[Br:1][C:2]1[CH:10]=[C:9]2[C:5]([CH:6]=[N:7][NH:8]2)=[C:4]([N+:11]([O-:13])=[O:12])[CH:3]=1.C(O)(C(F)(F)F)=O.C(Cl)Cl.C(=O)(O)[O-].[Na+].[O:29]1[CH:34]=[CH:33][CH2:32][CH2:31][CH2:30]1>>[Br:1][C:2]1[CH:3]=[C:4]([N+:11]([O-:13])=[O:12])[C:5]2[C:9]([CH:10]=1)=[N:8][N:7]([CH:30]1[CH2:31][CH2:32][CH2:33][CH2:34][O:29]1)[CH:6]=2To 6-bromo-4-nitro-1H-indazole (10 g, available from Sinova Ltd) in dihydropyran (100 ml) was added TFA (0.068 ml) and the reaction was heated for 1.5 hours at reflux. After cooling, 180 ml DCM and 50 ml saturated sodium bicarbonate solution was added and stirred for 10 minutes. The DCM was separated from the aqueous which was re-washed with DCM (70 ml). The combined organic layers were passed through a hydrophobic frit and evaporated to dryness. The residual solid was triturated with ether then filtered. The solid material was dissolved in DCM and purified by chromatography on silica on the ISCO Companion, using an isocratic gradient of DCM. Purified fractions were combined and evaporated to dryness to afford the title compound (7.78 g).
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