Chiral NHC–metal-based asymmetric catalysis

Abstract The strong σ-donor but poor π-acceptor abilities of N-heterocyclic carbenes (NHCs) result in chemical stability and coordination versatility, thus allowing them to coordinate with many metals ranging from alkaline-earth metals to rare-earth metals. Moreover, the easy introduction of chiral elements into NHCs and the facile preparation of their precursors have made chiral NHCs promising chiral ligands in metal-based asymmetric catalysis. Therefore, strategies for the design of efficient NHC–metal catalysts and novel asymmetric synthetic methodologies have dramatically increased over the past 10 years. Herein, the growing field of chiral NHC–metal-based asymmetric catalysis is comprehensively described.