Synthesis
Step 2: Preparation of 1-methyl-1H-indazol-5-amine
Iron powder (5.04 g, 90.3 mmol) was added batchwise to a mixed solution of ethanol (225 mL) and water (100 mL) of 1-methyl-5-nitro-1H-indazole (4.00 g, 22.6 mmol), followed by ammonium chloride (12.1 g, 225 mmol). The reaction mixture was stirred and heated at 80 °C for 1 hour. After completion of the reaction, the reaction mixture was diluted with dichloromethane (500 mL) and filtered to remove insoluble material. The organic layer was separated, dried with anhydrous magnesium sulfate and concentrated under reduced pressure to give the title compound 1-methyl-1H-indazol-5-amine (3.29 g, 99% yield).
HPLC analytical conditions: SYMMETRY C18 column (3.5 μm, 4.6 × 30 mm); mobile phase: acetonitrile/water gradient containing 0.1% trifluoroacetic acid (2%-98% acetonitrile, 10 min); flow rate: 2 mL/min; retention time: 1.06 min.
Mass spectrum (MS): m/z 147.2 ([M+H]+).
References
[1] Patent: WO2007/88478, 2007, A1. Location in patent: Page/Page column 19
[2] Tetrahedron, 2008, vol. 64, # 28, p. 6711 - 6723
[3] Journal of Chemical Research, Miniprint, 1990, # 11, p. 2601 - 2615
[4] Patent: WO2013/100632, 2013, A1. Location in patent: Page/Page column 95
[5] Patent: US2014/371219, 2014, A1. Location in patent: Paragraph 0662; 0663; 0664
