Mechanistic Investigations of an ?-Aminoarylation Photoredox Reaction

While photoredox catalysis continues to transform modern synthetic chemistry, detailed mechanistic studies involving direct observation of reaction intermediates and rate constants are rare. By use a combination steady state photochemical measurements, transient laser spectroscopy, electrochemical methods, an ?-aminoarylation mechanism that is the inspiration for large number reactions was rigorously characterized. Despite high product yields, external quantum yield (QY) remained low (15-30%). absorption productive unproductive pathways were identified assigned develop comprehensive picture reaction. The role cyanoarene, 1,4-dicyanobenzne, found be unexpectedly complex, functioning both as initial proton acceptor in neutral stabilizer 1,4-dicyanobenzene radical anion. Finally, kinetic modeling utilized analyze at unprecedented level understanding. This demonstrated limited not by kinetics individual steps but instead scattering losses parasitic photochemically inactive donor-acceptor complex.