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首页> 外文期刊>Chemistry: A European journal >Origin of Diastereoselectivity in the Organolanthanide-Mediated Intramolecular Hydroamination/Cyclisation of Aminodienes:A Computational Exploration of Constrained Geometry CGC-Ln Catalysts
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Origin of Diastereoselectivity in the Organolanthanide-Mediated Intramolecular Hydroamination/Cyclisation of Aminodienes:A Computational Exploration of Constrained Geometry CGC-Ln Catalysts

机译：非有机锡介导的分子内加氢胺化/氨基二烯环化中非对映选择性的起源：约束几何CGC-Ln催化剂的计算探索

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摘要

The regulation of ring-sub-stituent diastereoselectivity in the intramolecular hydroamination/cyclisa-tion(IHC)of alpha-substituted aminodienes by constrained geometry CGC-lanthanide catalysts(CGC = [Me2Si(eta~5-Me4C5)(rBuN)]~(2-))has been elucidated by means of a reliable DFT method.The first survey of relevant elementary steps for the 1-methyl-(4E,6)-heptadie-nylamine substrate(1)and the [{Me2Si-(eta~5-Me4C5)(rBuN)}Sm{N(TMS)2}] starting material(2)identified the following general mechanistic aspects of Ln-cata-lysed aminodiene IHC.The substrate-adduct 3-S of the active CGC-Ln-ami-dodiene compound represents the catalyst's resting state,but the substrate-free form 3' with a chelating amido- diene functionality is the direct precursor for cyclisation.This step proceeds with almost complete regioselectivity through exocyclic ring closure by means of a frontal trajectory,giving rise to the CGC-Ln-azacycle intermediate 4.Subsequent protonolysis of 4 is turnover limiting,whilst the ring-substituent diastereoselectivity is dictated by exocyclic ring closure.Unfavourable close interatomic contacts between the substrate's a-substituent and the catalyst backbone have been shown to largely govern the trans/cis selectivity.Substituents of sufficient bulk in the alpha-position of the substrate have been identified as being vital for stereochemical induction.The present study has indicated that the diastereoselectivity of ring closure can be considerably modulated.The variation of the lantha-nide's ionic radius and introduction of extra steric pressure at the substrate's a-position and/or the CGC N centre have been identified as effective handles for tuning the selectivity.The quantification of these factors reported herein represents the first step toward the rational design of improved CGC-Ln catalyst architectures and will thus aid this process.
机译：约束几何CGC-镧系元素催化剂对α-取代的氨基二烯分子内加氢/环化（IHC）中环取代基非对映选择性的调节（CGC = [Me2Si（eta〜5-Me4C5）（rBuN）]〜（已通过可靠的DFT方法阐明了2-））。对1-甲基-（4E，6）-庚二烯基胺（1）和[{Me2Si-（eta〜 5-Me4C5）（rBuN）} Sm {N（TMS）2}]起始材料（2）确定了Ln催化的氨基二烯IHC的以下一般机理。活性CGC-Ln的底物加合物3-S -ami-dodiene化合物代表催化剂的静止状态，但具有螯合氨基-二烯官能度的无底物形式3'是环化的直接前体。该步骤通过额线轨迹通过环外环的闭合几乎完全实现了区域选择性，从而产生CGC-Ln-氮杂双环中间体4。随后的4的质子分解限制了周转，取代基的非对映选择性是由环外环闭环决定的，已证明底物的a-取代基与催化剂骨架之间不利的紧密原子间接触主要决定了反式/顺式选择性。本研究表明，闭环的非对映选择性可以得到显着调节。镧系元素离子半径的变化以及在底物的a位置和/或CGC N处引入额外的空间压力本文所报道的这些因素的量化是朝着合理设计改进的CGC-Ln催化剂结构的第一步，因此将有助于这一过程。

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