Base-Free Asymmetric Transfer Hydrogenation of 1,2-Di- and Monoketones Catalyzed by a (NH)2 P2 -Macrocyclic Iron(II) Hydride.

Abstract

The hydride isonitrile complex [FeH(CNCEt3 )(1 a)]BF4 (2) containing a chiral P2 (NH)2 macrocycle (1 a), in the presence of 2-propanol as hydrogen donor, catalyzes the base-free asymmetric transfer hydrogenation (ATH) of prostereogenic ketones to alcohols and the hemihydrogenation of benzils to benzoins, which contain a base-labile stereocenter. Benzoins are formed in up to 83 % isolated yield with enantioselectivity reaching 95 % ee. Ketones give the same enantioselectivity observed with the parent catalytic system [Fe(CNCEt3 )2 (1 a)] (3 a) that operates with added NaOt Bu.