Visible-Light-Mediated Metal/Base-Free Stereoselective <i>C</i>-Alkyl Glycosylation via EDA Complexes of Glycosyl Xanthates and NHC-Borane

Owing to the toxic reagent and high temperature required, the application of xanthate-based radical chemistry has been limited. To address these challenges, we report a metal- and base-free, photoinduced strategy for stereoselective <i>C</i>-alkyl glycosylation via electron donor-acceptor (EDA) complexes of glycosyl xanthates and N-heterocyclic carbene (NHC)-BH₃. This method generates glycosyl radicals under mild conditions, affording compatibility with a wide range of sugars and olefins to produce <i>C</i>-alkyl glycosides in good to excellent yields. Mechanistic studies confirmed the formation of EDA complexes and the involvement of radical intermediates, providing insights into the reaction pathway.