The introduction of F into aromatic organic molecules is generally via two methods,

1.       The Balz-Schiemann reaction of diazonium tetrafluoroborates

2.       Halogen exchange

The former process produces large quantities of waste and has poor atom economy, and BF4- has recently been replaced by a process involving HF.  However this also produces lots of inorganic waste (NaF, NH4F salts)

The obvious process to prepare fluorobenzene would be from benzene, HF and oxygen, when water would be the only by-product.  The key is to find a catalyst – a metal fluoride – capable of oxidising an aromatic C-H bond and being regenerated by oxygen (and HF).  It has now been shown by chemists from DuPont (Subramanian M A et al, Science, 2002, 297, 1665) that copper II fluoride is a useful catalyst for this transformation at temperatures above 500oC.  Catalyst regeneration by O2/HF was possible.  The methodology has been applied to other F-aromatics (US Patent 6, 166, 273, 2000).