[N+:1]([C:4]1[CH:12]=[CH:11][CH:10]=[C:9]2[C:5]=1[CH:6]=[N:7][NH:8]2)([O-:3])=[O:2].C(=O)([O-])[O-].[K+].[K+].[CH2:19](Br)[C:20]1[CH:25]=[CH:24][CH:23]=[CH:22][CH:21]=1.O>CN(C=O)C>[CH2:19]([N:8]1[C:9]2[C:5](=[C:4]([N+:1]([O-:3])=[O:2])[CH:12]=[CH:11][CH:10]=2)[CH:6]=[N:7]1)[C:20]1[CH:25]=[CH:24][CH:23]=[CH:22][CH:21]=1To a solution of 4-nitro-1H-indazole (1.00 g; 6.13 mmol) in dry DMF (15 mL) under an atmosphere of dry nitrogen was added potassium carbonate (1.69 g; 12.3 mmol) and benzyl bromide (1.15 g; 6.74 mmol). The mixture was stirred at ambient temperature for 24 hours. Water (50 mL) was added and the mixture was extracted with ethyl acetate. The combined organic extracts were dried over sodium sulfate and filtered. The solvent was removed under reduced pressure to give a brown solid which was a mixture of two regioisomers. The desired isomer was separated by chromatography on silica (Biotage SNAP column, 100 g), eluting with hexane/ethyl acetate (20:1 to 10:1 to 5:1). The desired (N1) regioisomer was the first to elute. The fractions containing the desired product were evaporated under reduced pressure to give 1-benzyl-4-nitro-1H-indazole (730 mg) as a yellow solid.
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