Triphenylphosphine-Catalyzed Stereoselective Synthesis of Alkyl 3-(2-Naphthylsulfanyl)-2-propenoate from Alkyl Acetylenecarboxylates and 2-Naphthalenethiol

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and alkyl acetylenecarboxylates by 2-naphthalenethiol, leads to vinyltriphenylphosphonium salts, which undergo an addition-elimination reaction to produce the corresponding S-vinyl thioethers. The NMR spectra indicated that the compounds contained two stereoisomers for each S-vinyl thioether; their ratio was determined on the basis of 1H NMR spectra. The reaction is fairly stereoselective.