General procedure for the synthesis of 1,5-dibromo-2,4-difluorobenzene from 2,4-difluorobromobenzene: Iron powder (3.15 g, 56 mmol) was added to a solution of 1-bromo-2,4-difluorobenzene (19.3 mL, 171 mmol) in dichloromethane (100 mL). A dichloromethane (25 mL) solution of bromine (11 mL, 214 mmol) was slowly added dropwise to the stirred suspension over 30 minutes. The reaction mixture was stirred overnight at room temperature. Subsequently, the reaction mixture was slowly poured into saturated aqueous sodium thiosulfate solution (200 mL) and stirring was continued for 30 minutes at room temperature. The reaction mixture was extracted with dichloromethane (3 x 80 mL). The organic phases were combined, washed with brine, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to give 1,5-dibromo-2,4-difluorobenzene (40 g, 86% yield) as a brown oil.1H NMR (500 MHz, chloroform-d) δ 7.79 (t, J = 7.0 Hz, 1H), 7.00 (t, J = 8.2 Hz, 1H).
