An efficient one-pot synthesis of thiophene-fused pyrido[3,2-a]azulenes via Gewald reaction

A simple and efficient procedure was developed for the synthesis of 11H(2H)-4-oxothiophene[3',4':6,5]pyrido[3,2-a]azulene-10-carboxylates(3) in moderate to good yields via the Gewald reaction of ethyl 1-cyanoacetyl-2-methoxyazulene-3-carboxylate(1) with carbonyl compounds(2) and elemental sulfur utilizing imidazole as catalyst.This reaction provides a new procedure for synthesis of pyridinone-fused azulenes.