Highly Efficient Iridium Catalyst for Asymmetric Transfer Hydrogenation of Aromatic Ketones under Base-Free Conditions

Catalytic systems generated in situ from the chiral PNNP ligands with iridium or rhodium hydride complexes exhibited excellent catalytic activity and good enantioselectivity in the asymmetric transfer hydrogenation of aromatic ketones without added base. The best result was obtained in the IrH(CO)(PPh₃)₃−ligand 2 catalytic system with up to 99% yield and 97% ee.