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General procedure for the synthesis of 7-fluoroquinazoline-2,4(1H,3H)-dione from 2-amino-4-fluorobenzoic acid: 2-amino-4-fluorobenzoic acid (5.00 g, 32.2 mmol) was dissolved in water (180 mL), glacial acetic acid (3 mL) was added, and the temperature was heated to 35 °C. At this temperature, a suspension of sodium cyanate (5.24 g, 80.6 mmol) in water (20 mL) was slowly added. The residual sodium cyanate was washed with three portions of water (10 mL each). After continuing to stir the reaction mixture for 30 min, sodium hydroxide (35 g, 880 mmol) was slowly added and a white precipitate was observed to be produced. Water (100 mL) was added to dilute, the reaction mixture was cooled to 0 °C and the pH was adjusted with concentrated hydrochloric acid to 4. The white solid was collected by filtration, washed with water and dried under vacuum to afford 7-fluoroquinazoline-2,4(1H,3H)-dione 4.1 g in 71% yield.