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

Abstract

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 CC and CO 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.