Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Scope and Mechanistic Studies,Journal of the American Chemical Society

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Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Scope and Mechanistic Studies
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2017-11-17 00:00:00 , DOI: 10.1021/jacs.7b08976
Thomas M. Bräuer ₁ , Qi Zhang ₁ , Konrad Tiefenbacher _{1,

2}

Affiliation

Although iminium catalysis has become an important tool in organic chemistry, its combination with supramolecular host systems has remained largely unexplored. We report the detailed investigations into the first example of iminium catalysis inside a supramolecular host. In the case of 1,4-reductions of α,β-unsaturated aldehydes, catalytic amounts of host are able to increase the enantiomeric excess of the products formed. Several control experiments were performed and provided strong evidence that the modulation of enantiomeric excess of the reaction product indeed stems from a reaction on the inside of the capsule. The origin of the increased enantioselectivity in the capsule was investigated. Furthermore, the substrate and nucleophile scope were studied. Kinetic investigations as well as the kinetic isotope effect measured confirmed that the hydride delivery to the substrate is the rate-determining step inside the capsule. The exploration of benzothiazolidines as alternative hydride sources revealed an unexpected substitution effect of the hydride source itself. The results presented confirm that the noncovalent combination of supramolecular hosts with iminium catalysis is opening up new exciting possibilities to increase enantioselectivity in challenging reactions.

中文翻译：

自组装超分子胶囊中的铟催化：范围和机理研究

尽管亚胺催化已成为有机化学中的重要工具，但其与超分子宿主系统的结合仍未得到充分开发。我们报告了在超分子宿主内部亚胺催化的第一个例子的详细研究。在α，β-不饱和醛的1，4-还原的情况下，主体的催化量能够增加所形成产物的对映体过量。进行了几次对照实验，并提供了强有力的证据，证明对映体过量反应产物的调节确实源自胶囊内部的反应。研究了胶囊中对映选择性增加的起源。此外，研究了底物和亲核试剂的范围。动力学研究以及所测得的动力学同位素效应证实，氢化物向底物的传递是胶囊内部决定速率的步骤。对苯并噻唑烷作为替代氢化物来源的探索揭示了氢化物来源本身的出乎意料的取代作用。提出的结果证实，超分子主体与亚胺基催化的非共价结合为提高挑战性反应中的对映选择性开辟了新的令人兴奋的可能性。

更新日期：2017-11-19

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