Acid–Base Bifunctional Catalysis of Silica–Alumina‐Supported Organic Amines for Carbon–Carbon Bond‐Forming Reactions

Abstract

Abstract Acid–base bifunctional heterogeneous catalysts were prepared by the reaction of an acidic silica–alumina (SA) surface with silane‐coupling reagents possessing amino functional groups. The obtained SA‐supported amines (SA–NR 2 ) were characterized by solid‐state 13 C and 29 Si NMR spectroscopy, FT‐IR spectroscopy, and elemental analysis. The solid‐state NMR spectra revealed that the amines were immobilized by acid–base interactions at the SA surface. The interactions between the surface acidic sites and the immobilized basic amines were weaker than the interactions between the SA and free amines. The catalytic performances of the SA–NR 2 catalysts for various carbon–carbon bond‐forming reactions, such as cyano‐ethoxycarbonylation, the Michael reaction, and the nitro‐aldol reaction, were investigated and compared with those of homogeneous and other heterogeneous catalysts. The SA–NR 2 catalysts showed much higher catalytic activities for the carbon–carbon bond‐forming reactions than heterogeneous amine catalysts using other supports, such as SiO 2 and Al 2 O 3 . On the other hand, homogeneous amines hardly promoted these reactions under similar reaction conditions, and the catalytic behavior of SA–NR 2 was also different from that of MgO, which was employed as a typical heterogeneous base. An acid–base dual‐activation mechanism for the carbon–carbon bond‐forming reactions is proposed.