Synthesis
Tert-butyl 5-bromo-1H-indazole-1-carboxylate (10.1 mmol) and pinacol ester of bisboronic acid (11.1 mmol) were used as raw materials for the reaction catalyzed by palladium(II) acetate (1.01 mmol) and dichloro[1,1'-bis(diphenylphosphino)ferrocene]palladium(II) (1.01 mmol) with the addition of potassium acetate (30.3 mmol) in triethylamine ( 1.5 mL) solution of potassium acetate (30.3 mmol) and 1,4-dioxane (60 mL) as a solvent, and the reaction was carried out at 110 °C overnight. After completion of the reaction, the mixture was concentrated under reduced pressure and the residue was purified by fast column chromatography (eluent: 5% ethyl acetate/petroleum ether) to afford the target product 1-tert-butoxycarbonylindazole-5-boronic acid pinacol ester as a yellow solid in 74% yield.
References
[1] Patent: WO2011/66211, 2011, A1. Location in patent: Page/Page column 69-70
[2] Organic Letters, 2009, vol. 11, # 13, p. 2860 - 2863
[3] Patent: WO2010/59943, 2010, A2. Location in patent: Page/Page column 83; 84
[4] Patent: WO2006/86705, 2006, A1. Location in patent: Page/Page column 89
[5] Patent: US2008/153813, 2008, A1. Location in patent: Page/Page column 22
