Organic Electrode Reactions - Fundamentals and Applications of Organic Electrochemistry - page 158

cell is therefore not always necessary for
fluorination under such conditions.
In aprotic solvent, F − becomes more
nucleophilic, but the reactivity of F − is quite
sensitive to the water content of the electrolysis
system because a hydrated F − is a weak
nucleophile. Drying of both the solvent and
electrolyte is therefore necessary to optimize
the formation of fluorinated products.
A few examples are given below, and more
examples have been reported in the literature.
5.7.1 Electrochemical Fluorination of
Aromatic Rings
Aromatic compounds such as benzene,
substituted benzenes and naphthalene are
selectively fluorinated by constant potential
anodic oxidation in Et 4 N-3HF/MeCN or
Et 4 NF-4HF without solvent ( Eq. 5.20 ) [68,69].
Fluorination proceeds via addition with two
fluoride ions followed by elimination of HF to
provide monofluorinated aromatic compounds.
Notably, ipso -substitution with fluorine also
takes place in high yield, as shown in Eq. 5.21 .