[CH3:1][O-:2].[Na+].[CH3:4][C:5]1[C:14]([Cl:15])=[C:13]([Cl:16])[CH:12]=[C:11]2[C:6]=1[N:7]=[C:8](Cl)[C:9](Cl)=[N:10]2.[O:19]1[CH2:23]CCC1>C(OCC)(=O)C>[Cl:15][C:14]1[C:5]([CH3:4])=[C:6]2[C:11](=[CH:12][C:13]=1[Cl:16])[N:10]=[C:9]([O:2][CH3:1])[C:8]([O:19][CH3:23])=[N:7]2A solution of sodium methoxide (38 ml, 25% solution in methanol, 175 mmol) was added over 10 minutes to a solution of 5-methyl-2,3,6,7-tetrachloroquinoxaline (from step (e), 21 g, 74 mmol) in dry tetrahydrofuran (200 ml) at 20° C. There was a mildly exothermic reaction followed by formation of a precipitate. After 1 h the mixture was diluted with ethyl acetate (3 L), washed with water (1 L), dried (MgSO4) and concentrated under reduced pressure to give 6,7-dichloro-2,3-dimethoxy-5-methylquinoxaline (20.3 g, 100%).
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