Tetrafluorophthalic acid

Hydrolysis of tetrafluorophthaloyl difluoride with water gives tetrafluorophthalic acid (5).10,11... 

Aliphatic trifluoromethyl groups generally resist hydrolysis, both in acidic or alkaline media, unless adjacent to a C = C bond. Hydrolysis of a trifluoromethyl group attached to an aromatic nucleus requires rather energetic conditions. Thus, perfluoro(l,2-dimethylbenzene) is hydrolyzed by oleum to give tetrafluorophthalic acid (l).162... 

Retention of ester groups. Equimolar amounts of startg. nitrile and tetrafluorophthalic acid heated at 135° for 4 days in a heavy-walled glass pressure tube product. Y 56%. Work-up is simple since no solvent is required. F.e.s. W.D. Rounds, G.W. Gribble, Tetrahedron Letters 29, 6557-60 (1988) from carboxylic acid amides with tetrachloro-or tetrafluoro-phthalic anhydride s. ibid. 6553-6. 

R CONHR2 —> R COOH. This conversion can be effected in 70-90% yield by tetrachloro- or tetrafluorophthalic anhydride in the absence of water or of a solvent in a melt at 135-170°. This reaction does not affect esters. Conversion of nitriles to carboxylic acids can be effected by a similar reaction with tetrafluoro-or tetrachlorophthalic acid at 135-180° for 4-6 days in 60-85% yield. 

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