4-Chloro-8-nitroquinoline (6a) was synthesized as follows: 4-chloroquinoline (10.0 g, 61.3 mmol) was slowly added to sulfuric acid (45 mL), and the temperature needed to be controlled not to exceed 15 °C during the reaction. Subsequently, the reaction solution was cooled to -15 °C and fuming nitric acid was added dropwise at this temperature. After addition, the reaction mixture was gradually warmed to room temperature and stirring was continued for 3 hours. Upon completion of the reaction, the mixture was poured onto ice, the pH was adjusted to 9 with NH4OH, the precipitated solid precipitate was collected by filtration, washed thoroughly with water, dried and recrystallized from methanol to afford the target product 4-chloro-8-nitroquinoline (6a) 7.5 g in 59% yield. The product characterization data were as follows: melting point 128-129 °C (literature value 129-130 °C); 1H NMR (CDCl3) δ 7.67 (d, 1H, J=4.5 Hz), 7.75 (dd, 1H, J=8.6 Hz, J=7.6 Hz), 8.10 (dd, 1H, J=7.6 Hz, J=1.3 Hz), 8.48 (dd. 1H, J=8.6Hz, J=1.3Hz), 8.94 (d, 1H, J=4.5Hz); 13C NMR (CDCl3) δ 123.0, 124.4, 126.5, 127.5, 128.3, 140.6, 143.2, 148.7, 152.1.
