Sustainable, green protocols for heterogenized organocatalysts: N-Phenylthiazolium salts heterogenized on organic–inorganic hybrid mesoporous supports

Abstract

A heterogenized organocatalyst was synthesized by the covalent anchoring of N-phenyl-thiazolium salts over mesoporous organosilica (phenylene–silica, ethane–silica) and mesoporous silica (MCM-41) supports. Powder X-ray diffraction patterns as well as nitrogen physisorption analysis confirmed the retention of mesoporous structure after the grafting reactions. Solid-state NMR analysis ( 13C CP-MAS NMR, 29Si MAS NMR) certified the integrity of organocatalyst residing inside the pore channels of the mesoporous supports. Catalytic evaluation in the benzoin condensation reaction as well as in the cross-coupling of aldehydes with acyl imines indicated that the organocatalyst heterogenized on mesoporous phenylene organosilica exhibited higher catalytic activity, stability and reusability than the analogous mesoporous silica support. The better activity and stability of the phenylene–silica support was attributed to the enhanced hydrophobic properties arising from the frame wall organic groups.