Hybrid mesoporous materials containing covalently anchored N-phenylthiazolium salts as organo catalysts

A heterogenized organo catalyst based on an organic–inorganic hybrid material was synthesized by covalently anchoring N-phenylthiazolium salts onto mesoporous silica MCM-41 materials. The results of powder X-ray diffraction and N2 adsorption show the persistence of the ordered two-dimensional hexagonal mesostructure of the functionalized materials. The integrity of the organic groups in the mesoporous materials is confirmed by solid-state 13C and 29Si CP-MAS–NMR spectroscopy. These hybrid mesoporous materials are efficient catalysts for the benzoin condensation and for the cross-coupling of aldehydes with acylimines to yield α-amido ketones. The catalytic activity of the heterogenized organo catalyst can further be enhanced by silylation of the residual Si–OH groups using Me3SiCl, due to an increased hydrophobicity of the support’s surface. The recyclability of the catalysts depends on the solvent of reaction: here aprotic and solvents of low polarity turned out to be beneficial.