Occidental Chemical Corporation

Deanne M Nowak

Henry C Lin

William S Derwin

Neil J O'Reilly

3,4,6-trifluorophthalic acid is prepared in high yield by reaction of a 3,4,6-trichloro-N-substituted phthalimide with potassium fluoride at temperatures in the range of 200.degree. to 270.degree. C. in the absence of a catalyst to form the corresponding trifluoro-N-substituted phthalimide which, in turn, is hydrolyzed to form the 3,4,6-trifluorophthalic acid.

Preparation of 3,4,6-trifluorophthalic acid

Chlorinated phthalic anhydrides are converted to fluorinated phthalic acids without dilactone formation by reacting an anhydride with a primary amine under anhydrous conditions to form the corresponding chlorinated-N-substituted phthalimide which in turn is reacted with a fluorinating agent under anhydrous conditions to form the corresponding fluorinated phthalimide which is hydrolyzed to form the corresponding fluorinated phthalic acid. In a preferred embodiment tetrachlorophthalic anhydride is refluxed with aniline in the presence of glacial acetic acid for 5 to 10 hours to form tetrachloro-N-phenylphthalimide which is reacted with KF in sulfolane in the presence of tributylhexadecylophosphonium bromide under nitrogen at 140.degree. C. to 160.degree. C. for 10 to 15 hours to form tetrafluoro-N-phenylphthalimide which in turn is hydrolyzed by refluxing with 50% H.sub.2 SO.sub.4 for 15 to 25 hours. The tetrafluoro-N-phenylphthalimide is a novel compound. The fluorinated phthalic acid products are intermediates for the corresponding fluorinated phthalic anhydrides, fluorinated benzoic acids and fluorinated benzenes.

Tetrafluoro-N-phenylphthalimide

2,4,5-trifluorobenzoic acid is prepared by converting 4,5-di-fluoroanthranilic acid to the corresponding amine salt, converting the amine salt to the corresponding diazonium tetrafluoroborate and decomposing the tetrafluoroborate in a Schiemann reaction. In a preferred preparation, the 10 percent HCl is added to solid 4,5-difluoroanthranilic acid in sufficient amount to dissolve the solid at 70.degree. C., the amine salt is isolated, aqueous NaNO.sub.2 is added to the isolated amine salt at 0.degree. C., followed by addition of 40 to 50 percent aqueous HBF.sub.4 at 0.degree. C., followed by separation of the tetrafluoroborate by cooling and filtering and then drying, and the dried separated tetrafluoroborate is thermally degraded to 2,4,5-trifluorobenzoic acid by heating at 125.degree. to 140.degree. C.

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Depew, NY, United States of America

Deanne M Nowak