Abstract

Protonation of the highly reactive 1:1 intermediates produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates by 3,5-diphenyl-1   Hpyrazole2 Cl2 at room temperature to N -vinyl pyrazoles in fairly high yields. The reaction is fairly stereoselective. leads to vinyltriphenylphosphonium salts. The cation in these salts undergoes an addition reaction with the counter anion in CH yield the corresponding stabilized phosphorus ylides. Elimination of triphenylphosphine from the stabilized phosphorus ylides leads to the corresponding electron-poor