Process for introducing fluorine atoms into aromatic rings by nucleophilic exchange

Claim 1

In the preparation of an aromatic ring-fluorinated compound by nucleophilic exchange between an educt and potassium fluoride in the presence of a phase transfer catalyst, the improvement wherein the educt is selected from the group consisting of 3,4-dichloro-nitrobenzene, 2,4-dichloro-nitrobenzene 2,4-dichloro- 5-fluoro-benzoyl chloride, 3,4-dichloro-benzoyl chloride, 2,6-dichloro-benzonitrile, 2-nitro-6-chlorobenzonitrile, 2-trifluoromethyl-4-nitrochlorobenzene, pentachlorobenzotrifluoride, 4-trifluoromethyl-tetrachlorobenzoyl chloride and 3,4,5-trichlorobenzotrifluoride, the phase transfer catalyst is a quaternary nitrogen compound, a quaternary phosphorus compound, a pyridinium salt or a crown ether, and the reaction is effected in the additional presence of a salt of a metal of main groups 3 to 5 of the periodic table of the elements and of sub-group elements, the reaction is effected at from about 100° to 250° C., about 0.1 to 10 moles of the metal salt being present per mole of phase transfer catalyst, and about 0.1 to 20 mole % of the phase transfer catalyst being present based on the educt.