Immobilized ionic liquid on superparamagnetic nanoparticles as an effective catalyst for the synthesis of tetrasubstituted imidazoles under solvent-free conditions and microwave irradiation

The ionic liquid 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium chloride was immobilized on superparamagnetic Fe3O4 nanoparticles (IL-MNPs) and used as an efficient heterogeneous catalyst for the one-pot synthesis of 1,2,4,5-tetrasubstituted imidazoles under solvent-free conditions using microwave irradiation. The reactions in conventional heating conditions were compared with the microwave-assisted reactions. The combined merits of microwave irradiation and immobilized ionic liquid on superparamagnetic nanoparticles make the four-component condensation with safe operation, low pollution, and rapid access to products and simple work-up.

Graphical abstractWe report the immobilization of 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium chloride on magnetic Fe3O4 nanoparticles, as a new heterogeneous catalyst for the synthesis of 1,2,4,5-tetrasubstituted imidazoles via one-pot condensation of 1,2-diketone with aldehyde, amine, and NH4OAc in the presence of IL-MNPs as an inexpensive solid acid catalyst under solvent-free classical heating conditions or using microwave irradiation. The heterogeneous catalyst could be recovered easily and reused many times without significant loss of its catalytic activity. Furthermore, the catalyst could be magnetically isolated with a permanent magnet and the yields achieved are above 90% after it has been reused at least five times.Figure optionsDownload full-size imageDownload as PowerPoint slide