Synthesis of 1,2,4,5-tetrasubstituted imidazoles by a sequential one-pot reaction using tin tetrachloride supported on nanosilicagelas an efficient catalyst

An efficient and convenient synthesis of 1,2,4,5-tetrasubstituted imidazoles has been achieved by a one-pot, fourcomponent reaction of benzil, an aromatic aldehyde, primary amine and ammonium acetate in the presence of tin tetrachloride supported on silica gel nanoparticles (SnCl4/SiO2 NPs) in improved yields. According to the obtained data, many of these protocols have one or more disadvantages, such as long reaction times, expensive catalysts, large amounts of catalysts and tedious procedure or work-up. For example sulfonated carbon/silica composit and cyclic phosphoric acid have more yields but have lasted longer (10 and 20 h). These results clearly show the advantages of our methodology over other protic or Lewis acid catalyzed 1,2,4,5-tetrasubstituted imidazole synthesis such as low consumption of catalyst, shorter reaction time and excellent yields.A mixture of aldehyde, benzil, aniline or benzyl amine, ammonium acetate and SnCl4/SiO2 NPs in ethanol was reacted at refluxing temperature. After the disappearance of the starting materials (monitored by TLC), the mixture was filtered to remove the catalyst. By evaporation of the solvent, the crude product was recrystallized from hot aq. ethanol to obtain the pure compound.