Asymmetric Transfer Hydrogenation of Acetophenone Promoted by Chitosan Ester Ruthenium Complex

The catalytic properties of the catalyst generated in situ from the reaction of Ru(II) compounds with chitosan based ligands were evaluated in the asymmetric transfer hydrogenation of acetophenone using isopropanol or sodium formate as hydrogen source. The effects of reaction time, temperature and the dosage of THF on the performance of the catalyst were evaluated. The O-stearoyl chitosan (SCS) is in the form of micelles with the average size of 213 nm in i-PrOH/THF solution. Using i-PrOH as hydrogen source, the ee value of 1-phenylethanol is up to 62.9%. The dosage of THF strongly affected the catalytic activity. The catalytic activity (TOF) is up to 30.4 h(-1) at the volume ratio of i-PrOH to THF being 1 : 1. The TOF increased with the increase of the temperature. At 100 degrees C the TOF is up to 48.5 h(-1). While using HCOONa as the hydrogen source, the TOF and ee values of 1-phenylethanol are 29.4 h(-1) and 53.0%, respectively.