Fluorinated apolar solvents

The reaction cannot be performed in fully fluorinated apolar solvents such as octafluorotoluene, which is probably because of missing polarization of fluorine that is necessary to attack the aromatic system. Polar solvents such as methanol or acetonitrile provide better environments for fluorination [308]. Formic acid as a protic solvent gives even better results and is also quite inert as this small molecule has no labile site for fluorine attack [274]. 

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