Facile one-pot syntheses of new polyfunctional pyrazolyl substituted and pyrazolofused pyridines

摘要

Ethyl 2-cyano-3-(5-chloro-1,3-diphenylpyrazol-4-yl)acrylate (1) undergoes both conjugate addition of a number of methylene-active ethanenitriles and direct addition of other active methylene donors to the cyano carbon atom. These additions are the starting events of cascades of subsequent reactions eventually forming (i) novel polyfunctional pyrazolyl-substituted monocyclic pyridines (4a, b and 6), (ii) 1,3-benzothiazole and benzimidazole-fused pyridines (11, 13) and (iii) pyrazolo[5,4-b]pyridines (19b, 20) in one-pot reactions in ethanolic solution containing catalytic amounts of piperidine. [References: 14]