Simultaneous Access to Two Enantio-enriched Alcohols by a Single Ru-Catalyst: Asymmetric Hydrogen Transfer from Racemic Alcohols to Matching Ketones

Oxidative kinetic resolution and asymmetric transfer hydrogenation are two classical methods to access chiral secondary alcohols. Described here is an example of cross asymmetric hydrogen transfer between H-donor racemic alcohols and H acceptor prochiral ketones, which merge these two approaches in one catalytic cycle that could afford two chiral alcohols simultaneously. To create a large equilibrium constant for driving the reversible processes into completion, H-donor alcohols and H acceptor ketones should have substituents with significantly different properties in sterics or electronics, yet this would cause a substantial challenge for a single catalyst to induce high ee's for both alcohols. Moreover, either enantiomer of a racemic alcohol could be obtained via sequential transfer hydrogenations with a single Ru-catalyst. These results collectively provide efficient access to two distinct enantio-enriched alcohols as well as both enantiomers of single alcohols.