Hydroalumination of phenylthioacetylenes. Synthesis and reactions of (Z)- and (E)-1-butyltelluro-1-phenylthio-1-alkenes

Hydroalumination of phenylthioacetylenes with the Zweifelʹs reagent as reducing agent followed by the addition of C4H9TeBr afforded (Z)-telluro(thio)ketene acetals (Z >80–93%). The (E)-isomers were obtained with 100% stereoselectivity by reduction of thioacetylenes with DIBAL-H, followed by the addition of n-BuLi and subsequent treatment with C4H9TeBr. Reaction of the (E)-telluro(thio)ketene acetals with n-BuLi followed by the addition of valeraldehyde afforded the (Z)-phenylthio allylic alcohol as the main product and traces of the (E)-isomer, while the mixture of (Z)- and (E)-telluro(thio)ketene acetals under similar reaction conditions gave the (E)-phenylthio allylic alcohol exclusively.