Using the compound (CAS:2112-31-4) as starting material, 29.0 g of potassium fluoride (KF) was slowly added to the solution prepared in step (3) under continuous stirring conditions. Subsequently, the reaction mixture was heated to 140-160 °C and maintained at this temperature until the content of 2,3,4-trichlorobenzonitrile was reduced to less than 2% as detected by conventional analytical methods (Step 5). After completion of the reaction, the solvent N,N-dimethylformamide (DMF) was removed by rotary evaporator under reduced pressure to give a brownish-yellow granular solid. The solid was dissolved in 200 mL of toluene and purified by recrystallization. The solution was cooled to about 0 °C and allowed to stand overnight, after which the crystals were collected by filtration and dried to give 33.8 g of 3-chloro-2,4-difluorobenzonitrile. The product was a light yellow granular solid, analyzed by gas chromatography (GC) with a purity of 98.637% and a molar yield of 65.0%.
