The selective synthesis of -arylbenzene-1,2-diamines or 1-arylbenzimidazoles by irradiating 4-methoxy-4′-substituted-azobenzenes in different solvents

The solvent-controllable photoreaction of 4-methoxyazobenzenes to afford 1-aryl-1 H -benzimidazoles or N -arylbenzene-1,2-diamines has been studied. The irradiation of 4-methoxyazobenzenes in DMF containing 0.5 M hydrochloric acid provided N 2 -aryl-4-methoxybenzene-1,2-diamines as the major product, while irradiation in acetal containing 0.16 M hydrochloric acid led to 1-aryl-6-methoxy-2-methyl-1 H -benzimidazoles as the major product. A possible reaction mechanism explaining the selectivity was also discussed. A solvent-controllable photoreaction involving 4-methoxyazobenzenes has been developed to synthesize 1-aryl-1 H -benzimidazoles or N -arylbenzene-1,2-diamines in moderate to good yields.