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

Hydroalumination of phenylthioacetylenes with the Zweifel's 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. (C) 2001 Elsevier Science Ltd. All rights reserved.