Study of chiral N-heterocyclic carbenes and their applications to asymmetric catalysis

Abstract

The Kundig group has developed Herrmann-Enders type bulky chiral N-heterocyclic carbene (NHC) ligand precursors during the last couple of years. The aim of this thesis is to study the intrinsic properties of these carbene ligands and to broaden their scope in the field of asymmetric catalysis. The structural properties of the NHCs had been studied by employing their corresponding NHC-BH3 adducts. Crystal structures of the NHC-BH3 complexes showed the importance of allylic strain in the arrangement of the ligands' substituents in space. Our interest in the electron donating ability of the NHCs motivated us to synthesize cis-Ir(CO)2Cl(NHC) type of complexes. Such complexes gave us the opportunity to compare the electron donating ability of the NHC ligands developed in our research group with the literature known NHC ligands. The chiral NHC ligands were tested in the asymmetric gold catalysis and ruthenium catalyzed asymmetric hydrogenation of prochiral ketones.