Complementary Acetonitrile Reduction and Amine Adsorption on Mixed Cu–Ni Oxides for Electrocatalytic N-Ethylation

Abstract

N-ethylamines are important motifs in pharmaceuticals and fine chemicals, but their selective synthesis from nitriles requires control over both nitrile reduction and amine availability at the catalyst-electrolyte interface. Herein, we investigate mixed Cu–Ni oxides for the aqueous electrocatalytic C–N coupling of acetonitrile (MeCN) with benzylamine (BA). The optimized Cu-NiO-0.5 catalyst affords N-ethylbenzylamine (EBA) in 75% yield with 87% selectivity and a mass-normalized formation rate of 12.5 mmol h–1 gcat–1 at −0.5 VRHE. Electrochemical testing indicates that the presence of CuO can promote the MeCN electrochemical reduction, generating abundant ethylimine for subsequent coupling. Meanwhile, the incorporation of Ni significantly enhances the adsorption of BA, accelerating the C–N coupling between the ethylimine and BA. In situ experimental measurements further confirm the sequential reduction-condensation-reduction pathway. Moreover, this strategy has also been proven to enable efficient C–N coupling between MeCN and various amine derivatives, giving the corresponding N-ethylated products in 58.3–84.6% yield and greater than 74% selectivity. This work offers an environmentally friendly strategy for the electrocatalytic synthesis of N-ethylamines.