Concise route to the key intermediate for divergent synthesis of C7-substituted fluoroquinolone derivatives

A concise route to ethyl 7-bromo-1-cyclopropyl-6,8-difluoro-4-quinolone-3-carboxylate has been developed. This compound is a key intermediate for divergent synthesis of various C7-substituted fluoroquinolones, a group of potent topoisomerase II inhibitors with promising clinical applications.