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. imidazoles are an important class of heterocycles being the core fragment of different natural products and biological systems such as anti-allergic, anti-inflammatory, analgesic, antifungal, antimycotic, antibiotic, antiulcerative, antibacterial, antitumor and inhibitors of the p38 map kinase. 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.