General procedure for the synthesis of 4-chloro-7-methoxyquinazoline from 7-methoxyquinazolin-4(1H)-one: 7-methoxyquinazolin-4(1H)-one (1 g, 5.68 mmol) was dissolved in phosphorus trichloride (25 ml) and the reaction was carried out at reflux for 18 hours. After completion of the reaction, the solvent was removed by distillation under reduced pressure and the residue was diluted with cold water. Subsequently, the aqueous solution was alkalized with solid sodium carbonate and extracted with ethyl acetate. The organic layers were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether/ethyl acetate = 80:20) to afford the target compound 4-chloro-7-methoxyquinazoline (0.87 g, 72.5% yield) as a light yellow solid.1H NMR (400 MHz, DMSO-d6) δ: 8.52 (br s, 1H), 8.07-8.05 (d, J = 8 Hz. 1H), 7.20-7.17 (m, 2H), 3.91 (s, 3H); MS (ESI) m/z: 195.0 [M+H]+.
