NMR Spectroscopic Studies of Lithium Diethylamide:  Insights into Ring Laddering

Rutherford, Jennifer L.; Collum, David B.

doi:10.1021/ja992169m

Cited by 46 publications

(32 citation statements)

References 17 publications

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“…In 1999, Rutherford and Collum showed by low-temperature 6 Li and 15 NNMR spectroscopy that the lighter congener of LDA, lithium diethyl amide (LiDEA), can exist as several oligomers in THF and oxetane solutions. [20] In neat THF or oxetane,LiDEA is acyclic dimer.Atlower concentrations of donor base,c yclic oligomers appear.A tl ow THF concentrations (2-10 equiv) ac yclic trimer and af our-rung ladder form. Higher-order ladders were not observed within the solubility limits of LiDEA, but at substoichiometric oxetane concentrations they noticed ar elatively complex LiDEA equilibrium of cyclic dimers,trimers,and ladders of tetramers, pentamers,and hexamers.According to this work and to the lithium amide ring-stacking and laddering principle, [21] the assumption that this signal from oligomer 4 stems from the LDAhexamer appears to be valid.…”

Section: Methodsmentioning

confidence: 99%

The Donor‐Base‐Free Aggregation of Lithium Diisopropyl Amide in Hydrocarbons Revealed by a DOSY Method

2015

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Lithium diisopropyl amide (LDA) is a very prominent reagent that plays a key role in organic synthesis, serving as a base par excellence for a broad range of deprotonation reactions. However, the state of aggregation in solution in the absence of donor bases was unclear. In this paper we solved this problem by employing DOSY NMR experiments based on a newly elaborated external calibration curve (ECC) approach with normalized diffusion coefficients.

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Section: Methodsmentioning

confidence: 99%

The Donor‐Base‐Free Aggregation of Lithium Diisopropyl Amide in Hydrocarbons Revealed by a DOSY Method

2015

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“…Im Jahr 1999 untersuchten Rutherford und Collum Lithiumdiethylamid (LiDEA, das leichte Homologe des LDAs) in THF‐ und Oxetan‐Lösung mittels 6 Li‐ und 15 N‐Tieftemperatur‐NMR‐Spektroskopie 20. Demnach bildet LiDEA in reinem THF oder Oxetan eine dimere Struktur aus.…”

Section: Methodsunclassified

Aufklärung der donorbasenfreien Aggregation von Lithiumdiisopropylamid in Kohlenwasserstoffen mithilfe einer DOSY‐Methode

Neufeld

John

2015

Angewandte Chemie

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Lithiumdiisopropylamid (LDA) ist ein überaus wichtiges Reagens und nimmt vor allem in der organischen Synthesechemie eine Schlüsselrolle bei einer Vielzahl von Deprotonierungsreaktionen ein. Trotzdem ist seine Aggregation, und damit die Gestalt der reaktiven Spezies in nichtdonierenden Lösungsmitteln, bislang noch ungeklärt. Hier lösen wir dieses Problem durch eine neu entwickelte DOSY‐NMR‐Methode. Sie beruht auf externen Kalibrierungskurven mit normalisierten Diffusionskoeffizienten und ist vielfältig einsetzbar.

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“…Use of 6 Li-6 Li EXSY in organolithiumc hemistry is quite detailed with numerouse xamples in the literature. [211] Scheme39. Photochemical mechanocycle in 124;rotational on-off switch 125.…”

Section: Ring Opening/closurementioning

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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NMR Spectroscopic Studies of Lithium Diethylamide: Insights into Ring Laddering

Cited by 46 publications

References 17 publications

The Donor‐Base‐Free Aggregation of Lithium Diisopropyl Amide in Hydrocarbons Revealed by a DOSY Method

The Donor‐Base‐Free Aggregation of Lithium Diisopropyl Amide in Hydrocarbons Revealed by a DOSY Method

Aufklärung der donorbasenfreien Aggregation von Lithiumdiisopropylamid in Kohlenwasserstoffen mithilfe einer DOSY‐Methode

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

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