To a stirred solution of isoquinoline (24 g, 186 mmol) in acetic acid (50 mL) was slowly added N-bromosuccinimide (NBS, 36.2 g, 204.6 mmol) at room temperature. The reaction mixture was heated to 100 °C and kept at this temperature for the reaction overnight. Upon completion of the reaction, the mixture was cooled to room temperature and subsequently concentrated under reduced pressure to remove the solvent. The resulting crude product was purified by fast column chromatography (eluent: 5% ethyl acetate/hexane) to give 3-bromoisoquinoline (9.2 g, 23.8% yield) as an oil.
