A PRACTICAL ROUTE TO C-8 SUBSTITUTED FLUOROQUINOLONES

The ortho metalation of N-(tert-butoxycarbonyl)-3,4-difluoroaniline, with t-BuLi at -78-degrees-C in THF occured regioselectively at C-2 position. The resulting lithiated species reacted with a variety of electrophiles to give 2-substituted-3,4-difluoroanilines in good yields after hydrolysis. These compounds have been readily transformed into C-8 substituted fluoroquinolones. The nucleophilic substitution at C-7 by piperazines and the alkylation at N-1 on these quinolones have also been performed.