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Synthesis and medium-dependent photochemistry of tetrahydro-1,4- Anthraquinones and Anthraquinols : structure-reactivity… Askari, Syed Hasan 1987

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SYNTHESIS AND MEDIUM-DEPENDENT PHOTOCHEMISTRY OF TETRAHYDRO-1,4-ANTHRAQUINONES AND ANTHRAQUINOLS: STRUCTURE-REACTIVITY RELATIONSHIPS FROM X-RAY CRYSTALLOGRAPHY by SYED HASAN ASKARI B.Sc, A l i g a r h Muslim University, India, 1976 M.Sc, A l i g a r h Muslim Uni v e r s i t y , India, 1978 M.Sc, Un i v e r s i t y of Manchester I n s t i t u t e of Science and Technology, England, 1981 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 accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA February 1987 © Syed Hasan Askari, 1987 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 The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 DE-6(3/81) i i i ABSTRACT Previous work from our laboratory has been concerned with i n v e s t i -gating the photochemical r e a c t i v i t y of tetrahydro-1,4-naphthalenedione and tetrahydronaphthoquinol systems, both i n the' s o l i d state and i n so l u t i o n . The f a s c i n a t i n g r e s u l t s obtained prompted us to extend the studies to the analogous tetrahydro-1,4-anthracenediones, tetrahydro-5,12-naphthacenediones and tetrahydroanthraquinol systems. Tetrahydro-1,4-anthracenedione i s expected to undergo b i s - e n o l i z a t i o n with extreme ease, and therefore i t s preparation requires mild and neutral condi-tion s . These compounds were prepared by Diels-Alder r e a c t i o n between o-quinodimethane and p-benzoquinone and other p-substituted quinones. o-Quinodimethane was generated i n s i t u by sulphur dioxide extrusion from 3,6-dihydrobenzo[b]oxathiin-2-oxide. The photochemistry of the tetrahydro-1,4-anthracenediones, t e t r a -hydro-5,12-naphthalenedione and tetrahydroanthraquinols has been inves t i g a t e d both i n the s o l i d state and s o l u t i o n . The e f f e c t of the s o l i d state medium on the photoreactivity, compared to the s o l u t i o n , i s s i g n i f i c a n t ; the nature and/or the number of the photoproducts formed i n the s o l i d state i s generally d i f f e r e n t from the r e s u l t s obtained i n s o l u t i o n . These differences have been explained on the basis of the c r y s t a l and molecular structures of the reactants. Special s t e r i c e f f e c t s , which may impede the photochemical reactions i n the s o l i d state have been i d e n t i f i e d . The values of the geometric parameters (d, r and A ) for hydrogen atom abstraction are found to be s i m i l a r to those i v observed i n e a r l i e r studies by Scheffer et a l . I t has been found that the o-quinodimethane/2,3-dimethyl-l,4-naphthoquinone adduct affords, v i a /3-hydrogen atom abstrac t i o n and closure of the r e s u l t i n g 1,3-biradical, a cyclopropanol. The cyclopro-panol i t s e l f undergoes photolysis i n i t i a t e d by a novel r i n g opening process. I r r a d i a t i o n of c r y s t a l s of the adduct does not r e s u l t i n any cyclopropanol. The reasons for the n o n - r e a c t i v i t y of the Diels-Alder adduct i n the s o l i d state have been suggested to be due to the non-bonded s t e r i c i n t e r a c t i o n s between the l a t t i c e neighbors as shown by the X-ray c r y s t a l structure. The photorearrangement of one substrate, namely 2,3,4a,9a-tetra-methyl-4a,9a,9,10-tetrahydro-1,4-anthracenedione i s found to be con-t r o l l e d by the temperature, m u l t i p l i c i t y , and phase of the reaction. By carr y i n g out the re a c t i o n at or above room temperature or i n the pres-ence of a s e n s i t i z e r or i n the c r y s t a l l i n e state, the re a c t i o n can be forced i n one d i r e c t i o n . Lowering the photolysis temperature causes the formation of another product. The nature of the photoproduct i s inde-pendent of the temperature i n the c r y s t a l l i n e state. The r e s u l t s have been inte r p r e t e d i n terms of a required r i n g i n v e r s i o n which i s needed for the formation of the low temperature photoproduct (see Scheme 44). The r i n g i n v e r s i o n i s not allowed i n the s o l i d state. V TABLE OF CONTENTS Page ABSTRACT i i i LIST OF FIGURES x LIST OF SCHEMES x i i LIST OF TABLES x v i LIST OF ABBREVIATIONS x v i i ACKNOWLEDGEMENTS x v i i i INTRODUCTION Part 1 Synthesis of tetrahydro-1,4-anthracenediones . . . 2 Methods of Synthesis of o-quinodimethane f or Diels - A l d e r r e a c t i o n 6 1. From benzocyclobutene and i t s derivatives . . . 6 2. By photoenolization 8 3. By a 1,4-elimination reaction 9 4. Thermal or photochemical extrusion r e a c t i o n . . 12 Part II Photochemistry of tetrahydro-1,4-anthracenediones and tetrahydro-1-anthraceneones 1. General 14 A. Topochemical p r i n c i p l e 15 v i B. Role of defects 22 C . Concept of rea c t i o n c a v i t y 24 2. Photochemistry of tetrahydro-1,4-naphthoquinones 26 A . Ene-diones which react d i f f e r e n t l y i n i n the s o l i d state and s o l u t i o n 30 ( i ) Intermolecular [2+2] dimerization i n the s o l i d state 30 ( i i ) Intramolecular hydrogen atom abstraction 35 B. Ene-diones which react s i m i l a r l y i n the s o l i d state and s o l u t i o n 38 ( i ) Intramolecular [2+2] photo-cyc l o a d d i t i o n 39 ( i i ) Intramolecular hydrogen atom abstraction 40 ( i i i ) Oxetane formation 42 3. Photochemistry of tetrahydronaphthoquinols . . 44 4. Structure r e a c t i v i t y r e l a t i o n s h i p s : The geometric parameters associated with hydrogen atom abstra c t i o n 50 5. Objectives of the present research . . . . . . 54 RESULTS AND DISCUSSION Chapter 1 Part 1 Synthesis of tetrahydro-1,4-anthracenediones 60 1. Han and Boudjouk method 63 2. Ito method 64 (a) Reaction of ammonium s a l t 27 with duroquinone 65 (b) Reaction of ammonium s a l t 27 with 2,3-dimethyl-1,4-naphthalenedione 67 v i i (c) Reaction of ammonium s a l t 27 with tetraethyl-1,4-benzoquinone 69 (d) Reaction of ammonium s a l t 27 with 2,5-dimethyl-l,4-benzoquinone 70 (e) Reaction of ammonium s a l t 27 with 1,4-benzoquinone 73 Synthesis of acetate 70 and chlo r i d e 70 . . 76 3. Durst and Charlton method 79 Reaction of s u l t i n e 61 with p-quinones (a) with p-benzoquinone 80 (b) with 2-methyl-1,4-benzoquinone 82 (c) with 1,4-naphthalenedione 83 (d) with 2,5-dimethyl-1,4-benzoquinone . . . . 84 (e) with 2,3,5-trimethyl-1,4-benzoquinone . . . 87 Part II Synthesis of anthraquinols (a) Synthesis of enone 57A and 56B 89 (b) Synthesis of acetate 58B 94 (c) Synthesis of enone 59A 95 Chapter 2 Photochemistry of ene-diones 101 A. Ene-diones that behave s i m i l a r l y i n s o l i d state and s o l u t i o n 101 ( i ) Photochemistry of 2,4a-dimethyl-cis-4a,9a,9,10-tetrahydro-1,4-anthracenedione 101 ( i i ) Photochemistry of 2,4a-dimethyl-trans-4a,9a,9,10-tetrahydro-l,4-anthracenedione 113 B. Ene-diones that react d i f f e r e n t l y i n the s o l i d state than i n s o l u t i o n 115 v i i i ( i ) Photochemistry of 2,3,4a-trimethyl-cis-4a,9a,9,10-tetrahydro-1,4-anthracenedione 115 ( i i ) Temperature, m u l t i p l i c i t y and phase-dependent photochemistry of 2,3,4a,9a-tetramethyl-cis-4a,9a,9,10-tetrahydro-1,4-anthracenedione 123 ( i i i ) Photochemistry of cis-4a,9a,9,10-tetrahydro-1,4-anthracenedione 150 C. Ene-diones that react i n s o l u t i o n but not i n the s o l i d state 157 ( i ) Photochemistry of 5a,lla-dimethyl-cis-5a,11a,6,11-tetrahydro-5,12-naphthacenedione 157 ( i i ) Photochemistry of 2-methyl-cis-4a,9a,9,10-tetrahydro-1,4-anthracenedione 174 Chapter 3 Photochemistry of anthraquinols 180 A. Enones that react s i m i l a r l y i n the s o l i d state and s o l u t i o n 180 1. Photochemistry of 4a, 9a, 9 ,10-tetrahydro-4/3-(acetyloxy) -2,3,4a/3, 9a/3- tetramethyl-l(4H)anthracenone 180 2. Photochemistry of 4a, 9a, 9 ,10-tetrahydro-4/?-hydroxy- 2 , 3 , 4a/3, 9a$- tetramethyl-l(4H)anthracenone 186 B. Enones that react d i f f e r e n t l y i n the s o l i d state and i n s o l u t i o n 189 1. Photochemistry of 4a,9a,9,10-tetrahydro-4a-hydroxy-2 , 3 ,4aj9, 9aj3-tetramethyl-1(4H)anthracenone 189 2. Photochemistry of 4a, 9a, 9 ,10-tetrahydro-4,8-hydroxy-2 , 3 ,4a , 4a/3, 9a/3-pentamethyl-l(4H)anthracenone 196 Chapter 4 Photochemistry of Dienones 1. Photochemistry of 4,4, 8a-trimethyl-8ay9-carbomethoxy-cis-4a,5,8,8a-tetrahydro-l(4H)naphthalenone 203 i x 2. Photochemistry of 4,4,7-trimethyl-8aa-carbomethoxy-8a-acetyloxymethyl-cis-4a,5,8,8a-tetrahydro-l(4H)naphthalenone 212 Chapter 5 Quantitative structure - r e a c t i v i t y c o r r e l a t i o n s : geometric parameters f o r hydrogen atom abstract i o n 215 EXPERIMENTAL 229 REFERENCES 303 X LIST OF FIGURES Figure Page 1 32 2 33 3 40 4 50 5 51 6 68 7 85 8 90 9 92 10 99 11 103 12 105 13 109 14 112 15 115 16 121 17 122 18 130 19 137 20 141 21 144 22 167 x i 2 3 170 24 182 25 194 26 200 27 . 206 28 206 29 208 30 210 3 1 210 3 2 210 x i i LIST OF SCHEMES Scheme Page 1 3 2 5 3 5 4 10 5 12 6 16 7 19 8 19 9 20 10 21 11 21 12 23 13 25 14 27 15 29 16 31 17 31 18 34 19 35 20 36 21 37 22 38 x i i i x i v 4 7 145 4 8 147 4 9 • 148 5 0 151 5 1 153 5 2 154 5 3 155 5 4 158 5 5 161 5 6 • 162. 5 7 162 5 8 164 5 9 168 171 172 173 174 177 6 5 178 6 6 183 6 7 184 6 8 188 6 9 190 7 0 193 7 1 198 7 2 199 XV 73 74 75 76 201 212 219 222 xv i LIST OF TABLES Table Page 1 7 2 12 3 52 4 53 5 117 6 125 7 135 8 169 9 a 190 9 b 197 1 0 a 217 1 0 b 217 1 1 • • 270 1 2 271 1 3 271 1 4 274 1 5 • • • 300 x v i i LIST OF ABBREVIATIONS bp B o i l i n g point cone concentrated DMF Diraethylformamide EtOAc Ethyl acetate EtOH Ethanol GC Gas chromatography LDA Lithium diisopropylamide MP Melting point RT Room temperature t i c Thin-layer chromatography TBAF Tetrabutylammonium f l u o r i d e TEA Triethylamine THF Tetrahydrofuran TMS Tetramethylsilane TMS-C1 T r i m e t h y l s i l y l c h l o r i d e x v i i i ACKNOWLEDGEMENTS I would l i k e to thank Professor John R. Scheffer for h i s guidance and encouragement during my graduate studies and for h i s stimulating and h e l p f u l suggestions i n the course of t h i s research. I would also l i k e to thank Dr. Sara A r i e l , Mr. Fred Wireko and Professor James Tr o t t e r who performed a l l the X-ray crystallography reported i n t h i s t h e s i s . I also thank a l l my friends at the Chemistry Department and at U.B.C. e s p e c i a l l y Judy who made my stay most pleasant. I thank her for a l l her help during the preparation of t h i s t h e s i s . I would also l i k e to thank Kevin, Miguel and Phaniraj f o r proof-reading t h i s t h e s i s . I am very thankful to the Chemistry Department f o r f i n a n c i a l assistance i n the form of a teaching a s s i s t a n t s h i p . The cooperation and help from the departmental n.m.r., m.s., and elemental analysis labora-t o r i e s and the machine shop i s also acknowledged. x i x TO MY PARENTS BROTHERS, SISTERS AND JUDY - 1 -INTRODUCTION - 2 -PART 1 SYNTHESIS OF TETRAHYDRO-1,4-ANTHRACENEDIONES The photochemistry of Diels-Alder adducts formed between c y c l i c as well as a c y c l i c 1,3-dienes and p-quinones i s well e s t a b l i s h e d . ^ ' l 2 Interest i n the photochemistry of tetrahydro-1,4-naphthalenediones 1 arose when i t was discovered''--'-"^ 15 years ago, at the U n i v e r s i t y of B r i t i s h Columbia, that s o l u t i o n photolysis of these compounds r e s u l t s i n novel t r i c y c l i c products. A general example i s shown i n Scheme 1. However, when the photolysis was c a r r i e d out i n the c r y s t a l l i n e 1 ft 1 7 state, °'-L/ the r a t i o of the photoproducts shown i n Scheme 1 was e n t i r e l y d i f f e r e n t f o r some compounds. In l i g h t of the r e s u l t s shown i n Scheme 1 i t was thought, among other things, that the presence of an aromatic r i n g at the 6,7-position would not allow the formation of compounds of type 3, 5 and 7 because that would disrupt the aromaticity. Therefore, i t was decided to synthesize compounds of type 8 and then study t h e i r photochemistry. In p r i n c i p l e , tetrahydro-1,4-anthracenedione 8 can be synthesized by trapping the diene o-quinodimethane with p-quinones i n the Diel s -Alder r e a c t i o n . - ^ o-Quinodimethane, also known as o-xylylene, i s not a stranger to synthetic organic chemists. Its dibromo d e r i v a t i v e 10 was f i r s t implicated i n 1910 by H. F i n k e l s t e i n , ^ • 2 ^ by the rea c t i o n of a,a,a',a'-tetrabromoxylene 9 with sodium iodide as shown i n equation 1. 3 4 5 3,8-bonding 3,6-bonding ketonization ketonization Scheme 1 0 8 - 4 -Later, i t was shown by Cava and Napier^ 1 that compound 11 and not compound 10 was the correct structure f o r the F i n k e l s t e i n product. Cava and co-workers^•23 showed that 10 was an intermediate i n the rea c t i o n by trapping i t with a number of dienophiles as shown i n Scheme 2. Jensen and co-workers^'25 obtained adduct 12 (equation 2) by the thermolysis of 11 with maleic anhydride followed by dehydrobromination, thus demonstrating that o-xylylene could be regenerated by thermolysis of benzocyclobutene 11. At the same time, E r r e d e ^ showed that the decomposition of o-methylbenzyltrimethylammonium hydroxide 13 y i e l d e d o-quinodimethane 14 which under the re a c t i o n conditions, underwent dimerization to y i e l d two dimers 15a and 15b shown i n Scheme 3. Errede claimed that the spirodimer 15a was formed at lower temperatures, whereas dimer 15b was produced at higher temperatures. However, no reason f o r such behavior was given. Due to i t s extreme r e a c t i v i t y , o-quinodimethane has been of great i n t e r e s t to both e x p e r i m e n t a l i s t s ^ "30 a n c i t h e o reticians . 20 • For the same reason i t could not be i s o l a t e d u n t i l recently.^2 Flynn and Michl^^ were successful i n i s o l a t i n g t h i s compound i n a glassy matrix by 6 the photolysis of 1,4-dihydrophthalazine 16 at -196°C. Recently, however, Toda and co-workers J J i s o l a t e d o-quinodimethane derivatives 17 as stable c r y s t a l l i n e s o l i d s . I t d i d not take long before the synthetic importance of o-quino-dimethane was r e a l i z e d , and therefore several new methods f or generating 9 7 3 0 o-quinodime thane were developed. '" ~ > u In t h i s short review an attempt has been made to include almost a l l the known methods leading to o-quinodimethane. Intermolecular r e a c t i o n s 3 ^ of o-quinodimethane with various dienophiles w i l l also be mentioned. When possible, only dieno-ph i l e s that are of d i r e c t i n t e r e s t to the author ( i . e . quinones) w i l l be discussed. Intramolecular 2^> 2^• trapping of o-quinodimethanes w i l l not be discussed i n th i s t h e s i s . Methods of Synthesis of o-Quinodimethanes for D i e l s - A l d e r Reactions 1. From Benzocyclobutene and Its Derivatives This i s probably the most commonly used method f or forming the t i t l e compound because of the ready a v a i l a b i l i t y of benzocyclobutenes. 3^ 7 -The method involves heating the benzocyclobutenes to a high temperature (Table 1 l i s t s some of the t y p i c a l temperatures for various deriva-t i v e s ) . The r e a c t i o n proceeds by the r e v e r s i b l e conrotatory opening of a four-membered r i n g followed by s u p r a f a c i a l - s u p r a f a c i a l addition of o-quinodimethane 19 with the dienophile present as shown i n equation 3. 28 18 19 i Y li X A o r hf :3] Table 1: Approximate Reaction Temperatures for the Ring Opening of 18 19 (Reaction Time: 18 h ) . 2 8 Substituent R NH2 OH NHCOR' =0 H Temperature 25 80 140 150 200 (°C) R Z 18 E 8 Two points are worth mentioning with regard to the r i n g openings of benzocyclobutenes. F i r s t , the rate of r i n g opening depends on the substituent R, and second, the (E)-isomer forms i n preference to (Z)-quinodimethanes. Despite the ready a v a i l a b i l i t y of the s t a r t i n g material and also the ease with which substituted benzocyclobutenes undergo r i n g opening, the unsubstituted analogue reacts at a high temperature.^8 Therefore, b i s - e n o l i z a b l e adducts may not be stable under these r e a c t i o n condi-ti o n s . So when Kametani et a l . , , 36 - 38 w n j _ ] _ e synthesizing t e t r a c y c l i n e a n t i b i o t i c s , trapped o-xylylene with p-quinones, f u l l y aromatized products were obtained as shown below. 0 0 2. By Photoenolization^ I t i s very well established^^ * ^ 9-4-1 that ortho-alkyl substituted aromatic ketones containing 7-hydrogens undergo photoenolization quite smoothly. The r e a c t i o n proceeds by abstraction of a 7-hydrogen by the n,7r t r i p l e t state of the carbonyl group through a six-membered - 9 -t r a n s i t i o n state. In t h e i r pioneering work, Yang and R i v a s ^ 2 estab-l i s h e d that the r e s u l t i n g dienol 20 was s u f f i c i e n t l y l o n g - l i v e d to be trapped by dienophiles as i l l u s t r a t e d i n equation 4. H 20 Formation of o-quinodimethane species of type 20 does not n e c e s s a r i l y need a carbonyl oxygen for hydrogen abstraction. I t can also be brought about by a v i n y l i c carbon^ 3 as shown below. Several new applications of t h i s method have appeared,3^>34,37,44-46 and the dienophiles used, among others, are q u i n o n e s . 3 ^ • ^ > ^ A t y p i c a l example i s shown i n Scheme 4. Once again f u l l y aromatized quinones were obtained probably because DMF acts as a strong enough base to cause b i s - e n o l i z a t i o n of the tetrahydroadduct 23 i n i t i a l l y formed to give the corresponding hydroquinones. These hydroquinones get oxidized to f u l l y 10 -N a l , DMF 60-70°C - HBr 22 23 24 22a X = X' = Br, R = H b X = X' = Br, R = 0CH 3 c X = CI, X' = H, R = OCH3 Scheme 4 aromatic hydroquinones and f i n a l l y to f u l l y aromatic quinones 24. This property of quinones to undergo Diels-Alder r e a c t i o n with o-quinodi-me thanes to give f u l l y aromatic analogous p-quinones was c l e v e r l y u t i l i z e d by several w o r k e r s ^ • ^ >^ to make intermediate 25 for the synthesis of anthracyclinone 26. Han and Boudj ouVcA^»^® generated o-xylylene by the act i o n of zinc dust on a,a'-dibromoxylene at room temperature using ultrasound. Recently, Ito and co-workers^* developed a mild and e f f i c i e n t method to generate o-quinodimethane based on 1,4-elimination from [o-{a(trimethyl-silyl)methyl}benzyl]trimethylammonium halide 27. The 1,4-elimination was trigge r e d by f l u o r i d e anion-containing s a l t s such as te t r a b u t y l ammonium f l u o r i d e and cesium f l u o r i d e because of the high a f f i n i t y of f l u o r i d e towards s i l i c o n . The usefulness of t h i s r e a c t i o n was i l l u s -11 -trated by trapping the diene with several dienophiles. 1 ' • 3 Z Based on the property of a l l y l i c ethers to undergo 1,4-elimination on treatment with l i t h i u m dialkylamide (LDA), Rickborn and Moss-^ were successful i n preparing o-xylylene from o-tolualdehyde dimethylacetal 28. (X = NMe5Br) 27 U 28 12 4. By Thermal or Photochemical Extrusion Reactions This method takes advantage of the r e t r o c y c l o a d d i t i o n reaction which proceeds by elim i n a t i o n of a small molecule from the parent compound. Some of the compounds which have been used f o r t h i s purpose are shown i n Scheme 5. Compounds 16,27,32 and 29->^'^)-> underwent smooth photochemical e l i m i n a t i o n of N 2 and C=0 r e s p e c t i v e l y at or below room temperature to y i e l d o-quinodimethanes. Thermal extrusion of small molecules from compounds 30,-^'-^ 31,23,25 and 32^8-61 proceeded at quite high temperatures as shown i n Table 2. Only compound 3362,63 Table 2: Py r o l y s i s Temperatures of Compounds Shown i n Scheme 5 Compound Decomposition Temperature 30 300-500°C 31 200-300°C 32 150-200°C 33 80-100°C o£ 00 OCl V h 29 16 30 31 0 I S = 0 33 - 13 -underwent decomposition below 100°C. As before, the usefulness of these reactions were shown i n Diels-Alder reactions with various dienophiles (equation 5). - s o 2 •s=o '^\COOH 8 0 ° C ^ ^ k ^ x c o o H - 14 -PART II PHOTOCHEMISTRY OF TETRAHYDRO-1,4-ANTHRACENEDIONES AND TETRAHYDRO-1-ANTHRACENONES 1. General Considering the importance of photochemical reactions i n the h i s t o r y of mankind, i t i s very s u r p r i s i n g that only i n the past 35 years have photochemical reactions been extensively investigated. During t h i s period a large number of photochemical reactions has been added to the ever growing l i s t of chemical reactions. This does not mean that photochemical reactions were not examined before 1950, although photo-chemistry then was dependent on the weather, as Kan n o t e d . ^ With the advent of new l i g h t sources such as l a s e r s , progress i n t h i s area increased dramatically, and the p o t e n t i a l of photochemistry f o r the synthesis of unusual and i n t e r e s t i n g compounds was recognized. As e a r l y as 1880, when s o l u t i o n photochemistry was v i r t u a l l y unknown, German chemists were i n v e s t i g a t i n g photochemical processes i n c r y s t a l s , ^ 8 • ^ probably because of the u n a v a i l a b i l i t y or expense of solvents. However, development of t h i s f i e l d came to a h a l t because not enough was known at the time about the nature and structure of c r y s t a l s . Fortunately t h i s problem has been overcome i n the l a s t 30 years due to the advent of X-ray c r y s t a l l o g r a p h y , ^ > ^ a method that e s s e n t i a l l y "photographs" molecules and t h e i r neighbors i n three dimensions. There-- 15 -ft 9 79 ft ft fore, there i s a growing body of l i t e r a t u r e 0 c'°° av a i l a b l e today c o r r e l a t i n g r e a c t i v i t y with the structure of organic molecules i n the s o l i d state. A. The Topochemical P r i n c i p l e In the majority of s o l i d state photodimerization reactions, the c r y s t a l structure of the monomer i s d i r e c t l y r e l a t e d to the structure and stereochemistry of the photodimer. This i s the basis of the topo-chemical p r i n c i p l e , f i r s t enunciated by Kohlschutter i n 1918.77>88,89 The topochemical p r i n c i p l e states that, owing to the constraining envi-ronment present i n c r y s t a l s , reactions i n the s o l i d state proceed with a minimum of atomic and molecular movement. The s i t u a t i o n that p r e v a i l s i n the cinnamic acids i s shown i n Scheme 6. Cinnamic a c i d c r y s t a l l i z e s i n three polymorphic forms, a-type, /3-type and 7 -type . ^ 0, 91 ^ e Q-type c r y s t a l s shown i n Scheme 6 have intermolecular center-to-center distances of 3.6-4.1 A between the o l e f i n i c double bonds, and the monomer pa i r s are r e l a t e d by an a n t i -p a r a l l e l centrosymmetric arrangement. In the second type of c r y s t a l s (/?-type), the neighboring o l e f i n i c double bonds of monomer pa i r s are t r a n s l a t i o n a l l y equivalent with center-to-center distances of 3.9-4.1 A . L a s t l y , there are 7 -type c r y s t a l s , i n which the double bonds of adjacent monomers are o f f s e t i n such a way that they do not overlap very much and the distance between them i s 4.7-5.1 A. I r r a d i a t i o n of the c r y s t a l s of the trans-cinnamic acids y i e l d s 16 Packing, Requirements for S o l i d State T2+21 Photodimerization Y C O O H y B Ar--Ar • Ar o-type 5-type T-type Solid Solid Solid No Reaction Truxinic acids y C O O H Solution Ar C O O H Scheme 6 centrosymmetric t r u x i l i c a c i d dimers and mirror-symmetric t r u x i n i c acids from the a and ^-polymorphs re s p e c t i v e l y . The c r y s t a l s of the 7-polymorph are found to be unreactive. Schmidt et a l . ^ , 9 0 explained the photoinertness of the 7-polymorph i n terms of the larger distance and poor overlap between the adjacent double bonds of the monomers compared to the arrangement i n the a- and /3-trans-cinnamic acids. For [2+2] photocycloadditions, Schmidt^-* suggested an upper l i m i t of 4.2 A between the reactive double bonds. The authors also pointed out that i t i s not only necessary that the neighboring double bonds should be less than 4.2 A apart, but they should also be p a r a l l e l for a - 17 dimerization to occur. For example, i n case of m-bromo-trans-cinnamic acid, the adjacent double bonds of monomer pair s are only 3.9 A apart, but the c r y s t a l s of t h i s compound are photostable. The photoinertness of m-bromo-trans-cinnamic acid i s explained i n terms of the n o n - p a r a l l e l arrangement of the double bonds, which r e s u l t s i n a poor overlap between them. Q Q Ramamurthy et a l . have recently investigated the s o l i d state photochemistry of 28 coumarin derivat ives. They found that 7-chlorocou-marin I undergoes a topochemical dimerization even though the center-to-center distance between the neighboring molecules i s 4.5 A (higher than Schmidt's upper l i m i t of 4.2 A for photodimerizations). Furthermore, Q Q Ramamurthy et a l . also found that i n the case of 7-methoxycoumarin II the center to center distance between the o l e f i n i c double bonds i s 3.8 A, but the p o t e n t i a l l y reactive double bonds of the monomers are n o n - p a r a l l e l ; they are rotated by 65° with respect to each other r e s u l t i n g i n poor overlap between them. Since the dimerizations for both coumarins proceed i n a topochemical fashion, i t appears that both the upper l i m i t of 4.2 A and the p a r a l l e l i s m of the re a c t i v e double bonds may not be a s t r i c t requirement as suggested by Schmidt and may vary depending on the system. 7-methoxycoumarin 7-chlorocoumarin - 18 -Based on extensive c r y s t a l l o g r a p h i c and photochemical studies, S c h m i d t ^ a r r i v e d at the following conclusions, which are the basis of the topochemical p r i n c i p l e : 1. The i n t r i n s i c r e a c t i v i t y of a molecule i s less important than the nature of the packing of neighboring molecules around the reactant. The i m p l i c a t i o n here i s that the rea c t i o n i n the s o l i d state occurs with minimum atomic and molecular movement. 2. The separation distance, mutual o r i e n t a t i o n and space symmetry of the reactive f u n c t i o n a l groups are c r u c i a l . 3. In c r y s t a l l i n e s o l i d s there are very few (usually j u s t one) confor-mations taken up by molecules which i n the s o l u t i o n state may be f l e x i b l e . 4. Molecular c r y s t a l s (into which category the vast majority of organic s o l i d s f a l l ) display a r i c h d i v e r s i t y of polymorphic forms, i n each of which a p a r t i c u l a r conformer or a p a r t i c u l a r symmetry and separation of functional groups p r e v a i l . Based on these p r i n c i p l e s , photodimerizations of heteroanalogues of the trans-cinnamic acids (Scheme 7 ) , ^ benzylidene d e r i v a t i v e s (Scheme 93-98 butadiene d e r i v a t i v e s , ^  * fumaryl derivatives^-'- and coumarins^-^^ • have been r a t i o n a l i z e d . Unlike bimolecular reactions, where the packing mode of the monomers rather than the i n t r i n s i c r e a c t i -v i t y of the monomer i s the deriving force i n d i r e c t i n g the path of reactions, unimolecular reactions often follow an e n t i r e l y d i f f e r e n t r e a c t i o n pathway i n the s o l i d state. These les s motion unimolecular pathways proceeding under the influence of the c r y s t a l l a t t i c e often 19 Scheme 8 20 -require higher a c t i v a t i o n energies compared to greater motion pathways to d i s s i p a t e the energy associated with the photoexcited state. An e a r l y example which demonstrates how l a t t i c e constraints can d i r e c t the outcome of a unimolecular reaction i s shown i n Scheme 9. Dimers Cyclopentadienone Santonin Lumisantonin Scheme 9 Santonin upon i r r a d i a t i o n i n benzene undergoes a 'rearrangement to lumisantonin, whereas i n the s o l i d state, i t y i e l d s products assumed to be dimers of an unstable cyclopentadienone.-'-^ The mechanism of the l a t t e r transformation i s s t i l l unclear. Topochemical p r i n c i p l e s have also been used to explain the unmolec-u l a r reactions of indanones (Scheme 10),^8,109 i > i > 3 . t r i p h e n y l a c e t o n e (Scheme 10), ^ ® , a-cycloalkylacetophenone d e r i v a t i v e s (Scheme 11) ^ H - H ^ tetrahydro-1,4-naphthoquinones i9,16,17,72-76 a n c j tetrahydronaphthoqui-nols. ^ 2' " T h e l a s t two examples w i l l be discussed i n d e t a i l l a t e r . The examples mentioned above are rather random and by no means represent the scope of the vast f i e l d of organic s o l i d state photochem-i s t r y . The enthusiastic reader i s advised to read some of the very Ph2CHCCH2Ph h U • (PhCH ) + Ph.CHCHPh +(Ph„CH) - CO z z 1 2 2 . Benzene (Ratio) 1 : 2 - 1 Solid State 0 n l y Scheme 11 - 22 -recent review a r t i c l e s ^ > ^ • 8 8 which t r u l y represent the scope of various s o l i d state photochemical reactions. B. Role of Defects In contrast to those photodimerizations which follow topochemical p r i n c i p l e s , there are some reactions which can best be explained on the basis of molecules s i t u a t e d near defective s i t e s such as d i s l o c a -tions . 8 6 ' C r a i g and S a r t i - F a n t o n i 1 1 9 noted that the y3-forms of 9-cyanoanthracene and 9-anthraldehyde give h e a d - t o - t a i l photodimer, whereas head-to-head dimer would be expected from the c r y s t a l structure. The s i t u a t i o n i s shown i n Scheme 12. Similar observations were also made by Thomas et a l . 120-127 d u r i . n g photochemical studies of 9-substi-tuted anthracenes. Before any attempt i s made to explain the 'abnormal behavior' of some c r y s t a l s , i t w i l l be pertinent to explain how a normal re a c t i o n takes place i n the s o l i d state. When a c r y s t a l i s i r r a d i a t e d , three events can occur from the o r i g i n a l excited state, namely r a d i a t i v e and r a d i a t i o n l e s s deactivation, r e a c t i o n (dimerization i n the present example) and energy transfer. Assuming that the dea c t i v a t i o n process i s independent of the nature of the s i t e , when energy i s absorbed by molecules i n a c r y s t a l the reaction takes place at the s i t e where absorption occurred. Since the number of molecules s i t u a t e d at defects i s a small f r a c t i o n of those situated at regular l a t t i c e s i t e s (as determined by X-ray crystallography), the photochemistry of the c r y s t a l s 23 - 24 -i s governed by the regular l a t t i c e s i t e s . However, when the re a c t i o n i s slow, and i f the process of transfer of e x c i t a t i o n to the neighboring molecules i s e f f i c i e n t , then the photochemistry of the i d e a l l a t t i c e need not dominate. Since the normal symmetry of c r y s t a l s i s disrupted at d i s l o c a t i o n s or defects, the molecules at these s i t e s w i l l be l i k e l y to act as trapping centers for e x c i t a t i o n s . Under these circumstances, d i s l o c a t i o n s may act as favored s i t e s of reactions. Since the number of molecules at defective s i t e s i s small, m u l t i p l i c a t i o n i n defective s i t e s must propagate as the reaction progresses i n order to y i e l d appreciable amounts of photoproducts. C. Concept of the Reaction Cavity The topochemical p r i n c i p l e of Cohen and Schmidt*^ states that reactions i n s o l i d s take place with a minimum of atomic and molecular movement. Although t h i s p r i n c i p l e n i c e l y explained the dimerization i n planar trans-cinnamic a c i d d e r i v a t i v e s , i t was considered incomplete to explain a v a r i e t y of other s o l i d state reactions. For example, c i s -acids and s t e r i c a l l y hindered trans-cinnamic acids underwent c i s , t r a n s isomerization i n the s o l i d state.^5,86 Thus o-methoxy-cis-cinnamic acid gave c e n t r i c dimer along with the trans-acid. The molecules which are going to p a r t i c i p a t e d i r e c t l y i n a s o l i d state r e a c t i o n occupy a space of a c e r t a i n s i z e and shape i n the c r y s t a l . This space i s defined as the re a c t i o n c a v i t y . The molecular movements involved with the re a c t i o n may d i s t o r t t h i s c a v i t y and can - 25 -cause e i t h e r large decreases i n a t t r a c t i v e forces or large increases i n repulsive f o r c e s . 8 8 However, such d i s t o r t i o n s i n shape would be r e s i s t e d by the c l o s e l y packed environment. Therefore only those reactions which involve minimal change i n the surface of the reaction c a v i t y w i l l be e n e r g e t i c a l l y favorable. This formed the basis of the redefined topochemical postulate as: reactions proceeding under l a t t i c e c o n t r o l do so with minimal change or d i s t o r t i o n of the surface of the r e a c t i o n c a v i t y . The concept of the r e a c t i o n c a v i t y was found u s e f u l i n p r e d i c t i n g the course of reactions for which more than one pathway i s topochemically allowed.°8•106 obviously the r e a c t i o n with the l e a s t change i n r e a c t i o n c a v i t y w i l l be preferred (Scheme 13). Gavezotti's t h e o r e t i c a l c a l c u l a t i o n s 0 ^ •129 which conclude that a p r e r e q u i s i t e for Scheme 13 - 26 c r y s t a l r e a c t i v i t y i s the a v a i l a b i l i t y of free space around the reaction s i t e , also support the concept of reaction cavity. 2. Photochemistry of Tetrahydro-1,4-naphthoquinones The f i r s t tetrahydro-1,4-naphthoquinone whose photochemistry i n the s o l i d state was investigated was 34 by Di e l s and Alder i n 1929130 ^ s shown below. They reported that c r y s t a l s of t h i s compound, when photo-lyzed, y i e l d a polymeric material of unknown molecular weight. Many years l a t e r , Cookson and co-workers^ undertook the task of r e i n v e s t i g a t -ing t h i s reaction. They also found, i n agreement with D i e l s and Alder, that c r y s t a l s or ethyl acetate solutions of ene-dione 34 gave mainly polymeric material when photolyzed at A > 290 run. They t e n t a t i v e l y assigned the product 35d as a dimer of unknown stereochemistry. At t h i s point i t may be appropriate to explain the numbering system used i n t h i s t h e s i s . Letters such as CB and CP etc. have been used a f t e r arable numerals to indic a t e the o r i g i n and the nature of the product(s) formed. For exmple 34CP indicates that the product i s cyclopentanone type o r i g i n a t i n g from the ene-dione 34. The following i s the complete l i s t of l e t t e r s used i n t h i s thesis to indicate the nature of the product(s) and/or intermediate(s) formed and t h e i r meanings. CB (cyclobutanone), CP (cyclopentanone), BR ( b i r a d i c a l ) , EA (enone alc o h o l ) , d (dimer), OX (oxetane), S ( s o l i d state photolysis product), L ( l i q u i d photolysis product), P (propanol), L (lactone), KA (ketoaldehyde), K ( k e t a l ) , KE (ketoenol). I f more than one product of the same type forms from the same ene-dione, such other photoproduct has been r e f e r r e d with a dash, f o r example 34CP'. - 27 -More recently, however, Scheffer et a l . ' ' '^ -"'-) became int e r e s t e d i n the s o l u t i o n and l a t e r i n the s o l i d state photochemistry of ene-dione 34. When s e l e c t i v e l y photolyzed i n s o l u t i o n (A > 340 nm), extensive tar formation took place, as reported by Cookson et a l . However, c a r e f u l study of the tar showed the formation of two isomeric photoproducts, though i n poor y i e l d . Those compounds were i s o l a t e d and i d e n t i f i e d as the novel t r i c y c l i c products 34CP and 34CP' as shown i n Scheme 14. Scheme 14 28 -The adduct 34 was also photolyzed i n the s o l i d state. Indeed the dimeric compounds 34d, i n agreement with Cookson et a l , formed. However, Scheffer et a l . s u c c e s s f u l l y assigned the stereochemistry of the adduct 34d by X-ray crystallography as shown i n Scheme 14. The questions which immediately arose were: 1. What i s the mechanism of the r e a c t i o n shown i n Scheme 14? 2. Why does ene-dione 34 react d i f f e r e n t l y i n the s o l i d state and solution? 3. Of the many possible stereoisomeric products, why does only 34d form i n the s o l i d state? In contrast to unsubstituted ene-dione 34, hexa-substituted ene-dione 36 d i d not react photochemically i n the s o l i d state to give a dimer. Instead i t reacted v i a hydrogen atom abstrac t i o n both i n the s o l i d state and s o l u t i o n to give the products shown i n Scheme 15. Since the behavior of compound 36 was d i f f e r e n t from that of 34 i n the s o l i d state as well as i n s o l u t i o n , the following question was asked: 4. Why does substrate 36 not undergo [2+2] dimerization i n the s o l i d state l i k e compound 34? Since ene-dione 36 reacts v i a i n i t i a l hydrogen atom abstraction, other questions are: 5. Over what distances can hydrogen abstraction occur? 6. What i s the preferred geometry for abstraction? 7. Can a b s t r a c t i o n be f a c i l i t a t e d r e l a t i v e to competing processes by f r e e z i n g the reactant molecule i n a favorable s o l i d state conforma-tion? - 29 0 + Solvent Benzene t-Butanol A c e t o n l t r i l e Methanol 1:1 Dioxane:Water S o l i d State 36CB 36EA + 36CB + Ratio 36CB 0.5 1.1 4 13 30 3 36EA 1 1 1 1 1 2 36CP 36CP Scheme 15 In order to answer a l l the questions r a i s e d Scheffer's group systematically investigated the substituted tetrahydro-1,4-naphthoquinone derivatives above, Professor photochemistry of 30 -Depending on t h e i r r e a c t i v i t y , ene-diones studied both i n the s o l i d state and i n s o l u t i o n can be arranged into two d i f f e r e n t groups. (a) Ene-diones which react d i f f e r e n t l y i n the s o l i d state and sol u t i o n . (b) Ene-diones which react s i m i l a r l y i n the s o l i d state and sol u t i o n , (a) Ene-diones Which React D i f f e r e n t l y i n the S o l i d State and Solution This s e c t i o n has been further divided into two groups: ( i ) Inter-molecular [2+2] dimerization i n the s o l i d state, and ( i i ) Intramolecular hydrogen atom abstrac t i o n reactions. ( i ) Intermolecular [2+21 Dimerization i n the S o l i d State Ene-diones 34, 37 and 38 y i e l d intermolecular [2+2] dimers when photolyzed i n the c r y s t a l l i n e state. When i r r a d i a t e d i n sol u t i o n , novel t r i c y c l i c products are formed. The r e s u l t s are summarized i n Scheme 16 and Scheme 17. In order to understand t h i s behavior, the X-ray c r y s t a l structures of ene-diones 34 and 38 were determined by T r o t t e r et a l . • l 3 2 Crystals of ene-dione 37 were unsuitable f or X-ray crystallography. X-ray c r y s t a l structure analysis showed that the two neighboring molecules of compound 34 pack i n such a way that the ene-dione double bonds are p a r a l l e l i n a top-to-bottom fashion. The center-to-center distance was found to be 3.76 A, thus i d e a l l y f i x e d to undergo [2+2] intermolecular dimerization. Moreover, the i n c i p i e n t 31 -37EA 37CP' 37CP Scheme 16 Scheme 17 dimer has a stereochemical r e l a t i o n s h i p that i s i d e n t i c a l to that found i n the photoproduct. The s i t u a t i o n i s shown i n F i g . 1. Thus, formation of the dimer 34d i s a topochemical phenomenon s i m i l a r to the dimerization of the cinnamic a c i d d e r i v a t i v e s studied by Schmidt.^ In the same way c r y s t a l s of 38 also packed i n such a fashion 32 -Dimer 34d 34 Figure 1: that ene-dione double bonds are p a r a l l e l with a center-to-center distance of 4.04 A. Therefore 38 l i k e 34 gives a photodimer i n the s o l i d state. The X-ray c r y s t a l structures also revealed that ene-diones 34 and 38 (and a l l other ene-diones studied by Scheffer's group so f a r ) e x i s t i n a conformation where bridgehead hydrogen atoms are staggered with a t o r s i o n angle of 60° about the C(4a)-C(8a) b o n d . 7 2 , 7 5 In t h i s conformation, which the authors r e f e r to as the "twist" conformation, the h a l f - c h a i r cyclohexene moiety i s c i s - f u s e d to a more nearly planar cyclohex-2-en-l,4-dione r i n g . H a l f - c h a i r to h a l f chair r i n g inversion leads to two possible twist conformations (A and B) f o r each ene-dione (Fig. 2). The s i t u a t i o n i s very d i f f e r e n t i n s o l u t i o n since the molecules do not experience any l a t t i c e r e s t r a i n t s that are observed i n c r y s t a l s . Scheffer et a l . ^ 7 assumed the same-twist conformation i n s o l u t i o n as i n 33 -3 0; 0 '0 A B Figure 2: the s o l i d state. In t h i s twist conformation, 0(1) i s i d e a l l y s i t u a t e d to abstract an e n d o - a l l y l i c hydrogen atom from C(8) to give a C ( l ) , C ( 8 ) - b i r a d i c a l 34BR (Scheme 18). This C ( l ) , C ( 8 ) - b i r a d i c a l 34BR can collapse to give a cyclopropanol type product 34P a f t e r conformational inversion. However, no product of type 34P has ever been i s o l a t e d . B i r a d i c a l 34BR can isomerize and collapse to y i e l d 34CP and 34CP'. I t can also y i e l d 34EA, but t h i s product was only i s o l a t e d i n the case of substrate 37. The mechanistic s i t u a t i o n i s summarized i n Scheme 18. The favored conformation of ene-dione 38 i s assumed to be the same i n the s o l i d state as i n s o l u t i o n and i s exactly l i k e 34, i . e . a twist conformation. Scheffer et a l . i n t h e i r e a r l i e r s t u d i e s ^ showed that the a l l y l i c hydrogen atom that i s abstracted must be endo-/9(8H). Since compound 38 does not possess an endo-£(8H), 0(1) abstracts a hydrogen atom from the methyl group through a six-membered t r a n s i t i o n state. The r e s u l t i n g b i r a d i c a l , a f t e r conformational isomerization, couples to give the t r i c y c l i c product 38CP". The r e s u l t s are depicted i n Scheme 19. - 34 -hi/ 34 (R = H ) 37 (R = CH 3) 34CP' 37CP' 1. 3,6—bonding 2. Ketonizotion 1,8-bonding 1. 3,8—bonding 2. Ketonizotion 34CP 37CP 34P, 37P (not isolated) 34BR'" 37BR"' Scheme 18 - 35 -Scheme 19 ( i i ) Intramolecular Hydrogen Atom Abstraction i n the S o l i d State Two ene-diones, 36 and 39, f a l l into t h i s category. Their intramolecular hydrogen atom abstraction reactions are shown i n Scheme 15 and Scheme 20 re s p e c t i v e l y . As shown i n Scheme 20, when compound 39 was photolyzed i n the s o l i d state, i t y i e l d e d enone-alcohol 39EA, whereas i n s o l u t i o n , 39EA as well as 39CP were obtained i n the r a t i o s shown i n Scheme 20. S i m i l a r l y , compound 36 gave 36EA and 36GB i n r a t i o of 2:3 i n the s o l i d state whereas i n s o l u t i o n 36EA, 36CB and 36CP were obtained i n a r a t i o depending on s o l v e n t . ^ Three i n t e r e s t i n g observations were made i n the cases of compounds 36 and 39: 1. Intermolecular [2+2] dimerization does not take place, instead hydrogen atom abstrac t i o n occurs. 2. Compounds 36CP and 39CP do not form i n the s o l i d state. 3. A new kind of product, 36CB, i s formed both i n the s o l i d state and so l u t i o n . 36 -3.0 h 3.1 h 3.9 h 3:1 3:2 1:2 Scheme 20 Scheffer et a l . ' explained these observations with the help of X-ray crystallography. The packing diagram-*-33 >-*-3^ showed that the ene-dione double bonds i n compounds 36 and 39 were neither p a r a l l e l nor close enough to permit intermolecular dimerization. Therefore, these substrates undergo hydrogen atom abstraction by 0(1) and C(3) (36 only). The d e t a i l s of hydrogen abstraction by C(3) w i l l be discussed l a t e r . Substrates 36 and 39, l i k e t h e i r predecessors, also e x i s t i n twist conformations and are i d e a l l y suited to undergo hydrogen atom abstrac-t i o n by 0(1). After.H-atom abstraction, the b i r a d i c a l s 36BR and 39BR are formed, and these can couple to give 36EA or 39EA. The photopro-ducts 36EA and 39EA have e s s e n t i a l l y the same basic shape as ene-diones - 37 36 and 39 re s p e c t i v e l y . B i r a d i c a l 36BR can also undergo r i n g inversion to give b i r a d i c a l 36BR' i n which the r a d i c a l centers are close enough to couple to y i e l d 36CP. Since such gross conformational changes are allowed only i n s o l u t i o n and not i n the s o l i d state due to c r y s t a l l a t t i c e e f f e c t s (Scheme 21), substrate 36CP i s formed only i n s o l u t i o n and not i n the s o l i d state; the same explanation holds f o r 39CP. 1,6-bonding • ^ 36EA, 39EA Not allowed in solid state Substituents omitted f o r c l a r i t y 1. Bonding^ \ 2. Ketonization 36BR', 39BR' 36CP, 39CP Scheme 21 Cyclobutanone 36CB formation was shown by Scheffer et a l . i / to also come from the twist conformation. The mechanism of formation of 36CB i s depicted i n Scheme 22. X-ray crystallography revealed that the endo-H(5) atom l i e s d i r e c t l y over the ene-dione carbon-carbon double 38 bond. Transfer of t h i s hydrogen atom to C(2) through a six-membered t r a n s i t i o n state produces b i r a d i c a l 36BR". This b i r a d i c a l closes by bonding between C(3) and C(5) to y i e l d the observed product. As before, i t was found that 36CB also has the same basic shape as the parent ene-dione 36. Scheme 22 Scheffer et a l . also suggested that 36CP and 36EA are formed from an excited state d i f f e r e n t from that involved i n the formation of 36CB. The formation of 36CP and 36EA takes place from the n,7r* s i n g l e t state, whereas 36CB comes from the 7r,7r t r i p l e t state. This conclusion was supported by photophysical studies. (b) Ene-diones Which React S i m i l a r l y i n the S o l i d State and Solution There are three d i f f e r e n t kinds of reactions that are observed i n thi s section. ( i ) Intramolecular [2+2] photocycloaddition, ( i i ) Intra-molecular H-atom abstraction, and ( i i i ) Oxetane formation. 39 (i ) Intramolecular [2+21 Photocycloaddition Cookson et a l . ^  also investigated the photochemistry of bridged t r i c y c l i c ene-diones 40 and 41. They found that these compounds undergo intramolecular [2+2] cyc l o a d d i t i o n y i e l d i n g cage compound 40CP" and 41CP", both i n the s o l i d state and i n s o l u t i o n . The r e s u l t s are depicted i n Scheme 23. 0 Scheme 23 In order to understand the behavior of bridged t r i c y c l i c ene-diones i n the s o l i d state, T r o t t e r and Greenhough-'-^^ determined the X-ray c r y s t a l structure of ene-dione 41. They found that the conformation of substrate 41 was very d i f f e r e n t from that of ene-dione 34 as shown i n F i g . 3. Unlike the twist conformation of ene-dione 34, 41 exi s t s i n a - 40 conformation i n which the two intramolecular double bonds are p a r a l l e l and are 3.53 A apart. This arrangement, as expected on the basis of the Q Q topochemical p r i n c i p l e , * leads to intramolecular [2+2] photocycloaddi-t i o n to y i e l d cage compound 41CP". Moreover, T r o t t e r and Greenhough noted that there are no p a r a l l e l intermolecular double bonds les s than 4.2 A apart. The same conformation as i n s o l i d state can also e x i s t i n s o l u t i o n , and hence the same product i s formed. Figure 3: ( i i ) Intramolecular Hydrogen Atom Abstraction As shown i n the case of hexamethyl adduct 36 (Scheme 15), when the c r y s t a l l a t t i c e arrangement i s such that no intermolecular [2+2] addi-t i o n can take place, hydrogen atom abstrac t i o n becomes the major reac-t i o n pathway. Ene-diones 42 and 43 belong i n t h i s category. Hydrogen atom abstrac t i o n H(8) by 0(1) takes place to give the b i r a d i c a l s 42BR and 43BR. Scheffer et a l . 1 7 found that the b i r a d i c a l formed a f t e r H(8) hydrogen abstra c t i o n combined at p o s i t i o n s C(l) and C(6) to give enone-alcohol 42EA or 43EA as the sole product (Scheme 24). The authors - 41 43BR 43EA Scheme 24 argued that 42CP type product, though possible f o r enone 42, was not observed because the formation of 42CP requires r i n g i n v e r s i o n to give 42BR' i n which the r a d i c a l centers are close enough to couple to y i e l d 42CP. This conformational isomerization was suggested to be slower i n s o l u t i o n than the rea c t i o n from b i r a d i c a l 42BR. As i n the case of other ene-diones discussed e a r l i e r , the basic shapes of 42EA and 43EA are 42 -e s s e n t i a l l y the same as those of s t a r t i n g ene-diones 42 and 43. Although an e f f i c i e n t conformational isomerization of the type 42BR » 42BR' can be allowed f o r 43BR, the formation of CP type product, which requires bonding between the C(3) and C(8) r a d i c a l centers, does not take place because i t would disrupt the aromaticity. ( i i i ) Oxetane Formation Compounds 44 and 45 upon i r r a d i a t i o n i n s o l u t i o n y i e l d e d only oxetane 44-OX and 45-OX re s p e c t i v e l y (Scheme 25). Ene-dione 44 gave oxetane 44-OX i n the s o l i d state as well, whereas the photochemistry of 45 i n the s o l i d state was not investigated. 44 H 44-OX 0 H 45 45-OX Scheme 25 - 43 The c r y s t a l structure of ene-dione 44 showed that i t had essen-t i a l l y the same conformation as that of ene-dione 38 discussed e a r l i e r . Substrate 44 cannot undergo [2+2] dimerization because the molecular packing i n the c r y s t a l precludes i t , an argument supported by X-ray crystallography. This compound cannot abstract an endo-H(5) hydrogen because there i s none. I t can, however, abstract a 7-hydrogen atom from the methyl group through a six-membered t r a n s i t i o n state (Norrish type II reactionl-^^, 137) t o give a b i r a d i c a l 44BR analogous to 38BR (Scheme 19). In order to form a product of type 38CP.H conformational isomerization of 44BR^—^ 44BR' i s required. This isomerization i s p r o h i b i t e d i n the s o l i d state and therefore 44CP" does not form i n t h i s medium (Scheme 26). Scheffer et a l . ^ suggested that conformational 44CP" Scheme 26 - 44 -isomerization of 44BR ===== 44BR' i s quite slow i n s o l u t i o n as well due to the bridgehead cyano group. As a l a s t resort, the excited state under-goes intramolecular oxetane formation to d i s s i p a t e i t s energy. The authors argue that t h i s process of oxetane formation has a very low o v e r a l l rate constant because t h i s r e a c t i o n i s geometrically possible but unobserved for a l l of the ene-diones. 3. Photochemistry of Tetrahydronaphthoquinols Having investigated the photochemistry of tetrahydro-1,4-naphtho-quinone d e r i v a t i v e s , 7 2 • • the photochemistry group at U.B.C. turned to investigate the photochemical reactions of tetrahydronaphthoquinols (which w i l l be frequently r e f e r r e d to as enones i n the text) having the general structure 46 shown below. R O 46 Substrate 46 and i t s derivatives were e a s i l y synthesized by sodium borohydride reduction of the corresponding ene-diones. One such enone, for which R =CH3 was prepared by treatment of ene-dione 36 with methyl li t h i u m . Altogether nine enones were studied by Scheffer et a l . ^ ^ - ^ 45 -Upon photolysis i n solu t i o n , a l l nine enones underwent intramolecular [2+2] photocycloaddition leading to cage compounds, for example 46AL (Scheme 27) . Scheme 27 However, i n the s o l i d state photblyses, H(51) hydrogen atom abstrac-t i o n by the C(3) carbon through a five-membered t r a n s i t i o n state took place, and the r e s u l t i n g b i r a d i c a l coupled at po s i t i o n s C(2) and C(5) to give 46AS (Scheme 27). The epimer of enone 46A, 46B, on photolysis i n so l u t i o n , also underwent [2+2] intramolecular r e a c t i o n to give the tetracyclo[5.3.0.0. 2>6Q 4 , 9 ] d e c a n e r i n g compound 46BL. This photo-product, however, underwent hemiketal formation to y i e l d 46BK'. The s i t u a t i o n i s given i n Scheme 28. Enone 46B formed 46BS i n the s o l i d state p h o t o l y s i s . The s o l i d state reaction involved a b s t r a c t i o n of the hydrogen atom H(81) by the C(3) enone carbon through a six-membered t r a n s i t i o n state. The C(8), C(2) r a d i c a l centers then combine to a f f o r d - 46 -Scheme 28 46BS (Scheme 29). Cyclobutanone 46BS, as i n so l u t i o n , also undergoes hemiketal formation to produce 46BK as the sole i s o l a t e d product. Two very fundamental questions were asked about the r e s u l t s summa-r i z e d above. 1. Why are the products obtained i n the s o l i d state d i f f e r e n t from the products formed i n solution? 47 51 46B 46BS substituents omitted f o r c l a r i t y Scheme 29 2. Why do epimers 46A and 46B react d i f f e r e n t l y i n the s o l i d state? The answers to these questions came from X-ray crystallography. Scheffer and co-workers found that the conformations of enones of type 46 were determined by the preference f o r the b u l k i e r substituent at C(4) to adopt the les s hindered pseudo-equatorial p o s i t i o n . A l l nine com-pounds c r y s t a l l i z e d i n one of the two possible conformations r e f e r r e d to as A or B. For example, compound 46A c r y s t a l l i z e d i n conformation A, whereas 46B c r y s t a l l i z e d i n conformation B. The authors also noted that i n s o l u t i o n , conformers A and B were i n equilibrium through conformer C - 48 among others (Scheme 30). With c r y s t a l l o g r a p h i c information i n hand, the mechanism of formation of compounds 46AS and 46BS from 46A and 46B re s p e c t i v e l y can e a s i l y be understood, as i l l u s t r a t e d i n Scheme 29. Scheme 30 Solution Versus S o l i d State Photochemistry Scheffer et a l . argued that intramolecular [2+2] photocycloaddition i n the s o l i d state i s topochemically disallowed based on the f a c t that the X-ray c r y s t a l structure analysis shows that the double bonds are - 49 neither close nor p a r a l l e l to one another. This led them to suggest that [2+2] c y c l o a d d i t i o n i n s o l u t i o n occurs from a conformation d i f f e r -ent from A or B. They pointed out that i t should be 'C, i n which the double bonds are p a r a l l e l and i n close proximity to one another. Thus, three d i f f e r e n t conformations are postulated. Scheme 30 summarizes the s i t u a t i o n . As stated e a r l i e r , reactions i n the s o l i d state occur ei t h e r from conformation A or B. Based on a k i n e t i c scheme (Fig. 4) proposed by Lewis et a l . ^ - 3 8 for conformational isomers reacting photochemically i n s o l u t i o n to give d i f f e r e n t products, two l i m i t i n g s i t u a t i o n s can occur. In case I the a c t i v a t i o n energy for conformational isomerization i n the excited state i s l e s s than (or greater than, case II) the primary photochemical steps. In case I I , the r a t i o of products w i l l depend upon the excited state conformer population (A*, B* and C*), and since e x c i t a t i o n i s much fa s t e r than molecular motion (Frank-Condon p r i n c i p l e ) , on the ground state conformer population. Scheffer et al.H-* argued that C i s the minor conformer i n s o l u t i o n and i s very u n l i k e l y to have an e x t i n c t i o n c o e f f i c i e n t d i f f e r e n t from A or B, and therefore s i t u a t i o n I applied. Thus, the Curtin-Hammett principle- 1- explains the s i t u a t i o n , which means that the conformational equilibrium i s established during the l i f e t i m e of the excited state, and the photoproduct composition depends only upon the r e l a t i v e photochemical a c t i v a t i o n energies. In order to explain the predominance of [2+2] photocycloaddition, the authors postulated that » K^.Kg. This s i t u a t i o n i s shown schematically i n F i g . 4. - 50 -^ B A* C* B* K H-atom abstra-c t i o n product (5-membered t.s.) (2+2)cyclo-a d d i t i o n product H-atom abstraction product (6-membered t.s.) Figure 4: K i n e t i c scheme for [2+2] cyc l o a d d i t i o n i n s o l u t i o n 4. S t r u c t u r e - R e a c t i v i t y Relationships: The Geometric Parameters Associated with Hydrogen Atom Abstraction Three parameters have been used by Scheffer et a l . ' ^ - 75 t o characterize the geometric r e l a t i o n s h i p s between the abstracting oxygen or carbon atom and the hydrogen atom being abstracted. These are: d, the distance between the abstracting atom and the abstracted atom i . e . 0---H and C---H distances; r, the angle formed between the 0 - - - H or C - - - H vector and i t s p r o j e c t i o n on the mean plane of the carbonyl group or the ene-dione c e n t r a l double bond; and A, the C=0-•-H or C=C---H angle. A fourth parameter i s the distance between carbon atoms C - -'C that eventually become bonded together i n the f i n a l product. These parameters are shown i n Fi g . 5 for ene-diones and enones. - 51 -Figure 5: D e f i n i t i o n of r, A and d The values of d, r and A for almost a l l the enones and ene-diones that underwent H-atom abstrac t i o n i n the s o l i d state are shown i n Tables 3 and 4. 7 3 From the c r y s t a l l o g r a p h i c d a t a 7 3 shown i n Tables 3 and 4, Scheffer et a l . made the following generalizations for intramolecular photochemi-c a l reactions. 1. Intramolecular hydrogen atom abstrac t i o n can occur over distances that are l e s s than or equal to the sum of the van der Waals r a d i i of the atoms involved (2.7 A for 0-•-H and 2.9 A f o r C---H). The average experimentally determined v a l u e s 7 3 for hydrogen atom abs t r a c t i o n by oxygen and carbon were 2.5 A and 2.8 A, respec-t i v e l y . 2. The i d e a l angles ( T 0 and A D) for hydrogen abstraction by oxygen should be 0° and 90" respectively. The experimentally determined 7 3 average values f o r r Q and A Q were 6° and 86° r e s p e c t i v e l y . - 52 -Table 3 : The Hydrogen by Oxygen (carbon) through Flve-membered (Six-membered) T r a n s i t i o n State Ene-dione d (A) r Q (r c)° A Q (A c) C(l)---C(6) [C(2)•••C(8)] distance 36 2.5 0 85 3.4 (3.2) 36 2.8 (52) (73) 38 2.4 (r) 15 101 3.4 a 39 2.5 3 81 3.5 42 2.6 8 84 3.4 43 2.6 5 81 3.5 estimated distance a f t e r conformational inversion. 53 -Table 4: The Hydrogen Abstraction by Carbon Through Five- and Six-membered T r a n s i t i o n States. 46 lone 46 Rl R 2 R 3 R 4 *5 d (A) Ac (°) C2-•-C5 distancf a Me H Me Me H (c i s / R 3 ) 2.7 53 79 3.2 b Me H Me Me H (trans/R 3) 2.9 50 75 3.3 c Me H Me Me Me (trans/R 3) 2.8 50 78 3.3 d H H Me Me H ( c i s / R 3 ) 2.8 52 78 3.2 e H H Me Me H (trans/R 3) 2.9 51 72 3.3 f Me H H Me H (trans/R 3) 2.8 54 79 3.0 g H H H Me H (trans/R 3) 2.8 54 80 3.4 54 -3. The i d e a l angles ( r c and A c) for hydrogen abstraction by carbon should be 90° each. The average angle measured by Scheffer et a l . ^ ^ f o r T c a n ( j A c was 52° and 76° r e s p e c t i v e l y . 4. The distances between the carbon atoms that eventually became bonded to one another may be equal to or less than the sum of van der Waals r a d i i of two carbon atoms (3.4 A). The average distance found was 3.3 A for ene-diones. I f t h i s distance s u b s t a n t i a l l y exceeds 3.4 A, bond formation may be incompatible with the r e s t r a i n t s of the c r y s t a l l a t t i c e and no net chemistry may be observed. 5. Objectives of the Present Research The major goals of the present in v e s t i g a t i o n s are three f o l d . (a) E f f e c t of 6.7-Benzo Group on the Photochemistry of Naphthalene- diones What e f f e c t does the benzo-substituent at the 6,7-position of naphthalenediones such as the benzoquinone/1,3-butadiene adduct 34 and the duroquinone/2,3-dimethyl-l,3-butadiene adduct 36 have on t h e i r photochemistry. We expect that an aromatic r i n g at the 6,7-positions would not allow the products a r i s i n g from 1,6 and 3,6-bonding. There-fore, the y i e l d s f o r products a r i s i n g from other pathways can be optimized. In order to investigate the e f f e c t of 6,7-benzo substitu-ents, the following compounds were selected f or study (Scheme 30a). 55 -0 53 Scheme 30a (b) E f f e c t of 2.3- and 6.7- Benzo Substit u t i o n on the Photochemistry of  Naphthalenediones How w i l l naphthalenediones benzo-substituted at both the 2,3- and 6,7-positions react i n s o l u t i o n and the s o l i d state? What w i l l the photoproducts be? We have two expectations: f i r s t , hydrogen atom abstract i o n by the ene-dione carbon w i l l not be possible. Second, the 1,3-biradical formed a f t e r /3-hydrogen atom abstraction by oxygen cannot undergo bond formation between the 1,6- and 3,6- and 3,8-centers (see - 56 -Scheme 1). Therefore, the b i r a d i c a l formed w i l l have only one mode of combination a v a i l a b l e , that i s 1,8-bond formation to y i e l d a cyclopropa-nol type of photoproduct. The following two compounds were selected for t h i s purpose. (c) E f f e c t of 6.7-Benzo Substitution on the Photochemistry of  Naphthoquinols Naphthoquinols have been shown to undergo [2+2] intramolecular c y c l o a d d i t i o n i n s o l u t i o n to give cage compounds (Scheme 27 and 28). I t i s i n t e r e s t i n g to study what w i l l happens when [2+2] intramolecular dimerization i s not favored i n s o l u t i o n because i t involves d i s r u p t i o n of aromaticity. W i l l products from both conformation A and B a r i s e i n solution? In order to study the e f f e c t of 6,7- benzo-substitution on the photochemistry of naphthoquinols, the following compounds were selected. 0 55 54 - 57 (d) Synthetic Approaches to Tetrahvdro-1.4-anthracenediones and  Anthraquinols Before any of the objectives discussed above can be achieved, i t i s necessary that synthetic methods leading to the formation of the target compounds be uncovered. Thus another important objective of the present research i s to f i n d methods to synthesize ene-diones (47-55) and enones (56B-59A). (e) Other (General) Objectives In the recent l i t e r a t u r e - ^ • • 7 2 ' 8 ^ there has been a great deal of d i s c u s s i o n concerning the geometric requirements for hydrogen atom ab s t r a c t i o n by oxygen as well as by carbon. What are these geometric - 58 -requirements and how are they applicable i n the present study? The values of the geometric parameters such as d, r c ( r Q ) and A c (A Q) (see F i g . 5 for d e f i n i t i o n s of d, r and A) can be obtained from X-ray crystallography. I t i s well established that most organic compounds tend to c r y s t a l -l i z e i n one (minimum energy) conformation, whereas i n s o l u t i o n , multiple conformations e x i s t . Therefore, i t may be possible to study conforma-t i o n - s p e c i f i c photochemistry i n the s o l i d state. How can s o l i d state r e a c t i v i t y be c o r r e l a t e d with the conformation i n the s o l i d state and thus be used as a method to carry out mechanistic studies? F i n a l l y , from a t o t a l l y synthetic point of view, how can s o l i d state reactions be used to prepare target molecules i n good y i e l d s ? - 59 -RESULTS AND DISCUSSION 60 -CHAPTER 1 PART 1 SYNTHESIS OF TETRAHYDRO-1,4-ANTHRACENEDIONES The Diels-Alder adducts of general structure 1 can e a s i l y be prepared by the cy c l o a d d i t i o n r e a c t i o n of a 1,3-diene with the corres-ponding 1,4-quinones. For example, adduct 37 was synthesized by heating 2 , 3-dimethyl-l, 3-butadiene with 1,4-benzoquinone at 65°C,-'-';*l whereas the compound 36 was obtained by the addition of 2,3-dimethyl-l,3-butadiene to duroquinone at -190°C i n a sealed tube. I 37 36 By analogy, the most d i r e c t method f or the synthesis of the required tetrahydro-1,4-anthracenedione 47 and i t s d e r i v a t i v e s would be through Di e l s - A l d e r r e a c t i o n of 1,4-benzoquinone to the diene o-quino-dimethane (14) as shown i n equation 6. Unlike stable, commercially a v a i l a b l e dienes used to synthesize the adducts of general structure 1, o-quinodimethane, as mentioned i n the Introduction section, i s not a stable molecule at room temperature.^ - 61 -0 0 a + 10 H 47 3 2 [ 6 ] 0 0 14 Therefore, i t has to be generated i n s i t u and trapped with the desired 1,4-quinones under the r e a c t i o n conditions required f or i t s preparation. Another important point that has to be taken into account i s the f a c t that ene-dione 47 would be expected to undergo b i s -e n o l i z a t i o n under a c i d i c or basic conditions due to the presence of the enolizable hydrogens at 4a and 9a. This e n o l i z a t i o n can r e s u l t i n the formation of the corresponding hydroquinones which i n turn are r e a d i l y oxidized to f u l l y aromatic hydroquinones. Furthermore, i t has been found by Kametani et ai.30,36-38 t n a t adducts such as 47 and 53 (Scheme 30a) are not stable at temperatures higher than 150°C. Thus, the r e a c t i o n leading to the synthesis of adduct 47 should be c a r r i e d out under neutral conditions below 100°C (to be on the safe s i d e ) . The various methods that have been used to generate o-quinodi-methane have been reviewed i n the Introduction. Of those methods, three that appear to f i t into the category of 'neutral' conditions and 'lower temperatures' are summarized i n the form of equations 7, 8 and 9. (1) Han and Boudjouk Method. 4 9 (2) Ito Method. 5 1' 5 2 (X = NMe3Br) 27 (3) Durst and Charlton Method. 5 8" 6 5 ^ ^ ^ 0 kC0 2CH 3 - S° 2 ^ A ^ C 0 2 C H 3 61 (57%) XO£t f 2 TBA F / P t f N ^ y ^ C O ^ E t ^C02Et R T ^ A C 0 2 E t (46%) 63 (1) Han and Boudjouk Method The synthesis of tetrahydro-1,4-anthracenediones was f i r s t attemp-1 ft ted at U.B.C. by Perkins- 1- 0 using the method developed by Han and Boudjouk.^ I t was found by Perkins that, on treatment of a,a'-dibromo-xylene 60 with zinc under ultrasound conditions, i n the presence of e i t h e r 1,4-benzoquinone or duroquinone, no adducts corresponding to 47 or 52 were formed. Instead a,a'-dibromoxylene 60 was i s o l a t e d unreacted along with the corresponding hydroquinones. The s i t u a t i o n i s shown i n Scheme 31. Perkins explained t h i s difference i n r e a c t i v i t y i n terms 47 R=H 52 R=Me Scheme 31 64 -of involvement of the zinc i n reducing the quinones rather than p a r t i c i -pation i n o-quinodimethane formation. Therefore, t h i s method was abandoned. (2) Ito Method The next r e a c t i o n attempted was the f l u o r i d e ion-catalyzed decompo-s i t i o n of the ammonium s a l t 27. For t h i s purpose [o- [ a -(trimethyl-silyl)methyl)benzyl]trimethylammonium bromide (27) was p r e p a r e d ^ by the sequence of reactions shown i n Scheme 32. A l l the reactions i n Scheme 32 were c a r r i e d out exactly as reported i n the l i t e r a t u r e - ^ except step four which was c a r r i e d out at 0°C i n a round-bottomed f l a s k instead of at 110°C i n a sealed tube as reported by Ito. The d e t a i l s are given i n Scheme 32 - 65 -the Experimental section. The reaction of ammonium s a l t 27 with the following quinones was c a r r i e d out: a) Duroquinone b) 2,3-Dimethyl-1,4-naphthalenedione c) Tetraethyl-l,4-benzoquinone d) 2,5-Dimethyl-1,4-benzoquinone e) 1,4-Benzoquinone (a) Reaction of Ammonium Sa l t 27 with Duroquinone o-Quinodimethane (14) was generated i n s i t u i n the presence of duroquinone by the re a c t i o n of ammonium s a l t 27 with commercial tetrabutylammonium f l u o r i d e (TBAF, a v a i l a b l e from A l d r i c h Chemicals, Milwaukee, Wisconsin) at room temperature i n anhydrous CH3CN. 1 4 5 A f t e r 2.5-3 h on average, the reaction proceeded as expected and the product 52 was i s o l a t e d by f l a s h column chromatography 1 4 6 i n 40-50% y i e l d . The sequence of reactions leading to the formation of adduct 52 i s i l l u s -t r a t e d i n Scheme 33. I t i s c l e a r from Scheme 33 that with every mole of ammonium s a l t 27 reacted, 1 mole of trimethylamine i s also produced. The structure of the adduct 52 was assigned on the basis of the following spectroscopic data: the i r spectrum of t h i s substrate shows a strong peak at 1664 cm"1 and a weak si g n a l at 1610 cm"1, assigned to the C=0 and C=C stretchings r e s p e c t i v e l y of the ene-dione moiety. These values are i n good agreement with the C=0 and C=C stretches of ene-dione 36 147 nmr spectrum features four aromatic hydrogens at S 7.12-7.06 - 66 -as a m u l t i p l e t . The two doublets at 6 3.25 and S 2.55 coupled to one another (J = 17 Hz) are assigned to the two methylene u n i t s . The coupling constant (J «= 17 Hz) i s t y p i c a l of geminal coupling at an sp 3 - h y b r i d i z e d carbon. 1^ °* Due to the average plane of symmetry i n the molecule, the C(2) and C(3) methyl groups appear as a s i n g l e t at 5 1.98 along with a C(4a), C(9a) methyl s i n g l e t at 5 1.22. The nmr assignments of the C(2)/C(3) methyls and C(4a)/C(9a) methyls are made a f t e r comparing the chemical s h i f t s with the nmr of 36.1^0 ^ e average plane of symmetry also explains the enantiotopicity of the C(9) , C(10) methylene hydrogens. The - 67 -mass spectrum displays a molecular ion at m/e 288, and the compound analyzed c o r r e c t l y f o r C^H^nC^* Although the spectroscopic properties b a s i c a l l y confirm the structure, they do not give d e f i n i t i v e information regarding the r e l a t i v e stereochemistry of the methyls at the r i n g junc-t i o n , i . e . whether the methyls C(4a), C(9a) are c i s or trans. The r i n g j u n c t i o n stereochemistry, however, can be understood i n terms of the ' c i s r u l e ' 1 5 1 of the Diels-Alder reaction, i . e . the r e l a t i v e configura-t i o n of the s t a r t i n g materials i s retained i n the adduct. The c i s - r i n g j u n c t i o n stereochemistry, along with the unambiguous proof of the structure of the adduct 52, came from a sin g l e c r y s t a l X-ray d i f f r a c t i o n study c a r r i e d out by Mr. Fred W i r e k o 1 5 2 of Professor James Trotter's group. A l l the other c r y s t a l l o g r a p h i c work presented i n t h i s thesis was c a r r i e d out by Dr. Sara A r i e l 1 5 2 a of the same group. An i n t e r e s t i n g feature of t h i s r e a c t i o n i s that duroquinone reacts at a l l under these mild conditions. This i s remarkable i n view of the high temperature, sealed tube conditions required to bring about the Diels-Alder reaction between duroquinone and 2,3-dimethyl-1,3-butadiene. 1 4 2 This i s presum-ably a testimony to the high r e a c t i v i t y of o-quinodimethane. (b) Reaction of Ammonium Salt 27 with 2.3-Dimethyl-l.4-naphthalenedione A f t e r s u c c e s s f u l l y synthesizing the duroquinone adduct 52, we decided to prepare adduct 54 by the same method. In f a c t , when 2,3-dimethyl-1,4-naphthalenedione, prepared by oxidation of 2,3-dimethyl-naphthalene with CrC>3 1 5 3 (see Experimental section f or d e t a i l s ) , was - 68 -allowed to react with ammonium s a l t 27, under the same reaction conditions as duroquinone, the s u p r a f a c i a l - s u p r a f a c i a l a d d i t i o n ^ ^ D f o-quinodimethane (14) with the dienophile took place to a f f o r d the adduct 54 i n a poor y i e l d as shown i n equation 10. ( X = N M e s B r ) 0 0 27 54 The i r spectrum of the adduct 54 shows a strong C=0 s t r e t c h at 1680 cm'l. The nmr spectrum c l e a r l y demonstrates that the adduct 54 has two aromatic rings, A and B (Fig. 6). Ring A i s expected to show a pattern s i m i l a r to that i n 2,3-dimethyl-l,4-naphthoquinonel-^ and therefore assignments are made accordingly. The doublet of doublets (J = 6 Hz and 3 Hz) at S 8.05 i s assigned to H(l) and H(4), whereas the doublet of doublet (J = 6 Hz and 3 Hz) at « 7.73 i s a t t r i b u t e d to H(2) and H(3). Ring B shows i t s aromatic resonances at S 7.27-7.04, s i m i l a r to the 0 Fig. 6 aromatic hydrogens i n 52. The benzylic hydrogens, as f o r the adduct 52, appear as two doublets (J = 16 Hz) at 5 3.42 and 6 2.65. The two 69 -methyls show a s i n g l e t at S 1.33. The mass spectrum of the substrate 54 has the parent peak at m/e 290, and t h i s compound c o r r e c t l y analyzed for ^20^18u2- F i n a l proof of the c i s - s t r u c t u r e of t h i s compound came from X-ray c r y s t a l l o g r a p h y . 1 5 2 3 (c) Reaction of the Ammonium s a l t 27 with Tetraethvl-1.4-benzoquinone A f t e r preparing adducts 52 and 54, we decided to prepare the adduct 53 using the same method as shown i n equation 11. For t h i s purpose, tetraethyl-1,4-benzoquinone 66 was prepared by well-known methods. 1 5 5 When the Diels-Alder reaction was c a r r i e d out under the same conditions as above, the product i s o l a t e d , to our surprise, was i d e n t i f i e d as spiro-di-o-xylylene 15a, instead of adduct 53. The s p e c t r a l properties of the spiro-dimer 15a were i d e n t i c a l to the published v a l u e s . 2 6 27 66 53 I t i s i n t e r e s t i n g to speculate on the reasons why adduct 53 does not form. This i s probably due to a s t e r i c e f f e c t i n which the bulky et h y l groups prevent o-quinodimethane from approaching the quinone double bond and therefore allows s e l f - d i m e r i z a t i o n of o-quinodimethane - 70 -to compete with the formation of 53. I t i s w e l l - e s t a b l i s h e d ^ ^  that s t e r i c f a c t o r s , e s p e c i a l l y on the dienophile, play a very important role i n D i e l s - A l d e r reactions. Since the dienophile i s hard to approach f o r reaction, o-xylylene i t s e l f undergoes intermolecular [4+2] cyc l o a d d i t i o n g i v i n g the spiro-dimer 15a, as i l l u s t r a t e d i n equation 12. Such a spiro-dimer has already been i s o l a t e d and characterized both by E r r e d e ^ and I t o . 5 1 (d) Reaction of Ammonium Salt 27 with 2.5-Dimethyl-l.4-benzoquinone The next quinone selected f o r re a c t i o n with o-xylylene was 2,5-dimethyl-l,4-benzoquinone (available from A l d r i c h Chemical Co.). Under the same conditions as above, the rea c t i o n afforded a poor y i e l d of adduct 50t as shown i n Scheme 34. The structure of the adduct 50t was confirmed i n the following way. Its i r spectrum shows two carbonyl absorptions at 1680 and 1660 cm"-'-. Its nmr spectrum features aromatic hydrogens at 6 7.21-7.13 as a mul t i p l e t . The broad doublet at 6 6.57 (i n t e g r a t i n g f o r 1H) i s coupled (J = 2 Hz) to the doublet at S 2.06 (i n t e g r a t i n g f o r 3H), i n d i c a t i n g - 71 -the presence of the H-CMS-CH3 group i n the molecule. Thus, these signals are assigned to H(3) and CH3(2), r e s p e c t i v e l y . Unlike the adducts 52 and 54, which are symmetrical and therefore have r e l a t i v e l y simple b e n z y l i c resonances (two doublets i n each case), the adduct 50t shows a m u l t i p l e t at 6 3.21-2.95, since the four benzylic hydrogens are non-equivalent. Moreover, the benzylic hydrogens at H(9) are further coupled to the methine hydrogen at H(9a). The m u l t i p l e t at 5 3.21-2.95 int e g r a t i n g f o r 5H also includes the H(9a) methine hydrogen. The methyl at C(4a) appears as a s i n g l e t at S 1.15. The mass spectrum shows the 72 -parent peak at m/e 240, and the compound analyzed c o r r e c t l y for <-'16^ 16<-)2 • Although spectroscopy confirms the o v e r a l l structure, no information i s obtained about the stereochemistry at C(4a) with respect to C(9a). The t r a n s - r e l a t i o n s h i p at H(9a) r e l a t i v e to the methyl at C(4a) i s confirmed by an independent synthesis of the trans-adduct 50t from the authentic cis-adduct 49c (for the synthesis of the cis-adduct, see page 84) as shown below. 49c 50t Since the Diels-Alder reaction i s known to y i e l d k i n e t i c a l l y favored products with retention of configuration-'- 5 1, i . e . 49c i n the present example, the question a r i s e s , why i s the thermodynamically favored trans-compound formed i n t h i s reaction? Obviously, the trans-isomer must be formed from the cis-adduct 49c under the r e a c t i o n conditions. What factors are responsible for i n s t a b i l i t y of 49c? At t h i s point we r e c a l l that for every mole of the ammonium s a l t 27 reacted, one mole of trimethylamine i s also formed. The base, trimethylamine, present i n the r e a c t i o n mixture i s responsible (along with TBAF, as we l a t e r found out) for converting the k i n e t i c a l l y favored cis-product into the thermodynam-i c a l l y favored trans-isomer. Even though i t was c l e a r that enolizable Di e l s - A l d e r adducts are not stable under the reaction conditions due to - 73 -the presence of trimethylamine (and TBAF), the reac t i o n with p-benzoqui-none was attempted. (e) Reaction of Ammonium Salt 27 with 1,4-Benzoquinone The r e a c t i o n of f r e s h l y sublimed p-benzoquinone with the ammonium s a l t 27 was t r i e d i n the presence of anhydrous TBAF.-^ 0 I t was hoped that the desired b i s - e n o l i z a b l e adduct 47 could be synthesized, as shown i n Scheme 35. However, compound 47 could not be i s o l a t e d ; instead, the product obtained i n 65% y i e l d was i d e n t i f i e d as 1,4-anthracenedione 24a. The mp and spectroscopic properties of 24a compared very well with the reported values^-^ ( s e e Experimental f o r d e t a i l s ) . Another compound Scheme 35 74 -that was also i s o l a t e d i n 35% y i e l d was i d e n t i f i e d as hydroquinone by GC coinj ection. The r e a c t i o n leading to the formation of compound 24a c e r t a i n l y follows the formation of tetrahydro-1,4-anthracenedione 47. One mechanism involves the b i s - e n o l i z a t i o n of 47 under the re a c t i o n conditions and subsequent oxidation to 24a. The e n o l i z a t i o n can be brought about, as discussed e a r l i e r , by trimethylamine generated during the course of the r e a c t i o n (and by TBAF as we l a t e r found out). In order to confirm the idea that b i s - e n o l i z a t i o n by trimethylamine can a c t u a l l y lead to the corresponding hydroquinone, Diels-Alder adduct 37 was p r e p a r e d 1 4 1 by the c y c l o a d d i t i o n of 2,3-dimethyl-l,3-butadiene with p-benzoquinone. On treatment of adduct 37 with triethylamine at room temperature for 1 h, under Ito's reaction c o n d i t i o n s , 5 1 a l l of the adduct 37 was consumed, and the product i s o l a t e d i n 76% y i e l d was i d e n t i f i e d as hydroquinone 67 (equation 13) by i t s known mp 1 5 8 and spectroscopic properties given i n the Experimental section. Thus, the 0 O H Triethylamine MeCN, RT [13] 0 OH 37 6 7 formation of 24a from 47 can be understood as outlined i n Scheme 3 6 . The steps ( i i i ) and (iv) are probably very f a s t under the reaction conditions since no products corresponding to 68 and 68a could be - 75 -i s o l a t e d . C a v a , 2 2 ' 2 3 K a m e t a n i , 3 4 " 3 8 and McOmie 4 4 also i s o l a t e d 24a during the rea c t i o n of o-quinodimethane with p-benzoquinone. The formation of hydroquinone suggests that either step ( i i i ) or (iv) or both are brought about by p-benzoquinone i n an oxidation-reduction reaction. a + 14 + [DA] Oxidation Step i v Step i i i 24a 68a Scheme 36 I t i s c l e a r from the r e s u l t s discussed above that adduct 47 cannot be i s o l a t e d under Ito's reaction conditions due to the formation of a base, trimethylamine. In order to avoid the formation of trimethyla-mine, the nature of the leaving group was changed. For t h i s purpose - 76 -acetate and chloride ions, which are less basic than trimethylamine and are also good leaving groups, were selected. Therefore, the synthesis of acetate 70 and chloride 71 was required. 70 (X=0Ac) 71 (X=CI) Synthesis of Acetate 70 and Chloride 71 RR'R"N + (MeC0) 20 0 MeCNR' R" + 9 MeCOR S i M e 3 X (X=NMe2 ) 65 (MeC0) 20 Si Me, 0 + MeCNMeo [14] (X=0Ac) 70 M a r i e l l a and Brown^-^ have shown that t e r t i a r y amines, on treatment with a c e t i c anhydride at ref l u x , undergo displacement of one of the R groups from the amine as shown above. The groups displaced were benzyl, t - b u t y l , t r i t y l and cinnamyl. Based on the above p r i n c i p l e , i t was thought that amine 65 (Scheme 32) could be used to prepare acetate 70. Indeed, under the same reaction conditions as used by M a r i e l l a and B r o w n , a c e t a t e 70 was obtained i n 77% y i e l d (equation 14). The - 77 -structure of acetate 70 was derived from i t s spectroscopic properties. Its i r spectrum shows a strong C=0 band at 1720 cm"!. The nmr spectrum of t h i s compound i s s i m i l a r to the corresponding spectrum of amine 65. I t features aromatic hydrogens at S 7.34-7.02 and Ar-CH^-OAc at 8 5.08, s l i g h t l y further downfield compared to the ArCH2-NMe2 of 65, which appears at S 3.41. This can be due to the inductive e f f e c t of the acetate group. The s i n g l e t at 5 2.10 i s assigned to the acetate methyl whereas the remaining two s i n g l e t s at 6 2.18 and 6 0.03 are assigned to the other benzylic and t r i m e t h y l s i l y l hydrogens respec-t i v e l y . The mass spectrum and the microanalysis also conform to the assigned structure. The corresponding chloro compound 71 was prepared by the basic hyd r o l y s i s of the acetate followed by replacement of the hydroxyl group by c h l o r i d e as shown below. The spectroscopic properties of compound 71 are given i n the Experimental section. Though the compound 71 was f i r s t prepared by Ito et al.,-'-'- neither the method of i t s synthesis nor i t s spectroscopic data were reported. ( X = 0 A c ) (X = C | ) 70 71 The usefulness of acetate 70 as a diene precursor was demonstrated by c a r r y i n g out the Diels-Alder reaction of duroquinone i n the presence of TBAF and 70. In f a c t , a better y i e l d (61% vs 40-50% by ammonium s a l t 27 method) of the adduct 52 was obtained. However, when p-benzoquinone was used as the dienophile, once again f u l l y aromatized 1,4-anthracene-dione 24a resulted. When the chloro compound 71 was used as the diene-equivalent, and the r e s u l t i n g o-quinodimethane was used with p-benzoquinone as shown below, f u l l y aromatic adduct 24a was also obtained. Since substrates 70 and 71 cannot generate trimethylamine, the e n o l i z a t i o n leading to the formation of 24a must be brought about by Si Me, 70 ( X = 0 A c ) 71 (X=CI) TBAF 24a another species present i n the reaction mixture. Could i t be TBAF? In order to te s t whether the e n o l i z a t i o n can be caused by TBAF, ene-dione 37 prepared e a r l i e r was treated with TBAF under Ito's r e a c t i o n condi-tion s . To our surprise, i t was found that indeed b i s - e n o l i z a t i o n leading to the formation of hydroquinone 67 occurred as given below. TBAF /on The use of f l u o r i d e as a base and nucleophile i s not without prece-dence . ^ ® For example, the reaction of f l u o r i d e ion with 2-chlo-ro-2-methyl-cyclohexanone (69) produces 2-methyl-2-cyclohexenone (69a) and 2-fluoro-2-methylcyclohexenone (69b) (equation 15). CI KF, MeCN 18-Crown-6 > F [15] 69 69a This means that the enolizable adducts of type 47, 48, 49, 51 and 55 (Scheme 30) cannot be prepared by Ito's method 5 1 or any modification of i t . Therefore, some other method(s), which can be c a r r i e d out under neutral conditions, must be used. (3) D u r s t and Charlton Method C O r9 £ Q Durst and C h a r l t o n J ° • D i > O J have shown that s u l t i n e 61 undergoes a r e t r o - c h e l o t r o p i c r e a c t i o n by eliminating SO2 at 80° to give o-quinodimethane 14, which undergoes smooth Diels-Alder reactions with various dienophiles. A representative example i s shown i n Equation 9. 6 1 (57%) - 80 For t h i s purpose, s u l t i n e 61 was prepared by the sequence of reac-t i o n s - ^ ! 63 s h o w n £ n Scheme 37. 61a 1. NaOH/MeOH 2. NaBH. ' 4 3. Cone. HC1 61 0 I Scheme 37 R e a c t i o n s o f S u l t i n e 61 w i t h p - Q u i n o n e s (a) With p-Benzoquinone Under the re a c t i o n conditions u t i l i z e d by Durst and Charlton, ,63 a s o l u t i o n of s u l t i n e 61 i n benzene was refluxed i n the presence of f r e s h l y sublimed p-benzoquinone for 2 h. The solvent was removed i n vacuo and the remaining yellowish s o l i d was r e c r y s t a l l i z e d from MeOH to a f f o r d large needle-shaped, almost c o l o r l e s s c r y s t a l s of the desired adduct 47 i n 48% y i e l d . 1°" The structure of substrate 47 was v e r i f i e d by spectroscopy as follows: Its i r spectrum has a strong C=0 band at 1680 cm"l expected f o r the ene-dione group. The nmr spectrum shows a mu l t i p l e t at 6 7.18-7.06 int e g r a t i n g f o r 4H, assigned to the aromatic hydrogens. The chemical s h i f t of the s i n g l e t at 5 6.72 in t e g r a t i n g f o r 2H i s assigned to the v i n y l i c hydrogens a f t e r comparing i t with the 81 -0 oc - S 0 2 A [16] 0 61 corresponding hydrogen s h i f t s of 37, which appeared at 6 6.75. 1 6 1 The m u l t i p l e t i n t e g r a t i n g f or 2H at S 3.40 i s assigned to the hydrogens at 4a and 9a. The four benzylic hydrogens at 5 3.22 and S 2.92 appear as a doublet of doublets with coupling constant of 18 Hz and 6 Hz and 18 Hz and 4 Hz r e s p e c t i v e l y . The two doublets of doublets are expected because the two geminal methylene hydrogens are diastereotopic; each i s coupled to the other and both of them are independently coupled to the methine hydrogens. Thus the methine hydrogens, which should at l e a s t be two doublets, appear as m u l t i p l e t . The mass s p e c t r a l and elemental analyses support the molecular formula of C14H12O2. The adduct 47, though i t can be synthesized by the method given i n equation 16, i s generally very unstable i n polar solvents. I t must be r e c r y s t a l l i z e d very quickly i n the dark. Furthermore, the f l a s k i n which the a d d i t i o n r e a c t i o n i s being c a r r i e d out must be covered with aluminum f o i l . These comments are also true f o r the b i s - e n o l i z a b l e adducts 48 and 55 (Scheme 30). I f these precautions are not taken, a black r e a c t i o n mixture i s obtained from which i s o l a t i o n of the desired adduct cannot be achieved. - 82 -(b) Reaction of Sultine 61 with 2-Methyl-1.4-benzoquinone A f t e r successful synthesis of the adduct 47, we decided to use the same method to prepare the toluquinone adduct 48. For t h i s purpose, f r e s h l y sublimed toluquinone (available from A l d r i c h Chemical Co.) was prepared and the c y c l o a d d i t i o n r e a c t i o n proceeded as expected to give adduct 48 i n 60% y i e l d (equation 17). The compound 48, l i k e i t s predecessor 47, was characterized by spectroscopy. I t s i r spectrum features two strong carbonyl peaks at 1690 and 1675 cm"l, unlike adduct 47 which shows only one C=0 stret c h . I t also shows a r e l a t i v e l y weak peak at 1620 cnT^ due to C=C, a range i n good agreement with the l i t e r a t u r e v a l u e . ^ h e nmr spectrum of t h i s compound i s rather more complex compared to the symmetrical adduct 47, since the molecular symmetry does not e x i s t i n t h i s case and therefore i n p r i n c i p l e , no two hydrogens (except those on the methyl group) are magnetically equivalent. The aromatic hydrogen m u l t i p l e t appears at 5 7.15-7.06. A quartet at 8 6.58 ( i n t e g r t a t i o n 1H) i s coupled (J = 2 Hz) to the doublet at 8 2.02 ( i n t e g r a t i o n 3H) , c h a r a c t e r i s t i c ^ 0 " Q f the H-C=C-CH3 u n i t i n the molecule. The remaining a l i p h a t i c hydrogens appear i n the form of three groups of mu l t i p l e t s at 8 3.37, 8 3.20 and 8 - 83 2.92 of 2H each. The mu l t i p l e t at 6 3.37 i s assigned to the 4a and 9a methines a f t e r comparing i t with the chemical s h i f t of 33 (5 3 . 3 5 ) 1 6 1 , as well as with that of 47 (5 3.40). The remaining four benzylic hydrogens resonate at S 3.20 and 8 2.92. The mass spectrum and elemental analysis also agree f o r ^\^\ifi2. (c) Reaction of Sultine 61 with 1.4-Naphthalenedione The r e a c t i o n of f r e s h l y sublimed and r e c r y s t a l l i z e d 1,4-naphthalene-dione ( a v a i l a b l e from A l d r i c h Chemical Co.) with s u l t i n e 61 proceeded smoothly to a f f o r d b i s - e n o l i z a b l e adduct 55 i n 52% y i e l d [equation 18]. The i r spectrum features a strong peak at 1680 cm'1, c h a r a c t e r i s t i c of the C=0 s t r e t c h of a,^-unsaturated k e t o n e s . 1 5 8 The nmr of the adduct i s assigned by comparing i t with the nmr .spectrum of 1,4-naphthalene-d i o n e 1 5 4 and also with the nmr of 54 (page 68). The aromatic r i n g A shows two doublet of doublets (J = 6 Hz and 3 Hz) at S 8.08 and 5 7.75 in t e g r a t i n g f o r 2H each; these are assigned to H ( l ) , H(4) and H(2), H(3) res p e c t i v e l y . The aromatic r i n g B, which integrates f o r 4 protons, - 84 -appears as a m u l t i p l e t at 6 7.17-7.07. The methine hydrogens show a m u l t i p l e t at 6 3.57 i n t e g r a t i n g f o r 2H, whereas the be n z y l i c hydrogens appear as doublet of doublets at S 3.30 and S 2.99. The two doublet of doublets show secondary (unassigned) weak couplings (J = 1-2 Hz). The mass s p e c t r a l analysis shows a parent ion at m/e 262, and the compound analyzed c o r r e c t l y f o r C^gH^^^. (d) Reaction of Sultine 61 with 2.5-Dimethyl-1.4-benzoquinone The r e a c t i o n of 2,5-dimethyl-1,4-benzoquinone ( a v a i l a b l e from A l d r i c h Chemical Co.) with a r e f l u x i n g s o l u t i o n of s u l t i n e 61 i n benzene i s shown i n equation 19. As expected, the r e a c t i o n afforded a 62% y i e l d of the tetrahydro-1,4-anthracenedione 49c i n the form of b e a u t i f u l c r y s t a l s . Unlike adducts 47, 48 and 55 (Scheme 30), which are quite unstable, due to t h e i r tendency to undergo b i s - e n o l i z a t i o n i n methanol and other polar solvents, the adduct 49c i s quite stable. The structure of the adduct 49c i s based upon the following spectroscopic data: the i r spectrum of t h i s substrate shows a strong, broad (more l i k e two peaks - 85 -which are barely separated) C=0 peak at 1680 cm"-'-. Once again, the C=C str e t c h i s also very d i s t i n c t and appears at 1620 cm"-'-. The nmr spectrum, given i n F i g . 7, i s very i n t e r e s t i n g and informative, espe-c i a l l y i n the a l i p h a t i c region. I t features aromatic m u l t i p l e t s at 8 7.17-7.00 and a v i n y l i c quartet (3H) coupled (J = 1.5 Hz) to the v i n y l methyl doublet (1H) at 2.00 ppm. The a l l y l i c coupling with J = 1.5 Hz i s i n d i c a t i v e of the H-C=C-CH3 group i n the molecule. The chemical s h i f t of the 4a methyl group compares favorably with the 4a methyl s i n g l e t of ene-dione 52. The two doublets of doublets at 8 3.38 and 2.39 with coupling constants (J) of 17 Hz, 6 Hz, and 17 Hz, 5 Hz are due to the ben z y l i c hydrogens at H9. Doublets of doublets are observed because the two diastereomeric methylene hydrogens are coupled to one F i g . 7 : A 400 MHz -4* NMR Spectrum of Adduct 49c 86 -another (J = 17 Hz) and to the methine hydrogen (J = 6 Hz and 5 Hz). Since the coupling constants (J = 6 Hz and 5 Hz) of the C(9) benzylic hydrogens to the methine hydrogen are very s i m i l a r , H4a appears as a fortuituous t r i p l e t at 6" 3.06. The remaining two doublets, which are coupled to one another (J = 16 Hz), are due to the diastereomeric methylene protons at H10. The assigned structure i s also supported by the mass spectrum, which displays the M + peak at m/e 240, and the compound analyses c o r r e c t l y f o r C-L^IS0!- F i n a l proof of the structure of the adduct 49c comes from X-ray crystallography.152a I t was noted that the 2,5-dimethyl-l,4-benzoquinone adduct 50t prepared by Ito's method (Scheme 34) had d i f f e r e n t spectroscopic proper-t i e s and mp than the 2,5-dimethyl-l,4-benzoquinone adduct 49c prepared by the Durst and Charlton method. Since the cis-stereochemistry at the r i n g j u n c t i o n of 49c has been established unequivocally, i t was l o g i c a l to assume that 50t must be the trans-adduct. In order to prove the r i n g j u n c t i o n stereochemistry of 5 0 t , the cis-adduct 49c was treated with triethylamine with the expectation that the thermodynamically more stable trans-adduct 50t would be obtained. In f a c t , when a CH3CN s o l u t i o n of 49c was treated with triethylamine (1.0 equivalent) for 4 h at room temperature, a l l of the 49c was consumed, and the product i s o l a t e d had the same mp and i r spectrum as 50t i s o l a t e d e a r l i e r (see page 7 1 ) . 1 8 87 (e) Reaction of Sultine 61 with 2.3.5-Trimethvl-1.4-benzoquinone Decomposition of the s u l t i n e 61 i n b o i l i n g benzene i n the presence of 2,3,5-trimethyl-1,4-benzoquinone (prepared by oxidation of 2,3,5-tri-methylhydroquinone with C r C ^ ) 1 6 2 y i e l d e d adduct 51 i n 52% y i e l d (equation 20). The structure of adduct 51 was derived i n the following way: the i r spectrum of th i s compound has a strong C=0 s t r e t c h and a r e l a t i v e l y weak C=C peak at 1671 cm"1 and 1621 cm"1, r e s p e c t i v e l y . The nmr s p e c t r a l pattern of t h i s compound i s very s i m i l a r to that of 49c, as expected, with some di f f e r e n c e s . Ene-dione 51 displayed two methyl s i n g l e t s at 8 2.00 and 8 1.98 and d i d not show a v i n y l hydrogen quartet 88 -at 5 6.52. The remaining nmr signals and t h e i r assignments are i d e n t i c a l to 49c and therefore, w i l l not be discussed here. The mass spectrum shows the parent ion at m/e 254, and the microanalysis supports the molecular formula C17H13O2. F i n a l proof of the structure came from X-ray d i f f r a c t i o n study.152a - 89 -PART II SYNTHESIS OF ANTHRAQUINOLS (a) Synthesis of Enones 56B and 57A These two compounds were prepared by the reduction of ene-dione 52 with NaBH^ as shown i n equation 22. The same borohydride reduction has been used by Scheffer et a l . ^ - * (equation 21) to synthesize enones 46B and 46A. The r e s u l t s obtained can be j u s t i f i e d i n terms of Baldwin's •I r "3 r u l e . 0 - * According to t h i s r u l e , f o r an a,0-unsaturated ketone, two resonance structures (a) and (b) must be considered with the d i r e c t i o n of approach vector of the nucleophile as shown i n F i g . 8 with weights - 90 -C^>C2- A summation of these vectors gives a r e s u l t a n t approach vector as shown i n ( c ) . This analysis indicates that the approach vector for n u c l e o p h i l i c attack at a carbonyl function i s s h i f t e d from the symmetric d i s p o s i t i o n as i n ketone (a) to a p o s i t i o n i n space close to the residue 'x'. In t h i s approximate treatment, the angle subtended to the plane of the carbonyl function by the resultant approach vector i s taken to be 110°. The stereochemistry of reduction, therefore, i s c o n t r o l l e d by the q u a s i - a x i a l substituents at C(6) and C(5). Those at C(4) have l i t t l e e f f e c t on the stereochemistry of reduction. The weightings of substitu-ents i n t h e i r r e l a t i v e e f f e c t s are: and 6 q u a s i - a x i a l Me > 6 q u a s i - a x i a l H > 5 q u a s i - a x i a l H 5 q u a s i - a x i a l Me > 6 q u a s i - a x i a l H. - 91 -We applied t h i s concept to the reduction of ene-dione 52 (equation 22) as shown below. In structure (d), the qu a s i - a x i a l substituent at C(6) i s a methyl group and at C(5) i s a methylene. Because of the r e l a t i v e l y small s i z e of a methylene group compared to methyl, hydride ion attack i s impeded from the methyl side of structure (d) and therefore, 57A becomes the minor product (equation 22). The analysis given above implies that the b u l k i e r group at C(6) or C(5) controls the outcome of the reaction. The above analysis i s also consistent with the observations made by Scheffer et al.1^0 d u r i n g the reduction of ene-dione 34 shown below. In t h i s 0 o 34 - 92 case the b u l k i e r group i s methylene and not the hydrogen. Therefore, hydride ion attack takes place e x c l u s i v e l y from the hydrogen side of the carbonyl group. This attack r e s u l t s i n the dominance of the product having the stereochemistry opposite to that observed f o r the reduction of 52. The structure of enone 57A i s ind i c a t e d by i t s i r spectrum, fe a t u r i n g a hydroxyl band at 3484 cm"1, a carbonyl band at 1647 cm"1 and a carbon-carbon double bond at 1632 cm"1. These values are i n good agreement with the i r spectrum of 46A (equation 2 1 ) . 1 1 5 The nmr spectrum of enone 57A i s given i n F i g . 9. The m u l t i p l e t ( i n t e g r a t i o n 4H) at 8 7.15-6.94 i s assigned to the aromatic protons. The doublet ( i n t e g r a t i o n 1H) at 6" 4.42 i s coupled (J = 6 Hz) to the OH doublet at 8 F i g . 9: A 400 MHz nmr spectrum of enone 57A 93 2.25. This coupling r e l a t i o n s h i p i s confirmed by deuterium exchange, a f t e r which the doublet at S 2.25 disappears and the doublet at 6 4.42 collapses to a s i n g l e t , thereby confirming the existence of the -CHOH group i n t h i s compound. Accordingly, the peak at 5 4.42 i s assigned to the C(4) hydrogen. The nmr spectrum also shows four doublets (J = 18 Hz) at S 3.10, 3.05, 2.56 and 2.44 due to two groups of two non-equivalent geminal benzylic hydrogens. Four doublets, instead of two as observed f o r the parent compound 52, r e f l e c t the lack of symmetry present i n 57A. The C(3) methyl s i n g l e t at 6 2.00 and the C(2) methyl-singlet at 5 1.77 are assigned a f t e r comparing t h e i r chemical s h i f t s with the corresponding signals of 46A. The two quaternary methyl groups appear as s i n g l e t s at S 1.16 and 5 1.14. The mass s p e c t r a l parent peak at m/e 270 and a correct microanalysis f o r C^gH2202 a i s o support the structure. However, none of the above experimental data give any information about the C(4) stereochemistry. This was obtained from X-ray crystallography, which shows the anti-stereochemistry, i . e . , the OH group i s a n t i with respect to the C(4a) methyl group. In the same way as above, the s t r u c t u r a l assignment of the major enone 56B was also made a f t e r comparing i t with enone 46B.H-* j n e ^ r s p e c t r a l stretches at 3484, 1651, and 1629 cm"l are due to hydroxyl, carbonyl and C=C groups r e s p e c t i v e l y . The nmr spectrum i s very s i m i l a r to that of 57A, and the assignments are made accordingly ( d e t a i l s i n the Experimental s e c t i o n ) . Once again, spectroscopy does not give any information about the stereochemistry at C(4). However, t h i s informa-t i o n i s obtained i n the following way: 1. Since the stereochemistry of one of the two possible epimers has 94 -already been assigned unequivocally by X-ray crystallography, the only other possible epimer must have OH c i s to the C(4a) methyl. 2. During the course of photolysis (see page 186). the photoproduct formed from 56B undergoes hemiketal formation. Hemiketal formation i s only p o s s i b l e ^ - ' when the OH i s c i s to the methyl at C(4a) . 3. An acetate d e r i v a t i v e of 56B, (58B, see below) was analyzed by X-ray crystallography and found to have the c i s - r e l a t i o n s h i p between the C(4a) methyl group and the C(4) acetate. A l l the above arguments and observations leave no doubt that the con f i g u r a t i o n at C(4) i s such that the OH group i s c i s to the methyl at C(4a) i n 56B. (b) Synthesis of Acetate 58B The d e r i v a t i v e 58B was synthesized by the same method used by Walshl^O t o prepare the corresponding acetate from alcohol 46B (equation 21). Thus, when a s o l u t i o n of enone 56B i n a c e t i c anhydride was s t i r r e d with pyridine, acetate 58B was obtained i n 93% y i e l d . The rea c t i o n i s shown i n equation 23. CCfr OH 56B Acetic anhydrid Pyridine OAc 58B - 95 -The i r spectrum of acetate 58B features, i n a d d i t i o n to the normal strong C=0 s t r e t c h at 1665 and a weak C=C s t r e t c h at 1641 cm"1, a strong band at 1742 cm"1 assigned to the acetate carbonyl. The nmr spectrum has aromatic resonances at 5 7.22-6.92, whereas the methine s i n g l e t appears at 6 5.65. This downfield chemical s h i f t of the methine s i n g l e t at S 5.65 compared to the 6 4.31 chemical s h i f t of the parent enone 56B can be understood i n terms of the r e l a t i v e l y greater inductive e f f e c t of the acetate group compared to the hydroxyl g r o u p . 1 4 8 The benzylic hydrogens feature a doublet at 5 3.25 (J = 18 Hz) and a m u l t i p l e t at S 2.57 i n t e g r a t i n g f or four protons. The s i n g l e t at S 2.18 i s t e n t a t i v e l y assigned to the acetate methyl a f t e r comparing i t with the nmr of ethyl acetate (6 2 . 0 5 ) . 1 6 4 A f o r t u i t o u s s i n g l e t , i n t e g r a t i n g f or 6H, at 6 1.83 i s assigned to the C(3) and C(2) methyls, whereas the C(4a) and C(9a) methyls show s i n g l e t s at S 1.23 and 6 1.02. A mass spectrum and microanalysis for C20 H24°3 a l s o support the assigned structure. F i n a l proof of the structure of t h i s compound came from sin g l e c r y s t a l X-ray c r y s t a l l o g r a p h y 1 5 2 3 supporting the c i s - r e l a t i o n s h i p of the C(4a) methyl and C(4a) acetate. (c) Synthesis of Enone 59A Based on a report by W a l s h 1 1 5 that ene-dione 36 can be a l k y l a t e d s e l e c t i v e l y with one equivalent of methyl l i t h i u m to give almost exclu-s i v e l y one epimeric enone, (equation 24), i t was thought that the same method could be used to prepare enone 59A. In f a c t , when a THF s o l u t i o n 96 of the ene-dione 52 (shown below) was treated at -78°C with methyl lithiu m , enone 59A was i s o l a t e d i n 62% y i e l d (equation 25). Although 59A was the only product that could be i s o l a t e d , there were ind i c a t i o n s GC Y i e l d 80% 20% that small amount of epimer 59B also formed. For example, GC analysis c l e a r l y showed two peaks i n a r a t i o of 80:20 for 59A and 59B. A c a r e f u l l y done long path t i c (about 6" long) showed two spots that were barely separated, and a 400 MHz nmr spectrum of the crude reaction mixture contained a d d i t i o n a l peaks that could not be accounted for by 59A alone. F i n a l l y , when a nearly 50:50 mixture of 59A and 59B was treated with d i l u t e HC1, complete dehydration leading to the formation of dienone 72 took place, further confirming that both epimers were present i n the mixture. This l a s t point, and the structure of the product formed, w i l l be discussed l a t e r on. 97 Predominant formation of 59A can be understood i n terms of Baldwin's r u l e ^ ^ discussed e a r l i e r (see page 89). Due to the r e l a -t i v e l y larger s i z e of the methyl anion compared to the hydride ion, the approach of the nucleophile to the carbonyl group i s further impeded from the methyl side r e s u l t i n g i n a dominance of 59A (equation 25). The enone 59A i s quite d i f f i c u l t to p u r i f y because i t cannot be separated from i t s epimer 59B by column chromatography. Af t e r much experimentation, however, i t was found that 59A could be r e c r y s t a l l i z e d from the mixture i n the form of large prisms using acetone as a solvent. The structure of the enone 59A was elucidated i n the following way. Its i r spectrum features strong OH and C=0 stretches at 3498 and 1655 cm"! r e s p e c t i v e l y and a weak C=C peak at 1635 cm"^. The nmr spectrum of t h i s compound shows the presence of aromatic hydrogens at 6 7.17-6.92, a be n z y l i c hydrogen doublet (J = 18 Hz) at 6" 3.22 and a m u l t i p l e t f or 3H at 5 2.58. The f i v e methyl groups appear at 6 2.00 (C(3)CH 3), 6 1.70, 6 1.36, 6 1.26 and 5 1.06. Due to the poor s o l u b i l i t y of the compound i n common nmr solvents which have no signals that overlap with the reso-nance of enone 59A, no s a t i s f a c t o r y s i n g l e nmr spectrum could be obtained. In CDCI3, however, the substrate was soluble, but i t underwent immediate dehydration leading to a mixture of compounds. The dehydration i s probably due to traces of HC1 present i n the CDCI3. The enone 59A, l i k e a l l the other compounds synthesized so f a r , gave the correct mass s p e c t r a l molecular ion peak and microanalysis. A l l the spectroscopic data given above do not provide any informa-t i o n about the configuration at C(4). This information, along with the f i n a l proof of the structure of the enone: 59A, came from sin g l e c r y s t a l - 98 -X-ray crystallography. I t c l e a r l y demonstrates that the OH group at C(4) i s c i s to the C(4a) methyl group. When complete, the reaction of methyl l i t h i u m with ene-dione 52 (equation 25) i s quenched with ei t h e r excess water or a d i l u t e s o l u t i o n of ammonium chlo r i d e , and then 59A i s i s o l a t e d . During the course of reaction, i t was found that i f the reaction mixture i s quenched with d i l . HCl instead of water or ammonium chlo r i d e , no products correspond-ing to 59A or 59B were i s o l a t e d . Instead, the sole product i s o l a t e d was i d e n t i f i e d as dienone 72. HCl - H 20 5 9 7 2 The i r spectrum of 72 featured strong, rather broad stretches at 1655, 1635 and 1597 cm"1. The i r peak at 1655 cm"1 was assigned to C=0, whereas the stretches at 1635 and 1597 were assigned to the C=C of the diene. The nuclear magnetic resonance spectrum was rather i n t e r e s t i n g . Apart from aromatic mul t i p l e t s and four d i s t i n c t l y d i f f e r e n t methyl s i n g l e t s , i t featured four doublets f o r the benzylic hydrogens with coupling constants of 18 Hz each. The four methylene hydrogen doublets were expected because of the lack of symmetry i n the molecule. Probably the most c r u c i a l clue to the structure of dienone 72 came from the two s i n g l e t s at 8 5.43 and 6 5.35, which integrated for 1H each, an i n d i c a t i o n of the presence of a conjugated exo-methylene - 99 -g r o u p . I t was i n t e r e s t i n g to note that t h i s molecule possessed two kinds of methylene hydrogens, benzylic and v i n y l i c . While the former showed two doublets each, the l a t t e r displayed two s i n g l e t s . Why? The answer to t h i s question came from the Karplus equation for geminal coupling ( Fig. 1 0 ) . A c c o r d i n g to t h i s graph, i t i s c l e a r that the geminal coupling constant (J) depends on the H-C-H angle. I f the H-C-H angle i s -120° (exo-methylene) the coupling becomes too small to be observed, whereas i f the angle i s 109° (sp^ methylenes), a coupling constant of 15-18 Hz i s observed. The high r e s o l u t i o n mass spectrum supports the molecular formula C-^gU22^2-Degrees F i g . 10: The geminal Karplus c o r r e l a t i o n s . ^H-H ^ o r ^ 2 g r o u P s a s a function of H-C-H a n g l e . 1 4 8 - 100 -One reason why compound 59A undergoes e f f i c i e n t dehydration and 57A or 56B do not, i s that 57A and 56B are secondary alcohols, whereas 59A i s a t e r t i a r y alcohol. T e r t i a r y alcohols are known 1 0 0 to undergo f a c i l e dehydration to y i e l d alkenes. Similar observations of dehydration were also made by Scheffer et a l . l D ^ when enone 46 was treated with p-toluenesulfonic acid. - 101 -CHAPTER 2 PHOTOCHEMISTRY OF ENE-DIONES In the present research work, a t o t a l of eight ene-dione type compounds has been studied, both i n the s o l i d state and i n s o l u t i o n . S p e c i f i c reasons f o r the choice of each compound w i l l be discussed as i t comes along. The compounds have been regrouped depending on t h e i r r e a c t i v i t y i n the s o l i d state with respect to s o l u t i o n . Thus, three d i f f e r e n t kinds of r e a c t i v i t i e s were noticed. They are as follows: (a) Ene-diones that behave s i m i l a r l y i n the s o l i d state and s o l u t i o n . (b) Ene-diones that react d i f f e r e n t l y i n the s o l i d state and s o l u t i o n . (c) Ene-diones that only react i n s o l u t i o n and not i n the s o l i d state. (a) Ene-diones That Behave S i m i l a r l y i n the S o l i d State and Solution ( i ) Photochemistry of 2.4a-Dimethvl-cis-4a.9a.9.10-tetrahydro-1.4- anthracenedione (49c) 0 0 49c IUPAC numbering Numbering used here to describe photochemistry - 102 -As mentioned before, Scheffer et a l . ' - 5 have shown that symmetrical ene-diones can e x i s t i n two conformations c a l l e d A and B shown i n F i g . 2. In these "twist" conformations, bridgehead groups are staggered with an average t o r s i o n angle of 60° about the C(4a)-C(8a) bond. The h a l f chair cyclohexene moiety i s c i s - f u s e d to the more nearly planar cyclo-hex-2-en-l,4-dione r i n g . H a l f - c h a i r h a l f - c h a i r r i n g i n v e r s i o n leads to interconversion of twist conformations A and B. The symmetrically substituted ene-diones have equal energy i n conformations A and B and are enantiomers. Both conformers are present i n s t a t i c form i n the s o l i d state, and are i n ra p i d equilibrium i n so l u t i o n , of course. I t was thought that the s i t u a t i o n with unsymmetrically substituted ene-diones could be very d i f f e r e n t . In t h i s case conformers A and B are no longer enantiomeric, but are diastereomeric, and therefore A and B do not have equal energy. Thus, i t may be possible by p l a c i n g d i f f e r e n t groups at, for example, positions 4a and 8a, to s p e c i f i c a l l y obtain conformer A or B i n the s o l i d state. Most l i k e l y the conformer which has the lowest conformational energy w i l l be present i n the s o l i d A B F i g . 2 - 103 -s t a t e . A f t e r t h i s project began, s i m i l a r work from our laboratory confirmed t h i s idea, and the r e s u l t s have been p u b l i s h e d . 1 0 ^ I t was found that unsymmetrically substituted ene-dione 7 3 c r y s t a l l i z e d s o l e l y i n conformation A (Fig. 11) due to the preference of the b u l k i e r ethyl group at C(4a) to adopt the less hindered pseudo-equatorial p o s i t i o n with respect to the cyclohexene r i n g . The discussion of the photo-chemistry of ene-dione 7 3 i s deferred u n t i l the next section. 73 Pseudo equatorial exclusive s o l i d state conformation Pseudo-axial 73 F i g . 11 Photochemistry The i r r a d i a t i o n (N 2 l a s e r , A = 337 nm) of ene-dione 49c, both i n a KBr p e l l e t at room temperature and as a pure s o l i d at room temperature as well as at 0°C (to avoid melting), gave cyclobutanone 49CB (equation 26) as the only product. The structure of the photoproduct formed was confirmed by spectroscopic data. I t s i r spectrum features absorptions at 1765 and 1715 cm"-'-, c h a r a c t e r i s t i c 1 ^ of four-membered and s i x -104 -4 9 c 49CB membered ketones r e s p e c t i v e l y . The nmr assignments are made a f t e r comparision with the nmr of 36CB 1 1 and 52CB. The structure of 52CB i n turn i s confirmed by sing l e c r y s t a l X-ray crystallography. -^0 (The photochemical reactions leading to the formation of 52CB w i l l be 36CB 52CB discussed l a t e r ) . The aromatic mu l t i p l e t s of 49CB i n t e g r a t i n g f o r 4H appear at 6 7.27-7.07. Two doublets coupled (J = 6 Hz) to one another ( i n t e g r a t i o n 1H each) at 6 3.36 and S 3.20 are assigned to the hydrogens at C(2) and C(l) or v i c e versa. An AB quartet at 6 2.78 (J = 16 Hz) i s assigned to the C(5) methylenes a f t e r comparing the chemical s h i f t (5 2.80) of the corresponding hydrogens i n 52CB. The C(8) methylene hydrogens also display an AB quartet (J = 18 Hz) at 6 2.39. The l i t e r a t u r e 1 4 ^ value of a methylene u n i t next to a carbonyl group i s 6 2.40. The remaining two s i n g l e t s at 5 1.32 and 5 1.23 are assigned to - 105 -the two methyl groups i n the molecule. The mass spectrum and microa-analysis also support the structure. Ene-dione 49c was also photolyzed (450 W lamp, X > 290 nm) i n a c e t o n i t r i l e at room temperature. The photoproduct i s o l a t e d was the same as i n the s o l i d state. S o l i d State Conformation of 49c In order to understand the r e a c t i v i t y of ene-dione 49c i n the s o l i d state, i t s X-ray c r y s t a l structure was determined. The X-ray c r y s t a l structure a n a l y s i s 1 7 ^ * revealed that ene-dione 49c c r y s t a l i z e s i n conformation A (depicted i n F i g . 12), i n which the bulky methyl group i s pseudo-equatorial to the cyclohexene r i n g . The free energy difference between conformers A and B that have a sin g l e methyl group at C(4a) or C(8a) has been estimated to be 0.5 kcal/mole. This estimate i s based on the a x i a l / e q u a t o r i a l free energy difference f o r a C(4) methyl group i n cyclohexene (1 k c a l / m o l e ) 1 7 2 minus the a x i a l / e q u a t o r i a l free energy di f f e r e n c e f o r a C(5) methyl group i n cyclohex-2-ene-l,4-dione (unknown 0 A F i g . 20 - 106 -but assumed to be 0.5 kcal/mole). X-ray crystallography also revealed that, l i k e s i m i l a r compounds studied before by the UBC photochemistry g r o u p , 7 2 ' 7 3 49c has a twist conformation. This conformation i s i d e a l l y s u i t e d f o r hydrogen [H(82)] atom abstraction by ene-dione carbon. In t h i s conformation H(82) l i e s close to the ene-dione C=C double bond. The various geometric parameters required for hydrogen atom abstraction are discussed i n Chapter 5. Thus, the mechanism of the rearrangement, both i n the s o l i d state as well as i n s o l u t i o n , can be understood. Assuming that the ene-dione 49c adopts the same conformation i n s o l u t i o n as i n the s o l i d state (a s i m i l a r assumption has already been made by Scheffer et a l . 7 2 , 7 3 to explain the s o l u t i o n photochemistry of ene-diones discussed i n the Introduction) the reaction proceeds by abstrac-t i o n of an endo-benzylic hydrogen H(82) by C(3) through a six-membered t r a n s i t i o n state to give C(2) and C(8) b i r a d i c a l 49BR. The b i r a d i c a l centers then combine to give cyclobutanone 49CB. The s i t u a t i o n i s summarized i n Scheme 38. Since a r a p i d equilibrium between conformers A and B i s expected to be present i n s o l u t i o n as shown i n Scheme 38, of the two possible photoproducts, 49CB and 4 9 C B ', why i s only 49CB observed i n solution? We suggest that there are two reasons for t h i s . F i r s t , conformer A i s very l i k e l y the major conformer i n solu t i o n , and a l l other factors being equal, should y i e l d the major photoproduct. The second reason, which i s probably more important, i s explained by the mechanisms shown i n Scheme 38. A f t e r hydrogen atom abstraction, b i r a d i c a l s 49BR and 49BR' are formed, and since 49BR has a more stable t e r t i a r y r a d i c a l center compared to the secondary r a d i c a l center i n 49BR', the former i s - 107 -49c B Exclusive s o l i d state conformation Path I Path II Hydrogen atom abstraction Hydrogen atom abstraction 4; , r f ) \ by c(3) h l / y C { Z ) 49BR 4 9 B R C(2)--C(8) bonding C(3)--C(5) bonding 4 9 C B 4 9 C B Scheme 38 - 108 -pr e f e r r e d and gives the major photoproduct. These arguments imply that i f an unsymmetrical ene-dione such as 51 (Scheme 40) i s photolyzed, where the s t a b i l i t y of the r a d i c a l s formed i s i d e n t i c a l , the products from both conformers w i l l r e s u l t . We have done exactly that by studying the photochemistry of the adduct 51 (see page 115). The importance of the s t a b i l i t y of the b i r a d i c a l s formed v i a the two routes of Scheme 38 i s further emphasized during the photolysis of unsymmetrical ene-dione 73. As ou t l i n e d i n Scheme 39a, i r r a d i a t i o n of ene-dione 73 i n s o l u t i o n y i e l d s two enone-alcohol type photoproducts (73EA and 73EA') and two cyclobutanone type photoproducts (73CB and 73CB'). Since s t a b i l i t y of the b i r a d i c a l s formed i s i d e n t i c a l , a l l the four products r e s u l t . In contrast, photolysis of c r y s t a l s of 73 gives a s i n g l e photoproduct, enone-alcohol 73EA. The explanation f o r the 73EA 73CB 73EA' 73CB' Scheme 39a - 109 -s o l u t i o n photochemical r e s u l t s i s simple: both conformers 73A and 73B are present i n s o l u t i o n , therefore products from both conformers a r i s e . In the c r y s t a l , only one conformer i s present, and i r r a d i a t i o n leads to enone-alcohol 73EA. The lack of formation of the cyclobutanone type photoproduct 73CB, i s explained i n terms of an unfavorable s o l i d state s t e r i c e f f e c t accompanying attempted cyclobutanone formation. The authors suggest that the " s t e r i c compression" retards the rate of the f i r s t step of cyclobutanone formation (transfer of H(5) to C(2)). The " s t e r i c compression" which develops i s shown by the dotted l i n e s i n F i g . 13. I t involves two unfavorable intramolecular methyl-methyl interac-tions between the downward-moving C(2) methyl group and i t s neighboring eth y l groups. This observation of s t e r i c compression i s supported by computer simulated c a l c u l a t i o n s during the p y r i m i d a l i z a t i o n of C(2) i n the s o l i d s t a t e . 1 6 9 Since i n solu t i o n , no such s t e r i c compression e x i s t s , a l l four expected photoproducts are obtained. F i g . 13 Scheffer et a l . 1 ' have also reported /9-hydrogen atom abstraction by oxygen i n the s o l i d state and s o l u t i o n . For example, ene-dione 36 - 110 -undergoes hydrogen atom (H81) abstraction by 0(2) to give b i r a d i c a l 36BR", and then the r a d i c a l s at C(l) and C(6) combine, r e s u l t i n g i n 36EA (Scheme 39). However, no product a r i s i n g from t h i s pathway was observed for ene-dione 49c. The l i k e l y reason i s that the required bond formation between C(l) and C(6) would disrupt aromaticity (Scheme 39). Scheme 39 It i s i n t e r e s t i n g to compare our s o l u t i o n r e s u l t s to the photochem-i s t r y of the 1,4-naphthoquinone/cyclopentadiene adduct 74 investigated by Kushner D and also by Mehta et a l . 1 (^ D The adduct 74, on photolysis i n benzene, affords the corresponding cage compound. In t h i s case, p a r t i c -i p a t i o n by the aromatic r i n g does take place to give 74CP". The bridgehead methylene group probably forces the adduct 74 into conforma-- I l l -t i o n ' C instead of the twist conformation of 49c. In conformation 'C, the 2,3-aromatic double bond i s p a r a l l e l and close to the 6,7-alkene double bond, an i d e a l s i t u a t i o n for [2+2] intramolecular c y c l o a d d i t i o n to occur. We r e c a l l here that the same explanation was used by Scheffer and T r o t t e r (discussed i n the Introduction section) to explain the dif f e r e n c e s i n the p h o t o r e a c t i v i t y of 1,3-butadiene/ benzoquinone adduct 34 and cyclopentadiene/benzoquinone adduct 40 (Scheme 23). hv • 74 74C.P" o Hydrogen atom abstraction by sp -carbon has precedence i n previous ene-dione p h o t o c h e m i s t r y , ^ 2 > d i s c u s s e d i n the Introduction section and i n the photochemistry of cyclopentenone 75 and cyclohexenones.173-175 For example, Agosta and co-workers 1'' 4 have demonstrated hydrogen abstrac t i o n reactions by the /3-carbon atoms of a v a r i e t y of cyclopente-nones. In the photolysis of cyclopentenone 75, hydrogen atom abstrac-t i o n by the /9-carbon i s suggested to occur through a six-membered t r a n s i t i o n state giving b i r a d i c a l 75BR. Ring closure of the b i r a d i c a l affords the b i c y c l i c product 75CB. Since t h i s r e a c t i o n could be s e n s i t i z e d and quenched, i t was thought to proceed v i a the t r i p l e t state. Schaffner and co-workers 1^ 1 suggested that hydrogen abstraction by /?-carbon was a t y p i c a l n ,TT t r i p l e t reaction. Although no photo-p h y s i c a l studies were performed with ene-dione 49c, by analogy with - 112 -o e a r l i e r w o r k , 1 2 , 1 7 6 i t can be suggested that i t i s the 7r,ff*3 state of the ene-dione moiety which i s involved i n hydrogen atom abstraction. The packing diagram of 49c indicated that neighboring molecules i n the c r y s t a l pack i n such a way that the carbonyl (C(1)=0(1)) of one molecule l i e s above C(4)=0(2) of another molecule i n a n t i p a r a l l e l fashion ( Fig. 14). The center to center distance between the two carbonyl groups i s 3.54 A. A s i m i l a r s i t u a t i o n was also encountered for ene-dione 76, where a n t i p a r a l l e l carbonyl alignment was thought to be responsible f o r the n o n - r e a c t i v i t y of 76 i n the s o l i d s t a t e . 1 6 ' 1 7 - ' - The present case of 49c demonstrates that r e a c t i o n does take place when the F i g . 14 113 C=0 bonds are a n t i p a r a l l e l , and therefore, the explanation given for 76 i s l i k e l y i n c o r r e c t . ( i i ) Photochemistry of 2.4a-Dimethvl-trans-4a.9a.9.10-tetrahydro-l.4- anthracenedione (50t) The adduct 50t was studied i n order to explore what e f f e c t a t r a n s - r i n g j u n c t i o n has on the photochemistry of an ene-dione. Can i t also undergo cyclobutanone formation s i m i l a r to the corresponding cis-adduct 49c , studied e a r l i e r ? 0 0 7 6 0 0 50t 50t IUPAC numbering Numbering used here to describe photochemistry 114 -Photochemistry I r r a d i a t i o n (N 2 l a s e r , 337 nm and 450 W lamp, > 290 nm) of c r y s t a l s of 50t, e i t h e r i n a KBr matrix or as a pure s o l i d , l e d to no detectable r e a c t i o n as determined by GC and i r spectroscopy. S i m i l a r l y , the photo-l y s i s i n a c e t o n i t r i l e d i d not r e s u l t i n any detectable (by GC and i r spectroscopy) amount of photoproduct and luminescence was observed. Molecular Conformation Although the X-ray c r y s t a l structure of the trans - compound was not determined, a molecular model of the adduct showed that 50t i s very r i g i d and displays very l i t t l e f l e x i b i l i t y due to the tr a n s - r i n g j u n c t i o n . Because the molecule i s quite r i g i d , the molecular model could give a reasonable idea about the molecular conformation and the r e l a t i o n s h i p s of the b e n z y l i c hydrogens with respect to the carbonyl oxygens and C=C. The molecular model showed that the b e n z y l i c hydrogens i n 50t do not l i e above, or even close to, the 2p-atomic o r b i t a l s of the ene-dione C=C double bond (Fig. 15). Therefore, the only reaction that was observed for 49c i s not permitted for 50t. In a c e t o n i t r i l e , 50t di s s i p a t e s i t s energy by luminescence. In the s o l i d state, no luminescence i s observed. - 115 -O H O F i g . 15 (b) Ene-diones That React D i f f e r e n t l y i n the S o l i d State and Solution ( i ) Photochemistry of 2.3.4a-Trimethyl-cis-4a.9a.9.10-tetrahvdro-1.4- anthracenedione (51) The photochemistry of ene-dione 51 was investigated with the same goals i n mind as the photolysis of 4 9 c . However, i n the present example, the 2,3-positions of the ene-dione 51 have been substituted with methyl groups i n such a way that the s t a b i l i t y of the b i r a d i c a l s 0 0 51 IUPAC numbering numbering used i n t h i s text - 116 51BR and 51BR' (see Scheme 41, page 119) formed, a f t e r hydrogen atom ab s t r a c t i o n should not be d i f f e r e n t . This means that both paths I and II shown i n Scheme 41 can be followed, and therefore, photoproducts from both conformations A and B should r e s u l t i n s o l u t i o n , whereas 'conformation s p e c i f i c photochemistry' can be expected i n the s o l i d state. Photochemistry The photolysis (A >290 nm, 450 W lamp, RT) of ene-dione 51 i n a KBr matrix showed the generation of i r peaks at 1765 cm"1 and 3425 cm"1, i n d i c a t i v e of the presence of a cyclobutanone r i n g and a hydroxy group r e s p e c t i v e l y . The i r r a d i a t i o n (A > 290 nm, 450 W lamp) of pure c r y s t a l s at room temperature y i e l d e d cyclobutanone 51CB' (Scheme 40) as the major product along with a dimer 51d as the minor (<10%) compound. I t was d i f f i c u l t to determine exactly the amount of the dimer formed because the compound was not v o l a t i l e under the GC conditions employed. How-ever based upon the amount of the cyclobutanone 51CB' and 51CB i s o l a t e d from a weighed amount of re a c t i o n mixture, i t was estimated that the dimer 51d formed i n le s s than 10% y i e l d . During the i n i t i a l stages of the photolysis, i t was noticed that only one GC v o l a t i l e cyclobutanone 51CB' was formed. However, as the photolysis time increased, i t was c l e a r that another GC v o l a t i l e product (51CB) formed. That 51CB was not an i n i t i a l s o l i d state photoproduct, but res u l t e d a f t e r melting, was confirmed by c r y s t a l photolyses at short times (5-10 min, low conver-- 117 51d 0 Scheme 40 sions, see Table 5). The 51CB was i n f a c t found to be a s o l u t i o n photoproduct. A s i m i l a r observation of more s o l u t i o n - l i k e behavior with higher conversion was also made by Omkaram 1 7 7 during the photolysis of cyclohexyl acetophenones i n the s o l i d state. This was also ascribed to melting of the sample during the pho t o l y s i s . Table 5 % Conversion % 51CB' % 51CB <2 only product 0 5.3 4.9 0.4 21.9 19.5 2.4 84 66.4 17.6 118 -The structure of the photoproduct 51CB' was derived i n the following way: i t s i r spectrum showed two strong carbonyl absorptions at 1765 and 1720 cm"1, i n d i c a t i v e of the presence of cyclobutanone and cyclohexanone rings r e s p e c t i v e l y . Its nmr spectrum, though accounting for a l l the hydrogens present i n the molecule, i s not very informative. I t features aromatic mu l t i p l e t s at 5 7.17-7.12, ben z y l i c and methine hydrogens i n t e g r a t i n g f or 4H at 6 3.17-2.83 i n the form of a m u l t i p l e t . The presence of a HC-CH3 u n i t at C(8) i s confirmed by a quartet at 8 2.17 coupled (J = 7 Hz) to the doublet at 8 1.05, i n t e g r a t i n g f o r 1H and 3H r e s p e c t i v e l y . The exo-hydrogen stereochemistry at C(8) i s based on the proposed mechanism (see Scheme 41) and also a f t e r r e l a t i n g with the C(8) stereochemistry of other s i m i l a r molecules studied at UBC. 1 1" 1^ The exo-C(8) stereochemistry of one of the cyclobutanones 52CB (Scheme 42) i n the present i n v e s t i g a t i o n was confirmed by X-ray crystallography. The remaining two nmr s i n g l e t s are due to the remaining two methyl groups present i n the molecule. An a d d i t i o n a l proof of the structure of 51CB' comes from comparing i t s nmr spectrum with that of i t s s t r u c t u r a l isomer 51CB (discussed l a t e r i n t h i s s e c t i o n ) . The mass s p e c t r a l parent peak at m/e 254 and a correct microanalysis for ^n^\H^l2 a l s o support the assigned structure. The structure of the dimer 51d could not be assigned. However, based on the mass spe c t r a l parent peak at 508 (13%) of the crude reac-t i o n mixture and the i r s p e c t r a l OH-peak at 3425 cm"1 and a C=0 peak at 1672 cm"1, we suggest that the product i s a dimer of unknown stereo-chemistry. The photolysis (A > 290 nm, 450 W lamp) i n a c e t o n i t r i l e also - 119 -51A Hydrogen atom abstraction by C(3) Path i Hydrogen atom abstraction 51B by C(2) Exclusive s o l i d state conformation Path i i 51 BR 51BR C(2)--C(8) bonding C(3)—C(5) bonding 0=f 51CB 51 CB Scheme 41 - 120 -r e s u l t e d i n the formation of two products, 51CB' (the s o l i d state photoproduct) and 51CB (new product) i n the r a t i o of 43:57. The photoproduct 51CB (Scheme 41) was i s o l a t e d by f l a s h column chromato-g r a p h y 1 4 6 and i d e n t i f i e d by i t s spectroscopic properties. Its i r spectrum features two strong carbonyl absorptions at 1765 and 1705 cm"1, i n d i c a t i v e of the cyclobutanone and cyclohexanone rings r e s p e c t i v e l y . Apart from an aromatic m u l t i p l e t and two methyl s i n g l e t s , the nmr spectrum reveals two doublets (J = 7 Hz) at S 3.38 and 5 3.19, assigned to the C ( l ) and C(2) methines or v i c e versa. The AB quartet at 6 2.80, i n t e g r a t i n g f o r 2H, i s assigned to the methylenes at C(5). The methine (quartet) at 5 2.22, which i s coupled (J •= 7 Hz) to the methyl (doublet) at 5 1.05, shows the presence of a HC-CH3 u n i t i n the molecule. The exo-hydrogen stereochemistry at C(8), once again, i s derived from the mechanism shown i n Scheme 41. F i n a l l y , the mass spectrum and the microanalysis support the structure. S o l i d State Conformation of 51 Once again, i n order to understand the r e a c t i v i t y of ene-dione 51 i n the s o l i d state, i t s X-ray c r y s t a l structure was determined. I t revealed that the ene-dione 51 c r y s t a l l i z e d i n conformation B (Fig. 16) instead of the expected lower energy conformation A. In conformation B, the bulky methyl group i s pseudoaxial with respect to the cyclohexene r i n g and therefore, a higher energy conformation than conformation A, where the methyl group i s pseudoequatorial. We have estimated the - 121 -di f f e r e n c e between conformers A and B f o r t h i s molecule to be 0.5 kcal/mole using the same method as discussed e a r l i e r . Although i t has been s u g g e s t e d 1 6 8 that most organic molecules c r y s t a l l i z e i n t h e i r lowest energy conformations, there are examples where organic compounds do c r y s t a l l i z e i n more than one conformation for example, polymorphs. The ene-dione 51 c r y s t a l l i z e s i n conformation B probably because there are c r y s t a l l a t t i c e forces (unknown at t h i s time) which s t a b i l i z e i t i n t h i s conformation. The mechanistic p i c t u r e i s thus as follows: since the ene-dione 51 c r y s t a l l i z e s i n conformation B (Fig. 16), H(51) points d i r e c t l y at the ene-dione double bond and i s , therefore, abstracted by C(2) through a six-membered t r a n s i t i o n state. The H(51)-atom ab s t r a c t i o n r e s u l t s i n the formation of a C(3) and C(5) b i r a d i c a l (51BR', Scheme 41). The b i r a d i c a l - c e n t e r s then combine to form the product 51CB'. The packing diagram 1 7^ of ene-dione 51 shows that the neighboring molecules pack i n such a way that the C=0 group of one molecule i s close to the benzylic hydrogen atom of another molecule. Therefore, intermolecular hydrogen a b s t r a c t i o n takes place leading to the formation of topochemically allowed product 51d. The process of intermolecular hydrogen atom - 122 -abst r a c t i o n i n the s o l i d state, although very rare, i s not without p r e c e d e n t . i / J Since a ra p i d equilibrium between conformers A and B (Scheme 41) i s expected to be present i n solut i o n , products from both conformations a r i s e i n the f l u i d medium. Further, conformer 51B probably has a higher free energy than conformer 51A, as stated e a r l i e r , therefore the major conformer present i n s o l u t i o n i s l i k e l y to be 51A. Not s u r p r i s i n g l y , on photolysis i n a c e t o n i t r i l e , the major photoproduct (57%, vs 43%) ar i s e s from conformation 51A. Based on a k i n e t i c scheme (Fig. 17) proposed by Lewis et a l . 1 ^ 8 f o r conformational isomers rea c t i n g photochemically i n s o l u t i o n to give d i f f e r e n t products, two l i m i t i n g s i t u a t i o n s can occur. In case I the a c t i v a t i o n energy f o r conformational isomerization i n the excited state i s l e s s than (or greater than, case II) the primary photochemical steps. In case I I , the r a t i o of products w i l l depend upon the excited state conformer population (A*, B*), and since e x c i t a t i o n i s much f a s t e r than molecular motion (Frank-Condon p r i n c i p l e ) , on the ground state conformer population. In order to understand whether i t i s the case I or case II s i t u a t i o n that p r e v a i l s i n the present example, we can estimate roughly A B B hv • A * A B * B Case I, » K A, Kg Case I I , K ^ « K A, Kg F i g . 17 123 the rate constant of hydrogen atom abstraction and the rate constant for conformational isomerization of 51. Rate constant f o r hydrogen atom abstract i o n can be estimated roughly from the rate constant of duroqui-g none/quinodimethane adduct 52 (see page 140), which i s 6.66 x 10 . An approximate value of the rate constant of conformational isomerization can also be derived from the known value of a c t i v a t i o n energy of confor-mational isomerization (AG^) for s i m i l a r compounds. Scheffer et a l . 1 4 9 have reported, from the temperature dependent 1 3 C nmr studies i n duroquinone/2,3-dimethyl-1,3-butadiene adduct 36, to be 8.7 kcal/mole. Using Eyring e q u a t i o n , 1 4 9 3 we estimate that the rate constant for conformational isomerization should be~10 7. These two rough c a l c u l a -tions suggest that the rate of hydrogen atom ab s t r a c t i o n i s about 15 times f a s t e r than the rate of conformational isomerization. This means that the re a c t i o n i s under the influence of ground state conformation ( i i ) Temperature-. M u l t i p l i c i t y - , and Phase Dependent Photochemistry of  2.3.4a.9a-Tetramethyl-cis-4a.9a.9.10-tetrahydro-1.4-anthracenedione c o n t r o l . 178-181 0 0 0 0 5 2 IUPAC numbering numbering used here to describe photochemistry 124 -Unlike ene-diones 49c, 50t and 51 studied so f a r , ene-dione 52 i s symmetrically substituted. Photochemistry I r r a d i a t i o n (N 2 l a s e r , A 337 nm, RT) of ene-dione 52 i n a KBr matrix gives strong i r peaks at 1745 and 1700 cm"1 i n d i c a t i v e of the formati on of photoproduct 52CB (Scheme 42). Photolysis (N 2 l a s e r , A 337 nm, RT) of a pure single c r y s t a l shows the formation of only one compound, 52CB, when the conversion i s kept below 5%. However, as the i r r a d i a t i o n time i s increased, the c r y s t a l melts and the appearance of another photoproduct 52CP i s also observed (Scheme 42). The r a t i o of Scheme 42 the photoproducts as a function of conversion i s shown i n Table 6. The major photoproduct of the s o l i d state photolysis was i s o l a t e d by f l a s h column chromatography 1 4 6 and i d e n t i f i e d by spectroscopy and X-ray crystallography. The i r spectrum of 52CB features carbonyl peaks at 125 -Table 6 % Conversion % 52CB % 52CP 4.1 only 15.2 14.8 0.4 31.1 30.2 0.9 84.3 81.6 2.8 1745 and 1700 cm"1 assigned to cyclobutanone (see discussion below) and cyclohexanone rings r e s p e c t i v e l y . The cyclobutanone carbonyl s t r e t c h i n g frequency of 1745 cm"1 i s approximately 20 cm"1 lower than the s i m i l a r cyclobutanone of 49CB (Scheme 38), 51CB and 51CB' (Scheme 41) and 36CB. 1 1 The C=0 str e t c h i n g frequencies of some cyclobutanones are given i n Scheme 43. 36CB 51 CB 1765 SICB' 1765 4 9 C B 1765 57AL s e e chapter 3 of t h i s thesis 1747 Scheme 43 Although the reported C=0 s t r e t c h of 36CB i appears at 1763 cm"1, i t s i r spectrum was recorded i n CCl^. I t i s we 11 known 1 4 7 that C=0 - 126 -s t r e t c h i n g frequencies are lowered i n the s o l i d state by 10-20 cm"1, therefore, the cyclobutanone C=0 s t r e t c h of 36CB could well be -1750 i n KBr. We note here that, unless otherwise stated, a l l the i r spectra of s o l i d compounds i n t h i s thesis were recorded i n a KBr matrix. The low frequency of cyclobutanone C=0 of 52CB i s also consistent with the C=0 s t r e t c h of 57AL (see Chapter 3). Since the formation of any other s t r u c t u r a l isomer was ruled out by nmr (see below) and on mechanistic grounds, i t was necesssary to investigate the reasons behind such a low frequency. For t h i s purpose, si n g l e c r y s t a l X-ray crystallography was used to determine 1 7*^ t f t e structure of the photoproduct 52CB. The X-ray c r y s t a l structure confirmed the presence of a cyclobutanone r i n g i n 52CB. I t also d i s c l o s e d that the C(C0)C bond angle i s 92° instead of 88° present i n compound 77 (i/C=0 = 1760 cm" 1). We suggest that the O r e l a t i v e l y l a rger C(C0)C bond angle of the cyclobutanone i n 52CB i s p a r t l y responsible for the lower C=0 frequency, since i t i s well known 1 0^ that the C=0 s t r e t c h i n g frequency depends on the C(C0)C bond angle. As the C(C0)C bond angle increases, the carbonyl carbon has lower p - o r b i t a l character i n the o r b i t a l s of the r i n g with a consequent decrease i n the s - o r b i t a l character of the C=0 a bond. This i n turn - 127 -decreases the force constant of the carbonyl group and causes a decrease i n the st r e t c h i n g frequency of the carbonyl group. The nmr spectrum of 52CB shows aromatic hydrogens at 8 7.25-7.07 and a C(2) methine s i n g l e t at 6 3.01. An AB quartet (J = 18 Hz) at 8 2.81 i n t e g r a t i n g f o r 2H i s assigned to the ben z y l i c hydrogens. A quartet at 6 2.23 i s coupled (J = 8 Hz) to the doublet at 8 1.05 i n d i c a t i n g the presence of a HC-CH3 u n i t i n the molecule. When the quartet at 8 2.23 i s i r r a d i a t e d , the doublet at 1.05 collapses to a s i n g l e t , thereby providing a d d i t i o n a l proof of HC-CH3 coupling. The remaining s i n g l e t s at 5 1.33, 8 1.24 and 8 1.19 are cr e d i t e d to the remaining three methyls present. The exo-hydrogen stereochemistry at C(8) i s assigned on the basis of the proposed mechanism (see Scheme 44) and i s also supported by X-ray crystallography. The mass spectrum and microanalysis also support the assigned structure. Ene-dione 52 was also photolyzed i n a c e t o n i t r i l e with a 450 W Hanovia medium pressure mercury lamp at A >290 nm. A GC trace of the rea c t i o n mixture showed the formation of two photoproducts, 52CB ( s o l i d state photoproduct) and 52CP i n >96% and <4% y i e l d s r e s p e c t i v e l y . The two products were i s o l a t e d by f l a s h chromatography and i d e n t i f i e d by spectroscopy. The spectroscopic properties of 52CB have been discussed e a r l i e r . The structure of 52CP was derived from the following spectros-copic data: i t s i r spectrum reveals only one C=0 st r e t c h at 1735 cm"1, i n d i c a t i v e of the presence of two five-membered r i n g ketones i n the photoproduct. The nmr spectrum of t h i s compound features aromatic hydrogens at 8 7.25-7.00, a methine s i n g l e t at 8 2.92 and a benzylic AB quartet (J = 16 Hz) at 8 2.80. The quartet at 8 2.32 i s coupled (J = 8 128 52 H D 52 si hj/ Hydrogen atom abstraction by 0(1) Hydrogen atom abstraction by C(2) 52BR Not allowed i n the s o l i d state 52BR" C(3)--C(5) bonding C(3)-C(8) bonding 52CB i f MeOD present [DjH 52E Scheme 44 - 129 Hz) to the doublet at S 0.96, i n d i c a t i n g the presence of a HC-CH3 unit i n the molecule. These peaks are accordingly assigned to the HC(9)-CH3 u n i t . The remaining methyl s i n g l e t s appear at 5 1.07, S 1.04, and S 0.92. The exo-hydrogen stereochemistry at C(9) i s assigned a f t e r r e l a t i n g to the known C(9)-exo-stereochemistry of 36CP (page 132) and also by the known preference of exo-protonation of the enolate anions of bicyclo[2.2.1]heptan-2-ones 78 and 80. 1 8 4 In t h i s s t u d y , 1 8 6 the enhancement of the exchange rate i n compound 78 over that i n 80 was a t t r i b u t e d to the con t r i b u t i o n of the homoenolate (79) species. The 22000 exo 78 79 e n d o 80 R e l a t i v e r a t e of exchange discu s s i o n of the stereochemistry at C(8) brings up the question of the mechanism of the formation of 52CP. Assuming that the ene-dione 52 adopts the same conformation i n s o l u t i o n as i n the s o l i d state, the re a c t i o n proceeds v i a hydrogen atom abstrac t i o n by oxygen (as shown i n Scheme 44), and subsequent isomerization and bond formation r e s u l t s i n enol 52E which undergoes ketonization to give 52CP. I f the mechanism stated above i s correct, then i t should be possible to trap enol 52E i f the photolysis i s c a r r i e d out i n MeOD. We have done exactly that. A f t e r i r r a d i a t i o n i n MeOD, 55% deuterium incorporation was observed by - 130 mass spectroscopy a f t e r adjusting f or the M*T peak. In three d i f f e r e n t enol trapping studies of ene-diones 36, 37, and 38 (Schemes 18, 19 and 22, r e s p e c t i v e l y ) , Scheffer et a l . 1 1 found 100%, 92% and 30% deuterium incorporation r e s p e c t i v e l y . S o l i d State Conformation of 52 In order to understand the r e a c t i v i t y of ene-dione 52 i n the s o l i d state, i t s X-ray c r y s t a l structure was determined. This revealed that ene-dione 52 c r y s t a l l i z e d i n the 'twist' conformation, depicted i n F i g . 18, i n such a way that the bridgehead methyl groups are staggered about the C(4a)-C(8a) bond, a general f e a t u r e 1 7 of a l l the ene-diones studied so f a r . I t further indicated that, l i k e a l l other ene-diones studied previously, the ene-dione r i n g of 52 i s nearly planar and i s c i s - f u s e d to the h a l f - c h a i r cyclohexene r i n g . In t h i s conformation, the endo-benzylic hydrogen at C(5) points d i r e c t l y at the ene-dione c e n t r a l C=C double bond. F i g . 18 131 -With the X-ray c r y s t a l l o g r a p h i c r e s u l t s i n hand, i t i s easy to understand the r e s u l t s obtained. Since H(52) l i e s over the ene-dione c e n t r a l double bond, i t can therefore be abstracted by the C(2) carbon through a six-membered t r a n s i t i o n state. The hydrogen atom abstraction r e s u l t s i n b i r a d i c a l 52BR (Scheme 44). Due to the r e s t r a i n t s of the c r y s t a l l a t t i c e , the b i r a d i c a l i s trapped i n e s s e n t i a l l y the same conformation as the ene-dione 52, and subsequently the C(3) and C(5) r a d i c a l centers collapse to give the photoproduct 52CB. The photopro-duct 52CB has e s s e n t i a l l y the same shape as 52. Thus, from the f i r s t step of the l i g h t absorption u n t i l the formation of 52CB, there i s r e l a t i v e l y l i t t l e conformational change, and the re a c t i o n proceeds with a minimum of atomic and molecular movement, i . e . , i t i s a topochemically o c allowed" reacti o n . I t i s l i k e l y that the same mechanism i s also operative i n s o l u t i o n as well, although there are fewer r e s t r i c t i o n s on the atomic and molecular movements i n s o l u t i o n . Scheffer et a l . 1 1 > 1 2 • 1 7 have also examined the photochemistry of ene-dione 36. The r e s u l t s are shown i n Scheme 15. Ene-dione 36 i s analogous to 52 and therefore, i t might be expected that a photoproduct analogous to 36EA should also be formed from 52. However, no product a r i s i n g from t h i s pathway was observed i n the case of 52. The reason i s that the required bond formation between C(4) and C(7) [or C(l) and C(6)] would disrupt the aromaticity. We also notice that another p o s s i b i l i t y f o r b i r a d i c a l combination ex i s t s i . e . , the r a d i c a l centers at C(3) and C(8) can collapse to y i e l d 52CP (already i s o l a t e d i n solution) (Scheme 44). The process of C(3)---C(8) r a d i c a l combination i s not allowed i n the s o l i d state as given below. 132 " * 0 + °=SN 36CB 36EA + 36CB + Ratio Solvent 36CB 36EA Benzene 0.5 1 t-Butanol 1.1 1 A c e t o n i t r i l e 4 1 Methanol 13 1 1:1 Dioxane:Water 30 1 S o l i d State 3 2 36CP 36CP Scheme 15 To understand the reasons f or the lack of C(3)-- -C(8) closure, we r e c a l l that one of the pr e r e q u i s i t e s f o r a s o l i d state r e a c t i o n i s that the distance between the r a d i c a l centres that eventually become bonded together should be close to the sum of the van der Waals r a d i i of the two atoms i n question, not greatly d i f f e r e n t from 3.40 A i n the case of two carbon atoms. Since the distance between C(3) and C(8) i s 4.36 A, - 133 as we s h a l l see l a t e r , the b i r a d i c a l , i f formed i n the s o l i d state, can reverse to the s t a r t i n g ene-dione. In order for bond formation to occur, 52BR' must undergo h a l f - c h a i r to h a l f - c h a i r conformational isomerization (Scheme 44). This motion i s too great to be accommodated by the c r y s t a l l a t t i c e and therefore, 52CP i s not observed i n the s o l i d state. Since no such r e s t r a i n t s are present i n s o l u t i o n , compound 52CP i s observed i n t h i s medium. Solvent, Wavelength and Temperature E f f e c t s During the measurement of the quantum y i e l d s f or the formation of 52CB and 52CP i n a Merry-go-round apparatus (2% aqueous a c e t o n i t r i l e , 450 W Hanovia medium pressure mercury lamp, A > 313 nm, temperature 19 ± 2°C), i t was noticed that the r a t i o of the products (52CB:52CP) was 45%:55%. This r a t i o i s very d i f f e r e n t from the r a t i o of >96%:4% for 52CB:52CP obtained e a r l i e r . Since, during the quantum y i e l d s measurements, the r e a c t i o n proceeded very slowly and only about 1%' of conversion was achieved a f t e r about 16 h of photolysis, i t was thought that the change i n r a t i o could be due to the presence of some impurities i n the r e a c t i o n mixture. Since t h i s suspicion turned out to be negative a f t e r GC analysis of the s t a r t i n g material, we turned our attention towards exploring the possible factors responsible for such a dramatic change i n r a t i o . The f i r s t obvious sources to investigate were the solvent and/or the wavelength e f f e c t s . Therefore, a ser i e s of photo-lyses were c a r r i e d out i n d i f f e r e n t solvents and at d i f f e r e n t wave-134 lengths. This d i d not show any s i g n i f i c a n t change i n the photoproudct r a t i o [see Table 11 i n the Experimental s e c t i o n ] , when the i r r a d i a t i o n was c a r r i e d out i n the 'normal way' i . e . not using the Merry-go-round apparatus. The one exception was photolysis i n methanol. In methanol, the 52CB:52CP r a t i o changed from 30:1 ( a c e t o n i t r i l e ) to 3:1. Similar changes i n the photoproduct r a t i o with change i n solvent from non-hydroxylic to hydroxylic were was also observed by G a y l o r , 1 4 and Jennings 1-* i n our laboratory during the photolyses of ene-diones. A t y p i c a l example i s shown i n Scheme 15 (page 1 3 2 ) . 1 1 The solvent e f f e c t , though not f u l l y understood, was explained by the authors on the basis of a polar i n t e r a c t i o n between the hydroxyl group of the solvent and the free valence e l e c t r o n at C(8) (structure 81). I t was suggested 1 1 that e l e c t r o n demotion of the b i r a d i c a l 81 may also occur r e s u l t i n g i n the formation of a solvated z w i t t e r i o n i c species 82. This may r e s u l t i n p r e f e r e n t i a l bond formation between C(3) and C(8) g i v i n g 36CP. Substituents omitted for c l a r i t y 135 -It has been shown by several workers that the quantum y i e l d of the Norrish type II r e a c t i o n 1 7 7 ' 1 8 5 increases s i g n i f i c a n t l y i n hydroxylic solvents such as alcohols compared to non-hydroxylic solvents such as benzene. For example, the quantum y i e l d s f o r Norrish type II reaction of 4-methyl-l-phenyl-1-hexanone 83 are given i n Table 7 . 1 8 5 Wagner 1 8 5 has suggested that the increased quantum y i e l d s i n polar solvents are due to s o l v a t i o n of the b i r a d i c a l intermediate 83BR, which reduces the reverse hydrogen t r a n s f e r from 83BR. Table 7; Solvent $ II (acetophenone) $ cyclobutanol Benzene Benzene + 2% t-BuOH t-BuOH 0.23 0.33 0.94 0.03 0.03 0.06 0 II PhCCH2CH2GH-'CH3 0 H NCH 2CH 3 83 PhCCH3 Acetophenone CH 3 ™ ^ J ^ C H 2 C H 3 HO Ph--CH-CH 2CH 3 Cyclobutanol 83BR - 136 We suggest that, i n the present case of ene-dione 52, a solvated species such as 52BRS' may be involved i n MeOH. Reverse hydrogen atom tr a n s f e r i s r e l a t i v e l y reduced f o r 52BRS' than 52BR i n MeOH and therefore, a r e l a t i v e l y higher y i e l d of the product a r i s i n g from 52BRS' i s observed. The p o s s i b i l i t y that a z w i t t e r i o n i c intermediate analogous to 82 i s formed and the e f f e c t of the solvent on the nature of the excited state involved i n the hydrogen abstraction cannot be rul e d out. The quantum y i e l d s f o r the formation of 52CB and 52CP were also determined and found to be 0.0038 and 0.0054, r e s p e c t i v e l y i n 2% aqueous a c e t o n i t r i l e . Such low quantum y i e l d s indicate that there are one or more deac t i v a t i o n processes for the excited state that do not lead to products; the most dominant among these may be reverse hydrogen atom tra n s f e r to give the ene-dione 52 i n i t s ground state. Once the e f f e c t of the solvent and the wavelength had been i n v e s t i -gated, we discovered that the r a t i o of the photoproducts was dependent on the temperature. l o D Thus, i t was found that as the photolysis temperature i s lowered, more of 52CP formed at the expense of 52CB. At -40°C (see Table 12, page 271), when the i r r a d i a t i o n was c a r r i e d out 137 -with a N 2 l a s e r , >80% of 52CP resulted. The photolysis was c a r r i e d out at d i f f e r e n t temperatures between +20° to -40°, and when the natural logarithm of the photoproduct r a t i o [ln(52CB/52CP) was p l o t t e d (Fig. 19) against 1/T, a reasonable s t r a i g h t l i n e was observed. This r e s u l t i s consistent with two f i r s t order processes that have d i f f e r e n t a c t i v a t i o n energies, the slope of the s t r a i g h t l i n e giving AEa. From the slope of the s t r a i g h t l i n e , an a c t i v a t i o n energy difference [Ea(52CB)-Ea(52CP] of 4.5 ± 0.2 kcal/mole was c a l c u l a t e d . 1 /Temperature (K) F i g . 19 138 -Af t e r i t had been established that the s o l u t i o n photochemistry of 52 was temperature dependent and yie l d e d mainly 52CP at -40°C, i t was of in t e r e s t to see what happened when 52 was photolyzed at -40°C i n the s o l i d state. On i r r a d i a t i o n at -40°C i n the s o l i d state, no photopro-duct corresponding to 52CP could be detected by GC; instead 52CB was the sole product. Thus, the sequence of steps leading to the formation of 52CB and 52CP i s suggested to be as follows: 1. 52S Q 52S X 2. 52S L =====•• 52BR' 3. 52BR' > 52BR" 4. 52BR" > 52E > 52CP 5. 52S± I S C > 52T L 6. 52Ti =====• 52BR 7. 52BR > 52CB The intermediacy of enol 52E was confirmed by trapping studies i n MeOD. We suggest that the hydrogen atom abstra c t i o n processes (step 2 and step 6) leading to the formation of 52BR' and 52BR are rate determining, with step 2 having the lower a c t i v a t i o n energy, owing i n part to the f a c t that has a higher e x c i t a t i o n energy than T^, as well as to the greater resonance s t a b i l i z a t i o n of b i r a d i c a l 52BR'. T u r r o 1 9 4 has suggested that, other factors being equal, hydrogen abstraction reactions from excited states with higher energy proceed f a s t e r than from excited states with lower energy. I t may also be noted that i n the - 139 s o l i d state, the reaction with the greater o v e r a l l a c t i v a t i o n energy process i s observed ex c l u s i v e l y , even at -40°C. The reason, as stated e a r l i e r , i s the r e s t r i c t i o n of step 3 by the c r y s t a l l i n e medium, and implies that step 2 i s r e v e r s i b l e i n s o l i d state. A f t e r f i n d i n g that the s o l u t i o n phase photochemistry of 52 i s temperature dependent, we decided to investigate the temperature-dependence of the photorearrangement of ene-dione 36 (Scheme 15) studied e a r l i e r by G a y l o r . 1 4 The behavior s i m i l a r to that exhibited by ene-dione 52 was found. The lower portion of F i g . 19 shows a p l o t of [ln(36CB)/ (36EA+36CP)] [ i . e . l n ( t r i p l e t product/sum of s i n g l e t photoproducts)] versus 1/T between -32°C and +78°C. The s t r a i g h t l i n e obtained has a slope nearly the same as that found for ene-dione 52, and the E a ( t r i p l e t ) - E a ( s i n g l e t ) d i f f e r e n c e so c a l c u l a t e d i s 4.2 ± 0.3 kcal/mole compared to 4.5 ± 0.2 kcal/mole for ene-dione 52. Photophysical Studies So f a r i t has been c l e a r l y established that there are two d i f f e r e n t b e n z y l i c hydrogens [H(81) and H(52)] that are abstracted by two d i f f e r -ent atoms i . e . 0(1) and C(2) r e s p e c t i v e l y . The question a r i s e s as to the nature and m u l t i p l i c i t y of the excited states involved i n hydrogen atom ab s t r a c t i o n by oxygen and by carbon. Information on the excited state m u l t i p l i c i t y ( s i n g l e t or t r i p l e t ) can be obtained i n two ways: 1. S e n s i t i z a t i o n Studies 2. Quenching Studies 140 -In order to carry out a s e n s i t i z e d reaction, benzophenone (Ej — 69.2 k c a l / m o l e 1 8 7 ) w a s selected as s e n s i t i z e r because of i t s known high e f f i c i e n c y i n t r a n s f e r of t r i p l e t e x c i t a t i o n . 1 8 7 Furthermore, since the t r i p l e t energy of the ene-dione chromophore of Die l s - A l d e r adduct 52 i s approximately 58 k c a l / m o l e , 1 7 0 d i f f u s i o n c o n t r o l l e d energy trans f e r i s expected. Even though i t was estimated from the e x t i n c t i o n c o e f f i c i e n t s of 52 and benzophenone at A >330 nm that only 65% of the l i g h t was absorbed by the s e n s i t i z e r at equal concentration, the re a c t i o n pro-ceeded smoothly g i v i n g both photoproducts, 52CB and 52CP. As the amount of the s e n s i t i z e r was increased, the i n i t i a l r a t i o of 52CB:52CP (3:1, see Table 13 i n the Experimental section) changed to 49:1 for 1.0 equivalent of s e n s i t i z e r . These observations suggest that the formation of 52CB probably takes place from a t r i p l e t state, whereas 52CP i s produced from a s i n g l e t state. For c a r r y i n g out t r i p l e t quenching s t u d i e s , 1 8 8 > 1 8 ^ 2,5-dimethyl-2,4-hexadiene was selected as the t r i p l e t quencher because i t possesses the q u a l i t i e s of a good quencher. 1 8 7 A seri e s of A > 313 nm photolyses were conducted on 0.10 M degassed solutions of 52 i n 2% aqueous a c e t o n i t r i l e containing varying amounts of 2,5-dimethyl-2,4-hexadiene. The formation of both 52CB and 52CP was observed by GC. From the r e s u l t s obtained, quantum y i e l d s were calcu l a t e d . A p l o t of $o/$ (where $o = quantum y i e l d without any quencher and <E> = quantum y i e l d i n the presence of a quencher) against quencher concentration [Q] showed two kinds of behavior ( F i g . 20). From the r e s u l t s , i t i s apparent that f or 52CB, there i s a d i r e c t competition between the reaction g i v i n g the product (52CB) and the i n t e r a c t i o n leading to the quenching of the excited 141 -• Cvclobulenone A Cyclopentanone Quencher Concentration F i g . 20: Stern-Volmer Study state, whereas no such competition was observed f o r 52CP; therefore, the quantum y i e l d f o r i t s formation does not change. We conclude that the formation of 52CB and 52CP takes place from two d i f f e r e n t excited states, almost c e r t a i n l y a t r i p l e t and a s i n g l e t state, r e s p e c t i v e l y . Similar observations of reactions from two d i f f e r e n t ene-dione excited states were also made by Scheffer et a l . 1 2 during the quenching studies of compound 36 (Scheme 15). In analogy with the photochemistry of the duroquinone/2,3-dimethyl-1,3-butadiene adduct 36, 1 2 we suggest that the s i n g l e t state of ene-dione 52 i s n ,7r i n nature, whereas the t r i p l e t - 142 -state i s of n,n* character. Schuster et a l . 1 9 ( ^ have reinvestigated the photochemistry of phenanthrone 84 and found that on photolysis i t gave three d i f f e r e n t photoproducts. Stern-Volmer quenching gave two d i f f e r e n t slopes. I t was concluded from the slopes that there were two d i f f e r e n t excited states involved i n the reaction. The formation of 85 and 86 (Scheme 45) was a t t r i b u t e d to the n,n t r i p l e t state, whereas 87 and 87a were suggested to a r i s e from the n , 7 r * t r i p l e t state. There are several other examples that have been reported by S c h a f f n e r 1 9 1 Zimmerman 1 9 2 and Schuster, J a l l with the same conclusion, that i s , i n reactions of a,/3-unsaturated ketones, J r , 7 r , t r i p l e t states favor a b s t r a c t i o n by the ^-carbon atom, and n , 7 r excited states lead to hydrogen atom abstraction by oxygen. Ti ,11 87a Scheme 45 - 143 -There are other examples i n the l i t e r a t u r e - ^ 4 " 1 9 6 where i t has been shown that a molecule can react from two d i f f e r e n t excited states. A representative example-^ 4 i s shown i n Scheme 46. Triene 88 reacts to give photoproducts 89 and 90 on d i r e c t p h o t o l y s i s . When photolyzed i n the presence of a s e n s i t i z e r , only 91 was o b t a i n e d . ^ 4 Qne of the very well investigated reactions i n organic photochemistry, the di-7r-methane rearrangement, i s also multiplicity-dependent. 89 (83%) 90 (14%) Scheme 46 Why do S^ and T^ of ene-dione 52 react d i f f e r e n t l y ? In order to understand the d i f f e r e n t behavior of s i n g l e t and t r i p l e t states, i t i s pertinent to discuss the concept of 'loose' and 'tig h t ' geometries of d i r a d i c a l o i d s as introduced by M i c h l . 1 ^ 7 According to Michl, excited 144 -s i n g l e t states are z w i t t e r i o n i c i n character, whereas t r i p l e t d i r a d i c a l -oids are ne u t r a l . I t follows that, a l l other factors being equal, favors ' t i g h t ' geometries f o r which the free ( i o n i c ) valences are close together i n space (Coulombic a t t r a c t i o n ) , whereas w i l l favor a 'loose' geometry f or which the free ( r a d i c a l ) valences are as f a r apart as possible (Fig. 21). Fi g . 21 Based on the concepts discussed above, the formation of compounds 94 and 95 from 92 and 93 was explained as shown i n Scheme 47.-*-^8 B i r a d i c a l s 92BR and 93BR generated by the photolyses of 92 and 93 re s p e c t i v e l y y i e l d the same photoproduct i r r e s p e c t i v e of the s t a r t i n g diazo compound. The rea c t i o n v i a the s i n g l e t state prefers 't i g h t ' geometries and therefore, 93BR and 92BR react to give norbornadiene 95. In case of the t r i p l e t state, the 'loose' b i r a d i c a l s separated by two bonds react to give quadricyclane 94. 145 -Scheme 4 7 We also suggest that f o r ene-dione 52, the d i f f e r e n t behavior of the (n,7r ) L and (TT.TT ) j excited states may be due i n part to the preference f o r the t r i p l e t excited state to give a b i r a d i c a l intermedi-ate that has greater separation between the r a d i c a l centers ( i . e . 'loose' d i r a d i c a l o i d structure, 52BR) than the b i r a d i c a l intermediates 52BR' or 52BR" formed from the s i n g l e t excited state ( i . e . ' t i g h t ' or z w i t t e r i o n i c s t r u c t u r e ) . Comparing b i r a d i c a l s 52BR and 52BR' (Scheme 146 -44), i t can be seen that the r a d i c a l centers i n 52BR' (singlet-derived) can approach each other more c l o s e l y (two bond separation) than they can i n t r i p l e t - d e r i v e d 52BR (minimum three bond separation). Thus i n short, the main features of the photochemical rearrange-ments of erie-dione 52 can be summarized as given below. 1. On photolysis i n the s o l i d state only one product, 52CB, was observed at room temperature as well as at -40°C. 2. I r r a d i a t i o n i n s o l u t i o n leads to photoproducts 52CB and 52CP i n a r a t i o dependent on the solvent and temperature of the reaction employed. At lower temperatures (-40°C), 52CP i s the preferred product, whereas at room temperature 52CB i s the major product. A r a t i o of 52CB/52CP i s obtained at various temperatures, and from the p l o t of l n (52CB/52CP) against 1/T, an E a ( t r i p l e t ) - E a ( s i n g l e t ) energy d i f f e r e n c e of -4.50 ± 2 kcal/mole i s c a l c u l a t e d . 3. S e n s i t i z a t i o n studies have been c a r r i e d out with benzophenone, which show that, as the amount of benzophenone i s increased from 0.10 equivalent to 1.0 equivalent, the i n i t i a l r a t i o of 52CB:52CP (3:1) has changed to 49:1, thus i n d i c a t i n g that 52CB may be a t r i p l e t - d e r i v e d product, whereas 52CP may be s i n g l e t - d e r i v e d . The quenching study also supports t h i s f i n d i n g . Thus the photochemical rearrangement discussed above i s unique i n the sense that i t b e a u t i f u l l y demonstrates how three v a r i a b l e s i . e . temperature, m u l t i p l i c i t y , and phase can c o n t r o l the outcome of a photochemical reaction. - 147 -Reaction of 3,4-Benzo-l,6,8-endo-9-tetramethyltricyclo[4.4.0.0 2 • 9 ] -decan-7,10-dione (52CB) with Sodium Hydroxide Scheffer et a l . 1 " have shown that reactions of cyclobutanones such as 36CB and 96CB with aqueous potassium hydroxide a f f o r d e s s e n t i a l l y quantitative y i e l d s of 36CP and 96CP r e s p e c t i v e l y (Scheme 48). The authors proposed that the most l i k e l y mechanism for the formation of 96CB, Y = Z = CH 3, X = Et 96CP Scheme 48 36CP or 96CP i s v i a successive [2,3] and [1,3]-sigmatropic rearrange-ments. The enolate of CB gives 97 v i a an allowed [2,3]-sigma-tropic s h i f t , and 97 then rearranges to CP through a secondary (formal) [1,3]-sigmatropic s h i f t . A concerted 1,2-anionic s h i f t i s forbidden by o r b i t a l symmetry consideration, but may be possible (see the o r i g i n a l p a p e r 1 " f o r d e t a i l s ) , whereas a nonconcerted 1,2-shift v i a carbanion 98 or d i r a d i c a l anion 99 i s ru l e d out. The intermediacy of 98 was ruled out because of expected but unobserved protonation i n the aqueous medium. - 148 -We were curious to know what happens i f 52CB i s treated with aqueous KOH. W i l l we obtain 52CP analogous to 36CP or 96CP? Can we shed l i g h t on any of the mechanisms out l i n e d above? Accordingly, 52CB was treated with aqueous KOH at r e f l u x and the r e s u l t s are shown i n Scheme 49. Two points are very c l e a r from our r e s u l t s . 100 52 Scheme 49 - 149 1. The f a c t that 52CP does not form supports the mechanism of successive [2,3] and [1,3]-sigmatropic s h i f t s , because [2,3] s h i f t i n the present example would disrupt aromaticity and are, there-fore, disfavored. 2. The formation of ene-dione 52 i n >90% i s o l a t e d y i e l d , presumably v i a anion 100, supports the [2,3] and [1,3]-sigmatropic s h i f t s mechanism. This i s because the regeneration of ene-dione 52 does not require the d i s r u p t i o n of the aromaticity. Thus, i t can be concluded that the mechanistic aspects of 36CB and 96CB y i e l d i n g 36CP and 96CP i n the presence of a base are c l e a r and are correc t as proposed. whatever the mechani sm, the discovery of 52CP y i e l d i n g 52 on treatment with base has been a great convenience to the author. He frequently cycled and recycled the 52 and 52CB and thus avoided the high cost of making 52 and saved time as well. Apart from s o l v i n g the mechanism of the base catalyzed rearrange-ment and helping the author to save time, the r e a c t i o n described above could also serve as a p o t e n t i a l s o l a r energy storage c y c l e . 2 < ^ •201 The p o s s i b i l i t y of the storage of sol a r energy i n the form of chemical energy has at t r a c t e d the att e n t i o n of almost a l l the indus-t r i a l i z e d nations. The idea of sol a r energy storage involves the synthesis of a compound A which can absorb a photon d i r e c t l y or v i a a s e n s i t i z e r to give an excited A and then form the energy r i c h product B as given below. The product B i s then reconverted into A r e l e a s i n g the stored energy i n the form of heat. The amount of heat released depends on the - 150 -A ^ A * » - B Energy release d i f f e r e n c e between the heat of formation of the product and the reactant and i s accurately determined by calorimetry. 2^1 >2^2 i n the present example of cyclobutanone 52CB y i e l d i n g ene-dione 52, a crude e s t i m a t e 2 ^ 2 t e l l s that about 10-12 kcal/mole of energy i s released. In other words -10-12 kcal/mole of energy can be stored i n 52CB. ( i i i ) Photochemistry of cis-4a.9a.9.10-Tetrahydro-1.4-anthracenedione 147J. IUPAC numbering numbering used i n t h i s text to describe photochemistry This i s the only compound i n the present study that provides an example of intermolecular [2+2] dimerization i n the s o l i d state. - 151 -Photochemistry I r r a d i a t i o n (N 2 l a s e r , 337 nm) of ene-dione 47 i n a KBr matrix i s s u r p r i s i n g l y f a s t , and the reaction i s complete i n less than ten min. The i r spectrum of the product 47d shows a strong carbonyl peak at 1705 cm"-'- i n d i c a t i n g the presence of a cyclohexanone r i n g . The needle-shaped c r y s t a l s of ene-dione 47 were also photolyzed (N 2 l a s e r , 337 nm or at A > 290 nm, 450 W lamp), r e s u l t i n g i n the formation of a photodimer t e n t a t i v e l y assigned structure 47d (Scheme 50) i n 100% y i e l d . Scheme 50 47d The structure of the photodimer could not be established unequivo-c a l l y . However, the following spectroscopic data support the general general structure: the i r spectrum of the photodimer 47d shows a strong C=0 peak at 1705 cm"1. The mass spectrum shows the parent peak at m/e 424, twice the molecular weight of the monomer 47, and the compound analyzed c o r r e c t l y f o r ^gH^O^. An nmr spectrum of the compound i n 152 -question could not be obtained because i t i s insoluble i n most common organic solvents. I t dissolves only i n b o i l i n g DMF, and the dimer p r e c i p i t a t e s as soon as the temperature goes below the b o i l i n g point. Due to the same s o l u b i l i t y problems, no c r y s t a l s of 47d s u i t a b l e for X-ray crystallography could be grown. S o l i d State Conformation Since the c r y s t a l structure of ene-dione 47 could not be determined because i t s c r y s t a l s were not su i t a b l e f or X-ray d i f f r a c t i o n study, the exact conformation i n which the compound c r y s t a l l i z e s i s unknown. However, based upon X-ray c r y s t a l structure studies of symmetrical ene-diones such as 52 (page 123), 36 (page 38), 34 (page 2 6 ) , 1 7 and a l l other ene-diones investigated i n t h i s thesis and by Scheffer et a l . , 7 ^ i t can be assumed that the adduct 47 c r y s t a l l i z e s i n the same "twist" conformation as 34, although the c r y s t a l packing of the molecules may or may not be s i m i l a r . A l l the 1,3-butadiene/p-benzoquinone adducts studied by Dzakpasu 1 7 which undergo photodimerizations i n the s o l i d state (Scheme 51) pack i n a centrosymmetric fashion and therefore y i e l d centrosymmetric dimers. By analogy, i t can be suggested t e n t a t i v e l y that the photodimer 47d i s also a centrosymmetric dimer and therefore has the stereochemistry shown below. However, complete c h a r a c t e r i z a t i o n of 47d requires X-ray crystallography. 153 R Scheme 51 An i n t e r e s t i n g feature of the photodimerization i n the present example i s that i t i s a r a r e 8 8 example of 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 dimerization. Although i r r a d i a t i o n both at room temperature and 0°C causes the needle-shaped single c r y s t a l s of the monomer (average length 4-8 mm) to shatter into smaller c r y s t a l s of the dimer, each smaller piece (0.5-1 mm) i s a sin g l e c r y s t a l of the dimer, as determined through the use of a p o l a r i z i n g microscope; no c r y s t a l l o g r a p h i c parame-ters could, however, be determined. This r e a c t i o n i s an example of a class of organic s o l i d state reactions c l a s s i f i e d as topotactic 7-' ( t o p o t a x i c 8 1 ) reactions. The p o s s i b i l i t y of 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 was f i r s t - 154 -introduced by Schmidt, 0 0 even though his group d i d not a c t u a l l y discover such an example. The honor of discovering a t o p o t a c t i c 7 5 ( t o p o t o x i c 0 1 ) r e a c t i o n probably goes to G o u g o u t a s , 2 ^ 2 ' > 7 5 who found that halogen-substituted dibenzoyl peroxides rearrange thermally, photochemically and under X-ray bombardment to a f f o r d unusual polyvalent iodine compounds (Scheme 52). Thomas et al. 9 4'95,97 f o u n d that the dimerizations of 2-benzyl-5-benzylidenecyclopentanone (101) and i t s p-bromo de r i v a t i v e was also a s i n g l e c r y s t a l to s i n g l e c r y s t a l r e a c t i o n (Scheme 53). One of the c h a r a c t e r i s t i c features of a topotoxic r e a c t i o n found i n the case of 101 i s the extreme s i m i l a r i t y i n various c r y s t a l l o g r a p h i c parameters such as space group and u n i t c e l l volume of the s t a r t i n g material and the photoproduct. Thomas et a l . 9 4 ' 9 5 ' 9 7 pointed out that the packing arrangement of 101 and i t s dimer l O l d i s such that the dimerization requires very l i t t l e motion. 155 -Although no mechanistic investigations have been c a r r i e d out for the photodimerization of ene-dione 47, analogy can be drawn from numerous examples of such reactions both i n s o l i d state and so l u t i o n . For example, i t has been agreed0-* that the photodimerization reactions involve the union of an excited monomer and a ground state monomer. This has been demonstrated experimentally f o r s o l i d s t a t e 0 ^ and s o l u t i o n 2 ^ 4 dimerization reactions. I t has also been suggested^ 0 that dimerization i n the s o l i d state may be a concerted [TT2S + 7r2s] process unlike i n s o l u t i o n 2 ^ 1 4 >2^5 where dimerization may be concerted or stepwise. I t has also been suggested that dimerization i n the s o l i d state may occur from a s i n g l e t s t a t e , 8 ^ whereas i n so l u t i o n , dimeriza-t i o n may occur e i t h e r from a s i n g l e t state or t r i p l e t state depending on the r e a c t i o n conditions . 2 ^ ° " 2 < ^ 7 A small amount of adduct 47 was also photolyzed (A > 330 nm, 450 W lamp) i n a c e t o n i t r i l e , and the reaction was followed by i r spectroscopy. An i r spectrum of the crude reaction mixture shows carbonyl peaks at - 156 -1774 and 1716 cm"1, i n d i c a t i v e of the formation of 47CB (Scheme 50). Unfortunately at t h i s stage i t was r e a l i z e d that the author has a very high s k i n s e n s i t i v i t y towards even trace amounts of benzene, and since the reactions leading to the synthesis of adduct 4 7 1 8 require extensive use of benzene, no attempt was made to prepare large quantities of 47 and eventually i s o l a t e and characterize the photoproduct 47CB completely. Even though the structures of the photoproducts obtained from ene-dione 47, both i n the s o l i d state and sol u t i o n , are rather specula-t i v e , i t i s very tempting to suggest that these r e s u l t s are p a r a l l e l to the photochemistry of ene-diones 34, 37 and 38 (Schemes 16 and 17) and s i m i l a r i n p r i n c i p l e to the photochemistry of the cinnamic a c i d deriva-t i v e s studied by Schmidt. 8 5 We r e c a l l here that cinnamic a c i d deriva-t i v e s undergo [2+2] dimerization i n the s o l i d state, whereas unimolecu-l a r photochemistry ( c i s - t r a n s isomerization) i s observed i n sol u t i o n . D e t a i l s of the s o l i d state and s o l u t i o n photochemistry of cinnamic acid d e r i v a t i v e s are given i n the Introduction section. - 157 -C. Ene-diones That React i n Solution But Not i n S o l i d State ( i ) Photochemistry of 5a.lla-Dimethyl-cis-5a.11a.6.11-tetrahydro-5.12-naphthacenedione ( 5 4 ) ^ u o IUPAC numbering numbering used i n t h i s text to describe photochemistry As anticipated, i r r a d i a t i o n of a c e t o n i t r i l e solutions of 54 through Pyrex (A > 290 nm) r e s u l t e d i n the formation of the desired product, cyclopropanol 54P i n 35% y i e l d . GC analysis of the re a c t i o n mixture p r i o r to chromatography showed the presence of several other v o l a t i l e products. Further column chromatography permitted the i s o l a t i o n of small amounts of two of these substances, the ketoaldehyde 54KA (9%) and lactone 54L i n 22% y i e l d (Scheme 54). The cyclopropanol 54P has spectroscopic properties as expected, which are given i n the Experimental section. I t i s a c o l o r l e s s , crys-t a l l i n e material that i s stable i n b o i l i n g benzene f o r at l e a s t 18 hours. The i r spectrum of ketoaldehyde 54KA shows three prominent peaks at 2750, 1682 and 1650 cm"1. The signals at 2750 and 1682 cm"1 are complementary to one another and are assigned to the -CHO group. The - 158 -54 54P 54KA 54L Scheme 54 C=0 peak at 1650 cm"1 i s assigned to the ketone carbonyl group a f t e r comparing t h i s value to the l i t e r a t u r e v a l u e 1 4 7 f o r a d i a r y l ketone (1650-1660 cm"1 i n s o l i d s t a t e ) . The nmr spectrum of the ketoaldehyde 54KA features e s s e n t i a l l y four peaks i n the r a t i o of 1:9:3:3 and does not show any a l i p h a t i c hydrogens other than two methyl s i n g l e t s . The s i n g l e t at S 10.80 (i n t e g r a t i o n 1H) i s cr e d i t e d to the presence of the H-C=0 u n i t i n the molecule. The m u l t i p l e t at 5 8.10-7.15 integra t i n g f o r 9H i s assigned to the aromatic hydrogens. The remaining two sing-l e t s (3H each) at 6 2.47 and 6 2.25 are assigned to the two methyls present i n the molecule. The chemical s h i f t s of 5 2.47 and S 2.25 are comparable to the corresponding methyl group chemical s h i f t i n 2,3-dimethylnaphthalene (6 2 . 4 0 ) . 1 6 4 The mass spectrum shows the molecular ion peak at m/e 288, and the compound analyzed c o r r e c t l y for C20 H16°2-The i r spectrum of the lactone 54L shows a strong carbonyl peak at 1742 cm"1, i n d i c a t i v e of an unsaturated 5-membered lactone r i n g . The - 159 -C=0 s t r e t c h i n g frequency of the lactone 54L (1750 cm"1) 1N209 compares well with the C=0 s t r e t c h of 101a. 101a The nmr spectrum of compound 54L features a m u l t i p l e t at 6 8.30-6.90 in t e g r a t i n g f o r 10H and assigned to 9 aromatic hydrogens plus 1 methine hydrogen. The chemical s h i f t of the methine hydrogen, assumed to l i e under the aromatic hydrogens, i s not s u r p r i s i n g at a l l i f we compare i t with the corresponding chemical s h i f t of the benzylic protons of phthalide 102a. The methylene hydrogens of phthalide 102a appear at 6 5.32, 1 5 4 and a f t e r adding the deshielding e f f e c t of 1.8 1 4 7 by an aromatic r i n g , an approximate chemical s h i f t value f o r the methine proton of 6 7.12 i s calc u l a t e d . The nmr spectrum of 54L also indicates the presence of four methyl s i n g l e t s i n t e g r a t i n g f o r 6 hydrogens (!) assigned to four "h a l f methyls". That these four methyl s i n g l e t s are 0 102 a, R = H b, R = Ar - 160 -due to the presence of two conformers i n an approximately 1:1 r a t i o i n slow equilibrium i s c l e a r l y shown by a 90°C nmr spectrum. Fast exchange i s achieved at 90° as indicated by the following •L-'C nmr values (DMS0-d 6): S 170.1 (C=0), 150.7, 135.6, 135.5, 134.7, 132.3, 129.9, 129.2, 128.0, 127.2, 126.1, 125.9, 125.7, 125.1, 124.9, 122.5, 122.2 (aromatics), 79.4 (methine carbon), 20.7 and 15.7 (methyls). At 25°C, the peaks at 79.4, 20.7 and 15.7 ppm are broad doublets. The mass sp e c t r a l peak (m/e) at 288 and correct microanalysis for C20H16O2 also support the assigned structure. The formation of cyclopropanol 54P involves a /3-hydrogen atom abstract i o n by oxygen (01) through a five-membered t r a n s i t i o n state to give a 1,3-biradical which collapses to y i e l d the product. ^-Hydrogen atom ab s t r a c t i o n by oxygen does not need any further comment i n the present study. However, i t i s appropriate at t h i s point to c i t e some of the studies c a r r i e d out by Agosta et a l . 2 1 ^ Several a-methylene ketones were i r r a d i a t e d 2 1 ^ to give two types of products shown i n Scheme 55. The general mechanism f o r the formation of cyclopropyl ketones i n Scheme 55 involves a b s t r a c t i o n of a /9-hydrogen atom to give a resonance s t a b i l i z e d b i r a d i c a l which then collapses to form cyclopropyl ketone (103). S i m i l a r l y , the formation of cyclobutyl ketones (104) takes place v i a 7-hydrogen abstrac t i o n by oxygen followed by b i r a d i c a l collapse. Another example which i s very s i m i l a r to the cyclopropanol forma-t i o n i n the present study i s by Roth and E l R a i e . 2 1 1 They showed that ketones of general structure 105 undergo smooth /3-hydrogen atom ab s t r a c t i o n leading to the formation of 105P as i l l u s t r a t e d i n Scheme 56. - 161 -Scheme 55 - 162 105 1,3-diradical 1°5P Scheme 56 Once the question of the structures of the photoproducts i s solved, the mechanistic c u r i o s i t i e s a r i s e , that i s , what are the mechanisms of the formation of 54L and 54KA? Do 54L and 54KA a r i s e d i r e c t l y from 54 or v i a 54P? By an independent photolysis of 54P, we have confirmed that 54L and 54KA a r i s e from 54P (Scheme 57). Thus, as out l i n e d i n Scheme 54L' Scheme 57 163 -57, we view the formation of photoproducts 54L and 54KA as r e s u l t i n g from novel r i n g opening of cyclopropanol 54P to give ketene-enol intermediate 54KE, followed by thermally a l l o w e d 1 4 7 1,5-hydrogen tra n s f e r to a f f o r d 54KA' or closure to y i e l d 54L'. Products 54KA and 54L are then formed by oxidation during workup of dihydronaphthalene deriva-t i v e s 54KA' and 54L' respectively. The e l e c t r o c y c l i c r i n g opening postulated above i s not without some precedent. For example, i t has been shown by several w o r k e r s 2 1 2 that conjugated cyclohexadienones undergo a-cleavage r e a d i l y to form unsaturated ketene. An example of 6,6-dimethyl-2,4-cyclohexadienone i s shown below. I t was noticed that the GC peaks due to 54L' increase with increasing i r r a d i a t i o n time while those due to 54KA' and 54P decrease proportionately, i n d i c a t i n g that 54KA' may revert photochemically to 541/. Independent i r r a d i a t i o n of ketoaldehyde 54KA showed that i t undergoes photoenolization to a f f o r d lactone 54L i n 100% GC y i e l d (this i s an unusual re a c t i o n and w i l l be discussed i n d e t a i l l a t e r ) . There i s an exact l i t e r a t u r e 2 1 3 " 2 1 6 precedent f o r the aldehydic hydrogen atom - 164 -abst r a c t i o n i n the photorearrangement of o-phthalaldehyde (106a) to phthalide v i a a ketene-enol intermediate as shown i n Scheme 58. i U o phthalide a. R=H b. R=CH3 c. R=Ph Scheme 58 Returning to the photorearrangement of ketoaldehyde 54KA to 54L, i t has been shown 2 1 7-219 t n a t a. naphthyIketones u s u a l l y have lowest t r i p l e t states that are n , i r i n character and are therefore poor hydrogen atom abstractors. Furthermore, the difference between the lowest t r i p l e t state and the next higher t r i p l e t state i s large, f o r example, 18 kcal/mole f o r 2-acetonaphthalene. 1 8 7 Since 54KA i s a 1-naphthyl phenyl ketone d e r i v a t i v e and not a naphthyl a l k y l ketone, i t may be that the energy d i f f e r e n c e between the lowest t r i p l e t (T^) and the next higher t r i p l e t (T 2) may not be as large as i n the case of 2-acetonaphthalene. The energy d i f f e r e n c e f o r naphthyl phenyl ketone 107(below) was found to 9 9 0 be 8.9 k c a l / m o l e . ^ u This s t i l l large energy diffe r e n c e means that the ix,n and n,ix t r i p l e t states of 107 cannot be s o l e l y i n thermal 1 8 4 9 9 1 e q u i l i b r i u m ^ 0 ^ but n,ix w i l l have some v i b r o n i c coupling^- 1- to the n,7r - 165 state. We suggest by analogy with 1-naphthyl phenyl ketone (107) that the lowest t r i p l e t state of 54KA i s n,ir i n character with some n,)r J character, and as the reaction of hydrogen atom abstraction progresses, the n,7r state drops i n energy and the n , n r i s e s i n energy. Therefore, hydrogen atom abstrac t i o n i s observed. The same explanation was used by de Boer et al.LJ to explain the p h o t o r e a c t i v i t y of ketone 107 shown below. This i s another example of 'state switching' during r e a c t i o n . 1 9 3 OH 107 107a I r r a d i a t i o n (N 2 l a s e r , 337 nm; 450 W lamp, A > 290 nm) of the adduct 54 i n a KBr matrix or as a pure c r y s t a l d i d not show any trace of reaction, even a f t e r very long (up to 10 h) i r r a d i a t i o n times, as shown by i r , GC and t i c . In order to understand the n o n - r e a c t i v i t y of 54 i n the s o l i d state, i t s c r y s t a l and molecular structure was determined. S o l i d State Conformation The X-ray c r y s t a l structure of 54 revealed that there are two independent molecules with s l i g h t l y d i f f e r e n t conformations i n the 166 -asymmetric u n i t and that each has a h a l f chair cyclohexene r i n g c i s -fused to a nearly planar cyclohexen-1,4-dione moiety. A s p e c i a l feature of t h i s compound i s that the molecules pack i n stacks c o n s i s t i n g of a l t e r n a t i n g conformers (Fig. 22a). Since the ene-dione 54 has geometrical parameters f or hydrogen abs t r a c t i o n (d, r and A) which are s i m i l a r to the values f o r other ene-diones that react i n the c r y s t a l l i n e state (these parameters w i l l be discussed together l a t e r i n t h i s thesis i n Chapter 5), the u n r e a c t i v i t y of ene-dione 54 i s rather s u r p r i s i n g . We suggest that a s t e r i c compression phenomenon i s responsible for the n o n - r e a c t i v i t y of ene-dione 54. I f we look at the packing diagram (Fig. 22a), we notice that a s p e c i a l feature of the molecular packing of 54 that we f e e l explains the lack of cyclopropanol formation i n the s o l i d state i s evident i n the view shown. A methyl group of a lower molecule projects d i r e c t l y into the space between the two aromatic rings of an upper molecule. Cyclopropanol formation requires that these two rings move considerably c l o s e r together, and t h i s i s prevented by the presence of the methyl group from the neighboring molecule. The loca-t i o n of the methyl group with respect to the two aromatic rings i s i l l u s t r a t e d i n F i g . 22b. In the reactant 54, the center-to-center distance between the two rings i s 6.48 A, and the intruding methyl carbon-to-center distances are 4.12 A and 4.75 A for one molecule. The other molecule i n the asymmetric u n i t has an interatomic center-to-center distance of 6.52 A and methyl carbon-to-benzene center distances of 4.1 A and 4.68 A. A f t e r reaction, the conformationally r i g i d cyclopropanol 54P has an aromatic center-to-center distance of 4.1 A as - 167 a Molecular stacks F i g . 22a before reoctlon ofter reaction F i g . 22b estimated from Dreiding models. Assuming an i d e n t i c a l methyl group l o c a t i o n i n the s t a r t i n g material and the photoproduct, the distances between the intruding carbon and the aromatic centers i n photoproduct 54P are reduced to 2.6 A and 3.0 A, r e s p e c t i v e l y . These distances are too short to accommodate the methyl group. Methyl groups have van der Waals r a d i i of 2.0 A, 222 and when t h i s i s added to the van der Waals h a l f "thickness" of an aromatic r i n g (1.7 A), the sum of 3.7 A c l e a r l y indicates p r o h i b i t i v e " s t e r i c compression"^ 0^»223,224 accompanying cyclopropanol formation. A s i m i l a r s t e r i c compression co n t r o l argument was given by Scheffer et a l . > 2 2 3 , 2 2 4 t o e x p i a i n the preference for hydrogen atom abstrac-t i o n by a vs. /9-carbon atoms of enones of general structure 108. Of the 168 -R4 R, 108 seven enones investigated photochemically i n the s o l i d state, a l l reacted v i a path A or path B except one compound which reacted v i a path C (Scheme 59). Path A and path B involve hydrogen atom abstrac t i o n by the ^-carbon and therefore, are favored due to the s t a b i l i t y of the Scheme 59 169 -b i r a d i c a l s formed. Path C involves hydrogen atom abstrac t i o n by the a-carbon atom and i s thus a less favored process due to the r e l a t i v e l y low s t a b i l i t y of the non-delocalized r a d i c a l compared with the delocal-ized r a d i c a l formed v i a path A or B. In order to explain t h i s prefer-ence of compound 108g to follow an e n e r g e t i c a l l y less favorable path, Scheffer et a l . 2 2 ^ - 2 2 ^ suggested that the change i n h y b r i d i z a t i o n of C Q or Co from sp^ to sp , which n e c e s s a r i l y accompanies hydrogen trans f e r Table 8: Reactants, Hydrogen Abstraction Distances and S t e r i c Compressions i n S o l i d State Photorearrangements S t e r i c Compression Accom-Enone 108 R 2 R 3 R 4 H-•-Ca (A) H---C^ (A) P panying c a P y r a m i d a l i z a t i o n a  C £ a CH 3 CH 3 H OH 2. .78 2, .75 yes yes b CH 3 CH 3 OAc H 2. .79 2. .84 yes yes c CH 3 CH 3 OH CH 3 2. .86 2. .81 yes yes d H CH 3 H OH 2. .82 2. .78 yes no e H CH 3 OH H 2. .74 2, .85 yes yes f H H H OH 2. .92 2. .84 yes yes g CH 3 CH 3 H OAc 2, .74 2 .70 no yes Yes indicates a hydrogen-hydrogen contact upon p y r i m i d a l i z a t i o n of < 1.9 A. In some cases, more than one contact i s developed. No i n d i -cates no contacts < 2.2 A. The exact values are not given as they vary with methyl group r o t a t i o n . 170 -to these atoms, would force the methyl groups at these centers into close contacts with c e r t a i n hydrogen atoms on neighboring molecules and thus s t e r i c a l l y impede the reaction. For the same reason, twisting about the carbon-carbon double bond, which i s believed to accompany photoexcitation of a,f3-unsaturated ketones i n s o l u t i o n , 1 9 6 i s u n l i k e l y to be important i n the s o l i d state for enones 108a-108g. The s t e r i c hindrance to pyramidalization i s represented schematically i n F i g . 23. Methyl Group from Neighboring Molecule F i g . 23 The packing diagram indi c a t e d that s t e r i c hindrance to pyramidalization ( s t e r i c compression) was present i n a l l seven compounds studied. For enones 108 (a, b, c, e, f ) s t e r i c compression occurs upon pyramidalization at both Ca and Cp. One of the two exceptions to t h i s trend was the Ca methyl group of enone 108d, whose pyramidalization appeared to be unimpeded. Thus Scheffer et a l . concluded that i t i s the v o i d space surrounding the Ca methyl group of enone 108g which allows r e a c t i o n and pyramidalization at t h i s center i n contrast to the s t e r i c compression which would attend reaction and pyramidalization at - 171 Reaction of Cyclopropanol 54P with Potassium Hydroxide As part of exploring the properties of cyclopropanol 54P, we treated the t i t l e compound with a s o l u t i o n of 5% aqueous potassium hydroxide at r e f l u x . Two GC v o l a t i l e products were obtained. They were i d e n t i f i e d as the parent compound 54 and the rearrangement product 54L (Scheme 60) i n 87% and 0.5% GC y i e l d s r e s p e c t i v e l y . 0 Scheme 60 The formation of these two compounds can be understood i n terms of the formation of a homoenolate anion which can r i n g open e i t h e r to give 54 or 54L from the two possible paths 1 and path 2 (Scheme 61). The formation of 54L from 54P probably proceeds by r i n g opening to give enolate intermediate 54KE'. The intermediate enolate i s most l i k e l y trapped intramolecularly to give 54L'. The trapping of ketene interme-diates with nucleophiles i s well known. Aft e r workup, followed by a i r oxidation, 54L i s obtained. 172 f OH 54KE 5 4 L ' 54L Scheme 61 Attempted Synthetic C o r r e l a t i o n Between Lactone 54L and Ketoaldehyde 54KA Before we discovered the photochemical r e l a t i o n s h i p between 54KA and 54L ( i . e . 54KA n ^ > 54L), i t seemed important to confirm the struc-ture of 54L and 54KA unequivocally by e s t a b l i s h i n g a r e l a t i o n s h i p between them. Among several possible ways of achieving t h i s goal, we decided to follow the set of reactions given i n Scheme 62. For th i s purpose 54L was treated e i t h e r with a s o l u t i o n of sodium methoxide or sodium hydroxide at room temperature f o r 1 h. I t was found by GC 173 -analysis and t i c that the reaction was complete and a l l the s t a r t i n g material was consumed. A f t e r workup, i t was found that the i s o l a t e d product i s the same as the s t a r t i n g material i . e . no net r e a c t i o n has occurred. We i n t e r p r e t these r e s u l t s i n the following way: a f t e r the re a c t i o n of sodium methoxide with 54L, a ring-opened product 54E i s obtained. This product, during work up under a c i d i c or neutral conditions, c y c l i z e s to form 54L. There i s l i t e r a t u r e precedent for t h i s p r o c e s s . 2 2 5 ' 2 2 0 Fuchs et a l . 2 2 5 found that treatment of ketone 109 with sodium borohydride gives lactone 109L v i a intermediate 109E (Scheme 63) . 174 -( i i ) Photochemistry of 2-Methyl-cis-4a.9a.9.10-Tetrahydro-1.4- anthracenedione (48) 48 IUPAC numbering numbering used i n t h i s text to describe photochemistry Ene-dione 48 was prepared to study what e f f e c t the presence of a substituent at p o s i t i o n (2) has on the photochemistry of the unsubsti-tuted adduct 47 studied e a r l i e r . Photochemistry Photolysis (N 2 l a s e r , A 337 nm and 450 W lamp, A > 290 nm) of ene-dione 48 e i t h e r i n a KBr matrix or as pure c r y s t a l s f o r up to 6 h did not show any trace of reaction e i t h e r by GC, i r or t i c . - 175 -hv H b [27] H 0 48 48CB In contrast to the s o l i d state, t h i s compound reacted smoothly i n a c e t o n i t r i l e when photolyzed with a 450 W lamp (A >290 nm). The only photoproduct formed was i d e n t i f i e d as cyclobutanone 48CB (equation 27) by spectroscopy. Its i r spectrum shows two carbonyl peaks at 1770 and 1715 cm"1, assigned to the presence of the cyclobutanone and cyclohexa-none rings r e s p e c t i v e l y . The nmr spectrum features aromatic hydrogen mu l t i p l e t s at 6 7.29-7.11. M u l t i p l e t s at S 3.43 ( i n t e g r a t i o n 1H) and at 6 3.28 ( i n t e g r a t i o n 2H) are assigned to the methine hydrogens. An AB quartet (J = 17 Hz) at 5 3.01, which i s further s p l i t by the neighboring methine (J = 4 Hz) hydrogen, i s assigned to the methylenes at C(5), whereas another AB quartet (J = 18 Hz) at S 2.hi i s c r e d i t e d to the C(8) methylenes. The methyl s i n g l e t appears at 8 1.28. The mass spectrum at (m/e) 226 and a correct microanalysis also support the structure. S o l i d State Conformation of 48 Since the c r y s t a l structure of ene-dione 48 was not determined, exact conformation i n which t h i s compound finds i t s e l f i n the s o l i d state i s unknown. However, based on our e a r l i e r studies, there i s no - 176 reason to beli e v e that t h i s compound does not c r y s t a l l i z e i n the same "twist" conformations as a l l other ene-diones. So f a r , a l l the unsymme-t r i c a l ene-diones reported i n the present thesis and e l s e w h e r e 1 1 " 1 7 c r y s t a l l i z e e i t h e r i n conformation A or B (see pages 104 and 116 for example). The ene-dione 1 1 0 2 2 7 c r y s t a l l i z e s i n both conformations A and B, probably because i t contains no non equivalent bridgehead substitu-ents that can be e i t h e r pseudoaxial or pseudoequatorial, and the C(2) methyl group, presumably, contributes very l i t t l e to the molecular conformational energy; therefore, conformers A and B are isoenergetic. A s i m i l a r s i t u a t i o n could also be present i n the case of ene-dione 48. 110A HOB The u n r e a c t i v i t y of ene-dione 48 i n the s o l i d state means that the excited 48 has some e f f i c i e n t means of t r a n s f e r r i n g i t s energy and deactivating to ground state. The energy trans f e r leading to the deact i v a t i o n of the excited molecules i n the s o l i d state i s well known. 1 0 Without the X-ray c r y s t a l structure, i t i s not possible to say whether t h i s i s a c r y s t a l packing e f f e c t as speculated i n the case of o-quinodimethane/2,3-dimethyl-1,4-naphthoquinone adduct 54 or some other condition p e c u l i a r to the c r y s t a l l i n e state. Since both conformers 48A and 48B should be present i n s o l u t i o n i n - 177 an almost 1:1 mixture, both products 48CB and 48CB' (Scheme 64) are expected. However, 48CB i s the only photoproduct that i s observed. The formation of only product 48CB can be understood from the mechanism leading to the formation of the two products. The b i r a d i c a l 48BR has t e r t i a r y and secondary r a d i c a l centers, whereas 48BR' (Scheme 64) has two secondary r a d i c a l centers. Since a t e r t i a r y r a d i c a l i s more stable than a secondary r a d i c a l , the formation of 48CB i s preferred over 48CB'. 0 '0 48A 48B H(82) abstraction by C(3) H(51) abstraction by C(2) 0 "0 48BR 48BR' C(8)-C(2) bond formation C(5)-C(3) bond formation 0 0 0 0 48 GB 48CB Scheme 64 - 178 -The r e s u l t s shown i n Scheme 64 are i n sharp contrast to the photo-l y s i s of 2,3-dimethyl-l,3-butadiene/toluquinone adduct 110 i n sol u t i o n . In s o l u t i o n , the i r r a d i a t i o n of 110 leads to the formation of f i v e d i f f e r e n t photoproducts as expected i n a r a t i o dependent upon the solvent (Scheme 6 5 ) . ^ The mechanism of the reaction leading to a l l the photoproducts shown i n Scheme 65 involves /3-hydrogen abstrac t i o n by oxygen through the n , 7 r excited state. However, the t r i c y c l i c product 48CB i n the present study a r i s e s almost c e r t a i n l y from a IT,IX state, and no products corresponding to the f i v e photoproducts shown i n Scheme 65 were observed 110EA* 110CP" Solvent 110EA 110CP 110CP' 110EA' 110CP" Benzene 38 1 26 34 -t-BuOH 1 9.6 - 3 1 Scheme 65 179 i n s o l u t i o n . This contrasting r e a c t i v i t y of ene-dione 48 i s probably due to an excited state i n t e r a c t i o n of the aromatic group with ene-dione chromophore. The i n t e r a c t i o n probably leads to the s t a b i l i z a t i o n of the 7r,7r t r i p l e t state compared to the n,ix J state and therefore, the photochemical r e a c t i o n i s observed e x c l u s i v e l y from n,TT j state. S i m i l a r observation of the i n t e r a c t i o n of 6,7-ene-double bond with the ene-dione chromophore was also made by Scheffer et a l . , 7 ^ Baltrop et a l . , 1 7 ^ and Cookson et a l . , 1 " 2 during the photochemical in v e s t i g a t i o n s of ene-diones discussed e a r l i e r . These r e s u l t s are also consistent with the observations made e a r l i e r during the photolysis of benzoquinone/o-quinodimethane adduct 47 and 2,5-dimethyl benzoquinone/quinodimethane adduct 49c where the products observed came e x c l u s i v e l y from the n,n state. - 180 -CHAPTER 3 PHOTOCHEMISTRY OF ANTHRAQUINOLS Four compounds i n the anthraquinol category were studied. They have been further divided into two subsections depending on t h e i r r e a c t i v i t y i n the s o l i d state with respect to s o l u t i o n . (a) Enones that react s i m i l a r l y i n the s o l i d state and s o l u t i o n (b) Enones that react d i f f e r e n t l y i n the s o l i d state and s o l u t i o n (a) Enones That React S i m i l a r l y i n the S o l i d State and Solution 1. Photochemistry of 4a.9a.9.10-Tetrahydro-4fl-(acetvloxv)-2.3.UaB,9aB- tetramethyl-1(4H)anthraceneone (58B) 0 0 OAc OAc 5 8 B IUPAC numbering numbering used here to describe photochemistry I r r a d i a t i o n (A >290 nm) of anthraquinol 58B with a 450 W lamp i n a KBr p e l l e t and as a pure c r y s t a l at room temperature as well as at 181 --40°C, and i n CH3CN s o l u t i o n caused the formation of only one photo-product i d e n t i f i e d as 58BS (equation 28). The structure of the photoproduct 58BS i s assigned from the following spectroscopic data: i t s i r spectrum features cyclobutanone and acetate C=0 peaks at 1764 and 1738 cm"! r e s p e c t i v e l y . Its nmr spectrum features aromatic m u l t i p l e t s at 6 7.34-6.97, a C(7) methine doublet (J = 6 Hz) at S 4.90, a benzylic hydrogen AB quartet (J = 17 Hz) at 2.82, and a C(2) methine s i n g l e t at S 2.52. The methyl s i n g l e t of the acetate appears at 5 2.05 and the C(8) methine m u l t i p l e t comes at 5 2.10. The remaining methyls appear at 5 1.16 (s ) , 1.14 (s ) , 1.03 (s) and 0.73 (d, J = 8 Hz). The mass spectrum and microanalysis are also favorable f o r C ^ Q ^ ^ S -S o l i d State Conformation of 58B The X-ray d i f f r a c t i o n i n v e s t i g a t i o n of a sing l e c r y s t a l of 58B revealed that t h i s molecule c r y s t a l l i z e s i n a conformation i n which the b u l k i e r acetate group at C(4) occupies the more s t e r i c a l l y favored pseudo-equatorial p o s i t i o n (Fig. 24) i n accord with the p r i n c i p l e that 182 -organic molecules generally c r y s t a l l i z e i n t h e i r most stable conforma-t i o n . 1 6 8 The conformation of 58B i s very s i m i l a r to that of acetate 111B. 2 2 8 The conformation i n which enones 58B and 111B c r y s t a l l i z e i s r e f e r r e d to as conformation B shown i n Scheme 66. Conformation B (as well as A) can be described as c o n s i s t i n g of a h a l f - c h a i r cyclohexene r i n g c i s - f u s e d to a h a l f - c h a i r l i k e cyclohexenone moiety. OAc 111B Fig. 24 A h a l f c h a i r - t o - h a l f - c h a i r r i n g f l i p interconverts A and B, which are rendered non-equivalent by v i r t u e of the f a c t that the substituents at C(4) are non-equivalent and also by the f a c t that the C(4) substitu-ent i s pseudo-equatorial i n one conformer and pseudoaxial i n the other. - 183 -I t has been w e l l established 1''- 5 by conformational analysis as well as by X-ray crystallography that the C(4) substituent i n naphthoquinols determines the preferred conformation i n the s o l i d state. With the c r y s t a l l o g r a p h i c data i n hand, the mechanism of the rea c t i o n i n the s o l i d state can be r a t i o n a l i z e d . Since H(81) points d i r e c t l y at the enone C=C bond, hydrogen atom abstrac t i o n by the top lobe of the /3-carbon atom of the a,3-unsaturated ketone chromophore takes place through a six-membered t r a n s i t i o n state to give b i r a d i c a l 58BR (Scheme 66). This establishes the stereochemistry at t h i s center Scheme 66 58BS - 184 -i n the f i n a l product. The C(8) and C(2) r a d i c a l centers of 58BR then combine to give 58BS. There are a number of l i t e r a t u r e examples demonstrating photochemical hydrogen atom abstraction by o l e f i n i c carbon I I S ? 9 Q 9^1 T Q 1 atoms through six-membered t r a n s i t i o n s t a t e s . i i J , i i ' " i J X , J - 3 i For example, Agosta and coworkers have demonstrated hydrogen abstraction reactions by the /3-carbon atoms of a v a r i e t y of cyclopentanones 2^ (page 111) as discussed e a r l i e r . There are reports which suggest that H-transfer can occur also at the a-carbon i n s o l u t i o n 2 - ^ 2 a n c j i n the s o l i d s t a t e i l J . There i s one r e p o r t " 0 i n which abstrac t i o n by both the a and the /S-carbon has been found to take place i n the same molecule. Scheffer et a l . ^ - * have also observed H-atom abstraction by the ^-carbon atom i n the photolysis of enones. Hydrogen atom abstraction by the /9-carbon i s normally preferred over abstra c t i o n by the a-carbon due to the greater s t a b i l i t y of the b i r a d i c a l formed i n the former process. The s o l i d state photolysis product obtained i n the present study i s analogous to the s o l i d state photoproduct obtained by Walsh^O during the photolysis of enone 111B (Scheme 67). In contrast to the s o l i d state r e s u l t s the s o l u t i o n photochemistry of 111B i s very d i f f e r e n t from 111B H i d H2 Scheme 67 185 that of 58B (Scheme 67). The photolysis of naphthoquinol acetate 111B i n s o l u t i o n (Scheme 67) affords intramolecular [2+2] c y c l o a d d i t i o n ( l l l d ) and hydrogen abs t r a c t i o n (112 ) products. The formation of both s o l u t i o n products mentioned above requires the p a r t i c i p a t i o n of the 6,7-alkene double bond. In the case of 58B, the 6,7-double bond i s replaced by an aromatic r i n g , and therefore, intramolecular [2+2] dimerization requires d i s r u p t i o n of aromaticity. For t h i s reason, products analogous to l l l d and 112 do not form i n the present example. Benzylic hydrogen atom abstraction by the C=0 oxygen i s not allowed i n the s o l i d state because the distance between the C=0 -• -H(81) i s l a r g e r than the upper l i m i t (2.7 A ) 7 2 for such processes. The hydrogen atom ab s t r a c t i o n by C=0 oxygen, which can occur from the lowest n,7r* state, i s also disfavored i n s o l u t i o n . I t i s because a l k y l s u b s t i t u t i o n at Ca and of enones causes l o w e r i n g 1 9 0 of n,n* excited state energy compared to n,7r*. In analogy to other studies on e n o n e s , 1 1 5 • 1 9 ° we also suggest that i t i s the t r i p l e t state that i s involved i n hydrogen atom abs t r a c t i o n by the y9-carbon atom of 58B. This suggestion i s supported by a s e n s i t i z a t i o n study, which shows that i n the presence of acetone as a solvent and s e n s i t i z e r , 58BS i s the only product formed (also see the d i s c u s s i o n towards the end of t h i s chapter). - 186 -2. Photochemistry of 4a, 9a, 9,10-Tetrahydro-4/3-hydroxy-2, 3 , 4a/3, 9a£-tetramethyl-l(4H)anthracenone (56B) IUPAC numbering 5 6 B numbering used here to describe photochemistry Photolysis (A >290 nm) of enone 56B with a 450 W lamp e i t h e r i n a KBr matrix or as a pure c r y s t a l and i n a c e t o n i t r i l e r e s u l t s i n the formation of 56BK i n e s s e n t i a l l y quantitative chemical y i e l d (quantum y i e l d •= 0.04) (equation 29). The structure of the photoproduct was assigned on the basis of the following spectroscopic data: i t s i r spectrum shows a strong OH peak at 3272 cm"1. The ^H nmr spectrum of t h i s compound features resonances as expected, (and are reported i n the Experimental section) except the C(7) s i n g l e t at 5 3.28 and the C(8) quartet at 6 1.58. I f the above structure of 56BK i s correct, then the 187 s i n g l e t at 8 3.28 should be a doublet and the quartet at 8 1.58 should display an e i g h t - l i n e pattern. In order to understand the lack of expected coupling, a molecular model was constructed. The molecular model of 56BK shows that the angle between the C(7) and C(8) methine hydrogens i s -90°. The v i c i n a l coupling depends on the H-C-C-H dihedral 1 4ft angle, ^° and as the Karplus curve shows that at -90° dihedral angle, the coupling (J) i s 0-1 Hz. Therefore, not s u r p r i s i n g l y , v i c i n a l coupling i s not observed. The structure of t h i s compound i s also supported by i t s mass spectrum and correct microanalysis. Strong support for t h i s structure came from an independent synthesis as given i n equation 30. The formation of 56BK takes place v i a an intermediate 561 which undergoes hemiketal formation immediately under the reaction conditions. Hemiketal formation i n enone photochemistry has l i t e r a t u r e precedent, both i n the s o l i d state as well as i n s o l u t i o n . For example, Scheffer et a l . 1 1 5 found that the photolysis of naphthoquinol 46B leads to the formation of hemiketal type photoproducts, both i n the s o l i d state and i n s o l u t i o n (Scheme 68). 188 Scheme 68 Since the proposed mechanism of the formation of 56BK from 56B i s i d e n t i c a l to the formation of 58BS from 58B (Scheme 66), i t w i l l not be discussed any further. Although no X-ray d i f f r a c t i o n studies were performed to determine the conformation of 56B i n the s o l i d state, i t almost c e r t a i n l y c r y s t a l l i z e s i n conformation B (Scheme 66). - 189 -(b) Enones that React D i f f e r e n t l y i n the S o l i d State and i n Solution 1 • Photochemistry of 4a. 9a, 9 .10-Tetrahydro-4a-hydroxy-2 . 3 . haB. 9a/3- tetramethyl-1(4H)anthraceneone (57A) IUPAC numbering OH numbering used here to 5 7 A describe photochemistry UV i r r a d i a t i o n (A >290 nm) with a 450 W lamp of enone 57A, ei t h e r i n a KBr matrix or as a pure c r y s t a l , l e d to the formation of 57AS (equation 31). During the photolysis i t was noted that, as the amount of the r e a c t i o n i n the c r y s t a l was increased, the c r y s t a l melted and another product was formed (see Table 9a). The second photoproduct was l a t e r found to be a c t u a l l y the major s o l u t i o n photoproduct 57AL. The s o l i d state photoproduct, 57AS, features the following spectroscopic properties: i t s i r spectrum shows an OH peak at 3449 cm*1 and a C=0 s t r e t c h at 1724 cm"1. The C=0 peak at 1724 cm"1 i s about 10 cm"1 lower than the 'normal' C=0 s t r e t c h i n a KBr matrix for a five-membered r i n g ketone. However, the st r e t c h i n g frequency at 1724 cm"1 i s i n t e r n a l l y consistent with the other cyclopentanone photoproducts 113, 114, 115 and 116 (Scheme 69) i s o l a t e d by Scheffer et a l . 1 1 - ' The proton nmr spectrum of t h i s compound displays aromatic multiplets at S 7.19-6.56 (4H). The m u l t i p l e t at 6 3.74 i s coupled to the doublet (J = 4.5 Hz) at <5 1.77 and - 190 -% Conversion % 57AS % 57AL <2 only product 0 3.1 3.0 0.1 23.0 21.5 1.4 85.5 80.4 5.1 -0 :--H 'OH OH 6H 114 115 1720 1720 116 1725 Scheme 69 - 191 are assigned to the C(10) methine and OH re s p e c t i v e l y . A f t e r hydrogen/ deuterium exchange using D2O, the doublet at 6 1.77 disappears, whereas the m u l t i p l e t at 6 3.74 appears as a broad s i n g l e t . An eight l i n e pattern at 8 1.85 i s assigned to the C(9) methine, whereas the s i n g l e t at 8 2.96 i s assigned to the benzylic methine. An AB quartet (J = 17 Hz) at 8 2.75 i s assigned to the benzylic methylenes. Methyl groups i n the molecule appear at 8 1.03 (a fo r t u i t o u s s i n g l e t , 2 x CH3), 0.94 (d, J = 7 Hz), and a s i n g l e t at 8 0.86. The mass spectrum and microanalysis also support the structure. The structure of the photoproduct (57AS) was strongly supported by i t s oxidation with pyridinium chlorochro-m a t e 2 3 4 to a known compound 52CP characterized e a r l i e r (see page 124) (equation 32). Similar oxidations have been used by Scheffer et a l . 1 1 5 to e s t a b l i s h the structures of ketoalcohols. A representative example i s shown i n equation 33. The substrate 57A was also photolyzed i n a c e t o n i t r i l e with a Hanovia 450 W lamp at A >290 nm. A GC analysis of the r e a c t i o n mixture revealed the formation of two photoproducts i n the r a t i o of 92:8. The minor product was i d e n t i f i e d as the s o l i d state photoproduct 57AS 192 -(discussed above), whereas the major product was a new product 57AL (Scheme 70). The spectroscopic properties of 57AL are given i n the Experimental section. Once again a strong proof of the structure of 57AL came from oxidative studies as shown below. 52CB In contrast to the photoproduct that r e s u l t e d from the photolysis of 56B, 57AL and 57AS do not form the hemiketal. The reason i s obvious. The stereochemistry at C(7) i n 57AS and 57AL i s opposite to the C(7) stereochemistry i n 56BK (equation 32), and therefore intramolecular hemiketal formation i s impossible. The example shown i n Scheme 70 i s the f i r s t example where photoproducts from both conformations A and B have been i s o l a t e d from the same enone. 193 -HOv " O H 57A H51 abstraction by C3 no reaction 57BR' H O H H 57B H81 abstraction by C3 57BR C5-C2 bonding C8-C2 bonding 57AS 57AL Scheme 70 With the s o l i d state i r r a d i a t i o n r e s u l t s i n hand, i t can be deduced that enone 57A must have c r y s t a l l i z e d i n the conformation A i n such a way that the hydroxyl group i s pseudo-equatorial. In order to confirm t h i s speculation, X-ray d i f f r a c t i o n studies were performed on a single c r y s t a l of enone 57A. - 194 -S o l i d State Conformation X-ray crystallography revealed that the enone 57A c r y s t a l l i z e s i n the conformation common to a l l the naphthoquinols s t u d i e d , 1 1 5 i . e . the b u l k i e r hydroxyl group at C(4) assumes the less hindered pseudo-equatorial p o s i t i o n (conformation A). Furthermore, the conformation about the C(4a)-C(8a) bond i s twisted such that the bridgehead methyl groups are staggered. One of the s p a t i a l consequences of t h i s arrange-ment i s the proximity of the enone /?-carbon to the endo-benzylic hydrogen (H51), and therefore (H51) i s i d e a l l y suited f o r a b s t r a c t i o n by t h i s atom (Fig. 25). The abstraction, which occurs through a f i v e -F i g . 25: membered t r a n s i t i o n state, r e s u l t s i n b i r a d i c a l 57BR'; the C(2) and C(5) r a d i c a l centers of 57BR' then combine to form the photoproduct 57AS (Scheme 70). In s o l u t i o n , however, the s i t u a t i o n i s very d i f f e r e n t . Since the conformational equilibrium i s f a c i l e , a l l three d i s t i n c t conformers - 195 -A C ^  B are present i n s o l u t i o n (Scheme 70). Therefore, products from a l l three conformations can a r i s e . As stated e a r l i e r i n the case of 58B (Scheme 66), the [2+2] intramolecular dimerization product, which may r e s u l t from conformation 'C, i s not favored i n the present example as well, due to the presence of an aromatic r i n g . Out of the remaining two conformers present i n solut i o n , products from both conformers a r i s e . The r e s u l t s obtained can be analyzed i n terms of the Curtin-Hammet 1 on principle- 1--^ and probably suggest that the rea c t i o n v i a a six-membered t r a n s i t i o n state (from conformation B) i s k i n e t i c a l l y p r e f e r r e d over the rea c t i o n through a five-membered t r a n s i t i o n state (from conformation A) i n s o l u t i o n . Thus, the photoproduct 57AL ar i s e s from the higher energy conforma-t i o n B (Scheme 70). Hydrogen atom (H81) abstrac t i o n by the enone /9-carbon through a six-membered t r a n s i t i o n state r e s u l t s i n 57BR. Then the C(2) and C(8) r a d i c a l centers of 57BR combine to give the product 57AL. S e n s i t i z a t i o n studies were also c a r r i e d out which support the suggestion that i t i s t r i p l e t state of the enone which i s involved i n the hydrogen atom abstraction. We suggest that the t r i p l e t i s most l i k e l y a n,n J state i n the case of 57A. As discussed e a r l i e r , H-abstraction by oxygen i s once again not favored due to the e f f e c t of the methyl substituents on the enone carbon carbon double bond i n lowering the excited state energy of the (7r,7r*)^  compared to (n,7r*)^  s t a t e . 1 9 6 196 -2 . Photochemistry of 4a. 9a. 9 . lO-Tetrahydro-4/9-hydroxv- 2 . 3 . 4a, kaB. 9a/3- pentamethvl-1(4H)anthracenone (59A) IUPAC numbering 59 A numbering used here to describe photochemistry I r r a d i a t i o n (A >290 nm, 450 W lamp) of c r y s t a l s of 59A i n a KBr matrix or as pure c r y s t a l s r e s u l t e d i n the formation of only one product 59AS (equation 34). As i n the case of other s o l i d state reactions, with an increase i n the amount of reaction, the c r y s t a l melts and a second photoproduct can be observed (see Table 9b). The l a t t e r product was a c t u a l l y found to be the s o l u t i o n photoproduct. The i r s t r e t c h of the C=0 group which appears at 1724 cm"1 i s rather low for a cyclopentanone, but as discussed e a r l i e r (see page 190), i t i s consistent with the C=0 str e t c h i n g frequency of other cyclopentanone type photoproducts obtained i n t h i s study and e l s e w h e r e . 1 1 5 The remaining s p e c t r a l data f o r 59AS i s given i n the Experimental section. 59A 59AS - 197 Table 9b % Conversion % 59AS % 59AL <4 only product 0 5.1 5.0 0.1 23.5 22.7 0.8 94.3 91.4 4.9 Wostradowski 1- 3 has shown that, on treatment with base, dike tone 38CP undergoes a deuterium exchange i n the presence of deuterated solvents as shown below. 38CP I t was thought that the same method could be used to d i f f e r e n t i a t e 59AS from i t s possible regioisomer 59AS'. Since no exchange could 59AS1 - 198 -be observed by nmr or mass spectrometry, i t can s a f e l y be assumed that the assigned structure of 59AS i s correct. Enone 59A was also photolyzed (A >290 nm) i n a c e t o n i t r i l e with a 450 W lamp. A GC analysis of the rea c t i o n mixture showed that two products formed i n the r a t i o of 92:8. The minor product was the s o l i d state photoproduct 59AS. The major product was i d e n t i f i e d as 59AK (Scheme 71) by the spectroscopic data given i n the Experimental section. 59AK (92%) Scheme 71 In many ways, the s o l u t i o n and s o l i d state photochemistry of 59A p a r a l l e l s the r e a c t i v i t y of anthraquinol 57A (Scheme 70) and naphthoqui-nol 117A-'--'-5 (Scheme 72). Comparing the photochemistry of 57A and 59A, both compounds give analogous products i n the s o l i d state and so l u t i o n . I n t e r e s t i n g l y , i n s o l u t i o n the r a t i o of the s o l i d state to s o l u t i o n - 199 hi/ solut ion 117AL 117A hy crystal H-o 117AS 117AK Scheme 72 products i s e s s e n t i a l l y i d e n t i c a l (10:90). The photochemistry of anthraquinol 59A i s s i m i l a r i n some ways to that of naphthoquinol 117A. In both compounds, the stereochemistry of the OH group i n the product i s such that hemiketal formation should be observed. In f a c t , i n both cases, the s o l u t i o n photoproducts form hemiketals, but the s o l i d state products do not. This difference i n r e a c t i v i t y towards hemiketal formation could be because of two fa c t o r s : 1) cyclobutanone i s more reac t i v e towards hemiketal formation than a five-membered r i n g ketone. 2) The distance between the OH group and C=0 group i s r e l a t i v e l y smaller f o r cyclobutanone than f o r cyclopentanone as estimated from the molecular model. A s i m i l a r distance explanation was given by Scheffer et al.115 to explain the i n a b i l i t y of the cage compound 118 to engage i n hemiketal formation. - 200 -118 S o l i d State Conformation The anthraquinol 59A c r y s t a l l i z e d i n the same conformation common to a l l anthraquinols and naphthoquinols s t u d i e d , 1 1 5 i n which the b u l k i e r substituent at C(4) assumes the pseudo-equatorial p o s i t i o n (conformation A) ( F i g . 26). An i n t e r e s t i n g feature of t h i s molecule i s that the C(4a) methyl and the C(4)-0H groups have a syn-relationship unlike i n enone 57A where they are a n t i . In s p i t e of the opposite o r i e n t a t i o n of the hydroxyl groups at C(4), both compounds adopt s i m i l a r conformations i n the s o l i d state. The reason i s obvious; the methyl group i s the b u l k i e r of the two groups at C(4) and therefore occupies the less F i g 26 201 -hindered pseudo-equatorial p o s i t i o n . The mechanisms proposed f or the formation of 59AS and 59AK (Scheme 73) are p a r a l l e l to the mechanisms leading to 57AS and 57AL as discussed e a r l i e r . H. LOR' A Preferred s o l i d state H51 abstraction conformation f o r 57A, 59A by C3 no r e a c t i o n H81 abstraction by C3 B Preferred s o l i d state conformation f o r 56B, 58B BR BR C5-C2 bonding C8-C2 bonding Scheme 73 S o l i d State vs Solution R e a c t i v i t y f o r Enones So f a r , a l l four enones investigated i n the present study c r y s t a l -- 202 l i z e i n conformation A (59A and 57A) or conformation B (56B and 58B). A l l four enones react i n the s o l i d state and s o l u t i o n v i a hydrogen atom abstract i o n by the /9-carbon atom (Scheme 73). None of the compounds i n the present study react v i a conformation 'C i n s o l u t i o n . Conformation 'C has been suggested to be responsible f or the exclusive [2+2] i n t r a -molecular c y c l o a d d i t i o n of naphthoquinols leading to the cage compounds observed by Scheffer et a l . 1 1 - * The reason for the lack of formation of the cage compounds i n the case of the anthraquinols (Scheme 73) i s the presence of an aromatic r i n g i n place of the 6,7-ene bond of naphthoqui-nols. The question a r i s e s : why are cyclobutanone type photoproducts a r i s i n g from conformation B favored i n s o l u t i o n f or a l l four enones investigated i n s p i t e of the f a c t that anthraquinols 59A and 57A y i e l d e x c l u s i v e l y cyclopentanone type products i n the s o l i d state? The exclu-sive formation of cyclobutanone type photoproducts i n s o l u t i o n f or 59A and 57A can be r a t i o n a l i z e d i n terms of the Curtin-Hammett p r i n c i p l e 1 - ^ 9 as stated e a r l i e r . In order to further confirm the suggestion that i t i s the t r i p l e t excited state that i s involved i n hydrogen atom ab s t r a c t i o n by the /3-carbon atom of enone (59A), photolysis was c a r r i e d out i n acetone, a t r i p l e t s e n s i t i z e r (E^ =78 k c a l / m o l e 1 9 1 ) under conditions where most of the l i g h t was absorbed by acetone. A f t e r GC analysis of the reaction mixture, i t was found that the r a t i o of photoproducts remained essen-t i a l l y the same (92%:8%) i n the presence of acetone as i n the d i r e c t p h o t o l y s i s , i n d i c a t i n g thereby that i t i s the t r i p l e t state which i s involved i n hydrogen atom abstraction from both conformations. 203 -CHAPTER 4 PHOTOCHEMISTRY OF DIENONES Professor H.-J. L i u of the U n i v e r s i t y of Alberta has prepared a number of c r y s t a l l i n e Diels-Alder adducts such as 119 and 120 shown below. We decided to investigate the p o s s i b i l i t y of carr y i n g out conformation-specific photochemistry with these compounds i n the s o l i d state 236 A c O C H 2 o E=COOMe 119 120 (1) Photochemistry of 4,4,8a-Trimethyl-8a^-carbomethoxy-cis-4a,5,8,8a-tetrahydro-l(4H)naphthalenone ( 1 1 9 ) 2 2 3 > 2 2 4 I r r a d i a t i o n (A >290 nm) of naphthalenone 119 with a 450 W lamp i n benzene r e s u l t e d i n the formation of only one compound i n 80% y i e l d i d e n t i f i e d as the intramolecular [2+2] cy c l o a d d i t i o n product 119d. The spectroscopic properties of 119d are as follows:' the i r spectrum of t h i s compound features carbonyl absorptions at 1745 cm"-'- and 1720 cm"1, assigned to the cyclopentanone and ester carbonyls respec-- 204 -o E 7 3 2 Benzene *v, 290 8 4 o E=COOMe 119 119d t i v e l y . An 80 MHz nmr spectrum features a s i n g l e t at 6 3.80 assigned to the methyl of an ester group, and mu l t i p l e t s at 6 3.06 (1H), 2.75-2.12 (5H), 1.82 (1H), and 1.65 (1H). Two C(5) methyl s i n g l e t s appear at 6 1.30 and 0.78, and the C(10) methyl appears as a doublet (J = 7 Hz) at 6 0.86. The methyl s i n g l e t at 6 0.87 i s embedded i n the C(8) methyl doublet i n such a way that they show three l i n e s . Low and high resolu-t i o n mass spectra also support the above structure. In the benzene photolysis, the p o s s i b i l i t y of the formation of photoproducts 121 and 122 also e x i s t s . Photoproduct 121 may a r i s e by 7-hydrogen atom abstrac t i o n by oxygen through a six-membered t r a n s i t i o n state (Norrish type II r e a c t i o n 1 8 5 ) followed by coupling of the b i r a d i c a l s . The t r i c y c l i c product 122 may be obtained v i a e n d o - a l l y l i c o E=COOMe 121 E=COOMe 122 205 -C(5) hydrogen atom abstraction by the /3-carbon atom of the enone chromophore followed by bonding between the r a d i c a l centers. Both of the processes suggested above have l i t e r a t u r e p r e c e d e n t 1 8 5 ' 1 9 6 and are discussed i n the Introduction section and also i n Chapter 3 of the Results and Discussion. That the two possible products do not form i s c l e a r l y evident i n the nmr spectrum of the crude re a c t i o n mixture, which does not show v i n y l i c protons. I t should also be pointed out here that C(8) /9-hydrogen atom abstraction by oxygen i s impossible for 119 because t h i s hydrogen i s a n t i to the carbonyl group. Cr y s t a l s of enone 119 were also photolyzed at -16° to -18° (to prevent melting) with a He-Cd la s e r (>325 nm). Even a f t e r 20 h of p h o t o l y s i s , no photoproducts could be detected by GC, t i c or i r spectro-scopy . S o l i d State Conformation and Packing Arrangement The X-ray c r y s t a l l o g r a p h i c i n v e s t i g a t i o n 2 - ^ 7 revealed that enone 119 c r y s t a l l i z e s i n the now-familiar twist conformation. I t also revealed that the h a l f - c h a i r cyclohexene r i n g i s c i s - f u s e d to the h a l f - c h a i r cyclohexenone r i n g , and that the bridgehead ester moiety and C(8) methyl are pseudo-equatorial with respect to the cyclohexene r i n g ( F ig. 27). The s p a t i a l consequence of t h i s arrangement i s the proximity of the enone /3-carbon, C(3), to H(52). The o v e r a l l s o l i d state conformation of t h i s molecule i s very s i m i l a r to that found i n other enones (see Chapter 3) discussed e a r l i e r . A notable feature of the packing arrangement of - 206 -5 1 E=COOMe F i g . 27 enone 119 i s that the centrosymmetrically r e l a t e d molecules X and X (Fig. 28) are i d e a l l y s i t u a t e d to undergo [2+2] intermolecular photo-dimerization. The p o t e n t i a l l y reactive enone double bonds are p a r a l l e l , above one another, and the center to center distance i s 3.8 A. From the work of Schmidt and coworkers 8 5 on the s o l i d state photodimerization of cinnamic acids (see the Introduction section for d e t a i l s ) , i t i s c l e a r that i n a c r y s t a l packing arrangement of p a r a l l e l double bond with center-to-center distances of 4.1 A or l e s s , the intermolecular [2+2] F i g . 28: Packing diagram of enone 119 207 -photocycloaddition i s v i r t u a l l y i n e v i t a b l e . We were thus surprised to observe the complete lack of r e a c t i v i t y of enone 119 i n the s o l i d state. That lack of r e a c t i v i t y i s not an i n t r i n s i c property of enone 119 i s shown from i t s re a c t i o n to i n benzene to y i e l d cage compound 119d (vide supra). What i s the source of the lack of r e a c t i v i t y of enone 119 i n the s o l i d state? The most l i k e l y reason we f e e l comes from the packing diagram shown i n F i g . 28. We suggest that as the p o t e n t i a l l y reactive molecules X and X s t a r t to move towards one another i n the i n i t i a l stages of [2+2] dimerization, each molecule experiences in c r e a s i n g l y severe s t e r i c compression of two of i t s methyl groups [dotted l i n e s i n F i g . 28]. A noticeable point here i s that the s t e r i c compression i s not between the p o t e n t i a l reactants X and X, but between X and Y and X and Y. The r e t a r d a t i o n of photodimerization by Y and Y i s analogous to the i n h i b i t i o n of cyclopropanol formation i n naphthacenedione 54 by stationary l a t t i c e neighbors (see Chapter 2). I t i s thus another instance of " s t e r i c compression c o n t r o l " . Computer Simulation of Photodimerization In order to t e s t the v a l i d i t y of the ideas suggested above, Dr. S. A r i e l of our group d i d a computer simulation of the s o l i d state [2+2] photocycloaddition. Two mechanisms were considered: 1. "Center-to-Center" photodimerization mechanism; 2. "Twist" photodimerization mechanism. - 208 1. "Center-to-Center" Photodimerization Mechanism Two r e a c t i o n pathways were considered: (a) Dual motion mechanism: molecules X and X move towards one another i n 0.24 A increments along the double bond center-to-center vector; (b) Single motion mechanism: molecule X remains stationary while molecule X moves i n 0.48 A incre-ments along the same vector as above. In both cases, the coordinates of molecules Y and Y were kept unchanged during the hypothetical dimeriza-t i o n . The new hydrogen-hydrogen contacts were then determined at each stage of dimerization. The r e s u l t s are shown i n F i g . 29. 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 Center to Center Double Bond Distance (A) F i g . 29: 209 -I t i s evident from F i g . 29 that, i n the s i n g l e as well as i n the dual motion mechanisms, the non-bonded repulsion energy i s quite s i g n i f -icant. For example, at a center-to-center double bond distance of 2.35 A, the hydrogen-hydrogen contact i s 1.9 A, and the t o t a l MM2 (non-bonded repulsion energy) i s 13.2 kcal/mole. At t h i s geometry, 2p-2p o r b i t a l overlap, estimates Dr. A r i e l , i s l e s s than 20% of maximum. Any further movement of X and X, which i s required i f [2+2] c y c l o a d d i t i o n i s to occur, causes the non-bonded repulsion energy to become very high, and therefore no [2+2] intermolecular dimerization i s observed. The d i f f e r e n c e i n the hydrogen-hydrogen repulsion energy i n the si n g l e and dual motion dimerizations (Fig. 29) i s explained with the help of F i g . 30, which i s an i d e a l i z e d drawing of the packing arrange-ment f o r dienone 119 showing the methyl-methyl i n t e r a c t i o n s . F i g . 29 suggests that the sum of the four i n t e r a c t i o n s developed i n moving both reactants towards each other by a distance d i s l e s s than the sum of the two severe i n t e r a c t i o n s which r e s u l t when one of the reactants i s moved towards the other by a distance of 2d. 2. "Twist" Photodimerization Mechanism Two such mechanisms were considered: (a) Molecules X and X are each rotated around the intramolecular CI•••C4 vector i n 5° i n t e r v a l s (dual "twist" mechanism) and (b) molecule X remains • f i x e d while X i s rotated around i t s C1---C4 vector i n 5° i n t e r v a l s (single "twist" mechanism). The i d e a l i z e d drawing of the packing arrangement for 210 -compound 119 relevant for twist mechanism i s shown i n F i g . 31. At a 20° counter-clockwise twist, estimates Dr. A r i e l , the center-to-center distance decreases from 3.8 A to 3.2 A and the 2.3 A H-•'H intermole-cular constants are decreased to 1.6 and 1.7 A. At t h i s distance the F i g . 30: F i g . 31 t o t a l 6-12 repulsion energy i n 52.8 Kcal/mole. At the same time the o f f s e t between the 2p o r b i t a l s increases from 1.8 A to 2.7 A, a less favored geometry f or dimerization. In the case of s i n g l e motion "twist" mechanism i n which X i s f i x e d while only "X i s rotated around the C1---C4 vector, the p a r a l l e l i s m of the 2p o r b i t a l s i s l o s t , a condition necessary f o r dimerization. As before the o v e r a l l conclusions are not al t e r e d when rotations of the i n t e r a c t i n g methyl groups are taken into account. The formation of the t r i c y c l i c product of structure 121 i s not allowed i n the s o l i d state. The reason i s that a f t e r methyl 7-hydrogen - 211 atom abstrac t i o n by carbonyl oxygen, the b i r a d i c a l 119BR, i f formed, cannot collapse at the b i r a d i c a l centers C(3) and C(9) to form the product 121. The distance between the C(9) and C(3) r a d i c a l centers i s 4.5 A and i s more than has been ever observed i n the s o l i d state (up to 3.7 A ) . 2 2 7 The formation of t r i c y c l i c product 122 i s disfavored on s t e r i c grounds. We f e e l that because of the two methyl groups present at C(4), abstra c t i o n of H(51) by C(3) i s s t e r i c a l l y hindered by the methyl group C(42) [the H(42)...H(51) distance i s 2.2 A]. 121 E=COOMe 119 In s o l u t i o n the re a c t i o n must take place from conformation 'C (Scheme 74). In order to account for the [2+2] intramolecular dimeriza-t i o n as the sole product, i t must be that the a c t i v a t i o n energy for formation of adduct 119d i s much lower than the formation of products from conformation A or B. A s i m i l a r explanation was also given by Scheffer et a l . 1 1 5 • 7 2 to explain the complete dominance of [2+2] intramolecular dimerization i n the photochemical in v e s t i g a t i o n s of cyclohexenone 46A and naphthoquinol 46B (Scheme 28). D e t a i l s of t h i s work by Scheffer et a l . 1 1 5 have already been elaborated e a r l i e r and are given i n d e t a i l i n the Introduction section. - 212 -E=COOMe Exclusive s o l i d state conformation H9d Scheme 74 (2) Photochemistry of 4,4,7-Trimethyl-8a/3-carbomethoxy-8a-acetyloxy-methyl-cis-4a,5,8,8a-tetrahydro-l(4H)naphthalenone (120) Photolysis (A >290 nm) of naphthalenone 120 with a 450 W lamp i n benzene r e s u l t e d i n the formation of only one compound i d e n t i f i e d as the intramolecular [2+2] cyc l o a d d i t i o n product 120d. The spectroscopic properties of 120d are as follows: i t s i r spectrum shows a poorly resolved broad peak at 1740 cm'^ assigned to the carbonyl groups of the ester, acetate and cyclopentanone moieties. An 80 MHz nmr spectrum of - 213 AcOCHa O E A c O C H 2 4 ^ 0 Benzene 7 E=COOMe 120 120d the adduct features a mu l t i p l e t ( i n t e g r a t i o n 2H) at 5 3.98 assigned to -CH^OAc u n i t i n the molecule. This m u l t i p l e t should be, i n p r i n c i p l e , an eight l i n e pattern because the two methylene hydrogens are non-equivalent. They are next to an asymmetric center and therefore are coupled to one another. Both of the methylene hydrogens are further coupled to the methine hydrogen at C(10). The methyl s i n g l e t at 6 3.80 i s assigned to the ester methyl. M u l t i p l e t s at 6 2.67 (2H), 2.37 (3H), and 1.80 (2H) are assigned to the methines and the C(7) methylene hydrogens. The s i n g l e t at 6 2.00 i s assigned to the acetate methyl, whereas the remaining methyl s i n g l e t s appear at 6 1.28, 6 1.22 and 6 0.88. High and low r e s o l u t i o n mass spectra and correct microanalysis also conform to the assigned structure. Single c r y s t a l s of dienone 120 'were also photolyzed at 0°C with a He-Cd l a s e r (A 325 nm) and with a 450 W lamp. No reaction could be observed by GC, t i c and i r spectroscopy. Since no c r y s t a l structure of the dienone 120 was determined, i t i s hig h l y speculative to suggest that the u n r e a c t i v i t y i s due to a c r y s t a l packing e f f e c t or some other condition p e c u l i a r to the c r y s t a l l i n e state. We also note here that the [2+2] intramolecular reaction - 214 -observed i n s o l u t i o n i s almost c e r t a i n l y topochemically forbidden because, from our experience, we can s a f e l y assume that naphthalenone 120 w i l l not c r y s t a l l i z e i n conformation 'C. The analysis of the [2+2] intramolecular c y c l o a d d i t i o n i n s o l u t i o n i s analogous to that of the dienone 119 discussed e a r l i e r i n t h i s Chapter and therefore w i l l not be discussed any further. - 215 CHAPTER 5 QUANTITATIVE STRUCTURE-REACTIVITY CORRELATIONS: GEOMETRIC PARAMETERS FOR HYDROGEN ATOM ABSTRACTIONS There are four routes for endo-benzylic hydrogen atom abstraction that are p o s s i b l e i n the present study: (a) /3-Hydrogen atom abstraction by oxygen through a five-membered t r a n s i t i o n state; (b) 7- or s i x -membered t r a n s i t i o n state benzylic or a l l y l i c hydrogen atom abstraction by the c e n t r a l carbon atoms of the ene-dione chromophore; (c) benzylic hydrogen atom abstrac t i o n by the /3-carbon atom of the enone moiety through six-membered t r a n s i t i o n states; (d) benzylic hydrogen atom abs t r a c t i o n by the /J-carbon atom of enone moiety through a five-membered t r a n s i t i o n state. Only the l a s t three processes have been observed i n the present i n v e s t i g a t i o n i n the s o l i d state. In order to f u l l y understand the process of hydrogen atom abstrac-t i o n , we use a number of geometrical parameters that define the r e l a -tionship between the abstracting atom and the atom being abstracted leading to product formation. These parameters have also been used by Scheffer et a l . 1 7 • 7 3 » a n d cor r e l a t e d with r e a c t i v i t y f or some compounds. The geometric parameters are as follows (Fig. 5): the f i r s t , and probably the most important parameter, i s d, the distance between the hydrogen (abstracted atom) and the abstracting atom (carbon or oxygen). Second i s the angle r c , defined as the angle formed between the C - - - H vector and i t s p r o j e c t i o n on the mean plane of the carbon - 216 -6 ( a ) F i g . 5: D e f i n i t i o n of d, r and A carbon double bond (when the abstracting atom i s oxygen, the correspond-ing parameter i s rQ, and the plane i s the mean plane of the carbonyl group). T h i r d i s the angle Ac defined as the C=C---H angle (for oxygen Ao and C=0---H angle). F i n a l l y , another important parameter that i s also i n d i c a t e d i n F i g . 5 i s the distance between the carbon atoms ( r a d i c a l centers) that eventually become bonded to one another i n the f i n a l product. This distance has been assumed to be the same as the distances i n the s t a r t i n g material. Distance C r i t e r i a i n Hydrogen Atom Abstraction The values of d, r and A for the enones and ene-diones investigated i n t h i s study are l i s t e d i n Table 10. The data i n Table 10 c l e a r l y show that hydrogen atom abstraction by carbon occurs over distances of up to 2.9 A. The average distance of 2.8 A i s i n good agreement with - 217 -Table 10a: 7-Hydrogen atom abstraction by Carbon Compound t.s. d A r c A c C(3). C(5) 49c 6 2.9 47 75 3. 3 51 6 2.8 51 74 3. 2 52 6 2.7 51 74 3. 1 58B 6 2.8 49 74 3. 2 57A 5 2.8 54 77 3. 2 [C(2) -C(5)] 59A 5 2.8 48 72 3. 3 [C(2) -C(5)] 119 5 2.8 58 103 3. ,2 Table 10b: /9-Hydrogen atom abstraction by oxygen Compound t.s . d A T c A c C(2) • C(5) 49c 5 2.6 1 80 4 .4 51 5 2.5 1 84 4 .4 52 5 2.4 3 83 4 .4 54 5 2.5 a 2.5 3 6 81 82 2 .5 C ( l ) . • C(8) 58B 5 2.5 8 81 3 .3 57A 5 2.5 4 85 4 .4 59A 5 2.4 7 96 4 .4 119 unsuitable geometry two independent molecules i n the asymmetric u n i t . - 218 -the suggestions made e a r l i e r by Scheffer et a l . 1 7 ' 7 ^ ' 1 1 5 that the approximate upper l i m i t f o r hydrogen atom abstraction by an sp -carbon should be 2.9A. The value of 2.9 A i s the sum of the van der Waals r a d i i of the two p a r t i c i p a t i n g atoms, that i s , carbon (1.7 A) and H (1.2 ^ 2 2 2 -T-hg U p p e r l i m i t of 2.9 A for hydrogen atom abstrac t i o n by carbon was a r r i v e d at by Scheffer et a l . a f t e r a thorough s o l i d state photo-chemical and X-ray c r y s t a l l o g r a p h i c i n v e s t i g a t i o n of b i c y c l i c enones and ene-diones. D e t a i l s of t h i s study have already been discussed i n the Introduction section. Tables 3 and 4 of the Introduction s e c t i o n l i s t a l l ene-diones studied by Scheffer et a l . whose X-ray c r y s t a l structures were determined. In the case of ene-diones, the hydrogen atom abstrac-t i o n takes place by one of sp - carbon atoms of the ene-dione c e n t r a l double bond v i a a six-membered t r a n s i t i o n state. For enones, i t i s i n v a r i a b l y the B-carbon atom of the enone C=C that i s involved i n the H-atom abstraction. Table 10a also contains two examples of endo-benzylic hydrogen atom abs t r a c t i o n by enone /9-carbon atom through five-membered t r a n s i t i o n states. We also point out here that s o l i d state hydrogen atom abstrac-ion by the B-carbon atom through a five-membered t r a n s i t i o n state was f i r s t observed i n our laboratory at UBC. 1 1 5 An exc e l l e n t example of the demonstration of the upper l i m i t for hydrogen atom abstrac t i o n by oxygen was revealed by Mandelbaum et al.° on ene-diones and i s worth mentioning here. The authors photolyzed f i v e ene-diones of general structure 122 i n the s o l i d state and found that the ene-diones 122a-122d (Scheme 75) were unreactive i n the s o l i d state. However, ene-dione 122e reacted i n the s o l i d state v i a 5-hydrogen atom - 219 a b s t r a c t i o n (seven-membered t r a n s i t i o n state) by oxygen followed by C(l) and C(6) bonding to give a pentacyclic product 122EA. In order to understand the behavior of ene-diones 122a-122e, t h e i r X-ray c r y s t a l structures were determined. The authors found that the distance between the r e a c t i v e 6-hydrogen and i t s nearest carbonyl oxygen v a r i e d with the s i z e of rings 1 and 2. X-ray crystallography revealed that, i n the re a c t i v e ene-dione, the distance between the atoms involved i n abstrac-ton, 5-hydrogen and oxygen, i s 2.7 A. The value of 2.7 A i s the sum of van der Waals r a d i i of oxygen (1.7 A) and hydrogen (1.2 A). Other ene-diones have values ranging from 3.2 A to 4.8 A as shown i n Scheme 75. Ring 1 solid 122 12^EA Ring 1 122a 5 122b 6 122c 6 122d 6 122e 7 Ring 2 5 5 6 7 7 •H5 distance (A) 3.2 4.1 4.8 4.0 2.7 • Photoreaction No No No No Yes Scheme 75 - 220 -Angular Relationships i n Hydrogen Atom Abstraction The distance d between the oxygen (or carbon) and hydrogen atom, although very important, i s not the only f a c t o r that defines the geometry of hydrogen atom abstraction. Also important i s the angular r e l a t i o n s h i p of the hydrogen with respect to oxygen and carbon. I t i s well established i n both the M c L a f f e r t y 2 3 8 > 2 3 9 and Norrish type I I 1 8 5 reactions that the abstracting o r b i t a l i s a non-bonding atomic o r b i t a l on oxygen and not the jr-bond atomic o r b i t a l . Depending on the model considered, the n - o r b i t a l makes an angle of 90° or 120° with the C=0 axis. K a s h a 2 4 0 ' 2 4 1 has suggested that the lone p a i r - c o n t a i n i n g atomic o r b i t a l s of carbonyl groups are non-equivalent, one p a i r being l a r g e l y 2s and the other e s s e n t i a l l y 2p i n nature (Fig. 32a). Of the two o r b i t a l s , i t i s the l a t t e r , which forms an angle of 90° with the C=0 axis, that i s thought to be involved i n abstraction. Another group of workers has suggested that the two lone pa i r s on oxygen are equivalent as "rabbit e a r " 2 4 2 " 2 4 4 s p 2 hybrid atomic o r b i t a l s oriented at an angle of 120° with respect to the C=0 axis ( Fig. 32b). The rab b i t ear model ( a ) ( b ) F i g . 32: Arrangement of atomic o r b i t a l s i n carbonyl groups, a) Kasha's model; b) Rabbit ear model. 221 -i s supported by X-ray c r y s t a l l o g r a p h i c studies dealing with the direc-t i o n a l i t y of hydrogen bonds to carbonyl g r o u p s . 2 4 2 " 2 4 4 I t i s reasonable to suggest that the abstrac t i o n of hydrogen w i l l be most e f f i c i e n t when the hydrogen atom approaches the carbonyl group and with maximum overlap with the abstracting n - o r b i t a l . Accordingly, a b s t r a c t i o n should be most e f f i c i e n t when r Q approaches 0° and A Q = 90-120° and l e a s t e f f i c i e n t when TQ = 90 and A Q - 180°. For example, the non r e a c t i v i t y of ketone 123 towards McLafferty rearrangement was inter p r e t e d as being due to an unfavorable r Q angle of 80°. Ketone 124, with a T Q angle of 50°, d i d undergo McLafferty rearrangement. I t i s noted here that i n both cases, the values of d (1.6 A each) and r Q were estimated f o r the c l o s e s t hydrogen approach using molecular models. Keto-alcohol 125 i s unreactive under uv i r r a d i a t i o n despite a very close 7-hydrogen and oxygen contact. Aoyama et a l . 2 4 ^ suggested that the u n r e a c t i v i t y of ketoalcohol 125 i s due to the f a c t that the 7-hydrogen atom l i e s almost p r e c i s e l y i n the nodal plane ( r Q = 90°). In two recent review a r t i c l e s 7 4 ' 2 4 ^ 3 a note of caution has been given to Aoyama's suggestion owing to the known r e v e r s i b i l i t y of 7-hydrogen atom abstrac-t i o n , which may eventually r e s u l t i n no net photochemistry. 123 124 125 - 222 -The data f or hydrogen atom abstraction i n Table 10b show that the average distance f o r hydrogen atom abstraction by oxygen i s 2.5 A; the average r Q value i s 4° and A Q i s 84°. Since these values are almost i d e a l f o r benzylic hydrogen atom abstraction by oxygen (01), and almost exactly the same (d = 2.5 A, TQ = 4°, A Q = 83°) as those of naphthalenediones studied by Scheffer et a l . 7 3 (see Table I and II i n the Introduction section) where rea c t i o n d i d take place, such abstrac-t i o n i s expected here as w e l l . But no net rea c t i o n v i a hydrogen atom abs t r a c t i o n by oxygen was observed. The s i t u a t i o n i s shown i n Scheme 76. As i s c l e a r from Scheme 76, coupling of the r a d i c a l centers at C(l) and C(6) requires the d i s r u p t i o n of aromaticity and therefore 126EA i s not observed. The C(3) and C(8) r a d i c a l centers can also combine to give 126CP type product. However, no product a r i s i n g from t h i s route was observed i n the s o l i d state. The most l i k e l y reason f or the lack of O 126CP Scheme 76 223 -formation of 126CP i s the distance between the C(3) and C(8) r a d i c a l centers. The average distance between the p o t e n t i a l r a d i c a l centers from Table 10b i s 4.4 A, much larger than the sum of the van der Waals r a d i i (3.4 A) observed so f a r for bond formation. The longest distance between r a d i c a l centers which has been observed by Scheffer et a l . 7 3 for bond formation i s 3.7 A. The importance of the C(3)...C(8) distance i s substantiated by our s o l u t i o n studies where c r y s t a l l a t t i c e r e s t r i c t i o n s do not e x i s t . Bond r o t a t i o n can b r i n g the r a d i c a l centers C(3) and C(8) cl o s e r , as discussed e a r l i e r (see Scheme 44, for example) and bonding takes place between C(3) and C(8) r a d i c a l centers giving, f or example, 52CP (Scheme 44) and 36CP (Scheme 15). In the case of hydrogen atom abstraction by sp 2-carbon, i t i s the 2p atomic o r b i t a l that i s involved. In the ground state of enones and ene-diones, the 2p atomic o r b i t a l i s orthogonal to the plane of the double bond, and, therefore, the preferred.geometry of approach (see the disc u s s i o n on c o r r e l a t i o n of ground state parameters with excited state geometry towards the end of t h i s chapter) of the hydrogen atom i s 90° to the C=C axis and along the long axis of the atomic o r b i t a l rather than i n the nodal plane. This arrangement of the 2p-atomic o r b i t a l means the i d e a l values of both r c and A c should be 90°. The data i n Table 10a show that the average values of r c and A c are 51 and 78°, r e s p e c t i v e l y . As i t i s c l e a r that these values are not optimum values for hydrogen atom abstraction, we suggest that t h i s may be a t h i r d f a c t o r , along with the low jr , 7 r t r i p l e t energy and less resonance s t a b i l i z e d b i r a d i c a l , that may contribute to the higher a c t i v a t i o n energy of hydrogen atom abstract i o n by carbon compared to oxygen for ene-diones ( e s p e c i a l l y for - 224 -ene-dione 52 (Scheme 42). Though the average values of Tc and A c are not close to the optimum values, they are i n t e r n a l l y consistent with the average values of 50° and 74° obtained by Scheffer et a l . 7 3 i n e a r l i e r studies of enones and ene-diones. The Bonding Distance Between B i r a d i c a l Centers Table 10 also contains a parameter which i s the distance between the carbon atoms that eventually become bonded to one another. The process of b i r a d i c a l closure i s as important to the success of the s o l i d state r e a c t i o n as i s hydrogen atom abstraction. I f the b i r a d i c a l closure i s topochemically disallowed, that i s , requires motions that cannot be allowed by the c r y s t a l l a t t i c e , reverse hydrogen transfer could lead to regeneration of the s t a r t i n g material, and no net progress i n the r e a c t i o n would be observed. The average carbon carbon distance between r a d i c a l centers that become bonded to one another to y i e l d the f i n a l product i s 3.2 A i n the present study. This average distance i s less than the average distance observed by Scheffer et a l . 7 3 of 3.3 A for naphthalenediones and naphthoquinols (see Tables 3 and 4 of the Introduction section) and i s also less than the sum of the van der Waals r a d i i f o r two carbon atoms (3.4 A). These distances r e f e r to ground state distances and not to the b i r a d i c a l intermediates but, as suggested 7 ^  earlier,'-* these species must have s i m i l a r gross conformations due to the r e s t r a i n t s of the c r y s t a l l a t t i c e . The importance of the distance between the r a d i c a l centers could not be emphasized more than our own - 225 -example of ene-dione 52 as discussed e a r l i e r . F i n a l l y , we now examine the question of the v a l i d i t y of the argu-ment we made along with other w o r k e r s 7 3 • 1 7 7 suggesting that ground state s t r u c t u r a l parameters can be c o r r e l a t e d with excited state r e a c t i v i t y i n the s o l i d state. The excellent 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 observed i n the present study and i n other s o l i d state photochemical i n v e s t i g a t i o n s 7 3 ' 7 7 do not leave much doubt that the ground state parameters can be c o r r e l a t e d to the excited state r e a c t i v i t y . F i r s t of a l l , i t i s l i k e l y that the r i g i d s o l i d state medium w i l l allow only minimal changes i n the geometry of the excited state because of the r e a c t i o n c a v i t y . Also, there i s general a g r e e m e n t 7 4 » 2 4 6 that the geometries of (n ,7r ) excited states of a,B-unsaturated ketones are e s s e n t i a l l y i d e n t i c a l to t h e i r ground state geometries with s l i g h t increases (<0.1 A) i n the C=0 and C=C bond lengths. The s i t u a t i o n with sv ^  the T T . T T J states of a,/3-unsaturated ketones i s rather uncertain at t h i s stage as discussed below. Schaffner et a l . 1 9 1 have investigated the phosphorescence proper-t i e s of several six-membered c y c l i c enones. They found, i n general, that the emission spectra were quite d i f f u s e . This l e d them to conclude that the n,n t r i p l e t s of these enones are d i s t o r t e d , non-planar species unless the d i s t o r t i o n i s prevented by s t r u c t u r a l constraints, as i n testosterone acetate 127 and ene-dione 128. Twisting around C=C has also been suggested by Bonneau 2 4 7 during the l a s e r f l a s h photolysis of various enones, and he concluded that the angle of t o r s i o n around the C=C bond and consequent t r i p l e t e x c i t a t i o n energy v a r i e d as a function of the s t r u c t u r a l constraints of the system. T h e o r e t i c a l c a l c u l a -- 226 -OAc OAc tions^° have also shown that n ,ir states are strongly s t a b i l i z e d by t w i s t i n g about C=C. However, Jones and K e a r n s 2 4 9 l a t e r suggested, from the h i g h l y resolved phosphorescence spectra of s i n g l e c r y s t a l s of several fused r i n g enones at 4.2 K, that there i s l i t t l e change i n the geometry of the n , n state r e l a t i v e to the ground state. With respect to the previous c i t e d t h e o r e t i c a l c a l c u l a t i o n s 2 4 8 which suggested that J T . T T * states are strongly s t a b i l i z e d by twisting about C=C, Jones and K e a r n s 2 4 9 note that these states are d e s t a b i l i z e d by t w i s t i n g about C-C (C=C-C=0) bond because of the increased double-bond character i n t h i s bond i n the n , n states. The two twisting motions are coupled i n fused rings supporting t h e i r observation that the enone chromophore remains e s s e n t i a l l y planar. Even though the 7 r,7r* state remains planar i n single c r y s t a l s at 4.2 K, at the higher temperatures where photochemistry occurs, pathways i n v o l v i n g twisting may become possible. In a recent communication Schuster et a l . 2 - ^ a n dPienta 2-^ a have suggested that the transient species observed by Bonneau 2 4 7 and assigned as a twisted it , T T t r i p l e t i s not involved i n the photochemical reactions of enones. The species which i s involved i s a s h o r t - l i v e d phantom t r i p l e t species undetected by f l a s h photolysis. The l a s t observation by Schuster et a l . 2 - 5 ^ suggests that the s i t u a t i o n with enones i s more - 227 complex, and further investigations are needed. The discussion given above may also be true for ene-diones, although there are no analogous photophysical studies on ene-diones. If the reactive species at room temperature i s a planar u,ix J species, our ground state parameters can be d i r e c t l y c o r r e l a t e d with excited state geometry without much doubt. whatever the geometry of the excited state C=C may be, our r e s u l t s , and those of other workers 7 3'-'- 7 7 i n t h i s area, n i c e l y c o r r e l a t e the ground state parameters with chemical r e a c t i v i t y . - 228 -EXPERIMENTAL 229 -EXPERIMENTAL Infrared Spectra Infrared (IR) spectra were recorded e i t h e r on a Perkin-Elmer i n f r a r e d spectrophotometer (model 710B) or on a Perkin-Elmer FTIR spec-trometer (model 1710) i n one of the three ways: a) In KBr p e l l e t s containing 0.5 to 1% by weight of sample. b) With neat l i q u i d samples sandwiched between two sodium chloride p l a t e s . c) In CHCI3 containing 5% by weight of sample. KBr p e l l e t s were made using a Perkin-Elmer-KBr evacuable die 186-0002 and a Carver laboratory press model B. The pressing load was generally 20,000 lbs/square inch. The Perkin-Elmer i n f r a r e d spectro-photometer (model 710B) was c a l i b r a t e d with a polystyrene f i l m . In the case of compounds which had functional groups, only those peaks that had f u n c t i o n a l groups are recorded i n the text; otherwise, a l l major peaks have been reported. IR spectra were measured as ^ m a x i n cm"1. Nuclear Magnetic Resonance Spectra Nuclear magnetic resonance spectra (r e f e r r e d to simply as NMR spectra i n the text, unless otherwise stated) were recorded by the departmental NMR Service on Bruker WP 80, Bruker HXS 270, Varian XL 300, 230 -and Bruker WH 400 spectrometers. NMR spectra were also recorded by the author on a Varian T60 instrument. i J C NMR spectra were recorded on a Bruker WH 400 spectrometer operating at 100.1 MHz. Deuterochloroform (CDCI3) was used as the solvent and tetramethylsilane (TMS) was used as the i n t e r n a l standard, unless otherwise stated. Signal positions are given i n d e l t a (5), and t h e i r m u l t i p l i c i t y , coupling constants (J i n Hz), integrated areas and assignments ( i f made) are given i n parenthesis. Mass Spectra Low r e s o l u t i o n mass spectra and high r e s o l u t i o n mass spectra (HRMS) were obtained on a Kratos MS 50 instrument operating at 70 eV. Intensi-t i e s are recorded as percentages of the most intense (base) peak and are given i n brackets. Molecular ions are designated M+. Gas Chromatography Mass Spectrometry Gas chromatography mass spectrometry (GCMS) was performed by the departmental GCMS service on Kratos MS 80RFA and Carlo Erba 4160 instruments. 231 -U l t r a v i o l e t Spectra U l t r a v i o l e t (uv) spectra were recorded on a Carey 17D spectro-photometer i n a c e t o n i t r i l e . E x t i n c t i o n c o e f f i c i e n t s are given i n brackets. Microanalysis Microanalyses were c a r r i e d out by the departmental Microanalyst. Melting Points Melting points (MP) were recorded on a Fisher-Johns hot stage apparatus and are uncorrected. Chromatography Thin layer chromatography ( t i c ) was done on 0.2 mm thick aluminum sheets coated with s i l i c a gel (Merck 6OF254) and the plates were developed i n a s u i t a b l e solvent (mentioned i n the Experimental secti o n ) . The developed plates were observed under UV l i g h t . Flash column chroma-tography was c a r r i e d out under 5-10 PSi N 2 pressure. S i l i c a gel (Merck 9385) with p a r t i c l e size 0.040-0.063 mm was used, and was s l u r r y packed - 232 i n the e l u t i n g solvent. Solution Photolyses Quantitative scale s o l u t i o n photolyses were c a r r i e d out with a 450 W Hanovia medium pressure mercury lamp contained i n a water cooled quartz immersion w e l l . The required wave length (given i n nm) of l i g h t was achieved by s u i t a b l e f i l t e r sleeves a v a i l a b l e from Ace Glass (Pyrex A >290 nm, uranium A > 330 nm). The sample s o l u t i o n was degassed by bubbling nitrogen through the s o l u t i o n at a slow rate f o r 45 min to 1 h p r i o r to and during photolysis. The duration of photolysis was found to vary with the age of the lamp. I r r a d i a t i o n f o r a n a l y t i c a l purposes was usually c a r r i e d out with a Molectron UV 22 pulsed nitrogen l a s e r (A 337 nm, 330 mW average power). A Liconix He-Cd 325 nm CW l a s e r and the Hanovia 450 W lamp were also used oc c a s i o n a l l y . The samples were degassed by freeze-pump-thaw cycles, under a p o s i t i v e nitrogen pressure, at l e a s t three times. A l l reactions were c a r r i e d out at room temperature (20 ± 2°C) unless other-wise stated. Spectral grade solvents a v a i l a b l e from BDH or Fisher were used without any further p u r i f i c a t i o n . S o l i d State Photolyses These were c a r r i e d out by plac i n g a su i t a b l e s i n g l e c r y s t a l i n a 233 s p e c i a l l y made quartz tube (usually 2-3 mm i n diameter with a B9 stop-per) . The samples were degassed by attachment to a vacuum l i n e and then ei t h e r N 2 or Ar was introduced. This process was repeated at le a s t three times. The samples were sealed immediately and then photolyzed with a N 2 l a s e r . Sometimes a He-Cd 325 nm CW las e r or a Hanovia 450 W medium pressure Hg lamp were used. During, the course of photolysis, s p e c i a l care was taken to make sure that the substrate being photolyzed di d not melt. This was done eit h e r by l i m i t i n g the photochemical reac-t i o n to very low conversion or by carrying out the reac t i o n at lower temperatures (between 0 and -20°C). The lower temperatures were main-tained by using an appropriate i c e - s a l t bath or Dry Ice-solvent b a t h . 2 5 1 D e t a i l s of such baths and t h e i r temperatures are given i n Ref. 251. The c r y s t a l s maintained at the desired temperature i n a transparent Dewar f l a s k were photolyzed with a N 2 l a s e r . Powdered c r y s t a l s (1-2%, W/W) i n KBr matrices were also photolyzed and the re a c t i o n followed by i r spectroscopy. This was found to be a quick and e f f i c i e n t way to check whether a c e r t a i n compound w i l l react i n the s o l i d state. For large scale s o l i d - state photolyses, powdered c r y s t a l s were sandwiched between Pyrex glass plates (- 2" i n length and -1" i n dia-meter) . The ends of these plates were taped with 3M Magic transparent tape and then the taped plates were sealed i n polyethylene bags and l a t e r photolyzed with a Hanovia 450 W medium pressure Hg lamp at A >290 nm. The photolysis was c a r r i e d out u n t i l at l e a s t 90% of s t a r t i n g material was consumed. A f t e r the reac t i o n was over, the photoproduct(s) were scraped o f f the plates and 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 or column - 234 chromatography or both. P u r i f i c a t i o n of Solvents and Reagents Benzene , a c e t o n i t r i l e , dichloromethane, THF, d i e t h y l ether, were 9 S 9 p u r i f i e d by well known methods. J i Chlorotrimethylsilane, triethylamine and o-methylbenzaldehyde were d i s t i l l e d . For other compounds, the p u r i f i c a t i o n method i s mentioned i n the Experimental Section. Gas Chromatography A n a l y t i c a l gas chromatography (gas l i q u i d chromatography) was per-formed on Hewlett-Packard gas chromatograph models 5880A and 5890A f i t t e d with flame i o n i z a t i o n detectors. The Hewlett-Packard 5880A instrument was equipped with a b u i l t - i n integrator and the 5890A i n s t r u -ment had an 3392A integrator. A l l the chromatography was c a r r i e d out on one of the following fused s i l i c a c a p i l l a r y columns: a) a 12m x 0.21 mm Carbowax 20 M column; b) a 50 m x 0.21 mm Carbowax 20 M column; c) a 12m x 0.21 mm OV-101 column. A l l the above-mentioned columns were A known carcinogen, benzene was handled very c a r e f u l l y i n the fume hood. The author himself i s very s e n s i t i v e to trace amounts of t h i s solvent (skin s e n s i t i v i t y ) . Once the r e l a t i o n s h i p had been established, the use of t h i s solvent was completely stopped. 235 supplied by Hewlett Packard. Two other columns were used: d) a 15m x 0.25 mm DB-1 column with 100% dimethyl polysiloxane f i l m of 0.25 /xm thickness; and e) a 15 m x 0.25 mm DB-5 column with 95% dimethyl-(5%)-diphenyl-polysiloxane f i l m of 0.25 /im thickness, supplied by J & W S c i e n t i f i c , Inc. 1. Synthesis of [o- [ a -(Trimethylsilyl)methyl]benzyl]trimethylammonium bromide ( 2 7 ) 5 1 (a) Synthesis of Benzvltrimethvlammonium Iodide ( 6 3 ) 1 4 3 To a s t i r r e d s o l u t i o n of N,N-dimethylbenzylamine (10.5 g, 75.0 mmol) i n commercial absolute ethanol (60 ml), i n a two necked round-bottomed f l a s k attached to a condenser with a drying tube, iodomethane (14.26 g, 100.0 mmol) was added with a syringe i n 5 min. The reaction mixture turned yellow immediately, the f l a s k became hot and the contents st a r t e d r e f l u x i n g . The s o l u t i o n was allowed to r e f l u x f o r another 25 min. without any heat. A f t e r i t stopped r e f l u x i n g , the reac t i o n mixture was heated to r e f l u x on a water bath for another 30 min. The yellow r e a c t i o n mixture, on t r a n s f e r r i n g to an Erlenmeyer f l a s k , s o l i d i f i e d g i v i ng yellow c r y s t a l s . These were washed twice with anhydrous d i e t h y l ether (50 ml) and f i l t e r e d , g i v ing white c r y s t a l s (19.40 g, 94%). MP 177-78°C ( l i t . 1 4 3 MP 178-179°C). IR (KBr) 2870, 1250 cm - 1.' NMR 8 7.85-7.38 (m, 5H, Ar-H), 5.10 (s, 2H, CH2>- 3 - 4 5 (s> 9 H> 236 3xCH 3). (b) Synthesis of (o-Methylbenzyl)dimethylamine ( 6 4 ) 1 ^  To a three-necked round-bottomed f l a s k f i t t e d with a Dry Ice r e f l u x condenser, and containing 800 ml of ammonia was added 0.1-0.5 g of sodium u n t i l the blue color p e r s i s t e d . At t h i s point, f e r r i c n i t r a t e (0.20 g) and then sodium (4.14 g) were added slowly over a period of 5 min. The s o l u t i o n was s t i r r e d f o r another 20 min. u n t i l a greyish-black p r e c i p i t a t e formed. The mixture was swirled to wash down the mirror of sodium which formed on the upper walls of the f l a s k . Benzyltrimethylammonium iodide (63) (41.4 g, 0.15 mol) was added i n 15 min. and the reaction mixture was allowed to s t i r f o r another two hours. During t h i s period more ammonia was added to maintain a constant volume. To t h i s , NH^Cl (5.0 g) and (40 ml) were added very care-f u l l y . Ammonia was evaporated and the organic compounds were extracted with d i e t h y l ether (3 x 200 ml). The combined extracts were washed with s a l t water (20 ml) and d r i e d over Na2S04- Diethyl ether was rotary evaporated to give an almost c o l o r l e s s l i q u i d , which was d i s t i l l e d at 42°C at 0.3 mm Hg ( l i t . 1 4 4 BP 72-73°C at 9 mmHg) to give a c o l o r l e s s o i l (19.87 g, 88%). IR (neat) 2940, 2800, 2750, 1460, 1368, 1280, 1030, 760 cm - 1. NMR S 7.1 (br S, 4H, Ar-H), 3.33 (s, 2H, CH 2), 2.33 (s, 3H, CH3), 2.20 (s, 6H, N(CH 3) 2). - 237 (c) ro-(a(Trimethylsilvl)methyl)benzyl1dimethylamine ( 6 5 ) 3 1 To a s t i r r e d s o l u t i o n of (o-methylbenzyl)dimethylamine (64) (2.00 g, 13.3 mmol) i n anhydrous ether (30 ml) maintained at 0°C was added n-butyl l i t h i u m (20 ml, 26.6 mmol) i n 30 min. A change i n color from c o l o r l e s s to yellow was observed. The yellow s o l u t i o n was allowed to warm to room temperature and was s t i r r e d f o r a period of 22 hours. The r e s u l t i n g orange s o l u t i o n was cooled to 0°C and triethylamine (0.5 ml), from a f r e s h l y opened b o t t l e , and chlorotrimethyl s i l a n e (4.5 ml 26.8 mmol) were added simultaneously using two syringes. The orange color immediately disappeared. This s o l u t i o n was allowed to warm to room temperature and was s t i r r e d overnight. The c o l o r l e s s s o l u t i o n was quenched with c o l d aqueous sodium bicarbonate s o l u t i o n (saturated, 20 ml), and the organic compounds were extracted with d i e t h y l ether (3 x 50 ml), washed with co l d aqueous s a l t s o l u t i o n (10 ml) and with co l d H2O (10 ml). A f t e r drying, d i e t h y l ether was rotary evaporated giving a s l i g h t l y yellow o i l which was d i s t i l l e d to give a c o l o r l e s s l i q u i d (2.48 g, 84%). BP 81.5"C at 0.3 mmHg ( l i t . 5 1 BP 54°C at 0.2 mmHg). IR (neat) 2940, 2800, 2750, 1450, 1254, 1020, 820. NMR (TMS external) 6 7.42-7.00 (m, 4H, Ar-H), 3.41 (s, 2H, CH2-N), 2.35 (s, 2H, CH 2-Si), 2.31 (s, 6H, N(CH 3) 2), 0.10 (s, 9H, S i ( C H 3 ) 3 ) . 238 -(d) Synthesis of To- fa- (TrimethylsilyDmethyDbenzyl 1 trimethvlammonium  Bromide ( 2 7 ) 5 1 This was done i n an easier and more convenient method than the one reported by I t o . 1 [o-((Trimethylsilyl)methyl)benzyl]dimethlyamine (64) (2.22 g, 10.0 mmol) was cooled to 0°C and methyl bromide (5.02 g, 2.90 ml, 53.0 mmol)' was added. The reaction mixture c r y s t a l l i z e d within 2 min. g i v i n g c o l o r l e s s c r y s t a l s (3.20 g, 100%). MP 215-16°C dec. ( l i t . 5 1 MP 218-20°C d e c ) . IR (KBr) 2880, 1246, 855 cm"1. NMR (TMS external) S 7.70-7.02 (m, 4H, Ar-H), 4.90 (s, 2H, CH2-NMe3Br 3.50 (s, 9H, N(CH 3) 3 Br), 2.45 (s, 2H, CH 2-SiMe 3), 0.10 (s, 9H, SiMe 3). The s p e c t r a l data of t h i s material compared favorably with the l i t e r a t u r e v a l u e s . 5 7 2. Synthesis of 3,6-Dihydrobenzo[b]-l,2-oxathiin-2-oxide ( 6 1 ) i 8 " b : J (a) Synthesis of 1-Hvdroxy-l.3-dihydrobenzofblthiophene-2.2-dioxide  ( 6 1 a ) 5 8 Sulfur dioxide (10 ml), condensed using a Dry Ice acetone bath, was bubbled through benzene (100 ml) with a stream of nitrogen u n t i l a l l the su l f u r dioxide was dissolved. This s o l u t i o n was placed i n the photo-l y s i s apparatus and tolualdehyde (1.00 g, 8.3 mmol) was added. The reac-t i o n mixture was photolysed using a Pyrex glass f i l t e r f o r 12-16 hours. - 239 -The r e a c t i o n was followed by t i c which even a f t e r t h i s time indicated the presence of some s t a r t i n g material. Benzene was rotary evaporated at room temperature to give a brownish o i l . Though Durst and C h a r l t o n 6 3 claimed to have c r y s t a l l i z e d t h i s brown o i l , no success was achieved i n c r y s t a l l i z i n g the compound i n the present study. A NMR spectrum showed that the r e a c t i o n was -95% complete. Y i e l d (1.39 g, 100%). IR (neat) 3350 (OH), 1320 and 1125 (S0 2) cm - 1. NMR 5 7.95-6.95 (m, 4H, Ar-H), 5.73 (s, 1H exchangeable, OH), 5.60 (s, 1H, -CH-S), 4.24 (s, 2H, CH 2). (b) Synthesis of 3.6-Dihydrobenzofbl-1.2-oxathiin-2-oxide  ( 6 1 )58,60,63 To a s t i r r e d s o l u t i o n of the hydroxy sulfone (61a) (0.6 g, 3.26 mmol) i n a 5% methanolic s o l u t i o n of sodium hydroxide maintained at 0°C was added sodium borohydride (800 mg) slowly over a period of 5-10 min. An immediate evolution of hydrogen gas was observed. The s o l u t i o n was s t i r r e d f o r 30 min at 0°C and i t s temperature was r a i s e d to 50°C for 5 min. The solvent was rotary evaporated, the residue was cooled to 0°C, and cone hydrochloric a c i d (30 ml) was added c a r e f u l l y . The brownish s o l u t i o n was d i l u t e d with water, extracted with methylene chloride (50 mlx2), decolorized with Norit, rotary evaporated to give a yellow o i l , 0.3 g, which a f t e r column chromatography using pet. ether (30-60°C): EtOAc (4:1, v/v) gave a c o l o r l e s s o i l (0.15 g, 27%). IR (neat) 1120 (S=0) cm - 1. - 240 NMR 5 7.45-7.10 (m, 4H, ArH), 5.30 (d, J = 14 Hz, 1H), 4.96 (d, J =14 Hz, 1H), 4.42 (d, J = 16 Hz, 1H), 3.55 (d, J - 16 Hz, 1H). The s p e c t r a l data of t h i s material compared favorably with the published d a t a . 6 2 ' 6 5 9 S 3 3. Synthesis of 2,3,5-Trimethyl-l,4-benzoquinone^ J J A suspension of 2,3,5-trimethyl hydroquinone (15.2 g, 0.10 mol) i n g l a c i a l a c e t i c a c i d (100 ml) was heated u n t i l the s o l i d had j u s t d i s -solved. The s o l u t i o n was cooled i n an ice bath u n t i l the temperature dropped to ~30°C and a cooled s o l u t i o n of sodium dichromate dihydrate (10.8 g) i n a c e t i c a c i d (25 ml) was added c a r e f u l l y over a period of 25 min with constant cooling to maintain the temperature at - 35°C. Af t e r s t i r r i n g f o r 5 min, the s o l u t i o n was d i l u t e d with water (50 ml) and extracted with d i e t h y l ether (100 ml, 3 times). The br i g h t yellow s o l u t i o n was washed with water (100 ml), then with saturated s a l t solu-t i o n (20 ml), d r i e d over sodium s u l f a t e , and the solvent was rotary evaporated to give an o i l which c r y s t a l l i z e d g i v i n g yellow c r y s t a l s (8.00 g, 53%). MP 29-30°C ( l i t . 7 MP 29-30°C). IR (KBr) 1656 (C-0) cm"1. NMR 6 6.55 (bs, 1H, v i n y l i c ) , 2.05 (fortuituous s, 9H, 3xCH 3). - 241 -4. Synthesis of Duroquinone 1 4 3 (a) Dinitrodurene A s o l u t i o n of durene (13.4 g, 0.10 mol) i n 100 ml of chloroform was added to cone H2SO4 i n an 800 ml beaker. The mixture was cooled to 0°C and fuming HNO3 (10 ml, d = 1.50) was added drop by drop, with s t i r r i n g , so that the temperature did not r i s e above 50°C. As soon as a l l the a c i d had been added, the mixture was poured into a separatory funnel, the s u l f u r i c a c i d layer was removed, and the chloroform layer was immediately treated with 10% sodium carbonate s o l u t i o n (500 ml). This was again washed with 25% sodium carbonate s o l u t i o n (100 ml), dried over calcium chloride and f i l t e r e d . The solvent was rotary evaporated and the c o l o r l e s s s o l i d obtained was r e c r y s t a l l i z e d from 95% ethanol a f f o r d i n g c o l o r l e s s c r y s t a l s (21.5 g, 92%). MP 206-207°C ( l i t . 8 MP 207-208°C). (b) Reduction of Dinitrodurene To a b o i l i n g s o l u t i o n of dinitrodurene (18.0 g, 0.08 mol) i n g l a c i a l a c e t i c a c i d (200 ml) was added c a r e f u l l y a s o l u t i o n of stannous chloride (140.0 g, 0.74 mol) i n cone HC1 (150 ml), over 15 min. The r e a c t i o n mixture was cooled to 10°C, y i e l d i n g c o l o r l e s s c r y s t a l s . A f t e r f i l t r a t i o n , the c r y s t a l s were washed twice with ethanol (10 ml) and twice with d i e t h y l ether to give the t i n compound [C^(CE^)^-242 -(NH 2 . H C l ) 2 ] 2 . S n C l 4 . Y i e l d 28.0 g, 95%. (c) Duroquinone The t i n compound (25.0 g, 0.67 mol) was added to a s o l u t i o n of FeCl3 (75.0 g, 0.46 mol) i n a mixture of 150 ml water and 20 ml cone HC1. This mixture was allowed to stand overnight at room temperature, and was then f i l t e r e d . The product was r e c r y s t a l l i z e d from ethanol, a f f o r d i n g l i g h t yellow c r y s t a l s of duroquinone (10.0 g, 90%). MP 109-110°C ( l i t . 1 4 5 MP 109-110°C). 5 . 2, 3-Dlmethyl-l, 4-naphthalenedione i : > : 5 To a hot (~60°C) s o l u t i o n of 2,3-dimethylnaphthalene (1.00 g, 64 mmol) i n g l a c i a l a c e t i c a c i d (10 ml) was added a hot (~60°C) s o l u t i o n of Cr03 (1.53 g, 15.4 mmol) i n 80% ac e t i c a c i d (10 ml) over a period of 20 min. The reac t i o n mixture was then heated to r e f l u x f o r 10 min. Water (25 ml) was added to t h i s cooled re a c t i o n mixture whereupon yellow crys-t a l s p r e c i p i t a t e d . These were f i l t e r e d g i v i n g yellow c r y s t a l s (0.91 g, 77%) . MP 119-20°C ( l i t . 1 5 3 MP 127°C). IR (CHC1 3) 1650 (C=0) cm - 1. NMR 6 8.22-7.52 (m, 4H, Ar), 2.12 (s, 6H, 2xCH 3). - 243 6. Synthesis of Tetraethyl-1,4-benzoquinone ( 6 6 ) 1 5 5 (a) Synthesis of Hexaethvlbenzene 1 5 5 To a s t i r r e d s o l u t i o n of cold benzene (2.5 g, 32 .0 mmol) and ethyl c h l o r i d e (12.5 g, 201.6 mmol) was added A1C1 3 (1.62 g, 12.4 mmol) r e s u l t i n g i n a brownish s o l u t i o n . This was allowed to s t i r overnight at room temperature. Cold water was added to t h i s orange s o l u t i o n , and the organic compounds were extracted with d i e t h y l ether (50 ml, three times). The etheral layer was dr i e d over NaS0 4 , f i l t e r e d , and rotary evaporated to give an o i l , which c r y s t a l l i z e d y i e l d i n g c o l o r l e s s c r y s t a l s (3.4 g, 97%): MP 124-25°C ( l i t . 1 5 5 a MP 129°C). IR (CHCI3) 2950, 1450, 1380, 1060 cm"1. NMR 6 2.70 (q, 12H, 6xCH 2 ) , 1.15 (t, 16H, 6xCH 3 ) . Mass Spectrum, m/e M + 246. (b) Synthesis of Pentaethvlacetophenone1-*-'1-' To a s o l u t i o n of hexaethylbenzene (1.23 g, 5.0 mmol) i n anhydrous carbon d i s u l f i d e (10 ml) was added ac e t y l chloride (0.40 g, 5.1 mmol) followed by aluminum chloride (0.73 g, 5.5 mmol). The s o l u t i o n was refl u x e d u n t i l a change i n color to brown-black was observed. The reac-t i o n mixture was then poured into cold, d i l u t e hydrochloric a c i d (40 ml). The organic compounds were extracted using d i e t h y l ether (50 ml, 244 -three times). The extracts were combined, dri e d over Na2S0,4, and rotary evaporated to give a c o l o r l e s s s o l i d (1.26 g, 97%). MP 134-35°C ( l i t . 1 5 5 b MP 137-137.5°C). IR (CHC1 3) 1680 (C=0) cm"1. Mass Spectrum, m/e M + 260 (c) Synthesis of 3 . 6-Dinitrotetraethylbenzene 1 3 C ' 1- )- 3 Q To a s o l u t i o n of pentaethylacetophenone (4.00 g, 15.4 mmol) i n C H C I 3 (50 ml) was added 40 ml of mixed acids (HN03 (d=1.50): cone H 2S0 4 (1:3, v/v). The temperature rose quickly, and the s o l u t i o n turned black, then brown and f i n a l l y orange. A f t e r 6 h, the s o l u t i o n was d i l u t e d with water and the organic compounds were extracted with chloro-form. The chloroform layer was washed with a d i l u t e aqueous s o l u t i o n of sodium bicarbonate and drie d over Na2S04. Chloroform was rotary evapor-ated and the yellow s o l i d residue was r e c r y s t a l l i z e d from ethanol (20 ml) to y i e l d c o l o r l e s s c r y s t a l s (3.8 g, 88%). MP 146-47°C ( l i t . 1 5 5 c ' 1 5 5 d MP 145-147°C). IR ( C H C I 3 ) 1530, 1380 (N0 2) cm" 1 ' . -NMR 5 2.60 (q, 8H, 4xCH 2), 1.25 ( t , 12H, 4xCH 3). Mass Spectrum, m/e M + 280. - 245 (d) Synthesis of Tetraethyl-1.4-benzoquinone ( 6 6 ) 1 3 3 a To a hot (60-70°C) s o l u t i o n of 3,6-dinitrotetraethylbenzene (2.00 g, 7.1 mmol) i n a c e t i c a c i d (20 ml) was added a s o l u t i o n of stannous choride dihydrate (12.5 g, 55.4 mmol) i n cone HCl (15 ml). A f t e r the vigourous r e a c t i o n subsided, the mixture was refluxed f or 10 min and then cooled to 0°C. The white c r y s t a l l i n e s o l i d produced was f i l t e r e d o f f . A suspension of t h i s compound was allowed to stand overnight at room temperature i n a s o l u t i o n of FeCl3 (40 g) i n 15 ml cone HCl and then f i l t e r e d . The product was r e c r y s t a l l i z e d from 90% ethanol, giving yellow c r y s t a l s (1.04 g, 66%). MP 56-57°C ( l i t . 1 5 5 d MP 56-57°C). IR (CHC1 3) 1630 (C=0) cm - 1. NMR 6 2.50 (q, 8H, 4xCH 2), 1.10 ( t , 12H, 4xCH 3). 7. Synthesis of Tetrabutylammonium F l u o r i d e 1 - 3 0 Commercial 20% tetrabutylammonium hydroxide i n water was t i t r a t e d with d i l u t e aqueous h y d r o f l u o r i c acid u n t i l the s o l u t i o n had a pH of -7.00 as determined with pH paper. The s o l u t i o n was cooled below 10°C r e s u l t i n g i n the formation of a white s o l i d . The l i q u i d was decanted and the s o l i d was washed twice with water (5 ml) and freeze dried, giv-ing a c o l o r l e s s powder. This material was tra n s f e r r e d into small v i a l s and sealed under nitrogen i n a glove box. The v i a l s were stored over phosphorous pentoxide. When needed, the contents of the v i a l s were - 246 -tran s f e r r e d d i r e c t l y into anhydrous THF under anhydrous conditions i n an in e r t atmosphere. 8. Synthesis of 6,7-Dimethyl-cis-4a,5,8,8a-tetrahydro-l,4-naphthalenedione ( 3 7 ) 1 4 1 2,3-Dimethyl-l,3-butadiene (1.8 ml, 15.90 mmol) and 1,4-benzo-quinone (1.00 g, 9.25 mmol) were refluxed at 65°C f o r 2 h. The yellow s o l i d obtained was r e c r y s t a l l i z e d from pet. ether (65-110°C), affo r d i n g almost c o l o r l e s s c r y s t a l s (1.43 g, 81%). MP 113-114° ( l i t . 1 4 1 MP 115-117°C). IR (CHC1 3) 1680 (C-0) cm"1. NMR 5 6.58 (s, 2H, v i n y l i c - H ) , 3.10 (m, 2H, C4a and C8a methines), 2.20 (m, 4H, C5 and C8 methylenes), 1.63 (s, 6H, methyls). The spec-troscopic data f o r t h i s compound i s i d e n t i c a l to the l i t e r a t u r e d a t a . l c l 9. Synthesis of [o- [ a -(Trimethylsilyl)methyl]benzyl]acetate (70) To a s t i r r e d s o l u t i o n of sodium acetate (0.20 g, 2.40 mmol) i n f r e s h l y d i s t i l l e d a c e t i c anhydride (50 ml) was added [o- [ a -(trimethyl-silyl)methyl]benzyl]dimethylamine (65) (5.00 g, 22.50 mmol). Aft e r r e f l u x i n g f o r 24 h, ac e t i c anhydride was rotary evaporated and the r e s u l t i n g o i l was dissolved i n d i e t h y l ether (20 ml). The d i e t h y l ether s o l u t i o n was washed with 10% aqueous NaHC03 (10 ml x 2) sol u t i o n , dried - 247 over Na 2S04, and d i e t h y l ether was rotary evaporated to give a brown o i l which was d i s t i l l e d as a c o l o r l e s s l i q u i d (3.99 g, 77%). BP 55°C at 0.3 mmHg. IR (CHC1 3) 1720 (C=0) cm'1. NMR 6 7.34-7.02 (m, 4H, Ar-H), 5.08 (s, 2H, -0CH 2), 2.18 (s, 2H, -SiCH 2), 2.10 (s, 3H, methyl), 0.03 (s, 9H, -SiMe 3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 236 (M +, 58), 221 (44), 117 (22), 104 (100), 73 (55). Anal, calcd. f o r C 1 3 H 2 0 0 2 S i : C, 66.05; H, 8.52; found: C, 66.30; H, 8.60. 10. Synthesis o f [ o - [ a - ( T r i m e t h y l s i l y l ) m e t h y l ] b e n z y l ] c h l o r i d e (71)* (a) Hydrolysis of Acetate (70) A s o l u t i o n of acetate (70) (2.00 g, 8.47 mmol) i n methanol (10 ml) was refluxed with an aqueous s o l u t i o n of 10% KOH (20 ml) for 4 h. Organic compounds were extracted with d i e t h y l ether (30 ml x 3), washed with water (10 ml x 3) and drie d over Na2S04_ Diethyl ether was removed i n vacuo and the brownish o i l was d i s t i l l e d to y i e l d a c o l o r l e s s o i l (1.42 g, 86%) i d e n t i f i e d as [o-[a-trimethylsilyl)methyl]benzyl]alcohol (70a). Though t h i s compound i s mentioned i n r e f . 51, neither i t s synthesis nor i t s spectroscopic data has been reported. 248 -BP 70°C at 0.3 mmHg. IR (neat) 3300 (OH) cm"1. NMR 5 7.50-6.88 (m, 4H, Ar-H), 4.65 (s, 2H, -0CH 2), 2.19 (s, 2H, -SiCH 2), 1.92 (s, 1H, exchangeable OH), 0.10 (s, 9H, -SiMe 3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 194 (M+, 2), 122 (32), 107 (23), 104 (100), 91 (28), 77 (28). (b) Synthesis of [ o - f a - ( t r i m e t h y l s i l y l ) m e t h v l l b e n z y l l c h l o r i d e (71) A s o l u t i o n of the alcohol (70a) (1.00 g, 5.15 mmol) and Z n C l 2 (0.75 g, 5.50 mmol) i n 10 ml cone. HCl was refluxed f or 18 h. Water (5 ml) was added to the reac t i o n mixture and the organic compounds were extracted with d i e t h y l ether (20 ml x 3). The d i e t h y l ether layer was washed with 5% aqueous Na 2C0 3 s o l u t i o n (10 ml x 2) and then with water (10 ml x 2). The organic layer was dr i e d over Na 2S04 and the solvent was removed i n vacuo to y i e l d a c o l o r l e s s o i l which was p u r i f i e d by column chromatography with pet. ether (30-60°C) a f f o r d i n g a c o l o r l e s s o i l (0.71 g, 61%). BP 105°C at 0.3 mmHg. IR (neat) 2980, 2890, 1480, 1440, 1258, 740 cm"1. NMR 5 7.54-6.80 (m, 4H, Ar-H), 4.52 (s, 2H, -CH 2C1), 2.42 (s, 2H, -CH 2Si), 0.03 (s, 9H, -SiMe 3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 212 (M +, 20), 177 (15), 161 (28), 140 (21), 104 (100), 73 (40). 249 -11 . Reactions of [o-[a-(Trimethylsilyl)methyl]benzyl]trimethyl-ammonium Bromide ( 2 7 ) 5 1 (a) With Duroquinone To a s t i r r e d s o l u t i o n of the t i t l e compound (27) ( 2 . 4 4 g, 7.72 mmol) and duroquinone (3.80 g, 23.20 mmol) i n anhydrous CH3CN (50 ml), tetrab-utylammonium f l u o r i d e (TBAF) (4.04 g, 15.40 mmol) i n THF (15 ml) was added over a period of 30 min. A f t e r s t i r r i n g under nitrogen overnight at room temperature, water (10 ml) was added, and the organic compounds were extracted with d i e t h y l ether, d r i e d over N a S 0 4 and concentrated i n vacuo to a f f o r d a dark o i l (3.68 g). This was p u r i f i e d by f l a s h chroma-tography using 1:4 (v/v) EtOAc:pet. ether (30-60°C) gi v i n g a l i g h t yellow s o l i d (1.16 g). R e c r y s t a l l i z a t i o n from pet. ether (30-60°C) yi e l d e d almost c o l o r l e s s c r y s t a l s ( 0 .94 g, 44%) i d e n t i f i e d as 2 ,3 ,4a,9a-tetramethyl-cis - 4 a , 9 a , 9 , 1 0-tetrahydro - 1 , 4-anthracenedione (52). MP 84-85°C. IR (KBr) 1664 (C=0), 1610 (C=C) cm"1. NMR 6 7 .12-7 .02 (m, 4H, Ar-H), 3.35 (d, J = 17 Hz, 2H, benzylic hydrogens), 2.55 (d, J = 17 Hz, 2H, benzylic hydrogens), 1.98 (s, 6H, v i n y l methyls), 1.22 (s, 6H, 4 a , 9a methyls). UV (CH3CN) A m a x 249 (£ 90600), 350 (e 87). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 268 (M+, 3 4 ) , 253 (14), 240 ( 6 8 ) , 225 ( 1 0 0 ) , 210 ( 2 0 ) , 207 (30). Anal. calcd. f o r C 1 8H 2 o02: C, 80.56; H, 7.51; found: C, 80.45; H, 7.51. X-ray c r y s t a l structure analysis supports the above assigned 250 -structure. (b) With 2.3-Dimethvl-l.4-naphthalenedione Reaction, as above, between 2,3-dimethyl-1,4-naphthalenedione (4.00 g, 21.50 mmol), ammoniun s a l t (27) (6.80 g, 21.50 mmol) and TBAF (8.41 g, 32.20 mmol) i n anhydrous THF (50 ml) afforded an o i l . A f t e r work up and f l a s h chromatography using pet. ether (30-60°C):EtOAc (4:1, v/v), the compound corresponding to r f value 0.62 was i s o l a t e d and r e c r y s t a l -l i z e d from pet. ether (30-60°C) to give c o l o r l e s s c r y s t a l s (1.20 g, 20%) i d e n t i f i e d as 5a,lla-dimethyl-cis-5a,6,11,11a-tetrahydro-5,12-naphtha-cenedione (54). MP 101-102°C. IR (KBr): 1680 (C=0) cm'1. NMR S 8.05 (dd, J=6 6=3 Hz, 2H, aromatics 1 & 4) , 7.73 (dd, J=6 & 3 Hz, 2H, aromatics 2 6c 3), 7.17-7.04 (m, 4H, aromatics 7 and 10), 3.42 (d, J=16 Hz, 2H, benzylic hydrogens), 2.65 (d, J=16 Hz, 2H, benzylic hydrogens), 1.33 (s, 6H, methyls). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 290 (M +, 16), 275 (9), 262 (100), 247 (44), 229 (11). Anal. calcd. f o r C20H18O2: C, 82.73; H, 6.25; found: C, 82.47; H, 6.31. When the solvent from an EtOAc s o l u t i o n of t h i s compound was allowed to evaporate slowly, large, prism-shaped c r y s t a l s were formed. X-ray c r y s t a l structure analysis supports the assigned structure. - 251 -(c) With 2.5-Dimethyl-1.4-benzoquinone Reaction, as above, between 2,5-dimethyl-1,4-benzoquinone (0.86 g, 6.32 mmol), rig o r o u s l y dried ammonium s a l t (27) (1.00 g, 3.82 mmol) and anhydrous TBAF (1.65 g, 6.32 mmol) y i e l d e d a dark o i l . This o i l was p u r i f i e d by f l a s h column chromatography using benzene: EtOAc (19:1, v/v). The product corresponding to r f value 0.62 was i s o l a t e d and r e c r y s t a l l i z e d from pet. ether (30-60°C) to give b e a u t i f u l l i g h t yellow c r y s t a l s (0.15 g, 19%) i d e n t i f i e d as 2,4a-dimethyl-trans-4a,9a,9,10-tetrahydro-1,4-anthracenedione (50t): MP 119-120°C. IR (KBr) 1680 & 1660 (C=0) cm - 1. NMR 5 7.21-7.13 (m, 4H, Ar-H), 6.57 (br d, J = 2 Hz, 1H, v i n y l ) , 3.21-2.95 (m, 5H, benzylic hydrogens and methine at 9a), 2.06 (d, J = 2 Hz, 3H, v i n y l methyl), 1.15 (s, 3H, 4a methyl). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 240 (M +, 100), 225 (99), 212 (25), 197 (44), 179 (19), 141 (17), 128 (43), 115 (23), 96 (11), 69 (31). Anal. calcd. f o r C 1 6 H 1 6 0 2 : C, 79.97; H, 6.71; found; C, 80.00; H, 6.62. The structure of t h i s compound was further confirmed by synthe-s i z i n g t h i s product by an independent route (see page 257). (d) With 1.4-Benzoquinone Reaction, as before, between ammonium s a l t (27) (0.28 g, 0.9 mmol, 252 -benzoquinone (0.19 g, 1.8 mmol) and extremely anhydrous TBAF (0.33 g, 1.3 mmol) i n anhydrous CH3CN (10 ml), a f t e r 2 h y i e l d e d a yellow solu-t i o n . A f t e r work up and column chromatography with chloroform, the com-pound corresponding to r f value 0.75 was i s o l a t e d (0 .12 g, 65%) and i d e n t i f i e d as 1,4-anthracenedione (24a). MP 213-214°C ( l i t . 1 5 7 MP 216-218°). IR (CHCI3) 1662 (C=0) cm"1. NMR 6 8.15 (s, 2H, C9 & C 1 0, Ar-H) , 7.90 (m, 4H, remaining Ar-H) , 7.10 (s, 2H, v i n y l ) . Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 208 (M +, 100), 180 (19), 153 (50) , 126 (42). Another compound which was also present i n the r e a c t i o n mixture, was i d e n t i f i e d as hydroquinone (GC y i e l d 33%) by c o - i n j e c t i n g an authen-t i c sample i n the GC. The following v a r i a t i o n s i n t h i s r e a c t i o n were also t r i e d without any success i n synthesizing the desired adduct. A. Reaction was c a r r i e d out using 0.80 mole equivalent of absolutely anhydrous TBAF. B. Reaction was done at -36, 0 and 50 °C using the same molar r a t i o s as i n part (d). C. Commercial TBAF (containing up to 5% water) was used. D. Reaction i n the presence of 1 equivalent of 0.1 M HC1. E. Reaction using TBAF adsorbed on s i l i c a g e l . F. Reaction with KF i n 18-Crown-6 i n moist CH3CN. - 253 (e) Reaction with Tetraethyl-1,4-benzoquinone (66) Reaction as before was c a r r i e d out between ammonium s a l t (27) (0.11 g, 0.34 mmol), tetraethyl-1,4-benzoquinone (0.15 g, 0.68 mmol) and TBAF (0.18 g, 0.68 mmol) i n anhydrous CH3CN (15 ml). The re a c t i o n mixture was worked up as before and a f t e r column chromatography with pet. ether (30-60°C) and EtOAc (9:1, v/v), y i e l d e d an almost c o l o r l e s s o i l (0.046 g, 65%) i d e n t i f i e d as spiro-(5,5)-2,3-benz-6-methyleneundeca-7,9-diene (spiro-di-o-xylylene) (15a). IR (neat) 3030, 2857, 1587, 1492, 1449, 877, 740 cm"1. NMR S 7.00 (m, 4H, Ar-H), 5.80 (m, 4H, v i n y l i c - H ) , 4.93 (d, 2H, exo-vinylic-H), 2.80 (m, 4H, Benzylic-H), 2.00 (m, 2H, CH 2-CH 2-Ar). The spectroscopic data of t h i s sample are i d e n t i c a l with the pub-l i s h e d d a t a . 2 6 12. Reactions of [o-[Q-(Trimethylsilyl)methyl]benzyl]acetate (70) (a) With Duroquinone The r e a c t i o n between acetate (70) (0.10 g, 0.43 mmol), duroquinone (0.21 g, 1.26 mmol) and TBAF (0.22 g, 0.84 mmol) i n anhydrous CH3CN (5 ml), followed by the usual work up afforded 2,3,4a,9a-tetramethyl-cis-4a,9a,9,10-tetrahydro-1,4-anthracenedione (52) (0.07 g, 61%) whose properties were i d e n t i c a l to those reported above. 254 (b) With 1.4-Benzoquinone Reaction between acetate (70) (34 mg, 0.15 mmol), benzoquinone (31.3 mg, 0.29 mmol) and TBAF (72 mg, 0.23 mmol) i n anhydrous CH3CN (5 ml) was done under the same conditions as before. A f t e r the usual work up, the dark yellow product was i d e n t i f i e d as 1,4-anthracenedione (24a) (2-5%) whose properties were i d e n t i c a l to those reported e a r l i e r (see page 251). A second compound i s o l a t e d was i d e n t i f i e d as hydroquinone. 13. Reaction of [o-(a-[Trimethylsilyl]methyl)benzyl]chloride ( 7 1 ) 5 1 with 1,4-Benzoquinone Reaction was c a r r i e d out between chloride (71) (43 mg, 0.20 mmol), benzoquinone (43 mg, 0.40 mmol) and TBAF (76.00 mg, 0.30 mmol). A f t e r work up, a yellow compound was i s o l a t e d and i d e n t i f i e d as 1,4-anthra-cenedione (24a) (30 mg, 72%) whose properties were i d e n t i c a l to the com-pound i s o l a t e d before. The other compound i s o l a t e d was i d e n t i f i e d as hydroquinone. 255 14. Reactions of 6,7-Dimethyl-cis-4a,5,8,8a-tetrahydro-l,4-naphthalenedione (37) (a) With anhydrous TBAF To a s t i r r e d s o l u t i o n of the adduct (37) (0.50 g, 2.63 mmol) i n anhydrous CH3CN (20 ml) maintained under N 2, was added TBAF (0.69 g, 2.63 mmol). A f t e r one hour of s t i r r i n g , water (5 ml) was added and the organic compounds were extracted with d i e t h y l ether (2 x 20 ml). The combined organic layers were washed with water (10 ml), drie d over NaS04, and the ether was rotary evaporated to give a brown s o l i d (0.48 g). This was suspended i n CHCI3 (5 ml) and the insolubles were f i l t e r e d o f f (0.38 g, 76%) and i d e n t i f i e d as 6,7-dimethyl-5,8-dihydro-1,4-naphthoquinol (67): MP 177-78°C ( l i t . 2 5 4 MP 180-181°C). IR (KBr) 3150 (OH) cm"1. NMR (d6-DMS0) 6 8.40 (br s, 2H, exchangeable, 2 x OH), 6.40 (s, 2H, ArH), 3.08 (s, 4H, C(5) and C(8) hydrogens), 1.72 (s, 6H, 2 x CH 3). Mass Spectrum, m/e (M +, 290). (b) With Triethylamine A r e a c t i o n mixture of adduct (37) (0.10 g, 0.52 mmol) and t r i e t h y -lamine (0.05 g, 0.52 mmol) i n anhydrous CH3CN (3 ml) was s t i r r e d at room temperature f o r 4 hours. The solvent was removed i n vacuo, the brownish - 256 -crude was washed with chloroform (2 ml) and f i l t e r e d g i v i n g a brownish s o l i d (0.09 g, 90%). This product had i d e n t i c a l p h y s i c a l properties as reported above (67). 15. Reactions of 3,6-Dihydrobenzo[b]oxathiin-2-oxide ( 6 1 ) 5 8 " 6 3 (a) With p-Benzoquinone A s o l u t i o n of s u l t i n e (61) (l.OOg, 5.95 mmol) and f r e s h l y sublimed p-benzoquinone (0.96 g, 8.92 mmol) i n anhydrous benzene (10 ml) was refluxed f o r 1.75 h. Benzene was removed i n vacuo to give an orange s o l i d , which a f t e r two quick r e c r y s t a l l i z a t i o n s from methanol, afforded off-white needles (0.60 g, 48%) i d e n t i f i e d as cis-4a,9a,9,10-tetra-hydro-1 ,4-anthracenedione (47). MP 122-23°C. IR (KBr) 1680 (C=0) cm - 1. NMR 6 7.18-7.06 (m, 4H, Ar-H), 6.72 (s, 2H, v i n y l s ) , 3.40 (m, 2H, 4a, 9a methines) , 3.32 (dd, J = 18 <St 6 Hz, 2H, benzylic hydrogens), 2.92 (dd, J •= 18 & 4 Hz, 2H, benzylic hydrogens). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 212 (M+, 100), 195 (69), 184 (32), 165 (75), 152 (65), 141 (30), 128 (75), 115 (45). Anal. calcd. f o r C 1 4 H 1 2 ° 2 : c> 79.23; H, 5.70; found: C, 79.00; H, 5,50. 257 -(b) With Toluquinone The re a c t i o n was c a r r i e d out between s u l t i n e (61) (1.00 g, 5.95 mmol) and toluquinone (1.02 g, 8.37 mmol) as described above. A f t e r r e c r y s t a l l i z a t i o n from methanol, l i g h t yellow needles were obtained (0.80 g, 60%) i d e n t i f i e d as 2-methyl-cis-4a,9a,9,10-tetrahydro-1,4-anthracenedione (48). MP 110-11°C. IR (KBr) 1690 (OO) , 1620 (OC) cm"1. NMR S 7.15-7.06 (m, 4H, Ar-H), 6.58 (q, J = 2 Hz, 1H, v i n y l ) , 3.42-3.30 (m, 2H, 4a, 9a, methines), 3.37 (m, 2H, benzylic hydrogens), 3.20 (m, 2H, benzylic hydrogen), 2.92 (m, 2H, ben z y l i c hydrogens), 2.02 (d, J = 2 Hz, 3H, methyl). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 226 (M+, 44), 211 (33), 198 (100), 183 (46), 165 (72), 152 (33), 141 (30), 128 (90), 115 (55). Anal, calcd. f o r C 1 4 H 1 4 0 2 : C, 79.62; H, 6.24; found; C, 79.83; H, 6.29. (c) With 2.5-Dimethvl-l.4-benzoquinone Reaction, as before, between s u l t i n e (61) (1.00 g, 5.95 mmol) and 2,5 - dimethyl-1,4-benzoquinone, gave, a f t e r r e c r y s t a l l i z a t i o n of the crude product from methanol, a l i g h t yellow s o l i d (0.88 g, 62%): i d e n t i -f i e d as 2,4a-dimethyl-cis-4a,9a,9,10-tetrahydro-1,4-anthracenedione (49c) . - 258 -MP 80-81°C. IR (KBr) 1680 (C=0), 1620 (C=C) cm - 1. NMR 8 7.17-7.00 (m, 4H, Ar-H), 6.52 (q, J = 1.5 Hz, 1H v i n y l ) , 3.38 (dd, J = 17 and 5 Hz, 1H, benzylic hydrogen at 9), 3.17 (d, J = 16 Hz, 1H, benzylic hydrogen at 10), 3.06 (m, 1H, 9a methine), 2.93 (dd, J = 17 and 6 Hz, 1H, b e n z y l i c hydrogen at 9) , 2.53 (d, J = 16 Hz, 1H, benzylic hydrogen at 10), 2.00 (d, J = 1.5 Hz, 1H, v i n y l methyl), 1.35 (s, 3H, 4a methyl). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 240 (M+, 18), 225 (16), 212 (85), 197 (100), 179 (28), 128 (47). Anal, calcd. f o r C 1 6 H 1 6 0 2 : C, 79.97; H, 6.71; found: C, 80 .01; H, 6.60. X-ray c r y s t a l structure analysis supports the structure assigned above. When a s t i r r e d s o l u t i o n of t h i s compound i n CH3CN was treated at room temperature with triethylamine, i t y i e l d e d a compound whose proper-t i e s were i d e n t i c a l to the trans product (50t, see page 250). (d) With 1 .4-Naphthalenedione Reaction, as before, was c a r r i e d out between s u l t i n e (61) (1.00 g, 5.95 mmol) and 1 ,4-naphthalenedione (1.30 g, 8.22 mmol). The crude rea c t i o n mixture was c r y s t a l l i z e d to give very f i n e c o l o r l e s s needles (0.80 g, 52%) i d e n t i f i e d as cis - 5 a , 1 1 a ,6,ll-tetrahydro - 5 , 1 2-naphthacene-dione (55). MP 156-157°C. - 259 -IR (KBr) 1680 (OO) cm'1. NMR 6 8.08 (dd, J = 6 Hz and 3 Hz, 2H, Ar-H 1 and 4), 7.75 (dd, J = 6 Hz and 3 Hz, 2H, Ar H 2 and 3), 7.17-7.07 (m, 4H, Ar-H 7-10), 3.57 (m, 2H, 5a,11a methines), 3.30 (m, 2H, benzylic hydrogens), 2.99 (m, 2H, benz y l i c hydrogens). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) : 262 (M +, 100), 245 (59), 244 (89), 215 (46), 202 (13), 128 (15). Anal, calcd. f o r C 1 8 H 1 4 0 2 : C, 82.42; H, 5.38; found: C, 82.15; H, 5.29. (e) With 2.3.5-Trimethyl-l.4-benzoquinone Reaction, as before, between s u l t i n e (61) (1.28 g, 7.61 mmol) and 2,3,5-trimethyl-1,4-benzoquinone (1.58 g, 10.52 mmol), y i e l d e d a f t e r column chromatography with pet. ether (30-60°C):EtOAc (9:1, v/v) and r e c r y s t a l l i z a t i o n from pet. ether (30-60°C), c o l o r l e s s prisms (0.64 g, 33%): i d e n t i f i e d as 2,3,4a-trimethyl-cis-4a,9a,9,10-tetrahydro-1,4-anthracenedione (51) . MP 107-108°C. IR (KBr) 1672 (OO) , 1621 (OC) cm"1. NMR 6" 7.18-6.97 (m, 4H, Ar-H), 3.35 (dd, J = 16 Hz and 4 Hz, 1H, benz y l i c H at C(9)), 3.17 (d, J = 16 Hz, 1H, benzylic H at C(10)), 3.05 (overlapping dd appears l i k e a t, J = 4 Hz, 1H, methine at C(9a)), 2.52 (d, J = 16 Hz, 1H, benzylic H at C(10)), 2.00 (s, 3H, v i n y l i c CH 3), 1.98 (s, 3H, v i n y l i c CH 3), 1.35 (s, 3H, CH 3 at C(4a)). - 260 -Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 254 (M+, 8), 239 (9), 226 (99), 211 (100), 193 (32), 178 (8), 141 (19), 128 (42), 115 (20), 83 (41). Anal, calcd. f o r C 1 7 H 1 8 0 2 : C, 80.28; H, 7.13; found: C, 80.37; H, 7.15. X-ray c r y s t a l structure analysis supports the assigned struc-ture. When t h i s compound was r e c r y s t a l l i z e d from methanol, i t produced plates l i k e c r y s t a l s . The i r spectrum and the MP of the plates were i d e n t i c a l to the i r spectrum and the MP of the prisms reported above. 16. Reduction of 2,3,4a,9a-Tetramethyl-cis-4a,9a,9,10-tetrahydro-l,4-anthracenedione (52) (a) With Sodium Borohvdride To a s t i r r e d s o l u t i o n of anthracenedione (52) (1.60 g, 5.97 mmol) i n 20 ml methanol and THF (19:1, v/v), maintained at 0°C, was added NaBH4 (0.30 g, 7.93 mmol) slowly over a period of 5 min. A f t e r 20 min., the r e a c t i o n was quenched with aqueous ammonium chlo r i d e s o l u t i o n . The organic compounds were extracted with d i e t h y l ether (2 x 50 ml), dried over Na 2S04, rotary evaporated, and the c o l o r l e s s o i l obtained was p u r i -f i e d by f l a s h column chromatography using pet. ether (30-60°C) and EtOAc (4:1, v/v). The compound corresponding to r f value 0.66 was i s o l a t e d and r e c r y s t a l l i z e d from methylcyclohexane a f f o r d i n g c o l o r l e s s needles (0.89 g, 55%) i d e n t i f i e d as 4a, 9a, 9 ,10-tetrahydro-4/3-hydroxy-2 , 3 ,4a/3, 9a0-tetramethyl-l(4H)anthracenone (56B). 261 -MP 162-163°C. IR (KBr) 3484 (OH), 1651 (C-O), 1629 (C=C) cm"1. NMR S 7.16-7.00 (m, 4H, Ar-H), 4.31 (d, J = 8 Hz, 1H, collapses to a s i n g l e t a f t e r D 20 exchange, CH-OH), 3.10 (d, J = 18 Hz, 1H, benzylic H), 3.05 (d, J = 18 Hz, 1H, benzylic H), 2.56 (d, J = 18 Hz, 1H, ben-z y l i c H), 2.44 (d, J = 18 Hz, benzylic H), 1.99 (d, J = 8 Hz, 1H, exchangeable, OH), 1.96 (s, 3H, C(3)-CH 3), 1.82 (s, 3H, C(2) CH 3), 1.18 (s, 3H, CH 3), 0.98 (s, 3H, CH 3). UV A m a x (CH3CN) 246 (c 20280), 328 (e 87). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 270 (M +, 10), 252 (48), 237 (23), 225 (15), 209 (20), 166 (100), 141 (26), 112 (51), 104 (36). Anal, calcd. f o r C 1 8 H 2 2 0 2 : C, 79.96; H, 8.20; found: C, 80.10; H, 8.40. Another compound corresponding to r f value 0.42 was i s o l a t e d and r e c r y s t a l l i z e d from pet. ether (30-60°C) to y i e l d b e a u t i f u l c r y s t a l s (0.54 g, 34%) i d e n t i f i e d as 4a,,9a,9,10-tetrahydro-4Q-hydroxy-2,3,-4a/?, 9a/3- tetramethyl-1 (4H) anthracenone (57A) . MP 143-144°C. IR (KBr) 3457 (OH), 1647 (C-0), 1632 (C=0) c m 4 . NMR 6 7.15-6.94 (m, 4H, Ar-H), 4.42 (d, J = 6 Hz, 1H, collapses to a s i n g l e t a f t e r D 20 exchange, CH-OH), 3.46 (d, J = 18 Hz, 1H, benzylic H), 2.82 (d, J = 18 Hz, 1H, benzylic H), 2.60 (d, J = 18 Hz, 1H, ben-z y l i c H), 2.55 (d, J = 18 Hz, 1H, benzylic H), 2.25 (d, J = 6 Hz, 1H, exchangeable, OH), 2.00 (s, 3H, C(3) CH 3), 1.77 (s, 3H, C(2) CH 3), 1.16 (s, 3H, CH 3), 1.14 (s, 3H, CH 3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 270 (M+, 3), 252 (100), 237 - 262 -(46), 224 (17), 209 (62), 195 (12), 169 (28), 141 (22), 128 (28), 104 (24). Anal, calcd. f o r C 1 8H 2202: C, 79.96; H, 8.20; found: C, 79.91; H, 8.30. The structure assigned above was supported by X-ray c r y s t a l l o -graphy . (b) With Methyl l i t h i u m To a s t i r r e d s o l u t i o n of anthracenedione (52) (0.54 g, 2.00 mmol) i n f r e s h l y d i s t i l l e d anhydrous THF (20 ml) maintained under N2, was added methyl l i t h i u m (0.88 g, 2.00 mmol) i n 1 min. The reac t i o n mixture which turned yellow, was allowed to s t i r f o r 1 h and then quenched with a d i l u t e aqueous s o l u t i o n of NH4CI. A f t e r e x t r a c t i n g with d i e t h y l ether (3 x 50 ml) and drying over Na2S04, the solvent was removed to a f f o r d c o l o r l e s s powder (0.52 g). A GC chromatogram indicated that i t was a mixture of two major products i n 80:20 r a t i o . This mixture was recrys-t a l l i z e d from acetone to y i e l d large, b e a u t i f u l c r y s t a l s (0.35 g, 62%) i d e n t i f i e d as 4a, 9a, 9 ,10-tetrahydro-4/3-hydroxy-2 , 3 ,4a,4a/?, 9a/3-penta-methyl-l(4H)anthracenone (59A). MP 171-172°C. IR (KBr) 3498 (OH), 1655 (C=0), 1635 (C=C) 1597 cm'1. NMR (CD3OD) S 7.17-6.92 (m, 4H, Ar-H), 3.22 (d, J = 18 Hz, 1H, benzylic H), 2.58 (m, 3H, remaining benzylic H), 2.00 (s, 3H, C(3)-CH 3), (This peak was covered by the solvent peak however i t became cl e a r i n DMSO d 6 ) , 1.70 (s, 3H, C(2)-CH 3), 1.36 (s, 3H, CH 3), 1.26 (s, 3H, CH3), 263 -1.06 (s, 3H, CH 3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 284 (M +, 15), 266 (17), 255 (8), 223 (30), 197 (8), 165 (12), 126 (42), 83 (100). Anal, calcd. for C 1 9H 240 2: C, 80.24; H, 8.51; found: 80.17; H, 8.58. The assigned structure was also supported by X-ray c r y s t a l l o -graphy . When t h i s r e a c t i o n was quenched with d i l u t e HCl, no product corre-sponding to an alcohol was i s o l a t e d ; instead the product i s o l a t e d was an o i l (81%) i d e n t i f i e d as 2,3,4a,9a-tetramethyl-4-exo-methylene-cis-4a,9a,9,10-tetrahydro-l-anthracenone (72). IR (neat) 1662 (C=0), 1597 (C=C) cm - 1. NMR S 7.16-6.90 (m, 4H, Ar-H), 5.40 (s, 1H, v i n y l i c - H ) , 5.30 (s, 1H, v i n y l i c - H ) , 3.30 (d, J = 18 Hz, 1H, benzylic H), 3.10 (d, 18 Hz, 1H, benz y l i c H), 2.57 (d, 18 Hz, 1H, benzylic H), 2.45 (d, J = 18 Hz, ben-z y l i c H), 2.08 (s, 3H, v i n y l CH 3), 1.88 (s, 3H, v i n y l CH 3), 1.18 (s, 3H, CH 3), 1.10 (s, 3H, CH 3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 266 (M +, 100), 251 (42), 237 (20), 223 (38), 209 (21), 181 (14), 137 (45), 104 (76). HRMS calcd. f o r C 1 9H 2 20: 266.1672; found: 266.1671. 17. Synthesis of 4a, 9a, 9,10-Tetrahydro-4/3-(acetyloxy)-2 , 3 , 4a/3, 9aB-tetramethyl-l(4H)anthracenone (58B) To a suspension of the alcohol (58B) (0.05 g, 0.19 mmol) i n acetic anhydride (3 ml) was added pyridine (0.90 ml) and the reac t i o n mixture - 264 was s t i r r e d overnight. I t was d i l u t e d with water (20 ml), extracted with chloroform ( 3 x 5 ml). The combined organic layers were treated with cone HC1 ( 3 x 3 ml) and separated. The organic layer was washed with a saturated s o l u t i o n of NaHC03 ( 2 x 5 ml) and then with water (5 ml), dri e d over Na2S0 4, rotary evaporated and the crude product was r e c r y s t a l l i z e d from cyclohexane to a f f o r d large prism-shaped c o l o r l e s s c r y s t a l s (0.055 g, 93%) i d e n t i f i e d as 4a,9a,9,10-tetrahydro-4/?-(acetyloxy)-2,3,4a£,9aB-tetramethyl-1(4H)anthracenone (58B). MP 132-133°C. IR (KBr) 1742 (Me-C-0), 1665 (C-0), 1641 (C=C) cm"1. NMR 5 7.22-6.92 (m, 4H, Ar-H), 5.65 (s, 1H, CH-OAc), 3.25 (d, J = 18 Hz, 1H, b e n z y l i c H), 2.57 (3H, benzylic H), 2.18 (s, 3H, COCH3), 1.83 (s, 6H, 2 x v i n y l i c methyls), 1.23 (s, 3H, CH3), 1.02 (s, 3H, CH3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 312 (M +, 9), 270 (10), 252 (100), 237 (45), 223 (17), 209 (57), 166 (64), 142 (12), 130 (21), 112 (61), 104 (16). Anal, calcd. f o r C20H24O3: C, 76.89; H, 7.74; found: C, 77.10; H, 7.69. The above assigned structure was also supported by X-ray c r y s t a l l o g r a p h i c data. 18. Photolysis of 2,4a-Dimethyl-cis-4a,9a,9,10-tetrahydro-l,4-anthracenedione (49c) A s o l u t i o n of the adduct (49c) (0.11 g, 0.46 mmol) i n CH3CN (200 ml) was photolyzed for 2 h using a Pyrex f i l t e r transmitting at X —290 265 -nm. The solvent was removed i n vacuo. and the r e s u l t i n g yellowish crys-t a l s were r e c r y s t a l l i z e d from pet. ether (30-60°C) to y i e l d c o l o r l e s s c r y s t a l s (0.10 g, 91%) i d e n t i f i e d as 3,4-benzo-6,9-dimethyltricyclo-[4.4.0.0 2' 9]decan-7,10-dione (49CB). MP 81-82°C. IR (KBr) 1765 (C=0, cyclobutanone), 1715 (C=0) cm"1. NMR 5 7.27-7.04 (m, 4H, Ar-H), 3.36 (d, J - 6 Hz, 1H, C(l) or C(2)-H), 3.20 (d, J = 6 Hz, 1H, C(l) or C(2)-H), 2.78 (AB q, J = 16 Hz, 2H, benzylic-H), 2.39 (AB q, J = 18 Hz, 2H, C(5) methylenes), 1.32 (s, 3H, CH 3), 1.23 (s, 3H, CH 3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 240 (M +, 5), 212 (10), 197 (5), 143 (100), 128 (29), 115 (10). Anal. calcd. f or C 1 6 H 1 6 0 2 : C, 79.97; H, 6.71; found: C, 80.21; H, 6.71. (b) In the S o l i d State One s i n g l e c r y s t a l of the adduct (49c) (2-5 mg) was photolyzed at 0°C f o r 30 min with a N 2 l a s e r . The . c r y s t a l was dissolved i n EtOAc and analyzed by GC, which showed the formation (8%) of only one product. However, when the re a c t i o n was allowed to go for longer periods of time, an o i l was noticed on the wall of the photolysis tube i n d i c a t i n g that the c r y s t a l had melted. The i d e n t i t y of t h i s product was confirmed by c o i n j e c t i o n with the i s o l a t e d product (49CB). 266 -(c) In A c e t o n i t r i l e at -40° When a 0.01 M s o l u t i o n of the dimethyl adduct (49c) i n CH3CN was photolyzed at -40°C with a N 2 Laser for 5-10 min, only one photoproduct was formed, which was i d e n t i f i e d as (49CB). 19. Photolysis of 2,4a-Dimethyl-trans-4a,9a,9,10-tetrahydro-l,4-anthracenedione (50t) (a) In A c e t o n i t r i l e A s o l u t i o n of the trans adduct (50t) (2 mg/ml) i n CH3CN was photolyzed for up to 1 h using a N 2 l a s e r . Luminescence was observed and no photoproducts were detected by GC and t i c (pet. ether (30-60°C):Et0Ac (80:20, v/v). (b) In KBr A KBr p e l l e t containing 0.80-1.00% (w/w) of trans-adduct (50t) was photolyzed f o r 40 min using a N 2 l a s e r . No rea c t i o n could be observed by IR. Later the same p e l l e t was photolyzed with a 450 W lamp (A > 290 nm) for 3 h. No change i n the i n i t i a l i r spectra was noticed. - 267 20. Photolysis of 2,3,4a,9a-Tetramethyl-cis-4a,9a,9,10-tetrahydro-1,4-anthracenedione ( 5 2 ) 1 8 2 (a) In A c e t o n i t r i l e A s o l u t i o n of the tetramethyl adduct (52) (0.40 g, 1.49 mmol) i n CH3CN (250 ml) was photolyzed using a Pyrex f i l t e r (A > 290 nm) f o r 2 h. A GC analysis of t h i s reaction showed that only two products i n >96% and <4% y i e l d s formed. The solvent was removed i n vacuo and the r e s u l t i n g s o l i d was p u r i f i e d by f l a s h column chromatography using pet. ether (30-60°C): EtOAc (9:1, v/v). The t i c spot corresponding to r f value 0.61 was i s o l a t e d and r e c r y s t a l l i z e d from pet. ether (30-60°C) to y i e l d large c o l o r l e s s prisms (0.34 g, 85%), i d e n t i f i e d as 3,4-benzo-l,6,8-endo,9-tetramethyltricyclo[4.4.0.0 2• 9]decan-7,10-dione (52CB). MP 89.5-90°C. IR (KBr) 1745 (C=0, cyclobutanone), 1700 (C=0) cm"1. NMR 6 7.25-7.07 (m, 4H, Ar-H), 3.01 (s, 1H, ben z y l i c methine), 2.81 (AB q, J = 18 Hz, ben z y l i c methylenes), 2.23 (q, J = 8 Hz, 1H, -CH-CH3), 1.33 (s, 3H, CH 3), 1.24 (s, 3H, CH3), 1.19 (s, 3H, CH3), 1.05 (d, J = 8 Hz, 3H, CH-CH3). When the quartet at 5 2.23 was i r r a d i a t e d , the doublet at S 1.05 collapsed to a s i n g l e t . Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 268 (M+, 10), 240 (22), 225 (8), 197 (7), 157 (100), 156 (34), 142 (22), 83 (19). Anal. calcd. f or C 1 8H 2()02: C, 80.56; H, 7.51; found: C, 80.46; H, 7.43. X-ray crystallography confirmed the structure and stereo-chemistry a s s i g n e d . 1 7 ^ 268 The other compound corresponding to r f 0.57 was also i s o l a t e d and r e c r y s t a l l i z e d from pet. ether (30-60°C) to a f f o r d c o l o r l e s s needles (12 mg, 3%), i d e n t i f i e d as 3,4-benzo-l,6,8,9-endo-tetramethyltri-cyclo-[4.4.0.0 2' 8]decan-7,10-dione (52CP). MP 133-134°C. IR (KBr) 1735 (C=0) cm - 1. NMR 6 1.25-1.Ok (m, 4H, Ar-H), 2.92 (s, 1H, ben z y l i c methine), 2.80 (AB q, J = 16 Hz, 2H, benzylic methylenes), 2.32 (q, J = 8 Hz, 1H, -CH-CH3), 1.07 (s, 3H, CH3), 1.04 (s, 3H, CH3), 0.96 (d, J = 8 Hz, 3H, -CH-CH3), 0.92 (s, 3H, CH 3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 268 (M +, 66), 240 (3), 225 (14), 197 (13), 157 (65), 156 (100), 142 (22), 141 (22), 115 (9). Anal, calcd. f o r C 1 8 H 2 0 0 2 : C, 80.56; H, 7.51; found: C, 80.50; H, 7.44. (b) C r y s t a l Photolysis When a si n g l e c r y s t a l of the adduct (52) was photolyzed f or up to 20 min (less than 5% conversion) using the N 2 l a s e r or the 450 W lamp (A > 290 nm), the only product observed was cyclobutanone (52CB). However, when the r e a c t i o n was continued f or longer periods of time (1-1.5 h), the c r y s t a l melted and showed the formation of both products i n 30:1 r a t i o (52CB:52CP) for 30% reaction. - 269 -(c) Solvent and Wavelength Dependence Photolysis was performed using the same general procedure as before. The r e s u l t s are summarized i n Table 11. (d) Photolysis At Low Temperatures The photolysis of the adduct (52) at a low temperature was c a r r i e d out using the N 2 l a s e r . A s o l u t i o n of the adduct (52) (0.10 M) i n CH3CN:H20 (50:1, v/v) was used i n a l l cases. The required temperature was achieved by s e l e c t i n g an appropriate solvent/Dry Ice m i x t u r e 2 5 1 or by ic e and i c e / s a l t mixtures. The adduct (52), maintained at the desired temperature i n a transparent Dewar f l a s k containing the coolant, was photolyzed for 5-10 min. The products were analyzed by GC. The r e s u l t s obtained are shown i n Table 12. (e) S e n s i t i z a t i o n with Benzophenone A 0.10 M s o l u t i o n of the adduct (52) and a 1.00 M s o l u t i o n of benzophenone i n methanol were prepared. Using these two solutions and by d i l u t i n g to the desired concentration, f i v e d i f f e r e n t concentrations of the s e n s i t i z e r with a constant adduct concentration (1.00 x 10~ 2 M) were prepared. They were a l l photolyzed for the same amount of time using a 450 W lamp f i t t e d with a uranium glass f i l t e r (A > 330 nm). The r e s u l t s are given i n Table 13. - 270 Table 11: Photoproducts i n D i f f e r e n t Solvents and at Di f f e r e n t Wave Lengths % % % A Solvent Conv. Cyclo- Cyclo-(nm) butanone pentanone (52CB) (52CP) >290 CH3CN/H20 95 96 : 4±0.5 (50:1, v/v) C 6H 6 90 97 : 3±0.5 t-BuOH/benzene 87 97 : 3±0.5 (4:1, v/v) MeOH 75 76 : 24±1 >330 CH3CN/H20 41 97 : 3±0.5 (50:1, v/v) C 6H 6 10 96 : 3±0.5 7 337 CH3CN/H20 4 80 : 20±1 N 2 Laser (50:1, v/v) >313 CH3CN/H20 1 45 : 55±2 (50:1, v/v) 9 Sun lamp t-BuOH/benzene 37 97 : 3±0.5 >290 (40:1, v/v) - 271 Table 12: Temperature Dependent Products Ratio _ _ Temperature % Conv. Cyclo- Cyclo-butanone pentanone (52CB) (52CP) 1 -41°C 5 40 : 60±2 2 -15°C 7 44 : 56±1 3 -8°C 12 66 : 34±1 4 +0°C 15 76 : 24±1 5 (RT) 20°C 35 81 : 19±1 Table 13: S e n s i t i z a t i o n of the Adduct (52) with Benzophenone i n Methanol Adduct S e n s i t i z e r % % % cone. cone. Conv. Cyclo- Cyclo-pentanone butanone (xl0" 2M) (xl0" 2M) 52CP 52CB 1 1.00 0 4 24 : 76±2 2 1.00 0.2 33 6 : 94±1 3 1.00 0.4 36 5 : 95±1 4 1.00 0.8 53 3 : 9710.5 5 1.00 1.0 74 2 : 98±0.5 - 272 -(f) Photolysis i n Deuteriomethanol (CH3OD) A 0.01 molar s o l u t i o n of the adduct (52) was photolyzed with a 450 W lamp (A > 330 nm) for 30 min. The products formed were analyzed by GCMS. The peak corresponding to the cyclopentanone (52CP) showed 55% deuterium incorporation a f t e r corrected f o r M+l peak. (g) Photolysis of Crystals at -41°C Crys t a l s of the adduct (52) maintained at -41°C were photolyzed with the N 2 l a s e r f o r 50 min. A GC analysis showed formation of only one product, which was i d e n t i f i e d as the cyclobutanone (52CB) by coin-j e c t i o n with the photoproduct previously i s o l a t e d . (h) Reaction of Cyclobutanone (52CB) with a Base A s o l u t i o n of cyclobutanone (52CB) (134 mg, 0.05 mmol) and KOH (70 mg, 1.25 mmol) i n 40% (v/v) aqueous dioxane s o l u t i o n (10 ml) was refluxed f o r 24 h. The orange re a c t i o n mixture was treated with a c e t i c a c i d (1 ml) and the organic compounds were extracted with d i e t h y l ether (20 ml x 2). Excess HOAc was washed out with NaHC03 s o l u t i o n (satu-rated, 5 ml x 2). The l i g h t yellow organic layer was dried over Na2S04, and d i e t h y l ether was removed i n vacuo to y i e l d a l i g h t yellow s o l i d ; (120 mg, 90%). An i r spectrum and the GC ret e n t i o n time of t h i s com-- 273 pound were i d e n t i c a l to the i r spectrum and GC r e t e n t i o n time of the duroquinone adduct (52). 21. Photolysis of 2,3,4a,6,7,8a-Hexamethyl-cis-4a,5,8,8a-tetrahydro-1,4-naphthalenedione (36) (a) At Low Temperatures i n CH3CN As before, a 0.10 molar s o l u t i o n of the adduct (36), maintained at the desired temperature i n an appropriate solvent/dry i c e or i c e / s a l t bath was photolyzed f o r 5-10 min with the N 2 l a s e r . The r e a c t i o n mix-ture was analyzed by GC. Since a l l three photoproducts had been i s o l a t e d and characterized before,1''- no attempt was made to i s o l a t e them. However, they were i d e n t i f i e d as 1,3,4,6,8,9-hexamethyl-5-hydroxy-tricyclo[4.4.0.0 5• 9]deca-3,7 -dien-2 - one (36EA), 1,3,4,6,8,9-hexamethyl-t r i c y c l o [ 4 . 4 . 0 . 0 3 - 1 0 ] d e c - 8 -ene-2,5 -dione (36CB), 1,3,4,6,8,9-hexa-methyl-tricyclo[4.4.0.0 3' 7]dec-8-ene-2,5-dione (36CP) by GC analysis. The r e s u l t s of the low temperature and high temperature photolyses are summarized i n Table 14. (b) At High Temperature i n CH3CN Photolysis was conducted as above using a 0.10 molar s o l u t i o n of the hexamethyl adduct (36). The required temperature was maintained by - 274 -Table 14: Photolysis of hexamethyladduct (36) at various temperatures % % % % Temperature conv. Cyclo- Cyclo- Enone-(°C) butanone pentanone alcohol 36CB 36CP 36EA 1 - 32 4 3 : 5 : 92±0.5 2 - 10 7 4 : 3 : 9310.5 3 0 8 7 : 4 : 8910.5 4 +22 40 17 : 8 : 7511.0 5 +64 47 25 : 10 : 6511.0 6 +78 29 26 : 7 : 6711.5 r e f l u x i n g the appropriate solvent i n a two necked round-bottomed f l a s k . The r e s u l t s are shown i n Table 14. 22. Photolysis of 2,3,4a-Trimethyl-cis-4a,9a,9,10-tetrahydro-l,4-anthracenedione (51) (a) In A c e t o n i t r i l e The trimethyl adduct (51) (180 mg, 0.71 mmol) was photolyzed (A >330 nm) for 38 h i n CH3CN (250 ml) with 450 W lamp. A GC analysis at - 275 t h i s time showed that two products had formed i n 57% and 43% y i e l d s . A c e t o n t r i l e was removed i n vacuo and the yellow o i l obtained was p u r i -f i e d by column chromatography with pet. ether:EtOAc (9:1, v/v). The t i c spot corresponding to r f value 0.60 was i s o l a t e d and r e c r y s t a l l i z e d from cyclohexane, a f f o r d i n g c o l o r l e s s c r y s t a l s (65 mg, 36%), i d e n t i f i e d as 3,4-benzo-6,8-endo,9 -trimethyltricyclo[4.4.0.0 2' 9]decan-7,10-dione (51CB). MP 172-173°C. IR (KBr) 1765 (C=0, cyclobutanone), 1705 (C=0) cm"1. NMR cS 7.22-7.04 (m, 4H, Ar-H), 3.38 (d, J = 7 Hz, 1H, C(l) or C(2)-H), 3.19 (d, J = 7 Hz, 1H, C(l) or C(2)-H), 2.80 (AB q, J = 18 Hz, 2H, benzylic-H at C(5)), 2.22 (q, J = 8 Hz, 1H, -CH-CH3), 1.32 (s, 3H, CH 3), 1.29 (s, 3H, CH 3), 1.05 (d, J = 8 Hz, 3H, -CH-CH3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 254 (M+, 6), 226 (25), 198 (4), 183 (5), 155 (7), 143 (100), 128 (25), 115 (8), 83 (34). Anal. calcd. f o r C 1 7 H 1 8 0 2 : C, 80.28; H, 7.13; found: C, 80.10; H, 7.12. The other compound corresponding to r f value 0.54 was also i s o l a t e d and r e c r y s t a l l i z e d from pet. ether (30-60°C) to a f f o r d c o l o r l e s s crys-t a l s (55 mg, 31%), i d e n t i f i e d as 3,4-benzo-1,8-endo,9-trimethyltricyclo-[4.4.0.0 2' 9]decan-7,10-dione (51CB'). MP 101-102°C. IR (KBr) 1765 (C=0, cyclobutanone), 1720 (C=0) cm"1. NMR 5 7.32-7.12 (m, 4H, Ar-H), 3.17-2.85 (m, 4H, benzylic and C(6)-H), 2.17 (q, J = 7 Hz, 1H, -CH-CH3), 1.32 (s, 3H, CH 3), 1.25 (s, 3H, CH 3), 1.05 (d, J = 7 Hz, 3H, -CH-CH3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 254 (M+, 10), 226 (47), 211 (9), 183 (9), 155 (16), 143 (110), 128 (39), 115 (13), 83 (91). Anal, calcd. f o r C 1 7 H 1 8 0 2 : C, 80.28; H, 7.13; found: C, 80.00; H, 7.09. (b) In the S o l i d State When c r y s t a l s (-5.0 mg) of the trimethyl adduct (51) sandwiched between two Pyrex glass plates were photolyzed with a 450 W lamp (A > 290 nm) for 20 h; two compounds resulted. The major compound was iden-t i f i e d as cyclobutanone (51CB f) by c o i n j e c t i o n with the sample i s o l a t e d above. The other compound formed i n less than 10% y i e l d was i d e n t i f i e d as a dimer (51d). MP >290°C. IR (KBr) 3425 (OH), 1672 (C=0) cm"1. Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 508 (M+, 13), 480 (8), 452 (2), 365 (2), 309 (4), 254 (17), 226 (34), 211 (24), 183 (22), 155 (38), 143 (100), 128 (52), 115 (27), 83 (82). In another experiment, an unsuccessful attempt was made using column chromatography to i s o l a t e the dimer (51d) when 0.50 g (1.97 mmol) of the trimethyladduct (51) was photolyzed. 277 23. Photolysis of cis-4a,9a,9,10-Tetrahydro-l,4-anthracenedione (47) (a) In the S o l i d State The c r y s t a l s of tetrahydro-1,4-anthracenedione (47) (0.20 g, 0.94 mmol), sandwiched between Pyrex glass plates and sealed i n polyethylene bags, were i r r a d i a t e d (A >290 nm) for 1 h. The long needle shaped crys-t a l s were found to have shattered into smaller fragments. Y i e l d = 0.20 g, 100%. The dimer formed was i d e n t i f i e d as [2+2] dimer (47d). MP >300°C (decomp.). IR (KBr) 1705 (C=0) cm"1. Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 424 (M+, 5), 278 (2), 212 (100), 195 (69), 184 (31), 167 (57), 155 (28), 141 (27), 129 (78), 128 (74), 115 (29), 82 (24). Anal, calcd. f or C28H24O2: C, 79.23; H, 5.70; found: C, 79.20; H, 5.60. Attempted r e c r y s t a l l i z a t i o n of t h i s compound from many d i f f e r e n t solvents f a i l e d . Only i n DMF at the bp was i t soluble. However, the dimer p r e c i p i t a t e d out as soon as the temperature was allowed to go below the bp. For the same reason no s a t i s f a c t o r y nmr could be obtained. (b) Of a Single C r y s t a l at 0°C A s i n g l e c r y s t a l of the unsubstituted adduct (47) was photolyzed - 278 -with the N 2 Laser f o r 0.5 h at 0°C. The single c r y s t a l s p l i n t e r e d into several pieces as the reaction progressed. Each of the smaller c r y s t a l s was found to be a sing l e c r y s t a l of the dimer as seen through the micro-scope. The structure of the product formed was confirmed by i t s i r spectrum, which was i d e n t i c a l to that of the dimer (47d). 24. Photolysis of 5a,lla-Dimethyl-cis-5a,6,11,lla-tetrahydro-5,12-naphthacenedione (54) (a) In A c e t o n i t r i l e I r r a d i a t i o n (A >290 nm) of naphthacenedione 54 (0.40 g, 1.33 mmol) i n 300 ml CH3CN was c a r r i e d out with a 450 W lamp. A f t e r 4 h, the solvent was removed i n vacuo and the o i l obtained was p u r i f i e d by column chromatography with benzene:methanol (100:1, v/v). The t i c spot corres-ponding to r f value 0.67 was i s o l a t e d and r e c r y s t a l l i z e d from pet. ether (30-60°C) y i e l d i n g c o l o r l e s s needles (142 mg, 35%), i d e n t i f i e d as (3,4)(8,9)-dibenzo- 2-hydroxy-1,6 -dimethyltricyclo[4.4.0.0 2• 1 0]decan-5-one (54P). MP 158-159°C. IR (KBr) 3435 (OH), 1660 (C=0) cm"1. NMR 6 8.01-7.06 (m, 8H, Ar-H), 3.81 (s, 1H, cyclopropyl-H), 3.06 (AB q, J = 18 Hz, 2H, CH 2), 2.31 (s, 1H, exchangeable, OH), 0.89 (s, 3H, CH 3), 0.79 (s, 3H, CH 3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 290 (M+, 38), 262 (53), 247 279 -(32), 229 (21), 215 (13), 157 (50), 142 (39), 134 (100), 130 (50), 115 (31), 105 (52), 77 (34). Anal. calcd. f o r C 2 0 H 1 8 0 2 : C, 82.73; H, 6.25; found: C, 82.54.; H, 6.31. Another compound of r f value 0.80 was also recovered from the c o l -umn and r e c r y s t a l l i z e d from CH3OH producing c o l o r l e s s c r y s t a l s (90 mg, 22%), i d e n t i f i e d as 3-(2,3-dimethyl-l-naphthyl)phthalide (54L). MP 142-143°C. IR (KBr) 1742 (C=0) cm"1. NMR (27°C), S 8.30-6.90 (m, 10H, Ar-H plus methine-H), 2.68 (s, I. 5H, CH 3), 2.55 (s, 1 .5H, CH3), 2.36 (s, 1.5H, CH3), 1.86 (s, 1.5H, CH3). This spectrum indicates a 1:1 mixture of conformers i n slow equilibrium. Fast exchange i s achieved at 90°C as indi c a t e d by the following 1 3 C NMR spectrum (DMS0-d6, 100.6 Hz:): 6 170.1 (C=0), 135.6, 135.5, 134.7, 132.3, 129.9, 129.2, 128.0, 127.2, 126.1, 125.9, 125.7, 125.1, 124.9, 122.5, 122.2 (aromatics-C), 79.4 (methine-C), 26.7 and 15.7 (CH 3). At 27°C, the peaks at 79.4, and 15.7 ppm are broad doublets. Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 288 (M +, 100), 273 (58), 243 (75), 229 (80), 215 (22), 202 (21), 183 (25), 157 (30), 133 (30), 104 (62). Anal, calcd. f o r C 2 0 H 1 6 0 2 : C, 83.31; H, 5.59; found: C, 83.04; H. 5.50. This compound was the sole product when keto-aldehyde (54KA) was photolyzed (see below). The compound with r f value 0.58 was also i s o l a t e d from the column 280 -and r e c r y s t a l l i z e d from pet. ether (30-60°C), gave yellow c r y s t a l s (35 mg, 9%), i d e n t i f i e d as 2-(2,3-dimethyl-l-naphthoyl)benzaldehyde (54KA). MP 138-139°C. IR (KBr) 1682 (HC=0), 1650 (ArC=0) 2750 (H-CO) cm - 1. NMR 6 10.80 (s, 1H, CHO), 8.10-7.15 (m, 9H, Ar-H), 2.47 (s, 3H, CH 3), 2.25 (s, 3H, CH 3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 288 (M +, 66), 287 (2), 273 (100), 259 (16), 143 (25), 215 (20), 155 (14), 104 (18). Anal, calcd. f o r C 2 o H 1 6 0 2 : C, 83.31; H, 5.59; found: C, 83.39; H, 5.54. When t h i s compound was photolyzed (A >290 nm) i n the s o l i d state or i n CH3CN i t y i e l d e d compound 54L i n 100% GC y i e l d . The r a t i o of the three products formed was dependent on the dura-t i o n of i r r a d i a t i o n . For longer periods (more than 12 h), lactone 54L was almost the sole product. (b) In the S o l i d State When the naphthacenedione adduct (54) was photolyzed i n the form of a large s i n g l e c r y s t a l or powder or i n a KBr p e l l e t , no re a c t i o n could be observed e i t h e r by GC or i r for up to 10 h of i r r a d i a t i o n with a 450 W lamp (A > 290 nm) or the N 2 l a s e r . (For d e t a i l s of s o l i d state pho-t o l y s i s see the General Section). 281 -(c) Reaction of Cyclopropanol (54P) with Potassium Hydroxide A s o l u t i o n of cyclopropanol (54P) (5 mg) i n dioxane (0.5 ml) was refluxed f or 12 h with 1 ml of 5% aqueous KOH i n dioxane:water (4:6, v/v). The r e a c t i o n was worked up by adding 5 drops of a c e t i c acid. The organic compounds were extracted with d i e t h y l ether. The eth e r a l layer was washed with a d i l u t e aqueous s o l u t i o n of NaHC03, then with water and d r i e d over anhydrous Na2S0^. A GC analysis of the organic layer showed the presence of lactone (54L) (0.5%) and naphthacenedione adduct (54) (87%), which was confirmed by c o i n j e c t i o n s . (e) Reaction of Lactone (54L) with Sodium Methoxide To a s o l u t i o n of NaOMe (prepared by adding 0.10 g of sodium to 2 ml of methanol) was added lactone (54L) (20 mg) and the r e a c t i o n mixture was s t i r r e d at room temperature for 1 h. A t i c i n pet. ether (30-60°C):EtOAc (4:1, v/v) indicated that the r e a c t i o n was complete. The solvent was removed i n vacuo. the crude s o l i d obtained was dissolved i n water (1 ml) a c i d i f i e d with 0.2 ml cone HC1, extracted with d i e t h y l ether (5 ml) and then d r i e d over anhydrous Na2S04- The solvent was removed i n vacuo to y i e l d a c o l o r l e s s s o l i d (18 mg, 90%) i d e n t i f i e d as the lactone (54L) by mp and i r spectra (see above). This i s because rapid l a c t o n i z a t i o n takes place during workup. In a separate experiment when the r e a c t i o n was quenched by adding water, and no HC1 was used, the r e s u l t remained the same, that i s l a c t o n i z a t i o n took place completely. - 282 25. Photolysis of 2-Methyl-cis-Aa,9,9a,10-tetrahydro-l,4-anthracenedione (48) (a) In A c e t o n i t r i l e I r r a d i a t i o n of toluquinone adduct (48) (0.20 g, 0.90 mmol) was c a r r i e d out as before i n CH3CN (200 ml) with a 450 W lamp (A > 290 nm) for 8 h. The solvent was removed i n vacuo and the o i l obtained was p u r i f i e d by column chromatography with CHCI3. The t i c spot correspond-ing to r f value 0.38 was i s o l a t e d , and r e c r y s t a l l i z e d from pet. ether (30-60°C), y i e l d i n g c o l o r l e s s c r y s t a l s (0.12 g, 60%): i d e n t i f i e d as 3,4-benzo-9-methyltricyclo[4.4.0.0 2 > 9]decan-7,10-dione (48CB). MP 126-127°C. IR (KBr) 1770 (cyclobutanone), 1715 (C=0) cm"1. NMR S 7.29-7.11 (m, 4H, Ar-H), 3.43 (m, 1H, methine-H), 3.28 (m, 2H, 2 x methine-H), 3.01 (d of AB q, J = 17 Hz and 4 Hz, 2H, methylene at C(5)), 2.41 (AB q, J - 18 Hz, 2H, methylene at C(8)), 1.28 (s, 3H, CH 3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 226 (M +, 4), 198 (33), 155 (20), 141 (30), 129 (100), 128 (79), 115 (19). Anal, calcd. f o r C 1 5 H 1 4 0 2 : C, 79.62; H, 6.24; found: C, 79.41; H, 6.30. 283 -(b) In the S o l i d State Single c r y s t a l s (5-10 mg) of the toluquinone adduct (48) were i r r a d i a t e d using the same general method as before for up to 6 h with a 450 W lamp (A > 290 nm) or N 2 l a s e r . No reaction was observed by t i c or i r spectroscopy. When c r y s t a l s were photolyzed with the same l i g h t sources as above i n a KBr matrix, no rea c t i o n was observed by i r spectroscopy for up to 6 h of i r r a d i a t i o n . 26. Photolysis of cis-5a,11a,6,ll-tetrahydro-5,12-naphthacenedione (55) (a) In A c e t o n i t r i l e A s o l u t i o n of the adduct (55) (0.35 g, 1.34 mmol) i n CH3CN (250 ml) was photolyzed (A >290 nm) for 6 h with a 450 W lamp. A GC and a t i c showed the formation of 8 to 9 products without any product being dominant. Attempted separation by column chromatography (pet. ether (30-60°C):Et0Ac (4:1, v/v) of these products f a i l e d . (b) In the S o l i d State I r r a d i a t i o n of c r y s t a l s (5-10 mg) or a KBr p e l l e t containing (1-2%, w/w) of the adduct (55) for up to 10 h with a 450 W lamp (A >290 nm) did not show any reaction, detectable by t i c or i r . 284 -27. Photolysis of 4a, 9 , 9a, 10-Tetrahydro-4 /9-hydroxy-2 ,3 , 4a/3, 9a/3-tetra-methyl-l(4H)anthracenone (56B) (a) In A c e t o n i t r i l e Enone alcohol (56B) (0.20 g, 0.74 mmol) was photolyzed with a 450 W lamp (A >290 nm) f o r 2.5 h i n CH3CN (250 ml). A f t e r solvent evaporation and r e c r y s t a l l i z a t i o n from CH3CN, c o l o r l e s s c r y s t a l s were obtained (0.18 g, 90%), i d e n t i f i e d as i n t e r n a l hemiketal of 3,4-benzo-7-hydroxy-l,6,8-endo,9-tetramethyltricyclo-[4.4.0.0 2> 9]decan-10-one (56BK). MP 164-165°C. IR (KBr) 3272 (OH) cnT 1. NMR 6 7.15-6.95 (m, 4H, Ar-H), 3.48 (s, 1H, CH-0), 3.28 (s, 1H, exchangeable, OH), 2.76 (AB q, J = 17 Hz, 2H, benzylic methylene), 2.64 (s, 1H, b e n z y l i c methine), 1.58 (q, J = 7 Hz, 1H, -CH-CH3), 1.12 (s, 3H, CH 3), 1.01 (s, 3H, CH 3), 0.96 (s, 3H, CH3), 0.79 (d, J = 7 Hz, 3H, -CH-CH3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 270 (M +, 8), 240 (3), 225 (12), 209 (21), 169 (30), 157 (100), 142 (43), 128 (21), 115 (27). Anal. calcd. f or C l gH 2202: C, 79.96; H, 8.20; found: C, 79.98, H, 8.31. The structure of t h i s compound was confirmed by synthesizing i t by an independent route (see page 288). - 285 (b) In A c e t o n i t r i l e at -40°C and at +56°C I r r a d i a t i o n of 0.01 M solutions of the enone 56B (0.2-0.5 ml) was c a r r i e d out with a nitrogen l a s e r at -40°C and at +56°C. The only product formed was hemiketal 56BK. This was i d e n t i f i e d by GC coinjec-t i o n and by c o - t l c with the authentic material i s o l a t e d e a r l i e r (see above). (c) In A c e t o n i t r i l e i n the Presence of a S e n s i t i z e r Solutions of enone (56B) (0.10 M, 1 ml) i n CH3CN and acetophenone (1.00 M, 1 ml) i n CH3CN were mixed and then photolyzed with a N 2 l a s e r for 30 min. The only product formed was i d e n t i f i e d as the hemiketal (56BK) by GC c o i n j e c t i o n . The same r e s u l t was obtained when acetone was used as the solvent and s e n s i t i z e r . (d) In the S o l i d State A KBr p e l l e t containing 1-2 mg of the enone (56B) per 50 mg of KBr was prepared. The p e l l e t was photolyzed f o r 30 min with a N 2 l a s e r . An i r of the product formed was i d e n t i c a l to the i r spectrum of the hemi-k e t a l (56BK) i s o l a t e d above. - 286 28. Photolysis of 4a, 9 , 9a, 10-tetrahydro-4/3-(acetyloxy)-2 , 3 , 4a/3, 9aB-tetramethyl-1(4H)anthracenone (58B) (a) In A c e t o n i t r i l e Acetate (58B) (20 mg, 0.06 mmol) was photolyzed with a 450 W lamp (A >290 nm) for 2 h i n a c e t o n i t r i l e (20 ml). A f t e r solvent was removed i n vacuo. the o i l obtained was p u r i f i e d by column chromatography with pet. ether (30-60°C):Et0Ac (4:1, v/v). The t i c spot corresponding to r f value 0.74 was i s o l a t e d as a c o l o r l e s s o i l (16 mg, 80%), i d e n t i f i e d as 3,4-benzo-7-acetyloxy-l,6,8-endo,9-tetramethyltricyclo[4.4.0.0 2' 9]decan - 1 0 -one (58BS). BP 130°C at 0.1 mm Hg. IR (neat) 1764 (cyclobutanone), 1738 (C=0) cm"1. NMR 8 7.34-6.97 (m, 4H, Ar-H), 4.90 (d, J = 6 Hz, 1H, CH-OAc), 2.82 (AB q, J = 17 Hz, 2H, benzylic methylenes), 2.52 (s, 1H, C(2) H), 2.05 (m, 4H, C0CH 3 and CH-CH3), 1.16 (s, 3H, CH3), 1.14 (s, 3H, CH3), 1.03 (s, 3H, CH 3), 0.73 (d, J = 8 Hz, -CH-CH3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 312 (M+, 3), 270 (42), 225 (13), 209 (32), 169 (70), 157 (100), 142 (35), 128 (15), 113 (18). Anal. calcd. f o r C20H24O3: C, 76.89; H, 7 .74; found: C, 76.84; H, 7.85. When t h i s compound was hydrolyzed i n the presence of a base i t yi e l d e d hemiketal (56BK) (see page 283) . 287 (b) In the S o l i d State A KBr p e l l e t containing 1-2 mg of acetate (58B) per 50 mg of KBr was photolyzed with a N 2 l a s e r f o r 20 min. The i r spectrum of the photoproduct formed i n the KBr p e l l e t was i d e n t i c a l to the i r spectrum of the product (58BS) i s o l a t e d before (see above). Also c r y s t a l s (2-5 mg) of acetate (58B) were i r r a d i a t e d f o r 5 min with a N 2 l a s e r . A GC chromatogram showed that only one product resulted. The i d e n t i t y of the photoproduct was confirmed by c o i n j e c t i o n with the product (58BS) i s o l a t e d before. (d) In A c e t o n i t r i l e at -40° and at +56°C A s o l u t i o n of acetate (58B) (0.01 M) i n CH3CN (0.2-0.5 ml) main-tained at -40°C and another s o l u t i o n at +56°C were i r r a d i a t e d f o r 5-10 min with a N 2 l a s e r . Only one product r e s u l t e d at both temperatures as seen by GC. The i d e n t i t y of the product as 58BS was confirmed by GC c o i n j e c t i o n with the photoproduct i s o l a t e d before (see page 286). (e) In the Presence of a S e n s i t i z e r I r r a d i a t i o n of 0.1 M s o l u t i o n of 58B (0.1 to 0.5 ml acetone) was c a r r i e d out with a nitrogen l a s e r f o r 15 min. The only product formed was 58BS. This was i d e n t i f i e d by GC c o i n j e c t i o n and by c o - t l c with the 288 -authentic material i s o l a t e d e a r l i e r (see page 286). (fi) Hydrolysis of Acetate (58B) A s t i r r e d s o l u t i o n of acetate (58B) (20 mg, 0.06 mmol) i n methanol (2 ml) was treated with 2% aqueous NaOH s o l u t i o n (1 ml) at room tempera-ture f o r 3 h. The reaction mixture was washed with H2O (2 ml x 2), organic compounds were extracted with d i e t h y l ether (3 ml x 2). The organic layer was dr i e d over Na2S04. The solvent was removed i n vacuo to y i e l d c o l o r l e s s c r y s t a l s (16 mg, 92%) i d e n t i f i e d as i n t e r n a l hemi-k e t a l (56BK). MP 164-165°C. The i r spectrum of th i s compound was i d e n t i c a l to the i r spectrum of compound (56BK) i s o l a t e d e a r l i e r (see page 283). 29. Photolysis of 4a, 9 , 9a, 10-Tetrahydro-4a-hydroxy-2 ,3 , 4a/3, 9a/3-tetra-methyl-l(4H)anthracenone (57A) (a) In A c e t o n i t r i l e I r r a d i a t i o n (A >290 nm) of enone (57A) (0.15 g, 0.55 mmol) was c a r r i e d out i n a c e t o n i t r i l e (250 ml) for 3.5 h. A GC analysis showed the formation of two products i n 92% and 8% y i e l d s . A f t e r the usual workup and column chromatography with pet. ether (30-60°C):EtOAc (3:1, 289 -v/v), the t i c spot of r f value 0.60 was i s o l a t e d and r e c r y s t a l l i z e d from methylcyclohexane. The c o l o r l e s s c r y s t a l s (0.10 g, 67%) obtained were i d e n t i f i e d as 3,4-benzo-7-hydroxy-1,6,8-endo,9-tetramethyltricyclo-[4.4.0.0 2' 9] decan-10-one (57AL). MP 99-100°C. IR (KBr) 3496 (OH), 1747 (OO) cm"1. NMR 6 7.24-7.00 (m, 4H, Ar-H), 2.99 (m, 1H, a f t e r exchange becomes d, J = 8 Hz, CH-OH), 2.91 (d, J = 17 Hz, 1H, benzylic methylene), 2.64 (m, 2H, b e n z y l i c methylene and benzylic methine), 1.50 (d of q, 8 l i n e s , J = 17 Hz and 4 Hz, 1H, -CH-CH3), 1.44 (d, J = 8 Hz, 1H, exchangeable, OH), 1.20 (s, 3H, CH 3), 1.18 (s, 3H, CH3), 1.11 (s, 3H, CH3), 0.93 (d, J = 6 Hz, 3H, -CH-CH3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 270 (M+, 9), 242 (9), 227 (6), 209 (22), 194 (5), 169 (29), 157 (100), 142 (48), 128 (30), 115 (33). Anal, calcd. f o r C 1 8 H 2 2 0 2 : C, 79.96; H, 8.20; found: C, 79.76; H, 8.21. The structure of t h i s compound was further supported by i t s oxidation to a known compound (see section d). The minor product formed was i s o l a t e d by carrying out photolysis i n the s o l i d state (see below). (b) In the S o l i d State Crystals of enone alcohol (57A) (55 mg, 0.20 mmol) sandwiched between Pyrex glass plates were i r r a d i a t e d (A >290 nm) for 15 h with a - 290 450 W lamp and then r e c r y s t a l l i z e d twice from methylcyclohexane giving c o l o r l e s s c r y s t a l s (35 mg, 64%) i d e n t i f i e d as 3,4-benzo-10-hydroxy-l,6,8-endo,9-tetramethyltricyclo[4.4.0.0 2- 8]decan-7-one (57AS). MP 155-156°C. IR (KBr) 3449 (OH), 1724 (C=0) cm"1. NMR 8 7.19-6.56 (m, 4H, Ar-H), 3.74 (m, 1H, CH-OH), 2.96 (s, 1H, ben z y l i c methine), 2.75 (AB q, J = 17 Hz, 2H, benzylic methylenes), 1.85 (m, 8 l i n e s , 1H, -CH-CH3), 1.77 (d, J = 4.5 Hz, exchangeable OH), 1.03 (s, 6H, 2 x CH 3), 0.94 (d, J = 7 Hz, 3H, -CH-CH3), 0.86 (s, 3H, CH 3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 270 (M +, 51), 252 (10), 237 (15), 224 (10), 209 (45), 195 (12), 179 (57), 169 (71), 157 (84), 156 (97), 142 (88), 141 (100), 128 (64), 115 (67), 91 (20). Anal, calcd. f o r C 1 8H 220 2: C, 79.96; H, 8.20; found: C, 79.97; H, 8.35. The structure of t h i s compound was also supported by i t s oxidation to a known compound (see section d). When the conversion of the enone (57A) was kept below 5%, only one product (57AS) was observed. However, when the re a c t i o n was allowed to go for more than 5%, a GC peak due to another product appeared. At t h i s stage the c r y s t a l melting was c l e a r . This second product was the same as the s o l u t i o n photoproduct (57AL) as confirmed by GC c o i n j e c t i o n . (c) In A c e t o n i t r i l e i n the Presence of a S e n s i t i z e r As before, i r r a d i a t i o n of enone-alcohol 57A (0.10 M, 0.1 ml) was c a r r i e d out i n the presence of acetophenone (1.00 M, 0.1 ml) with a 450 - 291 -W lamp (A >290 nm) for 30 min. The r a t i o of the two products (57AL and 57AS) remained e s s e n t i a l l y the same (92:8) as t h e i r r a t i o to the unsensitized reaction. The same r e s u l t was obtained when the i r r a d i a -t i o n of 1-2 mg of the enone (57A) was c a r r i e d out i n acetone (0.5 ml). (d) Structure E l u c i d a t i o n of photoproducts (57AL) and (57AS) To a s t i r r e d s o l u t i o n of pyridinium chlorochromate (PCC) (48 mg, 2.21 mmol) i n f r e s h l y d i s t i l l e d anhydrous CH2CI2 (5 ml) maintained under N2 at room temperature, was added alcohol (57AS) (40 mg, 1.5 mmol) and the r e a c t i o n mixture was allowed to s t i r f o r 3.5 h. D i e t h y l ether (10 ml) was added to the brown suspension and the etheral layer was decanted. This process of addition of d i e t h y l ether was repeated twice. The combined ethereal layers were f i l t e r e d through F l o r i s i l i n a s i n -tered glass funnel. The solvent was removed i n vacuo and the yellowish s o l i d obtained was r e c r y s t a l l i z e d from pet. ether (30-60°C) to a f f o r d c o l o r l e s s c r y s t a l s [35 mg, 88%) i d e n t i f i e d as 3,4-benzo-l,6,8-endo,9-tetramethyltricyclo[4.4.0.0 2 > 8]decan-7,10-dione (52CP). MP 133-134°C. IR 1735 (C=0) cm"1. The i r spectrum of t h i s compound was exactly i d e n t i c a l to the i r spectrum of the compound (52CP) i s o l a t e d before (see page 267). In the same way, alcohol (57AL) (10 mg, 0.04 mmol) was oxidized with pyridinium chlorochromate (13 mg, 0.05 mmol). A f t e r workup and recrys-t a l l i z a t i o n as above, the product formed (8 mg, 80%) was i d e n t i f i e d as - 292 -3,4-benzo-1,6,8-endo,9-tetramethyltricyclo[4.4.0.0 2 > 9]decan-2,5-dione (52CB). MP 89.5-90°C. IR 1745 (C=0, cyclobutanone), 1700 (C=0) cm"1. The i r spectrum of th i s compound was found to be exactly i d e n t i c a l to the i r spectrum of the photoproduct i s o l a t e d before (52CB) (see page 266). 30. Photolysis of 4a, 9 , 9a, 10-tetrahydro-4/3-hydroxy-2 ,3 , 4a,4a/3,9a/3-pentamethyl-l(4H)anthracenone (59A) (a) In A c e t o n i t r i l e I r r a d i a t i o n (A >290 nm) of enone (59A) (0.14 g, 0.50 mmol) was c a r r i e d out i n a c e t o n i t r i l e (250 ml) by the standard procedure for 72 h. A GC analysis showed two products formed i n 90% and 10% y i e l d s . Column chromatography with pet. ether (30-60°C):EtOAc (3:1, v/v), ( r f value 0.28) and r e c r y s t a l l i z a t i o n from pet. ether (30-60°C) , afforded color-l e s s c r y s t a l s (80 mg, 57%), i d e n t i f i e d as the i n t e r n a l hemiketal of 3,4-benzo-7-hydroxy-1,6,7,8-endo,9-pentamethyltricyclo[4.4.0.0 2• 9]decan-10-one (59AK). MP 127-128°C. IR (KBr) 3326 (OH) cm"1. NMR S 7.23-6.94 (m, 4H, Ar-H), 2.92 (s, 1H, exchangeable OH), 2.68 (AB q, J = 17 Hz, 2H, benzylic methylene), 2.64 (s, 1H, benzylic methine), 1.50 (q, J = 7 H, 1H, -CH-CH3), 1.20 (s, 3H, CH3), 1.02 (s, - 293 -3H, CH 3), 0.98 (s, 3H, CH 3) , 0.78 (s, 3H, CH 3) , 0.70 (s, 3H, CH 3) . Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 284 (M +, 36), 269 (14), 239 (100), 223 (35), 209 (12), 195 (11), 183 (13), 169 (28), 157 (78), 141 (35), 127 (31), 115 (22). Anal, calcd. f o r C 1 9H 240 2: C, 80.24; H, 8.51 found: C, 80.06; H, 8.61. The minor product formed was also i s o l a t e d (see below). (b) In the S o l i d State Crystals of enone-alcohol (59A) (80 mg) were photolyzed (A >290 nm) with a 450 W lamp for 28 h. A GC analysis showed that 10% of the s t a r t -ing material was s t i l l unreacted. A f t e r column chromatography with pet. ether (30-60°C):EtOAc (4:1, v/v), the t i c spot of r f value 0.59 was i s o l a t e d and r e c r y s t a l l i z e d from methylcyclohexane, y i e l d i n g c o l o r l e s s c r y s t a l s (40 mg, 56%) i d e n t i f i e d as 3,4-benzo-10-hydroxy-l,6,8-endo-9,10-pentamethyltricyclo-[4.4.0.0 2• 8]decan-7-one (59AS). MP 165-167°C. IR (KBr) 3459 (OH), 1724 (C-0) cm - 1. NMR 6 7.20-6.92 (m, 4H, Ar-H), 2.74 (AB q, J = 17 Hz, 2H, methy-lene), 2.65 (s, 1H, benzylic methine), 1.85 (q, J = 7 Hz, 1H, -CH-CH3), I. 44 (s, 3H, CH 3), 1.36 (s, 3H, CH 3), 1.06 (s, 1H, exchangeable -OH), 1.00 (s, 3H, CH 3), 0.94 (s, 3H, CH 3), 0.90 (d, J = 7 Hz, 3H, CH-CH3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 284 (M+, 100), 269 (13), 241 (44), 228 (37), 213 (85), 195 (27), 185'(18), 169 (27), 158 (60), 142 (45), 127 (40), 115 (27), 83 (36). 294 Anal, calcd. f o r C 1 9H 240 2: C, 80.24; H, 8.51; found: C, 80.13; H, 8.45. (c) In Acetone I r r a d i a t i o n (A >290 nm ) of 1-2 mg of enone (59A) was c a r r i e d out i n acetone (0.2-0.5 ml) f o r 30 min, y i e l d i n g two products (59AK:59AS) i n the r a t i o of 92:8. (d) Deuterium Exchange Study of 59AS To a s o l u t i o n of alcohol 59AS (10 mg, 0.035 mmol) i n CH3OD (1 ml) was added NaOMe (1 ml) (prepared by adding 0.10 g of sodium i n 1 ml CH3OD) and the s o l u t i o n was s t i r r e d at room temperature for 20 h. The rea c t i o n mixture was treated with one drop of cone. HC1, and the organic compounds were extracted with d i e t h y l ether (3 ml x 2), washed with H 20 (2 ml), and d r i e d over Na^O^. The solvent was removed i n vacuo to a f f o r d c o l o r l e s s s o l i d (9 mg, 90%). A NMR spectrum of t h i s material showed that deuterium incorporation d i d not take place at a l l . - 295 31. Photolysis of 4,4,8a-Trimethyl-8a/3-carbomethoxy-cis-4a,5,8,8a-tetrahydro-l(4H)naphthalenone (119)* (a) In Benzene I r r a d i a t i o n (A >290 nm) of enone (119) (10 mg, 0.04 mmol) i n benzene (10 ml) was c a r r i e d out for 40 min. The solvent was removed i n vacuo and the o i l was c r y s t a l l i z e d from pet. ether (30-60°C), y i e l d i n g a co l o r l e s s s o l i d (8 mg, 80%) i d e n t i f i e d as 5,5,10-trimethyl-l-carbo-methoxy te t r a c y c l o [4 . 4.0.0. 3 > 90. 4' 8]decan-2 - one (119d). MP 52-53°C. IR (CHC13) 1745 (C-0), 1720 (C=0, ester) cm - 1. NMR 6 3.80 (s, 3H, -COOCH3), 3.06 (m, 1H), 2.75-2.12 (m, 5H), 1.82 (m, 1H), 1.65 (m, 1H), 1.30 (s, 3H, CH 3), 0.87 (d, J = 7 Hz, 3H, CH3), 0.86 (s, 3H, CH 3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 248 (M +, 39), 220 (8), 217 (15), 205 (12), 188 (14), 162 (13), 151 (27), 122 (100), 107 (28), 91 (28), 82 (34). HRMS calcd. f or C 1 5H 2o0 3: 248.1412; found: 248.1411. (b) In the S o l i d State I r r a d i a t i o n (A 325 nm) of the c r y s t a l s of enone 119 (2-5 mg) was c a r r i e d out with a He-Cd la s e r for up to 20 h at -16 to -18°C (to pre-vent melting). No rea c t i o n could be observed by t i c (CHCI3), GC or i r spectroscopy. * Supplied by Professor H.-J. L i u of the Un i v e r s i t y of Alber t a whom I thank. 296 32. Photolysis of 4,4,7-Trimethyl-8a/J-carbomethoxy-8-ac Atyloxymethyl-cis-4a,5,8,8a-tetrahydro-l(4H)-naphthalenone (120) (a) In Benzene I r r a d i a t i o n (A >290 nm) of enone (120) (20 mg, 0.06 mmol) i n benzene (10 ml) was c a r r i e d out for 1 h. Af t e r solvent removal and r e c r y s t a l l i z a t i o n from methylcyclohexane, c o l o r l e s s c r y s t a l s were obtained (16 mg, 80%) i d e n t i f i e d as 5,5,9-trimethyl-l-carbomethoxy-10-acetyloxymethyltetracyclo[4.4.0.0 2 , 90 4' 8]decan-2-one (120d). MP 103-104°C. IR (CHC1 3) 1740 (C=0) cm - 1. NMR (80 MHz) 6 3.98 (m, 2H, -CH2-0Ac) , 3.80 (s, 3H, -COOCH3) , 2.67(m, 2H), 2.37 (m, 3H), 2.00 (s, 3H, O-COCH3), 1.80 (m, 2H), 1.28 (s, 3H, CH 3), 1.22 (s, 3H, CH3), 0.88 (s, 3H, CH3). Mass Spectrum, m/e ( r e l a t i v e i n t e n s i t y ) 32c (M+, 16), 278 (100), 260 (11), 246 (25), 219 (15), 202 (22), 173 (20), 149 (20), 96 (40). HRMS calcd. f o r C 1 8 H 2 4 0 5 : 320.1624. found: 320.1623. Anal, calcd. f o r C 1 8 H 2 4 0 5 : C, 67.48; H, 7.55; found: C, 67.61; H, 7.56. (b) In the S o l i d State Crystals (2-5 mg) of enone (120) were i r r a d i a t e d f o r up to 11 h at 0°C with a He-Cd la s e r (A 325 nm). No reac t i o n was observed by GC, /fair or NMR spectroscopy. 297 -33. Quantum Yiel d s and Quenching Studies Apparatus A Merry-go-round apparatus was used to determine the quantum y i e l d s . 2 5 1 The 313 nm l i n e was i s o l a t e d by c i r c u l a t i n g a 0.002 M K^CrO^ s o l u t i o n containing 5% K2CO3 (W/W) through the quartz immersion well and by p l a c i n g 7.54 Corning f i l t e r s i n the f i l t e r h o l d e r . 2 5 1 The tempera-ture of the setup was maintained at 20 ± 2°C by c i r c u l a t i n g water through the system. P u r i f i c a t i o n of Solvents and Reagents Benzene was p u r i f i e d (thiophene free) and d r i e d by well known O C T methods. J i A c e t o n i t r i l e was d i s t i l l e d over CaH2. Valerophenone was d i s t i l l e d and stored i n the dark i n the r e f r i g e r a t o r and duroquinone adduct (52) was r e c r y s t a l l i z e d from pet. ether (30-60°C) and was stored i n the dark. Alkanes, used as i n t e r n a l standards, were used as received from A l d r i c h Chemical Co. without further p u r i f i c a t i o n . Actinometrv Valerophenone actinometry, which had been c a r r i e d out before i n our l a b o r a t o r y , 1 7 7 was used. As before, tetradecane was used as the i n t e r -298 -nal standard. The quantum y i e l d s were determined r e l a t i v e to acetophe-none formation from 0.10 M valerophenone (known to be 0.88 i n moist CH 3CN). 1 8 5 Internal Standards and GC Detector Responses Internal standards were selected i n such a way that t h e i r GC peak(s) d i d not overlap with product(s) peak(s) and yet had retention times close to the product(s) under i n v e s t i g a t i o n . Nonadecane was used as the i n t e r n a l standard for adduct (52) as well as f o r enone 57B. As reported above, tetradecane was the i n t e r n a l standard f o r valerophenone. In order to measure detector responses, an accurately weighed sample of the photoproduct (e.g. 52CB) (20-25 mg) and nonadecane (20-25 mg) was dissolv e d i n 10 ml of benzene. A 1-2 / i l sample of t h i s mixture was i n j e c t e d i n to the GC and the r a t i o of the peaks obtained was compared with the o r i g i n a l r a t i o . Preparation of Solutions A 1% (1.0 mg/ml) s o l u t i o n of nonadecane and'a 1% (1.0 mg/ml) solu-t i o n of tetradecane i n benzene were prepared i n 50 ml volumetric f l a s k s . Separate solutions of valerophenone (0.10 M), adduct (52) (0.10 M) and enone-alcohol (56B) (0.10 M) were prepared i n 25 ml volumetric f l a s k s i n moist CH3CN (CH3CN:H20 (50:1, v / v ) ) . A 3.0 ml portion of each 299 -of these solutions were separately transferred into s p e c i a l photolysis tubes (100 x 13 mm Pyrex t e s t tubes) with a pipette. These samples were degassed by a freeze, pump, and thaw cycle, at le a s t three times before use. I r r a d i a t i o n of Samples A t y p i c a l procedure i s given here f or the adduct (52). Several tubes of degassed samples (see preparation of solutions) containing 3.0 ml of 0.1 M s o l u t i o n of adduct (52) were photolyzed with a Hanovia 450 W medium pressure Hg lamp housed i n a quartz jacket. As mentioned before, i r r a d i a t i o n was performed i n a Merry-go-round apparatus at A > 313 nm. A p a r a l l e l i r r a d i a t i o n of valerophenone actinometer (0.10 M) containing the same amount of al i q u o t placed i n p a r t i a l l y covered but c a l i b r a t e d , opening i n the Merry-go-round apparatus, was also performed. The actinometer samples were replaced with new samples a f t e r 8 h and i r r a d i a t i o n was continued f o r another 8 h. At the end of t h i s period, the degassed samples were opened and 1.0 ml of 1% benzene s o l u t i o n of a su i t a b l e i n t e r n a l standard was added. Each sample was analyzed by GC at l e a s t four times and from the area/mg of the i n t e r n a l standard, the area/mg of the photoproducts was c a l c u l a t e d which i n turn was used to ca l c u l a t e the quantum y i e l d s . The quantum y i e l d s reported (see Discussion section) are an average of two independent experiments. The error i n t h i s measurement was estimated to be ± 10%. 300 Quenching Study Preparation of solutions. 1. A 1.00 M s o l u t i o n of adduct (52) was made i n 10.00 ml of CH3CN:H20 (50:1, v/v) (stock s o l u t i o n 1). 2. A 1.00 M s o l u t i o n of 2,5-dimethyl-2,4-hexadiene (diene) was pre-pared i n 10.0 ml of CH3CN:H20 (50:1, v/v) (stock s o l u t i o n 2). 3. The solutions of other concentrations were prepared by d i l u t i n g the stock solutions as shown below i n Table 15. Table 15: Volume of Stock Solution (1) (ml) Volume of Stock Solution (2) (ml) Volume of 0.10 M diene (ml) F Volume (ml) l n a Concentra-t i o n of diene (M) Concentra-t i o n of Adduct (M) 1 2 3 4 5 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 2.0 6.0 1.0 10.0 10.0 10.0 10.0 10.0 0.01 0.02 0.06 0.10 0.11 0.10 0.10 0.10 0.10 0.10 301 -A 3.0 ml po r t i o n of each of the 5 samples of d i f f e r e n t quencher concentrations shown i n Table 15 were transferred into the Pyrex tubes described e a r l i e r . A l l 5 samples, along with a sample without quencher., were degassed as before and photolyzed i n the Merry-go-round apparatus i n the same way as explained e a r l i e r . From the r e s u l t s obtained, the value of $ 0 (quantum y i e l d without quencher) and $ (the quantum y i e l d i n the presence of quencher) were calculated. A p l o t of $ 0/$ against the quencher concentration y i e l d e d a s t r a i g h t l i n e . From the slope of the s t r a i g h t l i n e , the l i f e t i m e of the t r i p l e t excited state and the rate constant were calc u l a t e d . - 302 -REFERENCES 303 REFERENCES 1. Cookson, R.C., Crundwell, E., H i l l , R.R., Hudec, J . J . Chem. S o c . 1964, 3062. 2. Cookson, R.C., H i l l , R.R. Hudec, J . J . Chem. Soc. 1964, 3043. 3. Barborak, J.C., Watts, L., P e t t i t , R. J . Am. Chem. Soc. 1966, 88, 1328. 4. F i l i p s e c u , N., Menter, J.M. J . Chem. Soc. B 1969, 616. 5. Warrener, R.N., McCay, I.W., Paddon-Row, M.N. Aust. J . Chem. 1977, 30, 2189. 6. Kushner, A.S. Tet. Let t . 1971, 3275. 7. McKennis, J.S., Brener, L., Ward, J.S., P e t t i t , R. J . Am. Chem.  Soc. 1971, 93, 4957. 8. (a) Marchand, A.P., Chou, T.-C. J . Chem. Soc. PI 1973, 1948. (b) Dekker, J . , Dekker, J . J . , Fourier, L., Martins, J.F.C. South  A f r i c . J . Chem. 1976, 29, 114. 9. Weisz, A., Kaftory, M., Vidavsky, I., Mandelbaum, A. J . Chem. Soc.  Chem. Commun. 1984, 18. 10. (a) Mehta, G., Srikrishna, A., Veera Reddy, A., Nair, M.S. Tetra-hedron 1981, 37, 4543. (b) Mehta, G., Singh, V., Rao, K. Tet. Le t t . . 1980, 21, 1369. 11. Scheffer, J.R., Bhandari, K.S., Gaylor, R.E., Wastradouski, R.A. J. Am. Chem. Soc. 1975, 97, 2178. 12. Scheffer, J.R., Jennings, B.M., Louwerens, J.P. J . Am. Chem. Soc. 1976, 98, 7040. 13. Wastradowski, R.A., Ph.D. Thesis, U n i v e r s i t y of B r i t i s h Columbia, 1972. 14. Gaylor, R.E., Ph.D. Thesis, U n i v e r s i t y of B r i t i s h Columbia, 1973. 15. Jennings, B.M., Ph.D. Thesis, U n i v e r s i t y of B r i t i s h Columbia, 1975. 16. Dzakpasu, A., Ph.D. Thesis, U n i v e r s i t y of B r i t i s h Columbia, 1977. 17. Scheffer, J.R., Dzakpasu, A. J. Am. Chem. Soc. 1978, 100, 2163. - 304 -18. Askari, S.H., Lee, S., Perkins, R.R., Scheffer, J.R. Can. J. Chem. 1985, 63, 3526. 19. F i n k e l s t e i n , H., Dis s e r t a t i o n , Strasburg, 1910, c i t e d i n reference 20. 20. McCullough, J . J . Acc. Chem. Res. 1980, 13, 270. 21. Cava, M.P., Napier, D.R. J . Am. Chem. Soc. 1957, 79, 1701. 22. Cava, M.P., Deana, A.A., Muth, K. J . Am. Chem. Soc. 1959, 81, 6458. 23. Cava, M.P., Deana, A.A. J . Am. Chem. Soc. 1959, 81, 4266. 24. Jensen, F.R., Coleman, W.E., B e r l i n , A.J. Tet. Let t . 1962, 15. 25. Jensen, F.R., Coleman, W.E. J . Am. Chem. Soc. 1958, 80, 6149. 26. Errede, L.A. J . Am. Chem. Soc. 1961, 88, 949. 27. Funk, R.L., Vollhardt, K.P.C. Chem. Soc. Rev. 1980, 41. 28. Oppolzer, W. Synthesis 1978, 793. 29. Sammes, P.G. Tetrahedron 1976, 32, 405. 30. Kametani, T., Fukumoto, K. Med. Res. Rev. 1981, 1, 23. 31. Pl a t z , M.S. "The Chemistry of B i r a d i c a l s " , Pergamon Press 1981, Ch. 4. 32. Flynn, C.R., Michl, J . J . Am. Chem. Soc. 1974, 96, 3280. 33. Toda, F., Tanaka, K., Matsui, M., Tet. Lett. 1982, 23, 217. 34. Kametani, T., Fukumoto, K. Heterocvcles 1975, 3, 29. 35. Klundt, I.L. Chem. Rev. 1970, 70, 471. 36. Kametani, T., Takeshita, M., Nemoto, H., Fukumoto, K. Chem. Pharm.  B u l l . (Tokyo') 1978, 26, 556. 37. Kametani, T., Chihiro, M., Takeshita, M., Takahashi, K., Fukumoto, K., Takano, S. Chem. Pharm. B u l l . (Tokyo) 1978, 26, 3820. 38. Kametani, T. , Takahashi, T. , Kajiwara, M. , H i r a i , Y. Ohtsuka, C , Satoh, F., Fukumoto, K. Chem. Pharm. B u l l . (Tokyo) 1974, 22, 2159. 39. Sammes, P.G., Arnold, B.J. J. Chem. Soc. Chem. Commun. 1972, 30. - 305 -40. Pfau, M., Rowe, J.E., Heindel, N.D. Tetrahedron 1978, 34, 3469. 41. Pfau, M., Combrisson, S., Rowe, J.E., Heindel, N.D. Tetrahedron 1978, 34, 3459. 42. Yang, N.C., Rivas, C. J . Am. Chem. Soc. 1965, 87, 5417. 43. Pratt, A.C. J . Chem. Soc. Chem. Commun. 1974, 183. 44. McOmie, J.F.W., Perry, D.H. Synthesis 1973, 416. 45. Kerdesky, F.A.J., Ardecky, R.J., Lakshmikantham, M.V., Cava, M.P. J. Am. Chem. Soc. 1981, 103, 1992. 46. Kametani, T., Ichikawa, Y., Suzuki, T., Fukumoto, K. J . Chem. Soc. PI 1975, 2101. 47. Wiseman, J.R., French, I.N. Tet. Lett. 1978, 3765. 48. Farina, F., Primo, J . , Torres, T. Chem. Lett. (Japan) 1980, 77. 49. Han, B.H., Boudjouk, P. J . Org. Chem. 1982, 47, 751. 50. Rubottom, G.M., Wey, J.E. Synth. Commun. 1984, 14, 507. 51. Ito, Y., Nakatsuka, M., Saegusa, T. J . Am. Chem. Soc. 1982, 104, 7609 and also 1980, 102, 863. 52. Ito, Y., Amino, Y., Nakatsuka, M., Saegusa, T. J . Am. Chem. Soc. 1983, 105, 1586. 53. Moss, R.J., Rickborn, B. J . Org. Chem. 1984, 49, 3694. 54. Quinkert, G. Pure Appl. Chem. 1964, 9, 607. 55. Quinkert, G., Opitz, K., Wiersdorff, W.W., Weiblich, J . Tet. Lett 1963, 1863. 56. Spangler, R.J., Beckmann, B.G., Kim, J.H. J . Org. Chem. 1977, 42, 2989. 57. Spangler, R.J., Beckmann, B.G. Tet. Lett. 1976, 2517. 58. Charlton, J.L., Durst, T. Tet. L e t t . 1984, 25, 2663. 59. Charlton, J.L., Alauddin, M.M., Penner, G.H. Can. J . Chem. 1986, 64, 794. 60. Charlton, J.L. Can. J . Chem. 1986, 64, 720. 61. Charlton, J.L. Tet. Lett. 1985, 26, 3413. 306 62. Jung, F., Molin, M., van den Elzen, R., Durst, T. J . Am. Chem.  Soc. 1974, 96, 935. 63. Charlton, J.L., Durst, T. Tet. L e t t . 1984, 25, 5287. 64. Durst, T., Tetreault-Ryan, L. Tet. Let t . 1978, 2353. 65. Durst, T., Charlton, J.L., Mount, D.B. Can. J. Chem. 1986, 64, 246. 66. R.O. Kan, "Organic Photochemistry" McGraw H i l l Book Co., New York, N.Y., 1966. 67. Eaton, P.E., Cole, T.W. J . Chem. Soc. Chem. Commun.. 1970, 1493. 68. van Bayer, A. Chem. Ber. 1880, 13, 2254. 69. Cohen, M.D., Green, B.S. Chem. i n B r i t a i n . 1973, 490. 70. Stout, G.H., Jensen, L.H., "X-ray Structure Determination". MacMillan Co., New York, N.Y. 1960. 71. Beurger, M.J. "Crystal Structure Analysis". Wiley 6c Sons, New York, N.Y. 1960. 72. Scheffer, J.R. Acc. Chem. Res.. 1980, 13, 283. 73. Scheffer, J.R., Tro t t e r , J . i n Chemistry of Quinonoid Compounds Supplementary v o l . 2, S. Patai and Z. Rappoport, Eds., Wiley Inter-science, i n Press. 74. Scheffer, J.R. i n Organic S o l i d State, G.R. Desiraju, Ed., E l s e v i e r , i n press. 75. Scheffer, J.R., Garcia-Garibay, M., Nalamasu, 0. i n "Organic Photo-chemistry", A. Padwa, Ed. Marcel Dekker, New York, Vol. 8, 1987. 76. T r o t t e r , J . Acta Cryst. 1983, B39, 373. 77. Schmidt, G.M.J. " S o l i d State Photochemistry", D. Ginsburg, Ed. Verlag Chemie, New York, 1976. 78. Hasegawa, M. Chem. Rev. 1983, 83, 507. 79. Paul, I., Curtin, D.Y. Acc. Chem. Res.. 1973, 6, 217. 80. Thomas, J.M., Morsi, S.E., Desvergne, J.P. Adv. Phys. Org. Chem. 1977, 15, 63. 307 -81. (a) Addadi, L., A r i e l , S., Lahav, M., Leiserowitz, L., Papovitz-Biro, R. , Tang, C P . "Chemical Physics of S o l i d and Their Surfaces", Roberts, M.W. and Thomas J.M. Eds. The Royal Society of Chemistry, London, S p e c i a l i s t P e r i o d i c a l Reports, Vol. 8, Ch. 7. 81. (b) Gavezotti, A., Simonetta, M., Chem. Rev. 1982, 82, 1. 82. Sarma, J.A.R.P., Desiraju, G.R. J. Chem. Soc. Perkin II 1984, 93, 407. 83. Desiraju, G.R. Proc. Indian. Acad. S c i . (Chem. Sci.) 1984, 93, 407. 84. Green, B.S., Lahav, M., Rabinovich, D. Acc. Chem. Res. 1979, 12, 191. 85. Schmidt, G.M.J. Pure Appl. Chem. 1971, 27, 647. 86. Cohen, M.D. Ang. Chem. Int. Ed. Eng. 1975, 14, 386. 87. McBride, J.M. Acc. Chem. Res. 1980, 13, 283. 88. Ramamurthy, V., Venkatesan, K. Chem. Rev. i n press. 89. Kohlshutter, H.W. Z. Anorg. A l l g . Chem. 1918, 105, 121. 90. Cohen, M.D., Schmidt, G.M.J. J . Chem. Soc. 1964, 1996. 91. Schmidt, G.M.J., "Reactivity of Photoexcitated Organic Molecule", Interscience, New York, N.Y., 1967, p. 227. 92. Lahav, M., Schmidt, G.M.J. J . Chem. Soc. B 1967, 239. 93. Nakanishi, H., Jones, W., Thomas, J.M. Chem. Phys. Lett. 1980, 71, 44. 94. Nakanishi, H., Jones, W., Thomas, J.M., Hursthouse, M.B., Mote-v a l l i , M. J . Chem. Soc. Chem. Commun. 1980, 611. 95. Jones, W., Nakanishi, H., Theocharis, C.R., Thomas, J.M. J. Chem.  Soc. Chem. commun. 1980, 610. 96. Thomas, J.M. Nature (London) 1981, 289, 633. 97. Nakanishi, H., Jones, W., Thomas, J.M., Hursthouse, M.B., Mote-v a l l i , M. J . Phvs. Chem. 1981, 85, 3636. 98. Jones, W., Ramadas, S., Theocharis, C.R., Thomas, J.M., Thomas, N.W. J. Phvs. Chem. 1981, 85, 2594. 308 99. Lahav, M., Schmidt, G.M.J., J . Chem. Soc. B. 1967, 312. 100. Green, B.S., Lahav, M., Schmidt, G.M.J. J . Chem. Soc. B 1971, 1552. 101. Sadeh, T., Schmidt, G.M.J. J . Am. Chem. Soc. 1962, 84, 3970. 102. Gnanaguru, K., Ramasubbu, N., Venkatesan, K., Ramamurthy, V. J.  Org. Chem. 1985, 60, 2337. 103. Ramasubbu, N., Gnanaguru, K., Venkatesan, K., Ramamurthy, V. Can.  J. Chem. 1982, 60, 2159. 104. Bhadbhade, M.M., Murthy, G.S., Venkatesan, K., Ramamurthy, V. Chem. Phys. L e t t . 1984, 109, 259. 105. Gnanaguru, K., Murthy, G.S., Venkatesan, K., Ramamurthy, V. Chem.  Phvs. L e t t . 1984, 109, 255. 106. Gnanaguru, K., Ramasubbu, N., Venkatesan, K., Ramamurthy, V. J .  Photochem. 1984, 27, 355. 107. Matsura, T., Sata, Y., Ogura, K., Tet. Lett . . 1968 4627. 108. Quinkert, G., Tabata, T., Hickman, E.A.J., Dobrat, W. Angew. Chem.  Int. Ed. Engl. 1971, 10, 199. 109. Quinkert, G., Opitz, K., Wiersdorff, W.W., Weinlich, J . Tet. Let t . 1963, 1863. 110. Baretz, B.H., Turro, N.J. J . Am. Chem. Soc. 1983, 105, 1309. 111. Evans, S., Omkaram, N., Scheffer, J.R., Tro t t e r , J . Tet. Lett. 1985, 26, 5903. 112. Evans, S.V., Omkaram, N., Scheffer, J.R., Tr o t t e r , J . Tet. Lett. 1986, 27, 1419. 113. Scheffer, J.R., Tro t t e r , J . , Omkaram, N., Evans, S.V., A r i e l , S. Mol. Crvst. L i q . Crvst. 1986, 34, 169. 114. A r i e l , S., Ramamurthy, V., Scheffer, J.R., Tro t t e r , J . J . Am.  Chem. Soc. 1983, 105, 6959. 115. Appel, W.K., Jiang, Z.Q., Scheffer, J.R., Walsh, L. J . Am. Chem.  Soc. 1983, 105, 5354. 116. Scheffer, J.R., Trotter, J . , Appel, W.K., Greenhough, T.J., Jiang, Z.Q., Secco, A.S. Mol. Crvst. L i q . Crvst. 1983, 93, 1. - 309 -117. Greenhough, T.J., Scheffer, J.R., Secco, A.S., Tro t t e r , J . , Walsh, L. I s r . J . Chem. 1985, 25, 297. 118. D. H u l l , "Introduction to Disl o c a t i o n s " , Pergaman Press, New York, N.Y. 1965. 119. Craig, D.P., Sarti-Fantoni, P. J . Chem. Soc. Chem. Commun. 1966, 762. 120. Thomas, J.M., Williams, J.O. J. Chem. Soc. Chem. Commun. 1967, 432. 121. Cohen, M.D., Ludmer, Z., Thomas, J.M., Williams, J.O. J . Chem.  Soc. Chem. Commun. 1969, 1172. 122. Thomas, J.M. Is r . J. Chem. 1972, 10, 573. 123. Cohen, M.D., Ludmer, Z., Thomas, J.M., Williams, J.O. Proc. R.  Soc. London. Ser. A 1971, 324, 459. 124. Desvergne J.P., Thomas, J.M., Williams, J.O., Bouas-Laurent, H. J.  Chem. Soc. P2 1974, 362. 125. Desvergne, J.P., Bouas-Laurent, Lapouyade, R., Gau l t i e r , J . , Hamo, C , Duprey, F. Mol. Crvst. L i q . Cryst. 1972, 19, 63. 126. Parkinson, G.M., Govinge, M.J., Ramdas, S., Williams, J.O., Thomas, J.M. J . Chem. Soc. Chem. Commun. 1978, 134. 127. Thomas, J.M., Williams, J.O., Desvergne, J.P., Gavnini, G., Bouas-Laurent, H. J . Chem. Soc. P2 1975, 84. 128. Bergman, J . , Osaki, K., Schmidt, G.M.J., Sonntag, F.I. J . Chem.  Soc. 1964, 2021. 129. Gavezotti, A. J . Am. Chem. Soc. 1983, 105, 5220. 130. D i e l s , 0., Alder, K. Chem. Ber. 1929, 62, 2362. 131. P h i l l i p s , S.E.V., Trotter, J . Acta Crvst. 1977, B33, 984. 132. P h i l l i p s , S.E.V., Trotter, J . Acta Crvst. 1977, B33, 996. 133. P h i l l i p s , S.E.V., Trotter, J . Acta Crvst. 1976, B32, 3098. 134. P h i l l i p s , S.E.V., Trotter, J . Acta Crvst. 1976, B32, 3088. 135. Greenhough, T.J., Trotter, J . Acta Cryst. 1980, B36, 2840. 136. Wagner, P.J. Acc. Chem. Res. 1983, 16, 461. 310 -137. Wagner, P.J. Acc. Chem. Res. 1971, 4, 168. 138. Lewis, F.D., Johnson, R.W., Johnson, D.E. J . Am. Chem. Soc. 1974, 96, 6090. 139. Seeman, J . I . Chem. Rev. 1983, 83, 82. 140. Fleming, I. "Frontier O r b i t a l s and Organic Chemical Reactions", John Wiley & Sons, 1976. 141. Mandelbaum, A., Cais, M. J . Org. Chem. 1962, 27, 2245. 142. A n s e l l , M.F., Nash, B.W., Wilson, D.A. J . Chem. Soc. 1963, 3027. 143. Brasen, W.R. , Hauser, CR. Org. Synth 1954, 34, 61. 144. Brasen, W.R. , Hauser, CR. Org. Svnth. 1954, 34, 62. 145. Smith, L.I. Org. Synth. C o l l . V o l. 4, 254. 146. S t i l l , W.C, Mitra, A. J . Org. Chem. 1978, 43, 2923. 147. Fleming, I., Williams, D.H. "Spectroscopic Methods i n Organic Chemistry" McGraw-Hill Pub. London, 1967. 148. S i l v e r s t e i n , R.M., Bassler, G.C., M o r r i l , T.C "Spectroscopic I d e n t i f i c a t i o n of Organic Compounds", Wiley and Sons, 1974. 149. A r i e l , S., Scheffer, J.R., Trotter, J . , Wong, Y.-F. Tet. Lett. 1983, 24, 4555. 149a.Kessler, H., Angew. Chem. Int. Ed. Eng.. 1970, 9, 219. 150. Scheffer, J.R., Walsh, L. unpublished r e s u l t s . 151. Martin, J.G., H i l l , R.K. Chem. Rev. 1961, 537. 152. Wireko, F., Tro t t e r , J . unpublished r e s u l t s . 152a.Ariel, S., Tro t t e r , J . unpublished r e s u l t s . 153. Kruber, 0. Berchte 1929, 3044. 154. Sadtler L i b r a r y of NMR spectra, Ed. Simon, W.W. Sadtler Res. Labs. P h i l . 1967. 155. (a) Wertyporoch, V.E., F i r l a T. Ann 1933, 500, 293. (b) Haff, H., Wick, A.K., Helv. Chim. Acta 1960, 43, 1473. (c) Suzuki, H., Ohnishi, K. Nippon Kagoka Ka i s h i 1981, 2, 245. - 311 -(d) Smith, L.I., Harris, S.A. J . Am. Chem. Soc. 1935, 1289. 156. Kuwajima, I., Kurofurshi, T., Nakamura, E. Synthesis 1976, 602. 157. Gupta, D.N., Hodge, P., Khan, N. J . Chem. Soc. PI 1981, 689. 158.Scharf, H.D. Fluschlaner, J . , Leismann, H., Ressler, I., Schleker, W., Weitz, R. Angew. Chem. Int. Ed. Eng. 1979, 18, 652. 159. M a r i e l l a , R.P., Brown, K.H. Can. J . Chem. 1971, 49, 3348. 160. L i o t t a , C.L., Harris, H.P. J . Am. Chem. Soc. 1974, 96, 2250. 161. Scheffer, J.R., Wong, Y.-F. unpublished r e s u l t s . 162. Fieser, L.F., Arado, M.I. J . Am. Chem. Soc. 1956, 78, 778. 163. Badwin, J.E. J . Chem. Soc. Chem. Commun. 1976, 738. 164. A l d r i c h L i b r a r y of NMR spectra by Pouchert, C.J., Campbell, J.R., A l d r i c h Chem. Co., Milwaukee, Wisconsin, 1974. 165. Pasto, D.J., Johnson, CR. "Organic Structure Determination" Pren-t i c e H a l l Inc. 1969. 166. Streitwieser, A., Heathcock, C.H. "Introduction to Organic Chemis-t r y " , MacMillan Publishing Co. New York, Ch. 10. 167. Jiang, Z.Q., Scheffer, J.R., Secco, A.S., Tro t t e r , J . , Wong, Y.-F. J. Chem. Soc. Chem. Commun. 1983, 773. 168. Dunitz, J.D., "X-ray Analysis of the Structure of Organic Mole-cules", C o r n e l l U n i v e r s i t y Press, Ithaca, New York, 1979, Ch. 7. 169. A r i e l , S., Evans, S., Hwang, C., Jay, J . , Scheffer, J.R., Trotter, J . , Wong, Y.-F. Tet. Let t . 1985, 26, 965. 170. A r i e l , S., Tro t t e r , J . unpublished r e s u l t s . 171. T r o t t e r , J . , P h i l l i p s , S.E.V. Acta Crvst. 1976, B32, 3095. 172. Rickborn, B., Lwo, S.-Y. J . Org. Chem. 1965, 30, 2212. 173. Werz, W. , Nair, CM. J. Am. Chem. Soc. 1967, 89, 5474. 174. Wolf, S., Schreiber, W.L., Smith, A.B., Agosta, W.C. J . Am. Chem.  Soc. 1973, 95, 1961. 175. Marchesini, A., Pagnoni, V.M., Pinett, A. Tet. Lett. 1973, 4299. 176. Baltrop, J.A., G i l e s , D. J . Chem. Soc. (C) 1969, 105. 312 -177. N. Omkaram, Ph.D. Thesis, U n i v e r s i t y of B r i t i s h Columbua, 1986. 178. Dauben, W.G., Kellog, M.S., Seeman, J . I . , Vietmeyer, N.D. Wend-schub, P.A. Pure Appl. Chem. 1973, 33, 197. 179. Dauben, W.G., Olsen, E.G. J . Org. Chem. 1980, 45, 3377. 180. Dauben, W.G., Kellog, M.S. J . Am. Chem. Soc. 1980, 102, 4456. 181. Dauben W.G., Mclnnis, E.L., Michno, D.M. i n "Rearrangement i n Ground and Excited States", P. de Mayo Ed., Academic Press, New York, 1980, v o l . 3, Ch. 15. 182. Askari, S.H., Scheffer, J.R., Trotter, J . , Wireko, F. J. Am. Chem.  Soc. (communicated). 183. Greenhough, T.J., Trotter, J . Acta Cryst. 1979, B35, 3084. 184. Werstiuk, N.H., T a i l l e f e r , R. Can. J. Chem. 1970, 48, 3966. 185. Wagner, P.J. Acc. Chem. Res. 1971, 4, 168. 186. See r e f . 178-181 f or temperature e f f e c t i n photochemical reactions. 187. Lamola, A.A. i n "Energy Transfer and Organic Photochemistry" Leer-makers, P.A. and Weisberger, A. Ed. Lamola, A.A. and Turro, N.J. Interscience Publisher, New York, 1969. 188. Stern, 0. Volmer, M. Physik. Z. 1919, 20, 183. 189. Wagner, P.J. i n "Creation and Detection of Excited State", Vol. I, Part 4, Marcel Dekker, New York, 1971, p. 173. 190. Chan, C.B., Schuster, D.I. J . Am. Chem. Soc. 1982, 104, 2928 and references c i t e d therein. 191. Bellus, D., Kearns, D.R., Schaffner, K. Helv. Chim. Acta 1969, 52, 971. 192. Zimmerman, H.E., Wilson, J.W. J . Am. Chem. Soc. 1964, 86, 4036. 193. Schuster, D.I., Muniz, I.M., Chan, C.B. Tet. Let t . 1981, 22, 1187. 194. Turro, N.J. "Modern Molecular Photochemistry", Benjamin/Cumming Publishing Co., Menlo Park, C a l i f o r n i a , 1978, Ch. 10 and 11. 195. Zimmerman, H.E. i n "Rearrangement i n Ground and Excited States". P. de Mayo, Ed. Academic Press, New York, 1980, Vol. 3 Ch. 16. 196. Ch. 17 and 18 of r e f . 195. 313 -197. Michl, J . Mol. Photochem. 1972, 4, 257 and 243. 198. Turro, N.J., Cherry, W.R., Mirbach, M.F. J . Am. Chem. Soc. 1977, 99, 7388. 199. Scheffer, J.R., Gaylor, R.E., Zakarous, T., Dzakpasu, A.A. J . Am.  Chem. Soc. 1977, 99, 7726. 200. Scharf, H.D. Fluschlaner, J . , Leismann, H., Ressler, I., Schleker, W., Weitz, R. Angew. Chem. Int. Ed. Eng. 1979, 18, 652. 201. For a general review see Solar Energy Chemical Conversion and Sto-rage. Ed. Hautala, R.R., King, R.B., Kutal, C. Humana Press, C l i f t o n , N.J. 1979. 202. Gougoutas, J.Z. Pure and Appl. Chem. 1971, 27 (1971). 203. Gougoutas, J.Z., Naae, D.G. J . Phys. Chem. 1978, 82, 393. 204. Eaton, P.E. Acc. Chem. Res. 1968, 1, 50. 205. de Mayo, P. Acc. Chem. Res. 1971, 4, 41. 206. Hammond, G.S., Stout, C.A., Lamola, A.A. J. Am. Chem. Soc. 1964, 86, 3103. 207. Morrison, H., Cu r t i s , H., McDowell, T. J . Am. Chem. Soc. 1966, 88, 5415. 208. A r i e l , S., Askari, S.H., Scheffer, J.R., Tro t t e r , J . Tet. Let t . 1985, 27, 783. 209. Nakanishi, K., Solomon, P.H. "Infrared Absorption Spectroscopy", Holden-Day Inc., San Fransisco, 1977. 210. Cormier, R.A., Schreiber, W.L., Agosta, W.C. J . Chem. Soc. Chem.  Commun. 1972, 729. 211. Roth, H.J., E l Raie, M.H. Tet. Let t . 1970, 2445. see also r e f . 194. 212. See Chapter 17 and 18 of r e f . 195 for leading references. 213. Pappas, S.P., Blackwell, J.E., Tet. L e t t . 1968, 3337. 214. Toda, M., Maeda, T. Chem. Industry. 1976, 742. 215. Pfau, M., Sarver, E.W., Heindel, N.D. Compt. Rend. (C) 1969, 268, 1167. 216. Yates, P., McKay, A.C., Garneau, F.X. Tet. Let t . 1968, 5389. - 314 -217. Hammond, G.S., Leermakers, P.A. J . Am. Chem. Soc. 1962, 84, 207. 218. Turro, N.J., Hammond, G.S. Mol. Photochem. 1972, 4, 427. 219. Wagner, P.J., Hammond, G.S. Adv. Photochem. 1968, 5, 21. 220. de Boer, CD., Herkstroder, W.C, Marchetti, A.P., Schultz, A.C, Schlessingner, R.H. J . Am. Chem. Soc. 1973, 95, 3963. 221. Wagner, P.J., Kemppainen, A.K., Schott, H.N. J . Am. Chem. Soc. 1970, 92, 5280. 222. Bondi, A. J . Phvs. Chem. 1964, 68, 441. 223. A r i e l , S., Askari, S., Scheffer, J.R., Tro t t e r , J . , Walsh, L. Am. Chem. Soc. 1984, 106, 5726. 224. A r i e l , S., Askari, S., Scheffer, J.R., Trotter, J . , Walsh, L. i n "Organic Phototransformations i n Nonhomogeneous Media", Fox, M.A. Ed. ACS, Symposium Series 278, American Chemical Society, Washing-ton, D.C 1985, Ch. 15. 225. Oren, J . , Schlufer, L., Schamuchi, V., Fuchs, B. Tet. Let t . 1984, 25, 981. 226. Korte, D.E., Hegedus, L.S., Wirth, R.K. J . Org. Chem. 1977, 42, 1327. 227. Northcote, P. Undergraduate D i s s e r t a t i o n , UBC, 1985. 228. A r i e l , S., Tro t t e r , J . Acta. Crvst. 1985, C41, 295. 229. Gloor, J . , Schaffner, K. Helv. Chim. Acta. 1974, 57, 1815. 230. See other references c i t e d i n r e f . 115. 231. Wolf, S., Schreiber, W.L., Smith, A.B. I l l , Agosta, W.C. J . Am.  Chem. Soc. 1972, 94, 7497. 232. Kobayashi, T., Murono, M., Sato, H., Nakanishi, K. J . Am. Chem.  Soc. 1972, 94, 2863. 233. Herz, W. , Iyer, V.S., Nan, M.C, S a l t i e l , J . J. Am. Chem. Soc. 1977, 99, 2704. 234. Corey, E.J., Suggs, J.W. Tet. Lett. 1975, 2647. 235. C a r g i l l , R.L., Bundy, W.A., Pond, D.M., Sears, A.B., S a l t i e l , J . , Winterle, J . Mol. Photochem. 1971, 3, 123. 315 -236. We thank Professor H.J. L i u for providing us the samples of these two compounds. For synthesis of dienones 119 and 120, see Brown, E.N.C. Ph.D. Thesis, U n i v e r s i t y of Alberta, Edmonton, Canada, 1980. 237. A r i e l , S., Trotter, J . Acta. Cryst. 1984, C40, 2084. 238. Dj e r a s s i , C. Pure and Appl. Chem. 1964, 9, 159. 239. D j e r a s s i , C , von Mutzenbecher, G., Fajkos, J . , Williams, D.H., Boudzikewics, H. J . Am. Chem. Soc. 1965, 87, 817. 240. Kasha, M. Radiation Research 1960, Suppl. 2, 243. 241. Calvert, J.G., P i t t s , J.N., J r . , "Photochemistry", Wiley, New York, 1966, 249-258. 242. Taylor, R., Kennard, P., V e r s i c h e l , W. J . Am. Chem. Soc. 1983, 105, 5761. 243. Olovsson, I., Croat. Chem. Acta 1982, 55, 171. 244. Taylor, R., Kennard, D. Acc. Chem. Res. 1984, 17, 320. 245. Sugiyama, N., Nishio, T., Yamada, K., Aoyama, H. B u l l . Chem. Soc. Jpn. 1970, 43, 1879. 245a.See Chapter 20 of Ref. 195. 246. Hoffmann, R., Svennson, J.R. J . Phvs. Chem. 1970, 74, 415. 247. Bonneau, R. J . Am. Chem. Soc. 1980, 102, 3816. 248. Devaquet, A. J . Am. Chem. Soc. 1972, 94, 5160. 249. Jones, C.R., Kearns, D.R. J. Am. Chem. Soc. 1977, 99, 344. 250. Schuster, D.I., Bonneau, R., Dunn, D.A., Rao, J.M. Jousset-Dubien, J. J . Am. Chem. Soc. 1984, 106, 2706. 250a.Pienta, N.J. J . Am. Chem. Soc.. 1984, 106, 2704. 251. Murv, S.L. "Handbook of Photochemistry", Marcel Dekker, Inc., N.Y. 1973. 252. Pe r r i n , D., Armarego, W.L.F., Perr i n , D.R. " P u r i f i c a t i o n of Labo-ratory Chemicals", 2nd Ed., Pergaman Press, Oxford, 1982. 253. Fieser, L.F. Arade, M.I., J . Am. Chem. Soc.. 1956, 78, 778. 254. Dekkev, J.K. J. South A f r i c . Chem. S o c . 1968, 1392. 

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