Photogeneration of Chlorine Radical from a Self‐Assembled Fluorous 4CzIPN•Chloride Complex: Application in C−H Bond Functionalization

The chlorine radical is a strong HAT (Hydrogen Atom Transfer) agent that is very useful for the functionalization of C(sp3)−H bonds. Albeit highly attractive, its generation from the poorly oxidizable chloride ion mediated by an excited photoredox catalyst is a difficult task. We now report that 8Rf8‐4CzIPN, an electron‐deficient fluorous derivative of the benchmark 4CzIPN photoredox catalyst belonging to the donor‐acceptor carbazole‐cyanoarene family, is not only a better photooxidant than 4CzIPN, but also becomes an excellent host for the chloride ion. Combining these two properties ultimately makes the self‐assembled 8Rf8‐4CzIPN•Cl− dual catalyst highly reactive in redox‐neutral Giese‐type C(sp3)−H bond alkylation reactions promoted by the chlorine radical. Additionally, because of its fluorous character, the efficient separation/recovery of 8Rf8‐4CzIPN could be envisioned. The fluorous photoredox catalyst 8Rf8‐4CzIPN (Rf8=C8F17) forms a supramolecular complex with chloride ions with high affinity. Integrating fluorous chains on the parent dye greatly enhances both the ion‐binding affinity, as well as the oxidizing ability of the catalyst. Efficient photooxidation of the chloride was observed, generating the chlorine HAT reagent, which was tested in the redox‐neutral Giese‐type C(sp3)−H bond alkylation reaction.