The general procedure for the synthesis of 3-chloro-5-fluorobenzonitrile from 1-bromo-3-chloro-5-fluorobenzene and zinc cyanide was as follows: 1-bromo-3-chloro-5-fluorobenzene (80 g, 480 mmol), zinc cyanide (33.65 g, 290 mmol), and zinc powder (0.94 g, 14.46 mmol) in a N,N-dimethylformamide (DMF, 340 mL) The mixture was stirred at room temperature for 5 min. Subsequently, dichloro[1,1 '-bis(diphenylphosphino)ferrocene]palladium(II) (4.99 g, 16 mmol) was added and the mixture was heated to reflux for 50 minutes. After completion of the reaction, the mixture was cooled to room temperature, filtered through Arbocel and washed with ether/pentane (50:50, 7 x 100 mL). After separation of the phases, the organic phase was diluted with water (100 mL) and extracted with additional ether/pentane (50:50, 3 x 100 mL). The organic solutions were combined, washed with water, dried over magnesium sulfate and subsequently concentrated under vacuum. The residue was purified by distillation under reduced pressure to afford 3-chloro-5-fluorobenzonitrile as a colorless solid in 66% yield (48.5 g). Mass spectrometry (LRMS) analysis showed: m/z APCI 155 [MH+].
