Highly Chemo- and Enantioselective Rh-Catalyzed Hydrogenation of β-Sulfonyl-α,β-unsaturated Ketones: Access to Chiral γ-Ketosulfones.

Rh-catalyzed highly chemo- and enantioselective hydrogenation of β-sulfonyl-α,β-unsaturated ketones was first successfully developed. Remarkably, a variety of enantioenriched γ-ketosulfones were generated in good to high yields with excellent chemo/enantioselectivities (82-99% yields, >99:1 chemoselectivity, 88 to >99% ee). Moreover, the gram-scale asymmetric hydrogenation was carried out smoothly in 97% yield and 97% ee. Preliminary DFT computations furnished a reasonable explanation for the high chemoselectivity and enantioselectivity.