Acylation of sulfonamines using silica grafted 1-butyl-3-(3-triethoxysilylpropyl)-4,5-dihydroimidazolium ionic liquids as catalysts

Heterogeneous immobilized ionic liquid catalysts were prepared via grafting of 1,3-dimethyl-3-(3-triethoxysilylpropyl)-imidazolium tetrafluoroborate or bis{(trifluoromethyl)sulfonyl} imide ([NTf2]−) on silica supports with different surfaces and pore size. In addition to the adsorption–desorption isotherms of nitrogen at −196 °C, the catalysts were characterized by TG-DTA, XPS, DRIFTS, DR-UV–vis, NMR, and XRD techniques. The catalytic behavior was checked in the acylation of three different sulfonamines: benzenesulfonamine, p-nitrobenzenesulfonamine, and p-methoxybenzene-sulfonamine with acetic acid, acetic anhydride and maleic anhydride. These tests confirmed the acid Lewis properties of these catalysts.