Electrochemical radiofluorination. Part 2. Anodic monofluorination of substituted benzenes using [18F]fluoride.
Electrochemical fluorination of various monosubstituted aromatic compounds was performed with [18F]fluoride using potentiostatic anodic oxidation on platinum electrodes in an undivided cell in acetonitrile with a mixture of Et(3)N.3HF/Et(3)N.HCl as electrolyte. Maximum radiochemical yields were obtained after a charge of 50C passed the solution. The results showed a clear dependence of the radiochemical yields on the oxidation potentials E(1/2) of the substrates as a consequence of different substituents namely CH(3)CO-, F-, Cl-, Br- and tert.-Butyl. With increasing E(1/2), the fluorination yields decreased from 7.9% (tert.-butylbenzene) to 1.5% (acetophenone). The ratio between F-for-X substitution and F-for-H substitution correlated with the bond energies of the C-X bond. With higher bond energies, less X-substitution was observed.
Reischl
G
G
PET Zentrum, Radiopharmazie, Universitätsklinikum Tübingen, Röntgenweg 15, D-72076 Tübingen, Germany. gerald.reischl@uni-tuebingen.de
Kienzle
G J
GJ
Machulla
H-J
HJ
D001554:Benzene / Q000737:chemistry; D004563:Electrochemistry / Q000379:methods*; D005459:Fluorides / Q000138:chemical synthesis / Q000737:chemistry; D005462:Fluorine Radioisotopes / Q000737:chemistry*; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis* / Q000737:chemistry; D006845:Hydrocarbons, Fluorinated / Q000138:chemical synthesis* / Q000737:chemistry; D007553:Isotope Labeling / Q000379:methods*; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000737:chemistry
D005462:Fluorine Radioisotopes; D006841:Hydrocarbons, Aromatic; D006845:Hydrocarbons, Fluorinated; D019275:Radiopharmaceuticals; D001554:Benzene; D005459:Fluorides