[F:1][C:2]1[CH:3]=[C:4]2[C:10](N)=[N:9][NH:8][C:5]2=[N:6][CH:7]=1.N(OCCC(C)C)=O.[I-:20].[Na+]>C1COCC1.C(OCC)C.CC(C)=O>[F:1][C:2]1[CH:3]=[C:4]2[C:10]([I:20])=[N:9][NH:8][C:5]2=[N:6][CH:7]=110 g (65.75 mmol) of 5-fluoro-1H-pyrazolo[3,4-b]pyridin-3-amine was put in THF (329 ml) and cooled to 0° C. Then 16.65 ml (131.46 mmol) of boron trifluoride/diethyl ether complex was slowly added. The reaction mixture was cooled further to −10° C. Then a solution of 10.01 g (85.45 mmol) of isopentyl nitrite in THF (24.39 ml) was slowly added and stirred for a further 30 min. The mixture was diluted with cold diethyl ether (329 ml) and the resultant solid was filtered off. The resultant diazonium salt was added in portions to a cold (0° C.) solution of 12.81 g (85.45 mmol) of sodium iodide in acetone (329 ml) and the mixture was stirred for a further 30 min at RT. The reaction mixture was added to ice water (1.8 l) and was extracted twice with ethyl acetate (487 ml each time). The combined organic phases were washed with saturated aqueous sodium chloride solution (244 ml), dried, filtered and concentrated by evaporation. 12.1 g (86% purity, 60% of theor.) of the title compound was obtained as a solid. The raw product was reacted without further purification.
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