Hydrochloric Acid → 7-Fluoro-8-(1-piperazinyl)-5-oxo-1,2-dihydro-5H-thiazolo(3,2-a)quinoline-4-carboxylic acid

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Reaction Steps

To one gram of 8-chloro-7-fluoro-5-oxo-1,2-dihydro-5H-thiazolo(3,2-a)quinoline-4-carboxylic acid (33 mmol) were added 2.87 grams (33 mmol) of anhydrous piperazine and 30 ml of pyridine and the resulting suspension was heated to reflux for twelve hours in an oil bath. Pyridine was evaporated therefrom under reduced pressure, water was added to the residue, and the mixture was again concentrated under reduced pressure. Water was added to the resulting residue, then 4 ml of 2 N aqueous solution of sodium hydroxide was added thereto, and the mixture was warmed to prepared uniform solution. Then this was adjusted to pH nearly seven with 1 N hydrochloric acid. Crystals separated out therefrom were collected by filtration, washed with water, washed with acetone and ether, and air dried to give the title product as powdery crystals. Yield 997.8 mg (90.7 percent). Melting point 287° to 288° C. (decomposition). Elementary analysis calculated as C16H16FN3O3S.3H2O: C 47.64, H 5.50, N 10.41; Found: C 47.60, H 5.42, N 10.63.

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