Peculiarities in the cleavage by methyllithium of unsymmetrical disilanes

Hevesi, L.; Dehon, M.

doi:10.1016/0040-4039(94)80041-3

Cited by 2 publications

(1 citation statement)

References 6 publications

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“…Since these figures are very close to those of perfluoropoly- p -phenylene, we assign this structure to the beige solid. In a preliminary account of this work we erroneously proposed poly(dimethyl)silane as the structure of this solid material. On the basis of reported precedents it was assumed that methyllithium might have abstracted a methyl group from 1e .…”

Section: Resultsmentioning

confidence: 94%

Kinetic Control in the Cleavage of Unsymmetrical Disilanes

et al. 1997

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A series of 12 phenyl-substituted arylpentamethyldisilanes 1a-l have been synthesized in order to examine the regioselectivity of their nucleophilic Si,Si bond cleavage reactions under Still's conditions (MeLi/HMPA/0 degrees C). It has been found that the sensitivity of these reactions to the electronic effects of the substituents in the phenyl ring could be described by the Hammett-type equation log(k(A)/k(B)) = 0.4334 + 2.421(Sigmasigma); (correlation coefficient R = 0.983). The k(A)/k(B) ratio represents the relative rate of attack at silicon atom A (linked to the aryl ring) or at silicon atom B (away from the aryl ring) of the unsymmetrical disilanes. Thus, the present investigation shows that the earlier belief according to which the nucleophilic cleavage of unsymmetrical disilanes always produces the more stable silyl anionic species (thermodynamic control) should be abandoned, or at least seriously amended: kinetic factors appear to exert a primary influence on the regioselectivity of such reactions. Since the two major kinetic factors (i.e., electrophilic character of and steric hindrance at a given silicon atom) have opposite effects on the orientation of the reaction, it may happen that kinetic and thermodynamic control lead to the same result. For some of the unsymmetrical disilanes studied, the major reaction path was not the Si,Si bond cleavage; instead, Si-aryl bond breaking occurred, producing the corresponding aryl anions.

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Section: Resultsmentioning

confidence: 94%

Kinetic Control in the Cleavage of Unsymmetrical Disilanes

et al. 1997

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Toward selective functionalisation of oligosilanes: borane-catalysed dehydrogenative coupling of silanes with thiols

et al. 2008

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Among established methods for transforming Si-H bonds, carbonyl hydrosilylation and heterodehydrogenative coupling with alcohols catalysed by B(C6F5)3 are shown to provide exceptionally clean routes to the derivatisation of tetra-substituted disilanes such as [Ph2SiH]2, giving no products resulting from Si-Si bond cleavage. Even higher activity is observed for the borane-catalysed dehydrogenative coupling of silanes with alkyl- and arylthiols, the first examples of such Si-S bond formation in the absence of a transition metal catalyst. Clean, quantitative syntheses of a range of thiosilanes are reported, and the lability of the Si-S linkage toward subsequent alcoholysis is investigated. The crystal structure of 2,3-disila-2,2,3,3-tetramethyl-1,4-benzodioxane is presented.

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Peculiarities in the cleavage by methyllithium of unsymmetrical disilanes

Cited by 2 publications

References 6 publications

Kinetic Control in the Cleavage of Unsymmetrical Disilanes

Kinetic Control in the Cleavage of Unsymmetrical Disilanes

Toward selective functionalisation of oligosilanes: borane-catalysed dehydrogenative coupling of silanes with thiols

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