Synthesis
Step A Preparation of 1-(2-amino-4-bromophenyl)ethanone (162a): 3-bromoaniline (31.3 g, 181.8 mmol) and acetonitrile (75 g, 1.818 mol) were dissolved in anhydrous toluene (120 mL) under argon protection and cooled in an ice bath. The above solution was added dropwise to a hexane solution (200 mL) of boron trichloride (23.4 g, 200 mmol) over 2.5 hours. After dropwise addition, aluminum chloride (26.6 g, 200 mmol) was added in batches over 30 minutes. The reaction mixture was gradually warmed to room temperature and subsequently heated to reflux for 16 hours. Upon completion of the reaction, 3N HCl solution (100 mL) was slowly added dropwise to the reaction mixture with stirring at 10 °C. After the dropwise addition was completed, heating and refluxing was continued for 3.5 hours. The reaction mixture was cooled to room temperature and left to stratify. The aqueous layer was extracted with chloroform (3 x 250 mL). The organic layers were combined, dried with magnesium sulfate, filtered and the filtrate was concentrated to afford the target product 2'-amino-4'-bromoacetophenone 162a (9.58 g, 25% yield). The product was characterized by 1H NMR (CDCl3, 300 MHz): δ 7.54 (d, 1H, J = 8.8 Hz), 6.83 (d, 1H, J = 1.9 Hz), 6.75 (dd, 1H, J = 8.4, 1.8 Hz), 2.54 (s, 3H) ppm.
References
[1] Patent: US2003/166636, 2003, A1
[2] Patent: US2002/52360, 2002, A1
[3] Patent: US2002/137737, 2002, A1
[4] Patent: US6503902, 2003, B2
[5] Patent: US5061800, 1991, A
