反应详情

tert-Butyl 3-methyl-6-nitro-1H-indazole-1-carboxylate (7.40 g, 26.7 mmol) was dissolved in EtOH (534 mL). To the solution was added Pd/C (10 wt %, 1.42 g, 1.33 mmol). The mixture was flushed with H2, and placed under an atmosphere of H2 at atmospheric pressure at rt for about 6 h. The mixture was filtered through Celite® and washed through with MeOH. The solvents were removed under reduced pressure. The residue was purified by column chromatography (120 g silica gel) eluting with 20-80% EtOAc/heptane to give a solid. The solid redissolved in DCM (20 mL) and heptane (50 mL) was added. The mixture was concentrated to remove the DCM. The resulting precipitate was collected by vacuum filtration and washed with heptane (20 mL) to provide tert-butyl 6-amino-3-methyl-1H-indazole-1-carboxylate (4.57 g, 69%): LCMS (Table 2, Method c) Rt=1.81 min.; MS m/z: 248 (M+H)+, 1H NMR (400 MHz, DMSO-d6) δ 7.36 (d, J=8.5 Hz, 1H), 7.14 (d, J=1.7 Hz, 1H), 6.59 (dd, J=8.5, 1.9 Hz, 1H), 5.71 (d, J=19.5 Hz, 2H), 2.33 (s, 3H), 1.58 (s, 9H).

1. customThe mixture was flushed with H2
2. filtrationThe mixture was filtered through Celite®
3. washwashed through with MeOH
4. customThe solvents were removed under reduced pressure
5. customThe residue was purified by column chromatography (120 g silica gel)
6. washeluting with 20-80% EtOAc/heptane
7. customto give a solid
8. concentrationThe mixture was concentrated
9. customto remove the DCM
10. filtrationThe resulting precipitate was collected by vacuum filtration
11. washwashed with heptane (20 mL)