Novel and efficient multifunctional periodic mesoporous organosilica supported benzotriazolium ionic liquids for reusable synthesis of 2,4,5-trisubstituted imidazoles

A series of periodic mesoporous organosilica supported benzotriazolium ionic liquids were synthesized and tested as effective and practical heterogeneous catalysts in the condensation reaction of diphenylethanedione, aromatic aldehydes and ammonium acetate. The catalyst PMO@ILBF4(1.0) showed brilliant catalytic activity for the synthesis of 2,4,5-trisubstituted imidazoles with good to high yields. We also found that the catalytic activity could be significantly influenced by the loading levels and functional anions of the benzotriazolium-cation ionic liquid, probably due to an intensification of intramolecular synergistic effect. Furthermore, the multifunctional catalyst PMO@ILBF4(1.0) could be easily recovered by filtration and recycled for six times with no significant loss in activity, indicating its excellent stability and reusability. This method provides an efficient and environmentally-friendly procedure for the production of 2,4,5-trisubstituted imidazoles.