CHEMISTRY OF POLYFLUOROCARBANIONS .1. NUCLEOPHILIC IODOFLUORINATION OF PERFLUOROALKYL VINYL ETHERS

Nucleophilic iodofluorination of perfluorovinyl methyl (I) and perfluorovinyl propyl (II) ethers by iodine chloride in nitrobenzene or sulfolan afforded 1-iodoperfluoro-1-methoxyethane (III) and 1-iodoperfluoro-1-propoxyethane in yields of 65 and 77%, respectively. In addition to compound (III), the reaction of perfluorovinyl methyl ether afforded two side products: 1-iodo-2-chloroperfluoro-1-methoxyethane and 2-iodo-1-chloroperfluoro-1-methoxyethane. The latter products are formed via a radical reaction, which takes place under drastic conditions. On the basis of quantum chemical calculations of (I), (II), and the two anions formed from (I), CF3OCFCF3 (VI) and CF3OCF2CF2, (VII), it is proposed that nucleophilic iodofluorination of perfluoroalkyl vinyl ethers involves the formation of thermodynamically more stable anions. The higher reactivity of (I) compared with (II) is in accord with the energy of the lowest unoccupied molecular orbitals and the charge density on the CF2 carbon atoms. F-19 NMR spectra of the synthesized products are shown.