Mechanistic Investigations of an α-Aminoarylation Photoredox Reaction
| Autor: | Victor Wambua, Emily A. Loiaconi, Ethan H. Spielvogel, John R. Swierk, Roman V. Nakhamiyayev, Bernard G. Stevenson |
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| Rok vydání: | 2021 |
| Předmět: |
Chemistry
Radical Kinetics Photoredox catalysis Quantum yield General Chemistry Reaction intermediate 010402 general chemistry Photochemistry 01 natural sciences Biochemistry Catalysis 0104 chemical sciences Colloid and Surface Chemistry Reaction rate constant Ultrafast laser spectroscopy Steady state (chemistry) |
| Zdroj: | Journal of the American Chemical Society. 143:8878-8885 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/jacs.1c03693 |
| Popis: | 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 of a combination of steady state photochemical measurements, transient laser spectroscopy, and electrochemical methods, an α-aminoarylation mechanism that is the inspiration for a large number of photoredox reactions was rigorously characterized. Despite high product yields, the external quantum yield (QY) of the reaction remained low (15-30%). By use of transient absorption spectroscopy, productive and unproductive reaction pathways were identified and rate constants assigned to develop a comprehensive mechanistic picture of the reaction. The role of the cyanoarene, 1,4-dicyanobenzne, was found to be unexpectedly complex, functioning both as initial proton acceptor in the reaction and as a neutral stabilizer for the 1,4-dicyanobenzene radical anion. Finally, kinetic modeling was utilized to analyze the reaction at an unprecedented level of understanding. This modeling demonstrated that the reaction is limited not by the kinetics of the individual steps but instead by scattering losses and parasitic absorption by a photochemically inactive donor-acceptor complex. |
| Databáze: | OpenAIRE |
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