General procedure for the synthesis of 2,2-difluoro-5-bromo-1,3-benzodioxole from 2,2-difluoro-1,3-benzodioxole: In a 1000 mL round-bottomed flask fitted with a mechanical stirrer, a reflux condenser, and a pressure-equilibrium charging funnel, 2,2-difluoro-1,3-benzodioxole (200 g, 1.27 mol) and water (456 g, 25.3 mol). Bromine (284 g, 1.77 mol) was added dropwise at 25 °C for 1 hour. The temperature of the reaction mixture was increased from 25 °C to 85 °C during the dropwise addition. The reaction mixture was kept at 85 °C for 8 h. The reaction process was monitored by liquid chromatography. After completion of the reaction, the reaction mixture was cooled to 25°C. The organic and aqueous layers were separated, and the organic layer was washed sequentially with sodium bisulfite solution and sodium bicarbonate solution to obtain the crude product of 2,2-difluoro-5-bromo-1,3-benzodioxole. The crude product was purified by vacuum distillation. Yield: 80%; purity: 99.8% (determined by liquid chromatography).
