[H-].[Na+].[NH2:3][C:4]1[C:9]([OH:10])=[CH:8][C:7]([Br:11])=[CH:6][N:5]=1.Br[C:13]([CH3:20])([CH3:19])[C:14](OCC)=[O:15].O>CN(C)C=O>[Br:11][C:7]1[CH:6]=[N:5][C:4]2[NH:3][C:14](=[O:15])[C:13]([CH3:20])([CH3:19])[O:10][C:9]=2[CH:8]=1
To a suspension of sodium hydride (60% dispersion in mineral oil, 0.68 g) in N,N-dimethylformamide (15 mL) was added dropwise a solution of 2-amino-5-bromopyridin-3-ol (3.22 g) in N,N-dimethylformamide (25 mL) at room temperature over a period of 10 minutes, and the mixture was stirred at room temperature for 20 minutes. To the mixture was added dropwise ethyl α-bromoisobutyrate (3.32 g) over a period of 20 minutes, and the reaction mixture was stirred at room temperature for 1 hour and at 80° C. for 2 hours. After cooling, to the reaction mixture was added cold water, and the mixture was extracted with ethyl acetate. The organic layer was washed successively water and brine, dried over magnesium sulfate and concentrated in vacuo by a half volume. The precipitates were collected by filtration to give 7-bromo-2,2-dimethyl-2H-pyrido[3,2-b][1,4]oxazin-3(4H)-one (0.90 g) was obtained as a powder.
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