A new short and efficient strategy for the synthesis of quinolone antibiotics

A simple protocol for the synthesis of quinolone antibiotics is exemplified for the synthesis of norfloxacin; 3-chloro-4-fluoroaniline with triethyl orthoformate is transformed into its N-ethyl-N-formyl derivative which reacts with methyl malonyl morpholide and phosphoryl chloride at 100 °C to give 6-fluoro-7-chloro-1-ethylquinol-4-one-3-carboxylic acid, which has previously been converted into norfloxacin by the action of piperazine.