Nano kaolin-SO3H as a new efficient and reusable catalyst for one-pot synthesis of 2,4,5-trisubstituted imidazoles in solvent-free conditions

Nano kaolin-SO3H as a new reusable and green heterogeneous catalyst was prepared by the reaction of kaolin nanoparticles with chlorosulfonic acid. This new type of solid acid, which contains the properties of a Lewis acid (Al3+) and a Br?nsted acid (SO3H group), was characterized by FT-IR, XRD, SEM, TEM, XRF, EDS, and TGA. Nano kaolin-SO3H was used as a recoverable acidic heterogeneous catalyst for one-pot synthesis of 2,4,5-trisubstituted imidazoles via three-component condensation of 1,2-diketones, various aromatic aldehydes, and ammonium acetate. Short reaction time, simple workup, high yields, solvent-free conditions, and environmental friendly catalysts are some advantages of this protocol.