A solution of trityl chloride (8.5 g, 30.5 mmol) in DMF (80 mL) was added dropwise to the solution of 3-(6-bromo-pyridin-2-yl)-6-chloro-1H-pyrazolo[3,4-d]pyrimidine (from Example 30 supra) (8.0 g, 25.7 mmol) and Et3N (12 mL, 83.2 mmol) in DMF (100 mL) at room temperature. The reaction mixture was stirred at room temperature for 2 hours then poured into water and extracted with ethyl acetate. The organic solution was dried with anhydrous Na2SO4. After filtration and concentration, the residue was purified by column chromatography (silica gel, petroleum ether:ethyl acetate, 20:1) to give 3-(6-bromo-pyridin-2-yl)-6-chloro-1-trityl-1H-pyrazolo[3,4-d]pyrimidine as a white powder. (Yield 3.8 g, 27%).
