Allylic sulfides add to alkynes in the presence of nickel complexes efficiently to afford thio-1,4-dienes regio- and stereoselectively. Functionalgroups such as alkoxy, siloxy, hydroxy, carboalkoxy, chloro, and cyano groups are tolerated. A mechanism that involves a
-allyl nickelintermediate is proposed on the basis of isolation of
-allyl complexes and distribution of products in the reactions of
- or
-methylated allylsulfide.