Asymmetric C-h Arylation For The Synthesis Of Planar Chiral Ferrocenes: Controlling Enantioselectivity Using Chiral Phosphoric Acid

Transition-metal-catalyzed direct activation reactions of C-H bond have been extensively developed in recent years. Although numerous synthetic methods have been reported to build diverse complex compounds, enantioselective C-H activation has not been paid much attention probably because of the absence of suitable ligands to control the stereoselectivity in the C-H activation reaction. Chiral phosphoric acids have also been applied in the Pd-catalyzed enantioselective C-H activation reactions recently.Herein, a Pd(O)-catalyzed enantioselective synthesis of planar chiral ferrocenes was described, and chiral phosphoric acids were used as the only chiral source to control the stereoselectivity in the C-H activation reactions. The desired product was obtained with 64%～93% isolated yields and 57%-83% ee value; Then we applied the method to enantioselective C(sp3)-H activation, two corresponding products were isolated with 50% and 67% ee value respectively; Unfortunately, the asymmetric reaction of 8-aminoquinoline directed ferrocene derivatives with iodobenzene produced only diphenylate compound under selected conditions, which indicates that more efforts are required.