[C:1]([O:5][C:6](=[O:14])[NH:7][C@H:8]1[CH2:11][C@H:10]([NH:12][NH2:13])[CH2:9]1)([CH3:4])([CH3:3])[CH3:2].Cl[C:16]1[C:21]([C:22]#[N:23])=[CH:20][CH:19]=[CH:18][N:17]=1.C([O-])(=O)C.[Cs+].CS(C)=O>C(OCC)(=O)C.[Cu]>[C:1]([O:5][C:6](=[O:14])[NH:7][C@H:8]1[CH2:9][C@H:10]([N:12]2[C:16]3=[N:17][CH:18]=[CH:19][CH:20]=[C:21]3[C:22]([NH2:23])=[N:13]2)[CH2:11]1)([CH3:4])([CH3:2])[CH3:3]
Tert-butyl(trans-3-hydrazinylcyclobutyl)carbamate (4 g, 19.87 mmol), 2-chloro-3-cyanopyridine (3 g, 21.65 mmol), cesium acetate (14 g, 72.9 mmol), and copper powder (0.126 g, 1.987 mmol) were placed under nitrogen. Dry dimethylsulfoxide (20 mL) was added and the mixture stirred at 100° C. After 1 hour the mixture was cooled and diluted with ethyl acetate (300 mL). The mixture was filtered through a pad of celite and the filtrate washed with 10% saturated sodium bicarbonate (500 mL) before drying with magnesium sulfate and evaporating to dryness under reduced pressure. Purification using silica chromatography (10% (2 N ammonia in methanol) in dichloromethane) gave the desired tert-butyl(trans-3-(3-amino-1H-pyrazolo[3,4-b]pyridin-1-yl)cyclobutyl)carbamate (2.72 g, 8.97 mmol, 45.1% yield).
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