[Cl:1]C1C(F)=C(C=C(Cl)C=1F)C(F)=O.ClC1C(F)=C(F)C(F)=C(C=1)C(F)=O.ClC1C(Cl)=C(Cl)C(Cl)=C(C=1)C(Cl)=O.[F-].[K+].FC1C=C(F)C(F)=CC=1C(O)=O.[Cl:54][C:55]1[C:56]([F:66])=[C:57]([CH:61]=[C:62]([F:65])[C:63]=1[F:64])[C:58](O)=[O:59].S(Cl)(Cl)=O>S1(CCCC1)(=O)=O>[Cl:54][C:55]1[C:56]([F:66])=[C:57]([CH:61]=[C:62]([F:65])[C:63]=1[F:64])[C:58]([Cl:1])=[O:59]The benzoyl halides (1) used as starting materials for this synthetic route are prepared as follows: 3,5-dichloro-2,4-difluorobenzoyl fluoride (boiling point 97°/20 mbar; nD20 =1.5148) and 5-chloro-2,3,4-trifluorobenzoyl fluoride (boiling point (68°-70°/20 mbar; nD20 =1.4764) are obtained together by heating tetrachlorobenzoyl chloride with potassium fluoride in sulpholane at elevated temperatures: ##STR18## The chlorination of 2,4,5-trifluorobenzoic acid in chlorosulphonic acid leads to 3-chloro-2,4,5-trifluorobenzoic acid which is reacted as the crude product with thionyl chloride to give 3-chloro-2,4,5-trifluorobenzoyl chloride (boiling point 94°/18 mbar; nD20 =1.5164): ##STR19##
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