A new efficient bis(phosphinite)-ruthenium(II) catalyst system for the asymmetric transfer hydrogenation of aromatic ketones

Many chiral ligands bearing phosphorus donor atoms were developed and applied in the area of metal catalyzed asymmetric catalysis. A new chiral bis(phoshinite) ligand was successfully synthesized from optically active (1S,8S)-3,6-[N-(S)-α-phenylethyl]diaza-1,8-diphenoxymethyl-1,8-octanediol in high yield. A ruthenium(II) complex generated in situ from [Ru(η6-p-cymene)(μ-Cl)Cl]2, bis(phosphinite) ligand and KOH acts as an active catalyst for asymmetric transfer hydrogenation (ATH) of acetophenone derivatives in isopropyl alcohol (IPA) as both solvent and hydrogen source. The catalytic reaction proceeds cleanly to give enantiomerically enriched secondary alcohols up to 90% or 89% ee’s at 50 or 82 °C, respectively.