Application of Halide Molten Salts as Novel Reaction Media for O-Glycosidic Bond Formation

In this study we have explored the application of halide molten salts as reaction media for O-glycosidic bond formation under basic conditions and mild heating. Eighteen different room-temperature ionic liquids and molten salts, representing four different classes of cations (i.e. imidazolium, pyridinium, pyrrolidinium and ammonium), were screened in the glycosidation reaction of p-nitrophenol with aceto-bromo-alpha-D-galactose. 1-Butyl-4-methylimidazolium chloride (BMIM center dot Cl) gave the best results and was applied in the reactions of other phenolic substrates to give the products with up to 80% yields. All the reactions were highly selective to give the beta-anomers, and the molten salt BMIM center dot Cl could easily be reused with no apparent loss in activity.