PREPARATION OF THE E AND Z-HEPTAFLUOROBUTENYL-2-ZINC REAGENT BY ZINC-INDUCED DEHALOGENATION METALATION OF 2,2-DIBROMOOCTAFLUOROBUTANE

The AlCl3-catalyzed isomerization of CF3CFBrCFBrCF3 afforded CF3CF2CBr2CF3, which upon treatment with 2 equiv. zinc in DMF underwent dehalogenation/metallation to afford a 1:1 mixture of E- and Z-CF3CF=C(ZnX)CF3 in 96% F-19 NMR yield. The zinc reagent exhibited poor thermal stability in DMF and completely decomposed by a beta-elimination route in 24 h at 60-degrees-C. However, the zinc reagent prepared from E- and Z-CF3CF=CICF3 in triglyme showed enhanced thermal stability and gave E- and Z-p-NO2C6H4C(CF3)=CFCF3 in a palladium-catalyzed coupling reaction with p-NO2C6H4I.