(1) To a 1000 mL four-necked reaction flask equipped with a magnet and a reflux condenser tube was added 84.4 g of 3,4,5- trifluorobromobenzene (0.4 mol), 500 mL of methanol and 67.2 g of
KOH (1.2 mol), the temperature was raised to 60 C after the addition was completed, and the reaction was stirred for 6 h. A gas chromatograph tracked the reaction process until the raw materials were basically reacted. After the reaction, the reaction solution was frozen at -10 for 5h, a large number of crystals were precipitated, and 80.0g of crystals were obtained by filtration and separation, and the content of the crystals in 2,3-difluoro-5-bromoanisole was 99.2% by GC normalization method. Methanol recovery can be used again.
(2) In a 1000 mL four-necked reaction flask equipped with a magnet and a reflux condenser tube, 80.0 g of obtained above was added.
2,3-difluoro-5-bromoanisole (0.36 mol), 600 mL of toluene and 71.8 g of AlCl3
(0.54 mol). The reaction was heated to 80 C under nitrogen protection and stirred for 5 h. Gas chromatography tracked the progress of the reaction until 2,3-difluoro-5-bromoanisole was essentially reacted. At the end of the reaction, the reaction solution was washed with water, the upper layer was separated, toluene was removed by spin distillation, and 5-bromo-2,3-difluorophenol was obtained by distillation under reduced pressure as 67.7 g, .
The content of the product was 99.3% by GC analysis. Recovered toluene can be used again after drying treatment.
The nuclear magnetic spectra and mass spectra of the obtained target product were tested to be consistent with those of the standard, and the total yield of the two-step reaction was 81.0%.
