Copper Catalyzed Enantioconvergent Nucleophilic Substitutions

As a versatile earth-abundant transition metal, Cu has long been widely applied in the C-C and C-X bond forming reactions. As for now, low-valent Cu(I) is known to reduce the redox active electrophiles via an SET pathway to give the corresponding radical and Cu(II) species. The resulting Cu(II) species can interact with the radical via the out-sphere pathway, affording the coupling product. Alternatively, Cu(II) can trap the radical through the inner-sphere process to generate Cu(III) species and then realize challenging bond formations due to the facile reductive elimination of Cu(III) intermediate. Although copper catalysis has been widely applied in arylations of various nucleophiles, copper-catalyzed enantioconvergent nucleophilic substitutions of racemic alkyl electrophiles have been less explored, likely due to the difficulties in overcoming the reduction potential of alkyl electrophiles, elimination of side reactions, and enantiomeric control. In order to overcome the high reduction potential of alkyl electrophiles, the photo-induced strategy has been developed under mild conditions. An alternative strategy with new anionic tridentate ligands has also been reported in this regard. This review summarizes recent developments in copper-catalyzed enantioconvergent nucleophilic substitutions of alkyl electrophiles by various nucleophiles to realize C-N, C-C, C-B, C-P and C-O bond formations and their brief mechanistic studies.