Mixed aggregates between acetylenic lithium compounds and lithium thiocyanate in non-aqueous solutions

Góralski, Paweł; Legoff, D.; Chabanel, Martial

doi:10.1016/0022-328x(93)83307-h

Cited by 14 publications

(15 citation statements)

References 27 publications

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“…Despite scattered reports of solution structural studies of lithium enolates and related O-lithiated species, − none of the methods manifested the right combination of reliability and generality to characterize a variety of lithium enolates in a range of solvents and temperatures. We turned to the method of continuous variation (MCV) − and a strategy founded on studies by Weingarten, Chabanel, Maddaluno, Gunther, and Gagne in which the aggregation number ( n ) of enolates A n and B n can be extracted from characteristic ensembles (eq ). Using 6 Li NMR spectroscopy with the aid of parametric fitting, we have characterized more than 100 lithium enolate–solvent combinations to date. , normalA n + normalB n → normalA n + normalA n − 1 normalB 1 + normalA n − normal2 normalB 2 + ... + normalB italicn …”

Section: Introductionmentioning

confidence: 99%

Structure Determination Using the Method of Continuous Variation: Lithium Phenolates Solvated by Protic and Dipolar Aprotic Ligands

Tomasevich

Collum

2013

J. Org. Chem.

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The method of continuous variation (MCV) in conjunction with 6Li NMR spectroscopy was used to characterize four lithium phenolates solvated by a range of solvents including N,N,N′,N′-tetramethylethylenediamine, Et2O, pyridine, protic amines, alcohols, and highly dipolar aprotic solvents. Dimers, trimers, and tetramers were observed, depending on the precise lithium phenolate-solvent combinations. Competition experiments (solvent swaps) provide insights into relative solvation energies propensities toward mixed solvation.

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Section: Introductionmentioning

confidence: 99%

Structure Determination Using the Method of Continuous Variation: Lithium Phenolates Solvated by Protic and Dipolar Aprotic Ligands

Tomasevich

Collum

2013

J. Org. Chem.

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“…The strategy finds its origins in studies by Chabanel,12 Gagne,13 Günther,14 and others 15. We have now extended these studies to include a broad range of lithium phenolates (ArOLi) solvated by two commonly used ethereal solvents, tetrahydrofuran (THF) and 1,2-dimethoxyethane (DME).…”

Section: Introductionmentioning

confidence: 99%

Lithium Phenolates Solvated by Tetrahydrofuran and 1,2-Dimethoxyethane: Structure Determination Using the Method of Continuous Variation

et al. 2009

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The method of continuous variation in conjunction with 6 Li NMR spectroscopy was used to characterize lithium phenolates solvated by tetrahydrofuran and 1,2-dimethoxyethane. The strategy relies on the formation of ensembles of homo-and heteroaggregated phenolates. The symmetries and concentration dependencies of the heteroaggregates attest to the aggregation numbers of the homoaggregates. The structurally diverse phenols afford substrate-and solvent-dependent combinations of lithium phenolate monomers, dimers, trimers, tetramers, and pentamers. We discuss the refinement of protocols for characterizing O-lithiated species. Computational studies examine further the substituent and solvent dependencies of aggregation.

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“…The effect of lithium salts on aggregate structures has also been studied . The groups of Collum, Hilmersson, Thomas, van Koten, Klumpp, Chabanel, and Duhamel have all independently carried out extensive studies on the solution structure and stereochemistry of mixed aggregates. It is well-established that mixed aggregates containing organolithium starting materials and lithium-containing products can cause marked dependencies of reactivities and selectivities on the organolithium/substrate ratios. 1c, The X-ray structure and reactivity of a mixed aggregate containing commercially available alkyllithiums and a chiral lithium amide derived from N -isopropyl- O -methyl valinol, as well as the solution structure of the lithium enolate of 3-pentanone and the same chiral lithium amide, were also investigated .…”

Section: Introductionmentioning

confidence: 99%

On the Mechanism of THF Catalyzed Vinylic Lithiation of Allylamine Derivatives: Structural Studies Using 2-D and Diffusion-Ordered NMR Spectroscopy

2005

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N-Lithio-N-(trialkylsilyl)allylamines can be deprotonated in the presence of ethereal solvents exclusively at the cis-vinylic position to yield 3,N-dilithio-N-(trialkylsilyl)allylamines under mild conditions. Low temperature (1)H and (7)Li NMR ((1)H NOESY, TOCSY, (1)H/(7)Li HSQC, and DO-NMR) studies on the solution structure of 3,N-dilithio-N-(tert-butyldimethylsilyl)allylamine identified three major aggregates in THF (monomer, dimer and tetramer), but the aggregate structures failed to explain the solvent dependence and regiochemical outcome of the reaction. Low temperature (1)H NMR (NOESY, TOCSY, DO-NMR) studies on the solution structure of N-lithio-N-(tert-butyldimethylsilyl)allylamine in the presence of nBuLi identified amide/nBuLi mixed aggregates in both the ethereal solvent THF (1:1 dimer) and the hydrocarbon solvent toluene (1:3 tetramer). Addition of 2 equiv of THF to toluene solutions induces the formation of the same THF solvated 1:1 dimer as observed in neat THF. NMR evidence suggests that in THF the mixed aggregate has close contact between the olefin and the beta-CH(2) of nBuLi, while in the absence of THF, the allyl chain appears to be pointed away from the nearest nBuLi residues.

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Mixed aggregates between acetylenic lithium compounds and lithium thiocyanate in non-aqueous solutions

Cited by 14 publications

References 27 publications

Structure Determination Using the Method of Continuous Variation: Lithium Phenolates Solvated by Protic and Dipolar Aprotic Ligands

Structure Determination Using the Method of Continuous Variation: Lithium Phenolates Solvated by Protic and Dipolar Aprotic Ligands

Lithium Phenolates Solvated by Tetrahydrofuran and 1,2-Dimethoxyethane: Structure Determination Using the Method of Continuous Variation

On the Mechanism of THF Catalyzed Vinylic Lithiation of Allylamine Derivatives: Structural Studies Using 2-D and Diffusion-Ordered NMR Spectroscopy

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