Cobalt-Catalyzed Hydroglycosylation of Alkynes for the Synthesis of Vinyl α-C-Glycosides.

Herein we report a cobalt-catalyzed hydroglycosylation of terminal alkynes, employing bench-stable ortho-iodobiphenyl (oIB) substituted sulfides as glycosyl donors. This reaction occurs with high stereo- and regioselectivity to afford E-configured vinyl α-C-glycosides, a class of compounds nontrivial to access by previous methods. The use of a bis(oxazoline) ligand with bulky side chains is critical for the high selectivities observed. Aryl iodides have not been used previously as surrogates for alkyl (glycosyl) electrophiles in Co-H catalyzed reactions. The transformation features mild reaction conditions, simple reagents, and broad substrate scope. This method can be applied to the derivatization of bioactive compounds and the preparation of naturally occurring products. Mechanistic studies suggest this stereoconvergent process involves glycosyl radicals as key reaction intermediates.