6,?7-?Dichloro-?1,?4-?dihydro-?4-?oxo-?3-?quinolinecarboxylic Acid Ethyl Ester is an intermediate in synthesizing 6-Chloro-6-defluoro Ciprofloxacin (C368035). It is an impurity of Ciprofloxacin (C482500), which is a fluorinated quinolone antibacterial.