Step 2: Synthesis of 6-chloro-3-nitroquinolin-4-ol
To a 500 mL round bottom flask was added 5-chloro-2-(2-nitroethylideneamino)benzoic acid (25 g, 0.10 mol), K2CO3 (42.6 g, 0.30 mol) and acetic anhydride (250 mL). The reaction mixture was heated to 90 °C and the reaction was stirred at this temperature for 1 hour. Upon completion of the reaction, the resulting solid product was collected by filtration, washed sufficiently with deionized water to remove residual reactants and salts, and subsequently dried to afford 17.5 g (76% yield) of 6-chloro-3-nitroquinolin-4-ol as a gray solid. The structure of the product was confirmed by 1H NMR (300 MHz, DMSO-d6): δ 9.12 (s, 1H), 8.15 (s, 1H), 7.72 (s, 2H). Mass spectral analysis showed m/z: 224 (M+H+).