Ethanol → 8-chloro-7-fluoro-5-oxo-1,2-dihydro-5H-thiazolo(3,2-a)quinoline-4-carboxylic acid

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Reaction Steps

Six hundred mg (1.83 mmol) of ethyl 8-chloro-7-fluoro-5-oxo-1,2-dihydro-5H-thiazolo(3,2-a)-quinoline-4-carboxylate obtained in Example 15 was added to a mixed solvent of ethanol and water (1:1), then 2 ml of 2 N aqueous solution of sodium hydroxide was added thereto, and the mixture was heated to reflux for two hours. When the reaction was completed, ethanol was evaporated therefrom, the residual aqueous solution was adjusted to pH nearly 7.0 with 1 N aqueous solution of acetic acid and, after stirring for a while, crystals separated out therefrom were collected by filtration, successively washed with ethanol, acetone and ether and air dried to give 501 mg (91.4 percent) of the title compound, melting point 318° C. (decomposition). Elementary analysis calculated as C12H7FClNO3S: C 48.09, H 2.35, N. 4.67; Found: C 48.28, H 2.14, N 4.37.

Provenance & Evidence