[Synthesis]
Step 2: In a dry reaction flask, 6-fluoro-2-naphthalenecarbonyl chloride (472 mg, 2.097 mmol) with AIBN (173 mg, 1.052 mmol) was dissolved in CBrCl3 (10 mL). The above solution was slowly added dropwise to a mixture containing 2-mercaptopyridine N-oxide sodium salt (981 mg, 6.58 mmol) and CBrCl3 (10 mL) under nitrogen protection at 100 °C over 30 min. After the dropwise addition, the reaction mixture was continued to be stirred at 100 °C for 15 min and subsequently cooled to room temperature. The reaction solution was quenched with deionized water (H2O) and extracted with ethyl acetate (EtOAc, 2 × 10 mL). The organic phases were combined, dried with anhydrous magnesium sulfate (MgSO4), filtered and concentrated under reduced pressure. The crude product was purified by a Biotage fast chromatography system (elution gradient: 0-5% EtOAc/heptane; column: SNAP25) to afford the target compound 2-bromo-6-fluoronaphthalene (6b, 472 mg, 40% yield) as a white solid.1H NMR (400 MHz, MeOD) δ ppm: 7.34 (td, J = 8.84, 2.59 Hz, 1H), 7.49-7.57 (m, 1H), 7.60 (ddd, J = 8.78, 1.96, 0.69 Hz, 1H), 7.77 (d, J = 8.84 Hz, 1H), 7.87 (dd, J = 9.09, 5.56 Hz, 1H), 8.09 (d, J = 1.58 Hz, 1H). |