Ru(II)-SDP-complex-catalyzed asymmetric hydrogenation of ketones. Effect of the alkali metal cation in the reaction.
The Ru(II) complexes of SDP and DPEN combined with t-BuOK in 2-propanol formed a very effective catalyst for the hydrogenation of simple aromatic ketones with high activity and enantioselectivity. The racemic alpha-arylcycloalkanones can also be hydrogenated by this system, providing alpha-arylcycloalkanols in excellent cis/trans stereoselectivity (>99:1) and enantioselectivity (up to 99.9%) for the cis isomer. In the study of the effect of the alkali metal cation in the hydrogenation of acetophenone using RuCl(2)(Tol-SDP)(DPEN) and RuCl(2)(Xyl-SDP)(DPEN) catalysts, we found that t-BuONa provided a faster reaction than t-BuOK, which indicated that the sterically hindered diphosphine ligands preferred the base with the smaller metal cation.
Xie
Jian-Hua
JH
State Key Laboratory and Institute of Elemento-organic Chemistry, Nankai University, Tianjin 300071, China.
Liu
Sheng
S
Huo
Xiang-Hong
XH
Cheng
Xu
X
Duan
Hai-Feng
HF
Fan
Bao-Ming
BM
Wang
Li-Xin
LX
Zhou
Qi-Lin
QL