General procedure for the synthesis of 4-bromo-6-fluoroquinoline from 4-hydroxy-6-fluoroquinoline: To a solution of 4-hydroxy-6-fluoroquinoline (20 g, 122.58 mmol) in DMF (130 mL) heated to 60 °C was slowly added phosphorus tribromide (13 mL, 1.15 equiv.). The reaction mixture was heated at 45 °C with stirring for 45 min. After the reaction was completed, it was cooled to room temperature and the reaction solution was diluted with water (200 mL). Subsequently, Na2CO3 was slowly added until the pH of the reaction solution reached 10. The precipitated solid product was collected by filtration. The solid was dissolved in ethyl acetate (200 mL) and the solution was concentrated to dryness. The residue was purified by column chromatography (eluent: ethyl acetate) to afford the target product 4-bromo-6-fluoroquinoline as a pale yellow solid (22 g, 79% yield).1H NMR (CDCl3) δ: 8.70 (d, J = 4.7 Hz, 1H); 8.14 (m, 1H); 7.96 (d, J = 4.7 Hz, 1H); 7.81-7.73 (m 2H).
