To a 2 L reactor at room temperature, 2,6-dichlorobenzonitrile (290.0 g, 1.68 mol) was added followed by addition of 96% sulfuric acid (10 eq, 0.92 L, 16.8 mol) with stirring at 25°C. After addition of sulfuric acid, the reaction mixture was stirred for 15 minutes to obtain a clear yellowish solution. The mixture was cooled to 0°C and N-bromosuccinimide (321 g, 1.07 eq, 1.8 mol) was added in portions over the course of 10 minutes at 0°C and a slightly exotherm was observed. The reaction mixture was stirred at 25 °C for 18h to afford a thick, pale yellowish orange slurry. After completion of the reaction, the crude mixture was slowly discharged to a work-up vessel containing chilled water (2.9 L, 10V, 0-5 °C). The slurry was stirred 45 minutes then the resulting precipitates collected by filtration. The filter cake was washed with water (500 mL (1.7V) ×5), dried under house vacuum and then washed with ethyl acetate (300 mL (1V) × 3). The solid was dried under vacuum to obtain 3-Bromo-2,6-dichloro-benzonitrile (355 g, yield: 80%).
