@prefix vivo: . @prefix edm: . @prefix ns0: . @prefix dcterms: . @prefix skos: . vivo:departmentOrSchool "Science, Faculty of"@en, "Chemistry, Department of"@en ; edm:dataProvider "DSpace"@en ; ns0:degreeCampus "UBCV"@en ; dcterms:creator "Chiu, Norman Wing Kwai"@en ; dcterms:issued "2011-09-23T16:14:21Z"@en, "1964"@en ; vivo:relatedDegree "Master of Science - MSc"@en ; ns0:degreeGrantor "University of British Columbia"@en ; dcterms:description """The thermal and photolytic decomposition of cis and trans_-3,5-dimethyl-3-acetyl-Δ¹-pyrazoline have been found to give six products. They have been separated and identified as 2,3,5-trimethyl-Δ²-dihydrofuran, cis and trans-1,2-dimethyl-1- acetyleyclopropane, cis and trans-3-methyl-3-hexen-2-one and 3-methyl-4-hexen-2-one. The formation of cyclopropanes by photolysis showed some degree of stereospecifIcity. Both pyrolysis and photolysis yielded olefins with high degree of stereospecificity. 2,3,5-TrImethyl-Δ²-dihydrofuran was a major product from the decomposition of cis-3,5-dimethyl-3-acetyl-Δ¹ -pyrazoline only. Pyrolysis gave a higher ratio of olefins to cyclopropanes than photolysis. These decomposition reactions gave results analogous to those of cis and trans-3,5-dimethyl-3-carbomethoxy-Δ¹-pyrazoline. The product compositions from both the pyrolysis and photolysis of cis and trans_-3,5-dimethyl-3-carbomethoxy-Δ¹-pyrazoline have been found to show a small and regular influence of the solvent and this has been related to the dielectric constant of the solvent. Pyrolysis and photolysis gave an olefin to cyclopropane ratio of 57:43 and 21:79, respectively, in formamide, and 7:93 and 5:95, respectively, in cyclohexane. A small kinetic solvent effect has been observed for the pyrolysis of 3,5-dimethyl-3-carboraethoxy-Δ¹-pyrazoline. The rate of pyrolysis as followed by the rate of nitrogen evolution has been found to decrease for the following series of solvents: dl-n-butyl ether, tetralin, nitrobenzene and form-amide. These rates were all within a factor of three. The absence of rate enhancement in a solvent of high dielectric constant has been used as an argument against an ionic Intermediate in these reactions. Liquid phase photolysis of trans-3,5-dimethyl-3-carbo- methoxy-Δ¹-pyrazolIne at various temperatures ranging from -55ᵒ to 58ᵒ did not show appreciable change in the product compositions attributable to the influence of temperature. The solvent temperature therefore does not affect the amount of quenching of any "hot" intermediate. Photolysis and pyrolysis of cis and trans-3,5-dimethy1-3-carbomethoxy-Δ¹ -pyrazoline under identical conditions did not give the same product composition. This suggested the two reactions do not have a common Intermediate. No isomerization between the cis and trans-3,5-dimethyl-3-carbomethoxy-Δ¹-pyrazolines has been observed as shown by the partial pyrolysis and photolysis of the trans-pyrazoline. These results are discussed In view of current mechanistlc proposals for the pyrolysis and photolysis of Δ¹-pyrazolines."""@en ; edm:aggregatedCHO "https://circle.library.ubc.ca/rest/handle/2429/37597?expand=metadata"@en ; skos:note "PYROLYSIS AND PHOTOLYSIS OP o i s AND trans-3,5-DIMETHYL-3-ACETYL-A 1 -PYRAZOLINE AND o i s AND trans-3,5-DIMETHYL-3-CARBOMETHOXY-A 1-PYRAZOLINE by NORMAN WING KWAI CHIU B.Sc., Dalhousie U n i v e r s i t y , 1962 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department o f CHEMISTRY We aopept t h i s t h e s i s as ponforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA J u l y , 1964 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of • B r i t i s h Columbia,, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study * .I f u r t h e r agree that per-m i s s i o n f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the. Head of my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood th a t ; c o p y i n g or p u b l i -c a t i o n . o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n permission,. Department of CHEMISTRY The U n i v e r s i t y . o f B r i t i s h Columbia/ Vancouver ' 8 , Canada Date - i i -ABSTRACT The thermal and p h o t o l y t i c decomposition of c i s and tra_ns_ - 3 , 5-dimethyl - 3-acetyl -A\" 1\"-pyrazoline have been found to g i v e s i x p r o d u c t s . They have been separated and i d e n t i f i e d as 2 , 3 , 5-trimethyl-/£-dihydrofuran, c i s and t r a n s - 1 , 2 - d i m e t h y l - l -a c e t y l e y c l o p r o p a n e , c i s and trans - 3-methyl - 3-hexen - 2-one and 3-methyl -4-hexen -2-one. The f o r m a t i o n of eyclopropanes by p h o t o l y s i s showed some degree of s - t e r e o s p e c i f I c i t y . Both p y r o l y s i s and p h o t o l y s i s y i e l d e d o l e f i n s w i t h h i g h degree of 2 s t e r e o s p e c i f i c i t y . 2,3,5-TrImethyl-££\"-dihydrofuran was a major product from the decomposition of c i s - 3 , 5 - d i m e t h y l - 3 - a c e t y l -A - p y r a z o l i n e o n l y . P y r o l y s i s gave a h i g h e r r a t i o o f o l e f i n s t o eyclopropanes than p h o t o l y s i s . These decomposition r e a c t i o n s gave r e s u l t s analogous to those of c i s and t r a n s - 3 , 5 - d i m e t h y l -3-earbomethoxy-^-pyrazoline. The product compositions from both the p y r o l y s i s and p h o t o l y s i s of c i s and trans_ - 3 , 5-dimethyl - 3-carbomethoxy-^\"-p y r a z o l i n e have been found to show a s m a l l and r e g u l a r i n f l u -ence of the s o l v e n t and t h i s has been r e l a t e d t o the d i e l e c t r i c c onstant of the s o l v e n t . P y r o l y s i s and p h o t o l y s i s gave an o l e f i n to cyclopropane r a t i o of 57*43 and 21*79* r e s p e c t i v e l y , i n formamide, and 7*93 and 5*95, r e s p e c t i v e l y , i n cyclohexane. A s m a l l k i n e t i c s o l v e n t e f f e c t has been observed f o r the p y r o l y s i s of 3 , 5-dimethyl - 3-carboraethoxy-/^-pyrazoline. The r a t e of p y r o l y s i s a s . f o l l o w e d by the r a t e of n i t r o g e n evo-- I l i -l u t i o n has been found to decrease f o r the f o l l o w i n g s e r i e s of solvents« d l - n - b u t y l e t h e r , t e t r a l i n , nitrobenzene and form-amide. These r a t e s were a l l w i t h i n a f a c t o r of t h r e e . The absence of r a t e enhancement i n a s o l v e n t of h i g h d i e l e c t r i c constant has been used as an argument a g a i n s t an i o n i c I n t e r -mediate i n these r e a c t i o n s . L i q u i d phase p h o t o l y s i s of t r a n s - 3 , 5 - d i m e t h y l - 3 - c a r b o -methoxy~£^-pyrazolIne at v a r i o u s temperatures ra n g i n g from o _.o -55 to 58 d i d not show a p p r e c i a b l e change i n the product compositions a t t r i b u t a b l e to the i n f l u e n c e of temperature. The s o l v e n t temperature t h e r e f o r e does not e f f e c t the amount of quenching of any \"hot\" i n t e r m e d i a t e . P h o t o l y s i s and p y r o l y s i s of c i s and trans - 3 , 5-dimethy 1 -3-carbomethoxy-A - p y r a z o l i n e under i d e n t i c a l c o n d i t i o n s d i d not g i v e the same product composition. T h i s suggested the two r e a c t i o n s do not have a common Intermediate. No i s o m e r i z a t i o n between the c i s and t r a n s - 3 , 5 - d i m e t h y l -3-carbomethoxy - A L-pyrazolines;has been observed as shown by the p a r t i a l p y r o l y s i s and p h o t o l y s i s of the t r a n s - p y r a z o l i n e . These r e s u l t s are d i s c u s s e d In view of c u r r e n t mecha-*1 n i s t l c p r o p o s a l s f o r the p y r o l y s i s and p h o t o l y s i s of & -p y r a z o l i n e s . - v i l i ACKNOWLEDGEMENT The author wishes to express h i s s i n c e r e a p p r e c i a t i o n to Dr, D. E. MeGreer who^ suggested t h i s r e s e a r c h p r o j e c t and under whose guidance and encouragement t h i s r e s e a r c h was performed. The author Is indebted to Mrs. E. B r i o n and Mr. P. Horn f o r the n u c l e a r magnetic resonance s p e c t r a , to Dr. A. Bernhardt, Mrs. A. A l d r i d g e and Mrs. C. Jenkins f o r the mic r o a n a l y s e s . F i n a n c i a l a s s i s t a n c e from the N a t i o n a l Research C o u n c i l of Canada f o r t h i s r e s e a r c h p r o j e c t i s deeply a p p r e c i a t e d . _ i v -TABLE OF CONTENTS Page I . I n t r o d u c t i o n 1 I I , S y n t h e s i s and I d e n t i f i c a t i o n of 3,3 ,,5-Trisubstituted /5^-Pyrazolines 1 1. c i s and t r a n s - 3 , 5 - d i m e t h y l - 3 - c a r b o m e t h o x y -p y r a z o l i n e 7 2. c i s and t r a n s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - A 1 - p y r a z o l i n e .. 9 I I I . S e p a r a t i o n and I d e n t i f i c a t i o n of Products from the De-composition of 3,5-DImethyl-3-aeetyl - A 1~pyrazolines ... 13 IV. Decomposition of 3 , 3 , 5 - T r i s u b s t i t u t e d Z^-Pyrazolines .. 21 V. D i s c u s s i o n 30 V I . Experimental 1. General statement 4 l 2. N - N i t r o s o - N - e t h y l urea 41 3. Diazoethane 42 4. Methyl Isopropenyl ketone 43 5. S ^ - D i m e t h y l - S - a c e t y l - ^ - p y r a z o l i n e 43 6. S e p a r a t i o n of e i s and tr_ans_-3,5-dimethyl-3-a c e t y l - ^ - p y r a z o l i n e 44 7. S e p a r a t i o n of c i s and trans-3,5-dimethyl-3-c a r b o m e t h o x y - ^ - p y r a z o l l n e 44 8. trans-3,5-Dimethyl-3-carbomethoxy-A^-pyrazollne hydrobromide 45 9. Thermal p y r o l y s i s of 3,5-dimethyl-3-acetyl-AJ\"-pyrazoline 46 9a. 2,4-Dinltrophenyl hydrazones 59 - V -Page 10. Thermal p y r o l y s i s of c i s and t r a n s - 3 , 5 - d i m e t h y l -3 - a c e t y l - A 1 - p y r a z o l i n e 50 11. Vapor phase p y r o l y s i s o f c i s and t r a n s - 3 , 5 - d i m e t h y l -3-acet.yl-^\"-pyrazoline 50 12. L i q u i d phase p y r o l y s i s o f 3 , 5-dimethyl - 3 -1 a c e t y l - A - p y r a z o l i n e 51 13. L i q u i d phase p y r o l y s i s of c i s and t r a n s - 3 , 5 -d i m e t h y l - 3 - a e e t y l - ^ \" - p y r a z o l i n e 52 14. P h o t o l y s i s o f 3 , 5-dimethyl - 3-acetyl-£J['-pyrazoline •••• 52 15. P h o t o l y s i s of c i s and t r a n s - 3 , 5 - d i m e t h y l - 3 -a c e t y l - ^ \" - p y r a z o l i n e 53 16. Vapor phase p y r o l y s i s of c i s and tra_ns - 3 , 5-di-methyl - 3-earbomethoxy-Z^-pyrazoline 53 17. L i q u i d phase p y r o l y s i s of c i s and t r a n s - 3 , 5 - d i methyl - 3-carbomethoxy-^\"-pyrazoline i n v a r i o u s s o l v e n t s 53 18. P h o t o l y s i s o f trans - 3 * 5-dimethyl - 3-carbomethoxy-^ \" - p y r a z o l i n e at v a r i o u s temperatures 5^ 19. P h o t o l y s i s of c i s and t r a n s - 3 , 5 - d i m e t h y l - 3 - c a r b o -methoxy-^\"-pyrazoline i n Formamide at 23° 56 20. P a r t i a l p y r o l y s i s of t r a n s - 3 , 5 - d i m e t h y l - 3 - c a r b o -m e t h o x y - ^ - p y r a z o l i n e 56 21. P a r t i a l l i q u i d phase p y r o l y s i s of t r a n s - 3 , 5 - d i -methyl-3-carbomethoxy-/£\"-pyrazoline 57 22. K i n e t i c s t u d i e s of the p y r o l y s i s of 3 , 5-dimethyl - 3 -carbomethoxy-/^-pyrazoline i n v a r i o u s s o l v e n t s ....... 57 BIBLIOGRAPHY 60 - v i -LIST OF FIGURES F i g u r e Page I . Mechanism of ^ - p y r a z o l i n e f o r m a t i o n 1 I I . I o n i c mechanism f o r the p y r o l y s i s of 3 ,4-dimethyl-3-carbomethoxy-A - p y r a z o l i n e s , 3 I I I . Products from the p h o t o l y s i s of 3*4~dimethyl - 3 -earbomethoxy-^s-pyrazolines 5 IV. N.m.r. a b s o r p t i o n showing.,the s e p a r a t i o n of 3*5-dimet.hyl - 3-carbomethoxy-^-pyrazoline i n t o i t s c i s and tr a n s isomers 8 V. N.m.r. sp e c t r a of trans-3,5-dlmethyl-3-earbomethoxy-&t-pyrazoline showing s p l i t t i n g s of C^-hydrogens .... 12 V I . Products from the decomposition of 3 , 5-dimethyl - 3 -earbomethoxy-Zr-pyrazolInes 13 VIIA. P r e p a r a t i v e vapor chromatogram showing the separa-t i o n of products from the decomposition of 3 * 5-di-m e t h y l - ^ - p y r a z o l i n e s lh VIIB. A n a l y t i c a l vapor phase chromatogram showing the s e p a r a t i o n of 3-methyl-4-hexen-2-one and t r a n s -1 , 2-dimethyl-l-aeety.lcyclopropane 14 V I I I . Products from the decomposition of 3 , 5-dimethyl-3-acetyl-£r-pyrazolines 15 2 IX. N.m.r. spectrum o f 2 , 3 , 5 - t r i m e t h y l - & - d i h y d r o f u r a n .. 17 X. S t e r e o c h e m i s t r y o f the form a t i o n of o l e f i n s from ^ • - p y r a z o l i n e 38 XI. Apparatus f o r p h o t o l y s i s at low temperature 55 X I I . F i r s t o r d e r p l o t of l o g ^/(V^-V^.) verse s time f o r the p y r o l y s i s of 3 , 5-dimethyl - 3-carbomethoxy-^s L-p y r a z o l i n e i n v a r i o u s s o l v e n t s 58 ~ v i i -LIST OP TABLES Table Page I . N.m.r. data of c i s and trans_-3,5-»diraethyl -3-acetyl-A ^ ~ p y r a z o l i n e and c i s and t r a n s - 3 3 5 - d i m e t h y l - 3 -carbomethoxy-£i\"~pyrazoline 11 I I . Product compositions f o r the decomposition of 3 , 5 - d i m e t h y l - 3 - a c e t y l - / ^ - p y r a z o l i n e s ' 22 I I I . Product compositions f o r the decomposition of 3<>5-d i m e t h y l - S - c a r b o m e t h o x y - ^ - p y r a z o l l n e s 23 IV. Product compositions f o r the sealed-tube p y r o l y s i s of c i s and trans_ - 3 , 5-dimethyl - 3-carbomethoxy-£^-o , p y r a z o l i n e i n v a r i o u s s o l v e n t s at 125 2o V. Product compositions of p h o t o l y s i s of c i s and trans - 3 , 5-dimethyl - 3-carbomethoxy-ft''-pyrazoline 27 - 1 -I . INTRODUCTION The a d d i t i o n of diazoalkanes to o(,/3-unsaturated c a r b o n y l compounds to form A ^ - p y r a z o l i n e s (1-5) and the p y r o l y s i s of these A ^ - p y r a z o l i n e s to form cyclopropanes (6,7) have been known f o r many y e a r s . Both the a d d i t i o n and p y r o l y s i s mecha-nisms have been the s u b j e c t of d i s c u s s i o n . In p a r t i c u l a r , the meehanism f o r the p y r o l y s i s of A ^ - p y r a z o l i n e s i s s t i l l not s e t t l e d at p r e s e n t . The a d d i t i o n mechanism has been proven r e c e n t l y , by Huisgen and coworkers (8-10) to be a one-step m u l t i p l e - c e n t e r a d d i t i o n , s i m i l a r to the 1,3-dlpolar a d d i t i o n r e a c t i o n , r a t h e r than the two-step i o n i c mechanism (6,11) p r e v i o u s l y proposed. These routes to p y r a z o l i n e s are shown i n F i g u r e I . I t has a l s o R 1 R \\ s C=C R J Y RCHN^ ,one-step two-step R — —H , —CH3 Y —-.COCH3, -COOCH3 R 1 • R 2 CT l^Y H ! 1 X J R R 1 R 2 R ^ f — W ^ N \" ^ Y I I R* R ^ X N ^ I I I R< FIGURE I - Mechanisms of A 1*-pyrazoline formation, been shown (6,7) t h a t the carbon o^to the n i t r o g e n In the diazo-alkane adds to the double bond at the carbon 0 to the c a r b o n y l - 2 -group i n the o l e f i n . C I s - a d d i t i o n (6,7) i s i n d i c a t e d by the r e -a c t i o n of diazomethane w i t h methyl t i g l a t e (IV) and methyl a n g e l a t e (V) to g i v e c i s and trans - 3,4-dimethyl - 3-carbomethoxy-£^-pyrazoline (VI and VII) r e s p e c t i v e l y (12). The thermal decomposition of A ^ - p y r a z o l i n e s has been r e -p o r t e d t o y i e l d a product mixture c o n s i s t i n g of cyclopropane and o l e f i n s (6,7,13-19) i n some i n s t a n c e s , w h i l e i n others the mixture a l s o c o ntained the corresponding A 2 - p y r a z o l i n e (20) or no o l e f i n s (3,2l) at a l l . Few s t u d i e s have been made to d e t e r -mine the mechanism of the p y r o l y s i s r e a c t i o n s . From l i m i t e d I n -f o r m a t i o n both i o n i c (6,11,12) and d i r a d i c a l (20,22-24) mecha-nisms f o r the thermal decomposition of ^ - - p y r a z o l i n e s have been proposed to e x p l a i n these p r o d u c t s . These p r o p o s a l s were made on the assumption that eyclopropanes are formed w i t h r e t e n t i o n of the geometry present In the o r i g i n a l p y r a z o l i n e s . Recent o b s e r v a t i o n s of p a r t i a l and complete l o s s of the above mention-ed geometry have been r e p o r t e d (12,21,25). For example, van Auken and Rinehart r e p o r t e d (12) t h a t the p y r o l y s i s of t r a n s -3 ,4-dimethyl - 3-earbomethoxy-A 1-pyrazoline (VII) g i v e s c i s - 1 , 2 -dimethyl-l-carbomethoxycyclopropane (X), t r a n s - 1 , 2 - d i m e t h y l - l -carbomethoxycyclopropane ( X I ) , methyl 2 , 3-dimethyl - 2-butenoate (XII) and methyl 2 , 3-dimethyl - 3-butenoate (XIII) In the r a t i o 1.00.1.22*1.16:©.155 and s i m i l a r l y , c i s - 3 , 4 - d i m e t h y l - 3 - c a r b o -m e t h o x y - ^ - p y r a z o l i n e (VI) g i v e s X, XI, XII,and X I I I i n the r a t i o 1 .00X0 .70*3.73*0.24. These authors have suggested the f o l l o w i n g m o d i f i e d i o n i c mechanism (F i g u r e I I ) , which postu-- 3 -H H 3 0 - 6 COOCH, COOCH, .N GH 3 VI (methyls c i s ) or V I I (methyls t r a n s ) V I I I -N, H H - ^ C ^ OOCH, C H , +CH, IX C O O C H , H H 3 C * . ~ C O O C H 3 XI H-.C CH-, 3 \\ / 3 c = c H - C * ' NC00CH o 3 3 XII E 2 \\ / H 3 C — C H H „ C / C O O C H , X I I I FIGURE I I - I o n i c mechanism f o r the p y r o l y s i s of 3 ,4-dimethyl - 3-carbomethoxy - £ i-pyrazolines. l a t e s t h a t r o t a t i o n occurs i n the diazonium b e t a i n e i n t e r m e d i -ate ( V I I I ) , and thus r a c e m i z a t i o n at the anion c e n t e r can take p l a c e . The s l i g h t degree of s t e r e o s e l e c t i v i t y , t h a t I s , 1 . 2 2 * 1 . 0 0 i n f a v o r of the trans-eyelopropane XI from the t r a n s -p y r a z o l i n e V I I and 1 . 0 0 * 0 . 7 0 i n f a v o r of the c i s - e y e l o p r o p a ne X from the c i s - p y r a z o l i n e V I , was e x p l a i n e d by the sug g e s t i o n t h a t the l o s s of n i t r o g e n i n going from V I I I t o IX i s s l i g h t l y f a s t e r than the r o t a t i o n i n V I I I due to the f a c t t h a t the l a t -t e r Involves c o n s e c u t i v e e c l i p s e d i n t e r a c t i o n o f methyl-carbo-- 4 -methoxy and methylenediazonium-methyl which p r o v i d e s some bar -r i e r to r o t a t i o n . I n s p i t e of the proposed common- in t e r m e d i a t e f o r the p y r o l y s i s of p y r a z o l i n e s VI and V I I , the r a t i o of e y c l o -propanes t o o l e f i n s are d i f f e r e n t , t h a t i s , .1.70 2 3.97 f o r the c i s - p y r a z o l i n e VI and 2.22°-1.31 f o r the t r a n s - p y r a z o l i n e V I I . Although t h i s mechanism would p r e d i c t the c o n v e r s i o n of the i n t e r m e d i a t e V I I I to p y r a z o l i n e s VI or V I I f a s t e r than n i t r o g e n l o s s from V I I I , i t was shown that the p a r t i a l p y r o l y s i s of c i s -3,4~dimethyl -3-carbomethoxy\"-£ L-pyrazoline. (VI) g i v e s no r e -arrangement In the recovered p y r a z o l i n e sample (12). T h e r e f o r e the v a l i d i t y of t h i s I o n i c mechanism f o r the thermal decom-p o s i t i o n o f ^ - p y r a z o l i n e s needs f u r t h e r examination. P h o t o l y s i s of c i s -and trans_ - 3 , 4-dimethyl - 3-carbomethoxy-^ - p y r a z o l i n e (VI and VII) has been r e p o r t e d (.12) to g i v e s t e r e o s p e c i f i c a l l y c i s and t r a n s - l , 2 - d i m e t h y l - l - c a r b o m e t h o x y -cyclopropane (X and XI) r e s p e c t i v e l y , and methyl t i g l a t e (IV) and methyl angelate (V) r e s p e c t i v e l y (Figure I I I ) . Rinehart and van Auken (12) have proposed a molecular mechanism to ex-p l a i n these o b s e r v a t i o n s of p h o t o l y s i s of ^ \" - p y r a z o l i n e s . The t r a n s i t i o n s t a t e i n v o l v e d would be XIV i n which the breakage of bonds N n - C r - and N o - 0 o and the f o r m a t i o n of bonds C 0 - C j - and 1 5 2 3 3 5 N 1-N 2 are simultaneous, hence the eyclopropanes formed r e t a i n the geometry which i s present i n the p y r a z o l i n e s . S i m i l a r l y , the s t e r e o s p e c i f i e r e g e n e r a t i o n of methyl t i g l a t e (IV) and methyl angelate (V) c o u l d then be e x p l a i n e d through a s i m i l a r t r a n s i t i o n s t a t e XV. T h e r e f o r e on the b a s i s of these p h o t o l y s i s _ 5 -r e s u l t s , the p h o t o l y s i s o f A ^ - p y r a z o l i n e s has been assumed to he s t e r e o s p e c i f i c i n g e n e r a l . H H3C-£OOCH, VI X .COOCH, H COOCHQ \\ / J / = \\ H.3C CH 0 5 3 IV _CH, VII XI H 0C .C00CH o 3 \\ / 3 N C H 3 V FIGURE I I I - Products from the p h o t o l y s i s of 3 , 4 - d i -methyl-3-carbomethoxy-,&?--pyrazolInes. COOCH 3 3 \\/ A V XIV H H 30- I xv OOCH, H, In t h i s l a b o r a t o r y however, a p r e l i m i n a r y i n v e s t i g a t i o n (26) has shown t h a t the p h o t o l y s i s r e a c t i o n s of c i 3 and t r a n s -3,5-dimethyl-3-earbomethoxy-£ L-pyrazoline (XVI and XVII) g i v e mixtures o f cyclopropanes, w i t h some l o s s of s t e r e o s p e c i f i c i t y , and o l e f i n p r o d u c t s . GOOCH, J C O 0 C I L N HH. 3 XVI H 3 C 1 -fS)H 3 XVII 6 With the f i n d i n g t h a t c i s and t r a n s - S ^ - d i a l k y l - A 1 -p y r a z o l i n e s c o u l d he separated by f r a c t i o n a l d i s t i l l a t i o n , a new system f o r s t u d y i n g the s t e r e o c h e m i s t r y has become a v a i l -a b l e . Thus, the purpose of the present i n v e s t i g a t i o n i s to examine the thermal and p h o t o l y t i c decompositions of c i s and t r a n s - 3 , 5 - d i m e t h y 1 - 3 - c a r b o m e t h o x y - p y r a z o 1 i n e (XVI and XVII) and t h e i r analogs, e i s and t r a n s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - A 1 -p y r a z o l i n e (XVIII and XIX) i n an attempt t o f i n d out more i n f o r m a t i o n about these r e a c t i o n s . ,COCH ,COCH 3 XVIII XIX _ 7 -I I . SYNTHESIS AND IDENTIFICATION OF 3 ,3 ,5-TRISUBSTITUTED A 1-PYRAZOLINES I I - l . c i s and trans - 3 , 5-dimethyl - 3-carbomethoxy-£r-pyrazoline (XVI and XVII) 3 , 5-Dimethyl - 3-carbomethoxy-/S L-pyrazoline (XX) prepared by the a d d i t i o n of methyl methacrylate (XXI) to diazoethane i n e t h e r (17) has been shown by n.m.r. a n a l y s i s to be a 40^60 mixture of the two p o s s i b l e geometric isomers. S e p a r a t i o n of H C00CH o COOCH„ t h i s mixture (Figure IV) by f r a c t i o n a l d i s t i l l a t i o n u s i n g a Nester and Faust 1 8-inch by 6-mm. s p i n n i n g band s t i l l gave a lower b o i l i n g f r a c t i o n up to 93$ pure and a h i g h e r b o i l i n g f r a c t i o n o f 99+$ p u r i t y . N.m.r. analyses of these two f r a c t i o n s and the o r i g i n a l mixture p y r a z o l i n e showed t h a t the lower b o i l i n g isomer was the 40$ component and the h i g h e r b o i l i n g isomer was the 60$ component. P h o t o l y s i s r e a c t i o n s have been c a r r i e d out on both the lower and the h i g h e r b o i l i n g f r a c t i o n s , and i t was found (complete r e s u l t s w i l l be d i s c u s s e d l a t e r ) t h a t the former g i v e s mainly cis - 1 , 2-dimethyl-l-carbomethoxycyclopropane (X) and the l a t t e r g i v e s mainly trans - 1 , 2-dimethyl-l-carbomethoxy-3 3 H XXI XX „ 8 -[A) Lower b o i l i n g f r a c t i o n 'B) P y r a z o l i n e mixture XX (C) Higher b o i l i n g f r a c t i o n (C) XVII (99*$) XVI si\" (B) XVII (60$) (A) X V I (4b$) XVII (7$), 6.3 { XVI (93$) 6:3 r FIGURE IV - N.m.r. a b s o r p t i o n s showing the s e p a r a t i o n of 3 ,5-dimethyl - 3-carbomethoxy-^ - p y r a z o l i n e (XX) i n t o i t s c i s (XVI) and t r a n s (XVII) isomers. - 9 -cyclopropane ( X I ) . On the b a s i s of the f a c t t h a t the photo-1 l y s i s of A. - p y r a z o l i n s g i v e s cyclopropane s t e r e o s p e c i f I c a l l y (12), the lower b o i l i n g isomer was assign e d the s t r u c t u r e c i s -. 3 , 5\"dimethyl - 3-carbomethoxy-A* 1'-pyrazoline (XVI) and the h i g h e r b o i l i n g isomer was assig n e d the s t r u c t u r e t r a n s - 3 , 5 - d i m e t h y l -3~carbomethoxy-£^~pyrazoline (XVII). F u r t h e r proof of s t r u c -t u r a l assignments i s based on the h i g h e r y i e l d of the t r a n s -p y r a z o l i n e XVII than the c i s - p y r a z o l i n e XVI on p r e p a r a t i o n . S t e r i c hindrance due to the and methyl groups c i s to each other- i n XVI would slow down I t s fo r m a t i o n when compared to XVII. I n order to o b t a i n more evidence, the hydrobromide s a l t (XXII) of t r a n s - 3 , 5 - d i m e t h y l - 3 - c a r b o m e t h o x y - ^ - p y r a z o l i n e (XVII) has been prepared and i s p r e s e n t l y b e i ng analyzed by the s i n g l e c r y s t a l X-ray method. XXII i s white c r y s t a l l i n e s o l i d w i t h m e l t i n g p o i n t at 152-153°. I I - 2 . c i s and trans - 3 , 5-dimethy 1 - 3-acetyl-A 1\"-pyrazoline (XVIII and XIX) 3 , 5 - D i m e t h y l - 3 - a c e t y l - A 1 - p y r a z o l i n e (XXIII) was prepared by the a d d i t i o n of methyl i s o p r o p e n y l ketone to an e t h e r -methanol s o l u t i o n of diazoethane. I t i s a c o l o r l e s s l i q u i d COCH, H COGH- r |C 5 V / 3 . PCEL fe=C' -|- CH 3CHN 2 e t h e r - ^ . ^ \"\"3 E/ N C H 3 \"* methanof E^(f \" N 5 \" XXIII which b o i l s at 56-57°/!.2 mm. and turns y e l l o w i s h on prolonged - 10 -exposure t o atmosphere. The n.m.r. spectrum of XXIII showed i t to be a 40°-60 mixture of the two p o s s i b l e geometric Isomers and t h e r e was no a b s o r p t i o n of proton a t t a c h e d to a n i t r o g e n atom. F r a c t i o n a l d i s t i l l a t i o n of XXIII by s p i n n i n g band s t i l l at reduced p r e s s u r e gave a lower and a h i g h e r b o i l i n g f r a c t i o n of 81$ and 97$ p u r i t y r e s p e c t i v e l y , and they were found t o be the 40$ and 60$ components of XXIII r e s p e c t i v e l y . The r e s u l t s of the p h o t o l y s i s r e a c t i o n s of the lower b o i l i n g and the h i g h e r b o i l i n g isomers showed t h a t the former g i v e s mainly c i 3 - l , 2 - d i m e t h y l ~ l - a c e t y l c y c l o p r d p a n e (XXIV) and the l a t t e r g i v e s mainly t r a j o s - 1 , 2-dime thy 1-1 -a c e t y l c y c lopropa ne (XXV). T h e r e f o r e on the b a s i s of s t e r i e hindrance d u r i n g the for m a t i o n of 3 , 5-dimethyl - 3-acetyl~£ L-pyrazoline (XXIII) and the r e s u l t s o f the p h o t o l y s i s r e a c t i o n s , the lower b o i l i n g isomer was as s i g n e d t o be c i s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - ^ -p y r a z o l i n e (XVIIl) and the h i g h e r b o i l i n g isomer was as s i g n e d to be t r a n s - 3 , 5 - d i m e t h y l - 3 - a e e t y l - ^ - p y r a z o l i n e (XIX) . T h i s i s analogous t o the assignment t o the c i s and trans_ - 3 , 5-dlmethyl-3-earbomethoxy-£ L-pyrazoline (XVI and XVII). The n.m.r. data o f c i s and t r a n s - 3 , 5 - d i m e t h y l - 3 - c a r b o -m e t h o x y - ^ - p y r a z o l i n e (XVI and XVII) and c i s and t r a n s - 3 , 5 -d i m e t h y l - 3 - a e e t y l - ^ \" - p y r a z o l i n e (XVIII and XIX) a i t t a b u l a t e d i n Table I . TABLE N.m.r. data o f c i s and t r a n s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - ^ - p y r a z o l i n e (XVIII and XIX) and c i s and trans - 3 , 5-dimethyl - 3-carbomethoxy-i£-pyrazollne (XVI and XVII) Sample A c e t y l methyl hydrogens E s t e r methyl hydrogen C^-methyl hydrogen C^-methyl hydrogens -hydro-gens C4-hydros ;ens XVI 6.33 8.38 8.51 5.42 7.68 9.14 s i n g l e t s i n g l e t doublet s e x t e t 2. .doublets 2 doublets J* 7 . 0 J*7 .5 Jgem\"-^ • 9 J g e n T ^ .8 J v i c ~ ^ * 5 J v i c ^ 8 . o XVII 6.27 s i n g l e t 8.63 s i n g l e t 8.55 doublet J=7.0 5.43 s e x t e t J«7.5 8.28 2 doublets ^gem~ 1 2 ,8 J v i c ~ 8 ' 0 8.43 „ d o u b l e t \" 8.56 2 doublets J g e r r T 1 2 ' 6 J v i o \" \" 8 ' 0 8.45 „ d o u b l e t ^ XVIII 7.78 s i n g l e t 8.40 s i n g l e t 8.52 doublet J* 7 . 0 5.66 s e x t e t J^7.4 7.57 9.30 2 doublets 2 doublets Jgem^-'-S.O Jg e m—12.8 J v i e ~ 8 * 7 J v l c - 7 . 7 XIX 7.65 8.63 8.48 5.67 8.53 s i n g l e t s i n g l e t doublet s e x t e t m u l t i p l e t J*6.0 J*7.4 1) A V l l l and AIA were done on • 205& s o l u t i o n i n 0014, AVI and A V I I were done on 30^ . s o l u t i o n i n CCI4, and the values i n parentheses were observed i n 1 0 $ s o l u t i o n . 2) Chemical s h i f t i n t' u n i t and c o u p l i n g constant i n c.p.s. #) Due to the small chemical s h i f t s e p a r a t i o n the outer d o u b l e t s o f the AB system . were not observed (see F i g u r e V ) . - 12 w £ O O C H 3 XVII 81.56? ; 8 . 2 8 * v l c « 8 . 0 \" J v i c * 3 \" 8 ' 0 \" 30$ v/v i n CCli| ! . 8 .45^ 8.43 r J=*8.0^ J«8 .OfM 10% v/v i n C C l ^ FIGURE V - N.m.r. sp e c t r a of t r a n s - 3 , 5 - d i m e t h y l - 3 - c a r b o -methoxy-A 1-pyrazoline (XVII) showing s p l i t t i n g s of C 4-hydrogens. - 13 3* I I I . SEPARATION AND IDENTIFICATION OF PRODUCTS FROM THE DECOMPOSITION OF 3,5~DIMETHYL-3-ACETYL-A*-PYRAZOLINES P r e l i m i n a r y s t u d i e s (17,26) on the decomposition of 3 , 5 -dimethyl - 3-carbomethoxy-A*-pyrazoline (XX), i t s e l s (XVI) and tr a n s (XVII) isomers have shown f i v e products to he formed as shown i n F i g u r e VI ( f o r p h o t o l y s i s , an a d d i t i o n a l product XXI was obtained) H. GOOCH. £OOCH, H , XVI .COOCH. H^C W XVII GOOCH, H CH 0 \\ S 3 CH - C C ^COOCH, 3 2 : XXVI XI CH-jCH- >0HO %=c' g N^OOCH, XXVII ° \\ 3 _ / = S * 3 H - C - C ^ H . C O O C H 3 H 2 C C x C 0 0 C H : CH^ XXVIII XXI FIGURE VI - Products from the decomposition o f 3 , 5 - d i -m e t h y l - S - c a r b o m e t h o x y - ^ - p y r a z o l i n e s . In the present study, the decomposition of 3 , 5-dimethyl-3 - a c e t y l - A - p y r a z o l i n e ( X X I I I ) , i t s c i s (XVIII) and t r a n s (XIX) - 14 -XXXII LI XXV XXIV XXV+XXXII I XIV XXIX \"XXX R e t e n t i o n time d i f -f e r e n c e &0.12 min, B 17.7 15.7 12.2 10.5 6.2 * R e t e n t i o n time i n minutes 1 A FIGURE V I I '- A. P r e p a r a t i v e vapor chromatogram showing the s e p a r a t i o n of products from the decomposition of 3 , 5 - d I m e t h y l - l - a c e t y l - Z r - p y r a z o l i n e s . B. A n a l y t i c a l vapor phase chromatogram showing the s e p a r a t i o n of 3-methyl-4-hexen-2-one (XXXII) and t r a n s - l , 2 - d i m e t h y l - l - a c e t y l c y c l o p r o p a n e (XXV) - 15 -isomers a f f o r d e d a mixture of s i x products as shown by ana-l y t i c a l vapor phase chromatography (Figure VII) w i t h b o i l i n g p o i n t s ranging from 119° to 152°. These products are shown i n Figure V I I I and have been i d e n t i f i e d as described below. Pre-HO COCH, XXIII £OCH, J P w XVIII f^CH, •N H 3C XIX ^OCH-,COCH, TJOCH, XXV / H H3C N0' CH 3 XXIX V CH CH CH 3 \\2 / 3 c = c H OCH C=C / \\ CH 3CH 2 COCH3 XXX ? H3 CH3CH = CH-CH-COCH3 XXXI XXXII FIGURE V I I I - Products from the decomposition of 3,5-dimethyl-S-acetyl-A^-pyrazolines. p a r a t i v e vapor phase chromatographic separation gave f i v e f r a c t i o n s i n which the second f r a c t i o n was found to be a mixture (Figure VII) of 1 -acetyl-tra_ns-l,2-dimethylcyelopro-pane (XXV) and 3-methyl-4-hexen-2-one (XXXII) i n the r a t i o of approximately 85 s15 depending on the c o n d i t i o n of decom-p o s i t i o n . The separ a t i o n of t h i s mixture of XXV and XXXII w i l l be discussed l a t e r . The p y r o l y s i s products have been charac-- 16 -t e r i z e d on the b a s i s of t h e i r n.m.r. and I n f r a r e d s p e c t r a l data and elemental m i c r o a n a l y s i s and t h i s i s d e s c r i b e d below. 2 , 3 * 5-Trimethyl-£ - d i h y d r o f u r a n (XXIX) has been r e p o r t e d (27) to b o i l at 118.5° at 746 mm. which agreed w i t h the v a l u e , o 120 , of t h i s work. I t s i n f r a r e d spectrum i n d i c a t e d the presence of carbon-carbon double-bond a b s o r p t i o n at 5.87M and v i n y l e t h e r a b s o r p t i o n at 8.21M and 9.63 JX (28). There was no i n d i c a t i o n o f a b s o r p t i o n i n the I n f r a r e d or n.m.r. (Fi g u r e IX) sp e c t r a a t t r i b u t a b l e to the a c e t y l methyl protons. N.m.r. ab-s o r p t i o n of an u n r e s o l v a b l e m u l t l p l e t centered at 8.43 *t was a t t r i b u t a b l e t o the methyl groups a t t a c h e d t o C 2 and C^.' There were t h r e e groups of m u l t l p l e t centered a t 7.98 T , 7.40't and 5.59 Y which can be assign e d to the hydrogens on (two hydro-gens) and C (one hydrogen). These t h r e e protons c o n s t i t u t e d a 5 t y p i c a l ABX system (29) w i t h J A B«*tl4 .5 c.p.s., J A Xe> 8 . 0 c.p.s., JB X — 9.5 c.p.s., A^ - ^ 3 5 . 5 c.p.s., A . A X ^ l 4 4 . 5 c.p.s. and A g X ^ 1Q9 c.p.s. In order t o e s t a b l i s h the c y c l i c s t r u c t u r e of t h i s 2 , 3 j 5 - t r i m e t h y l - A - d i h y d r o f u r a n (XXIX), the n.m.r. spectrum of a s i m i l a r c y c l i c compound, the 2-methyl-A?-dihydrofuran (XXX-I I I ) (30) was obtained f o r comparison. The n.m.r. spectrum of XXXIII showed a b s o r p t i o n at 8.30 f ( m u l t i p l e t ) , 5.55 X ( m u l t l -p l e t ) , 7.47 TT* ( m u l t l p l e t ) and 5.78 ( t r i p l e t w i t h Jc=t9.3 c.p. s.) a t t r i b u t a b l e t o C 2 methyl hydrogens, v i n y l hydrogen, G^ and G^ hydrogens r e s p e c t i v e l y . A comparison of the n.m.r. sp e c t r a of XXIX and XXXIII showed good c o r r e l a t i o n between s i m i l a r l y s i t u a t e d protons, conforming the s t r u c t u r a l a s s i g n -- 17 -FIGURE IX - N.m.r. spectrum of 2 , 3 , 5 - t r i m e t h y l - f c - d i h y d r o -f u r a n (XXIX) - 18 -ment of - 2 , 3 , 5-trimethyl-& - d i h y d r o f u r a n (XXIX) . cis - 3-Methyl - 3-hexen - 2-one (XXX) and t r a n s - 3 - m e t h y l - 3 -hexen-2~one (XXXI) have been found to have b o i l i n g p o i n t s at 145-145 .5° and 156.5-158° r e s p e c t i v e l y . Rohrmann and Shoule (31) r e p o r t e d the s y n t h e s i s of 3-tnethyl-3~hexen-2-one and gave i t s b o i l i n g p o i n t v a l u e , 151°• I t i s p o s s i b l e t h a t t h e i r o^fi-u n s a t u r a t e d ketone was a mixture of the two p o s s i b l e geometric Isomers XXX and XXXI. The presence of carbon-carbon double-bond and o^fi-unsaturated c a r b o n y l f u n c t i o n were i n d i c a t e d by i n f r a r e d bands at 6.-18 M and 5 .91 Jd r e s p e c t i v e l y , f o r the c i s -3-methyl-3-hexen-2-one. (XXX) and at 6.07 M and 5.96 JX r e -s p e c t i v e l y , f o r the trans - 3-methyl - 3-hexen - 2-one (XXXI). The n.m.r. s p e c t r a of XXX and XXXI showed a b s o r p t i o n at 7.86 \"t ( s i n g l e t ) and 7.81 H ( s i n g l e t ) due to a c e t y l methyl hydrogens, at 8.12 X ( m u l t i p l e t ) and 8.39 Y ( m u l t i p l e t ) due to v i n y l methyl hydrogens and at 4.44 'i ( m u l t i p l e t ) and 3.52 •f ( m u l t i -p l e t ) due to v i n y l hydrogens, r e s p e c t i v e l y . The assignment of geometry to c i s and trans - 3-methyl - 3-hexen - 2«one (XXX and XXXI) were based on the lower f i e l d v i n y l p roton a b s o r p t i o n of the l a t t e r at 3 . 5 2 f than the former at 4.44 1\\ In XXXI the v i n y l hydrogen i s c i s to the a c e t y l group, whereas i n XXX, the v i n y l hydrogen Is t r a n s to the a c e t y l group. I n other words, the v i n y l hydrogen i n XXXI Is c l o s e r to the a c e t y l group than i n XXX, t h e r e f o r e the diamagnetic a n i s o t r o p y of the carbon-oxygen double-bond i n a c e t y l group would d e s h i e l d the v i n y l proton i n XXXI to a g r e a t e r extent t o g i v e a lower f i e l d a b s o r p t i o n - 19 -(32). T h i s s h i f t i n the v i n y l hydrogen r e g i o n has been observed i n many other c i s and t r a n s p a i r s of o l e f i n s (38). 1-Acetyl-c is - 1 , 2-dimet.hylcyclopropane (XXIV) and 1-a c e t y l - t r a n s - l , 2 - d i m e t h y l c y c l o p r o p a n e (XXV) showed no i n f r a -red a b s o r p t i o n bands a t t r i b u t a b l e t o carbon-carbon double-bond * but c a r b o n y l conjugated t o the cyclopropane r i n g (33) at 5.90>* f o r XXIV and 5.96 A f o r XXV > and i n a d d i t i o n , t h e r e was a band at 9.76 M f o r XXV due to a b s o r p t i o n of cyclopropane r i n g (3^0 . T h e i r n.m.r. s p e c t r a showed no s i g n a l due to proton attached to the carbon-carbon double-bond but h i g h f i e l d a b s o r p t i o n c h a r a c t e r i s t i c of cyclopropane r i n g p r o t o n s . These r i n g p r o -ton a b s o r p t i o n s appeared as two groups of s i g n a l s ; . c e n t e r e d at 8.68 f (two hydrogens) and 9.7^ 1* (one hydrogen) i n the case of l - a o e t y l - c i s - l , 2 - d i m e t h y l c y c l o p r o p a n e (XXIV) and i n the r e g i o n of 8.75 '£ to 9.06 TT7 i n the ease o f 1-acetyl-trans_-1 , 2-dimethylcyclopropane (XXV). These m u l t i p l e t s were p a r t l y obscured by a b s o r p t i o n of methyl groups. The s t e r e o c h e m i s t r y of XXIV and XXV were made by comparison of t h e i r n.m.r. sp e c t r a to those of the analogous carbomethoxy-cyclopropanes, namely l-carbomethoxy-cls_-l , 2-dimethylcyclopropane (X) and 1-carbomethoxy-trans-l , 2-dlmethylcyclopropane (XI) whose s t e r e o -chemistry has a l r e a d y been determined by van Auken and Rinehart (12) on the b a s i s of c o m p e t i t i v e s a p o n i f i c a t i o n s i n which the l e s s h i n d e r e d carbomethoxy group of X was consumed more r a p i d l y than t h a t of XI. - 20 -3-Methyl-4-hexen-2-one (XXXII) was e l u t e d at the same time as 1 - a c e t y l - t r a n s - 1 , 2 - d i m e t h y l c y c l o p r o p a n e (XXV) from the p r e p a r a t i v e vapor phase chromatography column. Attempts to separate t h i s ^ ^ - u n s a t u r a t e d ketone XXXII by u s i n g columns packed w i t h v a r i o u s substances were not s u c c e s s f u l . Bromina-t i o n o f the mixture c o n s i s t i n g 3-methyl-4~hexen-2-one (XXXII) and 1- a c e t y l - t r a j i s - 1 , 2 - d i m e t h y l c y e l o p r o p a n e (XXV) i n carbon t e t r a c h l o r i d e gave XXV and trans-3-methyl-3-hexen-2-one (XXXI) i n s t e a d of the dibromide of XXXII as i n d i c a t e d i n the pr e p a r a -t i v e vapor phase chromatogram. Since 3-methyl-4-hexen-2-one (XXXII) was s t a b l e at the temperature of the column, the con-v e r s i o n of XXXII or i t s dibromide to XXXI must have o c c u r r e d b e f o r e i t was i n j e c t e d i n t o the column. Although 3-methyl-4-hexen-2-one (XXXII) was not I s o l a t e d pure, I t s presence was i n d i c a t e d i n the n.m.r. spectrum of the mixture w i t h 1 - a c e t y l -t r a n s - l , 2 - d i m e t h y l c y c l o p r o p a n e (XXV). Those a b s o r p t i o n s a t t r i b -u t a b l e t o XXXII are shown below. I t was not p o s s i b l e to d i s -4.57 i ( m u l t i p l e t ) ^6.94 *f ( m u l t i p l e t ) CH 3CH^H-CH-COCH 3 ^ 7.97 Y ( s i n g l e t ) 8.32 r 3\"\"*\"—-—8.92 Y (doublet, Jc^7.0 c.p.s.) (doublet, J ~ 4 . 8 c.p.s.) XXXII t i n g u i s h whether the v i n y l hydrogens i n the molecule are c i s or t r a n s t o each o t h e r . Elemental m i c r o a n a l y s i s of the mixture c o n t a i n i n g 3-methyl-4-hexen-2-one (XXXII) and 1-acetyl-trans_-1,2-dimethylcyclopropane (XXV) was i n good agreement to the em-p i r i c a l formula C H 0, which i s common to both XXV and XXXII. - 21 -IV. DECOMPOSITION OF 3,3,5-TRISUBSTITUTED A 1-PYRAZOLINES P r e l i m i n a r y i n v e s t i g a t i o n s have -keen, shown t h a t the p y r o l y s i s of c i s and trans - 3 , 5-dimethyl - 3-carbomethoxy - A 1 -p y r a z o l i n e (XVI and XVII) a f f o r d s f i v e products ( F i g u r e V I, p. 13 )> namely, c i s and trans - 1 , 2-dlmethyl-l-carbomethoxy-cyclopropane (X and X I ) , methyl c i s and t r a n s - 2 - m e t h y l - 2 -pentenoate (XXVI and XXVII) and methyl 2-methyl - 3-pentenoate (XXVIII)I on p h o t o l y s i s , an a d d i t i o n a l peak, methyl methacry-l a t e (XXI), was found. S i m i l a r p y r o l y s i s r e a c t i o n s , as r e p o r t -ed i n t h i s work, were c a r r i e d out on 3 , 5 - d i m e t h y l - 3 - a c e t y l - A 1 -p y r a z o l i n e ( X X I I I ) , i t s c i s (XVIII) and t r a n s (XIX) isomers and found to g i v e s i x products ( F i g u r e V I I I , p. 15)° 1 - a c e t y l -c i s and t r a n s - 1 , 2 - d i m e t h y l c y c l o p r o p a n e (XXIV and XXV), 2 ,3 ,5-t r i m e t h y l - A 2 - d l h y d r o f u r a n (XXIX), c i s and t r a n s - 3 - m e t h y l - 3 -hexen-2-one (XXX and XXXI) and 3-methyl-4-hexen-2-one (XXXII). P h o t o l y s i s of these a c e t y l - p y r a z o l i n e s (XXIII, XVIII and XIX) gave no a d d i t i o n a l p r o d u c t . These r e s u l t s are t a b u l a t e d i n Tables I I and I I I . I t can be seen that the decomposition r e a c t i o n s of 3 ,5-d i m e t h y l - 3 - a c e t y l - A ^ \" - p y r a z o l i n e (XXIII), i t s c i s (XVIII) and t r a n s (XIX) isomers g i v e r e s u l t s t h a t resemble those of 3 ,5-d i m e t h y l - 3 - c a r b o m e t h o x y - A 1 - p y r a z o l i n e (XX), i t s c i s (XVI) and t r a n s (XVII) isomers r e s p e c t i v e l y . P y r o l y s i s gave h i g h e r r a t i o of o l e f i n s t o eyclopropanes than d i d p h o t o l y s i s . In the TABLE I I Product compositions f o r the decomposition of 3 > 5-dimethyl - 3-acetyl - A - p y r a z o l i n e s Sample Reaction c o n d i t i o n s Cyclopropane Unsaturated ketone Dihydro-c i s t r a n s cis-«k/S t r a n s - o ^ f uran XXIV XXV XXX XXXI XXXII XXIX XVIII ( c i s ) Vapor phase p y r o l y s i s at 125° 27 48 : 7 3 2 13 XIX (trans) Vapor phase p y r o l y s i s at 125° 67 19 2 7 2 3 XXIII (mixt.) L i q u i d phase p y r o l y s i s , 100° 36 18 15 18 4 9 XVIII ( c i s ) L i q u i d phase p y r o l y s i s , 100° 22 25 27 2 10 14 XIX (trans) L i q u i d phase p y r o l y s i s , 100° 62 17 1 17 3 0 XXIII (mixt.) Thermal p y r o l y s i s at 250° 48 32 5 , 3 3 9 XVIII ( c i s ) Thermal p y r o l y s i s at 250° 28 41 12 1 2 16 XIX (trans) Thermal p y r o l y s i s at 250° 60 27 1 6 3 .3 XXIII (mixt.) P h o t o l y s i s i n ether at 35° 39 4 2 4 6 3 6 XVIII ( c i s ) P h o t o l y s i s i n ether at 35° 59 28 .1 0 6 6 XIX (tr a n s ) P h o t o l y s i s i n ether at 35° 21 70 2 1 4 2 TABLE I I I Product compositions f o r the decomposition of 3 , 5-dimethyl - 3-carbomethoxy-& L-pyrazolines Reaction c o n d i t i o n s Cyclopropane Unsaturated e s t e r Methyl methacry-l a t e Sample c i s t r a n s cis -0^2 . trans- <*$ p»i X XI XXVI XXVII XXVIII XXI XX (mixt.) Vapor phase p y r o l y s i s (17) 53 42 3 2 1 0 XVI ( c i s ) Vapor phase p y r o l y s i s (17) 23 65 • 5 2 5 0 XVII (trans) Vapor phase p y r o l y s i s (17). 76 15 1 3 5 0 XX (mixt.) L i q u i d phase p y r o l y s i s (17) 45 27 10 15 3 0 XVI ( c i s ) L i q u i d phase p y r o l y s i s (17) 18 48 32 0 2 0 XVII (trans) L i q u i d phase p y r o l y s i s (17) 60 15 0 22 3 0 XVI ( c i s ) P h o t o l y s i s i n ether at 35° 6 l 23 6 2 2 6 XVII (trans) P h o t o l y s i s i n ether at 35° 22 65 0 5 2 6 _ 24 -o l e f i n f r a c t i o n of the products, c i s - 3 , 5 - d i m e t h y l - A - p y r a z o l i n e s gave predominantly the oG^-c i s - o l e f i n s and tra_ns_-3,5-dimethyl-^ - p y r a z o l i n e s gave predominantly the o ( , ^ - t r a n s - o l e f i n s . In the cyclopropane f r a c t i o n of the products, c i s and t r a n s - 3 , 5 - d i -methyl-A^-pyrazolines gave more t r a n s and c i s - l , 2 - d i m e t h y l -cyclopropane r e s p e c t i v e l y , whereas on p h o t o l y s i s , they were i n r e v e r s e d abundance. The o n l y s i g n i f i c a n t d i f f e r e n c e between the keto and e s t e r p y r a z o l i n e s was the d i h y d r o f u r a n product XXIX which was formed from the decomposition r e a c t i o n s of the keto pyrazo-l i n e s . I t i s noteworthy t h a t t h i s product was formed from o n l y one of the keto p y r a z o l i n e s , c i s - 3 , 5 - d i m e t h y l - 3 - a c e t y . l - A 1 -p y r a z o l i n e ( X V I I I ) , i n s i g n i f i c a n t amount. On the b a s i s of the p o s t u l a t e d p o l a r Intermediate In the p y r o l y s i s r e a c t i o n i t Is a n t i c i p a t e d t h a t the p o l a r i t y of the s o l v e n t might i n f l u e n c e the product r a t i o and the r a t e of r e -a c t i o n , hence p y r o l y s i s i n a number of s o l v e n t s w i t h d i e l e c t r i c c o n stants v a r y i n g from 2D f o r cyclohexane to 109D f o r form-amide have been c a r r i e d out on the c i s and trans_ - 3 , 5-dimethyl-3-carbomethoxy-A^-pyrazoline (XVI and X V I I ) . Samples of 0.2 ml. of the e s t e r p y r a z o l i n e i n 20 ml. of s o l v e n t i n a s e a l e d tube were heated f o r 90 minutes at . 1 2 5 ° . For low b o i l i n g s o l v e n t s , the s o l v e n t was removed by d i s t i l l a t i o n through a s p i n n i n g band Column under r e f l u x c o n d i t i o n , and the c o n c e n t r a t e d s o l u t i o n was analysed by a n a l y t i c a l vapor phase chromatography. For - 25 -formamide, the products were recovered from the s o l v e n t on a vacutam l i n e by pumping f o r two hours. These r e s u l t s (Table IV) showed a s m a l l and r e g u l a r i n f l u e n c e of the d i e l e c t r i c constant of the s o l v e n t on the product composition. In form-amide, up to 57$ of the product was o l e f i n s , whereas i n cyclohexane, on l y 7$ of the product was o l e f i n s . P h o t o l y s i s of c i s and trans - 3 j > 5~dlmethyl - 3-carbomethoxy-lt-pyrazoline (XVI and XVII) i n s o l v e n t s of v a r y i n g d i e l e c t r i c c onstants showed a s i m i l a r s o l v e n t e f f e c t on the product com-p o s i t i o n as i n the p y r o l y s i s r e a c t i o n s but In l e s s e r degree\" f o r example, i n formamide, up to 21$ of the product was o l e -f i n s whereas i n cyclohexane, i t was 5$. The ^.kinetic s o l v e n t e f f e c t has been examined f o r the p y r o l y s i s of 3 , 5-dImethyl - 3-carbomethoxy-fif'-pyrazoline (XX) i n v a r i o u s s o l v e n t s and i t was found t h a t the r a t e of p y r o l y s i s decreased i n the order of d i - n - b u t y l e t h e r , t e t r a l i n , n i t r o -benzene and formamide. The r a t e s i n these s o l v e n t s were a l l w i t h i n a f a c t o r of t h r e e ( F i g u r e s X I I -and—3EEB). L i q u i d phase p h o t o l y s i s of t r a n s - 3 , 5 - d i m e t h y l - 3 - c a r b o -m e t h o x y - A 1 - p y r a z o l i n e (XVII) has been c a r r i e d out i n s o l v e n t s such as 2 , 3-dimethylbutane and d i e t h y l e t h e r at v a r i o u s tem-pe r a t u r e s r a n g i n g from -55° t o 58° i n an attempt t o determine the temperature e f f e c t on p h o t o l y s i s of ^ - p y r a z o l i n e s . Pro-duct a n a l y s i s by a n a l y t i c a l vapor phase chromatography showed no a p p r e c i a b l e change a t t r i b u t a b l e to the i n f l u e n c e of tern-TABLE IV Product compositions f o r the sealed-tube p y r o l y s i s of c i s and t r a n s - 3 , 5 -d i m e t h y l - 3 - c a r b o m e t h o x y - ^ - p y r a z o l i n e i n v a r i o u s s o l v e n t s at 1 2 5 ° 1 = Solvent Cyclopropane Unsaturated e s t e r Sample c i s t r a n s c i s - f l ^ t r a n s - s ^ » fr& # Cyclohexane X XI XXVI XXVII XXVIII XVI ( c i s ) 2 . 0 7 D 2 5 6 2 1 2 0 1 XVI ( c i s ) Cyelohexane 2 . 0 7 D 3 0 5 5 1 1 3 1 XVI ( c i s ) E t h y l ether 4 . 3 4 D 2 5 5 6 1 6 2 1 XVI ( c i s ) Methanol 3 3 . 6 D 2 1 3 9 3 4 4 2 XVI ( c i s ) A c e t o n i t r i l e 3 7 . 5 D 2 1 42 3 1 4 2 XVI ( c i s ) Formamide 1 0 9 D 1 9 3 3 4 4 2 2 \" XVII (trans) # Cyclohexane 7 7^ 2 . 0 7 : D 7 0 2 3 1 5 1 XVII (trans) Cyclohexane 2 . 0 7 D 7 2 2 0 0 6 2 XVII (trans) E t h y l ether 4 . 3 4 D 6 6 1 8 0 1 3 3 XVII (trans) Methanol 3 3 . 6 D 48 6 0 4 4 2 XVII (trans) A c e t o n i t r i l e 3 7 . 5 D 6 7 6 0 2 5 2 XVII (trans) Formamide 1 0 9 D 3 1 1 2 0 5 2 5 # at 81°, not i n sealed-tube. TABLE V Product compositions of p h o t o l y s i s of c i s and t r a n s - 3 , 5 - d i -methyl - 3-carbomethoxy-^\"-pyrazoline Cyclopropane Unsaturated ester Methyl methacry-l a t e Sample Solvent and temperature c i s t r a n s els-^p trans-atyS ^ X XI XXVI XXVII XXVIII XXI XVII ( tr a n s ) 2 , 3-Dimethyl butane 58° 28 ' 63 3 4 2 0 XVII ( t r a n s ) E t h y l ether (26) 35° 22 65 0 5 2 6 XVII ( tr a n s ) E t h y l ether 0° 27 56 1 7 3 6 XVII ( tr a n s ) E t h y l ether -20° 25 55 1 8 3 8 XVII ( t r a n s ) E t h y l ether -55° 25 53 1 10 4 7 XVI ( c i s ) Cyclohexane^ 81° 43 45 7 0 1 4 XVII ( t r a n s ) Cyclohexane^ 81° 46 45 0 4 1 4 XVI ( c i s ) Formamide 23° 54 21 9 5 1 .10 XVII ( t r a n s ) Formamide 23° 15 58 2 16 3 6 # a t 81, py r o l y s i s a l s o occurred at a r a t e t h r e e times slower than -pyrolyoirj-. - 28 -p e r a t u r e . These r e s u l t s are shown i n Table V. P h o t o l y s i s and p y r o l y s i s gave the same pro d u c t s , t h e r e -f o r e they- might w e l l i n v o l v e the same i n t e r m e d i a t e . In order to determine whether the product composition was dependent on temperature or on the nature of the r e a c t i o n , p h o t o l y s i s and p y r o l y s i s of c i s and t r a n s - S ^ - d i m e t h y l - S - c a r b o m e t h o x y - A 1 -p y r a z o l i n e (XVI and XVII) were c a r r i e d out at the same tem-p e r a t u r e , 8l°, wi t h cyclohexane as s o l v e n t . I t was found the e v o l u t i o n of n i t r o g e n to be th r e e to f o u r times f a s t e r by p h o t o l y s i s than by p y r o l y s i s . The product compositions from these two r e a c t i o n s were not the same d e s p i t e the f a c t t h a t they were run under i d e n t i c a l c o n d i t i o n s . The r e s u l t s under these c o n d i t i o n s i n d i c a t e as i n other systems t h a t p h o t o l y s i s \\ g r e a t e r -y i e l d e d eyclopropanes w i t h h i g h degree of r e t e n t i o n of geome-t r y of the s t a r t i n g p y r a z o l i n e than those from p y r o l y s i s . I t was a l s o found t h a t the r a t i o of o l e f i n s to eyclopropanes from these r e a c t i o n s was lower f o r the p h o t o l y s i s than the p y r o l y s i s . A f u r t h e r t e s t of the e a r l i e r proposed mechanism was based on the f a c t t h a t t h e r e should be r o t a t i o n of the C^-Cjj bond i n the diazonium hfttaine i n t e r m e d i a t e XXXIV and t h a t i t would form 3 , 5-dimethyl - 3-carbomethoxy-A^-pyrazoline (XX) by c y c l i z a t i o n f a s t e r than l o s s of n i t r o g e n . L i q u i d phase p y r o l y s i s of trans - 3 , 5-dimethyl - 3-carbomethoxy-.A t 1-pyrazoline (XVII) at 90° was c a r r i e d to 50$ completion, and the recovered unreacted p y r a z o l i n e was analysed by n.m.r.' I t was found t h a t - 29 -COOCH- COOCH f c „ , • r < 3 / 3 ~ \\ Q H _ J J • eyclopropanes N 3 **\"* / \\ 3 —***• H 3 C * N N ^ H 3C and o l e f i n s XX XXXIV not more than 1% i s o m e r i z a t i o n of XVII to c i s - 3 , 5 - d i m e t h y l - 3 -A\" carbomethoxy-A- L-pyrazoline (XVI) had o c c u r r e d , (^similar r e s u l t was observed when tr£ns_ - 3 , 5-dimethyl - 3-carbomethoxy-A 1-p y r a z o l i n e (XVII) i n d i e t h y l e ther was p a r t i a l l y p h o t o l y s e d at 35°. - 30 -V. DISCUSSION The thermal p y r o l y s i s of c i s and trans_ - 3 , 4-dimethyl - 3 -carbomethoxy-A 1-pyrazollne (VI and VII) has been r e p o r t e d by Rinehart and van Auken (12) to proceed w i t h r a c e m i z a t i o n at C^ to g i v e cyclopropane products i n which the methyls are c i s and t r a n s w i t h that cyclopropane which r e t a i n s the geometry present i n the p y r a z o l i n e b e i ng s l i g h t l y predominant. For example, the c i s - p y r a z o l i n e VI g i v e s c i s - l , 2 - d i m e t h y l - l - c a r -bomethoxycyclopropane (X) and tr a n s - 1 , 2 - d i m e t h y l - 1 - c a r b o -methoxycyclopropane (XI) i n the r a t i o of 1.00*0.70 whereas the trans-pyrazo 1ine V I I g i v e s X and XI i n the r a t i o of 1.00*1.22. Rinehart and van Auken suggested t h a t r o t a t i o n COOCH, 3 VI A. „ C 0 0 C H o Ho0. £ 0 0 C H o H 3Q ^OOCH^ H 3 C _ \\/ ^ 3 * \\ / N\"IL ~r*0H X XI : V I I about the O^-C^ bond i n the dlazonium bsfcaine i n t e r m e d i a t e V I I I accounts f o r the l o s s of geometric i n t e g r i t y and th a t H 3C £ 0 0 C H < ^ H 3 Ng V I I I - 31 the l o s s of n i t r o g e n Is o n l y s l i g h t l y slower than r o t a t i o n to g i v e a h i g h e r y i e l d of the cyclopropane which r e t a i n s the ge-ometry present In the p y r a z o l i n e . In the present work, i t was found t h a t the thermal p y r o l y s i s of c i s and trans - 3 , 5-dlmethyl - 3 - c a r b o m e t h o 3 c y-A 1-p y r a z o l i n e (XVI and X V I I ) , c i s and t r a n s - 3 , 5 - d i m e t h y l - 3 -acetyl-A - p y r a z o l i n e (XVIII and XIX) a l s o proceeds w i t h r a c e m i z a t i o n at to g i v e cyclopropane products i n which the methyls are c i s and t r a n s but the cyclopropane w i t h i n v e r -s i o n of the geometry present i n the p y r a z o l i n e was found p r e -dominant. For example, the r a t i o of c i s and t r a n s - l , 2 - d i -m e t h y l - l - a c e t y l c y c l o p r o p a n e (XXIV and XXV) from the thermal p y r o l y s i s of XVIII and XIX were 22*25 and 62*17 r e s p e c t i v e l y . ^ £ O C H 3 n/V XIX A second important f e a t u r e of the present work i s t h a t the f o r m a t i o n of o l e f i n s from the p y r o l y s i s of 3 * 5-dimethyl-A 1 - p y r a z o l i n e s - i s h i g h l y s t e r e o s p e c i f i c . The r a t i o of c i s and trans - 3-methyl - 3-hexen - 2-one (XXX and XXXI) from the p y r o l y s i s 32 -of c i s and t r a n s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - / ^ - p y r a z o l i n e (XVIII and XIX) were 27»2 and 1*17 r e s p e c t i v e l y . T h i s s t e r e o s p e c i -f i c i t y has not b e e n observed p r e v i o u s l y s i n c e a n a p p r o p r i a t e C O C H , H. XVIII £OGrL H CH ^ / 3 c=c CH CH NCOCH 3 2 3 XXX (27fo) CH CH CH 3 \\2 / 3 A .c=cf CH 3CH 2 ^ H 3 c=c H / XCOCH, XXXI (2%) H C CH 3CH 2 \\ COCH, XIX XXXI (17$) XXX (Ifo) model has not been a v a i l a b l e . The form a t i o n of o l e f i n s has p r e v i o u s l y been thought t o be formed through the i n t e r m e d i a t e H 3C COGCH, C H , 2 XXXIV H CH-, CH0CH_. \\ / 3 3 \\2 C=C / \\ CH 3CH 2 COGCH 3 H CH 0 / 3 \\ COOCH, XXVI XXVII XXXIV or XXXV i n which r o t a t i o n around the s i n g l e bonds would g i v e a mixture of c i s and t r a n s o l e f i n s . For the dlazonium' bjafcalne XXXIV to g i v e such s t e r i c c o n t r o l i t would r e q u i r e t h a t the anion c e n t e r must r e t a i n i t s asymmetry. T h i s Is not a n t i c i p a t e d on the b a s i s of s t u d i e s by Cram and coworkers (39). In the p y r o l y s i s and p h o t o l y s i s of 3 J , 5-dimethyl -3 -- 33 -a c e t y l - A 1 - p y r a z o l i n e ( X X I I I ) , i t s c i s (XVIII) and t r a n s (XIX) isomers, an a d d i t i o n a l product 2 , 3 , 5 ~ t r i m e t h y l - A 2 - d i h y d r o f u r a n (XXIX) was o b t a i n e d . T h i s can be formed through the diazonium b c t a i n e i n t e r m e d i a t e (XXXV) which has a. resonance form of XXXVI. Again f r e e r o t a t i o n around C^-C^ bond p r e d i c t s t h a t ,COCH XXXV XXXVI XXIX c i s and t r a n s - 3 , 5 - d i m e t h y l - 3 - a c e t y l ~ A - p y r a z o l i n e (XVIII and XIX) would g i v e the same i n t e r m e d i a t e XXXVI on p y r o l y s i s , and hence they should g i v e the same amount of d i h y d r o f u r a n XXIX. Experimental r e s u l t s , however, showed the amount of XXIX ob-t a i n e d from the i s o m e r i c p y r a z o l i n e s were s i g n i f i c a n t l y d i f -f e r e n t . F o r example, thermal p y r o l y s i s of c i s and t r a n s - 3 , 5 -d i m e t h y l - 3 - a c e t y l - A 1 \" - p y r a z o l i n e (XVIII and XIX) at the i n -j e c t o r of the vapor phase chromatography instrument gave 16$ and 3$, r e s p e c t i v e l y , of 2 , 3 , 5 - t r i m e t h y l - A - d i h y d r o f u r a n (XXIX), and p y r o l y s i s of neat l i q u i d samples gave 14$ and 0% r e s p e c t i v e l y . These r e s u l t s seem to i n d i c a t e t h a t the forma-t i o n of the d i h y d r o f u r a n was predetermined by the molecular s t r u c t u r e of the p y r a z o l i n e s . In f a c t , the s t e r i c i n t e r a c t i o n of and methyl groups i n c i s - S ^ - d i m e t h y l - S - a c e t y l - A 1 -p y r a z o l i n e (XVIII) might be expected to f o r c e the a c e t y l group i n t o a f a v o r a b l e p o s i t i o n f o r d i h y d r o f u r a n f o r m a t i o n . - 34 -I t i s a n t i c i p a t e d t h a t the f o r m a t i o n of an i o n i c dlazonium b a t a i n e i n t e r m e d i a t e l i k e I I from A ^ - p y r a z o l i n e s ( I I I ) would cause the k i n e t i c s of the r e a c t i o n to show a h i g h -er r a t e i n more p o l a r s o l v e n t s , s i n c e the process i n v o l v e s the 3> -N R2 Y Y= -COCH3, -COOCHo 2 I I f o r m a t i o n of i o n i c charges from a n e u t r a l s p e c i e s (37). In o t h e r woYds, the r a t e of p y r o l y s i s of A ^ - p y r a z o l i n e s should be f a s t e r i n a s o l v e n t of h i g h p o l a r i t y than a s o l v e n t of low p o l a r i t y . The r e s u l t s of the present work showed the r a t e of p y r o l y s i s of A ^ - p y r a z o l i n e s , as i n d i c a t e d by the r a t e of n i t r o -gen e v o l u t i o n , to be f a s t e r i n non-polar s o l v e n t s , such as d i -n - b u t y l e t h e r or t e t r a l i n than i n p o l a r s o l v e n t s , such as nitrobenzene or formamide by the s m a l l f a c t o r of t h r e e . T h i s o p p o s i t e k i n e t i c e f f e c t i n d i c a t e s t h a t the i n t e r m e d i a t e i n p y r o l y s i s has l e s s I o n i c c h a r a c t e r than the s t a r t i n g m a t e r i a l , the A 1 - P y r a z o l i n e . T h e r e f o r e , i t i s not l i k e l y t h a t the therm-a l p y r o l y s i s of A ^ - p y r a z o l i n e s proceeds through an i o n i c mecha-nism w i t h the dlazonium b u t a i n e I I as the t r a n s i t i o n s t a t e . The s m a l l d i f f e r e n c e i n r a t e of p y r o l y s i s i n p o l a r and non-p o l a r s o l v e n t s suggests the mechanism of the p y r o l y s i s of A 1 -p y r a z o l l n e s to be e i t h e r f r e e r a d i c a l or molecular s i n c e these do not Involve l a r g e i o n i c c h a r a c t e r . - 35 -One f u r t h e r argument can be made a g a i n s t the proposed i o n i c mechanisms f o r thermal p y r o l y s i s . T h i s mechanism would p r e d i c t t hat the diazonium b e t a i n e i n t e r m e d i a t e , f o r example XXXIV, would form p y r a z o l i n e by r i n g c l o s u r e f a s t e r than the l o s s of n i t r o g e n . Since the product a n a l y s i s p r e d i c t s r o t a t i o n ' C O O C H -N?H3 H3C N 2 XXXIV about Cg-G^ bond, one would a n t i c i p a t e t h a t when t r a n s - 3 , 5 -dimethyl - 3-carbomethoxy-^\"-pyrazoline (XVII) i s p a r t i a l l y p y r o l y s e d , the recovered sample should show both XVII and I t s c i s isomer XVI. T h i s has not been found to occur i n t h i s work o r i n the work of van Auken and RInehart (12). P a r t i a l photo-l y s i s of XVII a l s o gave a s i m i l a r r e s u l t . The p o s s i b i l i t y of the diazonium b n t a i n e I I as the i n t e r m e d i a t e f o r the p y r o l y s i s of ^ - p y r a z o l i n e s i s t h e r e f o r e e l i m i n a t e d . R1. ^ R 2 y R H \" \" N 2 I I Y = - C O C H 3 , - C O O C H o Recent work In t h i s l a b o r a t o r y (4o) has d i s c o v e r e d a CMT€-p y r a z o l i n e system which g i v e s k i n e t i c s t h a t i s - s e n s i t i v e to - 36 -s o l v e n t p o l a r i t y as expected f o r an i o n i c Intermediate. The O C O O C H , K /—* C00CH o other minor | | N C N W 3 4 . \\ ^ N — 7 C N p r o d u c t s . XXXVII XXXVIII A 1 - p y r a z o l i n e XXXVII In t h i s case has two e l e c t r o n withdrawing groups which can s t a b i l i z e d a dlazonium b ^ t a i n e i n t e r m e d i a t e to a g r e a t e r degree. I t i s apparent that p y r o l y s i s of ^ \" - p y r a z o l i n e s might f i t a spectrum of c o n d i t i o n s i r i which symmetric s u b s t i t u t i o n around the azo group leads to b r e a k i n g of both bonds s i m u l -t a n e o u s l y i n the t r a n s i t i o n s t a t e . In h i g h l y unsymmetrical / ^ - p y r a z o l i n e s l i k e XXXVII one bond breaks b e f o r e the o t h e r . Such a s i t u a t i o n has been shown to be the case f o r l i n e a r azo compounds ( 4 l ) where compounds XXXIX, XL,and,XLI (0=--C^B.^) H Q C C H - H o C , C H o H C 3 \\ / 3 3 v / 3 3 \\ C H - N = N - C H C H - N = N - C H J ! H - N = N - C H , 0 0 0 C H 3 0 XXXIX XL XLI show equal b r e a k i n g of both bonds, unequal b r e a k i n g of both bonds and i n i t i a l b r e a k i n g of one bond. These r e s u l t s were obtained by secondary deuterium e f f e c t s on the k i n e t i c s . I t i s apparent t h a t i n the p y r o l y s i s of c i s and t r a n s -3,5-dimethyl-3-carbomethoxy-A 1-pyi ,azolIne (XVI and XVII) we have an Intermediate s i t u a t i o n where the C - N bonds are break-- 37 -i n g i n the t r a n s i t i o n s t a t e p o s s i b l y to d i f f e r e n t degrees and s u f f i c i e n t p o l a r i t y developes i n the molecule a f t e r the t r a n -s i t i o n s t a t e to make the products s e n s i t i v e to the s o l v e n t used. Such a model c o r r e c t l y p r e d i c t s the o l e f i n r e a i f i o ' n 1 ^ ^ P h o t o l y s i s o f c i s and trans - 3 , . 4-dlmethyl - 3-earbomethoxy-^ - p y r a z o l i n e (VI and VII) have been r e p o r t e d by van Auken and Rineh a r t ( 12 ) to gi v e s t e r e o s p e c i f I c a l l y c i s and t r a n s _ - l , 2 - d i -methyl-l-carbomethoxycyclopropane (X and XI) r e s p e c t i v e l y , the major s i d e products are methyl t i g l a t e (IV) and methyl an-g e l a t e (V) r e s p e c t i v e l y . /COOCH^ ... - H COOCH ^ \\ fC * k X O O C H o \\ / KJ1 K3 w ^ 3 C ^ \" ^\"01 JC0GH, 3 XVIII xxiv (59$) XXV (28$) xP0CH3 H 3 C ^ ' N ^ N ^ H 3 . H 3 ^ ^ H 3 XIX XXV (70) XXIV (21$) product composition as observed i n the p y r o l y s i s was a l s o ob-served i n the p h o t o l y s i s . The two r e a c t i o n s t h e r e f o r e are c l o s e l y r e l a t e d but not I d e n t i c a l as shown by p h o t o l y s i s and p y r o l y s i s at same temperature and s o l v e n t In which d i f f e r e n t product compositions r e s u l t e d . ' I t i s p o s s i b l e the p h o t o l y s i s i n v o l v e s a d i f f e r e n t con- . f o r m a t i o n of the same Intermediate as the p y r o l y s i s w i t h v a r i a t i o n e i t h e r due to a d i f f e r e n t amount of a v a i l a b l e energy or due to induced s t r u c t u r a l f e a t u r e s from the p r i o r e l e c -t r o n i c a l l y e x c i t e d I ntermediate. The n u c l e a r magnetic r e s o -nance s p e c t r a (Table I) of the A ^ - p y r a z o l i n e s showed l a r g e d i f f e r e n c e s i n the chemical s h i f t p o s i t i o n s of the hydrogens on C / | , e s p e c i a l l y i n c i s - 3 , 5 - d i m e t h y l - 3 - a c e t y l - A * ' - p y r a z o l i n e _ 40 -(XVIII), and cis - 3 , 5-dlmethyl - 3-earbomethoxy-A - p y r a z o l i n e ' (XVI) . For example, hydrogens i n XVIII absorbed at 7.57 tf and 9.30-f, those of XVI absorbed at 7.68 • tf' and 9.14 com-pared to 8.28 'i and 8.56 tf f o r the t r a n s - e s t e r - p y r a z o l i n e (XVII) and 8.53 tf1 f o r the t r a n s - k e t o - p y r a z o l i n e (XIX). These d i f f e r e n c e s i n chemical s h i f t s c o u l d w e l l be r e l a t e d to d i f -f e r e n c e s i n conformation i n these s p e e i e s . I f t h i s i s so then i t Is obvious t h a t the molecules i n some cases are e n t e r i n g r e a c t i o n w i t h c o n s i d e r a b l e d i f f e r e n c e s i n t h e i r geometry. -.41 -V I . EXPERIMENTAL V I - 1 . General statement M e l t i n g p o i n t s and b o i l i n g p o i n t s are u n c o r r e c t e d . M e l t -i n g p o i n t s were determined by a mi c r o s c o p i c m e l t i n g p o i n t ap-paratus ( R e i c h a r t , A u s t r i a ) and most b o i l i n g p o i n t s were de-termined by the micro i n v e r t e d c a p i l l a r y method. I n f r a r e d s p e c t r a were measured wi t h a Perkin-Elmer Model 137 spectrophotometer f i t t e d w i t h sodium c h l o r i d e o p t i c s . N u c l e a r magnetic resonance s p e c t r a were recorded on a V a r i a n A s s o c i a t e s Model A-60 spectrophotometer by Mrs. E. B r i o n and Mr. P. Horn. T e t r a m e t h y l s i l a n e was used as I n t e r n a l standard. The vapor phase chromatography u n i t s used were an Aero-graph Model A-90-P ( p r e p a r a t i v e s c a l e ) and a Perkin-Elmer Model 226 ( a n a l y t i c a l s c a l e ) . The elemental microanalyses were performed by Dr. A. Bern-hardt of Germany and by Mrs. A. A l d r i d g e and Mrs. C. J e n k i n s . V I - 2 . N - N i t r o s o - N - e t h y l urea The method f o r the p r e p a r a t i o n of N-nitroso-N-methyl urea (35) was adapted w i t h some m o d i f i c a t i o n . Three hundred grams (5 moles) of urea was d i s s o l v e d i n a s o l u t i o n of 123 g. (1.5 moles) of ethylamine h y d r o c h l o r i d e , 300 ml. of water and a few drops of - 42 -c o n c e n t r a t e d h y d r o c h l o r i c a c i d . The mixture was b o i l e d g e n t l y under r e f l u x f o r t h r e e hours a n d , v i g o r o u s l y f o r a q u a r t e r hour. A f t e r c o o l i n g to room temperature, 110 g. (1.5 moles) of 98 per cent sodium n i t r i t e was added and the mixture was d i v i d e d i n t o s i x equal p o r t i o n s . Each p o r t i o n was c h i l l e d w i t h i c e and added to an i c e - c o l d s o l u t i o n of 17 g. (0.17 mole) of concentrated s u l f u r i c a c i d i n 110 g. of i c e w i t h s t i r r i n g at such a r a t e t h a t the temperature remained below 5 ° . The N-n i t r o s o - N - e t h y l urea, which rose to the s u r f a c e as pale yellow c r y s t a l s , was c o l l e c t e d on a f i l t e r and washed wi t h l e e - c o l d water and d r i e d by s u c t i o n t i l l constant weight (approximately t h r e e h o u r s ) . The y i e l d was 87 g. (0.75 mole) or 50 per cent of the t h e o r e t i c a l y i e l d . V I - 3 . Diazoethane F i f t y grams (O.285 mole) of N - n i t r o s o - N - e t h y l urea was added to v i g o r o u s l y s t i r r e d i c e - c o l d s o l u t i o n of 300 ml. of anhydrous ether-methanol ( 5 : l ) and 125 ml. of 40$ potassium hydroxide a t such a r a t e t h a t the r e a c t i o n was under c o n t r o l and the r e a c t i o n temperature remained below 5°» The orange c o l o r e d diazoethane-ether-methanol s o l u t i o n was decanted from the aqueous l a y e r , washed w i t h 100 ml. of i c e - c o l d water and d r i e d w i t h anhydrous potassium hydroxide p e l l e t s f o r two hours. The y i e l d was approximately 35-40 per cent as estimated by the r e a c t i o n s w i t h methyl i s o p r o p e n y l ketone and methyl met h a c r y l a t e . - 43 -VI-4. Methyl i s o p r o p e n y l ketone A commercial sample (K and K Laboratory, P l a i n s v i l l e , N.Y.) was p u r i f i e d by mixing w i t h an equal volume of anhydrous e t h y l e t h e r w i t h s t i r r i n g . A polymer r e s i d u e p r e c i p i t a t e d i n s t a n t l y and was f i l t e r e d w i t h f l u t t e d f i l t e r paper. The f i l -t r a t e was d i s t i l l e d at atmospheric pressure and the f r a c t i o n w i t h a b o i l i n g p o i n t of 9 5 ± 2 ° was c o l l e c t e d and used immedi-a t e l y . V I - 5 . S ^ - D i m e t h y l - S - a c e t y l - A 1 - p y r a z o l i n e (XXIII) To an i c e - c o l d diazoethane-ether-methanol s o l u t i o n was added the f r e s h l y d i s t i l l e d methyl i s o p r o p e n y l ketone s l o w l y w i t h s t i r r i n g u n t i l the orange c o l o r d i s a ppeared. The s o l v e n t mixture was removed by a f l a s h evaporator at water a s p i r a t o r p ressure and the r e s i d u e d i s t i l l e d to g i v e a c o l o r l e s s l i q u i d , b.p. 56-57°/1.2 mm. (50 per cent based on the q u a n t i t y of methyl Isopropenyl ketone used). A n a l . C a l c d . f o r C 7 H 1 2 N 2 ° 5 °> 59.97\" H, 8.63; N, 19.99-Found: C, 59.60° H, 8.22* N, 20 .27 . The n.m.r. spectrum (20$ v/v i n CCl^) showed i t to be a mixture of 40$ c i s and 60$ t r a n s isomers (see below) as e s t i -mated by the i n t e g r a l s o f the a c e t y l methyl hydrogens of the two isomers. - 44 -V I - 6 . S e p a r a t i o n of c i s and t r a n s - 3 , 5 - d l m e t h y l - 3 - a c e t y l - A -p y r a z o l i n e (XVIII and XIX) The 3 > 5-dimethyl - 3-acetyl-A 1-pyrazoline (XXIII) was f r a c t i o n a l l y d i s t i l l e d u s i n g a Nester and Faust 1 8-inch by 6-mm. spinning-band s t i l l at 0.2 to 0.3 mm. w i t h the s t i l l pot immersed i n o i l bath maintained between 65-70°. During the en-t i r e d i s t i l l a t i o n , the vapor came over at 32-35°/0.2-0.3 mm. The n.m.r. analyses of the lower and h i g h e r b o i l i n g f r a c t i o n s showed they c o n t a i n e d 8 l $ c i s - p y r a z o l i n e XVIII and 87$ t r a n s -p y r a z o l i n e XIX r e s p e c t i v e l y . These analyses were based on the i n t e g r a l s o f the a c e t y l methyl hydrogens a b s o r p t i o n s at 'J.fQ't f o r the e l s Isomer and at 7.65 <- (s) and 6.l8yU (w) a t t r i b u t a b l e to the o(,/£-unsaturated earbonyl and carbon-carbon double-bond s t r e t c h i n g r e s p e c t i v e l y . The n.m.r. spectrum (10$ v/v i n CCl^) showed peaks of a c e t y l methyl hydrogens at 7.86 tf ( s i n g l e t ) , v i n y l methyl hydrogens at 8.12 tf ( m u l t i p l e t ) , methylene hydrogens at 7.73 tf ( m u l t i p l e t ) , a l k y l methyl hydrogens at 9.02'tf ( t r i p l e t w i t h J ^7.3 c.p.s.) and v i n y l hydrogen at 4.44 tf ( m u l t i p l e t ) . Geometric assignment i s d i s c u s s e d below. A n a l . C a l c d . f o r C ^ H ^ O : C, 74.95° H, 10.78. Founds C, 75.021 H, 10 .77 . - 48 -trans-3-Methyl-3-hexen-2-one; (XXXI): b.p. 156.5-158°, n 2' 3 1.4481, 17.7 minutes and 7$. I n f r a r e d spectrum (5$ v/v i n CCl^) showed a b s o r p t i o n s at 5.96 A (s) and 6.07 (w) due to ^ ^ - u n -s a t u r a t e d c a r b o n y l and carbon-carbon double-bond s t r e t c h i n g r e -s p e c t i v e l y . The n.m.r. spectrum (10$ v/v i n CCl^) showed peaks of a c e t y l methyl hydrogens at 7.81 1* ( s i n g l e t ) , a l k y l methyl hydrogens at 8.93 ^ ( t r i p l e t w i t h J<*7.5 c . p . s . ) , v i n y l methyl hydrogens at 8.39 'c ( m u l t l p l e t ) , methylene hydrogens at 7.76't ( m u l t i p l e t ) and v i n y l hydrogen at 3.52 ^ ( m u l t l p l e t ) . The geometric assignments f o r the c i s and trans-3-methyl-3-hexen-2-one (XXX and XXXI) were based on the lower chemical s h i f t of the v i n y l proton i n XXXI. Since i n XXXI, the v i n y l proton Is c i s to the c a r b o n y l and hence c l o s e r t o the diamagnet-i c a n i s o t r o p y of the carbon-oxygen double-bond which d e s h i e l d s the v i n y l proton t o a g r e a t e r extent t o g i v e a low 85, 14 (1963)' A b s t r a c t , l 4 6 t h Meeting of t h e T m e r i e a n ChemicalHSociety, January, 1964,. p. 4C. 42. T. L. Jacobs In R. E l d e r f l e l d ed., \" H e t e r o c y c l i c Compounds\", V o l . 5, John Wiley and Sons, I n c . , New York, 1957, p. 63. 43. R. Locquin and R. Heilmann, Compt. rend., 186, 705 (1928). 44. J . Hine, \" P h y s i c a l Organic Chemistry\", McGraw-Hill Co., Inc., New York, 1956, p. 43 taken from A. A. Margott and E. R. Smith, Table of D i e l e c t r i c Constants of pure l i q u i d , N a t l . Bur. Standards C i r . 514, 1951. 45. H. R. Synder, J r . , Ph.D. D i s s e r t a t i o n , Boston Univ., 1958. "@en ; edm:hasType "Thesis/Dissertation"@en ; edm:isShownAt "10.14288/1.0062212"@en ; dcterms:language "eng"@en ; ns0:degreeDiscipline "Chemistry"@en ; edm:provider "Vancouver : University of British Columbia Library"@en ; dcterms:publisher "University of British Columbia"@en ; dcterms:rights "For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use."@en ; ns0:scholarLevel "Graduate"@en ; dcterms:title "Pyrolysis and photolysis of cis and trans-3, 5-dimethyl-3-acetyl-delta1-pyrazoline and cis and trans-3,5-dimethyl-3-carbomethoxy-delta1-pyrazoline."@en ; dcterms:type "Text"@en ; ns0:identifierURI "http://hdl.handle.net/2429/37597"@en .