Recent Application of Iridium(III)-Cyclopentadienyl Ligands in Asymmetric Catalysis

Abstract Asymmetric catalysis is indispensable for the synthesis of optically active molecules, where chiral ligands play a pivotal role in governing both stereoselectivity and catalytic efficiency. Cyclopentadienyl (Cp) ligands form stable complexes with Ir(III), enabling asymmetric transformations through strategies including the use of external chiral additives or inherently chiral Cp derivatives. However, recent progress in Cp*Ir(III) catalytic systems—specifically those incorporating preinstalled chiral ligands—has yet to be systematically summarized. This review summarizes advances in N,N′-; N,C-; and N,O-chelating ligands, focusing on their applications in Cp*Ir(III)-catalyzed asymmetric reactions: (transfer) hydrogenation of ketones, imines, and quinolines; nitrene transfer for C(sp3)–H amidation; borrowing-hydrogen catalysis; and cooperative catalysis with chiral phosphoric acids. Key reaction mechanisms, rationales for stereocontrol, and substrate scopes are highlighted. Finally, current challenges (e.g., limited accessibility and diversity of ligands) and future research directions are also addressed.