Absolute Configuration and Conformation of Two Frater-Seebach Alkylation Reaction Products by Film VCD and ECD Spectroscopic Analyses
Absolute Configuration and Conformation of Two Frater-Seebach Alkylation Reaction Products by Film VCD and ECD Spectroscopic Analyses
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DOI：
10.1021/jo502438a
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发表时间：
2015-01-02
影响因子：
3.6
通讯作者：
Xu, Yunjie
中科院分区：
文献类型：
--
作者：
Poopari, Mohammad Reza;Dezhahang, Zahra;Xu, Yunjie
两个手性光谱技术，即电子和振动圆二色性（ECD和VCD），以及NMR光谱已被用来确定两个Frater Seebach烷基化反应产物与长烃链的绝对构型和几何形状。实验研究得到了密度泛函理论计算的补充。已观察到这两种化合物在薄膜状态下在羰基伸缩区域的强特征双信号VCD签名。截断模型，即，没有长的CH 2链，已被用来检查两个单体部分之间的不同的氢键拓扑结构，并模拟相应的IR和VCD光谱的二聚体。此外，激子耦合模型也被应用到两个单体部分的C-O基团，这可以通过分子间氢键耦合。在这些简化方法的基础上，化合物的绝对构型已明确指定使用VCD和ECD光谱。在IR和UVvis区域的光谱模拟也进行了与完整的二聚体，以验证截断模型的适应性。研究表明，结合薄膜VCD和ECD技术是一种比较简单的方法来确定这类合成化合物的绝对构型。
Two chiroptical spectroscopic techniques, namely, electronic and vibrational circular dichroism (ECD and VCD), as well as NMR spectroscopy have been utilized to determine the absolute configurations and geometries of two Frater Seebach alkylation reaction products with long hydrocarbon chains. The experimental studies have been complemented with density functional theory calculations. Strong characteristic bisignate VCD signatures in the carbonyl stretching region have been observed for both compounds in film state. Truncated models, i.e., without the long CH2 chains, have been utilized to examine different hydrogen-bonding topologies between two monomeric moieties and to simulate the corresponding IR and VCD spectra of the dimers. In addition, the exciton coupling model has also been applied to the C-O groups of the two monomeric moieties, which can be coupled through intermolecular hydrogen-bonding. On the basis of these simplified approaches, the absolute configurations of the compounds have been unambiguously assigned using VCD and ECD spectroscopy. Spectral simulations in the IR and UVvis regions have also been carried out with the full dimers to validate the fitness of the truncated model. The study shows that the combination of the film VCD and ECD techniques is a relatively straightforward method to determine the absolution configurations of such synthetic compounds.