Step 22d. Synthesis of 4-chloro-7-methoxy-6-nitroquinazoline (Compound 0305): 7-methoxy-6-nitroquinazolin-4(3H)-one (Compound 0304, 3.8 g, 17.2 mmol) was suspended in phosphorus oxychloride (POCl3, 75 mL), and the reaction mixture was heated to reflux and maintained for 4 hours. Upon completion of the reaction, excess POCl3 was removed by distillation under reduced pressure. the residue was dissolved in a mixture of dichloromethane (50 mL) and aqueous sodium bicarbonate (NaHCO3) (50 mL), and the organic layer was separated and dried over anhydrous sodium sulfate. The solvent was removed by concentration under reduced pressure to afford the target product 4-chloro-7-methoxy-6-nitroquinazoline (compound 0305, 3.4 g, 83% yield). The product was characterized by 1H NMR (DMSO-d6): δ 4.05 (s, 3H), 7.44 (s, 1H), 8.27 (s, 1H), 8.53 (s, 1H).
