Regioselectivity of fluorine substitution by alkoxides on unsymmetrical difluoroarenes

An efficient approach to unsymmetrical halogenated resorcinol diethers has been developed. This synthesis consists of two subsequent nucleophilic aromatic substitutions (SNAr) of unsymmetrical difluoroarenes by alkoxides. The novelty of this approach is its control of regioselectivity during the first SNAr, which occurs at room temperature. Interestingly, the reactivity of competing fluorines was correlated to their chemical shift in 19F NMR.