Copper(ii)-catalyzed stereoselective 1,2-addition vs. Ferrier glycosylation of "armed" and "disarmed" glycal donors.

Selective activation of "armed' and ''disarmed" glycal donors enabling the stereo-controlled glycosylations by employing Cu(ii)-catalyst as the promoter has been realized. The distinctive stereochemical outcome in the process is mainly influenced by the presence of diverse protecting groups on the donor and the solvent system employed. The protocol is compatible with a variety of aglycones including carbohydrates, amino acids, and natural products to access deoxy-glycosides and glycoconjugates with high α-anomeric selectivity. Notably, the synthetic practicality of the method is amply verified for the stereoselective assembling of trisaccharides comprising 2-deoxy components. Mechanistic studies involving deuterated experiments validate the syn-diastereoselective 1,2-addition of acceptors on the double bond of armed donors.

Visible-light activated metal catalyst-free vicinal diazidation of olefins with sulfonium iodate(i) species.

A visible light-induced vicinal diazidation of various alkenes using stable sulfonium bis(acetoxy)iodate(i) and sodium azide as a radical precursor is described. The trimethylsulfonium [bis(azido)iodate(i)] species, intrinsically generated in situ, demonstrated unprecedented reactivity toward C[double bond, length as m-dash]C π bond-promoting selective azidation under photochemical conditions without any photoredox or metal catalyst. The visible-light stimulated diazidation reaction provides a convenient and straightforward approach to highly prevalent vicinal nitrogen scaffolds of myriad therapeutic importance.

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 α-D-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 α-D-mannopyranosyl sulfones in good yields with high regioselectivity.

Ruthenium catalyzed synthesis of 2,3-unsaturated C-glycosides from glycals.

A highly efficient and convenient C-glycosylation method was developed using ruthenium(III) chloride for the synthesis of 2,3-unsaturated C-glycosides. Various nucleophiles such as allyl trimethylsilane, triethylsilane, trimethylsilyl cyanide, trimethylsilyl azide and heterocycles such as thiophene and furan reacted smoothly with glycals in the presence of catalytic amount of ruthenium trichloride under mild reaction conditions.