[CH3:1][C:2]1[C:3](=O)[NH:4][CH:5]=[C:6]([C:8]([O:10][CH3:11])=[O:9])[N:7]=1.O=P(Cl)(Cl)[Cl:15]>CN(C=O)C>[Cl:15][C:3]1[N:4]=[CH:5][C:6]([C:8]([O:10][CH3:11])=[O:9])=[N:7][C:2]=1[CH3:1]To a solution of methyl 4,5-dihydro-6-methyl-5-oxo-2-pyrazine carboxylate (M. Mano, T. Seo, K. Imai, Chem. Pharm. Bull 10:3057-3063, 1980) in DMF (20 mL) was added POCl3 (20 mL). The reaction was refluxed for 0.5 h and then poured into ice. The aqueous layer was extracted with CHCl3 dried (MgSO4) and concentrated. The residue was chromatographed (SiO2, CHCl3) to provide the title compound (2.34 g, 52% yield); m.p. 49°-50° C.
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