1. A solution of tetrahydrofuran (THF, 100 mL) of 4-bromo-2-nitroaniline (6.50 g, 30.0 mmol) was slowly added dropwise to the boron trifluoride ethyl ether complex (BF3-OEt2, 16.0 mL, 126.3 mmol) at -30 °C for 20 min.
2. the reaction mixture was continued to be stirred at -30 °C for 10 min.
3. A solution of tert-butyl nitrite (tBuONO, 13.0 mL, 90%, 109.3 mmol) in THF (81 mL) was added dropwise to the above mixture over 15 minutes.
4. the reaction mixture was slowly warmed to -10 °C, followed by dropwise addition of ether (Et2O, 158 mL).
5. The reaction mixture was stirred at -5 °C for 1 h until a white solid precipitate was observed.
6. The solid was collected by filtration and washed with ether to give a white solid.
7. The resulting white solid was added one time to a 500 mL round bottom flask containing potassium iodide (KI, 5.45 g, 26.53 mmol), iodine (I2, 7.16 g, 13.27 mmol) and acetonitrile (MeCN, 120 mL).
8. The mixture was stirred at room temperature for 1.3 hours, followed by quenching the reaction with saturated aqueous sodium bicarbonate (NaHCO3).
9. The reaction mixture was washed with aqueous sodium thiosulfate (Na2S2O3, 250 mL) and extracted with dichloromethane (CH2Cl2, 2 x 150 mL).
10. The organic layers were combined, dried over anhydrous sodium sulfate (Na2SO4) and concentrated in vacuum to afford the target product 4-bromo-1-iodo-2-nitrobenzene (8.61 g, 88% yield) as a yellow solid.
