[NH2:1][C:2]1[N:3]=[CH:4][C:5]([CH:8]2[CH2:13][NH:12][C:11](=[O:14])[CH2:10][CH2:9]2)=[N:6][CH:7]=1.C1C(=O)N([Br:22])C(=O)C1>>[NH2:1][C:2]1[N:3]=[CH:4][C:5]([CH:8]2[CH2:13][NH:12][C:11](=[O:14])[CH2:10][CH2:9]2)=[N:6][C:7]=1[Br:22]To 5-(5-aminopyrazin-2-yl)piperidin-2-one (25 mg, 0.13 mmol) acetonitrile (10 mL) solution at 0° C. was added NBS (23.2 mg, 0.13 mmol) and the reaction mixture was stirred at 0° C. for 30 min, then at room temperature for 4 h. The reaction mixture was concentrated, and the residue was basified by 1 N NaOH (140 ul), diluted with methanol (2 mL), concentrated. The residue was triturated with EtOAc (3×1 mL), and the EtOAc supernatants were collected, combined and concentrated and a light solid was obtained as crude 5-(5-amino-6-bromopyrazin-2-yl)piperidin-2-one which was used in next step without further purification. LCMS (m/z): 241/243 (MH+), 0.41 min.
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