[CH3:1][N:2]1[C:11]2[C:6](=[CH:7][CH:8]=[CH:9][CH:10]=2)[N:5]=[C:4]([C:12]([OH:14])=[O:13])[C:3]1=[O:15].C(Cl)(=O)C(Cl)=O.[C:22]1(=O)[CH2:27][CH2:26][CH2:25][C:24](=[O:28])[CH2:23]1.C(N(CC)CC)C>ClCCl.CN(C)C=O>[CH3:1][N:2]1[C:11]2[C:6](=[CH:7][CH:8]=[CH:9][CH:10]=2)[N:5]=[C:4]([C:12]([O:14][C:22]2[CH2:27][CH2:26][CH2:25][C:24](=[O:28])[CH:23]=2)=[O:13])[C:3]1=[O:15]4.6 g (22.5 mmol) of 1-methyl-2-oxo-1,2-dihydroquinoxaline-3-carboxylic acid was dissolved in dichloromethane (200 mL), and N,N-dimethylformamide (0.5 mL) and 4.3 g (33.9 mmol) of oxalyl chloride were added thereto. The mixture was stirred for 1 hour at room temperature. The reaction mixture was concentrated under reduced pressure, and the obtained residue was dissolved in dichloromethane (100 mL). This solution was added dropwise at room temperature to a solution prepared by dissolving 2.8 g (25.0 mmol) of 1,3-cyclohexanedione and 2.7 g (26.7 mmol) of triethylamine in dichloromethane (100 mL). The mixture was stirred for 1 hour at room temperature, and then, the reaction mixture was washed with water, and dried over anhydrous sodium sulfate. The inorganic matter was separated by filtration, and then the solvent was distilled off under reduced pressure, to obtain 6.3 g (yield 94%) of 3-oxo-1-cyclohexenyl 1-methyl-2-oxo-1,2-dihydroquinoxaline-3-carboxylate as a yellow solid.
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