This embodiment relates to the synthesis of methyl 2-nitro-5-chlorobenzoate: to a stirred solution of 5-chloro-2-nitrobenzoic acid (9.393 g, 46.60 mmol) in anhydrous DMF (155 mL) at 0 °C was added potassium carbonate (K2CO3, 13.23 g, 95.72 mmol) and iodomethane (MeI, 19.38 g, 8.5 mL. 136.5 mmol), followed by slow warming of the reaction mixture to 40 °C. After 1 h of reaction, the solution was cooled to room temperature and diluted with ethyl acetate (EtOAc, 115 mL). The organic phase was washed sequentially with water (3 x 100 mL) and saturated sodium chloride solution (3 x 100 mL). The combined organic phases were dried over anhydrous sodium sulfate (Na2SO4) and concentrated under reduced pressure, and the resulting crude product was purified by silica gel column chromatography with 40-60% ethyl acetate/hexane as eluent to afford methyl 2-nitro-5-chlorobenzoate (9.244 g, 42.87 mmol, 92% yield) as a light yellow solid. The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3) and 13C NMR (100 MHz, CDCl3).
