Palladium, iridium, and rhodium complexes bearing chiral N-heterocyclic carbene ligands applied in asymmetric catalysis

Abstract

The field of asymmetric catalysis is rapidly developing and the chiral ligands play a key role in enantioselective transition-metal catalysis. The electron-rich chiral N-heterocyclic carbenes (NHCs) have established themselves as a popular class of stereodirecting ancillary ligands to catalyze enantioselective organic transformations in more efficient ways. Several novel transition-metal complexes in combination with tailored ligand design have emerged during last few decades in asymmetric catalysis. The tailor-made NHCs can easily be accessed due to the modular synthesis of their parent azolium salt precursors. Their donor capability and the molecular shape can easily be tuned by changing substituent at N-atom or by changing the cyclic backbone framework. This review article aims to describe the recent advances in this rapidly evolving research area of enantioselective catalysis using well-defined transition-metal complexes possessing chiral NHC donor ligands.