Asymmetric Transfer Hydrogenation of Arylketones Catalyzed by Enantiopure Ruthenium(II)/Pybox Complexes Containing Achiral Phosphonite and Phosphinite Ligands

Molecules. 2020 Feb 23;25(4):990. doi: 10.3390/molecules25040990.

Abstract

A family of complexes of the formula trans-[RuCl2(L)(R-pybox)] (R-pybox = (S,S)-iPr-pybox, (R,R)-Ph-pybox, L = monodentate phosphonite, PPh(OR)2, and phosphinite, L = PPh2(OR), ligands) were screened in the catalytic asymmetric transfer hydrogenation of acetophenone, observing a strong influence of the nature of both the R-pybox substituents and the L ligand in the process. The best results were obtained with complex trans-[RuCl2{PPh2(OEt)}{(R,R)-Ph-pybox}] (2c), which provided high conversion and enantioselectivity (up to 96% enantiomeric excess, e.e.) for the reduction of a variety of aromatic ketones, affording the (S)-benzylalcohols.

Keywords: alcohols; asymmetric catalysis; phosphinite ligands; phosphonite ligands; pybox; ruthenium; transfer hydrogenation.

MeSH terms

  • Acetophenones / chemistry
  • Catalysis
  • Coordination Complexes / chemistry
  • Crystallography, X-Ray
  • Hydrogenation
  • Isomerism
  • Ketones / chemistry*
  • Ligands
  • Oxazoles / chemistry*
  • Phosphines / chemistry
  • Phosphites / chemistry
  • Phosphorus Compounds / chemistry*
  • Pyridines / chemistry*
  • Ruthenium / chemistry*

Substances

  • (4'S,5'S)-2,6-bis(4'-(triisopropylsilyl)oxymethyl-5'-phenyl-1',3'-oxazolin-2'-yl)pyridine
  • Acetophenones
  • Coordination Complexes
  • Ketones
  • Ligands
  • Oxazoles
  • Phosphines
  • Phosphites
  • Phosphorus Compounds
  • Pyridines
  • Ruthenium
  • acetophenone