The general procedure for the synthesis of 4-bromophthalonitrile (4-BPN) from 4-bromophthalamide (4-BPA) was as follows: in a 200 mL aubergine flask, 100 mL of dry N,N-dimethylformamide (DMF) was added, and 70 mL of thionyl chloride was added slowly dropwise under the conditions of an ice bath at 0°C, with the acceleration of dropwise acceleration being controlled to keep the temperature of the reaction from exceeding 5°C. After the dropwise acceleration, the mixture was allowed to stand for 2 hr at 0°C. The mixture was allowed to stand at 0°C for 2 hours. Subsequently, 20.9032 g (0.086 mol) of 4-BPA powder was slowly added and the reaction temperature continued to be controlled to not exceed 5°C. After maintaining the reaction temperature in the range of 0 to 5°C for 5 hrs, the ice bath was removed and the reaction system was warmed to 23°C and the reaction continued for 24 hrs. Upon completion of the reaction, the reaction solution (which appeared as a white to yellow suspension) was slowly poured into a 1 L beaker containing 300 g of ice. The precipitated white to yellow crystals were collected by filtration under reduced pressure and washed sequentially with 100 mL of purified water and 100 mL of methanol. The crude product was dissolved in 10 times its weight in methanol and heated using an oil bath until completely dissolved, then left to recrystallize at 23°C. The product was dried under reduced pressure. The resulting white crystals were dried under reduced pressure for 24 h to give 17.80 g (yield: 80%) of 4-BPN. The structure of the product was confirmed by 1H-NMR spectrum (CDCl3, ppm): 7.96 (dd, 1H), 7.90 (dd, 1H), 7.67 (d, 1H).
