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General procedure for the synthesis of 7-bromo-2H-pyrido[3,2-b][1,4]oxazin-3(4H)-ones from 2H-pyrido[3,2-b][1,4]oxazin-3(4H)-ones: to 2H-pyrido[3,2-b][1,4]oxazin-3(4H)-ones (1 g, 6.66 mmol) of N,N-dimethylformamide (DMF. 30 mL) solution was slowly added bromine (0.480 mL, 9.32 mmol) dropwise. The reaction mixture was stirred at room temperature for 12 hours. Upon completion of the reaction, deionized water was added to induce precipitate formation and the precipitate was collected by filtration. The resulting solid was dried overnight in a freeze dryer to afford 7-bromo-2H-pyrido[3,2-b][1,4]oxazin-3(4H)-one (1.16 g, 76% yield). The product was characterized by 1H NMR (DMSO-d6): δ 11.43 (s, 1H), 8.04 (d, J = 2.0 Hz, 1H), 7.65 (d, J = 2.0 Hz, 1H), 4.67 (s, 2H).

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