Dehydrative Glycosylation Enabled by a Comproportionation Reaction of 2‐Aryl‐1,3‐dithiane 1‐Oxide†

A new dehydrative glycosylation reaction has been established by capitalizing on the comproportionation reaction of 2‐aryl‐1,3‐dithiane 1‐oxides promoted by triflic anhydride (Tf₂O). By wedding the high potency of thiophilic promoter system with the step efficiency of dehydrative glycosylation, this reagent underwent facile intermolecular oxothio acetalization with C1‐hemiacetal donor to install a temporary leaving group, rendering a transient electrophilic center at the remote site to the anomeric position. The sulfenyl triflate tethered at the terminus concomitantly activated the sulfide intramolecularly to afford the oxocarbenium ion, thereby facilitating the title glycosylation. Aside from accommodating broad range functional groups and inactive hemiacetal substrates, the present activation protocol also proved expedient for 1,3‐diol protection. Most importantly, this method further provided a fresh perspective for the application of sulfur chemistry to carbohydrate chemistry.