An Efficient Synthesis of Tri- and Tetrasubstituted Imidazoles from Benzils Using Functionalized Chitosan as Biodegradable Solid Acid Catalyst

An environmentally benign, highly efficient one-pot four-component synthesis of highly functionalized imidazole derivatives using different aldehydes, substituted amines, benzil, and ammonium acetate in the presence of biodegradable and highly efficient catalyst chitosan–SO3H were described. Chitosan–SO3H was found to be a heterogeneous acidic catalyst which allowed easy recovery of the catalyst. Use of microwave irradiation along with chitosan–SO3H for the synthesis of imidazole derivatives makes this protocol green. Moreover, excellent yields, shorter reaction time, chromatography-free purification, and elimination of environmentally hazardous solvents are other advantages of this protocol which leads to sustainability.