N-(Thieno[2,3-b]pyridin-3-yl)cyanoacetamides: synthesis and cyclizations

Abstract

A series of N-(thieno[2,3-b]pyridin-3-yl)cyanoacetamides were prepared by reaction of 3aminothieno[2,3-b]pyridines with 1-cyanoacetyl-3,5-dimethytlpyrazole. Upon treatment with alkali, N-(2-alkoxycarbonylthieno[2,3-b]pyridin-3-yl)cyanoacetamides undergo Camps-type cyclization to give dipyridothiophenes. The relative stability of their tautomers was estimated by quantum chemical calculations. In contrast, cyclization of 3-(2-cyanoacetamido)thieno[2,3b]pyridine-2-carboxamides lead to the formation of pyrido[3',2':4,5]thieno[3,2-d]pyrimidines.