Iodoethane → Ethyl 4-ethyl-6-fluoro-3,4-dihydro-3-oxo-2-quinoxalinecarboxylate

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The mixture of 6-fluoro-3,4-dihydro-3-oxo-2-quinoxalinecarboxylic acid, ethyl ester and 7-fluoro-3,4-dihydro-3-oxo-2-quinoxalinecarboxylic acid, ethyl ester (Example 22a) (2 g), ethyl iodide (4 g) and anhydrous potassium carbonate (5.9 g) in 2-butanone (200 ml) were heated under reflux for 5 hours. The mixture was filtered and the filtrate was evaporated. The residual oil was chromatographed on silica using a mixture of petroleum ether (b.p. 60°-80°) and ethyl acetate (3:1) as eluent to give the required product, on evaporation of the later fractions, m.p. 99°-101.5°, (50%).

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