25710-18-3

General procedure for the synthesis of 2,3-dichloro-pyrido[2,3-B]pyrazine-2,3(1H,4H)-dione from pyrido[2,3-B]pyrazine: 5 g (30.7 mmol) of pyrido[2,3-B]pyrazine-2,3(1H,4H)-dione was dissolved in 50 mL of phosphorus oxychloride (POCl3). The reaction mixture was heated to reflux for 24 hours. Upon completion of the reaction, the reaction solution was concentrated under vacuum to completely remove POCl3. The concentrated residue was carefully poured into ice water and extracted with ethyl acetate (EtOAc). The organic phases were combined, washed sequentially with saturated NaHCO3 solution and brine, and dried over anhydrous sodium sulfate. The dried organic phases were concentrated under reduced pressure to give a white powder of 2,3-dichloropyrido[3,2-b]pyrazine in 81% yield.

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