Study Of Gd（OTf）₃ Catalyzed Preparation Of 2,3-unsaturated Glycosides By Ferrier Rearrangement

2,3-unsaturated glycosides are a kind of important intermediate, they can be used to synthesize natural products like nucleoside, glycopeptide, oligosaccharide, etc. Type I Ferrier rearrangement is an efficient method for the synthesis of 2,3-unsaturated glycosides and capable of giving products in good yields and high anomeric stereoselectivities. Therefore, this reaction has important applications in the synthesis of glycosides.Many kinds of catalysts have been reported to promote type I Ferrier rearrangement, like Lewis acids, Bronsted acids, oxidants, etc. According to the former literatures, it is found that types of catalysts have great effects on this reaction. Some catalysts have a lot of disadvantages: reaction conditions are not mild, the price is high, poor anomeric stereoselectivity, etc. Therefore, find cheap and efficient catalysts will have great significance.Due to their unique properties and high catalytic activities, rare earth metal catalysts have extensive applications in the area of chemistry. During the study, we found Gd（OTf）₃ is a highly efficient catalyst for type I Ferrier rearrangement, so Gd（OTf）₃ catalyst system was established and we used it to study on type I Ferrier rearrangement.By using Gd（OTf）₃ as the catalyst, a series of 2,3-unsaturated O-, S-, N-, and Cglycosides were obtained from 3,4,6-tri-O-acetyl-D-glucal, 3,4,6-tri-O-benzyl-D- glucal and 3,4-di-O-acetyl-6-deoxy-L-glucal. This catalytic system have mild reaction condition, high efficience and good anomeric stereoselectivity. Furthmore, we tried to use Grignard reagent and aromatic nitrogenous heterocyclic compounds as nucleophiles for Ferrier rearrangement, and the results have been analyzed and discussed.