The general procedure for the synthesis of ethyl 2-carboxy-3-nitrobenzoate from 3-nitrophthalic acid is as follows: 3-nitrophthalic acid (35 g) was dissolved in ethanol (300 ml) containing concentrated hydrochloric acid. Sulfuric acid (20 ml) was slowly added to this solution and the reaction was then heated under reflux conditions for 24 hours. After completion of the reaction, the solvent was removed by distillation. The residue was poured into ice water (700 ml) and extracted with ethyl acetate. The organic layer was washed with water and back-extracted with aqueous potassium carbonate. The aqueous layer was acidified to acidity with hydrochloric acid and extracted with dichloromethane. The organic layer was washed with water and dried. Finally, the solvent was removed by distillation to afford the solid product ethyl 2-carboxy-3-nitrobenzoate (29 g, 74% yield), which could be used in subsequent reactions without further purification. The structure of the product was confirmed by 1H-NMR (90 MHz, CDCl3) and IR (Nujol): 1H-NMR δ: 1.43 (3H, t), 4.47 (2H, q), 7.70 (1H, t), 8.40 (2H, d), 9.87 (1H, br s); IR (Nujol) cm-1: 1725,1535, 1350,1300,1270.
