A novel sodium iodide and ammonium molybdate co-catalytic system for the efficient synthesis of 2-benzimidazoles using hydrogen peroxide under ultrasound irradiation

•A H2O2/NaI/(NH4)6Mo7O24 system was first reported for synthesis of 2-benzimidazole.•Ultrasound was demonstrated to be benefit for accelerating this reaction.•The amounts of oxidant and catalyst are markedly reduced while keeping good yields.•The reaction was performed efficiently in green conditions with high yields.

The reaction of aldehydes and o-phenylenediamine for the preparation of 2-benzimidazoles has been studied using hydrogen peroxide as an oxidant under ultrasound irradiation at room temperature in this paper. The combination of substoichiometric sodium iodide and ammonium molybdate as co-catalysts, together with using small amounts of hydrogen peroxide, makes this transformation very efficient and attractive under ultrasound. Thus, a mild, green and efficient method is established to carry out this reaction in high yield.