Tetrazoles have many interesting futures and applications in drug and energy industries. 5-Substituted 1H-tetrazoles were synthesized via [2+3] cycloaddition reaction of aryl or alkyl nitriles with sodium azide in the presence of Fe3O4@SiO2.SnCl4 as catalyst in DMF under reflux conditions. The catalyst was removed from reaction mixture by an external magnet and was reusable for many times without any appreciable loss of its activity. The Fe3O4@SiO2.SnCl4 promotes synthesis of tetrazole in shorter time than other reported catalysts. The obtained tetrazoles were identified by spectroscopic and physical data such as FT-IR, 1HNMR and melting point. Easy workup and reusability of catalyst are some advantages of this protocol. پرونده مقاله

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. پرونده مقاله