Pentane → 1-Cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic Acid Ethyl Ester

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Reaction Steps

To 2.0 g (6.0 mmol) of the 2-(2,3,4,5-tetrafluorobenzoyl)-3-cyclopropylaminoacrylic acid, ethyl ester in 60 ml of dry dioxane was added 0.29 g of sodium hydride 50% dispersion) that was prewashed with pentane. The sodium hydride was delivered in 10 ml of dry tetrahydrofuran at 0° C. When evolution of hydrogen began to slow, the mixture was refluxed for two hours. It was concentrated, and the residue taken up in dichloromethane, which was water extracted, dried (MgSO4), and concentrated. The residue was purified by column chromatography (silica gel 70-200 mesh, using chloroform:hexane:isopropanol, 4:5:1) to give 0.95 g of the 1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid, ethyl ester, mp 168-169° C. This material was dissolved in acetic acid at 100° C. and was treated with 10 ml of 0.5N hydrochloric acid for 2.5 hours. The mixture was cooled and water added. The solids were then collected to give 0.7 g of 1-cyclopropyl-1,4-dihydro-4-oxo-6,7,8-trifluoro-3-quinolinecarboxylic acid, mp 226-228° C.

Provenance & Evidence