for the synthesis of 2,3-unsaturated C-glycosides. Various nucleophiles such as allyl trimethylsilane, triethylsilane, trimethylsilyl cyanide, trimethylsilyl azide and heterocycles such as thiophene and furan reacted smoothly with glycals in the presence of catalytic amount of ruthenium trichloride under mild reaction conditions.
Iodine-Catalyzed Stereoselective Synthesis of Allylglycosides, Glycosyl Cyanides and Glycosyl azides
作者:J. S. Yadav、B. V. S. Reddy、C. Venkateshwar Rao、Pratap. K. Chand、A. R. Prasad
DOI:10.1055/s-2001-17438
日期:——
Iodine efficiently catalyzes the glycosidation of glycals with allyltrimethylsilane, trimethylsilyl cyanide and trimethylsilyl azide in dichloromethane at ambient temperature to afford the corresponding 2,3-unsaturated allyl glycosides, glycosyl cyanides and glycosyl azides in excellent yields with high α-selectivity.
InBr3-Catalyzed Ferrier Rearrangement: An Efficient Synthesis of C-Pseudoglycals
作者:J. S. Yadav、B. V. Subba Reddy
DOI:10.1055/s-2002-20968
日期:——
Glycals react smoothly with silyl nucleophiles such as allyltrimethylsilane, trimethylsilyl cyanide and trimethylsilyl azide in the presence of a catalytic amount of indium tribromide to give the corresponding 2,3-unsaturated allyl glycosides, glycosyl cyanides and glycosyl azides in excellent yields with high α-selectivity.
The use of ultrastable Y zeolites in the Ferrier rearrangement of acetylated and benzylated glycals
作者:Pieter Levecque、David W. Gammon、Pierre Jacobs、Dirk De Vos、Bert Sels
DOI:10.1039/b921051b
日期:——
The Ferrier rearrangement of a selection of protected glycals was successfully performed using a commercially available H-USY zeolite CBV-720 as catalyst, selected after screening a range of similar catalysts. By incorporating either alcohols, thiophenol, trimethylsilyl azide or allyltrimethylsilane in the reaction it was shown that a range of O-, S-, N- and C-glycosides could be formed. With benzylated glucal and galactal in particular, use of the CBV-720 catalyst led to significantly higher yields of the 2,3-dehydroglycosides than previously reported.
High selectivity in heteroconjugate addition for C—C bond formation with complete syndiastereoselection has been attributed to the chelation effect between the α-oxygen atom of the substrate and the nucleophile anions through metal cations. Herein is described a new method exhibiting antidiastereoselection based on a different chelation effect caused by the ligands on the β-carbon atom to the heteroolefin