Asymmetric Transfer Hydrogenation of 2,3-Disubstituted Flavanones through Dynamic Kinetic Resolution Enabled by RetroOxa-Michael Addition: Construction of Three Contiguous Stereogenic Centers

A ruthenium-catalyzed asymmetric transfer hydrogenation of 2,3-disubstituted flavanones was developed for the construction of three contiguous stereocenters under basic conditions through a combination of dynamic kinetic resolution and retro-oxa-Michael addition, giving chiral flavanols with excellent enantioselectivities and diastereoselectivities. The reaction proceeded via a base-catalyzed retro-oxa-Michael addition to racemize two stereogenic centers simultaneously in concert with a highly enantioselective ketone transfer hydrogenation step. The asymmetric transfer hydrogenation could be achieved at gram scale without loss of the activity and enantioselectivity.

Automated summary

In this study, a ruthenium-catalyzed asymmetric transfer hydrogenation of 2,3-disubstituted flavanones was developed. The reaction allowed for the construction of three contiguous stereocenters under basic conditions through a combination of dynamic kinetic resolution and retro-oxa-Michael addition. This method provided chiral flavanols with excellent enantioselectivities and diastereoselectivities.