Preparation of heptafluoronaphthyllithiums and -magnesiums: An unexpected difference in the reactivity of isomers C10F7H and C10F7Br towards organolithium and organomagnesium compounds

Significant differences in the reactivity of isomeric heptafluoronaphthalenes and bromoheptafluoronaphthalenes towards organolithium and organomagnesium compounds were found. Metalation of polyfluorinated naphthalenes 2-C10F7X (X = H, Br) occurs easily under the action of bases (BuLi, t-BuLi, LDA) as well as EtMgBr (X = Br) in ether. This fact was proven by 19F NMR spectroscopy and by trapping of 2-C10F7M (M = Li, MgBr, Mg(2-C10F7)) with electrophile ClSiMe3. The interaction of 1-C10F7Br with BuLi or EtMgBr proceeds in a similar way. In contrast to 2-C10F7H, isomeric 1-C10F7H is the less acidic substrate and undergoes only the nucleophilic alkyldefluorination when combined with BuLi or t-BuLi.