[Br:1][C:2]1[CH:3]=[N:4][C:5]([C:9]([O:11][CH2:12][CH3:13])=[O:10])=[N+:6]([O-])[CH:7]=1.FC(F)(F)C(OC(=O)C(F)(F)F)=[O:17]>CN(C)C=O>[Br:1][C:2]1[C:3](=[O:17])[NH:4][C:5]([C:9]([O:11][CH2:12][CH3:13])=[O:10])=[N:6][CH:7]=1To a 0° C. cooled solution of 5-bromo-2-(ethoxycarbonyl)pyrimidine 1-oxide (3, 0.62 g, 2.5 mmol) in dimethylformamide (6 mL), trifluoroacetic anhydride (3.1 g, 15 mmol) was added dropwise. The reaction mixture was heated at 50° C. for 18 h. TLC showed consumption of starting material and solvent was removed under reduced pressure. The residue was triturated with methanol (2 mL) and filtered. The solid was washed with diethyl ether and dried under reduced pressure to afford ethyl 5-bromo-6-oxo-1,6-dihydropyrimidine-2-carboxylate (4) as off white solid. Yield: 0.21 g, 34%; MS (ESI) m/z 245.09 [M−1]−.
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