Metal-Free, Redox-Neutral, Site-Selective Access to Heteroarylamine via Direct Radical–Radical Cross-Coupling Powered by Visible Light Photocatalysis

Transition-metal-catalyzed C–N
bond-forming reactions have
emerged as fundamental and powerful tools to construct arylamines,
a common structure found in drug agents, natural products, and fine
chemicals. Reported herein is an alternative access to heteroarylamine
via radical–radical cross-coupling pathway, powered by visible
light catalysis without any aid of external oxidant and reductant.
Only by visible light irradiation of a photocatalyst, such as a metal-free
photocatalyst, does the cascade single-electron transfer event for
amines and heteroaryl nitriles occur, demonstrated by steady-state
and transient spectroscopic studies, resulting in an amine radical
cation and aryl radical anion in situ for C–N bond formation.
The metal-free and redox economic nature, high efficiency, and site-selectivity
of C–N cross-coupling of a range of available amines, hydroxylamines,
and hydrazines with heteroaryl nitriles make this protocol promising
in both academic and industrial settings.