Sparteine, a ligand for magnesium in organometallics: nuclear magnetic resonance studies of exchange

Fraenkel, Gideon; Cottrell, Charles E.; Ray, J. G.; Russell, John G.

doi:10.1039/c29710000273

Cited by 24 publications

(12 citation statements)

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“…[13] Later, several experiments showed the importance of NMR line shape analysis for the investigation of the kinetic behavior of lithiated compounds. [14] In this work, we determined the epimerisation of the lithiated indenides 5 and 6 by 1 H NMR spectroscopy.…”

Section: H Nmr Spectroscopic Investigationsmentioning

confidence: 99%

Experimental and Theoretical Investigations of Lithio-Indenyl Carbamate/(−)-Sparteine and (−)-α-Isosparteine Complexes

et al. 1999

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1-Carbamoyloxy-1-lithio-indene complexes of (À)-sparteine and (À)-a-isosparteine 5/epi-5 and 6/epi-6 were prepared and found to be configurationally unstable on the macroscopic time scale. Ratios of epimers and the rates of interconversion, including some activation parameters, were determined by temperature-dependent line shape analysis in the 1 H NMR spectrum. The highest barrier for interconversion (DDH = b 25 kcal mol À1 ) was recorded for the 2-methylindenide/(À)-sparteine complexes 5 b/epi-5 b, whereas the activation energy for the epimerisation of the indenide/(À)-a-isosparteine complex 6 a/epi-6 a is too low to be recorded by this method. Trapping of the lithium compounds 5/epi-5 and 6/epi-6 proceeds with methyl iodide in an anti-S E ' process.The obtained enantiomeric ratios correlate roughly with the observed epimeric ratios in the lithium intermediates. The absolute configurations of the methylation products 7 c and 7 d have been established by chemical correlation with the known ()-(S)-3-methyl-1H-indan-1-one. The ratios correspond well to those predicted by semiempirical PM3 calculations on the relative stability of the diastereomeric complexes.

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Section: H Nmr Spectroscopic Investigationsmentioning

confidence: 99%

Experimental and Theoretical Investigations of Lithio-Indenyl Carbamate/(−)-Sparteine and (−)-α-Isosparteine Complexes

et al. 1999

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“…Early investigations on organometallic (−)-sparteine complexes concern the nucleophilic addition of lithium 7 , magnesium 12 and zinc complexes 13,14 onto carbonyl compounds, utilization in polymerization 15,16 and also NMR spectroscopic investigations 17,18 .…”

Section: General Featuresmentioning

confidence: 99%

Asymmetric Deprotonation with Alkyllithium–(−)‐Sparteine

Hoppe

Christoph

2009

Patai's Chemistry of Functional Groups

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Introduction Non‐Mesomerically Stabilized Organolithium Compounds (−)‐Sparteine‐Induced Lithiation with Formation of Benzyl‐Type Organolithiums Allyllithium–(−)‐Sparteine Complexes Lithium–(−)‐Sparteine Complexes of 2‐Alkynyl Carbamates Axial–Chiral and Planar–Chiral Lithium–(−)‐Sparteine Complexes Enantioselective Addition of Achiral Carbanionic Compounds in the Presence of (−)‐Sparteine

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“…Zeolites are crystalline aluminosilicate constituted by silica tetrahedron and alumina tetrahedron through oxygen bridges containing ordered micropores that enable shaped‐selective transformation [1–3] . Because of their high specific surface areas, high thermal and hydrothermal stability as well as strong Brønsted acidity, Zeolites have been widely used in many applications, including alkylation, [4,5] isomerization [6,7] and aromatization reactions [8,9] . According to the Structure Commission of the International Zeolite Association (IZA) (http://www.iza-online.org/ ), 255 different framework topologies with various sizes and channel connectivity exist.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Decisive Structural Parameters and Acidic Property of Zeolites for Gas‐Phase Alkylation of Benzene with Ethylene

et al. 2021

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The effects of the zeolite structure and acidic property on the activity and selectivity in gas‐phase alkylation of benzene with ethylene were investigated using TUN, IMF, *SFV and MFI with different structures and Si/Al2 ratios. The channels of TUN and IMF provide both higher selectivity to ethylation (ethylbenzene and di‐ethylbenzene) and lower xylene selectivity compared to MFI with slightly smaller pore diameter in which the pore diffusion limitations are suffered. The activity is mainly controlled by zeolite channel architecture. The higher activity and selectivity are obtained using modified TUN and modified IMF with suitable density of Brønsted acidity in a well‐defined channel structure sterically constrained for heavy by‐products. It is shown that the activity and selectivity increase with increasing pore diameter of three‐dimensional 10 ring channel structure, while the rule is not valid for *SFV.

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Sparteine, a ligand for magnesium in organometallics: nuclear magnetic resonance studies of exchange

Abstract: The existence and structure, (I), of strong sparteine R2Mg complexes, which undergo inversion, carbon-magnesium bond exchange, and magnesium ligand exchange unusually slowly, have been established by n.m.r. studies.

Cited by 24 publications

References 0 publications

Experimental and Theoretical Investigations of Lithio-Indenyl Carbamate/(−)-Sparteine and (−)-α-Isosparteine Complexes

Experimental and Theoretical Investigations of Lithio-Indenyl Carbamate/(−)-Sparteine and (−)-α-Isosparteine Complexes

Asymmetric Deprotonation with Alkyllithium–(−)‐Sparteine

Analysis of Decisive Structural Parameters and Acidic Property of Zeolites for Gas‐Phase Alkylation of Benzene with Ethylene

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