Rh-Mediated Asymmetric-Transfer Hydrogenation of 3-Substituted Chromones: A Route to Enantioenriched cis-3-(Hydroxymethyl)chroman-4-ol Derivatives through Dynamic Kinetic Resolution.

Enantioenriched cis-3-(hydroxymethyl)chroman-4-ol derivatives were conveniently prepared by rhodium-catalyzed asymmetric transfer hydrogenation of 3-formylchromones through a dynamic kinetic resolution process. The reaction proceeded under mild conditions using a low catalyst loading and HCO2H/Et3N (5:2) as the hydrogen source, delivering the reduced compounds in good yields, high diastereomeric ratio (up to 98:2 dr), and excellent enantioselectivities (up to >99% ee).