Some novel heterocyclic systems derived from 7‐amino‐2,3‐dihydro‐8‐nitro‐1 H ‐pyrrolo[1,2‐α]benzimidazole and the corresponding diamine

The preparation of 7‐amino‐2,3‐dihydro‐8‐nitro‐1 H ‐pyrrolo[1,2‐ a ]benzimidazole from 1,4‐diacetamido‐2,3‐dinitrobenzene is described. Reaction of this compound with 2,5‐dimethoxytetrahydrofuran produces 2,3‐dihydro‐8‐nitro‐7‐ N ‐pyrrolo‐1 H ‐pyrrolo[1,2‐ a ]benzimidazole, which can be cyclised to produce two new heterocyclic ring systems, 9,10‐dihydro‐8 H ‐pyrrolo[1,2‐ a ]pyrrolo(1′,2′:1,2]imidazo[5,4‐ f ]quinoxaline and 9,10‐dihydro‐8 H ‐pyrrolo[2,1‐ c ]pyrrolo[1′,2′:1,2]imidazo[4,5‐ h ][1,2,4]benzotriazine. The corresponding diamine, 7,8‐diamino‐2,3‐dihydro‐1 H ‐pyrrolo[1,2‐ a ]benzimidazole undergoes a variety of condensation reactions to produce several new heterocyclic systems, for example, with formic acid, 1,7,8,9‐tetrahydroimidazo‐[4,5‐ e ]pyrrolo[2,1‐6]benzimidazole is formed and with diacetyl, 9,10‐dihydro‐2,3‐dimethyl‐8 H ‐pyrrolo‐[1′,2′:1,2]imidazo[5,4‐y]quinoxaline is obtained.