Ru-Catalyzed asymmetric hydrogenation of alpha-ketoesters with CeCl3.7H2O as additive.
[reaction: see text] An efficient asymmetric hydrogenation of alpha-ketoesters is reported with use of a catalyst prepared from [Ru((S)-3)(benzene)Cl]Cl and CeCl(3).7H(2)O. Alpha-hydroxy esters are obtained in up to 96% ee. The addition of CeCl(3).7H(2)O not only improves the enantioselectivity, but also enhances the stability of the catalyst. As a result, the hydrogenation of methyl benzoylformate affords the product with 92% ee with a substrate/catalyst ratio of 10 000. Hydrolysis of 2 provides the final compound with 83% yield at 99% ee after a single recrystallization from 1,2-dichloroethylene.
Sun
Yanhui
Y
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, China.
Wan
Xiaobing
X
Wang
Jianping
J
Meng
Qinghua
Q
Zhang
Hongwei
H
Jiang
Lijuan
L
Zhang
Zhaoguo
Z