Triphenylphosphine-catalyzed preparation of sterically congested, electron-poor N-vinylimidazole derivatives from acetylenic esters and imidazole-containing NH-acids

چکیده مقاله

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and alkyl acetylenecarboxylates (or ethyl 3-phenyl-2-propynoate), by azathioprine or imidazole leads to vinyltriphenylphosphonium salts, which undergo a Michael addition reaction with a conjugate base to produce phosphorus ylides. Dipotassium hydrogen phosphate, potassium dihydrogen phosphate, and potassium iodide were found to catalyze the conversion of the phosphorus ylides to electron-poor N-vinyl imidazoles in solvent-free conditions under thermal (90 °C, 1 h) conditions. The structural analysis of the products indicated that the reaction is regio- and stereoselective. © Taylor & Francis Group, LLC.