Wells-Dawson heteropolyacid supported on silica: A highly efficient catalyst for synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles

摘要

Heteropolyacid H_6P_2W_(18)O _(62)?24H_2O (WD) supported on silica (WD/SiO _2) has been used as an effective catalytic system for the synthesis of various 1,2,4,5-tetrasubstituted imidazoles by four-component condensation of benzil, aldehydes, amines and ammonium acetate under solvent-free conditions. This approach can be useful for three-component synthesis of 2,4,5-trisubstituted imidazoles. The same reactions were repeated by using benzoin instead of benzil.