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- Title
Promotion of a Reaction by Cooling: Stereoselective 1,2‐<italic>cis</italic>‐α‐Thioglycoconjugation by Thiol‐Ene Coupling at −80 °C.
- Authors
Eszenyi, Dániel; Kelemen, Viktor; Balogh, Fanny; Bege, Miklós; Csávás, Magdolna; Herczegh, Pál; Borbás, Anikó
- Abstract
Abstract: The photoinitiated thiol‐ene coupling reactions of 2‐substituted glycals were studied as a generally applicable strategy for stereoselective 1,2‐<italic>cis</italic>‐α‐thioconjugation. Although all glycals reacted with full α‐selectivity, the efficacy of the reactions varied in a broad range depending on their configuration and glycals bearing axial acetoxy substituents reacted with very low efficacy at room temperature. The study revealed that the reaction progress could be promoted by cooling and inhibited by heating. At −80 °C, the equilibrium of the rapidly reversible addition of the thiyl radical to alkenes is shifted almost completely toward products, leading to efficient addition reactions. By exploiting this unique temperature effect a series of α‐thio‐ l‐fucosides, ‐ d‐galactosides, and d‐GlcNAc derivatives were prepared with high efficacy and complete stereoselectivity.
- Subjects
GLYCALS; CYCLIC ethers; ENOL ethers; THIYL radicals; STEREOSELECTIVE reactions
- Publication
Chemistry - A European Journal, 2018, Vol 24, Issue 18, p4532
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201800668