Electron-deficient acetylenic esters have proven to be very versatile reagent for the preparation of stable phosphorus ylides and many different products containing heterocycles can be synthesized [1,2]. Indeed, several series of heterocyclic compounds possessing a bridgehead thiazole or thiazine moiety play a vital role in many biological activities [3]. The present study aims to test the reactivity of DMAD towards imidazolidine-2-thione, pyrimidine-2-thione and N-phenylthiourea in the presence of triphenylphosphine. The new stable phosphorus ylides have been prepared in excellent yields by the three-components approach starting with activated electron-deficient acetylenic esters (dimethyl and diethyl acetylenedicarboxylate (DMAD and DEAD)), and imidazolidine-2-thione or pyrimidine-2-thione or N-phenylthiourea in the presence of triphenylphosphine. In some cases these ylides were cyclized to dihydro pyrimido thiazine, thioxoimidazolidine and thioxo tetrahydro pyrimidine derivatives. The FT-IR, 1H-NMR, 13C-NMR spectra confirm the structure of compounds.

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