PRODUCTION OF TRIFLUOROMERCAPTOPHTHALIC ACID

PURPOSE:To obtain the titled compound useful as a raw material for pharmaceuticals, with simple process in high yield, by reacting tetrafluorophthalic acid with hydrosulfide of alkali metal, alkaline earth metal or ammonium in a polar aprotic solvent. CONSTITUTION:A trifluoromercaptophthalic acid (e.g. 3,5,6-trifluoro-4- mercaptophthalic acid) is produced by reacting tetrafluorophthalic acid with one or more kinds of hydrosulfides of alkali metal, alkaline earth metal or ammonium (e.g. lithium, sodium or potassium hydrosulfide, etc.) in a polar aprotic solvent (e.g. DMSO, DMF, diethylformamide, DMA, etc.). The amount of the hydrosulfide is preferably about 1-5.0pts. per 1pt. of tetrafluorophthalic acid and the concentrations of the above reactants in the polar aprotic solvent are preferably about 1-30wt% each.