Fig. 4
A Concerted nucleophilic aromatic substitution (CSNAr) of phenols with [18F]F−. B CSNAr via aryl fluorosulfonate intermediates. C Dibenzothiophene sulfoniums as leaving groups for aromatic 18F-fluorination. D Electrochemical radiofluorination. E Aryl umpolung strategy with the use of external oxidant. F Photoredox radiofluorination. EWG = electron-withdrawing group. EDG = electron-donating group. NCS = N-Chlorosuccinimide. DBTO = dibenzothiophene S-oxide. TFAA = trifluoroacetic anhydride. TfOH = triflic acid. PIDA = phenyliodine diacetate. PC = photocatalyst