Cross condensation reactions of ethyl cyanoacetate with some keto methylene compounds: Diastereoselective synthesis of Z-2-( cyanoethoxycarbonyl)methylene-1,2- dihydropyridine and Z-2-(cyanoethoxycarbonyl)methylene-2H-pyran derivatives
| Main Authors: | Sunil K. Talapatra, Kabita Mandal, Kallolmay Biswas, Sudipta Mandai, Bani Talapatra |
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| Format: | Article Journal |
| Bahasa: | eng |
| Terbitan: |
, 1999
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| Subjects: | |
| Online Access: |
https://zenodo.org/record/5867036 |
Daftar Isi:
- Centre of Advanced Studies on Natural Products, Department of Chemistry, University College of Science, University of Calcutta, Calcutta-700 009. India Manuscript received 14 October 1999 Previously reported ethyl α:,ԑ-dicyano-β,δ-dimethyl-∆β,δ_hexadienoate (2) structure for the minor product of the diethylamine catalyzed condensation reaction between ethyl cyanoacetate and acetylacetone has now been revised as 4,6-dimethyi-Z-2- (cyanoethoxycarbonyl)methylene-1,2-dihydropyridine (3) based on its 1H NMR, 13C NMR and mass spectral analyses. The formation of the major product 3-carbocthoxy-4,6-dimethyl-2H-pyridone (1), and of 3 from 1 has been rationalized. The exocyclic substituted methylene moiety has been shown to have Z configuration, based on diastereomeric transition states as predicted mechanistically. However, 3 has been isolated as the sole product of the above condensation when mediated by K2CO3• Similarly, K2CO3 mediated condensation of ethyl cyanoacetate with ethyl acetoacetate gives 3-cyano-4-hydroxy-6- methyi-Z-2-(cyanocthoxycarbonyl)methylene-2H-pyran (4) and that with 2-hydroxy-4,6-dimethylacetophenone affords 3-cyano-4,5, 7 -trim ethylcou mario (5) and 4,5, 7-trimethyi-Z-2-( cyanoethoxycarbonyl)methylenebenzo[b]-2H-py ran (6). Diastereoselective formation of the Z isomers 4 and 6 has been accounted for in terms of the diastereomeric transition states of the reactions.