[CH:1]1([CH2:4][N:5]2[C:10](=[O:11])[C:9](O)=[N:8][C:7]3[CH:13]=[CH:14][CH:15]=[N:16][C:6]2=3)[CH2:3][CH2:2]1.P(Br)(Br)([Br:19])=O.C(=O)([O-])[O-].[Na+].[Na+]>ClC(Cl)C>[Br:19][C:9]1[C:10](=[O:11])[N:5]([CH2:4][CH:1]2[CH2:3][CH2:2]2)[C:6]2[N:16]=[CH:15][CH:14]=[CH:13][C:7]=2[N:8]=1700 mg (3.22 mM) of 4-(cyclopropylmethyl)-2-hydroxypyrido[2,3-b]pyrazin-3(4H)-one and 972.3 mg (3.22 mM) of phosphorus oxybromide at 95% in 10 ml of dichloroethane were refluxed for 16H under stirring. The reaction mixture was then basified with an aqueous solution of sodium carbonate and the aqueous layer was extracted with dichloromethane. The organic layer was separated, washed with water, dried on anhydrous sodium sulfate and the solvent was removed under vacuum. The compound was further purified by silica gel column chromatography, using dichloromethane as eluant, to give, after evaporation, 650 mg of 2-bromo-4-(cyclopropylmethyl)pyrido[2,3-b]pyrazin-3(4H)-one as a white solid. Yield: 66.5%.
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