Fluorine-19 NMR spectroscopy of polyhalonaphthalenes. Part II polychloropolyfluoronaphthalenes via nucleophilic fluoride dechlorination
作者:Raymond S. Matthews
DOI:10.1016/s0022-1139(00)85005-8
日期:1990.12
Six new polychloropolyfluoronaphthalenes have been identified by F-19 NMR whose empirical formulae are C10 Cl8-n F(n) where n is 5 and 6 i.e. two trichloropentafluoronaphthalenes and four dichlorohexafluoronaphthalenes:- 1,3,8-trichloro-2,4,5,6,7-pentafluoronaphthalene, 1,3,6-trichloro-2,4,5,7,8-pentafluoronaphthalene, 1,3-dichloro-2,4,5,6,7,8-hexafluoronaphthalene, 1,8-dichloro-2,3,4,5,6,7-hexafluoronaphthalene, 1,6-dichloro-2,3,4,5,7,8-hexafluoronaphthalene and 2,7-dichloro-1,3,4,5,6,8-hexafluoronaphthalene. In the partly fluorinated compounds such as 1,3,6,8-tetrachloro-2,4,5,7-tetrafluoronaphthalene, nucleophilic fluoride dechlorination occurs at both-alpha-and-beta-positions. Initial substitution in octachloronaphthalene is more selective and occurs predominantly at the alpha-position; both subsequent exchanges occur at sites two carbons away from the initial site. The results support the idea that the transition state is stabilised by chlorine at the sites of electron density, ortho and para to the site of nucleophilic attack.