Iridium-Catalyzed Asymmetric Hydrogenation of Racemic β-Keto Lactams via Dynamic Kinetic Resolution.

A highly efficient Ir-catalyzed asymmetric hydrogenation of racemic β-keto lactams via dynamic kinetic resolution (DKR) for the synthesis of optically active β-hydroxyl lactams has been described. With the Ir-SpiroSAP catalyst, a series of racemic β-keto lactams including β-keto γ-, δ-, and ε-lactams were hydrogenated to chiral β-hydroxy lactams in high yields (87-99%) with excellent enantio- and diastereoselectivity (83-99.9% ee, syn/anti: 97:3->99:1) at low catalyst loading under mild reaction conditions. This efficient method has been successfully applied in the synthesis of the chiral intermediate of fluoroquinolone antibiotic premafloxacine.