Photochemistry of some non zwitterionic fluoroquinolones

Two non zwitterionic analogues of fluoroquinolone drugs, viz. 1-ethyl-7-piperidino-8-fluoroquinol-4-
one-3-carboxylic acid and 1-ethyl-7-piperidino-6,8-difluoroquinol-4-one-3-carboxylic acids have been
synthesized and their photochemistry has been investigated. Both compound undergo photoheterolysis
of the C8 F bond generating a triplet cation that either inserts into the 1-alkyl chain or is trapped or
reduced by external nucleophiles. The reaction is analogous to that observed with the corresponding
(zwitterionic) 7-piperazino derivatives, but the quantum yield is ca five times lower. This supports the
rationalization that in the latter case assistance to defluorination by the N+ H bond has a determining
role.