Asymmetric Hydrogenation of Vinylthioethers: Access to Optically Active 1,5-Benzothiazepine Derivatives

A novel asymmetric hydrogenation of vinylthioethers was developed using a ruthenium(II) NHC complex. This method provides an efficient approach to optically active 1,5-benzothiazepines featuring stereocenters with C-S bonds. Excellent enantioselectivities (up to 95%ee) and high yields (up to 99%) were obtained for a variety of substrates bearing a range of useful functional groups. Moreover, this methodology could be directly applied to the synthesis of the antidepressant drug R-(-)-thiazesim.