[Br:1][C:2]1[CH:15]=[CH:14][C:13]2[O:12][C:11]3[C:6](=[N+:7]([O-])[CH:8]=[CH:9][C:10]=3[N+:16]([O-:18])=[O:17])[C:5](=[O:20])[C:4]=2[CH:3]=1.P(Cl)(Cl)([Cl:23])=O>CN(C=O)C.C1(C)C=CC=CC=1>[Br:1][C:2]1[CH:15]=[CH:14][C:13]2[O:12][C:11]3[C:6](=[N:7][C:8]([Cl:23])=[CH:9][C:10]=3[N+:16]([O-:18])=[O:17])[C:5](=[O:20])[C:4]=2[CH:3]=1A suspension of 8-bromo-4-nitro-10-oxo-10H-chromeno[3,2-b]pyridine 1-oxide (90 mg, 0.267 mmol) in 1 mL of dry DMF was added dropwise to a solution of phosphorus oxychloride (44.0 μL, 0.481 mmol) in 0.2 mL of DMF and 0.5 mL of toluene at 0° C. After stirring at 0° C. for 0.5 h, the reaction was 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=100:3) gave 8-bromo-2-chloro-4-nitro-10H-chromeno[3,2-b]pyridin-10-one as a light yellow solid.
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