Creation of acid–base bifunctional catalysis for efficient CC coupling reactions by amines immobilization on SiO2, silica-alumina, and nano-H-ZSM-5

Silica-supported amines (SiO2-NR2) were found to be excellent heterogeneous catalysts for various organic CC 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 SiO2-NR2 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 SiO2-NR2 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 SiO2 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 SiO2-NR2.