Example 4A Step 2: 6,7-difluoro-4-hydroxyquinazoline (910 mg, 5 mmol) was added to trichlorophos (15 mL) followed by triethylamine (700 μL, 5 mmol). The reaction mixture was heated to reflux at 100 °C for 4 h. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure. The resulting solid was ground with ethyl acetate (2 × 100 mL), and the combined organic phases were rapidly filtered through a silica gel column to afford 4-chloro-6,7-difluoroquinazoline (870 mg, 4.35 mmol, 87% yield). m/z 201 ([M + H]+) by LC-MS (ESI).
