General procedure for the synthesis of 3-bromocinnolin-4(1H)-ones from 1H-cinnolin-4-one: Intermediate 2: Preparation of 3-bromo-1,4-dihydro-4-cinnolinone: A solution of bromine (0.8 mL) in acetic acid (10 mL) was slowly added dropwise to a suspension of 1H-cinnolin-4-one (1.5 g, 10.27 mmol) in acetic acid (15 mL), followed by addition of sodium acetate (1.51 g, 18.49 mmol). The reaction mixture was heated to 100 °C and stirred at this temperature for 1 hour. Upon completion of the reaction, the mixture was concentrated under reduced pressure to half the initial volume and poured into ice water. The precipitated solid was collected by filtration, washed with water and dried under reduced pressure. Yield: 64%. 1H-NMR (δ ppm, CDCl3, 300 MHz): 13.87 (broad single peak, 1H); 8.06 (double peak, J = 7.8 Hz, 1H); 7.84-7.80 (multiple peaks, 1H); 7.61 (double peaks, J = 8.7 Hz, 1H); 7.49 (triple peak, J = 7.8 Hz, 1H).
