Triethylamine → 4-Bromo-3-fluoro-N-methoxy-N-methylbenzamide

Participants

Reaction Steps

To a suspension of 4-bromo-3-fluorobenzoic acid (1, 967.9 g, 4.4 mol) in dichloromethane (5.9 L) and DMF (21 mL) was slowly added a solution of oxalyl chloride ((COCl)2, 560 mL, 6.4 mol, 1.45 equiv) in dichloromethane (520 mL) at room temperature. The resulting reaction mixture was stirred at room temperature for 20 h and then cooled to 0° C. by ice-water bath. N,O-dimethyl hydroxylamine hydrochloride (826 g, 8.4 mol, 1.9 equiv) was added followed by slow addition of triethylamine (TEA, 2.5 L, 17.7 mol, 4.0 equiv) at 0° C. The reaction mixture was then gradually warmed to room temperature and stirred at room temperature overnight. Once the coupling reaction was complete, the reaction mixture was washed with saturated aqueous sodium bicarbonate solution (NaHCO3, 2 L). The aqueous phase was back extracted with dichloromethane (1 L). The combined organic phases were washed with water (1 L), brine (1 L), and concentrated under reduced pressure. The resulting solid residue was dissolved into methyl tert-butyl ether (MTBE, 5 L), washed sequentially with water (5×1 L), brine (1 L), and dried over anhydrous sodium sulfate (Na2SO4). The filtrated solution was concentrated under reduced pressure and the resulting solid was dried in a vacuum oven at 45° C. to afford 4-bromo-3-fluoro-N-methoxy-N-methylbenzamide (3, 1106 g, 1153 g theoretical, 95.9% yield) which was used for the subsequent reaction without further purification. For 3: 1H NMR (400 MHz, DMSO-d6) δ ppm 7.78 (t, 1H, J=7.47 Hz), 7.56 (dd, 1H, J=9.3, 1.6 Hz), 7.18 (d, 1H, J=8.1 Hz), 3.53 (s, 3H), 3.25(s, 3H); C9H9BrFNO2 (MW 262.08), LCMS (EI) m/e 262.0/264.0 (M++H).

Provenance & Evidence