Rapid advance has been achieved in the asymmetric catalysis using metal-chiral N-heterocyclic carbene (NHC) complexes as the catalysts in recent years. Increasing number of reports in this field and high enantioselectivities obtained under the catalysis of metal-NHC complexes have demonstrated the potential importance of metal-chiral NHC complexes in the catalytic, asymmetric synthesis of chiral compounds. Metal-chiral NHC complexes-catalyzed conjugate addition of α,β-unsaturated carbonyl compounds is reviewed. The results are summarized according to the ligated mode of NHC, from mono dentate to bidentate, with an intention to promote the design and discovery of high stereoselective catalysts with NHC ligands.

Key words: metal-NHC complex, copper, asymmetric catalysis, conjugate addition