ZnS-ZnFe2O4: Magnetic nanocatalyst for efficient synthesis of tetrasubstituted benzimidazoles

Catalysts in chemical reactions improve the reaction conditions, increase the speed and yield of the products. So, they play a prominent role in various industries such as the chemical industry, petroleum industry, and pharmaceutical chemistry. In this work, an efficient and co-friendly method for the synthesis of 1,2,4,5-tetrasubstituted imidazoles via a four-component condensation of benzil, aldehydes, primary amines and ammonium acetate in the presence of a magnetic nanocatalyst, ZnS-ZnFe2O4, in ethanol under refluxing conditions is presented. Magnetic ZnS-ZnFe2O4 was prepared via a simple method and characterized by energy-dispersive X-ray analysis (EDAX), field-emission scanning electron microscopy (FESEM), X-Ray diffraction pattern (XRD) and vibrating sample magnetometer (VSM). This protocol has advantages such as high yields of the products, use of a green solvent, simple and chromatography-free work-up procedure. Most importantly, the catalyst can be conveniently recovered from the reaction mixture by using external magnet and reused for at least three times without significant decrease in catalytic activity.