Stereoselective Formation of Z- or E-Vinyl Thioethers from Arylthiols and Acetylenes under Transition-Metal-Free Conditions

Vinyl sulfide formation with good yield and high regio‐ and stereoselectivities from thiols and acetylenes under transition‐metal‐free conditions is described. Potassium phosphate was used as an effective additive to enhance the reaction yield and selectivity. Z‐Vinyl sulfides were predominately formed in the presence of potassium phosphate, whereas E‐vinyl sulfides were formed under solvent‐ and base‐free conditions. Z‐Vinyl sulfides were formed in good yields and with high regio‐ and stereoselectivities when potassium phosphate was used as base in N‐methyl‐2‐pyrrolidone. E‐Vinyl sulfides were the major products when the reaction was carried out under solvent‐free conditions without any base.