The Manganese(I)-Catalyzed Asymmetric Transfer Hydrogenation of Ketones: Disclosing the Macrocylic Privilege.

The bis(carbonyl) manganese(I) complex [Mn(CO)2 (1)]Br (2) with a chiral (NH)2 P2 macrocyclic ligand (1) catalyzes the asymmetric transfer hydrogenation of polar double bonds with 2-propanol as the hydrogen source. Ketones (43 substrates) are reduced to alcohols in high yields (up to >99 %) and with excellent enantioselectivities (90-99 % ee). A stereochemical model based on attractive CH-π interactions is proposed.