title: Asymmetric Epoxidation of alpha,beta-Unsaturated Ketones Catalyzed by Chiral Polybinaphthyl Zinc Complexes: Greatly Enhanced Enantioselectivity by a Cooperation of the Catalytic Sites in a Polymer Chain.
abstract: Polybinaphthyl zinc catalysts have been developed for the asymmetric epoxidation of alpha,beta-unsaturated ketones in the presence of tert-butyl hydroperoxide. Up to 81% ee has been achieved for the epoxidation of alpha,beta-unsaturated ketones containing beta-aliphatic substituents by using a binaphthyl polymer combined with diethylzinc. A very interesting positive cooperative effect of the catalytic sites in the polymer chain is observed which leads to greatly increased enantioselectivity over the corresponding monomer ligands.
authors.affiliation: Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901.
authors.forename: Hong-Bin
authors.initials: HB
authors.lastname: Yu
authors.forename: Xiao-Fan
authors.initials: XF
authors.lastname: Zheng
authors.forename: Zhi-Ming
authors.initials: ZM
authors.lastname: Lin
authors.forename: Qiao-Sheng
authors.initials: QS
authors.lastname: Hu
authors.forename: Wei-Sheng
authors.initials: WS
authors.lastname: Huang
authors.forename: Lin
authors.initials: L
authors.lastname: Pu