Trifluoromethanesulfonic acid has been discovered to be an excellent new solvent for promoting the direct elemental fluorination of aromatics. Fluorobenzene has been successfully fluorinated to a mixture of 1, 4-difluorobenzene (31%) and 1, 2-difluorobenzene (7%) in CFCl3–CF3SO3H (5%), but no further improvement is observed by the addition of boron trifluoride. When the reaction is carried out in only CFCl3, the main reaction ...
