Preparation of 3,5 difluoro-4 formyl-N-methylbenzamide.
To an ice-cold solution of 3,5-difluoro-4-formylbenzoic acid (120 g, 645 mmol) in dichloromethane (1.5 L) and N,N-dimethylformamide (2.0 g, 27 mmol) was added oxalyl chloride (90 g, 709 mmol) drop-wise at a rate that allowed the mixture to not exceed an internal temperature of 10°C. The resulting mixture was stirred at the same temperature for 0.5 hr, warmed to room temperature, and stirred for an additional 1.5 hr. The solution was then cooled to 0°C, and aqueous methylamine (40%, 168 mL, 1.94 mol) was added drop-wise at a rate that allowed the mixture to not exceed an internal temperature of 7°C. Afterward, the mixture was quenched with aqueous HC1 (2M, 335 mL, 670 mmol) and warmed to room temperature. The organic layer was separated, washed with brine (500 mL), dried over MgSC>4, filtered, and concentrated under vacuum. The resulting residual solid was taken in MTBE (500 mL), and the resulting mixture was heated to reflux for 0.5 hr, cooled to room temperature, and stirred for 18 hr. Afterward, the mixture was cooled to 0°C, filtered, rinsed with pentane, and dried under vacuum to form the title compound (103 g, 80%) as a solid.
¾ NMR (300 MHz, CDC13) δ ppm 3.03 (d, J = 4.86 Hz, 3 H), 6.37 (br s, 1 H), 7.36-7.42 (m, 2 H), 10.36 (s, 1 H);
MS m/z 200.06 [M+H]+ (ESI).
