1,3-Dipolar cycloaddition reactions of 3-acylimino-1-methylbenzimidazolium betaines

3-Acylimino-1-methylbenzimidazolium betaines undergo 1,3-dipolar cycloaddition reactions with activated alkenes (methyl acrylate, acrylonitrile, and fumaronitrile) and methyl propiolate to produce 2-substituted 1-methylbenzimidazoles. The transformation involves the initial formation of a 1,3-dipolar cycloadduct followed by the N? N bond cleavage. The primary adducts can be isolated from the reaction with methyl acrylate and acrylonitrile.