Sodium perborate tetrahydrate (18.5 g, 0.12 mol, 5.0 eq) was suspended in glacial acetic acid (125 mL) and heated to 65 °C. 4-Bromo-2,6-difluoroanilline(5.0 g, 24.0 mmol, 1.0 eq) dissolved in glacial acetic acid (50 mL) was added slowly through a funnel over 4 h. After the addition, the reaction mixture was heated for 3 h additional hours before a second portion of NaBO3·4H2O (6.0 g, 30.0 mmol) was added. Then, the mixture was stirred for 14 h, and a third portion of oxidating agent (9.0 g, 45.0 mmol) was added. 9 h after the third addition full consumption of the starting material was indicated by TLC. After cooling the mixture to room temperature, the formed solid was removed by filtration. The filtrate was poured into ice-cold water (300 mL). The precipitated solid was filtered off and dried to give the product 5-Bromo-1,3-difluoro-2-nitrobenzene as a yellow solid (3.40 g 60percent).
