A cyclopropane ring has been fused onto tetrahydropyrrolo- and tetrahydropyrido-[1,2-a]-benzimidazoles and -benzimidazolequinones via the cycloaddition of diazomethines generated from the thermolysis of N-(allyl and but-3-enyl)benzimidazole-2-Eschenmoser hydrazones (aziridinyl imines). At lower temperatures, the 1,3-dipolar [3 + 2] cycloadduct was obtained for only the N-allylbenzimidazole-2-Eschenmoser hydrazones.
benzimidazoles - bioreductive - diazo-compounds - heterocycles - hydrazones