Sulfuric Acid → Ethyl 3-(2,7-dichloro-6-fluoro-3-quinolyl)-3-oxopropionate

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Reaction Conditions

Reaction Steps

A suspension of 2,7-dichloro-6-fluoro-3-quinolinecarboxylic acid (38.75 g) in trichloromethane (410 cc) and thionyl chloride (24 cc) is heated to a temperature in the region of 60° C. with stirring for 6 hours. The solution obtained is concentrated to dryness under reduced pressure (20 kPa) at 50° C. The dry extract is taken up twice with toluene (200 cc in total) and concentrated again under reduced pressure under the same conditions as above. The yellow solid obtained (m.p. 124° C.), is dissolved in anhydrous tetrahydrofuran (230 cc). The solution obtained is introduced dropwise, with stirring, in the course of 30 minutes and at between 5° and 10° C. into a solution (200 cc) of magnesium chelate in tetrahydrofuran. The temperature is allowed to rise to 20° C. and the mixture is stirred for 1 and a half hours at this temperature. The solution obtained is introduced dropwise, with stirring and at a temperature in the region of 5° C. into 0.5 N sulphuric acid (1 liter). The temperature of the suspension obtained is allowed to rise to 20° C. and the mixture is stirred for a further 2 hours at this temperature. The product is extracted with ethyl acetate (1 liter), the organic and aqueous phases are filtered through diatomaceous silica for filtration which enables some slight insoluble matter to be removed and the aqueous phase is extracted twice more with ethyl acetate (500 cc). The combined organic extracts are washed with water (2×500 cc), dried over magnesium sulphate, filtered and concentrated to dryness under reduced pressure (20 kPa) at 40° C. The residue is taken up with isopropyl ether (100 cc) at 20° C., drained and washed with isopropyl ether (2×30 cc). Ethyl 3-(2,7-dichloro-6-fluoro-3-quinolyl)-3-oxopropionate (40.55 g) is obtained in the form of a beige solid, m.p. 112°-114° C. This product is used without further purification for the subsequent steps.

Provenance & Evidence