Creation of acid–base bifunctional catalysis for efficient C [sbnd]C coupling reactions by amines immobilization on SiO 2, silica-alumina, and nano-H-ZSM-5

Abstract

Silica-supported amines (SiO 2-NR 2) were found to be excellent heterogeneous catalysts for various organic C C coupling reactions, namely cyanation, Michael reaction, and nitro–aldol reaction. A wide variety of substrates, such as aromatic, heteroaromatic, aliphatic, and cyclic carbonyl compounds, can be efficiently converted into the corresponding cyano- O-ethoxycarbonylation products. The SiO 2-NR 2 also promoted Michael reaction of ethyl cyanoacetae with cyclohexen-1-one and nitro–aldol reaction of nitromethane with benzaldehyde. These reactions proceeded on the catalyst surfaces, and the SiO 2-NR 2 catalysts were able to be reused without any significant loss of catalytic performance. Notably, these reactions were hard to occur either with amines alone or on the SiO 2 alone, which indicates a dual activation mechanism of basic amine group and surface silanol. In addition, amines immobilized on more acidic support of silica-alumina showed higher catalytic performances than that of the SiO 2-NR 2.