Abstract

Protonation of the highly reactive 1:1 intermediates produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates by saccharin leads to vinyltriphenylphosphonium salts, which undergo an addition reaction with a counter anion in CH 2 Cl 2 at r.t. to produce the corresponding stabilized phosphorus ylides. Silica-gel powder was found to catalyze the stereoselective conversion of the stabilized phosphorus ylides to the corresponding electron-poor N-vinylated isothiazoles in solvent-free conditions under thermal and microwave irradiation in fairly good yields.