General procedure for the synthesis of 6-bromoquinazolin-4-amine from 6-bromo-2H-benzo[d][1,3]oxazine-2,4(1H)-dione: 6-bromoisoanisic anhydride (2 g, 8.26 mmol) was bubbled with ammonia into a solution of DMF (20 mL) for 15 min at room temperature. Subsequently, degassing was carried out by bubbling nitrogen into the solution for 5 min while removing the generated (NH4)2CO3. The reaction solution was cooled to 0 °C and POCl3 (2 mL) was added dropwise slowly. After the dropwise addition, the reaction mixture was gradually warmed to 50 °C, maintained at this temperature for 30 min, and then cooled to room temperature. Water (6 mL) and 35% ammonium hydroxide solution (9 mL) were added to the cooled reaction mixture. The resulting mixture was heated at 100 °C for 1 hour and subsequently cooled to room temperature. During this process, a white precipitate was generated. The solid was collected by filtration to afford the white solid product 6-bromoquinazolin-4-amine (1.51 g, 82% yield). The product was confirmed by mass spectrometry (ES+) with m/e 224 [M+H]+ and molecular formula C8H6BrN3.
