DFT study on the palladium-catalyzed allylation of primary amines by allylic alcohol
DFT study on the palladium-catalyzed allylation of primary amines by allylic alcohol
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DOI：
10.1021/ja0621997
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发表时间：
2006-11-08
影响因子：
15
通讯作者：
le Floch, Pascal
中科院分区：
文献类型：
--
作者：
Piechaczyk, Olivier;Thoumazet, Claire;le Floch, Pascal
用密度泛函理论（B3 PW 91，PCM）研究了钯催化的伯胺烯丙基化反应，探讨了两种可能的反应机理。第一种机制依赖于阳离子双钯配合物的形成。它们的形成涉及一个质子从铵的氮原子到C β碳原子的金属辅助的形式（1，3）移位。循环的第二部分依赖于通过五配位的18 VE双钯络合物的配体交换。最后一步可能通过双分子途径进行，形式上包括从烯丙基铵到复合物的醇基的质子转移。第二种机制，这是更接近目前承认的亲核烯丙基取代，依赖于协调的烯丙基铵的解络合，似乎是有利的。这种催化循环重新计算模型配合物不同的配体，并进行了电荷分解分析，以评估配体的电子性质的影响。为了将我们的结果与竞争性实验进行比较，还对真实的配体进行了CDA计算。在协议与实验观察，这个过程被发现是强烈的配体依赖性，解络合被强π受体配体的青睐。这些计算使我们在实验上表明配合物[ Pd（P（OPh）（3））（2）（eta（3）-C3 H5）][ OTf]是该烯丙基化反应的有效催化剂。最后，该催化过程被证明对胺的性质敏感，碱性差的胺有利于催化前体的再形成。
The palladium-catalyzed allylation of primary amines has been investigated by DFT calculations (B3PW91, PCM method), and two potential mechanisms were studied. The first mechanism relies on the formation of cationic hydridopalladium complexes. Their formation involves a metal-assisted formal (1,3) shift of a proton from the nitrogen atom of an ammonium to the C beta carbon atom. The second part of the cycle relies on a ligand exchange through a pentacoordinated 18VE hydridopalladium complex. The last step likely proceeds through a bimolecular pathway and formally consists of a proton transfer from the allylammonium to the alcohol group of the complex. The second mechanism, which is closer to that currently admitted for nucleophilic allylic substitutions, relies on the decomplexation of the coordinated allylammonium and appears to be favored. This catalytic cycle was recomputed on model complexes varying the ligands, and a charge decomposition analysis was carried out to assess the influence of the electronic properties of the ligands. To compare our results with competitive experiments, CDA calculations were also performed on real ligands. In agreement with experimental observations, this process was found to be strongly ligand dependent, decomplexation being favored by strong pi-acceptor ligands. These calculations led us to show experimentally that complex [ Pd(P(OPh)(3))(2)(eta(3)-C3H5)][ OTf] is an efficient catalyst for this allylation. Finally, this catalytic process proved to be sensitive to the nature of the amine, with poorly basic amines favoring the re-formation of the catalytic precursor.