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 and N-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 between N-phenylpyrrolidine and the cyanoarene is controlled by the same phenomenon present in the persistent radical effect.

中文翻译：

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光氧化还原产物的选择性由持久的自由基稳定性控制

使用光氧化还原催化合成小有机分子依赖于利用和转换可见光中的能量来驱动反应。具体来说，光子能用于产生自由基离子物质，可以通过后续反应步骤利用自由基离子物质形成所需的产物。氰基芳烃因其作为持久自由基阴离子的稳定性而被广泛用作光氧化还原催化中的芳基化剂。然而，当使用不同的氰基芳烃时，产物收率存在明显的、无法解释的变化。在本研究中，表征了五种氰基芳烃偶联伙伴与N-苯基吡咯烷之间的 α-氨基芳基化光氧化还原反应的量子产率和产物产率。氰芳烃消耗量和产物收率的显着差异表明反应中存在化学不可逆、无生产力的途径。对反应中副产物的分析证明了与自由基阴离子断裂一致的物质的形成。使用电化学和计算方法研究了不同氰基芳烃的裂解，并揭示了产物产率和氰基芳烃自由基阴离子稳定性之间的相关性。反应的动力学模型表明， N-苯基吡咯烷和氰基芳烃之间的交叉偶联选择性受到持久自由基效应中存在的相同现象的控制。