Photoredox Product Selectivity Controlled by Persistent Radical Stability
Photoredox Product Selectivity Controlled by Persistent Radical Stability
复制标题
光氧化还原产物的选择性由持久的自由基稳定性控制
DOI：
10.1021/acs.joc.3c00490
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
Swierk, John R.
中科院分区：
文献类型：
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作者：
Stevenson, Bernard G.;Gironda, Cameron;Talbott, Eric;Prascsak, Amanda;Burnett, Nora L.;Kompanijec, Victoria;Nakhamiyayev, Roman;Fredin, Lisa A.;Swierk, John R.
光氧化还原催化用于小有机分子的合成依赖于利用和转换可见光中的能量来驱动反应。具体来说，光子能量被用来产生自由基，这些自由基可以通过随后的反应步骤来形成所需的产物。氰芳烃由于其作为持久性自由基阴离子的稳定性，在光氧化还原催化中被广泛用作芳化剂。然而，当使用不同的氰芳烃时，产品收率有明显的、无法解释的差异。在本研究中，表征了五种氰芳烃偶联伙伴与n -苯基吡咯烷之间α-氨基芳基化光氧化还原反应的量子产率和产物产率。氰芳烃消耗和产物产率的显著差异表明，反应的化学不可逆、非生产性途径。对反应副产物的分析表明，产物的形成与自由基阴离子的断裂一致。采用电化学和计算方法研究了不同氰基芳烃的裂解过程，揭示了产物收率与氰基芳烃自由基阴离子稳定性之间的关系。动力学模拟表明，n -苯基吡咯烷与氰芳烃的交叉偶联选择性受持续自由基效应的控制。
The use of photoredox catalysis for the synthesis of small organic molecules relies on harnessing and converting the energy in visible light to drive reactions. Specifically, photon energy is used to generate radical ion species that can be harnessed through subsequent reaction steps to form a desired product. Cyanoarenes are widely used as arylating agents in photoredox catalysis because of their stability as persistent radical anions. However, there are marked, unexplained variations in product yields when using different cyanoarenes. In this study, the quantum yield and product yield of an α-aminoarylation photoredox reaction between five cyanoarene coupling partners andN-phenylpyrrolidine were characterized. Significant discrepancies in cyanoarene consumption and product yield suggested a chemically irreversible, unproductive pathway in the reaction. Analysis of the side products in the reaction demonstrated the formation of species consistent with radical anion fragmentation. Electrochemical and computational methods were used to study the fragmentation of the different cyanoarenes and revealed a correlation between product yield and cyanoarene radical anion stability. Kinetic modeling of the reaction demonstrates that cross-coupling selectivity betweenN-phenylpyrrolidine and the cyanoarene is controlled by the same phenomenon present in the persistent radical effect.