[CH3:1]C(C)([O-])C.[K+].[Cl:7][C:8]1[C:9]([NH:23][S:24]([CH2:27][CH3:28])(=[O:26])=[O:25])=[C:10]2[C:15](=[CH:16][C:17]=1[Cl:18])[N:14]=[C:13]([O:19][CH3:20])[C:12]([O:21][CH3:22])=[N:11]2.CI>CN(C)C=O>[Cl:7][C:8]1[C:9]([N:23]([CH3:1])[S:24]([CH2:27][CH3:28])(=[O:26])=[O:25])=[C:10]2[C:15](=[CH:16][C:17]=1[Cl:18])[N:14]=[C:13]([O:19][CH3:20])[C:12]([O:21][CH3:22])=[N:11]2Potassium tert-butoxide (67.5 mg, 1.1 mmol) was added to a stirred solution of N-(6,7-dichloro-2,3-dimethoxyquinoxalin-5-yl)ethanesulphonamide (Preparation 4) (200 mg, 0.55 mmol) in dry dimethylformamide (3 ml) under nitrogen at 20° C. After 5 minutes, methyl iodide (38 μl, 1.1 mmol) was added and the mixture was stirred at 20° C. for 2 hours. The mixture was concentrated under reduced pressure, partitioned between ethyl acetate and water, and the combined organic extracts were washed with dilute aqueous sodium hydroxide. The solution was dried (MgSO4) and concentrated under reduced pressure. The residue was purified by flash chromatography (eluting with dichloromethane) to give N-(6,7-dichloro-2,3-dimethoxyquinoxalin-5-yl)-N-(methyl)ethanesulphonamide (150 mg, 79%).
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