A Dichotomy in Cross-Coupling Site Selectivity in a Dihalogenated Heteroarene: Influence of Mononuclear Pd, Pd Clusters, and Pd Nanoparticles-the Case for Exploiting Pd Catalyst Speciation.
A Dichotomy in Cross-Coupling Site Selectivity in a Dihalogenated Heteroarene: Influence of Mononuclear Pd, Pd Clusters, and Pd Nanoparticles-the Case for Exploiting Pd Catalyst Speciation.
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DOI：
10.1021/jacs.1c05294
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发表时间：
2021-06-30
影响因子：
15
通讯作者：
Fairlamb IJS
中科院分区：
文献类型：
--
作者：
Scott NWJ;Ford MJ;Jeddi N;Eyles A;Simon L;Whitwood AC;Tanner T;Willans CE;Fairlamb IJS
位点选择性二卤代杂芳烃与有机金属试剂的交叉偶联通常发生在靠近杂原子的卤素上，这是由于固有的相对亲电性，特别是在强极化体系中。一个典型的例子是2,4-二溴吡啶与有机硼的Suzuki-Miyaura交叉偶联（SMCC），该偶联通常使用单核Pd（预）催化剂表现出c2 -芳基化位点选择性。考虑到Pd的形成，特别是聚集，已知会导致催化能力强的多核Pdn的形成，这些物种对交叉偶联位点选择性的影响在很大程度上仍然未知。本研究发现，在与有机硼酸（SMCC）和格氏试剂（kumada）的2,4-二溴吡啶交叉偶联反应中，多核钯以pd3型簇和纳米粒子的形式，将芳基化位点选择性从C2切换到C4。Pd/配体的比例和合适的稳定盐的存在对改变位点选择性至关重要。更广泛地说，本研究提供了实验证据，证明聚合的钯催化剂不仅具有催化能力，而且通过改变产物的选择性来改变反应结果。
Site-selective dihalogenated heteroarene cross-coupling with organometallic reagents usually occurs at the halogen proximal to the heteroatom, enabled by intrinsic relative electrophilicity, particularly in strongly polarized systems. An archetypical example is the Suzuki–Miyaura cross-coupling (SMCC) of 2,4-dibromopyridine with organoboron species, which typically exhibit C2-arylation site-selectivity using mononuclear Pd (pre)catalysts. Given that Pd speciation, particularly aggregation, is known to lead to the formation of catalytically competent multinuclear Pdn species, the influence of these species on cross-coupling site-selectivity remains largely unknown. Herein, we disclose that multinuclear Pd species, in the form of Pd3-type clusters and nanoparticles, switch arylation site-selectivity from C2 to C4, in 2,4-dibromopyridine cross-couplings with both organoboronic acids (SMCC reactions) and Grignard reagents (Kumada-type reactions). The Pd/ligand ratio and the presence of suitable stabilizing salts were found to be critically important in switching the site-selectivity. More generally, this study provides experimental evidence that aggregated Pd catalyst species not only are catalytically competent but also alter reaction outcomes through changes in product selectivity.
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影响因子：
15
作者：
Golding, William A.;Schmitt, Hendrik L.;Phipps, Robert J.
通讯作者：
Phipps, Robert J.
影响因子：
15
作者：
Cassol, CC;Umpierre, AP;Dupont, J
通讯作者：
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影响因子：
4.3
作者：
Amatore, Christian;Jutand, Anny;Le Duc, Gaetan
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Le Duc, Gaetan
影响因子：
16.6
作者：
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通讯作者：
Schoenebeck, Franziska
影响因子：
3.3
作者：
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通讯作者：
Chechik, Victor