Step 1: Potassium cyanide (KCN, 1.25 g, 19.2 mmol) was added to a solution of 3-fluoro-4-chlorobenzyl bromide (4-(bromomethyl)-1-chloro-2-fluorobenzene, 3.90 g, 17.5 mmol) in dimethyl sulfoxide (DMSO, 60 mL). A small amount of water (H2O, a few mL) was added to promote the dissolution of potassium cyanide. After 1 h of reaction, the reaction mixture was diluted with water and extracted with ethyl acetate (EtOAc). The organic phases were combined, dried over anhydrous sodium sulfate (Na2SO4), filtered and concentrated. The crude product was purified by silica gel fast column chromatography (Biotage 40M, eluent ratio 9:1 petroleum ether/ethyl acetate) to give 3-fluoro-4-chlorophenylacetonitrile (2-(4-chloro-3-fluorophenyl)acetonitrile, 1.81 g, yield 61.2%) as a yellow crystalline solid.
