SYNTHESIS OF (E)-VINYLIC TELLURIDES AND THEIR TRANSFORMATION INTO ALPHA,BETA-UNSATURATED ESTERS AND CARBOXYLIC-ACIDS

Zirconium alkenyls and dienyls of E configuration, obtained by the hyd rozirconation of alkynes or conjugated enynes containing a terminal tr iple bond undergo the Zr/Te exchange reaction by treatment with C4H9Te Br or C(4)H(9)Tel in THF at -78 degrees C. Tie Zr/Te exchange reaction proceeds with total retention of configuration and with complete ster eoselectivity at the carbon 1, furnishing (E)-butyltelluro alkenes (64 - 86% yields) and (E)-1-butylteluro-1,3-dienes (68 - 75% yields). Vin ylic tellurides were transformed into alpha,beta- unsaturated esters a nd carboxylic acids with total retention of the regio- and stereochemi stry via vinyl lithium intermediates.