Nickel-catalyzed cross-coupling of photoredox-generated radicals: uncovering a general manifold for stereoconvergence in nickel-catalyzed cross-couplings.
Nickel-catalyzed cross-coupling of photoredox-generated radicals: uncovering a general manifold for stereoconvergence in nickel-catalyzed cross-couplings.
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DOI：
10.1021/ja513079r
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发表时间：
2015-04-22
影响因子：
15
通讯作者：
Kozlowski MC
中科院分区：
文献类型：
--
作者：
Gutierrez O;Tellis JC;Primer DN;Molander GA;Kozlowski MC
SP3杂化有机硼试剂通过光氧化还原/镍双重催化交叉偶联，代表了过渡金属催化过程中使用烷基金属试剂的新的反应性范例。本文用密度泛函理论对这一重要转变的机理细节进行了研究。计算揭示了一种新的反应途径，该反应途径涉及烷基镍(I)络合物，它是由烷基自由基加成到Ni(0)上而产生的，很可能与先前提出的机理同时进行。对转化的对映选择性变体的分析揭示了一种意想不到的立体诱导流形，涉及Ni(III)中间体的动态动力学拆分(DKR)，其中立体决定步骤是还原消除。此外，计算表明，基于DKR的立体诱导流形可能是在许多其他立体收敛的镍催化的交叉偶联和还原偶联中观察到的立体选择性的原因。
The cross-coupling of sp3-hybridized organoboron reagents via photoredox/nickel dual catalysis represents a new paradigm of reactivity for engaging alkylmetallic reagents in transition-metal-catalyzed processes. Reported here is an investigation into the mechanistic details of this important transformation using density functional theory. Calculations bring to light a new reaction pathway involving an alkylnickel(I) complex generated by addition of an alkyl radical to Ni(0) that is likely to operate simultaneously with the previously proposed mechanism. Analysis of the enantioselective variant of the transformation reveals an unexpected manifold for stereoinduction involving dynamic kinetic resolution (DKR) of a Ni(III) intermediate wherein the stereodetermining step is reductive elimination. Furthermore, calculations suggest that the DKR-based stereoinduction manifold may be responsible for stereoselectivity observed in numerous other stereoconvergent Ni-catalyzed cross-couplings and reductive couplings.