Highly Diastereoselective Formation of Ruthenium Complexes for Efficient Catalytic Asymmetric Transfer Hydrogenation

we have described herein a practical
procedure for the simple preparation of the single-diastereomer
catalysts cis-[RuCl2(Josiphos)RPyme]—also in situ—
from [RuCl2(PPh3)3], Josiphos ligands, and a racemic mixture
of RPyme ligands, avoiding the need for the resolution of the
aminopyridine ligands. These complexes efficiently catalyze
the asymmetric transfer hydrogenation of ketones with both a
very high TOF (up to 70000 h1 at 60 8C)and enantioselectivity
(up to 99%ee)which is due to the correctly matched
diphosphane and aminopyridine ligands. Work is in progress
to extend this practical approach to other metal-catalyzed
asymmetric reactions.