Theoretical investigation on SnCl4-catalyzed tandem dimerization/oxy-2-azonia-Cope rearrangements between beta,gamma-unsaturated ketones and imines
Theoretical investigation on SnCl4-catalyzed tandem dimerization/oxy-2-azonia-Cope rearrangements between beta,gamma-unsaturated ketones and imines
复制标题
SnCl4催化β,γ不饱和酮与亚胺串联二聚/oxy-2-azonia-Cope重排的理论研究
DOI：
10.1007/s00214-014-1606-2
复制
发表时间：
2015
影响因子：
1.7
通讯作者：
Li Zhi-Ming
中科院分区：
文献类型：
--
作者：
Zhang Liang;Wang Jing-Mei;Wang Quan-Rui;Zhang Dan-Wei;Li Zhan-Ting;Li Zhi-Ming
采用极化连续溶剂化模型增强的B3 LYP密度泛函方法，对刘易斯酸催化的β，γ-不饱和酮和亚胺的氧-2-偶氮-Cope重排反应生成高烯丙基酰胺和内酰胺的机理进行了理论研究.据预测，SnCl 4催化的串联二聚/氧基-2-azonia-Cope重排机制是高度优选的非催化版本，以及合理的串联二聚/Prins重排机制。发现整个反应为两步反应，包括最初的亲核二聚反应和随后的[3，3]-σ迁移重排反应。后一阶段被认为是限速步骤。特别地，过渡态解释了实验观察到的立体选择性和Z/E选择性。手性环状底物的高立体选择性和Z/E选择性归因于TS的相对构象稳定性。此外，畸变相互作用分析已经进行了尝试，以量化的各种贡献的反应过渡态，它揭示了相互作用能EintII和畸变能EintEdI与2COM 2复合物的形成是决定因素，以定义的Z/E选择性的九元环和十元环途径，分别。乙烯亚胺参与的反应的调查预测的途径中的一个相对非常低的障碍，因此，该序列可能是一个有用的策略，用于合成大环内酰胺。
The mechanism of the Lewis acid-catalyzed oxy-2-azonia-Cope rearrangement between β,γ-unsaturated ketones and imines leading to the formation of homoallylic amides and lactams has been theoretically studied using the B3LYP density functional theory methods enhanced with a polarized continuum solvation model. It was predicted that the SnCl4-catalyzed tandem dimerization/oxy-2-azonia-Cope rearrangement mechanism is highly preferred over the uncatalyzed version as well as the plausible tandem dimerization/Prins rearrangement mechanism. A two-step pathway was found for the overall reaction, involving the initial nucleophilic dimerization followed by the [3,3]-sigmatropic rearrangement. The latter phase was considered to be the rate-limiting step. Particularly, the transition states account for the experimentally observed stereoselectivities andZ/Eselectivities. The high stereoselectivity andZ/Eselectivity for the chiral cyclic substrates can be attributed to the relative conformational stabilities of TSs. Moreover, distortion–interaction analysis has been performed in an attempt to quantify the various contributions to the reaction transition states, and it revealed that interaction energyEintIIand distortion energy ∆EdIassociated with the formation of the2COM2complex are the determining factors to define theZ/Eselectivities for nine- and ten-membered ring pathway, respectively. Investigation on the ethyleneimine-involved reaction predicts a relatively very low barrier in the pathway; thus, the sequence might be a useful strategy for synthesis of macrolactams.