Phosphotungstic acid and sulphonic acid functionalised SBA-15 for the synthesis of 2,4,5 trisubstituted and 1,2,4,5 tetrasubstituted imidazole derivatives

Over the past few decades, research has been consistently focused on the development of simple green synthetic routes for organic transformations. Mesoporous silica based solid acid catalysts have become popular because of their versatility to anchor functional moieties and adherence to the green chemistry principles. In this study, the catalytic activity of a bifunctional solid acid catalyst (HPW/SSA), synthesized by impregnation of phosphotungstic acid into sulphonic acid functionalized mesoporous SBA-15 (SSA), for the synthesis of tri and tetrasubstituted benzimidazoles is explored. Structural and morphological characterization of the catalyst established the successful incorporation of the functionalities without significant disruption of the mesoporous structure. The synthetic protocol is validated for a broad substrate scope. Under optimized conditions, an isolated yield above 75% could be obtained for tri and tetrasubstituted benzimidazoles. The recyclability of the catalyst was also verified.