Orthogonal Nanoparticle Catalysis with Organogermanes
Orthogonal Nanoparticle Catalysis with Organogermanes
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DOI：
10.1002/anie.201910060
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发表时间：
2019-10-23
影响因子：
16.6
通讯作者：
Schoenebeck, Franziska
中科院分区：
文献类型：
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作者：
Fricke, Christoph;Sherborne, Grant J.;Schoenebeck, Franziska
虽然纳米颗粒被广泛用作催化剂，但与均相分子或本体多相催化剂相比，对其引发特权转化的潜在能力知之甚少。我们在此证明（和合理化），纳米粒子显示正交反应的分子催化剂的芳基卤化物与芳基锗烷的交叉偶联。虽然芳基锗烷在LnPd 0/LnPdII催化中是不反应的，并且允许在它们存在下建立的偶联配偶体的选择性官能化，但是它们在Pd纳米颗粒条件下显示出上级反应性，胜过建立的偶联配偶体（例如ArBPin和ArBMIDA），并且允许空气耐受、无碱和正交接近有价值的和具有挑战性的联芳基基序。与众所周知的不稳定的多氟芳基硼酸和2-吡啶基硼酸相反，相应的锗烷是高度稳定的，并且容易偶联。我们的机制和计算研究提供了明确的支持纳米粒子催化，并建议，由于芳基锗烷的电子丰富，他们优先亲电芳香取代反应，反过来又优先激活更亲电的纳米粒子。
Although nanoparticles are widely used as catalysts, little is known about their potential ability to trigger privileged transformations as compared to homogeneous molecular or bulk heterogeneous catalysts. We herein demonstrate (and rationalize) that nanoparticles display orthogonal reactivity to molecular catalysts in the cross-coupling of aryl halides with aryl germanes. While the aryl germanes are unreactive in LnPd0/LnPdII catalysis and allow selective functionalization of established coupling partners in their presence, they display superior reactivity under Pd nanoparticle conditions, outcompeting established coupling partners (such as ArBPin and ArBMIDA) and allowing air-tolerant, base-free, and orthogonal access to valuable and challenging biaryl motifs. As opposed to the notoriously unstable polyfluoroaryl- and 2-pyridylboronic acids, the corresponding germanes are highly stable and readily coupled. Our mechanistic and computational studies provide unambiguous support of nanoparticle catalysis and suggest that owing to the electron richness of aryl germanes, they preferentially react by electrophilic aromatic substitution, and in turn are preferentially activated by the more electrophilic nanoparticles.