Zum Mechanismus der Spaltung von Diäthyläther mit Alkyllithium‐Verbindungen: Unterschiedliche Zersetzungsmechanismen bei α‐ und ß‐deuteriertem Diäthyläther

Maercker, Adalbert; Demuth, Wolfgang

doi:10.1002/ange.19730850210

Cited by 17 publications

(3 citation statements)

References 7 publications

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“…In the case of diethyl ether all three mechanisms would lead to ethene and lithium ethoxide (eq ). Deuteration experiments have shown that β-elimination is the dominating reaction pathway, whereas THF is α-deprotonated and decomposes to ethene and the lithium enolate of acetaldehyde. , The metalation of 2,6-Me 2 -4-ClC 6 H 2 OH with tert -butyllithium in the presence of dioxane led to cleavage of 1,4-dioxane with formation of LiO(CH 2 ) 2 OCHCH 2 , which was crystallized as hexanuclear [(Aryl-O) 2 (R-O) 4 Li 6 (diox)] (Aryl = 2,6-Me 2 -4-ClC 6 H 2 ; R = CH 2 CH 2 OCHCH 2 ) RLi 1.5pt + 1.5pt CH 3 CH 2 normalO CH 2 CH 3 → RH 1.5pt + 1.5pt normalH 2 C CH 2 1.5pt + 1.5pt Li normalO CH 2 CH 3 …”

Section: Resultsmentioning

confidence: 99%

1,4-Dioxane Adducts of Grignard Reagents: Synthesis, Ether Fragmentation Reactions, and Structural Diversity of Grignard Reagent/1,4-Dioxane Complexes

et al. 2009

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The 1,4-dioxane precipitation method was employed to obtain solutions of R 2 Mg from Grignard reagents via precipitation of polymeric magnesium dihalides as dioxane adducts. The addition of a slight excess of dioxane resulted in partial cleavage of the initially formed [( μ-diox)MgR 2 ] ¥ polymer into smaller fragments of the type [(diox) nþ1 (MgR 2 ) n ]. In addition to the polymeric compounds(2) can be obtained from such solutions. In the system MesMgBr/1,4dioxane the compounds [( μ-diox)MgBr 2 ] ¥ and [( μ-diox)Mg(Mes) 2 ] ¥ are both sparingly soluble, offering the opportunity to remove most of these compounds from the reaction mixture and leaving the products of ether cleavage reactions as the major species in solution. Using this procedure, the new ether degradation products [(diox)Mg(Mes)(μ-OEt)] 2 (3) and [(EtOCH(Me)CH(Me)OEt)Mg-(Mes) 2 ] (4) were isolated. Excess dioxane yields mononuclear [(diox) 2 Mg(Mes) 2 ] (5). Exchange of the thf coligands in closely related [(thf) 2 Mg(Mes) 2 ] for other Lewis bases such as 2,2 0 -bipyridine (bpy) and 2,4,6-trimethylphenyl (Mes) anions allowed the preparation of [(bpy)Mg(Mes) 2 ] (6) and [(thf) 4 -Li] þ [Mg(Mes) 3 ] -(7). Molecular structures of all new compounds 2-7 are reported.

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Section: Resultsmentioning

confidence: 99%

1,4-Dioxane Adducts of Grignard Reagents: Synthesis, Ether Fragmentation Reactions, and Structural Diversity of Grignard Reagent/1,4-Dioxane Complexes

et al. 2009

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“…This reaction is well known, but only little investigated. [48] A much better understood reaction is the direct a-lithiation of tertiary methylamines used as nitrogen ligands, amongst them TMEDA, PMDTA and (R,R)-TMCDA (5).…”

Section: Structure-reactivity Relationship and The Reactivity Towardsmentioning

confidence: 99%

Structure Formation Principles and Reactivity of Organolithium Compounds

Gessner

Däschlein

Strohmann

2009

Chemistry A European J

241

111

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The structure-reactivity relationship is an important feature of organolithium compounds. The knowledge of the structure of reactive species is crucial for the elucidation of reaction mechanisms and the understanding of observed selectivities. This concept article gives an overview over the structural principles of lithium organics and their Lewis base coordinated complexes in the solid state. The transition from the oligomeric parent structures to smaller adducts, such as dimers and monomers, as well as special degrees of aggregation is presented. Besides the commonly used alkyllithium compounds, a short overview over the structural principles of the higher homologous silyllithium compounds is given. Moreover, the structure-reactivity relationship is depicted by means of the reactivity of the Lewis bases towards intramolecular decomposition reactions with the organolithium compound. Selected examples confirm the importance of structure elucidation for the understanding of mechanistic pathways and selectivities.

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“…Unfortunately, decreased solubility of lithiated compounds at very low temperatures in nonpolar solvents often hinders further decreases in the temperature. Changing to more polar solvents is in most cases impossible, as the lithiated compound may react with the solvent (e.g., ether cleavage), [18,19] or in general, different structure motives like solvent-separated ion pairs (SSIP) oc-cur. In addition, selective synthesis, controllable reactivity and stability for several days, at least, are further desired features.…”

Section: Introductionmentioning

confidence: 99%

Structural Studies on (–)‐Sparteine‐Coordinated Lithiosilanes

Däschlein

Strohmann

2008

Eur J Inorg Chem

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A series of (–)‐sparteine‐coordinated lithiosilanes was synthesised and studied by X‐ray structural analysis. All lithiosilanes are monomers in the solid state; yet, increasing sizes of substituents at silicon significantly influences their molecular structures. Due to the given stereochemistry of the dinitrogen (–)‐sparteine ligand, all systems possess stereoinformation. NMR spectroscopic studies were used to obtain deeper insight into the structures of these compounds in solution. Observed coupling between the silicon and lithium atoms as well as the presence of only one signal for each atom in the NMR spectra are indicative of monomeric structures of the lithiosilanes in solution. Additional quantum chemical calculations on one of the examined (–)‐sparteine‐coordinated systems provided very small energy differences between the diastereomers.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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Zum Mechanismus der Spaltung von Diäthyläther mit Alkyllithium‐Verbindungen: Unterschiedliche Zersetzungsmechanismen bei α‐ und ß‐deuteriertem Diäthyläther

Cited by 17 publications

References 7 publications

1,4-Dioxane Adducts of Grignard Reagents: Synthesis, Ether Fragmentation Reactions, and Structural Diversity of Grignard Reagent/1,4-Dioxane Complexes

1,4-Dioxane Adducts of Grignard Reagents: Synthesis, Ether Fragmentation Reactions, and Structural Diversity of Grignard Reagent/1,4-Dioxane Complexes

Structure Formation Principles and Reactivity of Organolithium Compounds

Structural Studies on (–)‐Sparteine‐Coordinated Lithiosilanes

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