SM（OTF）₃as The Catalyst For Type Ⅰ Ferrier Rearrangement Research Methodology

Alkyl and aryl2,3-unsaturated glycosides are capable of versatile chemicaltransformations, therefore they are important chiral intermediates in the synthesis ofbiologically active molecules and new functional materials. Ferrier rearrangement isan efficient and facile reaction for the synthesis of2,3-unsaturated glycopyranosides.A variety of reagents have been used to promote this reaction, including Bronstedacids, Lewis acids, as well as oxidants. However, some of these reaction systemssufferred from the disadvantages in terms of large excess of nucleophile,stiochiometric amounts of catalyst, harsh reaction conditions, which leading toextensive work up.Therefore, there still is of interest to find new efficient catalyst for milder andmore efficient synthetic process with good anomeric selectivity by usingstiochiometric amount of nucleophile under low catalyst load.In recent years, due totheir special properties and high catalytic activity, lanthanide elements as catalysthave got more and more application. For the reported lanthanides which have beenemployed as catalyst in Ferrier Rearrangement, there can be mentioned Dy(OTf)3,Er(OTf)3, and Yb(OTf)3, etc. In our continuing efforts to search for more efficientcatalyst for Ferrier Rearrangement, we found Sm(OTf)3is a highly efficient catalystfor our purposes.By using Sm(OTf)3as the catalyst, synthesis of2,3-unsaturated-glucosides has been performed. A series of2,3-unsaturated glucosides were obtained from3,4,6-tri-O-acetyl–D-glucal or3,4-Di-O-acetyl-6-deoxy-L-glucal under mild reactionconditions in good yield and high anomeric selectivity. It was found that under certainconditions, reaction of glucal with thiol leads to temperature-dependent formation ofC-1-S and C-3-S product. A temperature-dependent profile of the yield of these twoproducts is given.