[Br:1][C:2]1[C:3]([F:12])=[CH:4][C:5]([N+:9]([O-])=O)=[C:6]([OH:8])[CH:7]=1.O.O.[Sn](Cl)Cl.C[CH2:19][OH:20].C(N1C=CN=C1)(N1C=CN=C1)=O>C1COCC1>[Br:1][C:2]1[C:3]([F:12])=[CH:4][C:5]2[NH:9][C:19](=[O:20])[O:8][C:6]=2[CH:7]=1To a 100 mL of round bottom flask was added 5-bromo-4-fluoro-2-nitrophenol (0.98 g, 4.15 mmol), tin(II) chloride dihydrate (4.73 g, 20.76 mmol) and 5 mL of EtOH. The reaction mixture was heated to 70° C. for 30 minutes. The reaction mixture was concentrated and washed with saturated NaHCO3 solution, and extracted with DCM (100 mL×3), and concentrated providing the crude product. 1,1′-Carbonyldiimidazole (808 mg, 4983 mmol) was added to the crude product in 20 mL of THF. The reaction mixture was heated at reflux overnight. The reaction mixture was concentrated and purified with silica gel column chromatography, eluting with 0-30% EtOAc/hexane to give 6-bromo-5-fluorobenzo[d]oxazol-2(3H)-one (690 mg, 71.6% yield). MS m/z: 232 (M+1).
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