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

(S)-6,6'-Dibromo-BINOL and (S)-6,6'-diphenyl-BINOL have been developed as e fficient chiral ligands applicable to lanthanoid catalyzed asymmetric epoxi dation of alpha,beta -unsaturated ketones in the presence of cumene hydrope roxide. 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-di phenyl-BINOL catalyst at room temperature. A plausible catalyst structure a s well as the catalytic cycle has also been suggested. (C) 2001 Elsevier Sc ience Ltd. All rights reserved.