Synthesis of benzimidazolequinone analogue of cyclopropamitosene antitumor agents

The preparation of a pyrrolo[1,2-a]benzimidazole, pyrido[1,2-a] benzimidazole and pyrrolo[1,2-a]benzimidazolequinone containing a fused cyclopropane ring is reported. Their synthesis involved the thermolysis of the respective benzimidazole-2-Eschenmoser hydrazones (aziridinyl imines), which facilitated an intramolecular 1,3-dipolar cycloaddition. X-ray crystal structure of one [3+2] pyrazoline-cycloadduct is presented. The redox potential of -1.052 V (vs. ferrocene) for the cyclopropapyrrolo[1,2-o]benzimidazolequinone was determined by cyclic voltammetry indicating single-electron reduction occurs more easily than mitomycin C or the cyclopropamitosenes.