Ethylmagnesium bromide (EtMgBr, 370 mL, 1110 mmol) was added slowly and dropwise to a stirred solution of 2-bromo-5-chlorobenzonitrile (80 g, 370 mmol) in tetrahydrofuran (THF, 1000 mL) at 0 °C. The reaction mixture was kept at 0-5 °C for 5 h, followed by dropwise addition of methanol (MeOH, 500 mL). The solution continued to be stirred for 15 minutes before sodium borohydride (NaBH4, 28 g, 740 mmol) was carefully added and the resulting mixture was stirred for 16 hours at room temperature. Upon completion of the reaction, the reaction solution was poured into water and extracted with ethyl acetate (EtOAc, 3 x 200 mL). The organic layers were combined and dried with anhydrous sodium sulfate (Na2SO4). After filtration, the filtrate was concentrated under reduced pressure to give the crude product. The crude product was purified by column chromatography (eluent: petroleum ether/ethyl acetate=3:1) to afford 6-chloro-3,4-dihydro-isoquinolin-1-one (30 g, yield 34.6%) as a yellow oil. Mass spectrum (MS): 235.5 [M+H]+.
