Koenigs-Knorr Glycosylation Reaction Catalyzed by Trimethylsilyl Trifluoromethanesulfonate.

The discovery that traditional silver(I)-oxide-promoted glycosidations of glycosyl bromides (Koenigs-Knorr reaction) can be greatly accelerated in the presence of catalytic trimethylsilyl trifluoromethanesulfonate (TMSOTf) is reported. The reaction conditions are very mild that allowed for maintaining a practically neutral pH and, at the same time, providing high rates and excellent glycosylation yields. In addition, unusual reactivity trends among a series of differentially protected glycosyl bromides were documented. In particular, benzoylated α-bromides were much more reactive than their benzylated counterparts under these conditions.