Pyridyl Radical Cation for C−H Amination of Arenes

Electron‐transfer photocatalysis provides access to the elusive and unprecedented N ‐pyridyl radical cation from selected N‐substituted pyridinium reagents. The resulting C(sp 2 )−H functionalization of (hetero)arenes furnishes versatile intermediates for the development of valuable aminated aryl scaffolds. Mechanistic studies that include the first spectroscopic evidence of a spin‐trapped N ‐pyridyl radical adduct implicate SET‐triggered, pseudo‐mesolytic cleavage of the N−X pyridinium reagents mediated by visible light.