367-22-6

372-19-0

367-22-6

1. A CHCl3 (20.0 mL) solution of N-chlorosuccinimide (NCS) was added slowly and dropwise to a stirred CHCl3 (30.0 mL) solution of 3-fluoroaniline (1.11 g, 10.0 mmol) at 0 °C. 2. The reaction mixture was stirred continuously at 0 °C for 42 hours. 3. Upon completion of the reaction, the reaction mixture was concentrated under reduced pressure and the residue was dissolved in Et2O. 4. The mixture was washed with water and subsequently dried with MgSO4. 5. After concentration under reduced pressure, the mixture was purified by rapid chromatography on silica gel, using EtOAc/hexane as eluent, to afford 4-chloro-3-fluoroaniline (259.4 g, 18% yield) as a crystalline solid. 6. To a stirred solution of the above 4-chloro-3-fluoroaniline (259.4 mg, 1.78 mmol) in THF (8.9 mL) was added ethyl chloroacetate (237.3 μL, 2.14 mmol) and Et3N (296.6 μL, 2.14 mmol) sequentially at 0 °C. 7. The mixture was stirred at room temperature for 12 hours. 8. After filtration to remove the precipitate, the filtrate was concentrated under reduced pressure. 9. The residue was dissolved in EtOAc, washed sequentially with 1.0 M HCl, saturated NaHCO3 solution and brine, and then dried with MgSO4. 10. After concentration under pressure, 3-fluoro-4-chloroaniline 6a (435.2 mg, 99% yield) was obtained as brown crystals, which could be used without further purification.