Step 2: Synthesis of 6-bromo-3,4-dihydroquinazolin-2(1H)-one; Triethylamine (0.454 g, 4.5 mmol) was added slowly and dropwise to a solution of tetrahydrofuran (20 mL) containing triphosgene (0.445 g, 1.5 mmol) at 0 °C and under nitrogen protection. After stirring the reaction mixture for 30 minutes, a solution of 2-aminomethyl-4-bromoaniline (0.201 g, 1 mmol) in tetrahydrofuran (10 mL) was added slowly and dropwise. The reaction mixture was continued to be stirred at room temperature for 16 hours. Upon completion of the reaction, the reaction mixture was diluted with water (15 mL) and the pH was adjusted to 8-9 with 1 M aqueous sodium hydroxide solution.Subsequently, it was extracted three times with ethyl acetate (30 mL). The organic layers were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by recrystallization from a solvent mixture of dichloromethane and ethyl ether to afford 6-bromo-3,4-dihydroquinazolin-2-one (0.13 g, 57.5% yield) as a yellow solid.1H NMR (400 MHz, DMSO-d6) δppm: 9.12 (s, 1H), 7.29 (s, 1H), 7.27 (d, J=8.4 Hz. 1H), 6.87 (s, 1H), 6.70 (d, J=8.4Hz, 1H), 4.28 (s, 2H).
