Addition reactions of heterocyclic compounds. Part XXVI. Dimethyl acetylenedicarboxylate with imidazoles and benzimidazoles

Abstract

Methyl acetylenedicarboxylate with 2- and 4-methylimidazole gave 2- and 4-methyl-1-(1,2-dimethoxycarbonyl-vinyl)imidazoles. The major products from 1,2-dimethyl- and 1-ethyl-2-methyl-benzimidazoles were azepino-[1,2-a]benzimidazoles, but 2-ethyl-1-methyl- and 1-methyl-benzimidazole gave pyrido[1,2-a]benzimidazoles. Benzimidazole gave, according to the conditions, two 2,3-dihydro-1,3-di-(1,2-dimethoxycarbonylvinyl)-2-methoxybenzimidazoles, a pyrido[1,2-a]benzimidazole, or dimethyl αβ-dibenzimidazol-1-ylsuccinate.