Novel synthesis of arylfluoroquinolone antimicrobial agents

A new synthetic method for preparing two arylfluoroquinolone antimicrobial agents, difloxacin and temafloxacin, was reported. 2,4-Dichloro-5-fluoroacetophenone was used as a starting material to react with diethyl oxalate in place of diethyl carbonate giving the corresponding beta-keto ester in high yield. The beta-keto ester was allowed to ethyloxymethenylation, amination, cyclization and hydrolysis to afford an intermediate acid with one more carbonyl compared with that reported in the literature. After decarbonylation, it reacted with piperazine derivatives to yield the desired antibiotics. All new compounds were confirmed by H-1 NMR, IR, MS spectra and elemental analysis.