Ruthenium Catalyzed Stereo/Chemo/Regioselective One-Pot Synthesis of C(2)-C(3) Unsaturated and α-D-Mannopyranosyl Sulfones

An efficient and divergent approach to C(2)-C(3) unsaturated glycosyl and a-p-mannopyranosyl sulfones has been developed via ruthenium-promoted direct glycosylation, oxidation, and dihydroxylation from glycal in one-pot. The presence of stoichiometric amounts of NaIO4 and in situ generation of RuO4 from a RuCl3-NaIO4 reagent system were crucial for chemoselective oxidation of sulfide in the presence of an olefin moiety. The dual-role of ruthenium in sequential glycosylation-oxidation-dihydroxylation is amenable to a wide range of thio acceptors to access alpha-n-mannopyranosyl sulfones in good yields with high regioselectivity.