18F‐Radiolabeling of Aromatic Compounds Using Triarylsulfonium Salts

A new method for the 18F‐radiolabeling of aromatic compounds based on the aromatic nucleophilic substitution (SNAr) reaction using triarylsulfonium salts has been developed. Experiments and DFT calculations indicated that sulfonium ions have the potential to be optimized for labeling nonactivated and deactivated aryl rings that have Hammett σPsubstituent constants greater than –0.170. This method is applicable to a range of halogen‐substituted aryl systems including nonactivated and deactivated aryl rings. In particular, the high radiochemical yield of [18F]‐4‐fluoroiodobenzene from precursor 1arepresents a ready source of compound 1bfor subsequent use in palladium‐catalyzed C–H activation/C–C bond‐forming reactions.