Synergetic catalytic effect of ionic liquids and ZnO nanoparticles on the selective synthesis of 1,2-disubstituted benzimidazoles using a ball-milling technique

A solvent-free selective green synthesis of 1,2-disubstituted benzimidazoles was developed using a ball-milling technique. Recyclable ionic liquid-coated ZnO-nanoparticles (ZnO-NPs, catalyst 5) were employed as a catalyst, which produced high yields, turnover number and turnover frequency because of the synergetic catalytic properties of the ionic liquid and ZnO-NPs. The present method was successfully employed in the synthesis of various 1,2-disubstituted benzimidazole derivatives in excellent yields with high selectivity. The reaction could also be performed on a multi-gram scale with the same efficiency. A high eco-scale score and a low E-factor emphasize the ecofriendly nature of the present method.