[F:1][C:2]1[N:7]=[C:6]2[NH:8][N:9]=[C:10]([C:11]([O:13]C(C)(C)C)=O)[C:5]2=[CH:4][CH:3]=1.C([O-])(=O)C.[NH4+:22]>FC(F)(F)C(O)=O>[F:1][C:2]1[N:7]=[C:6]2[NH:8][N:9]=[C:10]([C:11]([NH2:22])=[O:13])[C:5]2=[CH:4][CH:3]=1t-Butyl 6-fluoro-1H-pyrazolo[3,4-b]pyridine-3-carboxylate (8.90 g, 37.5 mmole) was dissolved in 30 mL of trifluoroacetic acid and allowed to stand undisturbed for 2 hours. The solvent was then evaporated and the residue was dissolved in 30 mL of DMF. N,N'-Carbonyldiimidazole (7.0 g, 43.2 mmol) was added and the reaction mixture was stirred overnight. Ammonium acetate (8.7 g, 113 mmol) was then added to the resulting suspendion and stirring was continued for 4 hours. The solvent was evaporated under high vacuum and the residue was triturated well with H2O to give 6.02 g (89%) of product after drying. An analytical sample was obtained by recrystallization from HOAc, mp 295° C. (dec).
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