General procedure for the synthesis of 8-bromo-2-chloroquinazoline from 4-amino-8-bromo-2-chloroquinazoline: 8-bromo-2-chloroquinazolin-4-amine (12.93 g, 50 mmol) was dissolved in THF (500 mL) under stirring conditions, and isoamyl nitrite (23.43 g, 200 mmol) was added slowly dropwise over a dropwise period of 3 hours. Subsequently, the reaction mixture was continued to be stirred at 60 °C for 40 min. Upon completion of the reaction, the progress of the reaction was monitored by TLC (unfolding agent: PE:EA = 1:1). When the reaction was complete, the mixture was cooled to room temperature and the solvent was removed by distillation under reduced pressure. The residue was dissolved in DCM (300 mL) and the organic layer was washed sequentially with brine (100 mL) and water (100 mL). The organic layer was dried over anhydrous Na2SO4 and purified by column chromatography (eluent: DCM:PE = 1:1) to afford the target compound 8-bromo-2-chloroquinazoline as a yellow solid (8.21 g, 67% yield).1H NMR (DMSO-d6, 400 MHz): δ 9.66 (s, 1H), 8.45 (dd, J = 0.8, 7.6 Hz, 1H), 8.26 (dd, J = 0.8, 8.0 Hz, 1H), 7.73 (dd, J = 7.6, 8.0 Hz, 1H).
