Catalytic asymmetric epoxidation of alpha,beta-unsaturated esters with chiral yttrium-biaryldiol complexes.
The full details of the asymmetric epoxidation of alpha,beta-unsaturated esters catalyzed by yttrium complexes with biaryldiol ligands are described. An yttrium-biphenyldiol catalyst, generated from Y(OiPr)3-biphenyldiol ligand-triphenylarsine oxide (1:1:1), is suitable for the epoxidation of various alpha,beta-unsaturated esters. With this catalyst, beta-aryl alpha,beta-unsaturated esters gave high enantioselectivities and good yields (< or = 99% ee). The reactivity of this catalyst is good, and the catalyst loading could be decreased to as little as 0.5-2 mol % (the turnover number was up to 116), while high enantiomeric excesses were maintained. For beta-alkyl alpha,beta-unsaturated esters, an yttrium-binol catalyst, generated from Y(OiPr)3-binol ligand-triphenylphosphine oxide (1:1:2), gave the best enantioselectivities (< or = 97% ee). The utility of the epoxidation reaction was demonstrated in an efficient synthesis of (-)-ragaglitazar, a potential antidiabetes agent.
Kakei
Hiroyuki
H
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Tsuji
Riichiro
R
Ohshima
Takashi
T
Morimoto
Hiroyuki
H
Matsunaga
Shigeki
S
Shibasaki
Masakatsu
M
D002384:Catalysis; D004852:Epoxy Compounds / Q000138:chemical synthesis*; D004952:Esters / Q000737:chemistry; D010078:Oxazines / Q000138:chemical synthesis*; D010666:Phenylpropionates / Q000138:chemical synthesis*; D013237:Stereoisomerism; D015019:Yttrium
D004852:Epoxy Compounds; D004952:Esters; D010078:Oxazines; D010666:Phenylpropionates; D015019:Yttrium; C432703:ragaglitazar