6-Bromo-3-fluoro-4-nitro-1-(phenylsulfonyl)-1H-indazole → 6-Bromo-3-fluoro-1-(phenylsulfonyl)-1H-indazol-4-amine

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Reaction Steps

6-Bromo-3-fluoro-4-nitro-1-(phenylsulfonyl)-1H-indazole (5.9 g, 14.74 mmol) was suspended in acetic acid (60 ml) and to it added iron powder (4.12 g, 73.7 mmol). The suspension was heated to reflux for 2 h, then the reaction mixture was cooled, diluted with 100 ml EtOAc and filtered through celite. The filter cake was washed well with ethyl acetate then the filtrate basified till the colour moved from the aqueous layer to the organic (around pH 8-9). The biphasic system was then stirred for around 5 minutes and the aqueous layer turned cloudy. The layers were then separated, the aqueous washed with ethyl acetate and the combined organics washed with brine, dried (MgSO4), filtered and concentrated in vacuo. The residue was dry loaded onto a 330 g silica cartridge, purified on a 0-100% EtOAc/Cyclohexane gradient and the relevant fractions combined and concentrated to yield the title compound as a yellow solid (2.4 g).

Provenance & Evidence