General procedure for the synthesis of 2,4-dichloro-7-fluoroquinazoline from 7-fluoroquinazoline-2,4(1H,3H)-dione: 7-fluoroquinazoline-2,4(1H,3H)-dione (5.26 g, 29.2 mmol) was mixed with phosphorus trichloride (85 mL) and stirred for 3 days under reflux conditions. Upon completion of the reaction, the mixture was cooled to room temperature and slowly poured into ice water. The resulting solid product was collected by filtration and dried under vacuum to afford the title compound 2,4-dichloro-7-fluoroquinazoline (3.82 g) as a yellow solid. The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3): δ 8.32 (m, 1H), 7.63 (d, 1H), 7.49 (t, 1H).
