Silylium-Ion-Initiated Disulfidation of Internal Alkynes With Disulfides

A two-component protocol for the trans-selective addition of diaryl disulfides across internal alkynes is reported. The silylium-ion initiator converts the disulfide reagent into a silylated sulfonium ion and, as such, into a sulfenium-ion source. A subsequent transfer of that sulfur electrophile to the C≡C triple bond leads to the formation of a thiirenium ion. The ring opening of this intermediate by the disulfide as a sulfur nucleophile yields the disulfidation (bisthiolation) product with release of another sulfenium ion. The resulting 1,2-bis(arylthio)-substituted alkene derivatives can be oxidized to the corresponding sulfoxides and sulfones or further engaged in regioselective nickel-catalyzed cross-coupling reactions.