18294-00-3Relevant academic research and scientific papers
THE REACTION OF THE TRIMETHYLCHLOROSILANE/MAGNESIUM REAGENT WITH gem-DIBROMOCYCLOPROPANES
Seyferth, Dietmar,Duncan, Don P.
, p. 1 - 8 (1980)
The reaction of the trimethylchlorosilane/magnesium reagent with gem-dibromocyclopropanes in tetrahydrofuran medium results in the formation of silylated cyclopropanes and/or silylated ring-opened products, depending on the substituents on the cyclopropane ring.
The γ-silicon effect. I. Solvent effects on the solvolyses of 2,2- dimethyl-3-(trimethylsilyl)propyl and 3-(aryldimethylsilyl)-2,2- dimethylpropyl p-toluenesulfonates
Nakashima, Tohru,Fujiyama, Ryoji,Fujio, Mizue,Tsuno, Yuho
, p. 741 - 750 (2007/10/03)
The solvolysis rates of 2,2-dimethyl-3-(trimethylsilyl)propyl and 3- (aryldimethylsilyl)-2,2-dimethylpropyl p-toluenesulfonates were measured in a wide variety of solvents at 45 °C. The solvent effects were analyzed by using the Winstein-Grunwald equation. The solvent effects observed did not give simple linear correlations with the 2-adamantyl Y(OTs) parameter, but showed dispersion behavior in a series of binary solvents. The m values of 0.59-.67 were remarkably lower than unity for the limiting k(c) solvolysis of 2-adamantyl p-toluenesulfonate. The deviation patterns could not be interpreted in terms of nucleophilic assistance by the solvent. The dispersion behavior with reduced m values was found to be more significant for the 3-(aryldimethylsilyl) than for the 3-(trimethylsilyl) derivatives and was compatible with the delocalization of the incipient cationic charge by participation of the Si-Cγ bond in the rate-determining step. An extended dual-parameter treatment, log (k/k(80E)) = m(c)Y(OTs) + m(Δ)Y(Δ), successfully correlated such γ-silyl assisted solvolyses. The M(Δ) values of 0.24-0.49 so obtained, where M(Δ) = 0.51 m(Δ)/(m(c) +0.51 m(Δ)), are a measure of the extent of charge delocalization, suggesting that the γ-silyl group in the percaudal interaction is more effective in delocalizing the cationic charge than the alkyl group in C-C σ-participation, but less so than σ-assisted interaction by the β-aryl group.
γ-Silyl-stabilized tertiary ions? Solvolysis of 4-(trimethylsilyl)-2-chloro-2-methylbutane
Tilley, Leon J.,Shiner Jr.
, p. 564 - 576 (2007/10/03)
Rate constant, isotope-effect, and product studies of the solvolysis of 4-(trimethylsilyl)-2-chloro-2-methylbutane, 11, and its carbon analog, 2-chloro-2,5,5-trimethylhexane, 10, in aqueous ethanol and aqueous 2,2,2-trifluoroethanol (TFE) indicate very little participation of the γ-silyl substituent. These results are in sharp contrast to earlier reports on secondary γ-silyl substituted systems, in which the back lobe of the silicon-carbon bond has been shown to overlap with the carbocation p-orbital to form a so-called 'percaudally' stabilized intermediate. While the solvolytic behaviors of 11 and 10 are nearly identical in ethanol, differences in the TFE lead to the conclusion that there is a minor amount of participation by the silyl substituent in that solvent. Interestingly, this observation lends credence to an earlier suggestion that TFE is better than ethanol at stabilizing more highly delocalized ions. Copyright
