Template catalysis by manganese pincer complexes: oxa- and aza-Michael additions to unsaturated nitriles

Abstract

Activation of CN bonds by metal–ligand cooperation provides a new route for the functionalization of nitriles. Herein, we report the electrophilic activation of unsaturated nitriles by dearomatized manganese pincer complexes for the oxa- and aza-Michael addition reactions under very mild and neutral conditions. Derivatives of acrylonitrile and allyl cyanide furnished the corresponding β-addition products by reacting with alcohols and amines. Mechanistically, the catalysis is mostly ligand based. Reaction of the dearomatized PNN–Mn complex with 2-pentenenitrile or 3-pentenenitrile furnished an enamido–Mn complex. The equilibrium between an enamido complex and a ketimido complex, and reversible C–C bond formation with the ligand are proposed to play central roles in the catalysis.