Abstract
Several new chiral urea and thiourea ligands have been prepared by reaction of (1R,2R)-1,2-diaminocyclohexane with various organic isocyanates and isothiocyanates. These were used as ligands in the ruthenium catalysed enantioselective reduction of aromatic ketones by isopropanol. The reduction proceeded at room temperature using 2 mol% of ruthenium catalyst to give good yields of the (R)-alcohol with enantiomeric excesses of up to 83%. By contrast, the use of bis-urea ligands gave much lower enantioselectivities. Amino-thiourea ligands led to the (S)-alcohol with low enantiomeric excess.