Base-free Asymmetric Transfer Hydrogenation of 1,2-Di- and Monoketones Catalyzed by a Chiral Iron(II) Hydride

Lorena De Luca; Antonio Mezzetti

doi:10.2533/chimia.2018.233

Base-free Asymmetric Transfer Hydrogenation of 1,2-Di- and Monoketones Catalyzed by a Chiral Iron(II) Hydride

Authors

Lorena De Luca Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland. deluca@inorg.chem.ethz.ch
Antonio Mezzetti Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland

DOI:

https://doi.org/10.2533/chimia.2018.233

Keywords:

Asymmetric transfer hydrogenation, Base-free, Benzoin, Hydride complexes, Iron catalysis

Abstract

The chiral iron(II) hydride complex [FeH(CNCEt3)(1a)](BF4) (3, 1a is a chiral macrocycle with an (NH)2P2 donor set) catalyzes the base-free transfer hydrogenation (ATH) of prochiral ketones and the hemireduction of benzils to the corresponding benzoins using iPrOH as hydrogen donor. Ketones give the same excellent enantio-selectivity (up to 99% ee) as the parent catalyst [Fe(CNCEt3)2(1a)](BF4)2 (2), which is only active upon treatment with NaOtBu. Benzoins, whose labile stereocenter is known to undergo racemization under basic conditions, are formed in up to 83% isolated yield with enantioselectivity as high as 95%.