N-Bromosuccinimide (NBS) (1.48 g, 8.32 mmol) was added to a solution of 2-Nitrobenzaldehyde (1.01 g, 6.71 mmol) in H2SO4 (concentrated 5.0 mL). The resulting mixture was stirred at ambient temperature (3 h). The reaction was quenched with ice and extracted with ethyl acetate (320mL). The combined organic phases were washed with saturated NaCl (aqueous, 30 mL), dried (MgSO4), and filtered through a silica gel plug, and the solvents were evaporated under reduced pressure. The resulting brown oil was purified by column chromatography (hexanes=EtOAc, 8:2) to afford 2-Bromo-6-nitrobenzaldehyde.
