A Fluorine 1,2-Migration via Aryl Cation/Radical/Radical Anion/Radical Sequence

Irradiation of a 7-piperazino-8-fluoroquinolone causes formal 1,2-fluorine migration, piperazine loss and reduction, or nucleophile addition in 8. Product study, laser flash photolysis, and computational modeling support F– detachment to yield a triplet 8-quinolyl cation that either inserts intramolecularly or is trapped by Cl–, Br–. However, iodide and pyrrole reduce it to the radical that continues the ‘redox tour’ (aryl cation→ radical→ radical anion→ radical and then again radical or radical anion) leading to the rearranged products.