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 NZ 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 C-13 and Si-29 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 a-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. (C) 2009 Elsevier Inc. All rights reserved.