A suspension of methyl 4-(4-(8-oxa-3-azabicyclo[3.2.1]octan-3-yl)-6-chloro-1H-pyrazolo[3,4-d]pyrimidin-1-yl)piperidine-1-carboxylate (2.3 mmol), 4-aminophenylboronic acid pinacol ester (0.76 g, 3.5 mmol), and tetrakis(triphenylphosphine)palladium(0) (0.27 g, 10 mol %) in toluene/ethanol (1:1, 12 mL) and 2 M aqueous sodium carbonate solution (2.5 mL) was heated in a 10-20 mL Smith process vial in the microwave reactor for one hour at 120° C. The cooled mixture was partitioned between ethyl acetate and water. The aqueous phase was extracted three times with ethyl acetate. The combined extracts were washed with saturated aqueous sodium chloride solution, dried over anhydrous magnesium sulfate, filtered, and concentrated to dryness under reduced pressure. The crude residue was purified via reverse-phase high performance liquid chromatography using a Phenomenex Gemini column, running a gradient elution of 20% acetonitrile/80% of 0.07% aqueous ammonium hydroxide to 95% acetonitrile over 10 minutes. After the concentration of fractions under reduced pressure, methyl 4-(6-(4-aminophenyl)-4-(8-oxa-3-azabicyclo[3.2.1]octan-3-yl)-1H-pyrazolo[3,4-d]pyrimidin-1-yl)piperidine-1-carboxylate was obtained. MS (ES+): 464.6 (M+H)+
