Cooperative NHC and nickel-catalyzed asymmetric reductive coupling of nitrobenzyl bromides and cyclic ketimines via SET process

Abstract

An enantioselective reductive coupling of nitrobenzyl bromides with cyclic ketimines via single-electron-transfer (SET) process was realized via a synergistic combination of N-heterocyclic carbene (NHC) catalysis and nickel catalysis. This protocol could overcome the limitation of homoenolate radical species, providing an important influence on the tight stereocontrol of the nitrobenzyl radical intermediate and offering a direct and facile route to previously inaccessible, enantioenriched 4-substituted 4-aminopyrazolones and 3-substituted 3-aminooxindoles. Moreover, this NHC/metal cooperative catalysis might provide complementary access to new reaction pathways, especially asymmetric radical reactions.