The general procedure for the synthesis of 2-chloro-4-oxo-6-fluoroquinazoline from 2,4-dichloro-6-fluoroquinazoline was as follows: 2,4-dichloro-6-fluoroquinazoline (0.21 g, 0.97 mmol) was dissolved in tetrahydrofuran (1 mL) in a 50 mL single-neck flask. After 2,4-dichloro-6-fluoroquinazoline was completely dissolved, aqueous sodium hydroxide solution (1 M, 8 mL) was added and the reaction mixture was stirred at room temperature and under nitrogen protection for 12 hours. After completion of the reaction, the pH of the mixture was adjusted to 5-6 with glacial acetic acid.Subsequently, the reaction mixture was extracted with ethyl acetate (10 mL × 2). The organic phases were combined and concentrated to give the crude product. The crude product was purified by silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 4/1) as eluent to yield 2-chloro-4-oxo-6-fluoroquinazoline (white solid, 0.16 g, 83% yield). The product was confirmed by mass spectrometry (ESI, positive ion mode), m/z: 199.1 [M + H]+; 1H NMR (CDCl3, 400 MHz) δ (ppm): 10.93 (s, 1H), 7.92 (dd, J = 8.0 Hz, 3.0 Hz, 1H), 7.71 (dd, J = 9.0 Hz, 4.8 Hz, 1H), 7.53 ( td, J = 8.4 Hz, 3.0 Hz, 1H).
