A Visible‐Light‐Promoted <i>O</i>‐Glycosylation with a Thioglycoside Donor

Abstract

Abstract Visible‐light irradiation of 4‐ p ‐methoxyphenyl‐3‐butenylthioglucoside donors in the presence of Umemoto's reagent and alcohol acceptors serves as a mild approach to O‐glycosylation. Visible‐light photocatalysts are not required for activation, and alkyl‐ and arylthioglycosides not bearing the p ‐methoxystyrene are inert to these conditions. Experimental and computational evidence for an intervening electron donor–acceptor complex, which is necessary for reactivity, is provided. Yields with primary, secondary, and tertiary alcohol acceptors range from moderate to high. Complete β‐selectivity can be attained through neighboring‐group participation.