Scheme 3. Enantioselective Hydrogenation of Ketones Catalyzed by Ru(II)-NHC-Diamine Complexes.

Unless otherwise noted, reactions were carried out with 5 (1.0 mmol), C4 (0.0003 mmol, 0.03 mol %), and NaOt-Bu (0.02 mmol, 2.0 mol %) under 5–10 bar of H₂ and in i-PrOH (1.0 mL) at 22 °C for 24 h. Isolated yields after column chromatography are reported. The e.r. values were determined by HPLC analysis using a chiral stationary phase.

Using 0.05 mol % of C4.

Using 0.5 mol % of C4.