[NH2:1][C@@H:2]1[CH2:7][CH2:6][CH2:5][CH2:4][C@@H:3]1[NH2:8].[C:9](OCC)(=[O:15])[C:10](OCC)=[O:11]>COC=COC>[NH:1]1[C@@H:2]2[C@@H:3]([CH2:4][CH2:5][CH2:6][CH2:7]2)[NH:8][C:10](=[O:11])[C:9]1=[O:15]To a solution of cis-1,2-diaminocyclohexane (4.8 g, 42 mmol) in dimethoxy ethylene (100 mL) was added slowly diethyl oxalate (28.5 mL, 210 mmol). The reaction mixture was stirred at room temperature for 0.5 h and at 100° C. for 2 h. After the suspension was cooled down to room temperature, the resulting white solid precipitate was collected by filtration. The precipitate was washed with diethyl ether and dried to yield (4aR,8aS)-octahydro-2,3-quinoxalinedione (4.6 g, 66%). LCMS: (M+H)+: 169.1.
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