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

Nano kaolin-SO3H as a new reusable and green heterogeneous catalyst was prepared by reaction of kaolin nanoparticles with chlorosulfonic acid. This new type of solid acid which contains the properties of a Lewis acid (Al3) and a Brønsted 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 work-up, high yields, solvent-free conditions and environmental friendly catalyst are some advantages of this protocol.