Unexpected transamination between 2-aminoazoles and N-iodoacetyl azoles

N-Iodoacetyl-substituted azoles undergo transfer of iodoacetyl group from heterocyclic N atom toward the amino group of amino azoles, unlike the earlier investigated iodomethyl ketones. The proposed mechanism explaining the observed difference in such transamination is confirmed by calculations. The product derived from 2-aminobenzimidazole is cyclized into fused imidazo[1,2-α]benzimidazol- 9-ium salt.