Dimethylformamide → 6,7-Dichloro-2,3-dimethoxy-5-(N-methylcarbamoyl)quinoxaline

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Reaction Steps

To a solution of 6,7-dichloro-2,3-dimethoxyquinoxaline-5-carboxylic acid (Preparation 6, 0.890 g, 2.93 mmol) in dichloromethane (25 mL) at room temperature under nitrogen was added dry N,N-dimethylformamide (50 μL, 47.2 mg, 0.64 mmol) followed by oxalyl chloride (0.338 mL, 3.8 mmol). After 0.5 hours, the mixture was concentrated under reduced pressure. Dichloromethane (10 mL) was added to the residue at room temperature under nitrogen, followed by methylamine (33% w/w solution in ethanol, 10 mL, 80.3 mol). After 10 minutes, the mixture was evaporated under reduced pressure and the residue was partitioned between dichloromethane (20 mL) and 1M aqueous hydrochloric acid solution. The organic extract was dried (MgSO4) and evaporated under reduced pressure. The residue was purified by flash chromatography on silica gel, by gradient elution using dichloromethane:methanol (100:0 changing to 99:1, by volume) as the eluent to give a solid which was recrystallised from toluene to afford the title compound (0.570 g, 61%) as a white solid.

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