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Step 1. 4-Amino-3-nitrobenzoic acid (5.0 g, 27.4 mmol) was dissolved in anhydrous ethanol (100 mL) and an ether solution of 2N HCl (30 mL) was slowly added. The reaction mixture was heated to reflux and kept for 16 hours. After completion of the reaction, the solvent was removed by rotary evaporator under reduced pressure. The crude product was dissolved in dichloromethane (100 mL) and washed with 0.5N aqueous NaOH solution (50 mL x 3). The organic phase was dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give ethyl 4-amino-3-nitrobenzoate as a yellow solid (4.6 g, 79% yield). Mass spectrum (ISP): m/e = 211.1 ([M + H]+). The crude product obtained was used directly in the next step of the reaction.

[1] Patent: CN105636956, 2016, A. Location in patent: Paragraph 0212; 0213
[2] Patent: US2016/200709, 2016, A1. Location in patent: Paragraph 0186
[3] Patent: US2007/191603, 2007, A1. Location in patent: Page/Page column 27
[4] Indian Journal of Chemistry, Section B: Organic Chemistry Including Medicinal Chemistry, 1988, vol. 27, # 1-12, p. 1106 - 1109
[5] Justus Liebigs Annalen der Chemie, 1909, vol. 371, p. 165