Benzylic Fluorination of Aza‐Heterocycles Induced by Single‐Electron Transfer to Selectfluor

A selective and mild method for the benzylic fluorination of aromatic azaheterocycles with Selectfluor is described. These reactions take place by a previously unreported mechanism, in which electron transfer from the heterocyclic substrate to the electrophilic fluorinating agent Selectfluor eventually yields a benzylic radical, thus leading to the desired C−F bond formation. This mechanism enables high intra‐ and intermolecular selectivity for aza‐heterocycles over other benzylic components with similar C−H bond‐dissociation energies. An e‐transfer: Reported is a selective and mild method for the benzylic fluorination of aromatic aza‐heterocycles. These reactions take advantage of the oxidizing power of the electrophilic fluorinating agent Selectfluor. Either proton‐coupled electron‐transfer or single‐electron‐transfer followed by deprotonation yields a benzylic radical adjacent to the heterocycle, thus leading to selective C−F bond formation.