Rhodium-Catalyzed Asymmetric Transfer Hydrogenation/Dynamic Kinetic Resolution of 3-Benzylidene-Chromanones.

Straightforward access to enantiomerically enriched cis-3-benzyl-chromanols from (E)-3-benzylidene-chromanones was developed through Rh-catalyzed asymmetric transfer hydrogenation. This transformation allowed the reduction of both the C═C and C═O bonds and the formation of two stereocenters in high yields with excellent levels of diastereo- and enantioselectivities (up to >99:1 dr, up to >99% ee) in a single step through a dynamic kinetic resolution process using a low catalyst loading and HCO2H/DABCO as the hydrogen source.