Photoredox-Catalyzed Synthesis of Alkylaryldiazenes: Formal Deformylative C-N Bond Formation with Alkyl Radicals.

Diazenes are valuable compounds that have found broad applicability because of their optical and biological properties. We report the synthesis of alkylaryldiazenes via formal, photoredox-catalyzed, deformylative C-N bond formation. The procedure employs dihydropyridines for the generation of alkyl radicals, which are then trapped by diazonium salts and reduced to the corresponding diazenes. Control experiments were performed to confirm the involvement of radicals in the mechanism. The reaction can be carried out at room temperature and employs readily available reagents; the mild conditions allowed the use of highly functionalized substrates. There was no observed tautomerization of the diazenes to the corresponding arylhydrazones.