Silanes trimethoxysilanes

In [276] the properties of kaolin-filled polyethylenes were investigated. The filler was pre-treated with silanes of two kinds, vinyl triethoxysilane (VTES) (I) and gamma-methacryloxypropyl trimethoxysilane (II). The results are presented in Table. 9. 

Allylic trimethoxysilanes are activated by a catalytic combination of CuCl and TBAF.118 The mechanism of this reaction is not entirely clear, but it seems to involve fluoride activation of the silane. These reactions are stereoconvergent for the isomeric 2-butenyl silanes, indicating that reaction occurs through an acyclic TS. 

Covalent immobilization methods of NAs to a silica surface require its chemical modification. Functionally inert surface silanols (Si - OH) need to be transformed into reactive species to which the NAs can be attached irreversibly. To date, the main method for the attachment of biological moieties to silica surfaces has involved substrate reaction with organofunctional silanes of the general structure (RO)3Si(CH2)X, followed by the covalent attachment of the biological molecule to the newly introduced fimctional group on the surface [31,32]. Examples of organofimctional silanes used this way include (3-glycidoxypropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane,... 

The hydrotalcite-1ike material catalyzes organic reactions in which the interlayer Cl" anions play the role of catalyst. The material catalyzed the halide-exchange reactions between benzyl chloride with butyl bromide or butyl iodide in toluene. The hydrota1cite-1ike material also catalyzes a disproportionation of trimethoxysilane to give silane and tetramethoxysilane. 

Experiments like those described above have been performed to evaluate sodium ion barrier properties of Hitachi PIQ and DuPont PI 2540 polyimide films. Also included in the comparison were silicon nitride coatings plasma deposited in both tensile and compressive stress modes. The structure of the samples is illustrated in Figure 9. N-type, (111) oriented silicon substrates were cleaned and oxidized in dry oxygen ambient at 1100°C to form a 1060 A Si02 film. Wafers intended for polyimide characterization were coated with an organic silane film (gamma glycidal amino propyl trimethoxysilane) to promote adhesion of the polyimide to the oxide surface. The polyimide resins were spun onto the wafers at speeds to produce final... 

Shibata and co-workers have reported an effective protocol for the cyclization/hydrosilylation of functionalized eneallenes catalyzed by mononuclear rhodium carbonyl complexes.For example, reaction of tosylamide 13 (X = NTs, R = Me) with triethoxysilane catalyzed by Rh(acac)(GO)2 in toluene at 60 °G gave protected pyrrolidine 14 in 82% yield with >20 1 diastereoselectivity and with exclusive delivery of the silane to the G=G bond of the eneallene (Equation (10)). Whereas trimethoxysilane gave results comparable to those obtained with triethoxysilane, employment of dimethylphenylsilane or a trialkylsilane led to significantly diminished yields of 14. Although effective rhodium-catalyzed cyclization/hydrosilylation was restricted to eneallenes that possessed terminal disubstitution of the allene moiety, the protocol tolerated both alkyl and aryl substitution on the terminal alkyne carbon atom and was applicable to the synthesis of cyclopentanes, pyrrolidines, and tetrahydrofurans (Equation (10)). 

We have found that the ratios of silanes used can be varied within wide limits, and more than two silanes can be used. For example, TEOS, y-aminopropyl trimethoxysilane (AMP-silane) and phenyl trimethoxysilane can be co-polymerised to give a material containing both amino groups and phenyl groups. Some representative examples of materials synthesised by this procedure are detailed in Tables 1 and 2... 

The outcome of the reaction is affected by hydrosilane, CO pressure, and choice of catalyst. The hydrosilane substituents influence the selectivity of the reaction, i.e., relative ratio of silylformylation to hydrosilylation. For example, silanes with phenyl substituents, such as Me2PhSiH, Ph2MeSiH, and Ph3SiH, lead exclusively to silylformylation products, but at least 80% of the product derived from trimethoxysilane is due to hydrosilylation. Trialkylsilanes generally give 40 60 mixtures of hydrosilylation and silylformylation products. The carbon monoxide pressure under which the reaction... 

Standard solutions of methanol were prepared in distilled water using GR methanol (EM Science, 99.8%). Trimethylmonomethoxysilane (TMMS), methyl-trimethoxysilane (MTMS), and ethyltrimethoxysilane (ETMS) were obtained from Petrarch Systems Inc., Bristol, PA. All the silanes were distilled under vacuum prior to use and stored at 5°C. A liquid-phase, 3C-NMR spectrum of each silane showed no presence of methanol, which indicates little or no hydrolysis of the methoxy groups. 

The hydrolysis of aminopropyltrialkoxysilanes was recently studied by Kang et al. [12] using NMR spectroscopy. The rates of hydrolysis were shown to be dependent on the water and silane concentrations in solution as well as on the chemical structure. Under comparable conditions, the trimethoxysilane hydrolyzed much more rapidly than the triethoxy compound. 

As expected, the polymeric dimethoxysilane PS076.5 confers better moisture resistance than the polymeric trimethoxysilane PS076 (Fig. 9). However, the improvement obtained with APS, the monomeric silane, is somewhat better. This... 

Reduction The asymmetric reduction of a series of aryl alkyl ketones with quaternary ammonium fluorides and silanes was reported by Drew and Lawrence [55]. In these reactions, the best catalysts (e.g., 6f) were from the qui ni ne/quinidine series in fact, a fluoride salt prepared from cinchonine gave no induction. The use of trimethoxysilane resulted in faster rates but lower enantioselectivites when compared with tris(trimethoxy)silane. It is interesting that, with the... 

The hydrosilylation of carbonyl compounds with polymethylhydrosiloxane (PMHS) or other alkoxysilanes can be catalyzed by TBAF, at high efficiency [9]. The asymmetric version of this process has been developed by Lawrence and coworkers using chiral ammonium fluoride 7c prepared via the method of Shioiri [10]. The reduction of acetophenone was performed with trimethoxysilane (1.5 equiv.) and 7c (10 mol%) in THF at room temperature, yielding phenethyl alcohol quantitatively with 51% ee (R) (Scheme 4.6). A slightly higher enantioselectivity was observed in the reduction of propiophenone. When tris(trimethylsiloxy)silane was used as a hydride source, the enantioselectivity was increased, though a pro-... 

Chemisorption. A key step in the development of a successful membrane modified FET is the adherence and longevity of the membrane and the success of the encapsulation procedure. Sudholter et al (35) have proposed a method for the attachment of the ion selective membrane to a silylated SiC>2 gate oxide. An organofunctional silane, for example methacryloxypropyl trimethoxysilane, forms a bond between the surface and a photocrosslinkable polymer (eg polybutadiene). The ionophore would be directly bound to the polymer backbone, thus eliminating the need for plasticiser. Without any further modification with ionophore the membrane is sensitive to pH and shows a long life time (some months). Similar approaches have also been proposed by other workers, eg (36)... 

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