[Cl:1][C:2]1[N:7]=[C:6]2[NH:8][N:9]=[CH:10][C:5]2=[CH:4][N:3]=1.CS(O)(=O)=O.[O:16]1[CH:21]=[CH:20][CH2:19][CH2:18][CH2:17]1>C1COCC1>[Cl:1][C:2]1[N:7]=[C:6]2[N:8]([CH:17]3[CH2:18][CH2:19][CH2:20][CH2:21][O:16]3)[N:9]=[CH:10][C:5]2=[CH:4][N:3]=1To a suspension of 6-chloro-1H-pyrazolo[3,4-d]pyrimidine (1.00 g, 6.47 mmol) (Ark, Cat. No. AK-30782) in THF (10 mL) at r.t. was added methanesulfonic acid (84 μL, 1.3 mmol), followed by dihydropyran (1.77 mL, 19.4 mmol). The mixture was stirred at r.t. over weekend. The reaction mixture was quenched with saturated aqueous NaHCO3, and extracted with ethyl acetate (3×20 mL). The combined organic layers were washed with brine, dried over MgSO4, filtered and concentrated under reduced pressure to afford the crude product which was directly used in the next step reaction without further purification. LCMS (M-84+H)+: m/z=155.1/157.0.
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