Abstract Cyclization of (non)-methylated nitro-o-phenylenediamines with cyanogen bromide provided nitro-substituted 2-aminobenzimidazoles in good up to excellent yields. Catalytic hydrogenation of 2-amino-1-methyl-5-nitrobenzimidazole yielded 2, 5-diamino-1- methylbenzimidazole, which on treatment with 1, 1, 3, 3-tetramethoxypropane in methanol and subsequently after removal of methanol in polyphosphoric acid afforded food-borne ...