Synthesis of 2,3-Dihydrothiopyran-4-ones from 3-Oxo-1-pentene-4-ynes

3-Oxo-1-pentene-4-ynes were converted with sodium sulfide or hydrogensulfide to give 2,6-disubstituted 2,3-dihydrothiopyran-4-one derivatives. The starting materials were prepared in two steps from terminal alkynes and α,β-unsaturated aldehydes.