title: C(2) symmetric chiral NHC ligand for asymmetric quaternary carbon constructing copper-catalyzed conjugate addition of grignard reagents to 3-substituted cyclohexenones.
abstract: The asymmetric construction of quaternary carbon centers by conjugate addition of Grignard reagents to 3-methyl- and 3-ethylcyclohexenones was realized in a maximum enantioselectivity of 80% by using a C 2 symmetric chiral N-heterocyclic carbene (NHC)-copper catalyst, generated from (4 S,5 S)-1,3-bis(2-methoxyphenyl)-4,5-diphenyl-4,5-dihydro-1 H-imidazol-3-ium tetrafluoroborate and copper(II) triflate. The stereostructures of the NHC-Au complexes were analyzed by X-ray crystallography, which rationalized the good stereocontrolling ability of N-aryl NHCs.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo, Kyoto, Japan.
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Matsumoto
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Yamada
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Tomioka
mesh_terms: D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D053138:Cyclohexenes / Q000737:chemistry*; D007202:Indicators and Reagents / Q000737:chemistry*; D008024:Ligands; D013237:Stereoisomerism
chemical_list: D053138:Cyclohexenes; D007202:Indicators and Reagents; D008024:Ligands; D002244:Carbon