Ambimodal Transition States in Diels–Alder Cycloadditions of Tropolone and Tropolonate with N-Methylmaleimide**

Hong Zhang; Mathias Kirk Thøgersen; Cooper S. Jamieson; Xiao Song Xue; Karl Anker Jørgensen; Kendall N. Houk

doi:10.1002/anie.202109608

Ambimodal Transition States in Diels–Alder Cycloadditions of Tropolone and Tropolonate with N-Methylmaleimide**

Hong Zhang^*, Mathias Kirk Thøgersen, Cooper S. Jamieson, Xiao Song Xue, Karl Anker Jørgensen^*, Kendall N. Houk^*

^*Corresponding author for this work

Department of Chemistry

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

Abstract

The Diels–Alder reactions of tropolone and its conjugate base with N-methylmaleimide have been explored computationally and experimentally. Previous studies of the [4+2] cycloaddition under basic conditions show that both endo- and exo-products are obtained in similar, but variable amounts. Density functional theory (ωB97X-D) explorations of potential energy surfaces, and molecular dynamics trajectories show that the reaction involves an ambimodal transition state for the reaction of the ammonium tropolonate with N-methylmaleimide, and that similar amounts of endo- and exo-products are obtained. The thermal reaction, studied experimentally in detail here for the first time, is predicted to form the endo-adduct through an ambimodal transition state. The exo-adduct can be formed from the same transition state, but requires a hydrogen shift, that hinders this reaction dynamically. Longer reaction times give a small excess of the exo-product, which is thermodynamically more stable.

Original language	English
Journal	Angewandte Chemie - International Edition
Volume	60
Issue	47
Pages (from-to)	24991-24996
Number of pages	6
ISSN	1433-7851
DOIs	https://doi.org/10.1002/anie.202109608
Publication status	Published - Nov 2021

Keywords

cycloaddition reactions
molecular dynamics
periselectivity

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10.1002/anie.202109608

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title = "Ambimodal Transition States in Diels–Alder Cycloadditions of Tropolone and Tropolonate with N-Methylmaleimide**",

abstract = "The Diels–Alder reactions of tropolone and its conjugate base with N-methylmaleimide have been explored computationally and experimentally. Previous studies of the [4+2] cycloaddition under basic conditions show that both endo- and exo-products are obtained in similar, but variable amounts. Density functional theory (ωB97X-D) explorations of potential energy surfaces, and molecular dynamics trajectories show that the reaction involves an ambimodal transition state for the reaction of the ammonium tropolonate with N-methylmaleimide, and that similar amounts of endo- and exo-products are obtained. The thermal reaction, studied experimentally in detail here for the first time, is predicted to form the endo-adduct through an ambimodal transition state. The exo-adduct can be formed from the same transition state, but requires a hydrogen shift, that hinders this reaction dynamically. Longer reaction times give a small excess of the exo-product, which is thermodynamically more stable.",

keywords = "cycloaddition reactions, molecular dynamics, periselectivity",

author = "Hong Zhang and Th{\o}gersen, {Mathias Kirk} and Jamieson, {Cooper S.} and Xue, {Xiao Song} and J{\o}rgensen, {Karl Anker} and Houk, {Kendall N.}",

year = "2021",

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doi = "10.1002/anie.202109608",

language = "English",

volume = "60",

pages = "24991--24996",

journal = "Angewandte Chemie - International Edition",

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Ambimodal Transition States in Diels–Alder Cycloadditions of Tropolone and Tropolonate with N-Methylmaleimide**. / Zhang, Hong; Thøgersen, Mathias Kirk; Jamieson, Cooper S. et al.
In: Angewandte Chemie - International Edition, Vol. 60, No. 47, 11.2021, p. 24991-24996.

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

TY - JOUR

T1 - Ambimodal Transition States in Diels–Alder Cycloadditions of Tropolone and Tropolonate with N-Methylmaleimide**

AU - Zhang, Hong

AU - Thøgersen, Mathias Kirk

AU - Jamieson, Cooper S.

AU - Xue, Xiao Song

AU - Jørgensen, Karl Anker

AU - Houk, Kendall N.

PY - 2021/11

Y1 - 2021/11

N2 - The Diels–Alder reactions of tropolone and its conjugate base with N-methylmaleimide have been explored computationally and experimentally. Previous studies of the [4+2] cycloaddition under basic conditions show that both endo- and exo-products are obtained in similar, but variable amounts. Density functional theory (ωB97X-D) explorations of potential energy surfaces, and molecular dynamics trajectories show that the reaction involves an ambimodal transition state for the reaction of the ammonium tropolonate with N-methylmaleimide, and that similar amounts of endo- and exo-products are obtained. The thermal reaction, studied experimentally in detail here for the first time, is predicted to form the endo-adduct through an ambimodal transition state. The exo-adduct can be formed from the same transition state, but requires a hydrogen shift, that hinders this reaction dynamically. Longer reaction times give a small excess of the exo-product, which is thermodynamically more stable.

AB - The Diels–Alder reactions of tropolone and its conjugate base with N-methylmaleimide have been explored computationally and experimentally. Previous studies of the [4+2] cycloaddition under basic conditions show that both endo- and exo-products are obtained in similar, but variable amounts. Density functional theory (ωB97X-D) explorations of potential energy surfaces, and molecular dynamics trajectories show that the reaction involves an ambimodal transition state for the reaction of the ammonium tropolonate with N-methylmaleimide, and that similar amounts of endo- and exo-products are obtained. The thermal reaction, studied experimentally in detail here for the first time, is predicted to form the endo-adduct through an ambimodal transition state. The exo-adduct can be formed from the same transition state, but requires a hydrogen shift, that hinders this reaction dynamically. Longer reaction times give a small excess of the exo-product, which is thermodynamically more stable.

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Ambimodal Transition States in Diels–Alder Cycloadditions of Tropolone and Tropolonate with N-Methylmaleimide**

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Keywords

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Asymmetric Organocatalytic Higher-Order Cycloadditions

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