Microwave-induced stereoselective conversion of dialkyl 2-(1,1,3-trioxo-1,3-dihydro-2H-1,2-benzisothiazol-2-yl)-3-(triphenylphosphoranylidene) succinates to dialkyl 2-(1,1,3-trioxo-1,3-dihydro-2H-1,2-benzisothiazol-2-yl)-2-butendioates in the presenc

摘要

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 CH2Cl2 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.