General procedure for the synthesis of 7-fluoro-6-nitro-4-hydroxyquinazoline from 2-amino-4-fluorobenzoic acid: 2-amino-4-fluorobenzoic acid (25 g, 152 mmol) was slowly added dropwise to a mixed solution of concentrated sulfuric acid (50 mL) and concentrated nitric acid (51 mL) at 0 °C. The reaction mixture was stirred at room temperature for 1 hour and then warmed to 110°C and continued stirring for 2 hours. Upon completion of the reaction, the mixture was cooled to room temperature and quenched by slowly adding ice water (300 mL). The resulting mixture was continued to be stirred for 30 min, followed by filtration to give 7-fluoro-6-nitro-4-hydroxyquinazoline solid product (25 g, 79% yield). The structure of the product was confirmed by nuclear magnetic resonance hydrogen spectroscopy (NMR, 300 MHz, CDCl3) and mass spectrometry (MS, ESI+): NMR data: δ 12.83 (broad single peak, 1H), 8.72 (double peak, 1H), 8.32 (single peak, 1H), 7.79 (double peak, 1H); MS data: m/z 210 [M+H]+.
