Asymmetric catalysis with self-organized chiral lanthanum complexes: practical and highly enantioselective epoxidation of alpha,beta-unsaturated ketones.
A highly efficient and practical method for obtaining alpha,beta-epoxy ketones with high optical purities was developed. The chiral lanthanum complex self-organized in situ from lanthanum triisopropoxide, (R)-BINOL, triarylphosphine oxide, and alkyl hydroperoxide (1:1:1:1) was found to catalyze the epoxidation of alpha,beta-unsaturated ketones with tert-butyl hydroperoxide or cumene hydroperoxide at room temperature to give the corresponding epoxy ketones in high enantioselectivities (up to >99% enantiomeric excess (ee)). A remarkably high asymmetric amplification, a positive nonlinear effect, was observed in the epoxidation of chalcone, which strongly suggests the formation of a dinuclear peroxide-involved mu-complex as the active catalyst.
Daikai
Kazuhiro
K
Institute for Fundamental Research of Organic Chemistry, Kyushu University, Fukuoka, Japan.
Hayano
Tetsuji
T
Kino
Rie
R
Furuno
Hiroshi
H
Kagawa
Takumi
T
Inanaga
Junji
J
D001685:Biological Factors / Q000138:chemical synthesis; D002384:Catalysis; D004852:Epoxy Compounds / Q000737:chemistry*; D007659:Ketones / Q000138:chemical synthesis* / Q000737:chemistry*; D007811:Lanthanum; D008958:Models, Molecular; D008968:Molecular Conformation; D004364:Pharmaceutical Preparations / Q000138:chemical synthesis; D013237:Stereoisomerism
D001685:Biological Factors; D004852:Epoxy Compounds; D007659:Ketones; D004364:Pharmaceutical Preparations; D007811:Lanthanum