for the preparation of pharmaceuticals, pesticides, and liquid crystals. The conversion of diazonium salts is a well established route to aryl fluorides. Thus, anilines are precursors to aryl fluorides. In the classic Schiemann reaction, tetrafluoroborate is the fluoride donor:
:In some cases, the fluoride salt is used:
:

Many commercial aryl fluorides are produced from aryl chlorides by the Halex process.