Scheme 2. Ruthenium-Catalyzed Asymmetric Hydrogenation of Benzothiophene 1,1-Dioxides.

Unless otherwise noted, reactions were conducted with 3 (0.3 mmol), C3 (0.0015 mmol, 0.5 mol %), and NaOt-Bu (0.02 mmol 6.7 mol %) under 5 bar of H₂ in toluene (2.0 mL) at 25 °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 30 bar of H₂ at 0 °C.