Differences in the Performance of Allyl Based Palladium Precatalysts for Suzuki-Miyaura Reactions.
Differences in the Performance of Allyl Based Palladium Precatalysts for Suzuki-Miyaura Reactions.
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DOI：
10.26434/chemrxiv.12573608
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发表时间：
2020-06
影响因子：
5.4
通讯作者：
Matthew R. Espinosa;A. Doppiu;N. Hazari
中科院分区：
文献类型：
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作者：
Matthew R. Espinosa;A. Doppiu;N. Hazari
钯(II)预催化剂因其稳定性好、活性高而被广泛用于促进交叉偶联反应。因此，Buchwald的Palladacycle、Organ的Peppsi物种、Nolan的基于烯丙基的络合物和耶鲁的含有1-叔丁基的络合物等前催化剂都可以在商业上获得。比较不同类别的预催化剂的性能是具有挑战性的，因为它们通常在不同的条件下使用，部分原因是它们通过不同的途径被还原为活性物种。然而，在特定类别的预催化剂中，比较性能更容易，因为它们通过相似的途径激活，并且在相同的条件下使用。在此，我们考察了不同的烯丙基预催化剂，如(η3-烯丙基)PdCl(L)、(η3-巴豆基)PdCl(L)、(η3-肉桂基)PdCl(L)和(η3-1-叔丁基)PdCl(L)在铃木-宫浦反应中的活性。具体地说，我们评估前催化剂的性能作为辅助配体(NHC或膦)，反应条件和底物是不同的。在某些情况下，我们将相对活性与激活机制和非活性钯(I)二聚体形成的普遍程度联系起来。此外，我们还比较了原位生成的预催化剂与常用的钯源，如三(二亚甲基丙酮)二钯(0)(Pd2dBa3)，双(乙腈)二氯钯(II)(Pd(CH3CN)2Cl2)和醋酸钯的性能。我们的结果提供了在不同条件下使用哪种预催化剂的信息。
Palladium(II) precatalysts are used extensively to facilitate cross-coupling reactions because they are bench stable and give high activity. As a result, precatalysts such as Buchwald's palladacycles, Organ's PEPPSI species, Nolan's allyl-based complexes, and Yale's 1-tert-butylindenyl containing complexes, are all commercially available. Comparing the performance of the different classes of precatalysts is challenging because they are typically used under different conditions, in part because they are reduced to the active species via different pathways. However, within a particular class of precatalyst, it is easier to compare performance because they activate via similar pathways and are used under the same conditions. Here, we evaluate the activity of different allyl-based precatalysts, such as (η3-allyl)PdCl(L), (η3-crotyl)PdCl(L), (η3-cinnamyl)PdCl(L), and (η3-1-tert-butylindenyl)PdCl(L) in Suzuki-Miyaura reactions. Specifically, we evaluate precatalyst performance as the ancillary ligand (NHC or phosphine), reaction conditions, and substrates are varied. In some cases, we connect relative activity to both the mechanism of activation and the prevalence of the formation of inactive palladium(I) dimers. Additionally, we compare the performance of in situ generated precatalysts with commonly used palladium sources such as tris(dibenzylideneacetone)dipalladium(0) (Pd2dba3), bis(acetonitrile)dichloropalladium(II) (Pd(CH3CN)2Cl2), and palladium acetate. Our results provide information about which precatalyst to use under different conditions.