Reactions of Alk‐1‐enylxenonium(II) and Alk‐1‐ynylxenonium(II) Salts [RXe]Y with Bromides and Iodides in Anhydrous HF

The replacement of xenon(+) by iodine in reactions of alkenylxenonium(II) salts RCF=CFXe]Y (R = cis-C₂F₅, trans-H) and alkynylxenonium(II) salt C₃F₇C≡CXe]BF₄] with NaI in anhydrous HF (aHF) occurred regiospecifically. At −60 °C the substitution of xenon(+) by bromine in the perfluorinated salts cis-CF₃CF=CFXe]Y and trans-C₄F₉CF=CFXe]Y proceeded regio- and stereospecifically with NaBr in aHF, but at a higher temperature and after a longer time the treatment of cis-C₂F₅CF=CFXe]Y with NaBr, KBr, or NBu₄]Br in aHF gave mixtures of cisand trans-perfluorobut-1-enyl bromides. The reaction of C₃F₇C≡CXe]BF₄] with NaBr in aHF at −65 °C gave only 48 %, of C₃F₇C≡CBr and was accompanied by a mixture of bromine-containing related olefins. Reaction pathways to the main product are discussed.