Chiral Cyclopentadienyl Ligands Enable a Rhodium(III)-Catalyzed Enantioselective Access to Hydroxychromanes and Phthalides
The demand for efficient chiral cyclopentadienyl ligands (Cp-x) has increased significantly in recent years, partly because Cp*Rh(III) species have been developed as powerful catalysts for directed C-H functionalization reactions. However, a lack of suitable Cp-x ligands has hampered the development of the corresponding enantioselective processes. We report expansions of the libraries of two generations of Cp-x ligands and their corresponding rhodium(I) complexes. The potential of the rhodium complexes as catalysts was evaluated in enantioselective C-H functionalizations involving cyclizations across tethered aldehydes. The mild reaction conditions permit the syntheses of hydroxychromanes and phthalides in good yields and high enantioselectivities.