Synthesis of unsymmetrically 2,6-disubstituted 2,3-dihydrothiopyran-4-ones

A series of 2,3-dihydrothiopyran-4-one derivatives with unequal substituents in the 2- and 6-position have been prepared by double conjugate addition of sulfide to enynones. These starting materials were accessed in two steps from terminal alkynes and α,β-unsaturated aldehydes.