Acetic Anhydride → 3-Acetoxy-5,5-difluoro-6-oxo-5,6-dihydro-quinoline-4-carboxylic acid methyl ester

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Reaction Steps

A solution of 5,5-difluoro-3-hydroxy-6-oxo-5,6-dihydro-quinoline-4-carboxylic acid methyl ester (11.1 g, 43.50 mmol, 1.0 eq) in acetone (100 mL) is cooled to 0° C. before the addition of acetic anhydride (8.2 mL, 87.0 mmol, 2.0 eq). After 3 hours stirring at room temperature, solvent is evaporated and the crude product is purified by column chromatography (silica gel, eluent: petroleum ether:ethyl acetate, 5:1, v/v) to afford 3-acetoxy-5,5-difluoro-6-oxo-5,6-dihydro-quinoline-4-carboxylic acid methyl ester as a white solid (5.2 g, 40% yield).

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