Silane results

In contrast to the nickel-organozinc catalyst system, which induces /3,/3-coupling of bis(enones), the use of cobalt(ll) catalysts in the presence of silane results in a,/3-coupling to provide products of reductive Michael cyclization.48,48a,48b Both five- and six-membered ring products 26b and 25d are formed in good yields and with complete diastereoselection. The choice of silane is critical. Whereas exposure of bis(enone) 25a to Co(dpm)2... 

Metallated difluoroenol carbamate chemistry can be used as a flexible entry point to difluoroenolates and to difluoroenoxy silanes (Sect. 3.3, Eq. 42). Trapping the difluoroenolates with non-enolisable aldehydes affords aldol products (with low stereoselectivity and in variable yield) (Eq. 128) [332], while difluoroenoxy silanes result when the enolate is intercepted with a chlorotrialkyl silane [333]. 

The recorded bond strengths clearly show that MAMS and ECMS were totally ineffective as adhesion promoters on glass. MPS, APES and AAMS were all effective and their use resulted in a marked improvement in the bond strength of both adhesives. All three silanes resulted in a change of the site or mode of failure, the locus of failure transferring from the glass surface to the aluminium test specimen or within the adhesive. 

Table 15 shows the compressive data for anhydride cured foams containing 5 wt% of several silanes. In all cases the use of the silanes resulted in an increase in compressive strength and strain to failure, although in almost every case this was accompanied by a fall in the compressive modulus, i.e. the foams were less stiff . 

Some credence must be attached to the view that the wet strength of an oxide layer is improved by silanes in the light of the findings reported by Walker [13]. XPS data showed that water immersion in the absence of silanes resulted in the presence of aluminium on both surfaces of a broken joint. Aluminium was neither detected in the presence of a silane, nor on joints broken without exposure to water. The presence of aluminium on both fracture surfaces indicates either a cohesive failure within an oxide layer, or detachment of the oxide layer, the former seems more likely. 

The hypothetical replacement of hydrogen by hydroxyl in silane, or in an alkyl or aiyl silane, results in a series of silanols, formally analogous with the alcohol, vicinal glycol, hydrated carboxylic acid, and ortho-carbonic acid series of carbon chemistry. The silanols are in many ways both the most interesting and the most important silicone intermediates. 

A number of acyl silanes have been isolated from the photosensitized oxygenation of silyl diazo compounds using meso-tetraphenylporphine (TPP) as the sensitizer (Scheme 15)15. This synthesis is most useful for aromatic acyl silanes and the yellow u-carboxyacyl silanes, but it is not of general applicability, isolation difficulties commonly being encountered in the synthesis of aliphatic and other acyl silanes, resulting in poor overall yields. 

Complications in these reactions between an alkali-organosilico compound and a halogenated silane result from a frequent symmetrization of the disilanes formed, caused by a metal exchange. Kelling375 found the following unexpected products ... 

The formation of various cyclic silanes results from an intramolecular tp3 SiLi elimination ... 

Silane and diborane show a high reactivity towards zeolitic hydroxyl groups. Treatment of H-zeolites with silane results in a permanent change of their structural properties. 

During our investigation of the reactivity of the 10 % Pd/C catalyst, we found that le reacts with itself forming dimeric compounds (Scheme 32). This problem was solved by slow addition of the silane to a mixture of the alcohol and catalyst in the second alcoholysis step. We proposed that the silyl ether is activated by the catalyst and intramolecular dimerization occurs on the surface of the catalyst (Figure 8). This reaction is faster than the usual intermolecular reaction of the incoming alcohol with the silane, resulting in the dimeric products. 

Frye, C. L., G. E. Vogel, and J. A. Hall Triptych-siloxazolidines Penta-coordinate Bridgehead Silanes resulting from transannular interaction of Nitrogen and Silicon. J. Amer. chem. Soc. 83, 996—997 (1961). 

For the detection of ionic species other than protons, it is necessary to introduce receptor molecules which can selectively bind guest species on top of the gate of the ISFET. Direct attachment of ion-selective moieties to the surface, e.g. by silylation with (3-cyanopropyl)dimethyl(dimethylamino)silane resulted in some sensitivity towards Ag+ ions (20 mV decade" ), but the sensor was still sensitive towards protons (15 mV decade" ) [10]. Chemical grafting with ammonium phosphonate (1-3) and phosphate sites (4) (Figure 2) or with phthalocyanine-based ionophores bearing crown-ether moieties resulted in a sensitivity towards alkaline (earth) ions, but the pH dependency remained [11,12]. 

Tributyltin hydride has been used as a hydride donor to produce stabilized car-benium ions in 2-oxonia Cope rearrangement use of the less nucleophilic triethyl-silane resulted in poor chemical and optical yields (Scheme 12.129) [232]. 

In this step, the surface hydroxyl groups on the slide react with the ethoxy groups on the mercaptopropyltriethoxy silane resulting in a thiol-derivatized slide (22, 23)... 

During this process, the hydroxyl groups on the surface of the slide react with the ethoxy groups of aminopropyl triethoxy silane resulting in an amine-derivatized slide (24). 

Intramolecular coupling can lead to the formation of a C-Si bond, so that cyclic silanes result. Thus, l,5-dichloro-3-[2-(trichlorosilyl)ethyl]-pentane (349) with Mg in ether yield both l,l-dichloro-4-ethyl-l-silacyclohexane (-dihydrosiline) (350) (yield 21%) and 1-chloro-l-silabicyclo[2.2.2]-octane (351) (yield 64%) (equation 159)183. 

Up to now only the reaction of lithiated diethylaminoallene with trimethylchloro-silane, resulting in (exclusively) Me3SiCH2C=C—NEt2, has been reported [104]. The metallation of the easily accessible 2-alkynylamines [6] can be brought about with BuLi /-BuOK in THF. Under suitable conditions free allenic amines can be obtained in a reasonable state of purity if the protonation is carried out with the lithium compounds (obtained from 2-alkynylamines and BuLi in THF, see Ref. [219]), the ratio of allenic and acetylenic amine is less favourable [9]. 

Silicone Polymers - High energy UV irradiation of poly(phenylmethyl silane) results in end chain scission at the Si-Si bonds while alkoxypolysilanes show an increase in molecular weight. Two photon excitation of poly(dihex-ylsilylene) gives controlled oligomer formation containing ten Si atoms each. ... 

Silanes offer tremendous advantages for virtually all market segments involving polymer-filler interactions. Surface modification of fillers with silanes results in such attractive prospects as... 

As an example of the effect of methacryloxysilane in a filled UP system [34], a formulation containing 63% quartz flour was selected. Pretreatment of the filler with 1 % silane results in 38% lower viscosity versus the non-silane-containing composite. 

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