Methyl 4-oxotetrahydro-2H-thiopyran-3-carboxylate as a CH-acid undergoes amild reactionwith acetylenic esters in the presence of triphenylphosphine to produce phosphorus ylides possessing thiopyran-4-one ring moiety. The resulted phosphorus ylides when heated in toluene aforded functionalized thiopyran derivatives through intramolecular Wittig reaction.
