Synthesis
Under argon protection, 3-(2-bromo-4-fluorophenyl)propionic acid (1.2 g) was added to trifluoromethanesulfonic acid (15 mL) in batches and the reaction was carried out at room temperature. Subsequently, the reaction mixture was stirred at 60°C for 2 hours, then warmed to 80°C and continued stirring for 16 hours. After completion of the reaction, it was cooled to room temperature and the mixture was slowly poured into ice water. The aqueous phase was extracted twice with ethyl acetate. The organic phase was combined and washed sequentially with saturated aqueous Na2CO3 and brine. The organic phase was dried over anhydrous MgSO4 and concentrated under reduced pressure to remove the solvent. The resulting residue was stirred with dichloromethane (40 mL), filtered and washed with dichloromethane. The dichloromethane phase was combined and concentrated to give the target compound 4-bromo-6-fluoro-2,3-dihydro-1H-inden-1-one. Yield: 970 mg; liquid chromatography (Method 3): tR = 0.60 min; mass spectrometry (ESI+): m/z = 229 [M + H]+.
References
[1] Journal of Medicinal Chemistry, 2003, vol. 46, # 3, p. 409 - 416
[2] Patent: WO2013/144098, 2013, A1. Location in patent: Page/Page column 114; 115
[3] Patent: WO2015/36759, 2015, A1
