Catalytic Performance of Hydrophobic Sulfonated Nanocatalysts CMK-5-SO3H and SBA-15-Ph-PrSO3H for Ecofriendly Synthesis of 2-Substituted Benzimidazoles in Water

The hydrophobicity of environmentally benign organosulfonic acid-functionalized silica (SBA-15-Ph-PrSO3H) and sulfonic acidbased nanoporous carbon (CMK-5-SO3H) was assessed in relation to the green synthesis of 2-substituted benzimidazoles from aldehydes and benzene-1,2-diamine in open air in an aqueous medium. The results are rationalized in terms of the inclusion of the substrates inside hydrophobic cavities of the catalysts. Furthermore, the more hydrophobic and more water-resistant catalyst CMK-5-SO3H showed superior catalytic activity. Their excellent yields, their use of water as a green solvent, and their recyclability and environmentally friendly nature makes these catalysts important alternatives to classical acid catalysts.

benzimidazoles, heterogeneous catalysis, sulfonic acids, hydrophobicity, cyclizations