Highly efficient enantioselective epoxidation of α,β-enones catalyzed by cheap chiral lanthanum and gadolinium alkoxides

[摘要] (S)-6,6'-Dibromo-BINOL and (S)-6,6'-diphenyl-BINOL have been developed as efficient chiral ligands applicable to lanthanoid catalyzed asymmetric epoxidation of alpha,beta -unsaturated ketones in the presence of cumene hydroperoxide. Excellent chemical yield and enantioselectivity have been achieved for several epoxides at room temperature by using 5 mol% of La(O-i-Pr)(3)-(S)-6,6'-dibromo-BINOL and Gd(O-i-Pr)3-(S)-6,6'-diphenyl-BINOL, respectively. Up to 95% ee was obtained for epoxychalcone with Gd(O-i-Pr)(3)-(S)-6,6-diphenyl-BINOL catalyst at room temperature. A plausible catalyst structure as well as the catalytic cycle has also been suggested. (C) 2001 Elsevier Science Ltd. All rights reserved.

[发布日期] 2001-12-03

[关键词] asymmetric epoxidation;alpha,beta-enones;chiral lanthanoid complexes