Procedure for the synthesis of methyl 4-chloro-3-nitrobenzoate (1): 4-chloro-3-nitrobenzoic acid (5.0 g, 24.8 mmol) was dissolved in 200 mL of methanol and 4.15 mL (29.8 mmol) of triethylamine was added. The reaction mixture was cooled in an ice-salt bath and 3.19 mL (44.7 mmol) of acetyl chloride was added slowly and dropwise. The reaction mixture was stirred under reflux conditions for 6 hours. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure. The residue was dissolved in 100 mL of water and then extracted twice with ethyl acetate (100 mL). The organic phases were combined, dried with anhydrous magnesium sulfate and concentrated under reduced pressure. The crude product was recrystallized with ether (10 mL) to give white crystals of methyl 4-chloro-3-nitrobenzoate (4.81 g, 92% yield). Thin Layer Chromatography (TLC) Rf = 0.55 (unfolding agent: ethyl acetate/cyclohexane = 7/3); melting point 79-80 °C. Infrared spectroscopy (IR) showed the carbonyl absorption peak located at 1716 cm-1; 1H NMR spectrum (300 MHz, DMSO-d6) δ 3.90 (single peak, 3H, OCH3), 7.90 (double peak, 1H, H5, J5-6 = 8.1 Hz), 8.15 (double-double peak, 1H, H6, J6-5 = 8.1 Hz, J5-2 = 1.5 Hz ), 8.49 (double peaks, 1H, H2, J2-6 = 1.5Hz). Molecular formula: C8H6ClNO4.
