Proline-Based P,O Ligand/Iridium Complexes as Highly Selective Catalysts: Asymmetric Hydrogenation of Trisubstituted Alkenes

P,O joins the mix: P,O ligands (L1) form efficient iridium catalysts for the asymmetric hydrogenation of olefins. The proline-derived ligands lead to high enantioselectivities with several classes of alkenes, most notably with α,β-unsaturated carboxylic esters and ketones, where they match or even surpass the ee values reported for the best N,P and C,N ligands.