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. The control experiments showed that the asymmetric hydrogenation of the CC double bond occurs first followed by the reduction of the CO double bond.