347381-83-3Relevant academic research and scientific papers
Remote dipole effects as a means to accelerate [Ru(amino alcohol)]catalyzed transfer hydrogenation of ketones
Nordin, Sofia J. M.,Roth, Peter,Tarnai, Tibor,Alonso, Diego A.,Brandt, Peter,Andersson, Pher G.
, p. 1431 - 1436 (2007/10/03)
A new generation of 2-azanorbornyl amino alcohol ligands for the catalytic transfer hydrogenation reaction of aromatic ketones was synthesized. Extremely active catalysts were formed by introducing a ketal functionality at the rear end of the ligand. Acetophenone was reduced in 96% ee at low catalyst loading, substrate to catalyst ratio, S/C 5000, within 90 minutes with isopropyl alcohol as the hydrogen donor. It was found that the dioxolane substituent in the ligand increased the turnover frequency, TOF50, from 1050 h-1 to 3000 h-1 at an S/C ratio of 1000. Introduction of a methyl group at the carbinol carbon resulted in TOF50 as high as 8500 h-1. Transfer hydrogenation of a range of aromatic ketones was evaluated and found to reach completion within 30 minutes at room temperature, and excellent enantioselectivity, up to 99% ee, was obtained. A possible explanation for the enhanced activity was provided by density functional calculations, which showed that the presence of a remote dipole in the ligand lowered the transition state energy.
