Comparison of pathways to the versatile synthon of no‐carrier‐added 1‐bromo‐4‐[¹⁸F]fluorobenzene

The availability of no‐carrier‐added (n.c.a.) 1‐bromo‐4‐[ 18 F]fluorobenzene with high radiochemical yields is important for 18 F‐arylation reactions using metallo‐organic 4‐[ 18 F]fluorophenyl compounds (e.g. of lithium or magnesium) or Pd‐catalyzed coupling. In this study, different methods for the preparation of 1‐bromo‐4‐[ 18 F]fluorobenzene by nucleophilic aromatic substitution reactions using n.c.a. [ 18 F]fluoride were examined. Of six pathways compared, symmetrical bis ‐(4‐bromphenyl)iodonium bromide proved most useful to achieve the title compound in a direct, one‐step nucleophilic substitution with a radiochemical yield (RCY) of 65% within 10 min.