OO.NC(N)=[O:5].FC(F)(F)C(OC(=O)C(F)(F)F)=O.[Br:20][C:21]1[CH:34]=[CH:33][C:32]2[O:31][C:30]3[C:25](=[N:26][CH:27]=[CH:28][C:29]=3[N+:35]([O-:37])=[O:36])[C:24](=[O:38])[C:23]=2[CH:22]=1>C(Cl)Cl>[Br:20][C:21]1[CH:34]=[CH:33][C:32]2[O:31][C:30]3[C:25](=[N+:26]([O-:5])[CH:27]=[CH:28][C:29]=3[N+:35]([O-:37])=[O:36])[C:24](=[O:38])[C:23]=2[CH:22]=1To a suspension of urea hydrogen peroxide (58.6 mg, 0.623 mmol) in 5 mL of CH2Cl2 at 0° C. was added dropwise trifluoroacetic anhydride (87 μL, 0.623 mmol). After stirring for 5 min at 0° C., a solution of 8-bromo-4-nitro-10H-chromeno[3,2-b]pyridin-10-one (80 mg, 0.249 mmol) in CH2Cl2 (5 mL) was added and the resulting reaction was stirred at rt for 1.5 h. The mixture was carefully quenched with saturated NaHCO3 and extracted with ethyl acetate (5×5 mL). The combined organics were dried over sodium sulfate, filtered and evaporated to dryness. Purification of the crude residue by column chromatography (CH2Cl2 to CH2Cl2/EA=10:1 to 5:1) gave 8-bromo-4-nitro-10-oxo-10H-chromeno[3,2-b]pyridine 1-oxide as an light yellow solid.
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