Theoretical Studies of Rare-Earth-Catalyzed [3 + 2] Annulation of Aromatic Aldimine with Styrene: Mechanism and Origin of Diastereoselectivity,The Journal of Organic Chemistry

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Theoretical Studies of Rare-Earth-Catalyzed [3 + 2] Annulation of Aromatic Aldimine with Styrene: Mechanism and Origin of Diastereoselectivity
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2021-02-22 , DOI: 10.1021/acs.joc.0c03060
Pan Wang ₁ , Gen Luo ₂ , Jimin Yang ₁ , Xuefeng Cong ₃ , Zhaomin Hou _{1,

3} , Yi Luo _{1,

4}

Affiliation

The synthesis of multisubstituted 1-aminoindanes through catalyst-controlled diastereodivergent [3 + 2] annulation of aromatic imines with alkenes is of great interest and importance. An understanding of the exact reaction mechanism, especially for the origin of diastereoselectivity, is an essential aspect for further development of such reactions. In this study, density functional theory calculations have been carried out on the rare-earth-catalyzed diastereodivergent [3 + 2] annulation of benzaldimine with styrene. The results show that the reaction mainly involves generation of active species, olefin insertion, cyclization, and protonation steps. The noncovalent interactions, such as C–H···π and metal···π interactions, play an important role in stabilizing the key transition state or intermediate. Both steric and electronic factors account for the diastereoselectivity. The preferred cis-diastereoselectivity could be ascribed to more efficient orbital interaction, while the crowded space will induce the formation of a C–H···π interaction between the N^tBu group and benzene ring in a trans-diastereoselectivity manner, thus stabilizing the trans-selective transition state. Therefore, the stereospecific product could be obtained by fine-tuning the ligand/metal combination of the catalysts.

中文翻译：

稀土催化的苯丙氨酸与亚胺[3 + 2]环空的理论研究：非对映选择性的机理和成因

通过催化剂控制的芳族亚胺与烯烃的非对映异构体的[3 + 2]环合反应合成多取代的1-氨基茚满具有极大的意义和重要性。了解确切的反应机理，特别是对于非对映选择性的起源，是进一步发展此类反应的重要方面。在这项研究中，密度泛函理论计算已进行了苯并二胺与苯乙烯的稀土催化非对映异构[3 + 2]环化反应。结果表明，该反应主要涉及活性物种的产生，烯烃的插入，环化和质子化步骤。非共价相互作用，例如C–H···π和金属···π相互作用，在稳定关键过渡态或中间态方面起着重要作用。空间因素和电子因素均引起非对映选择性。首选顺-非对映选择性可归因于更有效的轨道相互作用，而拥挤的空间将以反-非对映选择性的方式诱导N ^t Bu基团与苯环之间形成C–H···π相互作用，从而稳定反式-选择性过渡状态。因此，可以通过对催化剂的配体/金属组合进行微调来获得立体定向产物。

更新日期：2021-03-05

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