Article

Projet
Conception, synthèse et étude de nouveaux hétérocycles azotés d'intérêts biologiques  
Martine DEMEUNYNCKIsabelle BAUSSANNE,   
Titre
Investigation of the Pyridinium Ylide—Alkyne Cycloaddition as a Fluorogenic Coupling Reaction  
[Full paper ]
Auteurs
S. Bonte, I.O. Ghinea, R. Dinica, I. Baussanne, M. Demeunynck
Edition
Molecules 2016, 21, 332
Année
2016
Résumé
The cycloaddition of pyridinium ylides with alkynes was investigated under mild conditions. A series of 13 pyridinium salts was prepared by alkylation of 4-substituted pyridines. Their reactivity with propiolic ester or amide in various reaction conditions (different temperatures, solvents, added bases) was studied, and 11 indolizines, with three points of structural variation, were, thus, isolated and characterized. The highest yields were obtained when electron-withdrawing groups were present on both the pyridinium ylide, generated in situ from the corresponding pyridinium salt, and the alkyne (X, Z = ester, amide, CN, carbonyl, etc.). Electron-withdrawing substituents, lowering the acid dissociation constant (pKa) of the pyridinium salts, allow the cycloaddition to proceed at pH 7.5 in aqueous buffers at room temperature.