Origin of Enantioselectivity in Palladium-Catalyzed Asymmetric Allylic Alkylation Reactions Using Aminophosphine Ligands
Origin of Enantioselectivity in Palladium-Catalyzed Asymmetric Allylic Alkylation Reactions Using Aminophosphine Ligands
复制标题
使用氨基膦配体的钯催化不对称烯丙基烷基化反应中对映选择性的起源
DOI：
10.1021/om0105369
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发表时间：
2002
期刊：
影响因子：
2.8
通讯作者：
V. Félix
中科院分区：
文献类型：
--
作者：
M. Widhalm;U. Nettekoven;H. Kalchhauser;K. Mereiter;M. Calhorda;V. Félix
研究了三种结构相关的手性PN配体在钯催化的烯丙基烷基化反应中的不对称诱导作用，它们都含有一个联萘单元和一个苄基（1）或二茂铁基甲基（2，3）片段桥接磷和氮络合位点.中间体烯丙基钯（II）配合物的配体1−3已被分离和光谱表征。对于其中的两个，1K和3K，晶体结构已被确定。根据DFT（ADF）和分子力学（CERIUS 2）计算结果，提出了一个合理化的分子水平上的实验结果。对整个分子和更简单模型的研究表明，立体化学结果不是由电子效应决定的，而主要是由空间排斥的微妙平衡决定的。特别是，在螯合物链中存在的苄基或二茂铁甲基对其排列有很强的影响，从而直接影响其结构。
The asymmetric induction observed in palladium-catalyzed allylic alkylation reactions with typical substrates was investigated using three structurally related chiral PN ligands, which all contain a binaphthyl unit and either a benzyl (1) or ferrocenylmethyl (2, 3) fragment bridging phosphorus and nitrogen complexation sites. The intermediate allyl palladium(II) complexes of ligands 1−3 have been isolated and spectroscopically characterized. For two of them, 1K and 3K, the crystal structure has been determined. A rationalization of the experimental findings on a molecular level is proposed based on the results of DFT (ADF) and molecular mechanics (CERIUS2) calculations. Studies on both the entire molecules and simpler models indicate that the stereochemical outcome is not determined by electronic effects, but mostly by a delicate balance of steric repulsions. In particular, the presence of a benzyl or a ferrocenylmethyl group in the chelate chain has a strong effect on its arrangement, thereby directly in...