Sterically Hindered Chiral Ferrocenyl P,N,N-Ligands for Highly Diastereo-/Enantioselective Ir-Catalyzed Hydrogenation of α-Alkyl-β-ketoesters via Dynamic Kinetic Resolution

A new class of sterically hindered chiral ferrocenyl P,N,N-ligands have been prepared through a two-step transformation from (S-c,R-p)-PPFNH2, in which a new (R)-stereogenic center at the pyridinylmethyl position was generated in high diastereoselectivity. With these newly developed P,N,N-ligands, Ir-catalyzed asymmetric hydrogenation of various alpha-alkyl substituted beta-aryl-beta-ketoesters via dynamic kinetic resolution has been realized in high diastereo- and enantioselectivities for the first time, which led to a variety of optically active anti-beta-hydroxyesters in up to 99% ee. The study indicated that the additional stereocenter at the pyridinylmethyl position of these ligands is crucial to realize this hydrogenation.