Pyridyl Radical Cation for C−H Amination of Arenes

The road less travelled: Select pyridinium reagents undergo an unprecedented heterolytic fragmentation upon single electron reduction to afford a synthetically viable N‐pyridyl radical cation. This reactive species was leveraged for the C−H amination of (hetero)arenes to furnish N‐aryl pyridinium products, which enable access to diverse nitrogen scaffolds.

Abstract

Electron‐transfer photocatalysis provides access to the elusive and unprecedented N‐pyridyl radical cation from selected N‐substituted pyridinium reagents. The resulting C(sp²)−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.

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