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*CoIII-catalyzed enantioselective C­(sp3)–H amidation of α-aryl thioamides using dioxazolones.