Radical Functionalization of Thioglycosides in Aqueous Medium
A visible-light-mediated thiol-ene reaction is successfully operated in aqueous medium. Organic photoredox catalyst (9-mesityl-10-methylacridinum tetrafluoroborate) is used to initiate the radical process to generate thiyl radicals upon light irradiation. Two reaction pathways are discovered in different aqueous buffer system. Thiol-ene adduct is preferred in acidity reaction medium; while disulfide formation is found to be favored in basic reaction medium. Moreover, a visible-light-mediated modified Danishefsky-Wan desulfurization is used to convert thioglycoside to highly substituted tetrahydropyran ring.