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Ternary complexes of chiral disulfonimides in transfer-hydrogenation of imines: the relevance of late intermediates in ion pair catalysis
In ion pairing catalysis, the structures of late intermediates and transition states are key to understanding and further development of the field. Typically, a plethora of transition states is explored computationally. However, especially for ion pairs the access to energetics via computational che...
Autores principales: | , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
The Royal Society of Chemistry
2021
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8635212/ https://www.ncbi.nlm.nih.gov/pubmed/34976346 http://dx.doi.org/10.1039/d1sc03724b |
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author | Žabka, Matej Gschwind, Ruth M. |
author_facet | Žabka, Matej Gschwind, Ruth M. |
author_sort | Žabka, Matej |
collection | PubMed |
description | In ion pairing catalysis, the structures of late intermediates and transition states are key to understanding and further development of the field. Typically, a plethora of transition states is explored computationally. However, especially for ion pairs the access to energetics via computational chemistry is difficult and experimental data is rare. Here, we present for the first time extensive NMR spectroscopic insights about the ternary complex of a catalyst, substrate, and reagent in ion pair catalysis exemplified by chiral Brønsted acid-catalyzed transfer hydrogenation. Quantum chemistry calculations were validated by a large amount of NMR data for the structural and energetic assessment of binary and ternary complexes. In the ternary complexes, the expected catalyst/imine H-bond switches to an unexpected O–H–N structure, not yet observed in the multiple hydrogen-bond donor–acceptor situation such as disulfonimides (DSIs). This arrangement facilitates the hydride transfer from the Hantzsch ester in the transition states. In these reactions with very high isomerization barriers preventing fast pre-equilibration, the reaction barriers from the ternary complex to the transition states determine the enantioselectivity, which deviates from the relative transition state energies. Overall, the weak hydrogen bonding, the hydrogen bond switching and the special geometrical adaptation of substrates in disulfonimide catalyst complexes explain the robustness towards more challenging substrates and show that DSIs have the potential to combine high flexibility and high stereoselectivity. |
format | Online Article Text |
id | pubmed-8635212 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2021 |
publisher | The Royal Society of Chemistry |
record_format | MEDLINE/PubMed |
spelling | pubmed-86352122021-12-30 Ternary complexes of chiral disulfonimides in transfer-hydrogenation of imines: the relevance of late intermediates in ion pair catalysis Žabka, Matej Gschwind, Ruth M. Chem Sci Chemistry In ion pairing catalysis, the structures of late intermediates and transition states are key to understanding and further development of the field. Typically, a plethora of transition states is explored computationally. However, especially for ion pairs the access to energetics via computational chemistry is difficult and experimental data is rare. Here, we present for the first time extensive NMR spectroscopic insights about the ternary complex of a catalyst, substrate, and reagent in ion pair catalysis exemplified by chiral Brønsted acid-catalyzed transfer hydrogenation. Quantum chemistry calculations were validated by a large amount of NMR data for the structural and energetic assessment of binary and ternary complexes. In the ternary complexes, the expected catalyst/imine H-bond switches to an unexpected O–H–N structure, not yet observed in the multiple hydrogen-bond donor–acceptor situation such as disulfonimides (DSIs). This arrangement facilitates the hydride transfer from the Hantzsch ester in the transition states. In these reactions with very high isomerization barriers preventing fast pre-equilibration, the reaction barriers from the ternary complex to the transition states determine the enantioselectivity, which deviates from the relative transition state energies. Overall, the weak hydrogen bonding, the hydrogen bond switching and the special geometrical adaptation of substrates in disulfonimide catalyst complexes explain the robustness towards more challenging substrates and show that DSIs have the potential to combine high flexibility and high stereoselectivity. The Royal Society of Chemistry 2021-11-17 /pmc/articles/PMC8635212/ /pubmed/34976346 http://dx.doi.org/10.1039/d1sc03724b Text en This journal is © The Royal Society of Chemistry https://creativecommons.org/licenses/by-nc/3.0/ |
spellingShingle | Chemistry Žabka, Matej Gschwind, Ruth M. Ternary complexes of chiral disulfonimides in transfer-hydrogenation of imines: the relevance of late intermediates in ion pair catalysis |
title | Ternary complexes of chiral disulfonimides in transfer-hydrogenation of imines: the relevance of late intermediates in ion pair catalysis |
title_full | Ternary complexes of chiral disulfonimides in transfer-hydrogenation of imines: the relevance of late intermediates in ion pair catalysis |
title_fullStr | Ternary complexes of chiral disulfonimides in transfer-hydrogenation of imines: the relevance of late intermediates in ion pair catalysis |
title_full_unstemmed | Ternary complexes of chiral disulfonimides in transfer-hydrogenation of imines: the relevance of late intermediates in ion pair catalysis |
title_short | Ternary complexes of chiral disulfonimides in transfer-hydrogenation of imines: the relevance of late intermediates in ion pair catalysis |
title_sort | ternary complexes of chiral disulfonimides in transfer-hydrogenation of imines: the relevance of late intermediates in ion pair catalysis |
topic | Chemistry |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8635212/ https://www.ncbi.nlm.nih.gov/pubmed/34976346 http://dx.doi.org/10.1039/d1sc03724b |
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