N-Benzyl-7-bromo-2-chlorothieno[3,2-d]pyrimidin-4-amine (310 mg, 0.874 mmol) was dissolved in acetonitrile (4 mL) and then bis(triphenylphosphine)palladium(II) dichloride (15 mg, 0.022 mmol), CuI (6 mg, 0.350 mmol), dicyclohexylamine (0.19 mL, 0.96 mmol) and ethynyltrimethylsilane (0.24 mL, 1.75 mmol) were added. After flowing nitrogen gas for 15 minutes, the reaction mixture was stirred at 80° C. for 14 hours. After cooling to room temperature, the reaction mixture was filtered with celite and washed with ethyl acetate (50 mL). The filtrate was washed with brine and concentrated by drying with MgSO4. Without purification, the resultant compound was dissolved in anhydrous tetrahydrofuran (5 mL) and then 1.0 M tetrabutylammonium fluoride dissolved in tetrahydrofuran (4.4 mL, 4.4 mmol) was added thereto. The reaction mixture was stirred at room temperature for 30 minutes and then concentrated. Purification of the mixture by silica gel chromatography (ethyl acetate/hexane: 2/8→3/7) yielded the target compound (180 mg, 68% yield).
