[CH3:1][O:2][C:3]1[CH:13]=[CH:12][C:6]2[NH:7][C:8](=[O:11])[CH2:9][O:10][C:5]=2[CH:4]=1.[H-].[Na+].[CH3:16]I.O>CN(C=O)C>[CH3:1][O:2][C:3]1[CH:13]=[CH:12][C:6]2[N:7]([CH3:16])[C:8](=[O:11])[CH2:9][O:10][C:5]=2[CH:4]=1
7-Methoxy-4H-benzo[1,4]oxazin-3-one (11.61 g, 0.065 mol) in 100 mL dry DMF was stirred at 0° C. under nitrogen. Sodium hydride (60%, 2.85 g, 0.072 mol) was added in portions over 30 minutes, after which methyl iodide (4.44 mL, 0.071 mol) was added dropwise. The reaction mixture was stirred at 0° C. for 2.5 hours, then poured into 1400 mL water. The resulting aqueous mixture was extracted four times with 400 mL EtOAc, and the combined organic layers were washed with water, then brine, dried (MgSO4), filtered, and evaporated under reduced pressure to provide 13.07 g of 7-Methoxy-4-methyl-4H-benzo[1,4]oxazin-3-one. (M+H)=194.
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