Hydrochalcogenation of phenylthioacetylenes. Synthesis of mixed (Z)-trisubstituted 1,2-bis(organylchalcogeno)-1-alkenes

The treatment of 1-phenylthioacetylenes with phenylselenolate and butyl or phenyltellurolate anions generated by the reaction of the corresponding dichalcogenide with NaBH4 in aqueous ethanol results in the formation of mixed 1,2-bis(organylchalcogeno)-1-alkenes of Z configuration. The phenylthio group acts as a directing and activating group for the nucleophilic addition of the chalcogenate anions