Send to

Choose Destination
J Org Chem. 1999 Jul 23;64(15):5388-5395.

Photoinduced C-F Bond Cleavage in Some Fluorinated 7-Amino-4-quinolone-3-carboxylic Acids.

Author information

Department Organic Chemistry, University of Pavia, v. le Taramelli 10, 27100 Pavia, Italy, and CNR Inst. Photochemistry, v. Gobetti 101, 40129 Bologna, Italy.


The photochemistry of some fluorinated 7-amino-4-quinolone-3-carboxylic acids used in therapy as antibacterials and known to be phototoxic has been investigated in water. All of them undergo heterolytic defluorination, and this appears to be a path for the generation of aryl cations in solution. 6-Fluoro derivatives such as norfloxacin (Phi(dec) = 0.06) and enoxacin (Phi(dec) = 0.13) give the corresponding phenols. Insertion of an electron-donating substituent makes defluorination inefficient; thus, ofloxacin, an 8-alkoxy derivative, is found to be rather photostable (Phi(dec) = 0.001) and reacts in part via a process different from defluorination (degradation of the N-alkyl side chain). With a 6,8-difluoro derivative, lomefloxacin, the reaction is more efficient (Phi = 0.55) and selective for position 8. Contrary to the previous cases, the aryl cation undergoes insertion in the neighboring N-ethyl group rather than solvent addition (a carbene-like chemistry). With all of the above fluoroquinolones an intensive triplet-triplet absorption is detected and is quenched by sulfite (k(q) = (1-5) x 10(8) M(-)(1) s(-)(1)). Under this condition, reductive defluorination via the radical anion takes place. The relation of the above chemistry to the phototoxicity of these drugs is commented upon briefly.


Supplemental Content

Full text links

Icon for American Chemical Society
Loading ...
Support Center