7-Chloro-1-ethyl-6-fluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic Acid (Norfloxacin EP Impurity A) is a Norfloxacin intermediate. Norfloxacin EP Impurity A; Norfloxacin USP Related Compound A (7-Chloro-1-ethyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic Acid).
Ethyl 7-chloro-1-ethyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylate (2.75 g, 9.24 mmol) was used as a raw material and dissolved in 60 mL of methanol. Subsequently, a 1:1 solution of hydrochloric acid (31.5 mL, 189 mmol) was added. The reaction mixture was heated to reflux for 2 h. Upon completion of the reaction, a white solid precipitated. The solid product was collected by filtration and washed with plenty of water. Finally, the product was dried in a vacuum oven for 2 h to afford 7-chloro-1-ethyl-6-fluoro-1,4-dihydro-4-carbonylquinoline-3-carboxylic acid (2.46 g, yield: 89.5%).
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