Synthesis
General procedure for the synthesis of 2-bromo-4-fluoro-5-chloroaniline from 3-chloro-4-fluoroaniline: to a solution of 3-chloro-4-fluoroaniline (5 g, 34.3 mmol) in dichloromethane (60 mL) under ice-bath cooling conditions was added pyridine (4.2 ml, 51.5 mmol), and bromine (1.8 ml, 34.3 mmol) was added slowly and dropwise to a dichloromethane ( 40mL) solution. The reaction mixture was stirred continuously for 1 hour under an ice bath. Upon completion of the reaction, the reaction was quenched by adding aqueous sodium thiosulfate to the mixture and extracted with ethyl acetate. The organic layers were combined, dried with anhydrous sodium sulfate and concentrated under reduced pressure to remove the solvent. The residue was purified by silica gel column chromatography (eluent: ethyl acetate/hexane) to afford the target product 2-bromo-4-fluoro-5-chloroaniline (6.4 g, yield: 83%) as an orange solid. m/z = 223 [M + H]+ by LC-MS.
References
[1] Patent: EP3112369, 2017, A1. Location in patent: Paragraph 0296; 0297
[2] Patent: EP2952510, 2015, A1. Location in patent: Paragraph 0196
[3] Tetrahedron Letters, 2002, vol. 43, # 42, p. 7581 - 7583
[4] European Journal of Medicinal Chemistry, 2012, vol. 50, p. 179 - 195
