Synthesis of chiral chromanols via a RuPHOX- Ru catalyzed asymmetric hydrogenation of chromones

Chiral chromanols and their derivatives have been synthesized via a RuPHOX-Ru catalyzed asymmetric hydrogenation of chromones in high yields, >20:1 drs and with up to 99.9% ee. Control experiments show that the reaction undergoes two sequential asymmetric hydrogenation steps of the C?C and C?O double bonds. The reaction could be performed on a gram-scale with a relatively low catalyst loading (up to 1000 S/C), and the resulting products can be transformed to several biologically active compounds.