This embodiment relates to the synthesis of 2-chloro-6-nitrobenzaldehyde: To a stirred solution of 2-chloro-6-nitrotoluene (18.53 g, 108.0 mmol) in anhydrous N,N-dimethylformamide (240 mL) was added N,N-dimethylformamide dimethyl acetal (39.5 g, 44.0 mL, 331.0 mmol). After the mixture was heated at 140 °C for 16 h, the dark red solution was cooled to 0 °C and slowly added to a rapidly stirred solution of sodium periodate (83.0 g, 388.0 mmol) in water (291 mL) through a cannula over a 1 h period. The reaction flask was washed with N,N-dimethylformamide (77 mL) at 0 °C and the washings were added to the sodium periodate mixture. The reaction mixture was stirred at 0°C for 2 hours and then slowly warmed to room temperature. After continued stirring for 6 hours, the orange solution was filtered and rinsed with toluene/ethyl acetate (1:1, 200 mL). The filtrate was washed sequentially with water (3 x 150 mL) and saturated aqueous sodium chloride solution (3 x 150 mL). The organic phase was dried with magnesium sulfate and concentrated under reduced pressure to give a dark red oil, which precipitated as a solid upon addition of hexane (40 mL). The solid was recrystallized by toluene to afford the target product 2-chloro-6-nitrobenzaldehyde (17.23 g, 92.88 mmol, 86% yield).1H NMR (400 MHz, CDCl3) δ 10.42 (s, 1H), 8.01 (dd, J=1.0, 8.2 Hz, 1H), 7.79 (dd, J=1.0, 8.1 Hz, 1H ), 7.65 (t, J=8.1Hz, 1H); 13C NMR (100MHz, CDCl3) δ 188.6, 148.4, 138.6, 132.9, 132.4, 123.4, 121.9.
