General procedure for the synthesis of 2-bromo-1-iodo-4-methoxybenzene using 3-bromoanisole as starting material: 3-bromoanisole (10 g, 53.5 mmol), mercuric oxide (HgO, 8.8 g, 40.6 mmol) and acetic anhydride (Ac2O, 1 mL) were dissolved in dichloromethane (CH2Cl2, 100 mL) under stirring conditions, and refluxed for 30 minutes. Subsequently, iodine (I2, 17.6 g, 69.5 mmol) was added in six 12-hour intervals, and refluxing was continued for 12 hours after each addition. Upon completion of the reaction, the reaction mixture was filtered through a diatomaceous earth pad and the filtrate was washed with saturated sodium thiosulfate (Na2S2O3) solution. The aqueous layer was extracted with dichloromethane (3 x 10 mL), the organic layers were combined and dried over anhydrous magnesium sulfate (MgSO4) and subsequently concentrated to dryness under reduced pressure. The crude product was purified by fast column chromatography (with cyclohexane as eluent) to afford the target compound 2-bromo-1-iodo-4-methoxybenzene as a colorless oil (94% yield). The product was characterized by 1H NMR (300 MHz, CDCl3): δ 7.68 (d, J = 8.8 Hz, 1H), 7.19 (d, J = 2.8 Hz, 1H), 6.59 (dd, J = 2.8 Hz, J = 8.8 Hz, 1H), 3.77 (s, 3H).
