Catalytic asymmetric Darzens reaction promoted by a chiral phase-transfer catalyst derived from cinchonine is described. The desired α,β-epoxy ketones were obtained by use of α-chloro acyclic and cyclic ketones as substrates with moderate to high enantiomeric excesses under mild reaction conditions. This methodology can be quite an effective protocol for practical asymmetric synthesis.
Enantioselective Epoxidation of α,β-Enones by Electrophilic Activation with a BINOL-Zinc Catalyst
作者:Ana Minatti、Karl Heinz Dötz
DOI:10.1002/ejoc.200500606
日期:2006.1
affords, in situ, a catalyst for homogeneous epoxidation of (E)-α,β-enones to the corresponding trans-epoxy ketones. tert-Butyl hydroperoxide (TBHP) and cumene hydroperoxide (CMHP) are effective terminal oxidants for this process. Enantiomeric excesses of up to 96 % can be achieved conveniently at room temperature. Mechanistic investigations point towards an electrophilicactivation of the substrates
A Chiral BINOL-Zinc Complex as a Novel Catalyst for the Enantioselective Epoxidation of α,β-Enones
作者:Karl H. Dötz、Ana Minatti
DOI:10.1055/s-2004-829065
日期:——
First systematic studies on asymmetric epoxidation of electron-deficient α,β-enones with a simple zinc-BINOL catalyst in the presence of tert-butyl hydroperoxide and cumene hydroperoxide are described. The epoxidation proceeds in moderate to excellent yields with complete diastereoselectivity and high enantiomeric excesses by using enantiomerically pure BINOL. Different substituent effects are discussed
Self-supported BINOL–Zn catalysts for heterogeneous enantioselective epoxidation of (E)-α,β-unsaturated ketones
作者:Haiming Wang、Zheng Wang、Kuiling Ding
DOI:10.1016/j.tetlet.2009.02.151
日期:2009.5
A class of chiral self-supported catalysts prepared from bis-BINOL ligands and diethyl zinc were successfully applied in the hetereogeneous enantioselective epoxidation of a range of (E)-alpha,beta-unsaturated ketones, affording the corresponding epoxy ketones in high enantioselectivity. The self-supported catalysts were easily recovered from the reaction mixture and were reusable for several consecutive runs. (C) 2009 Elsevier Ltd. All rights reserved.
Asymmetric Epoxidation of α,β-Unsaturated Ketones Catalyzed by Chiral Polybinaphthyl Zinc Complexes: Greatly Enhanced Enantioselectivity by a Cooperation of the Catalytic Sites in a Polymer Chain
作者:Hong-Bin Yu、Xiao-Fan Zheng、Zhi-Ming Lin、Qiao-Sheng Hu、Wei-Sheng Huang、Lin Pu
DOI:10.1021/jo990749w
日期:1999.10.1
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.