[CH3:1][O:2][C:3](=[O:16])[C:4]1[CH:9]=[CH:8][C:7]([O:10][CH2:11][CH2:12][Cl:13])=[C:6]([O:14][CH3:15])[CH:5]=1.C(OC(=O)C)(=O)C.[N+:24]([O-])([OH:26])=[O:25]>C(O)(=O)C>[CH3:1][O:2][C:3](=[O:16])[C:4]1[CH:5]=[C:6]([O:14][CH3:15])[C:7]([O:10][CH2:11][CH2:12][Cl:13])=[CH:8][C:9]=1[N+:24]([O-:26])=[O:25]The intermediate 4-(2-chloro-ethoxy)-3-methoxy-benzoic acid methyl ester (2.7 g, 11.03 mmol) was taken in acetic acid (30 mL) and acetic anhydride (6 mL) was added. The solution was cooled to 0° C. and 90% nitric acid (2 mL) was added. The reaction mixture was stirred for 10-15 minutes at ambient temperature, then heated to 50° C. for 2h. Completion of the reaction was monitored by TLC. The reaction mixture was cooled and was poured on to crushed ice. The precipitate formed was filtered and was dried to afford the pure 4-(2-chloro-ethoxy)-5-methoxy-2-nitro-benzoic acid methyl ester (2.73 g, 85%) as a yellow solid. 1H NMR (300 MHz, DMSO-d6) δ 7.70 (s, 1H), 7.35 (s, 1H), 4.42 (t, 2H), 4.10-3.90 (m, 5H), 3.80 (m, 3H).
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