Synthesis
Step B: Preparation of tert-butyl 6-amino-1H-indazole-1-carboxylate: To a solution of tert-butyl 6-nitro-1H-indazole-1-carboxylate (0.88 g, 3.34 mmol) in methanol (20 mL) was added 10% Pd/C catalyst (0.355 g, 0.334 mmol). After displacing the air in the reaction system with nitrogen, the hydrogenation reaction was carried out under hydrogen (30 psi) atmosphere for 2 hours. After completion of the reaction, the reaction mixture was filtered through GF/F filter paper and the filtrate was concentrated to afford the target product tert-butyl 6-amino-1H-indazole-1-carboxylate (0.76 g, 98% yield). Mass spectrometry analysis (APCI-positive ion mode) showed [M+1]+ peak of 233.8.
References
[1] Patent: US2010/63066, 2010, A1. Location in patent: Page/Page column 35
[2] Journal of Medicinal Chemistry, 2002, vol. 45, # 4, p. 944 - 954
[3] Patent: US6372759, 2002, B1
[4] Bioorganic and Medicinal Chemistry, 2013, vol. 21, # 13, p. 3821 - 3830
[5] Asian Journal of Chemistry, 2014, vol. 26, # 22, p. 7539 - 7543
