An extremely stable and highly active periodic mesoporous Lewis acid catalyst in water-medium Mukaiyama-aldol reaction

Abstract

A periodic mesoporous Lewis acid catalyst ((OTf)₂Sc-SO₃-Ph-PMO) was synthesized through chelating scandium triflate (Sc(OTf)₃) with sodium benzenesulfonate-functionalized periodic mesoporous silica (PhSO₃Na-Ph-PMO). Compared with homogeneous catalyst Sc(OTf)₃ and mesoporous SBA-15-supported scandium triflate catalyst ((OTf)₂Sc-SO₃-Ph-SBA-15), it exhibited superior catalytic activity and selectivity in water-medium Mukaiyama-aldol reaction. Hydrophobicity tests and substrate adsorption experiments demonstrated that its unique catalytic performance was related to the combined advantage of mesoporosity and hydrophobic microenvironment, which effectively stabilized and concentrated the substances as well as decreased intrinsic mass transfer resistance. Noted that the periodically arranged Lewis acids in the mesoporous silica framework inhibited the active sites leaching, leading to its high catalytic recyclability with almost unchanged catalytic efficiency for more than 10 times in water media.