Direct N‐Alkylation of Amines with Alcohols Catalyzed by N‐Heterocyclic Carbene Cobalt‐Pincer Catalyst under Mild Conditions

Abstract

AbstractAlcohols are widely available and can be derived from renewable resources. Catalytic alcohol amination for N‐alky amine synthesis using the borrowing hydrogen strategy is an environmentally benign and prominent sustainable method, which produces water as the sole byproduct. However, expensive noble metals are generally employed for this transformation, while the nonprecious metal‐based catalysts were also known for this reaction and have attracted considerable attention recently. Herein, an efficient N‐alkylation of amines with alcohols using base‐metal cobalt catalysts is reported. This reaction is catalyzed by an N‐heterocyclic carbene cobalt‐pincer catalyst and the reaction operates simply and under mild conditions. Various alcohol and aniline substrates and functional groups including nitrile, ether, thioether and alkene could be well tolerated. Moreover, experimental studies and DFT calculations were also performed to illustrate the reaction mechanism. Our results suggest that the N‐alkylation reaction proceeds via a hydrogen autotransfer mechanism.