A re-investigation of the reaction of hemimellitic acid with sulphur tetrafluoride. A simple preparation of 2,6-bis(trifluoromethyl)benzoic acid

Abstract

The reaction of hemimellitic acid (1) with SF 4/HF gives a 1 : 3.5 : 13 mixture of 1,2,3-tris (trifluoromethyl) benzene (2), 1,1,3,3-tetrafluoro 4-trifluoromethyl-l, 3-dihydroisobenzofuran (3) and 2,6-bis(trifluoromethyl)benzoyl fluoride (4). Treatment of the crude reaction mixture with aqueous KOH, followed by acidification of the water phase, gives a good yield of pure 2,6-bis(trifluoromethyl)benzoic acid (5).