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首页> 外文期刊>Chemistry: A European journal >Catalytic Performance of Symmetrical and Unsymmetrical Sulfur-Containing Pincer Complexes: Synthesis and Tandem Catalytic Activity of the First PCSPincer Palladium Complex
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Catalytic Performance of Symmetrical and Unsymmetrical Sulfur-Containing Pincer Complexes: Synthesis and Tandem Catalytic Activity of the First PCSPincer Palladium Complex

机译：对称和不对称含硫夹钳配合物的催化性能：首个PCSPincer钯配合物的合成和串联催化活性

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摘要

The synthesis andcatalytic applications of a new aryl-basedunsymmetrical PCS-pincer complex are reported. Preparation of the robust airandmoisture-sta ble PCS-pincer palladium complex 5[X] startedfrom the symmetrical a,a-dibromo-meta-xylene andinvolvedthe selective substitution of one bromide by PPh2ACHTUNGTRENUNG(BH3), followedby substitution of the second bromide by SPh and subsequent introduction of the palladium. The new PCS complexes (5[X]) were employedas catalysts in two important organic transformations. Firstly, complex 5[Cl] displays high catalytic activity in aldol reactions but enters the catalytic cycle as a precatalyst. Secondly, complex 5- ACHTUNGTRENUNG[BF4] displays tandem catalytic activity in the coupling of allyl chlorides with aldehydes and imines in the presence of hexamethylditin. In these tandem catalytic reactions the first process s the conversion of allyl chlorides into trimethylallyltin (andtrime thyltin chloride) with Sn2Me6, which is followedby catalytic allylation of aldehyde and sulfonimine substrates. In addition, we present a new catalytic process for the one-pot allylation of 4-nitrobenzaldehyde with vinyloxirane. The catalytic performance of the novel PCS-pincer palladium complex was compared to those of its symmetrical PCP- andSCSpincer complex analogues. It was concluded that the unsymmetrical PCS complex advantageously unifies the attractive catalytic features of the corresponding symmetrical pincer complexes including both (p-) electronwithdrawing (such as phosphorus) or(s-) electron-donating (such as sulfur andnitrogen) heteroatoms. Thus, in the aldol reaction the PCS-pincer palladium complex 5[X] provides a high turnover frequency, while in the tandem process both reactions are catalysed with sufficiently high activity.
机译：报道了一种新的基于芳基的不对称PCS-钳子配合物的合成和催化应用。从对称的α，α-二溴-间二甲苯开始制备稳定的空气和水分稳定的PCS-夹钳式钯络合物5 [X]，包括用PPh2ACHTUNGTRENUNG（BH3）选择性取代一种溴化物，然后用SPh和CH2取代第二种溴化物。随后引入钯。新的PCS配合物（5 [X]）被用作两个重要的有机转化催化剂。首先，络合物5 [Cl]在醛醇缩合反应中显示出高催化活性，但作为预催化剂进入催化循环。其次，络合物5-乙酰苯并[BF4]在六甲基二锡存在下，在烯丙基氯与醛和亚胺的偶联中表现出串联催化活性。在这些串联催化反应中，第一个过程是用Sn2Me6将烯丙基氯化物转化为三甲基烯丙基甜菜碱（氯化三苯甲基锡），然后进行醛和亚磺胺底物的催化烯丙基化。此外，我们提出了一种新的催化方法，用于4-硝基苯甲醛与乙烯基环氧乙烷的一锅化烯丙基化。比较了新型PCS-pincer钯配合物与对称PCP-和SCSpincer配合物类似物的催化性能。得出的结论是，不对称的PCS配合物有利地统一了相应的对称钳形配合物的吸引人的催化特征，包括（p-）吸电子（如磷）或（s-）供电子（如硫和氮）杂原子。因此，在醛醇缩合反应中，PCS-夹钳钯配合物5 [X]提供了高周转频率，而在串联过程中，两个反应均以足够高的活性被催化。

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