[Pd(NHC)(μ-Cl)Cl]2: Versatile and Highly Reactive Complexes for Cross-Coupling Reactions that Avoid Formation of Inactive Pd(I) Off-Cycle Products
[Pd(NHC)(μ-Cl)Cl]2: Versatile and Highly Reactive Complexes for Cross-Coupling Reactions that Avoid Formation of Inactive Pd(I) Off-Cycle Products
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DOI：
10.1016/j.isci.2020.101377
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发表时间：
2020-08-21
期刊：
影响因子：
5.8
通讯作者：
Szostak, Michal
中科院分区：
文献类型：
--
作者：
Zhou, Tongliang;Ma, Siyue;Szostak, Michal
开发更具反应性、通用性、易于获得和易于获得的Pd（II）-NHC预催化剂仍然是均相催化中的关键挑战。在这项研究中，我们建立了空气稳定的NHC-Pd（II）氯二聚体，[Pd（NHC）（mu-Cl）Cl]（2），作为迄今为止开发的最具反应性的Pd（II）-NHC催化剂。最关键的是，与[Pd（NHC）（allyl）Cl]配合物相比，用氯化物取代烯丙基丢弃配体允许更容易的活化步骤，同时有效地防止形成关闭循环[Pd-2（mu-allyl）（mu-Cl）（NHC）（2）]产物。通过与酰胺交叉偶联、Suzuki交叉偶联以及药物的直接后期官能化的广泛相容性证明了该实用性。计算研究为NHC-Pd（II）氯二聚体活化途径提供了关键的见解。报道了一种由NHC盐一锅法合成NHC-Pd（II）氯代二聚体的简便方法。考虑到Pd催化的交叉偶联反应的巨大效用和[Pd（NHC）（烯丙基）Cl]预催化剂的压倒性成功，我们认为NHC-Pd（II）氯代二聚物[Pd（NHC）（mu-Cl）Cl]（2）应被视为交叉偶联过程中的首选预催化剂。
The development of more reactive, general, easily accessible, and readily avail-able Pd(II)-NHC precatalysts remains a key challenge in homogeneous catalysis. In this study, we establish air-stable NHC-Pd(II) chloro-dimers, [Pd(NHC)(mu-Cl) Cl](2), as the most reactive Pd(II)-NHC catalysts developed to date. Most crucially, compared with [Pd(NHC)(allyl)Cl] complexes, replacement of the allyl throw-away ligand with chloride allows for a more facile activation step, while effec-tively preventing the formation of off-cycle [Pd-2(mu-allyl)(mu-Cl)(NHC)(2)] products. The utility is demonstrated via broad compatibility with amide cross-coupling, Suzuki cross-coupling, and the direct, late-stage functionalization of pharmaceu-ticals. Computational studies provide key insight into the NHC-Pd(II) chloro-dimer activation pathway. A facile synthesis of NHC-Pd(II) chloro-dimers in one-pot from NHC salts is reported. Considering the tremendous utility of Pd-catalyzed cross-coupling reactions and the overwhelming success of [Pd(NHC)(allyl)Cl] precatalysts, we believe that NHC-Pd(II) chloro-dimers, [Pd(NHC)(mu-Cl)Cl](2), should be considered as go-to precatalysts of choice in cross-coupling processes.