Oxidative amidation of benzaldehydes and benzylamines with N-substituted formamides over a Co/Al hydrotalcite-derived catalyst

Abstract

The present work describes a highly efficient synthetic strategy for amides via oxidative coupling of benzaldehydes or benzylamines with N-substituted formamides using a heterogeneous Co/Al hydrotalcite-derived catalyst in the presence of TBHP. A series of Co/Al hydrotalcite-derived catalysts (Cat-2, Cat-3, and Cat-4 with the Co²⁺/Al³⁺ molar ratio in the synthesis mixture as 1/1, 2/1 and 3/1) have been prepared by a simple co-precipitation method and characterized using powder XRD, XPS, FEG-SEM, EDS, FT-IR, DTG-TGA and N₂ physical adsorption techniques. Among the as-prepared catalysts, Cat-3 exhibited excellent catalytic activity towards the direct amidation of benzaldehydes as well as benzylamines bearing various substituents into the corresponding amides at 100 °C using TBHP as an oxidant. The mechanistic investigation of the amidation reaction revealed that the reaction follows a radical pathway. Furthermore, the catalyst is easily separable and recyclable without considerable loss in catalytic activity.