[CH2:1]([NH:3][C:4]1[C:5]([NH2:10])=[CH:6][CH:7]=[CH:8][CH:9]=1)[CH3:2].O=[C:12]([CH3:16])[C:13](O)=[O:14]>CO>[CH2:1]([N:3]1[C:4]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[N:10]=[C:12]([CH3:16])[C:13]1=[O:14])[CH3:2]5,4 g (39,6 mM) of N-ethylbenzene-1,2-diamine and 2,76 ml (39,6 mM) of 2-oxopropanoic acid in 200 ml of methanol were refluxed for 8 h. The solvent was removed under vacuum. The residue was further purified by silica gel column chromatography, using dichloromethane, followed by dichloromethane/dimethylketone (95/5) as eluant to give 4,2 g of 1-ethyl-3-methyl-quinoxalin-2(1H)-one as a yellow solid. Yield: 56,7%.
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