Palladium(0)-based approach to functionalized C-glycopyranosides
About: This article is published in Journal of Organic Chemistry.The article was published on 1989-04-01. It has received 83 citations till now. The article focuses on the topics: Palladium.
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388 citations
TL;DR: The collective studies suggest that stereochemical control of the C-glycosides is dependent on the substrate and catalysts combination, as demonstrated by its use in the first total synthesis of the natural product salmochelin SX.
Abstract: A Ni-catalyzed Negishi cross-coupling approach to C-glycosides is described with an emphasis on C-aryl glycosides. The combination of NiCl2/PyBox in N,N'-dimethylimidazolidinone (DMI) enabled the synthesis of C-alkyl glycosides under mild reaction conditions. Moderate yields and beta-selectivities were obtained for C-glucosides, and good yields and high alpha-selectivities were the norm for C-mannosides. For C-aryl glycosides, reactions employing Ni(COD)2/(t)Bu-Terpy in N,N-dimethylformamide (DMF) were typically high yielding and provided C-glucosides with high beta-selectivities (1:>10 alpha:beta) and C-mannosides in moderate alpha-selectivities (3:1 alpha:beta); alpha-C-aryl glycosides could be obtained by the combination of Ni(COD)2/PyBox in DMF (>20:1 alpha:beta). The collective studies suggest that stereochemical control of the C-glycosides is dependent on the substrate and catalysts combination. The Negishi protocol displays excellent functional group tolerance, as demonstrated by its use in the first total synthesis of the natural product salmochelin SX.
203 citations
TL;DR: Glycals (or usually their O-substituted derivatives) are readily converted into 2,3-unsaturated glycosyl compounds with O-, C-, N-, S- or otherwise linked substituents at the anomeric position as discussed by the authors.
Abstract: Glycals (or usually their O-substituted derivatives) are readily converted into 2,3-unsaturated glycosyl compounds with O-, C-, N-, S- or otherwise linked substituents at the anomeric position. These products have been found to be useful for a range of synthetic purposes. In particular, the C-glycosidic compounds have served as readily available starting materials for the preparation of useful non-carbohydrate compounds. While these allylic rearrangement processes are usually conducted under the influence of Lewis acid catalysts, adaptations that involve activation of the allylic substituents of the starting glycals as leaving groups under neutral conditions have been developed. General features of the reactions are described as well as applications in synthesis and extensions of the basic processes.
146 citations
TL;DR: A review of recent developments in the use of promoters for the Ferrier rearrangement of O-, N-, C- and S-nucleophiles with glycals can be found in this paper.
121 citations
TL;DR: A palladium(O)-water soluble catalyst prepared in situ from palladium acetate and the sulfonated triphenyl phosphine P(C6H4-m-SO3Na)3 is an efficient catalyst for allylic substitution with various carbon and heteronucleophiles in an aqueous-organic medium, allowing a very easy separation of the product(s) and the recycling of the catalyst as discussed by the authors.
72 citations