A solution of 4-(methylsulfonyl)phenol (available from Matrix Scientific, Columbia, S.C., USA; 52 mg, 0.3 mmol) in tetrahydrofuran (3 mL) was cooled to 0° C. under argon. Sodium hydride (60% dispersion; 13.2 mg, 0.33 mmol) was added and the mixture was stirred for 10 min. 4-(4,6-Dichloro-pyrazolo[3,4-d]pyrimidin-1-yl)-piperidine-1-carboxylic acid tert-butyl ester (Intermediate 24; 100 mg, 0.27 mmol) was added and the mixture was stirred at room temperature for 4 h and then poured into saturated aqueous ammonium chloride solution. The mixture was extracted three times with ethyl acetate and the combined organic layers were washed with brine, dried (magnesium sulfate), filtered, evaporated and purified by column chromatography, eluting with 25-50% ethyl acetate/hexanes to give 4-[6-chloro-4-(4-methanesulfonyl-phenoxy)-pyrazolo[3,4-d]pyrimidin-1-yl]-piperidine-1-carboxylic acid tert-butyl ester (91 mg, 66%) as a white solid.
