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.