Nucleophilic aromatic substitution (SNAr) is widely used by organic chemists to functionalize aromatic molecules, and it is the most commonly used method to generate arenes that contain F-18 for use in positron-emission tomography (PET) imaging(1). A wide range of nucleophiles exhibit SNAr reactivity, and the operational simplicity of the reaction means that the transformation can be conducted reliably and on large scales(2). During SNAr, attack of a nucleophile at a carbon atom bearing a 'leaving group' leads to a negatively charged intermediate called a Meisenheimer complex. Only arenes with electron-withdrawing substituents can sufficiently stabilize the resulting build-up of negative charge during Meisenheimer complex formation, limiting the scope of SNAr reactions: the most common SNAr substrates contain strong p-acceptors in the ortho and/or para position(s)(3.) Here we present an unusual concerted nucleophilic aromatic substitution reaction (CSNAr) that is not limited to electron-poor arenes, because it does not proceed via a Meisenheimer intermediate. We show a phenol deoxyfluorination reaction for which CSNAr is favoured over a stepwise displacement. Mechanistic insights enabled us to develop a functional-group-tolerant F-18-deoxyfluorination reaction of phenols, which can be used to synthesize F-18-PET probes. Selective F-18 introduction, without the need for the common, but cumbersome, azeotropic drying of F-18, can now be accomplished from phenols as starting materials, and provides access to F-18-labelled compounds not accessible through conventional chemistry.