Certain precious metal complexes are efficient catalysts for the asymmetric hydrogenation (AH) of ketones and imines into their corresponding enantiopure alcohols and amines, respectively. These products have wide industrial applications, especially in the pharmaceutical industry. Currently, most of the asymmetric hydrogenation catalysts rely on phosphine ligands as the electronic and steric handle. In contrast, N-heterocyclic carbenes (NHC) have been demonstrated in recent years as effective ligands for a variety of catalytic applications. In 2016, we reported a new ligand, “Kaibene”, which is a primary amine-tethered NHC containing two chiral centers. In this presentation, our recent development and mechanistic investigation of highly active half-sandwich ruthenium complexes based on Kaibene for asymmetric hydrogenation of ketones will be discussed. At 50°C in 2-propanol, under 25 bars of H2(g), [RuCp*(Kaibene)(CH3CN)](PF6) can hydrogenate a variety of aryl ketones with TON up to 10000, TOF up to 171000 h-1, and up to 60% e.e.

Half-sandwich ruthenium catalysts with enantiopure primary amine-tethered N-heterocyclic carbenes for asymmetric ketone hydrogenation

253rd National Meeting (2017)

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