Construction of Planar Chiral Ferrocenes by Cobalt-Catalyzed Enantioselective C-H Acyloxylation Enabled by Dual Ligands

Oxy-substituted planar chiral ferrocenes are of greatimportance in asymmetric synthesis and pharmaceu-ticals. However, enantioselective C-H activation offerrocenes that form C-O bonds remains a hugechallenge and has not yet been reported. Herein, theasymmetric synthesis of oxy-substituted planar chi-ral ferrocenes is achieved by cobalt-catalyzed enan-tioselective dehydrogenative C-H acyloxylation. Theuse of a dual-ligand system consisting of a chiralsalicyloxazoline (Salox) ligand and a neutral phos-phine oxide ligand, which is oxidized in situ fromthe corresponding phosphine, resulted in good yield(up to 83%) and excellent enantioselectivity (90-99% ee). The utility of this unprecedented pro-tocol is highlighted by its versatile synthetic trans-formations.