1-Bromo-2,3,5,6-tetrafluorobenzene is used to produce 1,2,4,5-tetrafluoro-3-hept-1-ynyl-benzene. It is also used as a pharmaceutical intermediate.
Potassium salt of 2,3,5,6-tetrafluorobenzoic acid (100 g) was added to dimethylformamide (250 ml) and stirred in a glass reactor equipped with a mechanical stirrer, a dropping funnel, a separator, a Liebig condenser, an adapter and a receiving flask, the reaction mixture was heated to 140 C and bromotrichloromethane (85 g) was added in such a way as to maintain a 140-143 C temperature while distilling out the resulting product. This process was continued until the end of the outgassing. The distillate was mixed with the cube and washed with two volumes of 15% perchloric acid. The lower (organic) layer was separated, hydrodistilled, then dried and distilled with CaCl2. 1-Bromo-2,3,5,6-tetrafluorobenzene (89 g) was obtained with a boiling point of 144C and a yield of 91%.
