Chiral 2-Aryl Ferrocene Carboxylic Acids for the Catalytic Asymmetric C(sp3)-H Activation of Thioamides

Enantioselective C-H functionalization reactions using trivalent group 9 metals (Co, Rh, Ir) have been investigated mainly on the basis of the development of well-designed chiral cyclopentadienyl (Cp) ligands. Although it has recently been demonstrated that chiral carboxylic acids combined with achiral Cp-type ligands can enable highly enantioselective C-H functionalization reactions, the structural diversity of the applied chiral acids remains limited. Here, we report that chiral 2-aryl ferrocene carboxylic acids, which are easily obtained from diastereoselective ortho lithiation and Suzuki-Miyaura coupling, can serve as external chiral sources for the Cp*Co-III-catalyzed enantioselective C(sp(3))-H amidation of alpha-aryl thioamides using dioxazolones.