Kaolin-SO3H as an efficient catalyst for one- pot synthesis of 1,2,4,5-tetrasubstituted imidazoles

Kaolin-SO3H as a new solid acid is prepared via reaction of kaolin and chlorosulfonic acid. This natural based catalyst is very inexpensive and easy available. A simple, highly versatile and efficient synthesis of 1,2,4,5-tetrasubstituted imidazoles is achieved using Kaolin-SO3H as a catalyst at moderate temperature under solvent-free condition. The key advantages of this process are high yields with simple work-up using easy available inexpensive natural based catalyst.