Sulfonated Carbon/Silica Composites: Highly Efficient Heterogeneous Catalysts for the One-Pot Synthesis of Hantzsch 1,4-dihydropyridines, 2,4,5-trisubstituted Imidazoles and 2-arylbenzimidazoles

Sulfonated carbon/silica composites derived from biomaterials viz. glucose, maltose, cellulose, chitosan and starch exhibited high catalytic activity for the one-pot synthesis of Hantzsch 1,4-dihydropyridines under solvent-free conditions, and for one-pot synthesis of 2,4,5-trisubstituted imidazoles and 2-arylbenzimidazoles under liquid phase catalysis. The activity of sulfonated carbon/silica composites derived from starch was found to be superior to other sulfonated carbon/ silica composites. The excellent conversions showed that the catalyst has strong and sufficient acidic sites, which are responsible for its catalytic performance. Moreover, these solid acid catalysts owned the advantages of high selectivity and recyclability.