We report here a comprehensive computational analysis of the mechanisms of the photoredox-nickel-HAT (HAT: hydrogen atom transfer) catalyzed arylation and alkylation of α-amino Csp3-H bonds developed by MacMillan and coworkers. Different alternatives for the three catalytic cycles were tested to identify unambiguously the operative reaction mechanism. Our analysis indicated that the IrIII photoredox catalyst, upon irradiation with visible light, can be either reduced or oxidized by the HAT and nickel catalysts, respectively, indicating that both reductive and oxidative quenching catalytic cycles can be operative, although the reductive cycle is favored. Our analysis of the HAT cycle indicated that activation of a α-amino Csp3‒H bond of the substrate is facile and selective relative to activation of a β-amino Csp3‒H bond. Finally, our analysis of the nickel cycle indicated that both arylation and alkylation of α-amino Csp3-H bonds occurs via the sequence of nickel oxidation states NiI-NiII-NiI-NiIII, and of elementary steps: radical addition-SET-oxidative addition-reductive elimination.

中文翻译：

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对光氧化还原-镍-HAT 三重催化的 α-氨基 Csp3-H 键的芳基化和烷基化的机理洞察

我们在此报告了对由 MacMillan 及其同事开发的光氧化还原-镍-HAT（HAT：氢原子转移）催化的 α-氨基 Csp3-H 键的芳基化和烷基化机制的综合计算分析。测试了三个催化循环的不同替代方案，以明确确定操作反应机制。我们的分析表明，在可见光照射下，IrIII 光氧化还原催化剂可以分别被 HAT 和镍催化剂还原或氧化，这表明还原和氧化猝灭催化循环都可以进行，尽管还原循环是有利的。我们对 HAT 循环的分析表明，相对于 β-氨基 Csp3-H 键的激活，底物的 α-氨基 Csp3-H 键的激活是容易和选择性的。最后，