NMR studies of chemical exchange amongst five conformers of a ten-membered ring compound containing two amide bonds and a disulfide †

Bain, Alex D.; Bell, Russell A.; Fletcher, Daniel A.; Hazendonk, Paul; Maharajh, Rob A.; Rigby, Suzie S.; Valliant, John F.

doi:10.1039/a900502a

Cited by 15 publications

(11 citation statements)

References 43 publications

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“…The power of one‐ and two‐dimensional NMR methods for determining equilibrium constants and exchange rates was demonstrated by Bain and co‐workers, fully deciphering conformational dynamics of a ten‐membered ring 47 (Scheme , only conformers a – b shown) containing two amide bonds and a disulfide link. In this case, barriers to fragment flips in the range 18–20 kcal mol −1 were identified (an analogous interconversion of calix[6]arenes is slow too, 17–21 kcal mol −1 ) …”

Section: Intramolecular Rotationmentioning

confidence: 99%

Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy

Nikitin

O'Gara

2019

Chemistry A European J

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Detailed mechanistic information is crucial to our understanding of reaction pathways and selectivity. Dynamic exchange NMR techniques, in particular 2D exchange spectroscopy (EXSY) and its modifications, provide indispensable intricate information on the mechanisms of organic and inorganic reactions and other phenomena, for example, the dynamics of interfacial processes. In this Review, key results from exchange NMR studies of small molecules over the last few decades are systemised and discussed. After a brief introduction to the theory, the key types of dynamic processes are identified and fundamental examples given of intra‐ and intermolecular reactions, which, in turn, could involve, or not, bond‐making and bond‐breaking events. Following that logic, internal molecular rotation, intramolecular stereomutation and molecular recognition will first be considered because they do not typically involve bond breaking. Then, rearrangements, substitution‐type reactions, cyclisations, additions and other processes affecting chemical bonds will be discussed. Finally, interfacial molecular dynamics and unexpected combinations of different types of fluxional processes will also be highlighted. How exchange NMR spectroscopy helps to identify conformational changes, coordination and molecular recognition processes as well as quantify reaction energy barriers and extract detailed mechanistic information by using reaction rate theory in conjunction with computational techniques will be shown.

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Section: Intramolecular Rotationmentioning

confidence: 99%

Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy

Nikitin

O'Gara

2019

Chemistry A European J

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“…Compound 16 provides a relevant example of disulfide linkage in a rather flexible 10-membered ring . Five conformers of similar energies were in equilibrium as seen in the NMR spectra.…”

Section: Resultsmentioning

confidence: 99%

“…Selected model compounds from literature providing examples of barrier to inversion in oxamide 15 , disulfide linkage 16 and N-alkenyl axis 17 …”

Section: Resultsmentioning

confidence: 99%

Atropisomerism in a 10-Membered Ring with Multiple Chirality Axes: (3Z,9Z)-1,2,5,8-Dithiadiazecine-6,7(5H,8H)-dione Series

et al. 2018

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For the first time, chirality in (3 Z,9 Z)-1,2,5,8-dithiadiazecine-6,7(5 H,8 H)-dione series was recognized. Enantiomers of the 4,9-dimethyl-5,8-diphenyl analogue were isolated at room temperature, and their thermal stability was determined. X-ray crystallography confirmed the occurrence of a pair of enantiomers in the crystal. Absolute configurations were assigned by comparing experimental and calculated vibrational/electronic circular dichroism spectra of isolated enantiomers. A distorted tesseract (four-dimensional hypercube) was used to visualize the calculated enantiomerization process, which requires the rotation around four chirality axes. Conformers of higher energy as well as several concurrent pathways of similar energies were revealed.

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“…When exploring the limits of accuracy in determining activation parameters using a three‐experiment approach, he was able to discern differences in effect of various solvents on the entropy of activation of an internal rotation process in furfural . His pursuits at tackling systems with ever increasing dynamic complexity were epitomized by a study on DADS, where 4 simultaneous processes were studied using selective inversion and line‐shape methods, achieving unprecedented accuracy determining their activation enthalpies and entropies to within 1 kJ/mol and 5 J/molK, respectively . His reformulation of dynamic NMR was extended to the solid state using sparse matrix methods and Floquet theory .…”

Section: The Scientistmentioning

confidence: 99%

A tribute to Alexander Davidson Bain: An NMR pioneer and mentor at McMaster University

Anand

Berno

Boulton

et al. 2016

Concepts Magnetic Resonance

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In this tribute to our friend, mentor and colleague Alexander Davidson Bain we have collectively recapitulated the milestones of his career at McMaster university. We start from Alex's scientific and educational achievements and continue with his accomplishments as a community and infrastructure builder. We attempt to provide a sense of the breadth and depth of his seemingly endless scientific contributions while at McMaster by briefly summarizing selected representative examples from his body of work. Following Alex's lead, the scientific account is mixed with anecdotes and "bits of wisdom" we fondly remember from our interactions and collaborations with him. We also touch upon his brilliant and nurturing educational style and his "aggregator" role within the McMaster and wider NMR communities. We conclude with a more personal picture of Alex D. Bain, in which his scientific excellence and profound intellect are inextricably tied to his kind, nurturing and optimistic character and to his uniquely wry humor. He was not just a "good guy," he was the epitome of the "good guy."

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NMR studies of chemical exchange amongst five conformers of a ten-membered ring compound containing two amide bonds and a disulfide †

Cited by 15 publications

References 43 publications

Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy

Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy

Atropisomerism in a 10-Membered Ring with Multiple Chirality Axes: (3Z,9Z)-1,2,5,8-Dithiadiazecine-6,7(5H,8H)-dione Series

A tribute to Alexander Davidson Bain: An NMR pioneer and mentor at McMaster University

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