1851-00-9Relevant academic research and scientific papers
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.
Alkyl-4-silyl-phenols and esters thereof as antiatherosclerotic agents
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, (2008/06/13)
This invention relates to compounds of the formula STR1 wherein R1 and R6 are each independently C1 -C6 alkyl; R2, R3 and R4 are each independently hydrogen or C1 -C6 alkyl; R is hydrogen or --C(O)--(CH2)m --Q wherein Q is hydrogen or --COOH and m is an integer 1, 2, 3 or 4; Z is a thio, oxy or methylene group; A is a C1 -C4 alkylene group; R5 and R7 are each independently a C1 -C6 alkyl or --(CH2)n --(Ar) wherein n is an integer 0, 1, 2 or 3; and Ar is phenyl or naphthyl unsubstituted or substituted with one to three substituents selected from the group consisting of hydroxy, methoxy, ethoxy, halogen, trifluoromethyl, C1 -C6 alkyl, or --NR8 R9, wherein R8 and R9 are each independently hydrogen or C1 -C6 alkyl; with the proviso that when R2 and at least one of R5 or R7 is C1 -C6 alkyl, and Ar is not substituted with trifluoromethyl or --NR8 R9, then R is --C(O)--(CH2)m --Q; or a pharmaceutically acceptable salt thereof; useful for the treatment of atherosclerosis and chronic inflammatory disorders; for inhibiting cytokine-induced expression of VCAM-1 and/or ICAM-1; for inhibiting the peroxidation of LDL lipid; for lowering plasma cholesterol; and as antioxidant chemical additives useful for preventing oxidative deterioration in organic materials.
