875781-18-3

General procedure for the synthesis of 5-bromo-3-iodo-1H-pyrazolo[3,4-B]pyrimidines (IV-A-I) from 5-bromo-1H-pyrazolo[3,4-B]pyridines: to a stirred solution of 5-bromo-1H-pyrazolo[3,4-B]pyridines (III-A-1) (1g, 5.05mmol) in DMF (14mL) was added in one go crushed KOH pellets (1.06 g, 19.03 mmol). after 11 min, I2 (1.15 g, 4.54 mmol) was added and the mixture was stirred vigorously for 3.5 h. The mixture was then partially purified in vacuo. The mixture was then partially concentrated in vacuo, diluted with EtOAc (40 mL) and saturated NaHCO3 solution (20 mL) and partitioned. The aqueous layer was extracted with EtOAc (2 x 20 mL). The combined organic layers were dried (MgSO4), filtered and concentrated to give a 1:1 mixture of III-A-1 and IV-A-1 (1.377 g). The mixture was redissolved in 1,4-dioxane (14 mL) and treated with solid NaOH (0.7 g). The mixture was stirred at room temperature for 5 min and I2 (0.7 g) was added. The mixture was stirred at 40 °C for 23 h. The mixture was diluted with EtOAc (50 mL) and washed with saturated aqueous Na2S2O3 (30 mL). The aqueous layer was extracted with EtOAc (2 x 30 mL), and the combined organic extracts were dried (MgSO4), filtered and concentrated to afford 5-bromo-3-iodo-1H-pyrazolo[3,4-B]pyrimidine (IV-A-I) (1.585 g, 97%).1H NMR (400 MHz; CDCl3) δ 7.94 (d, J=2.1 Hz, 1H) 8.55 (d, J=2.1Hz, 1H), 10.85 (brs, 1H, NH).

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