Synthesis
Step 1: 3-amino-5-nitrobenzoic acid was dissolved in concentrated hydrochloric acid to prepare a 0.09 M solution. To this solution, 7.0 equivalents of aqueous NaNO2 (0.96 M) was slowly added at 0°C. After gradually warming the reaction mixture to room temperature over 30 minutes, 10.0 equivalents of aqueous CuCl solution (1.37 M) was added. The reaction mixture was stirred at room temperature for 3 hours and subsequently heated to 70 °C and kept for 30 minutes. After completion of the reaction, ether and water were added to separate the organic phase and the aqueous phase was extracted with ether. The organic layers were combined, dried and the solvent was evaporated to give a solid product (MS (ES+) m/z 200,202 (M+H)+). The solid was dissolved in methanol to prepare a 0.1 M solution. To this solution 20 equivalents of SOCl2 was added and the reaction mixture was heated at 80 °C for 16 hours. At the end of the reaction, the solvent was evaporated and the residue was dissolved in ethyl acetate and saturated aqueous NaHCO3 solution. The aqueous phase was separated and the organic phase was washed sequentially with saturated aqueous NaHCO3 and brine, dried and the solvent was evaporated to give the title compound methyl 3-chloro-5-nitrobenzoate in 95% yield as a white solid (MS (ES+) m/z 216,218 (M+H)+).
