SiO2-Cu2O: An efficient and recyclable heterogeneous catalyst for N-benzylation of primary and secondary amines

Abstract

A mild, effective, and selective procedure is reported for the mono N -benzylation and N , N -dibenzylation of primary amines as well as mono N -benzylation of secondary amines using silica-supported copper(I) oxide in water. The silica-supported Cu 2 O was generated in situ by the reaction of Fehling solution and glucose at 100 °C onto activated silica. The catalyst was filtered, washed with water, and oven-dried, and was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and atomic absorption spectroscopy. The prepared Cu 2 O-SiO 2 was found to be thermally stable up to 325 °C. The copper was uniformly distributed onto the surface of the silica, and the mean particle diameter was 7 nm. The catalyst served as a selective heterogenous catalyst for the N -benzylation of primary and secondary amines. The catalyst is recyclable and was used effectively upto fifth run without a significant loss of catalytic activity. Various reaction solvents including water, acetonitrile, and toluene were screened for N -benzylation of amines, and the success of the aqueous system highlights the low environmental impact of the procedure. Silica-supported Cu 2 O was prepared in situ using inexpensive and widely available starting materials and used as a catalyst for N -benzylation and N , N -dibenzylation of primary and secondary amines.