles) o f anhydrous A I C I 3 ( f r o m A l d r i c h ) was added i n s e v e r a l p o r t i o n s d i r e c t l y t o the s o l u t i o n . The r e a c t i o n m i x t u r e was s t i r r e d a t room t e m p e r a t u r e f o r 1 h 45 min under a n i t r o g e n atmosphere. The deep r e d s o l u t i o n was t h e n quenched w i t h 300 ml o f w a t e r and t h e t o t a l volume r e d u c e d t o 1 l i t e r . The s o l u t i o n was t h e n washed w i t h w a t e r (2 x 200 m l ) , d r i e d o v e r MgSO^, f i l t e r e d , and e v a p o r a t e d . The r e s u l t i n g o i l was chromatographed and e l u t e d w i t h 10% d i e t h y l e t h e r i n hexanes. The f i r s t major band was 1.4 g o f the p r o d u c t as a w h i t e s o l i d ( y i e l d 2 1 % ) . R e c r y s t a l l i z a t i o n from hexanes gave p r i s m s . MP: 127-128 °C. IR (KBr) v^^^: 1713 ( s , e s t e r C=0), 1667 ( s , b e n z o y l C=0), 1244 ( s , C-0) c m ' l . NMR (400 MHz) 5: 7.6-6.9 (m, I I H , a r o m a t i c and v i n y l ) , 5.55 (dd, IH, J = 6,2 Hz, b r i d g e h e a d ) , 5.04 (dd, IH, J = 6,2 Hz, b r i d g e h e a d ) , 3.40 ( s , 3H, m e t h y l ) ppm. l ^ c NMR (75 MHz) S : 195.60 ( b e n z o y l 0=0), 164.14 ( C ) , 159.27 ( C ) , 145.41 ( C ) , 144.12 ( C ) , 141.97 ( C ) , 140.27 (CH), 138.03 (CH), 135.69 ( C ) , 133.39 (CH), 128.57 (CH), 128.52 (CH), 124.55 (CH), 124.34 (CH), 123.25 (CH), 123.07 (CH), 52.29 (CH), 51.61 (CH3), 48.89 (CH) ppm. MS ( E I ) m/e: 316 (M-H, 1 1 ) , 284 ( 1 1 ) , 256 ( 1 2 ) , 211 ( 1 2 ) , 152 ( 2 0 ) , 128 ( 9 0 ) , 105 ( 1 0 0 ) , 77 ( 3 9 ) . E x a c t mass c a l c u l a t e d f o r C2iH]^603: 316.1100, f o u n d 316.1103. UV (Hexane): 247 {e 16890), 290 sh (e 3220) nm. A n a l . c a l c d . f o r C21HX6O3: C, 79.73; H, 5.10. Found: C, 79.75; H, 5.13. The s t r u c t u r e o f t h i s compound was s u p p o r t e d by an X - r a y d i f f r a c t i o n a n a l y s i s . The c r y s t a l d a t a a r e as f o l l o w s : C2iH]^g03, t r i c l i n i c , space group P I , a = 9.772 (8)Â, b = 11.034 (2)Â, c = 8.174 ( 8 ) Â , a = 92.58(1)°, = 111.50(8)°, 7 = 97.96(1)°, V = 8 0 7 . 8 ( 2 ) Â 3 , Z = 2, Dx = 1.296 g/ml, R = 0.042. E t h y l 2 - B e n z o y l - l , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 3 - c a r b o x y l a t e (44) C r y s t a l s o f 43 (400 mg, 1.27 mmole) were d i s s o l v e d i n 400 ml o f d r y e t h a n o l and t o t h i s was added 4 ml o f c o n c e n t r a t e d H2SO4. The s o l u t i o n was r e f l u x e d f o r 2 days and n e u t r a l i z e d w i t h s a t u r a t e d NaHC03^gq^. The e t h a n o l was e v a p o r a t e d under r e d u c e d p r e s s u r e and t h e r e m a i n i n g s o l u t i o n e x t r a c t e d w i t h d i e t h y l e t h e r , washed w i t h w a t e r , d r i e d o v e r MgS04, f i l t e r e d , and e v a p o r a t e d a g a i n . The r e m a i n i n g o i l was chromatographed on s i l i c a g e l u s i n g d i e t h y l e t h e r and hexanes (1 : 9 v/v) as t h e e l u t i n g s o l v e n t . The p r o d u c t e l u t e d i n the f i r s t band as a w h i t e s o l i d (340 mg, 8 1 % ) . T h i s was f o l l o w e d c l o s e l y by s t a r t i n g m a t e r i a l 4 3 . R e c r y s t a l l i z a t i o n from hexanes gave c o l o r l e s s r o d s . MP: 93-94 °C. IR (KBr) U m a x : 1708 ( s , e s t e r C=0), 1657 ( s , b e n z o y l C=0), 1255 ( s , C-0) cm-1. 1-H NMR (400 MHz) 5: 7.6-6.9 (m, I I H , a r o m a t i c and v i n y l ) , 5.55 (dd, IH, J = 6,2 Hz, b r i d g e h e a d ) , 5.02 (dd, IH, J = 6,2 Hz, b r i d g e h e a d ) , 3.85 ( q , 2H, J = 7 Hz, C H 2 ) , 0.79 ( t , 3H, J = 7 Hz, C H 3 ) ppm. l^ C NMR (50 MHz) 6: 195.82 ( b e n z o y l C=0), 163.91 ( C ) , 158.74 ( C ) , 145.66 ( C ) , 144.36 ( C ) , 142.11 ( C ) , 140.52 (CH), 138.17 (CH), 136.03 ( C ) , 133.51 (CH), 128.85 (CH), 128.63 (CH), 124.68 (CH), 123.36 (CH), 123.24 (CH), 61.04 (CH2), 52.56 ( b r i d g e h e a d CH), 49.00 ( b r i d g e h e a d CH), 13.31 (CH3) ppm. MS ( E I ) m/e: 330 (M+, 1 5 ) , 284 ( 1 6 ) , 256 ( 1 5 ) , 152 ( 1 0 ) , 128 ( 1 7 ) , 105 ( 1 0 0 ) , 77 ( 2 0 ) . E x a c t mass c a l c u l a t e d f o r C22H18O3: 330.1255, f o u n d 330.1251. UV (CH3CN) : 251 (e 16500) nm. A n a l , c a l c d . f o r C22H18O3: C, 79.98; H, 5.49. Found: C, 80.10; H, 5.47. The s t r u c t u r e o f t h i s compound was s u p p o r t e d by an X - r a y d i f f r a c t i o n a n a l y s i s . The c r y s t a l d a t a a r e as f o l l o w s : €22^18^3' t r i c l i n i c , space group P I , a = 10.14(1)Â, b = 11.28(2)Â, c = 8.41(1)Â, a = 96.31(1)°, ^ = 110.26(9)°, 7 = 95.62(1)°, V = 8 8 6 . 8 ( 2 ) Â 3 , Z = 2, Dx = 1.237 g/ml, R = 0.043. I s o p r o p y l 2 - B e n z o y l - 1 , 4 - d i h y d r o - 1 , 4 - e t h e n o n a p h t h a l e n e - 3 - c a r b o x y l a t e (45) Compound 43 (400 mg, 1.27 mmole) d i s s o l v e d i n 200 ml o f d r y i s o p r o p a n o l was r e a c t e d w i t h c o n c e n t r a t e d H2SO4 (1.2 ml) and s t i r r e d a t r e f l u x f o r 3 days. G.C. showed an e q u i l i b r i u m r a t i o (43 : 45) o f 67 : 29. The r e a c t i o n was n e u t r a l i z e d w i t h s a t . NaHC03(^q) and the i s o p r o p a n o l e v a p o r a t e d . E x t r a c t i n g w i t h d i e t h y l e t h e r , w a s h i n g w i t h w a t e r , d r y i n g o v e r MgS04, f i l t e r i n g , and e v a p o r a t i n g under r e d u c e d p r e s s u r e gave a y e l l o w o i l . Chromatography o f t h i s o i l on s i l i c a g e l u s i n g a 1:9 ( v / v ) m i x t u r e o f d i e t h y l e t h e r : hexanes as the e l u e n t gave 108 mg o f 45 i n t h e f i r s t band ( y i e l d 2 5 % ) . T h i s was f o l l o w e d c l o s e l y by s t a r t i n g m a t e r i a l 43 (180 mg, 45% r e c o v e r e d ) . R e c r y s t a l l i z a t i o n o f 45 from hexanes gave n e e d l e s . MP: 77-78 °C. IR (KBr) Umax^ 1^95 ( s , e s t e r C=0), 1666 ( s , b e n z o y l C=0), 1270 ( s , C-0). 711 ( s ) c m ' l . NMR (300 MHz) S : 7.6-6.95 (m, I I H , a r o m a t i c and v i n y l ) , 5.57 (dd, IH, J = 6,2 Hz, b r i d g e h e a d ) , 5.01 (dd, IH, J = 6,2 Hz, b r i d g e h e a d ) , 4.76 ( s e p t e t , IH, J = 6 Hz, CH(CH3)2), ^-^^ ^H, J = 6 Hz, m e t h y l ) , 0.73 ( d , 3H, J = 6 Hz, m e t h y l ) ppm. •^^ C NMR (75 MHz) 8: 196.07 ( b e n z o y l C=0) , 163.50 (C) , 158.45 (C) , 145.87 ( C ) , 144.53 ( C ) , 142.21 ( C ) , 140.78 (CH), 138.24 (CH), 136.23 ( C ) , 133.68 (CH), 129.10 (CH), 128.77 (CH), 124.80 (CH), 124.58 (CH). 123.46 (CH), 123.38 (CH), 69.13 ( i s o p r o p y l CH), 52.69 (CH), 49.02 (CH), 21.19 ( m e t h y l ) , 21.14 ( m e t h y l ) ppm. The above a s s i g n m e n t s were s u p p o r t e d by an APT. MS ( E I ) m/e: 344 (M+, 7), 284 (13), 256 (12), 128 (15), 105 (100), 77 (21). E x a c t mass c a l c u l a t e d forC23H2o03: 344.1412, f o u n d 344.1418. U V (CH3CN) : 251 (e 14500) nm. A n a l , c a l c d . f o r C23H20O3: C, 80.21; H, 5.85. Found: C, 80.36; H, 5.90. The s t r u c t u r e was s u p p o r t e d by an X - r a y d i f f r a c t i o n a n a l y s i s . The c r y s t a l d a t a a r e as f o l l o w s : C23H2o03> m o n o c l i n i c , space group P2i/c, a = 7.402(3)Â, b = 20.013(5)Â, c = 12.556(3)Â, ^ = 93.32(2)°, V = 1856.8(9)À3, Z = 4, = 1.232 g/ml, R = 0.036. I, 4-Dihydro-1,4-ethenonaphthalene-2,3-dicarboxy1ic Ac i d , Diethylamine Monosalt (48) C r y s t a l s o f d i a c i d 40 (300 mg, 1.2 mmoles), d i e t h y l a m i n e (0.3 ml, 2.9 mmoles), and 15 ml o f e t h y l a c e t a t e were p l a c e d i n a 50 ml roun d bottom f l a s k . The s o l u t i o n was r e f l u x e d f o r 20 min and the s a l t , as a w h i t e p r e c i p i t a t e was d i s s o l v e d a t r e f l u x w i t h a f u r t h e r a d d i t i o n o f a p p r o x i m a t e l y 30 ml o f e t h y l a c e t a t e . The c l e a r s o l u t i o n was s l o w l y c o o l e d t o room t e m p e r a t u r e a l l o w i n g f o r c r y s t a l s t o form. The r e s u l t i n g c o l o r l e s s r o d s were s u c t i o n f i l t e r e d (260 mg, y i e l d 69%) . MP: 163-164 °C. IR (KBr) U[„ax- ^058 ( b r s) , 2772 ( b r s) , 2507 ( b r m) , 1700 (m), 1621 ( s ) , 1524 ( s ) , 1466 ( s ) , 1371 ( s ) cm"!. NMR (300 MHz) 5: 9.25 ( b r s, 2H, a c i d OH), 7.4-6.8 (m, 6H, a r o m a t i c and v i n y l ) , 5.78 (dd, 2H, J = 4,3 Hz, b r i d g e h e a d ) , 3.10 ( q , 4H, J = 7 Hz, CHg), 1.30 ( t , 6H, J = 7 Hz, C H 3 ) ppm. MS ( E l ) m/e: (no M+ peak) 242 ( 4 ) , 224 ( 3 2 ) , 198 ( 4 0 ) , 180 (25) 152 ( 1 0 0 ) , 128 ( 4 0 ) . MS (FAB) m/e: 316 (M + 1 ) . UV (CH3CN): 223 sh (e 9970), 290 (e 1650) nm. A n a l . c a l c d . f o r C]^8H2i04N: C, 68.55; H, 6.71; N, 4.44. Found: C, 68.55; H, 6.81; N, 4.40. 1 , 4 - D i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c A c i d , P y r r o l i d i n e M o n o s a l t (49) D i a c i d 40 (300 mg, 1.2 mmoles) and p y r r o l i d i n e (0.15 m l , 1.8 mmoles) were r e f l u x e d i n 15 ml o f e t h y l a c e t a t e f o r 10 min t o form a w h i t e p r e c i p i t a t e . A p p r o x i m a t e l y 75 ml o f e t h y l a c e t a t e was added a t r e f l u x t o d i s s o l v e the p r o d u c t . T h i s was a l l o w e d t o c o o l s l o w l y t o form 230 mg o f r o d s a f t e r f i l t r a t i o n ( y i e l d 6 1 % ) . MP: 185-187 °C. IR (KBr) u^iax- ^011 ( b r s) , 2790 ( b r m) , 1578 ( v s ) , 1463 ( v s ) , 1360 ( v s ) , 751 ( s ) cm-1. ^H NMR (300 MHz) 5: 9.58 ( b r s, 2H, a c i d OH), 7.34-6.88 (m, 6H, a r o m a t i c and v i n y l ) , 5.72 (dd, 2H, J = 4,3 Hz, b r i d g e h e a d ) , 3.34 (m. 4H, 2 X NCH2), 2.05 (m, 4H, CH2-CH2-CH2-CH2) ppm. MS (FAB) m/e: 314 (M + 1, 2 2 ) , 72 ( 1 0 0 ) . UV (CH3CN): 223 sh (e 8050), 290 (e 1280) nm. A n a l , c a l c d . f o r Ci3Hi^904N: C, 69.00; H, 6.11; N, 4.47. Found: C, 68.87; H, 6.07; N, 4.40. 1,4-D i h y d r o - 1 , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c Ac i d , P y r r o l i d i n e D i s a i t (50) D i a c i d 40 (70 mg, 0.29 mmole) and p y r r o l i d i n e (41 mg, 0.58 mmole) i n 4 ml o f a c e t o n i t r i l e were r e f l u x e d f o r 45 min and c o o l e d t o g i v e s m a l l w h i t e n e e d l e s . The c r y s t a l s were b r i e f l y s u c t i o n f i l t e r e d t o g i v e 80 mg o f the s a l t ( y i e l d 7 0 % ) . P r o l o n g e d s u c t i o n f i l t r a t i o n r e s u l t s i n re m o v a l o f one e q u i v a l e n t o f p y r r o l i d i n e and subsequent m e l t i n g o f t h e c r y s t a l s f o l l o w e d by t h e i r r e s o l i d i f i c a t i o n as the mo n o - s a l t . MP: ~ 90 °C ( d e c o m p o s i t i o n ) . IR (KBr) v^^^: 2979 ( b r s ) , 2773 ( b r m), 1558 ( v s ) , 1464 ( v s ) , 1386 ( s ) , 716 (m) cm"!. NMR (400 MHz, CDCI3) 6: 7.30-7.20 (m, 2H, a r o m a t i c ) , 6.95-6.85 (4H, m, a r o m a t i c and v i n y l ) , 5.50 ( b r s, 2H, b r i d g e h e a d ) , 3.00 (m, 8H, 4 X NCH2), 1.75 (m, 8H, 2 x CH2CH2) ppm. MS ( E l ) m/e: (no M+) 242 ( 5 ) , 224 ( 4 8 ) , 198 ( 3 8 ) , 180 ( 3 9 ) , 152 ( 1 0 0 ) , 128 ( 5 5 ) , 70 ( 9 1 ) . MS (FAB) m/e: 385 (M + 1 ) . UV (CH3CN): 223 sh (£ 6500), 290 (e 2000) nm. 1 , 4 - D i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d l c a r b o x y l i c A c i d E t h y l e n e d i a m i n e D i s a i t (51) D i a c i d 40 (300 mg, 1.2 mmole) and e t h y l e n e d i a m i n e (0.15 ml, 2.2 mmoles) were r e f l u x e d i n 20 ml o f e t h y l a c e t a t e f o r 1 h. The r e s u l t i n g p r e c i p i t a t e was s u c t i o n f i l t e r e d t o g i v e 352 mg o f a d r y w h i t e powder ( y i e l d 9 7 % ) . R e c r y s t a l l i z a t i o n from w a t e r gave c o l o r l e s s n e e d l e s . These c r y s t a l s were i n s o l u b l e i n c h l o r o f o r m , a c e t o n e , benzene, and a c e t o n i t r i l e . MP: 235-238 °C. IR (KBr) Un,ax: 3100 ( b r s) , 1636 ( s ) , 1559 ( s ) , 1500 ( s ) , 1455 (m), 1386 ( s ) , 711 (m) c m " l . NMR (400 MHz, DMSO-dg) 5: 7.3-6.8 (m, 6H, a r o m a t i c and v i n y l ) , 5.70 (dd, 2H, J = 4,3 Hz, b r i d g e h e a d ) , 5.0-4.5 ( v e r y b r s, 4H, 2 X NH2), 2.78 ( s , 4H, CH2-CH2) ppm. MS ( E I ) m/e: (no M+ peak) 242 ( 5 ) , 224 ( 3 1 ) . 198 ( 3 7 ) , 152 ( 1 0 0 ) , 128 ( 4 8 ) . MS (FAB) m/e: 303 (M + 1 ) . UV (CH3CN): 223 sh (e 4160), 290 ( 6 500) nm. A n a l , c a l c d . f o r C]^6Hi^804N: C, 63.57; H, 6.00; N, 9.27. Found: C, 63.54; H, 6.00; N, 9.29. 1 , 4 - D i h y d r o - 1 , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c A c i d , R u b i d i u m D i s a i t (52) A c i d 40 (200 mg, 0.8 mmole) was d i s s o l v e d i n 12 ml o f a c e t o n i t r i l e and t o t h i s was added 0.1 ml o f 50% (w/w) r u b i d i u m h y d r o x i d e i n w a t e r (1.6 mmole, A l d r i c h ) . The s o l u t i o n was d i l u t e d t o 17 ml, s t i r r e d a t r e f l u x f o r 30 min, c o o l e d , and f i l t e r e d t o g i v e 271 mg o f a w h i t e s o l i d ( y i e l d 8 2 % ) . R e c r y s t a l l i z a t i o n by s l o w e v a p o r a t i o n o f methanol i n an NMR tube gave c o l o r l e s s n e e d l e s . MP: > 300 °C. IR (KBr) v^^y.: 3400-3000 ( b r s) , 1569 ( v s ) , 1542 ( v s ) , 1371 ( v s ) cm'-'-. NMR (300 MHz, CD3OD) 6: 7.26-6.80 (m, 6H, a r o m a t i c and v i n y l ) , 5.10 (dd, 2H, J = 4,3 Hz, b r i d g e h e a d ) ppm. ^H NMR (300 MHz, D2O) 6: 7.45-7.00 (m, 6H, a r o m a t i c and v i n y l ) , 5.15 (dd, 2H, J = 4,3 Hz, b r i d g e h e a d ) ppm. MS (FAB) m/e: 413 (M + 1 , 7 ) , 411 ( 9 ) , 238 ( 5 3 ) , 85 ( 1 0 0 ) . UV (CH3OH): 229 (e 11000), 288 sh (e 1400) nm. 1 , 4 - D i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c A c i d , B a rium D i s a i t (53) D i a c i d 40 (200 mg, 0.8 mmole) d i s s o l v e d i n 10 ml o f a c e t o n i t r i l e and Ba(OH)2.8H20 (252 mg, 0.8 mmole) i n 4 ml o f w a t e r were r e f l u x e d t o g e t h e r f o r 3 h. The r e s u l t i n g p r e c i p i t a t e was f i l t e r e d t o g i v e 199 mg o f a w h i t e powder ( y i e l d 6 6 % ) . MP: > 300 °C. IR (KBr) Ujjjax: 1645 (m) , 1559 ( v s ) , 1455 ( s ) , 1413 ( s ) cm'^. % NMR ( 3 0 0 M H z , D2O) 5: 7.5-7.0 (m, 6H, a r o m a t i c and v i n y l ) , 5.16 (dd, 2H, J = 4,3 Hz, b r i d g e h e a d ) ppm. MS (FAB) m/e: 379 (M+-f1, 2 9 ) , 356 ( 2 0 ) , 186 ( 2 2 ) . UV (H2O): 228 sh (e 2200), 265 (e 1900) nm. 1 , 4 - D i h y d r o - 1 , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d l c a r b o x y l i c Ac i d , m-Amino-acetophenone M o n o s a l t (54) C r y s t a l s o f d i a c i d 40 (70 mg, 0.29 mmole) d i s s o l v e d i n 3 ml o f a c e t o n i t r i l e and 3'-aminoacetophenone (50 mg, 0.37 mmole, A l d r i c h ) i n 2 ml a c e t o n i t r i l e were mixed t o g e t h e r and s t i r r e d a t room t e m p e r a t u r e f o r 20 min and t h e n a t r e f l u x f o r a n o t h e r 20 min. The c l e a r y e l l o w s o l u t i o n was c o n c e n t r a t e d t o a y e l l o w o i l , s c r a t c h e d t o a s o l i d i n 1 ml o f d i e t h y l e t h e r , and f i l t e r e d t o g i v e 76 mg o f an o f f - w h i t e s o l i d ( y i e l d 7 0 % ) . A l l a t t e m p t s t o r e c r y s t a l l i z e the s o l i d have f a i l e d as t h e s a l t i n s o l u t i o n d i s s o c i a t e s and t h e amine s l o w l y p o l y m e r i z e s t o a d a r k brown o i l . MP: 111-113 °C. IR (KBr) Unjax^ 2958 ( b r s) , 2631 ( b r s) , 1694 ( s ) , 1579 ( v s ) , 1445 ( v s ) , 1359 ( v s ) cm'^. NMR (300 MHz, CDCI3) 5: 9.36 ( b r s, OH), 7.8-6.7 (m, lOH, a r o m a t i c and v i n y l ) , 5.65 (dd, 2H, J = 4,3 Hz, b r i d g e h e a d ) , 2.55 ( s , 3H, CH3) ppm. MS (FAB) m/e: 378 (M + 1 , 4 ) , 352 ( 6 ) , 225 ( 1 3 ) , 55 ( 5 4 ) . UV (CH3CN): 230 (€ 37050), 252 sh (e 11400), 333 (e 3100) nm. A n a l . c a l c d . f o r C22H19O5N: C, 70.02; H, 5.07; N, 3.71. Found: C, 70.13; H, 5.08; N, 3.75. 4 - ( 2 , 5 - D i m e t h y l p h e n y l ) - p e n t a n o i c A c i d ( 6 0 ) ^ ^ Anhydrous p - x y l e n e (106 g, 1.00 mole, from A l d r i c h ) and 7 - v a l e r o l a c t o n e (47 ml, 0.50 mole, from A l d r i c h ) were s t i r r e d under a n i t r o g e n atmosphere and t o t h i s was added anhydrous A I C I 3 (70 g, 0.55 mole) as a s o l i d o v e r a p e r i o d o f 0.5 h. The s o l u t i o n was h e a t e d t o r e f l u x f o r 15 min and much HCl^g^ e v o l v e d . The s o l u t i o n was t h e n p o u r e d o v e r a c i d i f i e d i c e , d i l u t e d w i t h d i e t h y l e t h e r , washed w i t h d i l u t e HCl^^q) ( t o remove A l ( 0 H ) 3 ) , d r i e d o v e r MgSO^, f i l t e r e d , and e v a p o r a t e d t o g i v e 117 g o f a l i g h t y e l l o w s o l i d ( y i e l d 9 0 % ) . R e c r y s t a l l i z a t i o n gave a w h i t e amorphous s o l i d . MP: 88-92 °C ( l i t . 7 6 113.5 o c ) _ IR (KBr) Ujnax'- 3200-2600 ( b r s, OH), 1723 ( s , G=0) , 1460 (m) , 1428 (m), 1286 (m), 1214 (m) cm'^. ^H NMR (300 MHz) S : 7.1-6.8 (m, 3H, a r o m a t i c ) , 3.00 (m, IH, CH2-CH-CH3), 2.30 ( s , 3H, a r o m a t i c m e t h y l ) , 2.27 (m, 2H, CH2), 2.25 ( s , 3H, a r o m a t i c m e t h y l ) , 1.93 (m, 2H, CH2), 1.22 ( d , 3H, J = 8 Hz, CH-CH3) ppm. MS ( E I ) m/e: 206 (M+, 5 5 ) , 146 ( 4 8 ) , 133 ( 1 0 0 ) , 117 ( 1 9 ) , 105 ( 4 8 ) , 91 ( 4 4 ) , 77 ( 2 8 ) . 2 , 3 - D i h y d r o - 4 , 5 , 8 - 1 r i m e t h y 1 - 1 - n a p h t h a l e n o n e ( 6 1 ) ^ 6 I n a 500 ml 2-neck f l a s k was p l a c e d 100 g o f 85% H3PO4 and t o t h i s was added, w i t h s t i r r i n g , 75 g o f anhydrous P2*-'5 o v e r 1 min. The t e m p e r a t u r e r o s e t o -200 °C and t h e s o l i d d i s s o l v e d . The m i x t u r e was c o o l e d t o 170 °C and 58 g o f a c i d 60 (0.282 mole) was added i n s e v e r a l p o r t i o n s . A f t e r a l l the a c i d had d i s s o l v e d , t h e r e a c t i o n was s t i r r e d a t 140 °C f o r 5 min more. The s o l u t i o n was t h e n p o u r e d o v e r i c e , e x t r a c t e d w i t h d i e t h y l e t h e r , washed w i t h w a t e r , n e u t r a l i z e d w i t h s a t . NaHC03, washed w i t h w a t e r a g a i n , d r i e d o v e r MgSO^, and f i l t e r e d . The s o l v e n t was removed t o g i v e 39.6 g o f an o i l ( y i e l d 7 4 % ) . IR ( n e a t ) v^^^.: 2929 ( s , CH) , 1677 ( s , C=0) , 1474 (m) , 1263 (m) c m ' l . % NMR (300 MHz) 5: 7.17 ( d , IH, J = 8 Hz, a r o m a t i c ) , 6.97 ( d , IH, J = 8 Hz, a r o m a t i c ) 3.28 (m, IH, CH2-CH-CH3), 2.57 ( s , 3H, a r o m a t i c m e t h y l ) , 2.32 ( s , 3H, a r o m a t i c m e t h y l ) , 2.20 (m, 2H, CH2), 1.95 (m, 2H, CH2), 1.25 ( d , 3H, J = 7 Hz, a l i p h a t i c m e t h y l ) ppm. MS ( E I ) m/e: 188 (M+, 100), 173 ( 9 0 ) , 160 ( 6 2 ) , 145 ( 6 1 ) , 132 ( 5 0 ) , 117 ( 6 6 ) , 91 ( 3 9 ) . 1 , 2 . 3 , 4 - T e t r a h y d r o - l , 4 , 5 , 8 - t e t r a m e t h y l - l - n a p h t h o l (62) To k e t o n e 61 (36 g, 0.19 mole) i n 100 ml anhydrous d i e t h y l e t h e r under n i t r o g e n was added d r o p w i s e w i t h s t i r r i n g a t 0 °C was 285 ml o f 1.4 M m e t h y l l i t h i u m i n hexane (0.4 mole, from A l d r i c h ) . The r e a c t i o n was warmed t o room t e m p e r a t u r e and s t i r r e d f o r 45 min, p o u r e d i n t o i c e , e x t r a c t e d w i t h d i e t h y l e t h e r , washed w i t h w a t e r , and d r i e d w i t h MgSO^. Removal o f s o l v e n t gave 34 g o f a c i s / t r a n s m i x t u r e o f compound 62 as a w h i t e s o l i d ( y i e l d 8 8 % ) . A s m a l l p o r t i o n was r e c r y s t a l l i z e d t o g i v e c o l o r l e s s c r y s t a l s . MP: 87-89 °C ( l i t . ^ ^ 93-95 °C). IR (KBr) Ujua^: 3345 ( v s , OH), 2941 ( v s , CH) , 1466 ( s ) , 1124 ( s ) , 812 ( s ) cra-1. ^H NMR (300 MHz, c i s / t r a n s m i x t u r e ) 5: 7.00-6.89 (m, 2H, a r o m a t i c ) , 3.12 (m, IH, CH2-CH-CH3), 2.61 ( s , 3H, a r o m a t i c m e t h y l ) , 2.30 ( s , 3H, a r o m a t i c m e t h y l ) , 2.25-1.96 (m, 2H, CH2), 1.95-1.65 (m, 2H, CH2), 1.57 ( s , 3H, HO-C-CH3), 1.22 ( d , 3H, J = 5 Hz, CH-CH3) ppm. MS ( E I ) m/e: 204 (M+, 1 1 ) , 189 ( 1 0 0 ) , 171 ( 5 4 ) , 156 ( 2 7 ) . A n a l , c a l c d . f o r C14H20O: C, 82.30; H, 9.87. Found: C, 82.62; H, 9.82. I , 2-D i h y d r o - 1 , 4 , 5 , 8 -1 e trame t h y I n a p h t h a l e n e ( 6 3 ) ^ 6 The crude a l c o h o l from above (31 g, 0.15 mole) was d i s s o l v e d i n 200 ml o f t e t r a h y d r o f u r a n and t o t h i s was added 20 ml o f cone H C l ^ ^ q ) . A f t e r s t i r r i n g f o r 1 h, t h e r e a c t i o n was n e u t r a l i z e d w i t h s a t u r a t e d NaHC03, e x t r a c t e d w i t h e t h e r and chromatographed on s i l i c a g e l u s i n g p e t r o l e u m e t h e r (30-60 °C) as the e l u t i n g s o l v e n t . T h i s gave 17 g o f a c o l o r l e s s o i l ( y i e l d 61%) i n t he f i r s t band. IR ( n e a t ) v^^^^: 2963 ( s , CH) , 1456 ( s ) , 813 (m) cm-^. ^H NMR (300 MHz) 5: 5.89 ( s , 2H, a r o m a t i c ) , 5.77 (m, IH, v i n y l ) , 3.01 (m, IH, CH2-CH-CH3), 2.41 ( s , 3H, a r o m a t i c m e t h y l ) , 2.28 ( s , 3H, a r o m a t i c m e t h y l ) , 2.19 (m, 3H, v i n y l m e t h y l ) , 2.10-2.00 (m, 2H, CH2), 1.06 ( d , 3H, J = 7 Hz, CH-CH3) ppm. MS ( E I ) m/e: 185 (M+, 4 3 ) , 171 ( 1 0 0 ) , 155 ( 6 0 ) , 141 ( 2 6 ) . 1 , 4 , 5 , 8 - T e t r a m e t h y l n a p h t h a l e n e ( 6 4 ) ^ 6 The a l k e n e 63 (10 g, 54 mmoles) was p l a c e d i n a 2-neck f l a s k f i t t e d w i t h a co n d e n s e r and a n i t r o g e n i n l e t . To t h i s was added 2 g o f 10% p a l l a d i u m on a c t i v a t e d c h a r c o a l ( A l d r i c h ) and the m i x t u r e h e a t e d t o to 280 °C i n a sand b a t h f o r 5 h. D u r i n g the r e a c t i o n , a s l o w s t r e a m o f n i t r o g e n was f l u s h e d t h r o u g h the i n l e t t o remove the H2(p-) e v o l v e d . A f t e r the r e a c t i o n , the sample was d i s s o l v e d i n methylene c h l o r i d e , f i l t e r e d , c o n c e n t r a t e d i n vacuo, and t w i c e r e c r y s t a l l i z e d f r o m methanol t o g i v e 1.7 g o f c o l o r l e s s n e e d l e s ( y i e l d 1 7 % ) . MP: 128-130 °C ( l i t . ' ' ^ 131 °C) . IR (KBr) U n , a x : 2937 (m, CH) , 1593 (m) , 1463 (m) , 816 ( s ) cm'^. ^H NMR ( 3 0 0 M H z ) 5: 7.09 ( s , 4H, a r o m a t i c ) , 2.82 ( s , 12H, 4 X m e t h y l ) ppm. MS ( E I ) m/e: 184 (M-(-, 100), 169 ( 8 6 ) , 153 ( 2 7 ) . D i m e t h y l 1 , 4 - D i h y d r o - l , 4 , 5 , 8 - t e t r a m e t h y l - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 -d i c a r b o x y l a t e (47) T e t r a m e t h y l n a p h t h a l e n e 64 (1.7 g, 9.2 mmoles), d i m e t h y l a c e t y l e n e d i c a r b o x y l a t e (0.9 ml, 7.3 mmoles), and h y d r o q u i n o n e (0.15 g) were s e a l e d under vacuum i n a t h i c k - w a l l e d P y r e x tube and h e a t e d a t 180 °C f o r 2 h i n an e x p l o s i o n - p r o o f oven. The m i x t u r e was chromatographed on s i l i c a g e l u s i n g d i e t h y l e t h e r and hexanes (1 : 9 v/v) as the e l u t i n g s o l v e n t . The f i r s t band was 0.9 g o f t e t r a m e t h y l n a p h t h a l e n e , and the second band was t h e p r o d u c t (47) as a w h i t e s o l i d . R e c r y s t a l l i z a t i o n from methanol gave 518 mg o f c o l o r l e s s n e e d l e s ( y i e l d 2 0 % ) . MP: 126-127 °C. IR (KBr) Vj^^y.: 1728 ( s , C=0) , 1645 (m) , 1606 (m) , 1253 ( s , C-0) cm-1. ^H NMR (300 MHz) S : 6.59 ( s , 2H, a r o m a t i c ) , 6.54 ( s , 2H, v i n y l ) , 3.73 ( s , 6H, 2 x e s t e r CH3), 2.54 ( s , 6H, 2 x a r o m a t i c CH3), 2.21 ( s , 6H, 2 X b r i d g e h e a d CH3) ppm. l ^ c NMR (50 MHz) 5: 165.31 (C=0), 151.50 ( C ) , 146.64 ( C ) , 146.53 (CH), 130.57 (C) , 129.32 (CH), 53.41 (C b r i d g e h e a d ) , 51.91 ( e s t e r CH3), 22.51 (CH3), 21.09 (CH3) ppm. MS ( E I ) m/e: 326 (M+, 2 0 ) , 294 ( 4 3 ) , 266 ( 9 8 ) , 207 ( 1 0 0 ) . E x a c t mass c a l c u l a t e d f o r C20H22O4: 326.1518, f o u n d 326.1525. UV (CH3CN): 236 (€ 2700), 281 (e 975) nm. A n a l . c a l c d . f o r C20H22O4: C, 73.60; H, 5.79. Found: C, 73.48; H, 5.73. The s t r u c t u r e o f t h i s compound was s u p p o r t e d by an X - r a y d i f f r a c t i o n a n a l y s i s . C r y s t a l d a t a i s as f o l l o w s : C20H22O4, m o n o c l i n i c , space group P 2 i / c , a = 12.643(9)Â, b = 9.288(1)Â, c = 15.153(9)Â, fi = 105.595(5)°, V = 1712.8(5)Â3, Z = 4, D,, = 1.265 g/ml, R = 0.037. l - D e u t e r i o n a p h t h a l e n e ^ ^ Over a h a l f hour p e r i o d , 1-bromonaphthalene (40 g, 0.194 mole) i n 100 ml o f anhydrous d i e t h y l e t h e r was added t o magnesium t u r n i n g s (8.0 g, 0.20 mole) i n 80 ml o f anhydrous d i e t h y l e t h e r . The r e s u l t i n g m i x t u r e was r e f l u x e d f o r 1 h and c o o l e d t o 0 °C. D2O (10 ml, 0.05 mole) was added d r o p w i s e . A f t e r the a d d i t i o n , t h e r e a c t i o n was s t i r r e d f o r 0.5 h f u r t h e r a t room t e m p e r a t u r e and quenched w i t h a c i d i f i e d i c e . The s o l u t i o n was d i l u t e d w i t h 200 ml o f d i e t h y l e t h e r , washed t h r e e t i m e s w i t h w a t e r , d r i e d o v e r MgS04, f i l t e r e d , and the s o l v e n t e v a p o r a t e d t o g i v e 24 g o f a l i g h t y e l l o w s o l i d . R e c r y s t a l l i z a t i o n f i r s t from methanol t h e n from hexanes gave c o l o r l e s s p l a t e s . MP: 79-80 °C ( l i t . ^ ^ 80 °C). IR (KBr) U n i a x ^ 3055 (m, CH) , 1590 (m) , 1500 (m) , 1376 (m) , 807 (m), 777 ( v s ) cm-1. ^H NMR ( 3 0 0 M H z ) 5: 7.9-7.7 (m, 3.OIH + 0.99D, H 1 + H 4 + H 5 + H 8 ) , 7.5-7.3 (m, 4H, H2+H3+H6-I-H7) ppm. MS ( E I ) m/e: 129 (M+, 100), 103 ( 7 ) . M i x t u r e o f D i m e t h y l 1 and 5 - D e u t e r i o - l , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e -2 , 3 - d i c a r b o x y l a t e (29-D) The p r o c e d u r e was the same as f o r the n o n - d e u t e r a t e d p r e p a r a t i o n d e s c r i b e d e a r l i e r ^ e x c e p t t h a t 6.0 g o f 1 - d e u t e r i o n a p h t h a l e n e (47 mmoles), 3.0 ml o f d i m e t h y l a c e t y l e n e d i c a r b o x y l a t e (24 mmoles, from A l d r i c h ) , and 0.5 g o f h y d r o q u i n o n e were p l a c e d i n one P y r e x t h i c k w a l l e d s e a l e d tube. A f t e r r e c r y s t a l l i z a t i o n , 1.8 g o f c o l o r l e s s p r i s m s ( y i e l d 14%) were o b t a i n e d . MP: 105-106 °C. IR (KBr) v^^y.: 1732 ( s ) , 1714 ( s ) , 1643 (m) , 1238 ( s ) cm'^. ^H NMR (300 MHz) 5: 7.35-7.20 (m, 1.59H + 0.41D, Hj-t-Hg) , 7.02-6.90 (m, 4.00H, Hg-HHy + v i n y l ) , 5.30-5.20 (dd, 1.47H + 0.53D, J = 4,3 Hz, b r i d g e h e a d ) , 3.78 ( s , 6.61H, 2 x m e t h y l ) ppm. MS ( E I ) m/e: 271 (M+, 5 1 ) , 243 ( 1 3 ) , 211 ( 7 7 ) , 184 ( 6 3 ) , 153 ( 1 0 0 ) , 129 ( 5 6 ) . E x a c t mass c a l c u l a t e d f o r Ci6H2^304D: 271.0955. f o u n d 271.0964. M i x t u r e o f 1 and 5 - D e u t e r i o - l , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 -d i c a r b o x y l i c A c i d (40-D) The p r o c e d u r e was the same as f o r the n o n - d e u t e r a t e d p r e p a r a t i o n d e s c r i b e d e a r l i e r e x c e p t 6.9 g o f 29-D was d i s s o l v e d i n 90 ml o f e t h a n o l and 75 g o f NaOH i n 250 ml w a t e r was used. A f t e r workup, 5.7 g o f a w h i t e s o l i d was o b t a i n e d ( y i e l d 9 2 % ) . R e c r y s t a l l i z a t i o n f rom a c e t o n i t r i l e gave p r i s m s . MP: 208-209 °C. IR (KBr) 3200-2200 ( b r m, OH), 1694 ( s ) , 1618 ( s ) , 1567 ( v s ) , 1467 ( s ) , 1280 ( s ) , 1240 ( s ) cm'^. ^H NMR (400 MHz) 5: 11.65 ( b r s, 1.18H, OH), 7.35-7.25 (m, 1.49H + 0.51D, H5 + Hg), 7.05-6.90 (m, 4.00H, Hg + H7 + v i n y l ) , 5.25 (dd, 1.55H + 0.45D, J = 4,3 Hz, b r i d g e h e a d ) ppm. MS ( E I ) m/e: 243 (M+, 1 9 ) , 199 ( 5 7 ) , 154 ( 1 0 0 ) , 129 ( 3 3 ) . E x a c t mass c a l c u l a t e d f o r C14H9O4D: 243.0641, f o u n d 243.0641. M i x t u r e o f 1 and 5 - D e u t e r i o - l , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e -2 , 3 - d i c a r b o x y l i c A n h y d r i d e (41-D) The same p r o c e d u r e u s e d f o r the n o n - d e u t e r a t e d p r e p a r a t i o n was u s e d h e r e e x c e p t t h a t 4.8 g o f 40-D (20 mmoles) i n 135 ml o f d r y m e t h y l e n e c h l o r i d e was r e a c t e d w i t h 4.0 ml o f o x a l y l c h l o r i d e (0.48 mole) R e c r y s t a l l i z a t i o n from a 1:4 m i x t u r e o f benzene and hexanes gave 3.4 g o f l i g h t y e l l o w n e e d l e s ( y i e l d 7 6 % ) . MP: 128-129 °C. IR (KBr) v^ax- ^^^^ - ^771 ( s , C=0) , 870 (m) cm'^. ^H NMR (400 MHz) 6: 7.40-7.30 (m, 1.44H+0.56D, H5 + Hg), 7.15-7.00 (m, 4.00H, H5 + H7 + v i n y l ) , 5.29 (dd, 1.32H + 0.68D, J = 4,3 Hz, b r i d g e h e a d ) ppm. MS ( E I ) m/e: 225 (M+, 5 6 ) , 181 ( 4 1 ) , 153 ( 1 0 0 ) , 129 ( 4 1 ) . E x a c t mass c a l c u l a t e d f o r Cj^4H703D: 225.0536, f o u n d 225.0534. M i x t u r e o f 1,4,5, and 8 - D e u t e r i o - l , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 -d i c a r b o x y l i c A c i d Monomethyl E s t e r (58-D) The p r o c e d u r e was t h e same as f o r t h e p r e p a r a t i o n o f compound 58 e x c e p t t h a t 1.00 g o f a n h y d r i d e 41-D was d i s s o l v e d i n 30 ml o f d r y m e t h a n o l . The y i e l d was 1.16 g ( 1 0 0 % ) . IR ( l i q u i d f i l m ) U j ^ ^ x ^ 3400-2400 ( b r s, OH), 1718 ( v s ) , 1636 ( s ) , 1440 ( s ) , 1278 ( v s ) , 712 (m) cm'^. ^H NMR ( 4 0 0 M H z ) 5: 7.39-7.29 (m, 1.64H + 0.36D, H5 + Eg), 7.02-6.92 (m, 4.00H, Hg + H7 + v i n y l ) , 5.90 ( d , 0.82H + 0.18D, J = 5 Hz, b r i d g e h e a d ) , 5.60 ( d , 0.75H + 0.25D, J = 5 Hz, b r i d g e h e a d ) , 3.99 ( s , 3.24H, m e t h y l ) ppm. MS ( E I ) m/e: 257 (M+, 6 ) , 225 ( 1 0 ) , 213 ( 1 8 ) , 181 ( 1 9 ) , 153 ( 1 0 0 ) , 129 ( 3 4 ) . E x a c t mass c a l c u l a t e d f o r C3^5Hxi04D: 257.0798, f o u n d 257.0796. M i x t u r e o f M e t h y l 1,4,5, and 8 - D e u t e r i o - 2 - b e n z o y l - l , 4 - d i h y d r o - l , 4 -e t h e n o n a p h t h a l e n e - 3 - c a r b o x y l a t e (43-D) The p r o c e d u r e was the same as f o r the n o n - d e u t e r a t e d p r e p a r a t i o n , e x c e p t t h a t 1.16 g o f 58-D (4.51 mmoles) i n 50 ml o f d r y methylene c h l o r i d e , 3 ml o f o x a l y l c h l o r i d e (34.4 mmoles), 600 ml o f d r y benzene, and a p p r o x i m a t e l y one m o l a r e q u i v a l e n t o f A I C I 3 was u s e d ; t h e r e s u l t i n g w h i t e s o l i d weighed 566 mg ( y i e l d 4 0 % ) . MP: 127-128 °C. IR (KBr) Umax^ ^712 ( s , e s t e r C=0), 1667 ( s , b e n z o y l C=0), 1242 ( s , C-0), 702 ( s ) cm"^. NMR (400 MHz) 5: 7.60-6.95 (m, 10.80H + 0.20D, a r o m a t i c and v i n y l ) , 5.54 ( d , 0.67H+0.33D, J = 6 Hz, b r i d g e h e a d ) , 5.03 ( d , 0.67H + 0.33D, J = 6 Hz, b r i d g e h e a d ) , 3.40 ( s , 3.00H, m e t h y l ) ppm. MS ( E l ) m/e: 317 (M+, 4 ) , 285 ( 6 ) , 129 ( 1 1 ) , 105 ( 1 0 0 ) , 77 ( 2 3 ) . E x a c t mass c a l c u l a t e d f o r C21H15O3D: 317.1162, f o u n d 317.1153. I I . PHOTOCHEMISTRY OF SUBSTRATES A. D i m e t h y l 1 , 4 - D i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l a t e (29) D i r e c t S o l u t i o n P h o t o l y s i s ^ ^ • A n a l y t i c a l p h o t o l y s e s (A > 290 nm) were p e r f o r m e d i n benzene, m e t h a n o l , and a c e t o n i t r i l e . The r e a c t i o n s were m o n i t o r e d by GC (DB-1) w h i c h showed the f o r m a t i o n o f one p r o d u c t i n d e p e n d e n t o f s o l v e n t . I n a p r e p a r a t i v e r u n , a s o l u t i o n o f 500 mg o f 29 (1.9 mmole) i n 100 ml o f benzene was p h o t o l y z e d ( A > 290 nm) i n an i m m e r s i o n w e l l s e t u p t o complete c o n v e r s i o n , m o n i t o r e d by GC. The r e a c t i o n m i x t u r e was d i r e c t l y r e c r y s t a l l i z e d t h r e e t i m e s from a 2:1 m i x t u r e o f hexanes and methanol t o g i v e w h i t e n e e d l e s o f d i m e t h y l b e n z o c y c l o o c t e n e - 7 , 8 -d i c a r b o x y l a t e (29d)^'^. MP: 77-78 °C ( l i t . ^ ^ 77.0-77.5 °C). IR (KBr) Uniaj^: 1724 ( s , C=0) , 1435 (m) , 1260 ( s , C-0), 1149 (m) , 1025 (m), 800 (m) cm'^. ^H NMR ( 3 0 0 M H z ) 6: 7.30-7.00 (m, 4H, a r o m a t i c ) , 6.77 ( d , 2H, J = 12 Hz, b e n z y l i c v i n y l ) , 6.20 ( d , 2H, J = 12 Hz, ^ - v i n y l ) , 3.75 ( s , 6H, 2 X m e t h y l ) ppm. MS ( E I ) m/e: 270 (M+, 1 1 ) , 238 ( 1 4 ) , 210 ( 7 7 ) , 179 ( 3 2 ) , 152 ( 1 0 0 ) . UV (CH3CN) \^^^: 284 sh (e 1820) nm. A n a l . c a l c d . f o r C16H14O4: C, 71.10; H, 5.22. Found: C, 71.19; H, 5.24. Benzophenone-Sens i t ized Photolys i s On an a n a l y t i c a l s c a l e , p h o t o l y s i s o f an a p p r o x i m a t e l y 1:1 mass r a t i o o f compound 29 t o benzophenone i n benzene t h r o u g h a u r a n i u m g l a s s f i l t e r (A > 330 nm) gave o n l y one p r o d u c t by GC (DB-1). A s o l u t i o n o f 50 mg o f compound 29 (0.18 mmole) and 0.40 g o f benzophenone (2.2 mmole) i n a 10 ml p h o t o t u b e o f a c e t o n e was p h o t o l y z e d w i t h a medium p r e s s u r e mercury lamp (A > 330 nm). The r e a c t i o n was m o n i t o r e d by GC u n t i l no s t a r t i n g m a t e r i a l r e m a i n e d and chromatographed t o g i v e 39 mg o f t h e p r o d u c t as a t h i c k c o l o r l e s s o i l ( y i e l d 7 8 % ) , i d e n t i f i e d as d i m e t h y l 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e -2 a , 6 c - d i c a r b o x y l a t e (29a). IR ( n e a t ) v^^^: 1730 ( s , C=0) cm'^. % NMR (300 MHz) 6: 7.5-7.1 (m, 4H, a r o m a t i c ) , 5.82 (dd, IH, J = 5,3 Hz, Hi), 5.36 ( d , IH, J = 5 Hz, H2), 4.49 ( d , IH, J = 3 Hz, H6b), 4.48 ( s , IH, H2b), 3.85 ( s , 3H, m e t h y l ) , 3.70 ( s , 3H, m e t h y l ) ppm. MS ( E I ) m/e: 270 (M+, 3 7 ) , 238 ( 1 4 ) , 210 ( 9 4 ) , 183 ( 9 0 ) , 152 ( 1 0 0 ) . E x a c t mass c a l c u l a t e d f o r Ci^Hii^O^: 270.0892, f o u n d 270.0892. UV (CH3CN) \^^^: 278 (e 1100) nm. A c e t o n e - S e n s i t i z e d P h o t o l y s i s of Compound 29 The p h o t o l y s i s was a n a l y t i c a l l y p e r f o r m e d i n a c e t o n e u s i n g a P y r e x f i l t e r s l e e v e (A > 290 nm). The r e a c t i o n was m o n i t o r e d by GC t o show 2 major p h o t o p r o d u c t s w i t h r e t e n t i o n t i m e s c o r r e s p o n d i n g t o compounds 29a and 29e. A t low c o n v e r s i o n t h e i r r a t i o was a p p r o x i m a t e l y 1:1, b u t as c o n v e r s i o n i n c r e a s e d , 29e decomposes q u i c k l y , 29a decomposes s l o w l y , and a new peak a r o s e i n t h e GC w i t h a r e t e n t i o n time c o r r e s p o n d i n g t o compound 29b. Compounds 29e and 29b w i l l be c h a r a c t e r i z e d l a t e r . On a p r e p a r a t i v e s c a l e , compound 29 (1.50 g, 5.6 mmoles) i n 425 ml o f a c e t o n e was p h o t o l y z e d (A > 290 nm) i n an i m m e r s i o n w e l l t o complete c o n v e r s i o n . GC showed p h o t o p r o d u c t s 29a, 29e, and 29b i n a r a t i o 65:25:9 r e s p e c t i v e l y . Chromatography e l u t i n g w i t h p e t . e t h e r (30-60 °C) and d i e t h y l e t h e r 93:7 ( v / v ) gave two bands. The f i r s t was an i n s e p a r a b l e m i x t u r e o f 29e and 29b, f o l l o w e d by 0.96 g o f 29a ( y i e l d 5 4 % ) . The i d e n t i t y o f t h e s e compounds was c o n f i r m e d by NMR s p e c t r o s c o p i c c o m p a r i s o n o f the m i x t u r e s t o t h e i r f u l l c h a r a c t e r i z a t i o n s , d e s c r i b e d l a t e r . S o l i d State Photolysis C r y s t a l s o f compound 29 were p h o t o l y z e d a n a l y t i c a l l y t h r o u g h P y r e x g l a s s f o r 2, 5, and 9 h t o a f f o r d one p r o d u c t , c y c l o o c t a t e t r a e n e (COT) 29c a t 30%, 15%, and 25% c o n v e r s i o n r e s p e c t i v e l y . I n a l l c a s e s , the c r y s t a l s t u r n e d y e l l o w and were s t i c k y on t h e s u r f a c e . Compound 29 and COT 29c were i n s e p a r a b l e by TLC. L a s e r p h o t o l y s i s (A = 337 nm) o f the c r y s t a l s i n an NMR tube f o r 1 h a l s o r e s u l t e d i n y e l l o w i n g and s l i g h t s u r f a c e m e l t i n g . GC showed a 15% c o n v e r s i o n t o p r o d u c t 29c. Photochemical Interconversion of Compounds 29a and 29b Compound 29a was p h o t o l y z e d a n a l y t i c a l l y i n a c e t o n e (A > 290 nm), a c e t o n i t r i l e (A > 260 nm), and benzene (A > 260 nm). A l l t h r e e p h o t o l y s e s gave one major p r o d u c t a t a maximum c o n v e r s i o n o f 52% by GC. The r e a c t i o n i n a c e t o n i t r i l e was f o u n d t o p r o c e e d much more s l o w l y t h a n t h e o t h e r two r e a c t i o n s . I n a p r e p a r a t i v e r u n , compound 29a (0.64 g, 2.4 mmoles) i n 200 ml o f benzene was i r r a d i a t e d t h r o u g h a Corex f i l t e r (A > 260 nm) i n an i m m e r s i o n w e l l f o r 13 h. The sample was s u b s e q u e n t l y c hromatographed u s i n g an e t h y l a c e t a t e and p e t r o l e u m e t h e r (30-60 °C) (1 : 19 v/v) s o l u t i o n as the e l u t i n g s o l v e n t . The f i r s t band c o n t a i n e d 59 mg o f d i m e t h y l 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] -p e n t a l e n e - 1 , 6 c ( 2 a H ) - d i c a r b o x y l a t e (29b) as a c o l o r l e s s o i l ( y i e l d 9%). IR (KBr) u^ax^ 1^19 ( s , C=0) cm'^. NMR (300 MHz) S : 7.4-7.1 (m, 4H, a r o m a t i c ) , 6.15 ( d , IH, J = 3 Hz, v i n y l ) , 4.69 ( s , IH, Hg^), 3.89 ( d , IH, J = 8 Hz, H2b), 3.72 ( s , 3H, m e t h y l ) , 3.71 ( s , 3H, m e t h y l ) , 3.43 (dd, IH, J = 8,3 Hz, H2a) PPm. MS ( E I ) m/e: 270 (M+, 5 5 ) , 210 ( 6 2 ) , 183 ( 4 7 ) , 152 ( 1 0 0 ) , 84 ( 4 2 ) . E x a c t mass c a l c u l a t e d f o r Ci(^Eii^Oi^: 270.0892, f o u n d 270.0885. The p h o t o s t a t i o n a r y s t a t e r a t i o o f the r e a c t i o n was i n v e s t i g a t e d by a s e r i e s o f a n a l y t i c a l s c a l e p h o t o l y s e s . R a t i o s were d e t e r m i n e d by GC, c a l i b r a t e d by c o - i n j e c t i o n s w i t h o c t a d e c a n e (n-C]^gH38) i n t e r n a l s t a n d a r d . I t was c a l c u l a t e d t h a t the GC d e t e c t o r i s 1.6 t i m e s more s e n s i t i v e t o 29b t h e n 29a. Compound 29a, compound 29b, and m i x t u r e s o f t h e two were p h o t o l y z e d : a) i n a c e t o n i t r i l e (A > 260 nm) b u t compound d e c o m p o s i t i o n was too f a s t t o e s t a b l i s h an e q u i l i b r i u m , b) i n benzene (A > 260 nm) t h i r t e e n t i m e s t o e s t a b l i s h a 29a t o 29b r a t i o o f 7 ± 1 : 3 + 1.^^ c) i n a c e t o n e (A > 260 nm) t h r e e t i m e s t o e s t a b l i s h a 29a t o 29b r a t i o o f 8 : 2. A c e t o n e - S e n s i t i z e d P h o t o l y s i s o f Compound 29c On an a n a l y t i c a l s c a l e , s o l u t i o n s o f 29c i n a c e t o n i t r i l e . benzene, and ac e t o n e were p h o t o l y z e d (A > 290 nm) f o r 10 h; compound 29e was the o n l y peak seen on GC ( s u b s e q u e n t l y c h a r a c t e r i z e d ) a t c o n v e r s i o n s o f 15%, 22%, and 100% r e s p e c t i v e l y . On a p r e p a r a t i v e s c a l e , c y c l o o c t a t e t r a e n e 29c (100 mg, 0.37 mmole) i n 200 ml o f a c e t o n e was i r r a d i a t e d t h r o u g h P y r e x (A > 290) i n an i m m e r s i o n w e l l system. The r e a c t i o n was m o n i t o r e d by GC t o co m p l e t e c o n v e r s i o n and t h e n chromatographed on s i l i c a u s i n g d i e t h y l e t h e r and low b o i l i n g p e t r o l e \ i m e t h e r (1:3 v/v) as the e l u e n t . T h i s a f f o r d e d 71 mg o f d i m e t h y l 2 b , 6 b - d i h y d r o b e n z o [ a ] -c y c l o p r o p a [ c d ] p e n t a l e n e - 2 , 6 c ( 2 a H ) - d i c a r b o x y l a t e (29e) as a c o l o r l e s s o i l ( y i e l d 7 1 % ) . IR (KBr) v^^y.: 1718 ( s , C=0) cm'^. NMR (300 MHz) 8: 7.4-7.1 (m, 4H, a r o m a t i c ) , 6.58 ( d , IH, J = 3 Hz, v i n y l ) , 4.51 ( d , IH, J = 3 Hz, Hgb)> 3.84 ( d , IH, J = 6 Hz, H2a)> 3.74 ( d , IH, J = 6 Hz, H2b)> 3.70 ( s , 3H, m e t h y l ) , 3.65 ( s , 3H, m e t h y l ) ppm. MS ( E I ) m/e: 270 (M+, 3 4 ) , 238 ( 1 9 ) , 210 ( 9 2 ) , 183 ( 5 8 ) , 152 ( 7 8 ) , 43 ( 1 0 0 ) . E x a c t mass c a l c u l a t e d f o r C16H14O4: 270.0892, f o u n d 270.0889. D e t e c t i o n o f C y c l o b u t e n e 29d Compound 29c (6 mg, 0.022 mmole) d i s s o l v e d i n an NMR tube was p h o t o l y z e d : a) i n acetone-dg (A > 290 nm) t o 10% c o n v e r s i o n by GC and a n a l y z e d by NMR (300 MHz). S i g n a l s c o r r e s p o n d i n g t o 29c, 29d, and 29e were d e t e c t e d i n a r a t i o o f 74 : 14 : 12. T h i s t h i r d compound 29d was t h e r m a l l y u n s t a b l e and r e a d i l y r e v e r t e d back t o c y c l o o c t a t e t r a e n e 29c on GC; b) i n d e u t e r i o c h l o r o f o r m (A > 330 nm) f o r 3 days t o show no c o n v e r s i o n on GC, b u t NMR (300 MHz) shows a 83 : 17 m i x t u r e o f 29c t o the c y c l o b u t e n e d e r i v a t i v e 29d. From t h e NMR o f t h e m i x t u r e , d i m e t h y l c y c l o b u t a [ a ] n a p h t h a l e n e - 2 , 2 a ( 8 b H ) - d i c a r b o x y l a t e (29d) was c h a r a c t e r i z e d ; c) i n benzene-dg (A > 330 nm) t o a 29c : 29d : 29e r a t i o o f 75 : 15 : 9 c h a r a c t e r i z e d by •'-H NMR o f the m i x t u r e as w e l l . S p e c t r o s c o p i c d a t a f o r 29d a r e d e s c r i b e d below. ^H NMR (400 MHz, CDCI3) 5: 7.3-7.0 (m, 4H, a r o m a t i c o v e r l a p p i n g w i t h 2 9 c ) , 7.72 ( s , IH, Hj^) , 6.47 ( d , IH, J = 10 Hz, H4) , 6.22 ( d , IH, J = 10 Hz, H3), 4.23 ( s , IH, Hgb), 3.78 ( s , 3H, m e t h y l ) , 3.76 ( s , 3H, m e t h y l ) ppm. •'"H NMR (300 MHz, benzene-dg, o n l y n o n - o v e r l a p p i n g peaks a r e r e p o r t e d ) 5: 6.40 ( d , IH, J = 10 Hz, H4), 6.26 ( d , IH, J = 10 Hz, H3), 4.04 ( s , IH, Hgb) ppm. B. 1 , 4 - D i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c A c i d (40) D i r e c t S o l u t i o n P h o t o l y s i s A n a l y t i c a l p h o t o l y s e s t h r o u g h P y r e x (A > 290 nm) were c o n d u c t e d i n NMR t u b e s . Samples were d i s s o l v e d i n CDCI3 (3 mg) and DMSO-dg (6 mg), p h o t o l y z e d f o r 1.5 h, and a n a l y z e d by NMR. T h i s showed t h e f o r m a t i o n o f 40c ( s u b s e q u e n t l y c h a r a c t e r i z e d ) as t h e o n l y p r o d u c t a t 50% and 5% c o n v e r s i o n r e s p e c t i v e l y . On a p r e p a r a t i v e s c a l e , d i a c i d 40 (60 mg, 0.25 mmole) was p h o t o l y z e d (A > 290 nm) i n e t h y l a c e t a t e , u s i n g 3 x 10 ml p h o t o t u b e s , u n t i l t h e s o l u t i o n was b r i g h t y e l l o w (1.75 h) . The r e a c t i o n m i x t u r e was c o n c e n t r a t e d t o a volume o f 5 ml a t 60 °C and a l l o w e d t o c r y s t a l l i z e . C l e a r brown r o d s were f i l t e r e d (18 mg) and i d e n t i f i e d as b e n z o c y c l o o c t e n e - 7 , 8 - d i c a r b o x y l i c a n h y d r i d e (41d)60 ( y i e l d 3 2 % ) . MP: 210-212 °C. IR (KBr) v^^^: 1767 ( s , C=0) , 1263 ( s , C-0), 713 ( s ) cm''^. NMR (400 MHz, CDCI3) 5: 7.35-7.25 (m, 2H, a r o m a t i c ) , 6.99 ( d , 2H, J = 12 Hz, b e n z y l i c v i n y l ) , 6.97-6.91 (m, 2H, a r o m a t i c ) , 6.19 ( d , 2H, J = 12 Hz, / 9 - v i n y l ) ppm. ^H NMR (300 MHz, DMSO-dg) 5: 7.36-7.28 (m, 2H, a r o m a t i c ) , 7.13 ( d , 2H, J = 12 Hz, b e n z y l i c v i n y l ) , 7.05-6.80 (m, 2H, a r o m a t i c ) , 6.19 ( d , 2H, J = 12 Hz, / 3 - v i n y l ) ppm. MS ( E I ) m/e: 224 (M+, 6 9 ) , 180 ( 4 2 ) , 152 ( 1 0 0 ) , 76 ( 4 1 ) . E x a c t mass c a l c u l a t e d f o r Ci4H803: 224.0474, f o u n d 224.0474. A n a l . c a l c d . f o r Ci4H803: C, 75.00; H, 3.60. Found: C, 74.95; H, 3.56. The mother l i q u o r was l e f t t o s t a n d and c l e a r y e l l o w n e e d l e s formed. T h i s was f i l t e r e d t o g i v e 20 mg o f b e n z o c y c l o o c t e n e - 7 , 8 -d i c a r b o x y l i c a c i d (40c) c r y s t a l s ( y i e l d 3 3 % ) . MP: C r a c k s and t u r n s orange a t 122-130 °C ( d e h y d r a t i o n ) , m e l t s a t 208-210 °C ( a n h y d r i d e m e l t i n g p o i n t ) . IR (KBr) Ujnax: 3100-2400 ( b r s, OH), 1724 ( s , C=0) , 1624 (m) , 1230 ( s ) cm-1. ^H NMR (400 MHz, DMSO-dg) 5: 12.95 ( b r s, 2H, 2 x OH), 7.4-7.0 (m, 4H, a r o m a t i c ) , 6.72 ( d , 2H, J = 11 Hz, b e n z y l i c v i n y l ) , 6.18 ( d , 2H, J = 11 Hz, / 3 - v i n y l ) ppm. MS ( E I ) m/e: 224 (M+ - H2O, 72), 180 ( 3 0 ) , 152 ( 1 0 0 ) , 84 ( 8 2 ) , 66 ( 9 9 ) . MS (DCI-NH3) m/e: 243 (M+ + 1, 1 1 ) , 224 ( 1 0 0 ) , 180 ( 4 7 ) , 152 ( 9 0 ) , 85 ( 9 4 ) . B e n z o p h e n o n e - S e n s i t i z e d P h o t o l y s i s Samples o f d i a c i d 40 ( c a . 5 mg) and benzophenone ( c a . 30 mg) were d i s s o l v e d i n a p h o t o t u b e w i t h 1 ml o f acetone-dg and p h o t o l y z e d (A > 330 nm). Two p r o d u c t s were d e t e c t e d by NMR, a t 70% c o n v e r s i o n and shown t o be compounds 40b and 40a ( r a t i o 87 : 1 3 ) . The p h o t o l y s i s was r e p e a t e d a t l o w e r c o n v e r s i o n ( 1 9 % ) , and a 92 : 8 r a t i o o f 40b t o 40c was d e t e r m i n e d by i n t e g r a t i o n o f t h e expanded NMR s i g n a l s . Compounds 40b and 40a were c h a r a c t e r i z e d l a t e r . On a p r e p a r a t i v e s c a l e , a m i x t u r e o f compound 40 (120 mg, 0.50 mmole) and benzophenone (900 mg) was d i s s o l v e d w i t h a c e t o n e i n f i v e 10 ml p h o t o t u b e s , p h o t o l y z e d (A > 330 nm) and m o n i t o r e d by NMR t o a l m o s t complete c o n v e r s i o n . The f i n a l component r a t i o o f 40, 40c, 40b, and 40a by NMR was 10 : 2 : 78 : 10. The r e a c t i o n m i x t u r e was t r a n s f e r r e d t o d i e t h y l e t h e r , e x t r a c t e d w i t h NaOH^^q). washed w i t h d i e t h y l e t h e r ( t o remove benzophenone), r e a c i d i f i e d w i t h cone. H C l , e x t r a c t e d w i t h d i e t h y l e t h e r , washed w i t h w a t e r , d r i e d o ver MgS04 and e v a p o r a t e d . To the r e m a i n i n g o i l was added 5 ml o f anhydrous d i e t h y l e t h e r and the s o l u t i o n t r e a t e d w i t h e x c e s s diazomethane i n d i e t h y l e t h e r ( p r e p a r e d from D i a z a l d , A l d r i c h ) . The diazomethane was added d r o p w i s e a t room t e m p e r a t u r e u n t i l t h e s o l u t i o n s t a y e d y e l l o w ; the r e a c t i o n was s t i r r e d f o r a n o t h e r 20 min, quenched w i t h w a t e r and the e t h e r a l l a y e r s e p a r a t e d . Chromatography on s i l i c a g e l , e l u t i n g w i t h d i e t h y l e t h e r i n hexanes ( 1 : 9 v/v) gave 11 mg o f a 3 : 1 m i x t u r e o f compounds 29a and 29c i n the f i r s t band. The second band c o n t a i n e d 40 mg o f a w h i t e s o l i d ( y i e l d 3 0 % ) . R e c r y s t a l l i z a t i o n f r o m hexanes gave c o l o r l e s s r o d s w h i c h were c h a r a c t e r i z e d as d i m e t h y l 2 a , 2 b , 6 b , 6 c - t e t r a h y d r o b e n z o [ a ] c y c l o p r o p a -[ c d ] p e n t a l e n e - l , 2 - d i c a r b o x y l a t e ( 2 9 f ) ^ * ^ . MP: 86-87 °C ( l i t . ^ 86.5-87.0 °C). IR (KBr) Ujnax^ 2927 (m, CH) , 1729 ( s , C=0) , 1273 ( s , C-0) cm"^. ^H NMR (400 MHz) 5: 7.75-7.10 (m, 4H, a r o m a t i c ) , 4.23 ( d , IH, J = 6 Hz, Hgb), 3.73 ( s , 3H, m e t h y l ) , 3.71 ( s , 3H, m e t h y l ) , 3.50 (ddd, IH, J = 6,6,6 Hz, Hgc), 3.29 (dd, IH, J = 6,6 Hz, H2b), 3.00 (dd, IH, J = 6,6 Hz, H2a) Ppm. MS ( E I ) m/e: 270 (M+, 3 2 ) , 238 ( 4 5 ) , 210 ( 1 0 0 ) , 183 ( 4 8 ) , 152 ( 1 0 0 ) . A n a l . c a l c d . f o r C16H14O4: C, 71.10; H, 5.22. Found: C, 71.25; H, 5.27. S o l i d S t a t e P h o t o l y s i s C r y s t a l s o f 40 were p h o t o l y z e d (A > 290 nm) i n NMR tube s f o r 4 h and 15 h. These c r y s t a l s t u r n e d y e l l o w w i t h s l i g h t m e l t i n g . A n a l y s i s by NMR (400 MHz, DMSO-dg) showed no p h o t o p r o d u c t s . H y d r o l y s i s o f B e n z o s e m i b u l l v a l e n e 29f Compound 29f (26 mg, 9.6 x 10"^ mole) was s t i r r e d i n 0.5 ml o f e t h a n o l f o r 10 min and t o t h i s m i x t u r e was added 0.2 g o f NaOH i n 4 ml w a t e r . The r e a c t i o n was r e f l u x e d f o r 35 min, d i l u t e d t o 10 ml w i t h w a t e r , washed w i t h d i e t h y l e t h e r , a c i d i f i e d w i t h cone. H C l , e x t r a c t e d w i t h e t h e r , d r i e d w i t h MgS04, f i l t e r e d , and e v a p o r a t e d t o a f f o r d 18 mg o f a w h i t e s o l i d ( y i e l d 77%) . T h i s was c h a r a c t e r i z e d as 2a,2b,6b,6c - t e t r a h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 1 , 2 - d i c a r b o x y l i c A c i d ( 4 0 b ) . MP: > 300 °C (decomposes s l o w l y a t appro x . 150 °C). IR (KBr) Ujnax^ 3200-2200 ( b r v s , OH), 1699 ( s , C=0) , 1601 ( s ) , 1567 ( s ) , 1484 ( s ) , 1263 ( s ) cm"^. ^H NMR (4 0 0 M H z , CDCI3) 5: 7.25-7.05 (m, 4H, a r o m a t i c ) , 4.46 (d , IH, J = 6 Hz, Hgb), 3.50-3.38 (m, 2H, Hgb + Hg^), 3.33 (dd, IH, J = 6,6 Hz, H2a) Ppm. ^H NMR (400 MHz, DMSO-dg) 5: 9.4 ( b r s, 2H, 2 x OH), 7.50-7.05 (m, 4H, a r o m a t i c ) , 4.20 ( d , IH, J = 6 Hz, Hgb). 3.46 (ddd, IH, J = 6,6,6 Hz, Hgc), 3.34 (dd, IH, J = 6 Hz, H2b), 3.06 (dd, IH, J = 6,6 Hz, H2a) ppm. MS ( E I ) m/e: 242 (M+, 1 6 ) , 224 ( 5 5 ) , 152 ( 1 0 0 ) . E x a c t mass c a l c u l a t e d f o r Cii^BiQOi^: 242.0579, f o u n d 242.0588. H y d r o l y s i s o f B e n z o s e m i b u l l v a l e n e 29a Compound 3 (730 mg, 2.7 mmoles) was d i s s o l v e d i n 15 ml o f e t h a n o l and t o t h i s was added 5.6 g o f NaOH i n 100 ml o f w a t e r and the s o l u t i o n r e f l u x e d f o r 40 min. The c o o l e d s o l u t i o n was washed w i t h d i e t h y l e t h e r , a c i d i f i e d w i t h cone. H C l , e x t r a c t e d w i t h d i e t h y l e t h e r , washed w i t h w a t e r , d r i e d o v e r MgS04, f i l t e r e d , and e v a p o r a t e d t o g i v e 402 mg o f a w h i t e s o l i d ( y i e l d 6 1 % ) . R e c r y s t a l l i z a t i o n from a c e t o n i t r i l e gave w h i t e c r y s t a l s , c h a r a c t e r i z e d as 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a -[ c d ] p e n t a l e n e - 2 a , 6 c - d i c a r b o x y l i c a c i d ( 4 0 a ) . MP: 178-181 °C. IR (KBr) Ujuax^ 3200-2400 ( b r s, OH), 1697 ( s , C=0) , 1445 (m), 1299 (m) cm'^. ^H NMR (400 MHz, CDCI3) 5: 10.3-9.8 ( b r s, 2H, OH), 7.5-7.1 (m, 4H, a r o m a t i c ) , 5.84 (dd, IH, J = 5,3 Hz, H^), 5.40 ( d , IH, J = 5 Hz, H2), 4.56 ( s , IH, H2b), 4.55 ( d , IH, J = 3 Hz, Hg^ w i t h p a r t i a l o v e r l a p t o H2b) PPm. ^H NMR (200 MHz, acetone-dg) 5: 11.6-11.0 ( b r s, 2H, OH), 7.6-7.1 (m, 4H, a r o m a t i c ) , 5.85 (dd, IH, J = 5,3 Hz, H^), 5.40 ( d , IH, J = 5 Hz, H2), 4.50 ( d , IH, J = 3 Hz, Hgb), 4.40 ( s , IH, Hgb) Ppm. ^H NMR (400 MHz, DMSO-dg) S : 13.1-12.3 ( b r s, OH), 7.55-7.10 (m, 4H, a r o m a t i c ) , 5.78 (dd, IH, J = 5,3 Hz, H^), 5.30 ( d , IH, J = 5 Hz, H2), 4.35 ( d , 3H, J = 3 Hz, Hgb). 4.24 ( s , IH, Hgb) Ppm. MS ( E I ) m/e: (no M+ peak) 198 ( 7 ) , 196 ( 8 ) , 152 ( 2 0 ) , 78 ( 1 0 0 ) . MS (DCI-NH3) m/e: 260 (M + NH4+, 1 2 ) , 243 (M + 1, 4 3 ) , 225 ( 1 9 ) , 198 ( 1 0 0 ) , 153 ( 7 8 ) . A n a l , c a l c d . f o r C14H10O4: C, 69.42; H, 4.16. Found: C, 69.48; H, 4.15. DeuteriTim L a b e l l i n g Study C r y s t a l s o f 40-D (60 mg, 0.25 mmole) i n t h r e e 10 ml p h o t o t u b e s o f e t h y l a c e t a t e were p h o t o l y z e d (A > 290 nm). The r e a c t i o n was c o n t i n u e d u n t i l t h e s o l u t i o n was b r i g h t y e l l o w ( 3 h ) , t h e n e v a p o r a t e d and t h e p r o d u c t r e c r y s t a l l i z e d f rom i n a 5 : 1 ( v / v ) s o l u t i o n o f e t h y l a c e t a t e and hexanes t o gave 33 mg o f a n h y d r i d e 41d-D as c l e a r orange r o d s ( y i e l d 5 9 % ) . MP: 209-211 °C. ^H NMR (400 MHz, DMSO-dg) S : 7.40-7.25 (m, 2.05H, a r o m a t i c H2 + H3), 7.15-6.95 (m, 3.12H + 0.88D, a r o m a t i c H^ + H4 and v i n y l H5 + H I Q ) . 6.19 (m, 2.00H, v i n y l Hg + H9) ppm. I n a t r i p l e t - s e n s i t i z e d e x p e r i m e n t , compound 40-D (25 mg, 0.10 nunole) and benzophenone (10 mg) were d i s s o l v e d w i t h 1.5 ml DMSO-dg i n an NMR tube. T h i s was p h o t o l y z e d (A > 330 nm) f o r 45 min and d i r e c t l y a n a l y z e d by NMR (shown i n F i g u r e 3.10 o f t e x t ) . G. 1 , 4 - D i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l i c A n h y d r i d e (41) D i r e c t S o l u t i o n P h o t o l y s i s On an a n a l y t i c a l s c a l e , a n h y d r i d e 41 was p h o t o l y z e d (A > 290 nm) i n benzene and e t h y l a c e t a t e t o g i v e t h r e e p r o d u c t s (41a, 41b, and 41c) i n d e p e n d e n t o f s o l v e n t , whose r a t i o s however, v a r i e d w i t h c o n v e r s i o n . A n h y d r i d e 41 (15 mg, 6.7 x 10'^ mole) i n 1 ml o f CDCI3 was p h o t o l y z e d (A > 290 nm) i n a p h o t o t u b e u n t i l c o m p l e t e c o n v e r s i o n t o g i v e an NMR (GC) r a t i o 47 (51) : 18 (13) : 24 (19) o f 41a, 41b, and 41c, r e s p e c t i v e l y . From an a n a l y s i s o f the r e a c t i o n m i x t u r e s , 41a was d e t e r m i n e d t o be 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a ] c d ] p e n t a l e n e - 2 a , 6 c - d i c a r b o x y l i c a n h y d r i d e . NMR (400 MHz, CDCI3) 5: 7.5-7.0 (m, 4H, a r o m a t i c o v e r l a p p i n g w i t h 4 1 c ) , 5.90 (dd, IH, J = 6,3 Hz, Hj^) , 5.44 ( d , IH, J = 6 Hz, H2) , 4.57 ( d , IH, J = 3 Hz, Hgb), 4.45 ( s , IH, H2b) Ppm. GC-MS (DB-1, E I ) m/e: 224 (M+, 73), 198 ( 8 8 ) , 180 ( 7 0 ) , 154 ( 9 1 ) , 126 ( 1 0 0 ) , 76 ( 7 2 ) . E x a c t mass c a l c u l a t e d f o r C14H8O3: 224.0474, f o u n d 224.0465. Compound 41b was i d e n t i f i e d from the m i x t u r e as n a p h t h a l e n e -2 , 3 - d i c a r b o x y l i c a n h y d r i d e ^ ^ ^H NMR (400 MHz, CDCI3) S : 8.57 ( s , 2H, H^ and H4), 8.16 (m, 2H, H5 and Hg), 7.82 (m, 2H, Hg and H7) ppm. GC-MS (DB-1, E I ) m/e: 198 (M+, 9 0 ) , 154 ( 9 1 ) , 126 ( 1 0 0 ) , 98 ( 6 8 ) , 87 ( 7 0 ) , 77 ( 7 2 ) , 63 ( 7 9 ) . From t h e above m i x t u r e , 41c was c h a r a c t e r i z e d as 2a,2b,6b,6c-t e t r a h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - l , 2 - d i c a r b o x y l i c a n h y d r i d e . ^H NMR (400 MHz, CDCI3) S : 7.5-7.1 (m, 4H, a r o m a t i c o v e r l a p p i n g w i t h 4 1 a ) , 4.29 ( d , IH, J = 6 Hz, Hgt,) . 3.99 (ddd, IH, J = 6,6,6 Hz, Hgc). 3.67 (dd, IH, J = 6,6 Hz, H2b), 3.01 (dd, IH, J = 6,6 Hz, H2a) ppm. GC-MS (DB-1, E I ) m/e: 224 (M+, 3 6 ) , 198 ( 7 ) , 180 ( 3 3 ) , 152 (1 0 0 ) , 126 ( 2 0 ) . E x a c t mass c a l c u l a t e d f o r C14H8O3: 224.0473, f o u n d 224.0470. Compound 41 was a n a l y t i c a l l y p h o t o l y z e d (A > 290 nm) t h r e e t i m e s i n e t h y l a c e t a t e and the p h o t o p r o d u c t r a t i o s were m o n i t o r e d as a f u n c t i o n o f c o n v e r s i o n and p l o t t e d g r a p h i c a l l y i n t h e t e x t . R a t i o s were r e c o r d e d on GC (DB-1) w i t h t h e t e m p e r a t u r e program: 150 °C f o r 1 min, r a t e o f 5 °C/min t o 230 °C f o r 1 min. The r e l a t i v e GC r e s p o n s e o f t he compounds was c a l i b r a t e d from NMR i n t e g r a t i o n . A n h y d r i d e 41 (200 mg, 0.90 mmole) was d i s s o l v e d i n 500 ml o f e t h y l a c e t a t e and p h o t o l y z e d (A > 290 nm) t o complete c o n v e r s i o n . T h i s s o l u t i o n was t h e n s t i r r e d w i t h 100 ml d r y methanol f o r 10 h and e v a p o r a t e d . The r e s u l t i n g y e l l o w o i l was d i s s o l v e d i n anhydrous d i e t h y l e t h e r and t r e a t e d a t room t e m p e r a t u r e w i t h e x c e s s diazomethane ( f r o m D i a z a l d , A l d r i c h ) ; diazomethane was added d r o p w i s e u n t i l t he s o l u t i o n remained b r i g h t y e l l o w i n d i c a t i n g an e x c e s s o f u n r e a c t e d diazomethane. T h i s was s t i r r e d f o r a n o t h e r 30 min b e f o r e t h e r e a c t i o n was quenched o v e r a c i d i f i e d i c e , d i l u t e d w i t h d i e t h y l e t h e r . d r i e d w i t h MgSO^, f i l t e r e d , and e v a p o r a t e d . Chromatography gave t h r e e bands. The f i r s t was 20 mg ( y i e l d 8%) o f compound 3, f o l l o w e d by 43 mg o f d i m e t h y l n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l a t e ^ ^ ( y i e l d 2 0 % ) . MP: 51-53 °C ( l i t . ^ ^ 52-54 °C). IR (KBr) u^ax^ 1733 ( s , C=0), 1717 ( s , C=0), 1288 ( s , C-0) cm'^. NMR (400 MHz, CDCI3) 5: 8.25 ( s , 2H, H^ + H4), 7.91 (m, 2H, H5 7.62 (m, 2H, Hg + H7), 3.95 ( s , 6H, 2 x m e t h y l ) ppm. MS ( E I ) m/e: 244 (64, M+), 213 ( 1 0 0 ) , 183 ( 3 3 ) , 127 ( 8 1 ) , 63 ( 7 5 ) . The t h i r d band was 21 mg ( y i e l d 9%) o f compound 29f ( p r e v i o u s l y c h a r a c t e r i z e d ) . A c e t o n e - S e n s i t i z e d P h o t o l y s i s A n h y d r i d e 41 was p h o t o l y z e d (A > 290 nm) a n a l y t i c a l l y i n a c e t o n e and t h e r e a c t i o n was m o n i t o r e d by GC t o show complete c o n v e r s i o n t o two p r o d u c t s (41a and 4 1 c ) ; p r o l o n g e d p h o t o l y s i s r e s u l t e d i n the d e c o m p o s i t i o n o f 41c. The r a t i o o f 41a t o 41c a t low c o n v e r s i o n (12%) was 37 : 63 by GC w i t h the r e s p o n s e c a l i b r a t e d by NMR. I n an NMR s t u d y , compound 41 (15 mg) i n 1 ml o f a c e t o n e - d g was p h o t o l y z e d (A > 290 nm) t o complete c o n v e r s i o n and a n a l y z e d by NMR (GC) t o show a 64 (72) : 36 (28) r a t i o o f 41a t o 41c. S o l i d S t a t e P h o t o l y s i s On an a n a l y t i c a l s c a l e , c r y s t a l s o f 41 were p h o t o l y z e d (A > 260 nm) f o r 4 h and a n a l y z e d by GC. The c r y s t a l s were c r a c k e d and t u r n e d d a r k y e l l o w w i t h no s i g n o f m e l t i n g . Two p r o d u c t s were formed, 41a and 41c, i n a r a t i o o f 2 : 5 a t 7% c o n v e r s i o n . F o r NMR, c r y s t a l s o f 41 (approx . 10 mg) i n an NMR tube were p h o t o l y z e d u n t i l t h e r e was no f u r t h e r change i n the appearance o f the c r y s t a l s (13 h ) . The d a r k y e l l o w c r y s t a l s were d i s s o l v e d i n CDCI3 and a n a l y z e d by NMR (GC) w h i c h showed a 41 : 41a : 41c r a t i o o f 84 (92) : 4 (3) : 12 (5) r e s p e c t i v e l y . D e u t e r i u m L a b e l l i n g S t u d y Compound 41-D (20 mg) i n 2 ml o f CDCI3 was p h o t o l y z e d (A > 290 nm) t o c o m plete c o n v e r s i o n t o 41a-D, 41b-D, and 41c-D. T h i s m i x t u r e was was t r a n s f e r r e d t o an NMR tube and a n a l y z e d . The s i g n a l s f o r 41a-D a r e d e s c r i b e d below. NMR (400 MHz) 5: 7.5-7.1 (m, 3.50H + 0.50D, a r o m a t i c o v e r l a p p i n g w i t h 41c-D), 5.91 (m, l.OOH, H^), 5.48 ( d , l.OOH, J = 6 Hz, H2), 4.57 ( d i s t o r t e d s, 0.88H+0.12D, Hg^). 4.42 ( s , 0.63H + 0.37D, H2b) ppm. The s i g n a l s f o r 41b-D a r e below. ^H NMR (400 MHz) 8: 8.59 ( s , l . l l H + 0.89D, H^  + H4), 8.14 (m, 1.33H + 0.67D, H5 + Hg), 7.82 (m, 2.00H, Hg + H^) PPm. Below a r e t h e s i g n a l s f o r 41c-D. ^H NMR (400 MHz) 5: 7.5-7.1 (m, 3.5H + 0.5D, a r o m a t i c o v e r l a p p i n g w i t h 41a-D), 4.30 ( d , 0.56H + 0.44D, J = 6 Hz, Hgb), 4.00 (ddd, l.OOH, J = 6,6,6 Hz, Hgc). 6.64 (dd, 0.78H + 0.22D, J = 6,6 Hz, H2b), 3.00 (dd, l.OOH, J = 6,6 Hz, H2a)• D. 2,3-Dlbenzoyl-l,4-dlhydro-l,4-ethenonaphthalene (42) Direct Solution Photolysis S m a l l samples o f compound 42 were d i s s o l v e d i n benzene and a c e t o n i t r i l e f o r p h o t o l y s i s (A > 330 nm). The r e a c t i o n was m o n i t o r e d by GC and shown t o be s o l v e n t - i n d e p e n d e n t w i t h t he f o r m a t i o n o f o n l y one p r o d u c t (42a). F u r t h e r p h o t o l y s i s c a u s e d t he f o r m a t i o n o f a se c o n d a r y p h o t o p r o d u c t (42c). I n an NMR s t u d y , compound 42 was p h o t o l y z e d (A > 330 nm) w i t h CDCI3 i n an NMR tube f o r 10 min u t e s and a n a l y z e d by NMR (GC) t o a 42 : 42a r a t i o o f 84 (92) : 16 ( 8 ) . On a p r e p a r a t i v e s c a l e , a s o l u t i o n o f 42 (35 mg, 9.7 x 10'^ mole) i n 4 ml o f benzene i n a 10 ml p h o t o t u b e was p h o t o l y z e d (A > 330 nm) t o complete c o n v e r s i o n . The r e s u l t i n g m i x t u r e o f 42a and 42c was chromatographed t w i c e , e l u t i n g w i t h a d i e t h y l e t h e r : hexanes (1:9 v/v) s o l u t i o n . T h i s gave 20 mg o f an i n s e p a r a b l e 75 : 25 m i x t u r e o f 42a and 1 , 6 c - d i b e n z o y l - 2 b , 6 b ( 2 a H ) - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e (42c) , from w h i c h t h e l a t t e r i s c h a r a c t e r i z e d below. % NMR (400 MHz) 5: 8.0-7.1 (m, 14H, a r o m a t i c o v e r l a p p i n g w i t h 42a), 6.08 ( d , IH, J = 3 Hz, H2), 4.90 ( s , IH, Hg^), 4.12 ( d , IH, J = 8 Hz, H2b), 3.78 (dd, IH, J = 8,3 Hz, H2a) Ppm-GC-MS (DB-1, E I ) m/e: 362 (M+, 2 ) , 257 ( 3 ) , 105 ( 1 0 0 ) , 77 ( 3 1 ) . E x a c t mass c a l c u l a t e d f o r C26H2^802- 362.1307, f o u n d 362.1295. Benzophenone-sensitized Photolysis of Compound 42 On an a n a l y t i c a l s c a l e , a s m a l l amount o f compound 42 and a f i v e - f o l d e x c e s s (w/w) o f benzophenone were d i s s o l v e d i n benzene and p h o t o l y z e d (A > 330 run) t o complete c o n v e r s i o n . GC m o n i t o r i n g showed the f o r m a t i o n o f 42a; o n l y t r a c e amounts o f 42c was d e t e c t e d . On a p r e p a r a t i v e s c a l e , a s o l u t i o n o f 42 (27 mg, 7.5 x 10"^ mole) and benzophenone (300 mg, 1.7 mmole) i n 8 ml o f benzene was p h o t o l y z e d (A > 330 nm) t o complete c o n v e r s i o n . Chromatography on s i l i c a g e l e l u t i n g w i t h d i e t h y l e t h e r : p e t r o l e u m e t h e r (30-60 °C) (1 : 9 v/v) gave benzophenone i n the f i r s t band. The second band c o n s i s t e d o f 16 mg o f 2 a , 6 c - d i b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o -p r o p a [cd] p e n t a l e n e (42a) as a c o l o r l e s s o i l ( y i e l d 5 9 % ) . IR ( n e a t ) Vj^^^^: 1682 ( s , C=0) , 1599 (m) , 1279 ( s ) cm"!. NMR (400 MHz) 5: 8.0-7.1 (m, 14H, a r o m a t i c ) , 5.94 (dd, IH, J = 5,2 Hz, H i ) , 5.50 ( d , IH, J = 5 Hz, H2), 4.63 ( s , IH, H2b), 4.40 ( d , IH, J = 2 Hz, Hg^) ppm. MS ( E I ) m/e: 362 (M+, 7 0 ) , 105 ( 1 0 0 ) , 77 ( 2 0 ) . E x a c t mass c a l c u l a t e d f o r C26H18O2: 362.1307, f o u n d 362.1298. S o l i d S t a t e P h o t o l y s i s o f Compound 42 C r y s t a l s o f 42 were p l a c e d i n an NMR tube and p h o t o l y z e d (A > 290 nm) f o r 15 h t o g i v e u n m e l t e d y e l l o w c r y s t a l s . A n a l y s i s by NMR i n d i c a t e d an 8% c o n v e r s i o n t o two p r o d u c t s , 42a and 42b i n a 1 : 1 r a t i o . I n a l o n g e r p h o t o l y s i s (45 h ) , the u n m e l t e d y e l l o w c r y s t a l s were a n a l y z e d by NMR w h i c h showed a 14% c o n v e r s i o n t o a n o t h e r 1 : 1 r a t i o o f 42a t o 42b. I n a p r e p a r a t i v e s t u d y , c r y s t a l s o f 42 (43 mg, 1.2 x 10"^ mole) were c r u s h e d between two p a i r s o f m i c r o s c o p e s l i d e s and p h o t o l y z e d (A > 330 nm) f o r 20 h. The unmelt e d y e l l o w c r y s t a l s were a n a l y z e d by NMR w h i c h i n d i c a t e d a 42a : 42b r a t i o o f 59 : 41 a t 38% c o n v e r s i o n . Chromatography on s i l i c a g e l u s i n g a 1 ; 9 ( v / v ) m i x t u r e o f d i e t h y l e t h e r t o hexanes as the e l u e n t gave t h r e e o v e r l a p p i n g bands. The f i r s t band c o n t a i n e d s t a r t i n g m a t e r i a l 42; second band c o n s i s t e d o f 42a and t h e t h i r d band was r e c h r o m a t o g r a p h e d two more t i m e s under the same c o n d i t i o n s as above t o g i v e 4 mg o f 1 , 2 - d i b e n z o y l - 2 a , 2 b , 6 b , 6 c - t e t r a -hydrobenzo [a] c y c l o p r o p a [ c d ] p e n t a l e n e (42b) as a c o l o r l e s s o i l ( y i e l d 9%). IR ( n e a t ) v^^y.: 1651 ( s , C=0) , 1597 (m) , 1273 ( s ) cm'^. NMR (400 MHz) 5: 7.6-6.7 (m, 14H, a r o m a t i c ) , 4.61 ( d , IH, J = 6 Hz, Hgb). 3.64 (ddd, IH, J = 6,6,6 Hz, Hg^). 3.49 (dd, IH, J = 6,6 Hz, H2b), 3.23 (dd, IH, J = 6,6 Hz, H2a) Ppm. MS ( E l ) m/e: 362 (M+, 5 ) , 105 ( 1 0 0 ) , 77 ( 4 4 ) . E x a c t mass c a l c u l a t e d f o r C26H18O2: 362.1307, f o u n d 362.1312. P h o t o l y s i s o f B e n z o s e m i b u l l v a l e n e 42a On an a n a l y t i c a l s c a l e , compound 42a was p h o t o l y z e d (A > 330 nm) i n benzene. One p r o d u c t (42c) was d e t e c t e d by GC (DB-1) a t a p h o t o s t a t i o n a r y s t a t e c o m p o s i t i o n o f 59 : 41 = 42a : 42c. E. M e t h y l 2 - B e n z o y l - l , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 3 - c a r b o x y l a t e (43) D i r e c t S o l u t i o n P h o t o l y s i s S o l u t i o n s o f 43 i n benzene, a c e t o n i t r i l e , hexanes, and m e t hanol were a n a l y t i c a l l y p h o t o l y z e d (A > 330 nm) t o c o m p l e t e c o n v e r s i o n , m o n i t o r e d by GC (DB-1). Two major p h o t o p r o d u c t s , s u b s e q u e n t l y shown t o have s t r u c t u r e s 43a and 43b, were seen a l o n g w i t h some mi n o r p r o d u c t s . The r e a c t i o n was i n d e p e n d e n t o f s o l v e n t . A s o l u t i o n o f k e t o - e s t e r 43 (25 mg) i n 1 ml CDCI3 was p h o t o l y z e d as above t o c o m p l e t e c o n v e r s i o n , and the i n t e g r a t e d NMR s p e c t r u m o f the r e s u l t i n g m i x t u r e showed s i x p r o d u c t s (43a, 43b, 43h, 43c, 43d, and 43e) a t a r a t i o o f 50 : 25 : 17 : t r a c e : 8 : t r a c e , r e s p e c t i v e l y . A s o l u t i o n o f compound 43 (130 mg, 0.411 mmole) i n 40 ml o f benzene was p l a c e d i n f o u r 10 ml p h o t o t u b e s and p h o t o l y z e d t o c o m p l e t e c o n v e r s i o n as m o n i t o r e d by GC. The benzene was e v a p o r a t e d and t h e r e s u l t i n g y e l l o w o i l chromatographed on s i l i c a g e l u s i n g d i e t h y l e t h e r and hexanes (1 : 19 v/v) as the e l u e n t . The f i r s t band c o n t a i n e d 47 mg o f a w h i t e s o l i d ( y i e l d 3 6 % ) . R e c r y s t a l l i z a t i o n from hexanes gave two c r y s t a l m o r p h o l o g i e s , n e e d l e s and p r i s m s , o f m e t h y l 2 a - b e n z o y l -2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 6 c - c a r b o x y l a t e ( 4 3 a ) . MP: ( n e e d l e s ) 106-107 °C, ( p r i s m s ) 113-114 °C. IR (KBr, n e e d l e s ) ^niax^ ^^33 ( s , e s t e r C=0), 1674 ( s , b e n z o y l C=0), 1224 ( s , C-0) cm-1. IR (KBr, p r i s m s ) ^max^ ^723 ( s , e s t e r C=0), 1677 ( s , b e n z o y l C=0), 1225 ( s , C-0) c m " l . % NMR ( 4 0 0 M H z ) 5: 8.0-7.2 (m, 9H, a r o m a t i c ) , 5.93 (dd, IH, J = 3,5 Hz, H^), 5.27 ( d , IH, J = 5 Hz, H2), 4.69 ( d , IH, J = 3 Hz, Hgb), 4.57 ( s , IH, H2b), 3.45 ( s , 3H, m e t h y l ) ppm. MS ( E I ) m/e: 316 (M+, 2 8 ) , 256 ( 3 1 ) , 228 ( 4 0 ) , 152 ( 3 0 ) , 105 ( 1 0 0 ) , 77 ( 8 0 ) . E x a c t mass c a l c u l a t e d f o r C21H16O3: 316.1100, f o u n d 316.1103. UV (CH3CN) X^^^: 244 (e 14000), 277 sh (e 3100) nm. A n a l . C a l c d . f o r C21H16O3: C, 79.73; H, 5.10. Found: C, 79.48; H, 5.15. The second band c o n t a i n e d 29 mg o f a w h i t e s o l i d ( y i e l d 2 2 % ) . R e c r y s t a l l i z a t l o n from pentane gave p r i s m s and t h i s compound was i d e n t i f i e d as m e t h y l 6 c - b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] -p e n t a l e n e - l ( 2 a H ) - c a r b o x y l a t e ( 4 3 b ) . MP: 100-101 °C. IR (KBr) ^^^^ ( s , e s t e r C=0) , 1663 ( s , b e n z o y l C=0) , 1253 ( s , C-0) c m ' l . NMR (300 MHz) 5: 7.7-7.2 (m, 9H, a r o m a t i c ) , 6.29 ( d , IH, J = 3 Hz, H2), 4.62 ( s , IH, Hgb), 4.07 ( d , IH, J = 8 Hz, H g t ) , 3.72 ( s , 3H, m e t h y l ) , 3.66 (dd, IH, J = 8,3 Hz, H2a) PPm. MS ( E I ) m/e: 316 (M+, 7 ) , 284 ( 8 ) , 180 ( 2 3 ) , 152 ( 5 0 ) , 105 ( 1 0 0 ) , 77 ( 7 2 ) . E x a c t mass c a l c u l a t e d f o r C21H16O3: 316.1100, f o u n d 316.1106. UV (CH3CN) An,aj^: 244 (e 16500), 280 sh (e 4900) nm. A n a l , c a l c d . f o r C2iH3^503: C, 79.73; H, 5.10. Found: C, 79.80; H, 5.10. B e n z o p h e n o n e - s e n s i t i z e d P h o t o l y s i s I n a 0.2 ml a n a l y t i c a l p h o t o t u b e , a benzene s o l u t i o n o f 0.02 M i n 43 and c a . 0.2 M i n benzophenone was p h o t o l y z e d t h r o u g h u r a n i u m g l a s s (A > 330 nm). GC showed the f o r m a t i o n o f two p h o t o p r o d u c t s (43a and 4 3 h ) , however, e x t e n d e d p h o t o l y s i s gave s i m i l a r r e s u l t s t o d i r e c t i r r a d i a t i o n . S o l i d S t a t e P h o t o l y s i s C r y s t a l s o f 43 were p h o t o l y z e d (A > 290 nm) i n n i t r o g e n f i l l e d P y r e x a n a l y t i c a l p h o t o t u b e s . GC showed the f o r m a t i o n o f t h r e e new p r o d u c t s : 43d, 43e, and 43f. N e i t h e r 43a n o r 43b were d e t e c t e d a t low c o n v e r s i o n s , b u t a t c o n v e r s i o n s above c a . 20%, the c r y s t a l s began t o m e l t and s t i c k t o the tube s u r f a c e , and d e t e c t a b l e amounts o f compound 43a began t o form. I n an NMR s t u d y , c r y s t a l s ( a p p r o x . 10 mg) o f 43 were p h o t o l y z e d i n an NMR tube u n t i l t he sample t u r n e d y e l l o w b u t showed no s i g n o f m e l t i n g . NMR a n a l y s i s o f t h e r e a c t i o n m i x t u r e a t 17% c o n v e r s i o n i n d i c a t e d a 43d : 43e : 4 3 f r a t i o o f 50 : 30 : 20. On a p r e p a r a t i v e s c a l e , c r y s t a l s o f 43 (291 mg, 0.921 mmole) were p l a c e d i n t h r e e v i a l s and p h o t o l y z e d (A > 290 nm) u n t i l t h e c r y s t a l s were y e l l o w b u t showed no s i g n s o f m e l t i n g (18% c o n v e r s i o n by GC). The c r y s t a l s were d i s s o l v e d i n benzene and chromatographed on s i l i c a g e l u s i n g a s o l v e n t s y s t e m o f hexanes and d i e t h y l e t h e r , 92:8 ( v / v ) , t o g i v e t h r e e o v e r l a p p i n g bands. The f i r s t band was r e c h r o m a t o g r a p h e d as above t o g i v e 13 mg o f m e t h y l 6 c - b e n z o y l - 2 a , 2 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e -6 b - c a r b o x y l a t e ( 4 3 f , y i e l d 4.5%). R e c r y s t a l l i z a t i o n from hexanes gave c o l o r l e s s n e e d l e s . MP: 162-163 °C. IR (KBr) Umax-' 1^42 ( s , e s t e r C=0) , 1668 ( s , b e n z o y l C=0) , 1285 ( s , C-0) cm'^. NMR (300 MHz) 6: 7.7-7.1 (m, 9H, a r o m a t i c ) , 6.06 ( d , IH, J = 5 Hz, H i ) , 5.40 (dd, IH, J = 5,3 Hz, Hg), 4.07 ( d , IH, J = 8 Hz, H2b), 3.44 (dd, IH, J = 8,3 Hz, Hga), 3.12 ( s , 3H, m e t h y l ) ppm. S p i n d e c o u p l i n g e x p e r i m e n t s : i r r a d i a t i o n o f Hj^ c o l l a p s e s Hg t o a d o u b l e t ( J = 3 H z ) ; i r r a d i a t i o n o f Hg c o l l a p s e s H^ t o a s i n g l e t and s i m p l i f i e s Hga t o a d o u b l e t ( J = 8 H z ) ; i r r a d i a t i o n o f Hg^ c o l l a p s e s Hg t o a d o u b l e t ( J = 5 Hz) and c o l l a p s e s Hg^ t o a s i n g l e t ; i r r a d i a t i o n o f Hgb s i m p l i f i e s Hg^ t o a d o u b l e t ( J = 3 H z ) . MS ( E I ) m/e: 316 (M+, 1 2 ) , 284 ( 1 3 ) , 256 ( 2 0 ) , 152 ( 2 0 ) , 105 ( 1 0 0 ) , 77 ( 3 5 ) . E x a c t mass c a l c u l a t e d f o r C2iH3^603: 316.1100, f o u n d 316.1098. UV (CH3CN) X^^^: 240 (€ 9500), 280 sh (e 1760) nm. A n a l , c a l c d . f o r C 2 i % 6 0 3 : C, 79.73; H, 510. Found C, 79.73; H, 5.16. The a s s i g n e d s t r u c t u r e was a l s o s u p p o r t e d by an X - r a y c r y s t a l s t r u c t u r e d e t e r m i n a t i o n . The c r y s t a l d a t a a r e as f o l l o w s : ^21^1603' o r t h o r h o m b i c , space group Pbca, a = 33.023(2)Â, b = 11.210(1)Â, c = 8.637(2)Â, V = 3197(1 ) Â 3 , Z = 8, = 1.314 g/ml, R = 0.042. The second band was 190 mg o f r e c o v e r e d s t a r t i n g m a t e r i a l and t h e t h i r d band was r e c h r o m a t o g r a p h e d as above t o g i v e 26 mg o f an i n s e p a r a b l e o i l y m i x t u r e o f p h o t o p r o d u c t s 43d and 43e (75 : 2 5 ) . Compound 43d was c h a r a c t e r i z e d as a m i x t u r e w i t h 43e. IR ( n e a t , 1:1 m i x t u r e w i t h 43e) u^ax- ^^^^ ' e s t e r C=0), 1673 ( s , b e n z o y l C=0), 1267 ( s , C-0) cm'^. NMR (300 MHz, CDCI3) S : 7.6-6.8 (m, 9H, a r o m a t i c o v e r l a p p i n g w i t h 4 3 e ) , 4.40 ( d , IH, J = 6 Hz, Hg^), 3.62 (ddd, IH, J = 6,6,6 Hz, Hgc s l i g h t l y o v e r l a p p i n g w i t h 43e) , 3.45 ( s , 3H, m e t h y l ) , 3.40 (dd, IH, J = 6,6 Hz, H2b), 3.00 (dd, IH, J = 6,6 Hz, H2a) Ppm. The peaks o f 43d c a n be d i s t i n g u i s h e d from t h o s e o f 43e by a n a l y z i n g s e v e r a l s p e c t r a w i t h d i f f e r e n t c o m p o s i t i o n s o f 43d and 43e, v a r y i n g f r o m 1 : 1 t o 4 : 1, r e s p e c t i v e l y . S p i n d e c o u p l i n g e x p e r i m e n t s : i r r a d i a t i o n o f H2b m o d i f i e s Hgj. and H2a; i r r a d i a t i o n o f H2a m o d i f i e s H2b and Hg^ ,; i r r a d i a t i o n o f Hgb m o d i f i e s Hgj,; i r r a d i a t i o n o f Hg^ , c o l l a p s e s Hg^ t o a s i n g l e t and H2a t o a d o u b l e t ( J = 6 Hz) and H2b t o a d o u b l e t ( J = 6 H z ) . L a n t h a n i d e s h i f t r e a g e n t s t u d i e s were a l s o p e r f o r m e d t o d i s t i n g u i s h Hga from ^2h- r e a s o n e d t h a t ^2a' b e i n g c l o s e r t o t h e s i t e o f s h i f t r e a g e n t c o m p l e x a t i o n ( t h e c a r b o n y l s u b s t i t u e n t s ) , s h o u l d be more s t r o n g l y d e s h i e l d e d t h a n ^2h-S u c c e s s i v e a d d i t i o n s o f 0, 4, 10, 20, and 30 mole % o f E u ( h f c ) 3 ( f r o m A l d r i c h ) t o the NMR m i x t u r e o f 43d and 43e showed a g r e a t e r s h i f t a t S 3.00 compared t o t h a t a t 5 3.40. T h e r e f o r e t h e s e s i g n a l s were a s s i g n e d t o Hg^ and Hg^ r e s p e c t i v e l y . The r e s u l t s a r e p r e s e n t e d g r a p h i c a l l y i n the t e x t . GC-MS ( E I , DB-1) m/e: 316 (M+, 1 0 ) , 284 ( 4 0 ) , 179 ( 1 0 ) , 152 ( 1 5 ) , 105 ( 1 0 0 ) , 77 ( 6 9 ) . E x a c t mass c a l c u l a t e d f o r C21H15O3: 316.110, f o u n d 316.1097. The s p e c t r a l d a t a f o r 43e a r e from m i x t u r e s w i t h 43d and a r e d e s c r i b e d below. IR ( n e a t , 1:1 m i x t u r e w i t h 43d) w^ax- d e s c r i b e d above. NMR (300 MHz, CDCI3) 6: 7.6-6.8 (m, 9H, a r o m a t i c o v e r l a p p i n g w i t h 4 3 d ) , 4.35 ( d , IH, J = 6 Hz, Hg^), 3.58 (ddd, IH, J = 6,6,6 Hz, Hgc s l i g h t l y o v e r l a p p i n g w i t h 4 3 d ) , 3.33 (dd, IH, J = 6,6 Hz, Hgb), 3.18 (dd, IH, J = 6,6 Hz, Hga o v e r l a p p i n g w i t h m e t h y l ) , 3.17 ( s , 3H, m e t h y l o v e r l a p p i n g w i t h Hga) ppm. S p i n d e c o u p l i n g e x p e r i m e n t s : i r r a d i a t i o n o f Hg^ m o d i f i e s Hga and ^èc' i r r a d i a t i o n o f Hga m o d i f i e s Hg^ and Hg^ ,; i r r a d i a t i o n o f Hg^ m o d i f i e s Hg(,; i r r a d i a t i o n o f Hg^ , c o l l a p s e s Hg^ t o a s i n g l e t and m o d i f i e s Hga and Hgb- A s h i f t r e a g e n t s t u d y was p e r f o r m e d as above t o a s s i g n Hga and Hgb (see t e x t ) . GC-MS ( E I , DB-1) m/e: 316 (M+, 5 ) , 284 ( 7 ) , 152 ( 8 ) , 105 ( 1 0 0 ) , 77 ( 3 8 ) . E x a c t mass c a l c u l a t e d f o r C 2 i H i g 0 3 : 316.1100, f o u n d 316.1103. P h o t o l y s i s o f Compound 43 i n P o l y [ m e t h y l m e t h a c r y l a t e ] (PMMA) F i l m Compound 43 (3 mg, 1 x 10'^ mole) was d i s s o l v e d a l o n g w i t h 30 mg o f medium m o l e c u l a r w e i g h t p o l y ( m e t h y l m e t h a c r y l a t e ) ( f r o m A l d r i c h ) i n 2 ml o f methylene c h l o r i d e and s p r e a d o v e r t h r e e m i c r o s c o p e s l i d e s . The s o l v e n t was e v a p o r a t e d under vacuum f o r 24 h, and t h e r e s u l t i n g c l e a r f i l m s were p h o t o l y z e d a t 20 °C t h r o u g h a P y r e x f i l t e r (A > 290 nm). F o r m o n i t o r i n g t h e r e a c t i o n , p o r t i o n s o f f i l m were d i s s o l v e d i n CH2CI2 and methanol was added t o p r e c i p i t a t e t h e PMMA p r i o r t o GC a n a l y s i s . I r r a d i a t i o n t o co m p l e t e c o n v e r s i o n gave f i v e p r o d u c t s (43a, 43b, 43h, 43d, and 43e) i n a GC r a t i o o f 34 : 12 : 30 : 12 : 12, r e s p e c t i v e l y . A low te m p e r a t u r e p h o t o l y s i s (-50 °C) gave s i m i l a r r e s u l t s , b u t the r a t e was much s l o w e r . On a p r e p a r a t i v e s c a l e , a s o l u t i o n o f 43 (200 mg, 0.63 mmole) and 2.0 g o f medium m o l e c u l a r w e i g h t PMMA (f r o m A l d r i c h ) i n 30 ml o f CH2CI2 was p o u r e d i n t o a 24 x 5 cm P y r e x vacuum-safe tube and s p r e a d e v e n l y o v e r t he i n n e r s u r f a c e . The s o l v e n t was removed by f l u s h i n g w i t h n i t r o g e n f o r 30 min f o l l o w e d by pumping on a vacuum l i n e f o r 50 h r . The tube was s e a l e d under n i t r o g e n and p h o t o l y z e d (A > 290 nm) a t 20 °C. The tube was r o t a t e d e v e r y 15 min and t h e r e a c t i o n m o n i t o r e d by GC t o a maximum c o n v e r s i o n o f 93%. The polymer was d i s s o l v e d i n 100 ml o f CH2CI2 and 75 ml o f methanol was added. The s o l v e n t was e v a p o r a t e d u n t i l a p p r o x i m a t e l y 75 ml remained, a t w h i c h p o i n t most o f the polymer had p r e c i p i t a t e d . The m i x t u r e was s t i r r e d f o r a n o t h e r 30 min t o p r e c i p i t a t e t he r e s t o f the polymer and t he s o l u t i o n was f i l t e r e d and e v a p o r a t e d t o a y e l l o w o i l . Chromatography on s i l i c a g e l u s i n g h e x a n e s - d i e t h y l e t h e r , 9:1 v/v, as the e l u e n t gave t h r e e major bands. The f i r s t band c o n s i s t e d o f 61 mg o f 43a ( y i e l d 3 1 % ) . The second band c o n t a i n e d 27 mg o f a w h i t e s o l i d ( y i e l d 1 4 % ) . R e c r y s t a l l i z a t i o n from hexanes gave p r i s m s w h i c h were c h a r a c t e r i z e d as m e t h y l 6 c - b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a -[ c d ] p e n t a l e n e - 2 a - c a r b o x y l a t e ( 4 3 h ) . MP: 129-130 °C. IR (KBr) Vjnax- ^718 ( s , e s t e r C=0), 1676 ( s , b e n z o y l C=0), 1287 ( s , C-0) cm-1. NMR (300 MHz) 5: 7.9-7.1 (m, 9H, a r o m a t i c ) , 5.91 (dd, IH, J = 5,2 Hz, H]_), 5.64 ( d , IH, J = 6 Hz, Hg) , 4.55 ( s , IH, Hgb) , 4.30 ( d , IH, J = 2 Hz, Hgt,) . 3.70 ( s , 3H, m e t h y l ) ppm. MS ( E I ) m/e: 316 (M+, 2 5 ) , 284 ( 4 9 ) , 256 ( 2 5 ) , 152 ( 1 5 ) , 105 ( 1 0 0 ) , 77 ( 3 0 ) . E x a c t mass c a l c u l a t e d f o r C21H16O3: 316.1100, f o u n d 316.1105. UV (CH3CN) A^a^: 245 (e 25800), 278 sh (e 3900) nm. A n a l , c a l c d . f o r C21H16O3: C, 79.73; H, 5.10. Found: C, 79.82; H, 5.14. The t h i r d band c o n t a i n e d a 3 : 1 m i x t u r e o f compounds 43d t o 43e as i n d i c a t e d by GC. P h o t o s t a t i o n a r y S t a t e o f B e n z o s e m i b u l l v a l e n e s 43a and 43c C r y s t a l s o f 43a were d i s s o l v e d i n benzene, a c e t o n i t r i l e , and ac e t o n e t o make up a p p r o x i m a t e l y 0.01 M s o l u t i o n s , and a n a l y t i c a l l y p h o t o l y z e d (A > 290 nm). The r e a c t i o n s m o n i t o r e d by GC t o show th e f o r m a t i o n o f one compound, s u b s e q u e n t l y c h a r a c t e r i z e d as 43c. The r e a c t i o n was ind e p e n d e n t o f s o l v e n t , e x c e p t t h a t the r a t e o f r e a c t i o n i n acet o n e was n o t i c e a b l y s l o w e r . I n a l l t h r e e c a s e s , the 43a : 43c r a t i o a f t e r p r o l o n g e d i r r a d i a t i o n ( c o r r e c t e d f o r d e t e c t o r r e s p o n s e by NMR) was 8 : 2 . Independent a n a l y t i c a l p h o t o l y s i s o f compound 43c l e d t o t h e same r a t i o . On a p r e p a r a t i v e s c a l e , a s o l u t i o n o f 50 mg (0.16 mmole) o f compound 43a i n 40 ml o f benzene was p h o t o l y z e d i n f o u r 10 ml p h o t o t u b e s t h r o u g h a P y r e x f i l t e r (A > 290 nm) t o a t i m e - i n v a r i a n t 43a : 43c r a t i o o f 83 : 17. The s o l v e n t was c o n c e n t r a t e d t o a y e l l o w o i l and chromatographed on s i l i c a g e l u s i n g d i e t h y l e t h e r and hexanes ( 1 : 9 v/v) as t h e s o l v e n t . Two o v e r l a p p i n g bands were e l u t e d , compound 43a f i r s t , f o l l o w e d by 43c. A p a r t i a l s e p a r a t i o n o f 43c from 43a was a c h i e v e d , and the p u r e 43a i s o l a t e d (32 mg) was r e p h o t o l y z e d and chromatographed as above t o g i v e p a r t i a l s e p a r a t i o n o f 43c a g a i n . The f r a c t i o n s o f 43c were combined and r e c h r o m a t o g r a p h e d as above t o g i v e c o m p lete s e p a r a t i o n r e s u l t i n g i n 12 mg o f a w h i t e s o l i d ( y i e l d 2 4 % ) . R e c r y s t a l l i z a t i o n f rom hexanes gave c o l o r l e s s n e e d l e s o f m e t h y l 1-benzoyl-2b,6b-d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n a t a l e n e - 6 c ( 2 a H ) - c a r b o x y l a t e ( 4 3 c ) . MP: 100-101 °C. IR (KBr) Vjj^siK- 1726 ( s , e s t e r C=0) , 1639 ( s , b e n z o y l C=0) , 1329 ( s ) , 1267 ( s , C-0), 1213 ( s ) c m ' l . NMR (300 MHz) 5: 7.6-7.1 (m, 9H, a r o m a t i c ) , 5.95 ( d , IH, J = 3 Hz, H2), 4.96 ( s , IH, Hgb), 3.97 ( d , IH, J = 8 Hz, H2b)> 3.74 ( s , 3H, m e t h y l ) , 3.54 (dd, IH, J = 8,3 Hz, H2a) PPm. MS ( E l ) m/e: 316 (M+, 2 0 ) , 284 ( 4 ) , 256 ( 1 0 ) , 152 ( 1 3 ) , 105 ( 1 0 0 ) , 77 ( 4 5 ) . E x a c t mass c a l c u l a t e d f o r C21H16O3: 316.1100, f o u n d 316.1100. A n a l . c a l c d . f o r C2iH]^603: C, 79.73; H, 5.10. Found: C, 79.63; H, 5.21. Photostationary State of Benzosemibullvalenes 43f and 43g C r y s t a l s o f 43f were d i s s o l v e d i n benzene, a c e t o n i t r i l e , and a c e t o n e t o make up a p p r o x i m a t e l y 0.01 M s o l u t i o n s and a n a l y t i c a l l y p h o t o l y z e d (A > 290 nm). GC m o n i t o r i n g o f the r e a c t i o n i n d i c a t e d the f o r m a t i o n o f one v o l a t i l e p r o d u c t , s u b s e q u e n t l y shown t o have t h e s t r u c t u r e 43g, a t a p h o t o s t a t i o n a r y s t a t e r a t i o o f 43f : 43g = 2 : 8. Independent a n a l y t i c a l p h o t o l y s i s o f 43g i n benzene a l s o l e d t o t h i s r a t i o , b u t p r o l o n g e d p h o t o l y s i s c a u s e d i r r e v e r s i b l e d e c o m p o s i t i o n o f the sample. The r e s u l t s were the same i n a l l t h r e e s o l v e n t s , e x c e p t t h a t t h e r a t e o f r e a c t i o n was n o t i c e a b l y s l o w e r i n a c e t o n e . P h o t o p r o d u c t 43g was i s o l a t e d by p h o t o l y s i s o f a s o l u t i o n o f 7.5 mg (0.025 mmole) o f 43f i n 1 ml o f CDCI3. The p h o t o l y s i s was h a l t e d a t a 43f : 43g r a t i o o f 57 : 43 i n o r d e r t o a v o i d p h o t o d e c o m p o s i t i o n . The m i x t u r e was chromatographed on s i l i c a e l u t i n g w i t h d i e t h y l e t h e r and hexanes (1 : 9 v / v ) . Compound 43f e l u t e d f i r s t f o l l o w e d c l o s e l y by 43g. Pure 43f was r e p h o t o l y z e d and chromatographed as above. The two p u r e p o r t i o n s were combined t o g i v e 3 mg o f a c o l o r l e s s o i l ( y i e l d 40%) o f m e t h y l 6 c - b e n z o y l - 2 a , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] -p e n t a l e n e - 2 b - c a r b o x y l a t e (43g). IR ( n e a t ) ^max^ 1^28 ( s , e s t e r C=0), 1675 ( s , b e n z o y l C=0), 1264 ( s , C-0) c m ' l . % NMR (300 MHz) 6: 7.9-7.1 (m, 9H, a r o m a t i c ) , 5.87 (dd, IH, J = 5,2 Hz, Hi), 5.42 (dd, IH, J = 5,3 Hz, Hg), 4.27 ( d , IH, J = 2 Hz, Hgb), 4.24 ( d , IH, J = 3 Hz, Hga), 3.73 ( s , 3H, m e t h y l ) ppm. S p i n d e c o u p l i n g e x p e r i m e n t s : i r r a d i a t i o n o f Hj^  c o l l a p s e s Hg t o a d o u b l e t ( J = 3 Hz) and c o l l a p s e s Hg^ , t o a s i n g l e t ; i r r a d i a t i o n o f Hg c o l l a p s e s Hi t o a d o u b l e t ( J = 2 Hz) and c o l l a p s e s Hg^ t o a s i n g l e t . MS ( E I ) m/e: 316 (M+, 1 3 ) , 300 ( 8 ) , 152 ( 1 2 ) , 105 ( 1 0 0 ) , 77 ( 3 9 ) . E x a c t mass c a l c u l a t e d f o r C2iH2^603: 316.1100, f o u n d 316.1096. P h o t o s t a t i o n a r y S t a t e o f B e n z o s e m i b u l l v a l e n e s 43h and 43b C r y s t a l s o f 43h were d i s s o l v e d i n benzene and a c e t o n i t r i l e t o make up a p p r o x i m a t e l y 0.01 M s o l u t i o n s and a n a l y t i c a l l y p h o t o l y z e d (A > 290 nm). GC i n d i c a t e d a p h o t o s t a t i o n a r y s t a t e c o m p o s i t i o n o f 43h : 43b = 2 : 8. T h i s was v e r i f i e d by an in d e p e n d e n t p h o t o l y s i s o f compound 43b under i d e n t i c a l c o n d i t i o n s . Compound 43h r e a r r a n g e s t h e r m a l l y t o 43b i n t h e GC above 200 °C. P h o t o l y s i s o f B e n z o s e m i b u l l v a l e n e s 43d and 43e A 1 : 1 m i x t u r e o f compounds 43d and 43e was d i s s o l v e d i n benzene, a c e t o n e , and a c e t o n i t r i l e t o make up a p p r o x i m a t e l y 0.02 M s o l u t i o n s and a n a l y t i c a l l y p h o t o l y z e d (A > 290 nm). GC showed the f o r m a t i o n o f a new peak w i t h a maximum c o n v e r s i o n o f 4% r e l a t i v e t o the s t a r t i n g m a t e r i a l s . I n s u f f i c i e n t c o n v e r s i o n p r e v e n t e d i t s i s o l a t i o n o r i d e n t i f i c a t i o n . P h o t o l y s i s o f D e u t e r a t e d 43 (43-D) i n CDCI3 Compound 43-D (10 mg) d i s s o l v e d i n 1 ml o f CDCI3 was p h o t o l y z e d (A > 330 nm) t o complete c o n v e r s i o n . Compounds 43a-D and 43b-D were a n a l y z e d i n t h e r e a c t i o n m i x t u r e by NMR f o r the s i t e s o f d e u t e r a t i o n . The r e s u l t s f o r 43a-D a r e d e s c r i b e d . I H NMR (300 MHz, o n l y n o n - o v e r l a p p i n g s i g n a l s a r e r e p o r t e d ) 5: 5.90 (dd, l.OOH, J = 5,3 Hz, H^), 5.27 ( d , 0.89H, J = 5 Hz, H2), 4.69 ( d , 0.59H -1- 0.31D, J = 3 Hz, Hg^) . 3.57 ( s , 0.63H + 0.37D, Hgb), 3.43 ( s , 3.21H, m e t h y l ) ppm. The d a t a f o r 43b-D a r e r e p o r t e d below. •'-H NMR (300 MHz, o n l y n o n - o v e r l a p p i n g s i g n a l s a r e r e p o r t e d ) 5: 6.29 ( d , l.OOH, J = 3 Hz, Hg), 4.62 ( s , 0.72H + 0.28D, Hgb), 4.07 ( d , 0.78H + 0.22D, J = 8 Hz, Hgb), 3.71 ( s , 3.22H, m e t h y l ) ppm. P h o t o l y s i s o f D e u t e r a t e d 43 (43-D) i n t h e S o l i d S t a t e C r y s t a l s o f 43-D (54 mg, 0.17 mmole) were c r u s h e d between two p a i r s o f m i c r o s c o p e s l i d e s and p h o t o l y z e d (A > 290 nm). The r e s u l t i n g y e l l o w s o l i d was d i s s o l v e d i n 1 ml o f CDCI3 and a n a l y z e d by NMR. S p e c t r a l e x p a n s i o n and i n t e g r a t i o n o f the r e a c t i o n m i x t u r e was done. S i g n a l s o f compound 43f-D a r e r e p o r t e d below. •'-H NMR (300 MHz, CDCI3, o n l y n o n - o v e r l a p p i n g s i g n a l s a r e r e p o r t e d ) 6: 6.06 ( d , 0.68H + 0.32D, J = 5 Hz, H]_) , 5.40 (dd, l.OOH, J = 5,3 Hz, Hg), 4.07 ( d , 0.76H + 0.24D, J = 8 Hz, Hgb), 3.13 ( s , 2.88H, m e t h y l ) ppm. The m i x t u r e was chromatographed on s i l i c a u s i n g a 9 : 1 ( v / v ) m i x t u r e o f hexanes t o d i e t h y l e t h e r as the e l u t i n g s o l v e n t . T h i s gave t h r e e o v e r l a p p i n g bands; the f i r s t was 43f-D, the second was s t a r t i n g m a t e r i a l , and the t h i r d was 10 mg o f a 57 : 43 m i x t u r e o f compounds 43d-D and 43e-D. The t h i r d band was r e c h r o m a t o g r a p h e d as above and a n a l y z e d by NMR. S p e c t r a l d a t a f o r 43d-D a r e d e s c r i b e d . •'-H NMR (300 MHz, CDCI3, o n l y n o n - o v e r l a p p i n g bands a r e r e p o r t e d ) 6: 4.40 ( d , 0.67H + 0.33D, J = 6 Hz, Hgb), 3.45 ( s , 3.07H, m e t h y l ) , 3.40 (dd, 0.80H + 0.20D, J = 6,6 Hz, Hgb), 3.00 (dd, l.OOH, J = 6,6 Hz, Hga), 3.45 ( s , 3.12H, m e t h y l ) ppm. R e s u l t s f o r 43e-D a r e below. NMR (300 MHz, CDCI3, o n l y bands n o n - o v e r l a p p i n g w i t h 43d-D a r e r e p o r t e d ) 5: 4.35 ( d , 0.57H + 0.43D, J = 6 Hz, Hg^). 3.33 (dd, 0.71H + 0.29D, J = 6,6 Hz, H2b), 3.22-3.16 (m, 4.00H, H2a + m e t h y l ) ppm. The s o l v e n t was e v a p o r a t e d and r e d i s s o l v e d i n benzene-dg t o a n a l y z e t h e s i g n a l s o f H2a and H2b o f compound 43e-D a g a i n . ^H NMR (400 MHz, benzene-dg, o n l y s i g n a l s o f H2a and H2b a r e r e p o r t e d ) S : 2.86 (dd, 0.71H + 0.29D, J = 6,6 Hz, H2b), 2.80 (dd, l.OOH, J = 6,6 Hz, H2a) ppm. F. E t h y l 2 - B e n z o y l - l , 4 - d i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 3 - c a r b o x y l a t e (44) D i r e c t P h o t o l y s i s I n an a n a l y t i c a l s t u d y , c r y s t a l s o f 44 were d i s s o l v e d i n benzene and a c e t o n i t r i l e f o r p h o t o l y s i s (A > 290 nm). The r e a c t i o n s were m o n i t o r e d t o c o m p l e t e c o n v e r s i o n t o g i v e two major p h o t o p r o d u c t s and t h r e e m i n o r p h o t o p r o d u c t s i n d e p e n d e n t o f s o l v e n t . However, o v e r l a p p i n g peaks p r e v e n t e d p r o p e r GC i n t e g r a t i o n a t h i g h c o n v e r s i o n . I n an NMR s t u d y , compound 44 (app r o x . 10 mg) i n 1.5 ml o f CDCI3 were p h o t o l y z e d (A > 330 nm) t o c o m p l e t e c o n v e r s i o n t o g i v e f i v e p r o d u c t s 44a, 44b, 44c, 44d, 44e, and 44f i n a r a t i o o f 46 : 35 : 4 : 11 : 4 : t r a c e , r e s p e c t i v e l y . On a l a r g e r s c a l e , compound 44 (28 mg, 8.5 x 10"^ mole) was d i s s o l v e d i n 1.5 ml o f CDCI3 and p h o t o l y z e d (A > 330 nm) i n a p h o t o t u b e t o c o m p l ete c o n v e r s i o n . I n t e g r a t i o n o f t h e NMR e x p a n s i o n showed a 44a, 44b, 44c, 44d, 44e, and 4 4 f r a t i o o f 45 : 32 : 10 10: 3: t r a c e , r e s p e c t i v e l y . Chromatography on s i l i c a g e l w i t h d i e t h y l e t h e r and hexanes (1:9 v/v) as e l u e n t gave 8 mg o f a w h i t e s o l i d ( y i e l d 29%) i n t h e f i r s t band. R e c r y s t a l l i z a t i o n from hexanes gave p r i s m s o f e t h y l 2 a - b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 6 c -c a r b o x y l a t e ( 4 4 a ) . MP: 73-74 °C. IR (KBr) Un,ax: 1724 ( s , e s t e r C=0) , 1677 ( s , b e n z o y l C=0) , 1239 ( s , C-0) cm-1. ^H NMR ( 3 0 0 M H z ) 8: 8.05-7.15 (m, 9H, a r o m a t i c ) , 5.91 (dd, IH, J = 5,2 Hz, H^), 5.27 ( d , IH, J = 5 Hz, H5), 4.68 ( d , IH, J = 2 Hz, Hgb)- 4.57 ( s , IH, Hga), 3.88 ( q , 2H, J = 7 Hz, m e t h y l e n e ) , 0.96 ( t , 3H, J = 7 Hz, m e t h y l ) ppm. MS ( E I ) m/e: 330 (M+, 5 2 ) , 284 ( 8 ) , 257 ( 9 ) , 105 ( 1 0 0 ) , 77 ( 4 0 ) . E x a c t mass c a l c u l a t e d f o r C22H18O3: 330.1255, f o u n d 330.1255. A n a l , c a l c d . f o r C22H18O3: G, 79.98; H, 5.49. Found: C, 80.05; H, 5.46. The second band c o n t a i n e d 2.5 mg o f e t h y l 6 c - b e n z o y l - 2 b , 6 b -d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - l ( 2 a H ) - c a r b o x y l a t e (44b) as a c o l o r l e s s o i l ( y i e l d 9%). IR ( n e a t ) U n i a x ^ ^^09 ( s , e s t e r C=0) , 1666 ( s , b e n z o y l C=0) , 1248 ( s , C-0) c m ' l . ^H NMR (300 MHz) 8: 7.6-7.1 (m, 9H, a r o m a t i c ) , 6.29 ( d , IH, J = 3 Hz, Hg), 4.61 ( s , IH, Hgb), 4.25-4.10 (m, 2H, m e t h y l e n e ) , 4.06 (d , IH, J = 8 Hz, Hgb), 3.66 (dd, IH, J = 8,3 Hz, H2a), 1.30 ( t , 3H, J = 7 Hz, m e t h y l ) ppm. MS ( E I ) m/e: 330 (M+, 1 5 ) , 284 ( 4 0 ) , 257 ( 1 0 ) , 225 ( 4 0 ) , 180 ( 2 0 ) , 152 ( 5 0 ) , 105 ( 1 0 0 ) , 77 ( 6 0 ) . E x a c t mass c a l c u l a t e d f o r *-'22^ 18*-'3• 330.1255, f o u n d 330.1260. More compound 44b was s y n t h e s i z e d l a t e r f o r t h i s c h a r a c t e r i z a t i o n from t h e p h o t o l y s i s o f compound 44c. The t h i r d band was a 5 mg o f an i n s e p a r a b l e 1 : 7 : 2 m i x t u r e o f 44c, 44d, and 44e, from w h i c h t h e l a t t e r two were c h a r a c t e r i z e d . S p e c t r a l d a t a f o r e t h y l l - b e n z o y l - 2 a , 2 b , 6 b , 6 c - t e t r a h y d r o b e n z o [ a ] -c y c l o p r o p a [ c d ] p e n t a l e n e - 2 - c a r b o x y l a t e (44d) a r e as f o l l o w s : ^H NMR (300 MHz) 5: 7.6-7.0 (m, 9H, a r o m a t i c o v e r l a p p i n g w i t h 44c and 4 4 e ) , 4.40 ( d , IH, J = 6 Hz, Hgb), 3.90 (m, 2H, me t h y l e n e o v e r -l a p p i n g w i t h 4 4 e ) , 3.60 (ddd, IH, J = 6,6,6 Hz, Hg^ o v e r l a p p i n g w i t h 4 4 e ) , 3.41 (dd, IH, J - 6,6 Hz, H2b). 3.00 (dd, IH, J = 6,6 Hz, H2a), 0.85 ( t , 3H, J = 7 Hz, m e t h y l ) ppm. Peaks o f 44d were d i s t i n g u i s h a b l e f r o m t h o s e o f 44e by s t u d y i n g o t h e r m i x t u r e s w i t h d i f f e r e n t r a t i o s . GC-MS ( E l , DB-1) m/e: 330 (M+, 1 ) , 213 ( 8 ) , 180 ( 4 ) , 152 ( 2 0 ) , 105 ( 1 0 0 ) , 77 ( 2 0 ) . E x a c t mass c a l c u l a t e d f o r C22H18O3: 330.1256, f o u n d 330.1253. Data f o r e t h y l 2 - b e n z o y l - 2 a , 2 b , 6 b , 6 c - t e t r a h y d r o b e n z o [ a ] c y c l o -p r o p a [ c d ] p e n t a l e n e - l - c a r b o x y l a t e (44e) a r e below. ^H NMR (300 MHz) 6: 7.6-7.0 (m, 9H, a r o m a t i c o v e r l a p p i n g w i t h 44c and 44d) , 4.45 ( d , IH, J = 6 Hz, Hg^). 3.90 (m, 2H, met h y l e n e o v e r -l a p p i n g w i t h 44d) , 3.60 (ddd, IH, J = 6,6,6 Hz, Hg^, o v e r l a p p i n g w i t h 4 4 d ) , 3.33 (dd, IH, J = 6,6 Hz, H2b), 3.20 (dd, IH, J = 6,6 Hz, H2a), 0.66 ( t , 3H, J = 7 Hz, m e t h y l ) ppm. GC-MS ( E I , DB-1) m/e: 330 (M+, 2 ) , 213 ( 8 ) , 180 ( 4 ) , 152 ( 1 7 ) , 105 ( 1 0 0 ) , 77 ( 2 2 ) . E x a c t mass c a l c u l a t e d f o r C22H18O3: 330.1256, fo u n d 330.1259. Benzophenone-Sens i t i z e d P h o t o l y s i s I n an a n a l y t i c a l s t u d y , c r y s t a l s o f 44 and e x c e s s benzophenone were d i s s o l v e d i n benzene and p h o t o l y z e d (A > 330 nm). GC m o n i t o r i n g i n d i c a t e d c o m p lete c o n v e r s i o n t o 44a and 44c i n a s i n g l e i n s e p a r a b l e GC (DB-1) peak. However, a t column t e m p e r a t u r e s > 200 °C, compound 44c c o n v e r t s c o m p l e t e l y t o 44b. The r a t i o o f 44a t o 44c (44b) was 48 : 52 as e s t a b l i s h e d by GC (DB-17). On a p r e p a r a t i v e s c a l e , b e n z o b a r r e l e n e 44 (163 mg, 0.49 mmole) and 7 g (38 mmoles) o f benzophenone i n 140 ml o f benzene were p h o t o l y z e d (A > 330 nm) i n an i m m e r s i o n w e l l t o c o m p l e t e c o n v e r s i o n . The r e s u l t i n g s o l u t i o n was chromatographed on s i l i c a g e l w i t h hexanes and d i e t h y l e t h e r (9 : 1 v/v) as the e l u e n t . The f i r s t band was benzophenone. The second band was 58 mg o f p h o t o p r o d u c t 44a ( y i e l d 36%) , and the t h i r d band c o n t a i n e d 57 mg o f e t h y l 6 c - b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] -c y c l o p r o p a [ c d ] p e n t a l e n e - 2 a - c a r b o x y l a t e (44c) as a c o l o r l e s s o i l ( y i e l d 3 5 % ) . IR ( n e a t ) v^^^^: 1717 ( s , e s t e r C=0) , 1675 ( s , b e n z o y l C=0) , 1278 ( s , C-0) cm-1. % NMR (400 MHz) S : 7.9-7.1 (m, 9H, a r o m a t i c ) , 5.90 (dd, IH, J = 6,2 Hz, H^), 5.64 ( d , IH, J = 6 Hz, Hg) , 4.51 ( s , IH, Hgt,) , 4.29 ( d , IH, J = 2 Hz, Hg^). 4.12 ( q , 2H, J = 7 Hz, m e t h y l e n e ) , 1.12 ( t , 3H, J = 7 Hz, m e t h y l ) ppm. MS ( E I ) m/e: 330 (M+, 2 8 ) , 284 (65) 256 ( 3 0 ) , 226 ( 2 5 ) , 152 ( 4 9 ) , 105 ( 1 0 0 ) , 77 ( 6 0 ) . E x a c t mass c a l c u l a t e d f o r C22H18O3: 330.1255, f o u n d 330.1262. A s m a l l amount o f compounds 44d and 44e ( c a . 8 mg) were d e t e c t e d i n the t a i l o f the compound 44c band. S o l i d S t a t e P h o t o l y s i s o f Compound 44 C r y s t a l s o f 44 (9 mg, 2.7 x l O ' ^ mole) were p h o t o l y z e d (A > 290 nm) i n an NMR tube f o r two h o u r s and the u n m e l t e d , s l i g h t l y y e l l o w c r y s t a l s were d i s s o l v e d i n CDCI3 f o r NMR a n a l y s i s . The r a t i o o f the f o u r p r i m a r y p h o t o p r o d u c t s 44a, 44c, 44d, and 44e was 54 : 8 : 23 : 15 r e s p e c t i v e l y a t a c o n v e r s i o n o f 47%. The above e x p e r i m e n t was r e p e a t e d i n a 5 h p h o t o l y s i s and the 44a, 44c, 44d, and 44e r a t i o was 64 : 9 : 18 : 9, r e s p e c t i v e l y a t a 46% c o n v e r s i o n . P h o t o l y s i s o f B e n z o s e m i b u l l v a l e n e 44a On an a n a l y t i c a l s c a l e , s m a l l samples o f compound 44 were d i s s o l v e d i n benzene (A > 330 nm), a c e t o n i t r i l e (A > 330 nm), and a c e t o n e (A > 290 nm) f o r p h o t o l y s i s . GC m o n i t o r i n g i n d i c a t e d one v o l a t i l e p r o d u c t i n d e p e n d e n t o f s o l v e n t a t a maximum c o n v e r s i o n o f c a . 10%. Compound 44a (5 mg, 0.015 mmole) i n 1 ml o f CDCI3 was p h o t o l y z e d (A > 290 nm) and t h e e q u i l i b r i u m r a t i o was a n a l y z e d by NMR (GC) t o be 92 (92) : 8 (8) f o r 44a and 44f. The p r o d u c t , e t h y l 1-benzoyl-2b,6b-d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 6 c ( 2 a H ) - c a r b o x y l a t e ( 4 4 f ) was c h a r a c t e r i z e d as a m i x t u r e w i t h 44a as d e s c r i b e d below. NMR (400 MHz) S : 8.0-7.0 (m, 9H, o v e r l a p p i n g w i t h 4 4 a ) , 5.94 ( d , IH, J = 3 Hz, H2), 4.96 ( s , IH, Hgb), 4.20 ( q , 2H, J = 7 Hz, m e t h y l e n e ) , 3.97 ( d , IH, J = 8 Hz, H2b), 3.52 (dd, IH, J = 8,3 Hz, H2a), 1.30 ( t , 3H, J = 7 Hz, m e t h y l ) ppm. GC-MS ( E I , DB-1) m/e: 330 (M+, 1 1 ) , 256 ( 5 ) , 152 ( 1 2 ) , 105 ( 1 0 0 ) , 77 ( 2 5 ) . E x a c t mass c a l c u l a t e d f o r C22H18O3: 330.1255, f o u n d 330.1266. P h o t o s t a t i o n a r y S t a t e o f B e n z o s e m i b u l l v a l e n e s 44b and 44c On an a n a l y t i c a l s c a l e , s m a l l samples o f p h o t o p r o d u c t 44c were p h o t o l y z e d (A > 290 nm) i n benzene, a c e t o n i t r i l e , and a c e t o n e . The r e a c t i o n was m o n i t o r e d by GC t o show the f o r m a t i o n o f compound 44b, as t h e o n l y p r o d u c t , i n d e p e n d e n t o f s o l v e n t . The maximum c o n v e r s i o n was c a . 85%. Compound 44c (5 mg) was d i s s o l v e d i n CDCI3 and p h o t o l y z e d (A > 290 nm) t o e q u i l i b r i u m and a n a l y z e d by NMR (GC). T h i s i n d i c a t e d 83 (82) : 17 (18) c o m p o s i t i o n o f compounds 44b and 44c. Independent a n a l y t i c a l p h o t o l y s i s o f 44b gave the same r a t i o . G. Isopropyl 2-Benzoyl-l,4-dihydro-l,4-ethenonaphthalene-3-carboxylate (45) Direct Solution Photolysis of Compound 45 C r y s t a l s o f 45 were p h o t o l y z e d a n a l y t i c a l l y (A > 330 nm) i n benzene, a c e t o n i t r i l e , and methanol t o c o m p l e t e c o n v e r s i o n . GC m o n i t o r i n g showed two major p r o d u c t s and t h r e e minor p r o d u c t s , and the r e a c t i o n was i n d e p e n d e n t o f s o l v e n t . The GC (DB-1) r a t i o s were t y p i c a l l y 50 : 30 : 7 : 10 : 3 o f 45a, 45b, 45c, 45d + 45e, and 45f r e s p e c t i v e l y (use o f the DB-17 r e s u l t e d i n o t h e r o v e r l a p s ) . These a s s i g n m e n t s were v e r i f i e d l a t e r . On a l a r g e r s c a l e , c r y s t a l s o f 45f (20 mg, 5.8 x l O ' ^ mole) were d i s s o l v e d i n 1.5 ml o f CDCI3 and p h o t o l y z e d (A > 330 nm) t o complete c o n v e r s i o n . NMR a n a l y s i s showed a 45a : 45b : 45c : 45d : 45e r a t i o o f 50 : 30 : 8 : 8 : 4. The r e a c t i o n m i x t u r e was chromatographed on s i l i c a g e l e l u t i n g w i t h a 1 : 9 ( v / v ) m i x t u r e o f d i e t h y l e t h e r t o hexanes. The f i r s t band c o n s i s t e d o f 5 mg o f a w h i t e s o l i d ( y i e l d 26 % ) . R e c r y s t a l l i z a t i o n from hexanes gave c o l o r l e s s p r i s m s o f i s o p r o p y l 2 a - b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 6c -c a r b o x y l a t e (45a). MP: 78-79 °C. % NMR ( 3 0 0 M H z ) 5: 8.1-7.2 (ra, 9H. a r o m a t i c ) , 5.91 (dd, IH, J = 5,2 Hz, Hj^), 5.26 ( d , IH, J = 5 Hz, H2) , 4.75 ( s e p t e t , IH, J = 6 Hz, i s o p r o p y l m e t h i n e ) , 4.69 ( d , IH, J = 2 Hz, Hg^), 4.56 ( s , IH, H2b). 1-04 ( d , 3H, J = 6 Hz, m e t h y l ) , 0.65 ( d , 3H, J = 6 Hz, m e t h y l ) ppm. MS ( E I ) m/e: 344 (M+, 3 6 ) , 302 ( 6 ) , 258 ( 2 1 ) , 105 ( 1 0 0 ) , 77 ( 2 0 ) . E x a c t mass c a l c u l a t e d f o r C23H20O3: 344.1412, f o u n d 344.1408. A n a l . c a l c d . f o r C23H20O3: C, 80.21; H, 5.85. Found: C, 79.89 H, 5.75. The s e c o n d band was an i n s e p a r a b l e m i x t u r e o f 45b and 45c (6.5 mg) o v e r l a p p i n g w i t h t r a c e amounts o f 45d and 45e. T h i s was r e c h r o m a t o g r a p h e d as above t o remove 45d and 45e, g i v i n g 2 mg o f 45b and 45c. From t h i s m i x t u r e , i s o p r o p y l 6 c - b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o -[ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - l ( 2 a H ) - c a r b o x y l a t e (45b) was c h a r a c t e r i z e d as a 45b : 45c = 7 : 3 m i x t u r e . IR ( n e a t , 30% o f 45c) Uj^^x" 1705 ( s , e s t e r C=0) , 1666 ( s , b e n z o y l C=0), 1249 ( s , C-0) cm-1. I R NMR (300 MHz) 5: 7.7-7.1 (m, 9H, a r o m a t i c o v e r l a p p i n g w i t h 4 5 c ) , 6.28 ( d , IH, J = 3 Hz, H2), 5.04 ( s e p t e t , IH, J = 6 Hz, i s o p r o p y l m e t h i n e ) , 4.60 ( s , IH, Hg^,) > 4.04 ( d , IH, J = 8 Hz, H2b) , 3.66 (dd, IH, J = 8,3 Hz, H2a), 1-28 ( d , 3H, J = 6 Hz, m e t h y l ) , I . 23 ( d , 3H, J = 6 Hz, m e t h y l ) ppm. GC-MS (DB-1, DCI) m/e: 345 (M++1, 2 2 ) , 285 ( 1 0 0 ) , 105 ( 9 5 ) . E x a c t mass c a l c u l a t e d f o r C23H20O3: 344.1412, f o u n d 344.1408. B e n z o p h e n o n e - S e n s i t i z e d P h o t o l y s i s o f Compound 45 C r y s t a l s o f 45 (2 mg) and an a p p r o x i m a t e l y 1 0 - f o l d m o l a r e x c e s s o f benzophenone were d i s s o l v e d i n benzene and p h o t o l y z e d (A > 330 nm) t o c o m p lete c o n v e r s i o n . GC showed the f o r m a t i o n o f compounds 45a and 45c as the p h o t o p r o d u c t s . On a p r e p a r a t i v e s c a l e , compound 45 (57 mg, 1.5 x 10'"^ mole) and 1.0 g (5.5 mmoles) o f benzophenone were p h o t o l y z e d (A > 330 nm) i n 40 ml o f benzene t o complete c o n v e r s i o n . Chromatography on s i l i c a g e l u s i n g a 1 : 9 ( v / v ) m i x t u r e o f d i e t h y l e t h e r t o hexanes as e l u e n t gave f o u r bands. The f i r s t was benzophenone. The second c o n t a i n e d 25 mg o f compound 45a ( y i e l d 4 7 % ) . The t h i r d band c o n s i s t e d o f 20 mg o f i s o p r o p y l 6 c - b e n z o y l - 2 b , 6 b -d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 2 a - c a r b o x y l a t e (45c) as a c o l o r l e s s o i l ( y i e l d 3 7 % ) . IR ( n e a t ) U m a x ^ ^^18 ( s , e s t e r C=0), 1677 ( s , b e n z o y l C=0), 1283 ( s , C-0) cm-1. NMR (300 MHz) 6: 7.9-7.0 (m, 9H, a r o m a t i c ) , 5.90 (dd, IH, J = 5,2 Hz, H]_), 5.65 ( d , IH, J = 5 Hz, Hg) , 4.96 ( s e p t e t , IH, J = 6 Hz, i s o p r o p y l m e t h i n e ) , 4.46 ( s , IH, Hgb), 4.28 ( d , IH, J = 2 Hz, Hgb), 1-15 ( d , 3H, J = 6 Hz, m e t h y l ) , 1.01 (d , 3H, J = 6 Hz, m e t h y l ) ppm. MS ( E I ) m/e: 344 (M+, 3 ) , 284 ( 8 ) , 180 ( 1 2 ) , 152 ( 1 9 ) , 105 ( 1 0 0 ) , 77 ( 2 7 ) . E x a c t mass c a l c u l a t e d f o r C23H20O3: 344.1412, f o u n d 344.1406. The f o r t h band c o n t a i n e d 5 mg o f a 3 : 1 m i x t u r e o f p h o t o p r o d u c t s 45d and 45e; t h e s e two compounds were c h a r a c t e r i z e d i n t h e s o l i d s t a t e s t u d y . S o l i d S t a t e P h o t o l y s i s o f Compound 45 C r y s t a l s o f 45 i n an a n a l y t i c a l p h o t o t u b e were p h o t o l y z e d (A > 330 nm) u n t i l t he c r y s t a l s were y e l l o w b u t n o t m e l t e d . GC (DB-17) a n a l y s i s showed a 44 : 44 : 12 r a t i o o f 45d, 45e, and 45a a t a 27% c o n v e r s i o n . The p h o t o l y s i s was r e p e a t e d w i t h a P y r e x f i l t e r s l e e v e (A > 290 nm) u n t i l t h e c r y s t a l s s t a r t e d t o m e l t . GC (DB-17) showed a 73% c o n v e r s i o n t o a 40 : 40 : 20 r a t i o o f 45d, 45e, and 45a. On a p r e p a r a t i v e s c a l e , c r y s t a l s o f 45 (65 mg, 1.9 x 10'^ mole) were p h o t o l y z e d (A > 290 nm) f o r 4 h i n two NMR tub e s w i t h r o t a t i n g e v e r y 15 min. The u n m e l t e d y e l l o w c r y s t a l s were a n a l y z e d by NMR t o show a 32% c o n v e r s i o n and a 45d : 45e : 45a r a t i o o f 45 : 45 : 10. The r e a c t i o n m i x t u r e was chromatographed t w i c e on s i l i c a g e l e l u t i n g w i t h d i e t h y l e t h e r and hexanes (1 : 9 v / v ) . The r e s u l t i n g i n s e p a r a b l e m i x t u r e o f 45d and 45e (7.8 mg, y i e l d 12%) were c h a r a c t e r i z e d t o g e t h e r . Data f o r i s o p r o p y l 1-benzoyl-2a,2b,6b,6c-t e t r a h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 2 - c a r b o x y l a t e (45d) i s d e s c r i b e d . IR ( n e a t , 50:50 mix w i t h 45e) % a x = 1^07 ( s , e s t e r C=0), 1672 ( s , b e n z o y l C=0), 1270 ( s , C-0) c m " l . I R NMR (300 MHz) S : 7.6-6.7 (m, 9H, a r o m a t i c o v e r l a p p i n g w i t h 4 5 e ) , 4.78 ( s e p t e t , IR, J = 6 Hz, i s o p r o p y l m ethine o v e r l a p p i n g w i t h 4 5 e ) , 4.41 ( d , IR, J = 7 Hz, Hgb)> 3.61 (ddd, IH, J = 7,7,7 Hz, Hg^ o v e r l a p p i n g w i t h 4 3 ) , 3.40 (dd, IR, J = 7,7 Hz, H2b), 3.00 (dd, IR, J = 7,7 Hz, H2a), 1-01 ( d , 3R, J = 6 Hz, m e t h y l ) , 0.66 ( d , 3H, J = 6 Hz, m e t h y l ) ppm. GC-MS (DB-17, DCI i s o b u t a n e ) m/e: 345 (M+ + 1, 100), 285 ( 3 5 ) . E x a c t mass ( E I ) c a l c u l a t e d f o r C23H20O3: 344.1412, f o u n d 344.1405. C h a r a c t e r i z a t i o n o f i s o p r o p y l 2 - b e n z o y l - 2 a , 2 b , 6 b , 6 c - t e t r a -h ydrobenzo [ a] c y c l o p r o p a [ c d ] p e n t a l e n e - 1 - c a r b o x y l a t e (45e) i s g i v e n below. IR ( n e a t , 50:50 mix w i t h 45d) u^^^^: see above. NMR (300 MHz) S : 7.6-6.7 (m, 9H, a r o m a t i c ) , 4.62 ( s e p t e t , IH, J = 6 Hz, i s o p r o p y l methine o v e r l a p p i n g w i t h 4 5 d ) , 4.33 ( d , IH, J = 7 Hz, Hgb). 3.58 (ddd, IH, J = 7,7,7 Hz, Hg^ o v e r l a p p i n g w i t h 4 5 d ) , 3.31 (dd, IH, J = 7,7 Hz, H2b). 3.20 (dd, IH, J = 7,7 Hz, H2a), 0.88 ( d , 3H, J = 6 Hz, m e t h y l ) , 0.44 ( d , 3H, J = 6 Hz, m e t h y l ) ppm. GC-MS (DB-17, DCI i s o b u t a n e ) m/e: 345 (M+ -l- 1, 100), 285 ( 5 2 ) . E x a c t mass ( E I ) c a l c u l a t e d f o r C23H20O3: 344.1412, f o u n d 344.1418. P h o t o l y s i s o f B e n z o s e m i b u l l v a l e n e 45a S m a l l amounts o f compound 45a were d i s s o l v e d i n benzene, a c e t o n i t r i l e , and a c e t o n e . P h o t o l y s i s (A > 290 nm) showed a s o l v e n t - i n d e p e n d e n t r e a c t i o n t o form one p r o d u c t ( 4 5 f ) a t a 13% maximum c o n v e r s i o n by GC. On a l a r g e r s c a l e , 10 mg o f 45a were d i s s o l v e d i n 1 ml o f CDCI3 and p h o t o l y z e d (A > 290 nm) t o e q u i l i b r i u m . The m i x t u r e was a n a l y z e d by NMR (GC) t o g i v e a 45a t o 45f r a t i o o f 88 (91) : 12 ( 9 ) . I s o p r o p y l 1 - b e n z o y l - 2 b , 6 b - d i h y d r o b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e -6 c ( 2 a H ) - c a r b o x y l a t e ( 4 5 f ) was c h a r a c t e r i z e d i n t h i s m i x t u r e . ^H NMR (300 MHz) 5: 7.9-7.1 (m, 9H, a r o m a t i c ) , 5.94 ( d , IH, J = 3 Hz, H2), 5.06 ( s e p t e t , IH, J = 6 Hz, i s o p r o p y l m e t h i n e ) , 4.94 ( s , IH, Hgb), 3.95 ( d , IH, J = 8 Hz, H2b), 3.50 (dd, IH, J = 8,3 Hz, H2a) ppm. M e t h y l s o f t h e i s o p r o p y l a r e h i d d e n b e n e a t h 45a. GC-MS (DB-1, E I ) m/e: 344 (M+, 8 ) , 302 ( 8 ) , 284 ( 8 ) , 257 ( 1 0 ) , 152 ( 1 3 ) , 105 ( 1 0 0 ) , 77 ( 1 9 ) . E x a c t mass c a l c u l a t e d f o r C23H20O3: 344.1412, f o u n d 344.1400. P h o t o l y s i s o f B e n z o s e m i b u l l v a l e n e 45c On an a n a l y t i c a l s c a l e , compound 45c was d i s s o l v e d i n benzene, a c e t o n i t r i l e , and a c e t o n e . The s o l u t i o n s were p h o t o l y z e d (A > 290 nm) t o g i v e one p r o d u c t ( 4 5 b ) , i n d e p e n d e n t o f s o l v e n t , a t an e q u i l i b r i u m c o n v e r s i o n o f 87%. I t was a l s o n o t i c e d t h a t compound 45c r e a r r a n g e s t o 45b i n the gas chromatography column (DB-17) a t t e m p e r a t u r e s above 220 °C. H. 1 , 4 - D i h y d r o - l , 4 - e t h e n o n a p h t h a l e n e - 2 , 3 - d i c a r b o x y l a t e S a l t s D i r e c t S o l u t i o n P h o t o l y s i s o f S a l t s 48-54 A s t a n d a r d p r o c e d u r e f o r a n a l y t i c a l p h o t o l y s i s o f the p r e p a r e d s a l t s (48-54) was adopted. The s a l t (5 - 10 mg) was d i s s o l v e d w i t h a s u i t a b l e d e u t e r a t e d s o l v e n t (1 ml) i n a 10 ml P y r e x p h o t o t u b e . The sample was degassed by r e p e a t i n g t h e freeze-pump-thaw c y c l e t w i c e . The r a t i o s o f p h o t o p r o d u c t s ( d e t e r m i n e d by NMR) were r e p o r t e d i n t h e t e x t . On a p r e p a r a t i v e s c a l e , the s t a n d a r d p r o c e d u r e f o r s a l t s 48-54 was t o d i s s o l v e 10 - 30 mg o f the s a l t i n a s u i t a b l e d e u t e r a t e d s o l v e n t (3 ml) i n a 10 ml P y r e x p h o t o t u b e . The d e g a s s e d sample was p h o t o l y z e d and t h e r e s u l t i n g m i x t u r e a n a l y z e d d i r e c t l y by NMR. The r a t i o s were r e p o r t e d i n the t e x t . The m i x t u r e was t h e n d i l u t e d w i t h d i e t h y l e t h e r , a c i d i f i e d w i t h H C l (aq)> washed w i t h w a t e r , d r i e d o v e r MgSO^, f i l t e r e d , e v a p o r a t e d , and r e d i s s o l v e d i n CDCI3. The r e s u l t i n g m i x t u r e o f r e p o r t e d d i a c i d s was a n a l y z e d by NMR (400 MHz) and t h e s i g n a l s c o r r e l a t e d t o c o n f i r m our a s s i g n m e n t s . S o l i d S t a t e P h o t o l y s i s o f S a l t s 48-54 C r y s t a l s o r powders ( a p p r o x . 10 mg) o f s a l t s 48-54 were p l a c e d i n a n i t r o g e n - f i l l e d NMR tube and p h o t o l y z e d . A f t e r i r r a d i a t i o n t h e sample was d i s s o l v e d i n a s u i t a b l e s o l v e n t and a n a l y z e d by NMR. The p r o d u c t r a t i o s and r e s u l t a n t sample appearances were t a b u l a t e d i n the t e x t . F o r each s a l t , t he same p r o c e d u r e was r e p e a t e d u s i n g s e v e r a l d i f f e r e n t p h o t o l y s i s t i m e s . I . D ime t h y 1 1,4-D ime thy1-1,4,5,8-1 e trame thy1-1,4-e thenonaphtha1ene-2,3-d i c a r b o x y l a t e (47) D i r e c t S o l u t i o n P h o t o l y s i s o f Compound 47 On an a n a l y t i c a l s c a l e , c r y s t a l s o f compound 47 were p h o t o l y z e d (A > 290 nm) i n benzene and a c e t o n i t r i l e . GC m o n i t o r i n g showed the f o r m a t i o n o f two p r o d u c t s , 47b and 47a, i n d e p e n d e n t o f s o l v e n t a t an a p p r o x i m a t e 1 : 1 r a t i o . A t h i g h e r c o n v e r s i o n s t h e r a t i o changed; 47b s t a r t e d t o d i m i n i s h and the f o r m a t i o n o f a s e c o n d a r y p h o t o p r o d u c t was seen ( 4 7 c ) . I n an NMR s t u d y , c r y s t a l s o f 47 d i s s o l v e d i n 1.5 ml CDCI3 were p h o t o l y z e d (A > 290 nm) f o r 30 min. The m i x t u r e was a n a l y z e d by NMR (GC) t o a 47b : 47a r a t i o o f 43 (41) : 57 (59) a t 9% c o n v e r s i o n . A p r e p a r a t i v e r e a c t i o n was p e r f o r m e d w i t h 250 mg (0.77 mmole) o f compound 47 i n f i v e 10 ml p h o t o t u b e s , u s i n g benzene as s o l v e n t , and p h o t o l y z e d (A > 290 nm) t o 95% c o n v e r s i o n . Chromatography o f t h e m i x t u r e on s i l i c a g e l u s i n g a d i e t h y l e t h e r and hexanes (1 : 9 v/v) s o l v e n t s y s t e m gave t h r e e bands. The f i r s t band c o n t a i n e d 23 mg o f d i m e t h y l 2a,6c - d i h y d r o - 1 , 2 a , 3 , 6 - t e t r a m e t h y l b e n z o [ a ] c y c l o p r o p a [ c d ] -p e n t a l e n e - 2 b , 6 b - d i c a r b o x y l a t e (47c) as a w h i t e s o l i d ( y i e l d 9%). R e c r y s t a l l i z a t i o n from hexanes gave c o l o r l e s s p r i s m s . MP: 94-98 °C. IR (KBr) v^^^: 1730 ( v s , C=0), 1274 ( s , C-0), 1244 ( s ) cm"!. I R NMR (400 MHz) 6: 6.95 (AB q u a r t e t , 2H, J = 14,8 Hz, a r o m a t i c ) , 5.08 ( s , IH, H2), 3.82 ( s , 3H, e s t e r m e t h y l ) , 3.78 ( s , 3H, e s t e r m e t h y l ) , 3.36 ( s , IH, Hg^)> 2.21 ( s , 3H, a r o m a t i c m e t h y l ) , 2.19 ( s , 3H, a r o m a t i c m e t h y l ) , 1.78 ( s , 3H, m e t h y l on C^), 1.25 ( s , 3H, m e t h y l on C2a) ppm. The above a s s i g n m e n t s were s u p p o r t e d by NOE s t u d i e s . l ^ c NMR (50 MHz) 5: 171.0 (C=0), 170.5 (C=0), 148.3 ( C ) , 147.1 ( C ) , 134.5 ( C ) , 133.9 ( C ) , 129.4 (CH), 129.3 (CH), 128.2 (CH), 120.3 (CH), 73.5 ( C ) , 65.1 ( C ) , 53.0 ( C ) , 52.1 (CH3), 51.7 (CH3), 47.4 (CH3), 19.4 (CH3), 19.2 (CH3), 13.8 (CH3), 12.0 (CH3) ppm. The a s s i g n m e n t s were b a s e d upon an APT. MS ( E I ) m/e: 326 (M+, 5 5 ) , 294 ( 7 4 ) , 267 ( 6 3 ) , 235 ( 4 1 ) , 207 ( 1 0 0 ) . E x a c t mass c a l c u l a t e d f o r C20H22O4: 326.1518, f o u n d 326.1512. A n a l , c a l c d . f o r C20H22O4: C, 73.60; H,6.79. Found: C, 73.50; H, 6.76. The second band was 58 mg o f d i m e t h y l 1 , 4 , 6 , 9 - t e t r a m e t h y l b e n z o -c y c l o o c t e n e - 5 , 1 0 - d i c a r b o x y l a t e (47b) as a w h i t e s o l i d ( y i e l d 2 3 % ) . R e c r y s t a l l i z a t i o n from methanol gave c o l o r l e s s r o d s . MP: 204-207 °C. IR (KBr) U m a ^ : 1711 ( s , C=0), 1620 (m), 1239 ( s , C-0) cm'^. NMR (400 MHz) 5: 6.98 ( s , 2H, a r o m a t i c ) , 5.88 ( s , 2H, v i n y l ) , 3.65 ( s , 6H, e s t e r m e t h y l s ) , 2.21 ( s , 6H, a r o m a t i c m e t h y l s ) , 2.06 ( s , 6H, v i n y l m e t h y l s ) ppm. These a s s i g n m e n t s were s u p p o r t e d by NOE s t u d i e s . NMR (100 MHz) 6: 167.4 (2 x C=0) , 148.5 (2 x C) , 138.4 (2 X C ) , 133.1 (2 X C ) , 133.0 (2 x CH), 129.7 (2 x C ) , 128.5 (2 x CH), 51.6 (2 x e s t e r CH3), 19.7 (2 x CH3), 19.6 (2 x CH3) ppm. The above a s s i g n m e n t s were b a s e d on an APT. MS ( E I ) m/e: 326 (M+, 3 5 ) , 294 ( 8 0 ) , 267 ( 6 4 ) , 235 ( 4 3 ) , 207 (1 0 0 ) . E x a c t mass c a l c u l a t e d f o r C20H22O4: 326.1518, f o u n d 326.1518. A n a l . c a l c d . f o r C20H22O4: 0, 73.60; H, 6.79. Found: C, 73.70; H, 6.72. The s t r u c t u r e o f t h i s compound was c o n f i r m e d by an X - r a y d i f f r a c t i o n a n a l y s i s . The c r y s t a l d a t a a r e as f o l l o w s : C20H22O4, o r t h o r h o m b i c , space group Pbca, a = 17.716(2)Â, b = 15.298(2)Â, c = 13.210(3)Â, V = 3580(2)Â3, Z = 8, D^ ^ = 1.211 g/ml, R = 0.046. The t h i r d band was d i m e t h y l 2 a , 2 b - d i h y d r o - 1 , 2 b , 3 , 6 - t e t r a m e t h y l -b e n z o [ a ] c y c l o p r o p a [ c d ] p e n t a l e n e - 6 b , 6 c - d i c a r b o x y l a t e (47a) mix e d w i t h some u n r e a c t e d s t a r t i n g m a t e r i a l ( 4 7 ) . The m i x t u r e was r e p h o t o l y z e d and chromatographed as above t o g i v e 33 mg o f 47a as a w h i t e s o l i d ( y i e l d 1 3 % ) . R e c r y s t a l l i z a t i o n from hexanes gave c o l o r l e s s p r i s m s . MP: 104-105 °C. IR (KBr) v^^^: 1734 ( s , C=0), 1435 (m), 1 2 7 2 ( s , C-0) cm-1. I R NMR ( 4 0 0 MRz) S : 6.92 ( s , 2H, a r o m a t i c ) , 5.04 ( d , IR, J - 2 Hz, H2), 3.83 ( s , 3H, e s t e r m e t h y l ) , 3.67 ( s , 3H, e s t e r m e t h y l ) , 3.04 ( d , IH, J = 2 Hz, H2a), 2.41 ( s , 3H, a r o m a t i c m e t h y l ) , 2.25 ( s , 3H, a r o m a t i c m e t h y l ) , 1.94 ( s , 3R, m e t h y l ) , 1.81 ( s , 3H, m e t h y l ) ppm. The above a s s i g n m e n t s were s u p p o r t e d by NOE s t u d i e s . l^c NMR ( 1 0 0 MHz) 5: 171.1 (C=0), 169.5 (C=0), 146.7 ( C ) , 145.9 ( C ) , 137.0 ( C ) , 132.9 ( C ) , 130.4 (CH), 129.4 (CH), 128.3 (CH), 120.0 (CH), 70.0 ( C ) , 68.3 ( C ) , 53.0 ( C ) , 51.9 ( e s t e r CH3), 51.0 ( e s t e r CR3), 20.7 (CH3), 19.8 (CH3), 17.3 (CR3), 13.9 (CH3) ppm. These a s s i g n m e n t s were b a s e d on an APT e x p e r i m e n t . MS ( E I ) m/e 326 (M+, 3 5 ) , 294 ( 2 7 ) , 266 ( 1 0 0 ) , 2 07 ( 8 4 ) . E x a c t mass c a l c u l a t e d f o r C20H22O4: 326.1518, f o u n d 3 2 6 . 1 5 2 7 . A n a l , c a l c d . f o r C20H22O4: C, 79.60; R, 6.79. Found: C, 73.80; H, 6.86. The s t r u c t u r e o f t h i s compound was c o n f i r m e d by an X - r a y d i f f r a c t i o n a n a l y s i s . The d a t a a r e as f o l l o w s : C2oH2204> o r t h o r h o m b i c , space group P c a 2 i , a = 7.325(9)Â, b = 14.781(1)Â, c = 15.535(1)Â, V = 1681.9(5)Â3, Z = 4, D^ ^ = 1.289 g/ml, R = 0.045. D e t a i l s w i l l be p u b l i s h e d e l s e w h e r e . B e n z o p h e n o n e - S e n s i t i z e d P h o t o l y s i s I n an a n a l y t i c a l s t u d y , compound 47 was d i s s o l v e d w i t h an a p p r o x i m a t e l y 2 - f o l d w/w e x c e s s o f benzophenone i n benzene and p h o t o l y z e d (A > 330 nm) t o complete c o n v e r s i o n . GC m o n i t o r i n g showed two p r o d u c t s , 47a and 47d, a t a 32 : 68 r a t i o . On a l a r g e r s c a l e , c r y s t a l s o f 47 (80 mg, 0.25 mmole) and benzophenone (200 mg) i n 8 ml o f benzene were p h o t o l y z e d (A > 330 nm) to 92% c o n v e r s i o n t o 47a and 47d i n a 40 : 60 r a t i o . Chromatography on s i l i c a g e l u s i n g d i e t h y l e t h e r and hexanes (1 : 19 v/v) as the e l u e n t s e p a r a t e d benzophenone from 47a and 47d. The two p h o t o p r o d u c t s c o u l d n o t be s e p a r a t e d and t h e r e f o r e 47d c o u l d n o t be i d e n t i f i e d . From t h e m i x t u r e , t he f o l l o w i n g GC-MS d a t a c o u l d be o b t a i n e d : GC-MS (DB-1, E I ) m/e: 326 (M+, 1 2 ) , 266 ( 1 0 0 ) , 235 ( 1 4 ) , 207 ( 8 0 ) , 193 ( 2 9 ) . When l e f t t o s t a n d , i t was n o t i c e d t h a t 47d r e a d i l y c o n v e r t e d t o o t h e r i n s e p a r a b l e p r o d u c t s . S o l i d S t a t e P h o t o l y s i s o f Compound 47 C r y s t a l s o f 47 (8 mg) were p h o t o l y z e d (A > 290 nm) i n an NMR tube f o r 15 h. The c r y s t a l s r e m a i n e d c o l o r l e s s b u t were s l i g h t l y s t i c k y on t h e s u r f a c e . NMR a n a l y s i s showed the f o r m a t i o n o f one major p h o t o p r o d u c t (47a). The r a t i o o f 47 : 47a : 47b was 89 : 10 : 1. The p h o t o l y s i s was r e p e a t e d f o r 45 h and the c o l o r l e s s , s l i g h t l y s t i c k y c r y s t a l s had a 47 : 47a : 47b r a t i o o f 79 : 20 : 1. C r y s t a l s o f 47 were p h o t o l y z e d (A > 330 nm) f o r 4 days t o g i v e by NMR a 47 : 47a : 47b r a t i o o f 94 : 6 : t r a c e . C r y s t a l s were a l s o p h o t o l y z e d w i t h a n i t r o g e n l a s e r (A = 337 nm) f o r 5 h. NMR a n a l y s i s o f the u n m e l t e d c o l o r l e s s c r y s t a l s i n CDCI3 showed a 47, 47a, and 47b r a t i o o f 76 : 23 : 1. P h o t o l y s i s o f C y c l o o c t a t e t r a e n e 47b On an a n a l y t i c a l s c a l e , c r y s t a l s o f 47b (5 mg) were d i s s o l v e d i n benzene and a c e t o n e . P h o t o l y s i s (A > 290 nm) w i t h GC m o n i t o r i n g showed t h e f o r m a t i o n o f compound 47c. The a c e t o n e r e a c t i o n was much f a s t e r t h a n t h e benzene r e a c t i o n . I I I . QUANTUM YIELD STUDIES A p p a r a t u s A merry-go-round apparatus-'-23 ^^s u s e d i n a l a r g e w a t e r b a t h t o m a i n t a i n an even p h o t o l y s i s a t a c o n s t a n t t e m p e r a t u r e (20 + 3 °C). The 450 W H a n o v i a medium p r e s s u r e m e r c u r y lamp was u s e d as t h e l i g h t s o u r c e . The 313 nm l i n e from the lamp was i s o l a t e d by a f i l t e r c o m b i n a t i o n o f a 7-54 C o r n i n g g l a s s p l a t e ^ ^ S ^nd an aqueous s o l u t i o n o f 0.002 M K2Cr04 c o n t a i n i n g 5% K2CO3 (wt/wt) c i r c u l a t e d t h r o u g h a P y r e x c o o l i n g j a c k e t . P u r i f i c a t i o n o f S o l v e n t s and Reagents Benzene was u s e d as t h e s o l v e n t u n l e s s o t h e r w i s e s p e c i f i e d . Benzene was made t h i o p h e n e - f r e e by s u c c e s s i v e washes w i t h c o n c e n t r a t e d s u l f u r i c a c i d f o l l o w e d by d i s t i l l a t i o n o v e r sodium metal.122 V a l e r o p h e n o n e , u s e d as t h e a c t i n o m e t e r , was c h e c k e d f o r acetophenone p r i o r t o use (< 0.3% by GC). The s t a r t i n g m a t e r i a l s and t h e i r p h o t o p r o d u c t s were p u r i f i e d by chromatography and r e c r y s t a l l i z a t i o n . The a l k a n e i n t e r n a l s t a n d a r d s ( f r o m A l d r i c h ) were u s e d w i t h no f u r t h e r p u r i f i c a t i o n . I n t e r n a l S t a n d a r d s and GC D e t e c t o r (FID) Responses Each a l k a n e i n t e r n a l s t a n d a r d chosen was su c h t h a t i t s GC s i g n a l was c l o s e b u t d i d n o t o v e r l a p w i t h the s t a r t i n g m a t e r i a l o r i t s p h o t o p r o d u c t s . T e t r a d e c a n e (n-Cii^ti^Q) was the i n t e r n a l s t a n d a r d f o r the v a l e r o p h e n o n e a c t i n o m e t r y . T e t r a c o s a n e (n-C24H5Q) was the i n t e r n a l s t a n d a r d f o r the p h o t o p r o d u c t s o f s t a r t i n g m a t e r i a l s 42, 43, and 47. T r i c o s a n e (n-C23H4g) was the i n t e r n a l s t a n d a r d f o r t h e p h o t o p r o d u c t s o f 45, and o c t a c o s a n e (n-C28H58) i n t e r n a l l y s t a n d a r d i z e d t h e s t u d y o f s t a r t i n g m a t e r i a l 44. D e t e c t o r r e s p o n s e s were measured from s e v e r a l i n j e c t i o n s (n > 3) o f an a c c u r a t e l y weighed m i x t u r e o f p h o t o p r o d u c t and i n t e r n a l s t a n d a r d . A c t i n o m e t r y V a l e r o p h e n o n e a c t i n o m e t r y was used. The quantum y i e l d o f acetophenone from v a l e r o p h e n o n e has been e s t a b l i s h e d t o be $ = 0.3 w i t h an opaque c o n c e n t r a t i o n (0.1 M) o f v a l e r o p h e n o n e i n benzene. •'-^ ^ The e x c i t a t i o n w a v e l e n g t h was the mercury 313 nm l i n e . Two 3 ml benzene s o l u t i o n s o f 0.1 M v a l e r o p h e n o n e and 1 g/ml o f t e t r a d e c a n e were degassed by r e p e a t i n g the freeze-pump-thaw c y c l e t w i c e under n i t r o g e n . These s o l u t i o n s , i n 10 ml P y r e x p h o t o t u b e s , were p l a c e d a l o n g s i d e t h e t e s t samples i n the merry-go-round a p p a r a t u s and m o n i t o r e d by GC (carbowax column, 15 m, average o f two i n j e c t i o n s ) . I r r a d i a t i o n s Two 3 ml t e s t samples were p r e p a r e d f o r each s t a r t i n g m a t e r i a l . An opaque c o n c e n t r a t i o n a t 313 nm, d e t e r m i n e d by UV s t u d i e s , was p r e p a r e d . I n t e r n a l s t a n d a r d s were added and t h e i r c o n c e n t r a t i o n i n the t e s t samples was a p p r o x i m a t e l y 5% o f the s t a r t i n g m a t e r i a l . The samples were p h o t o l y z e d a l o n g s i d e the a c t i n o m e t e r s o l u t i o n s and m o n i t o r e d by GC (DB-1, 15 m, two i n j e c t i o n s p e r sample p o i n t ) t o no more t h a n 10% p h o t o p r o d u c t f o r m a t i o n . C a l c u l a t i o n o f Quantum Y i e l d s A f t e r c o r r e c t i n g f o r t h e v a r i o u s r e s p o n s e s , t h e quantum y i e l d s were c a l c u l a t e d from the f o l l o w i n g e q u a t i o n : ^ ' $ = # moles p h o t o p r o d u c t / # moles photons a b s o r b e d The quantum y i e l d o f each p h o t o p r o d u c t was c a l c u l a t e d a t d i f f e r e n t c o n v e r s i o n s and graphed ( i n t e x t ) . The s t r a i g h t l i n e was e x t r a p o l a t e d t o z e r o c o n v e r s i o n t o d e t e r m i n e t h e r e p o r t e d v a l u e . These v a l u e s were d e t e r m i n e d by l i n e a r l e a s t s q u a r e s c a l c u l a t i o n s p e r f o r m e d on one o f B. C l i f f o r d ' s u n d e r g r a d u a t e l a b o r a t o r y computers. The e r r o r l i m i t s a r e r e p o r t e d as s t a n d a r d d e v i a t i o n s , i n p a r e n t h e s e s . REFERENCES 1. R o t h , H.D. Angrew. Chem. Ed. 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The numbers i n p a r e n t h e s e s a r e s t a n d a r d d e v i a t i o n s o f the l e a s t s i g n i f i c a n t f i g u r e . 96. Flemming, I . " F r o n t i e r O r b i t a l s and O r g a n i c C h e m i c a l R e a c t i o n s " , W i l e y , New Yo r k , 1980, p 201. 97. G r i f f i n , G.W.; Padwa, A. " P h o t o c h e m i s t r y o f H e t e r o c y c l i c Compounds", ed. B u c h a r t , 0.; W i l e y , New Yo r k , 1976, p 41. 98. a) Dauben, W.G.; Shaffer, G.W.; Deving, E.J. J. Am. Chem. Soc. 1 9 7 0 , 92, 6273. b) Hess, L.D.; Jacobson, J.L.; Schaffner, K.; Pitts, J.N. J. Am. Chem. Soc. 1 9 6 4 , 89/ 3684. 99. Garcia-Garibay, M.; Scheffer, J.R.; Watson, D.G. J. Org. Chem. 1 9 9 2 , 57, 241. 100. Lowry, T.H. and Richardson, K.S. "Mechanism and Theory in Organic Chemistry", 3rd ed.. Harper & Row Pub., New York, 1 9 8 7 , p 767. 101. For examples see: a) Reddy, G.D.; Jayasree, B. ; Ramamurthy, V. J. Org. 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