Silylation methods

It is observed that the synthesis of various polymers by the silylated method is superior to the conventional diamine, diphenol, or dithiol route particularly with respect to higher inherent viscosity or molecular weight of the resulting polymers. 

The strategy of the silylated method has several advantages over the condensation of nonsilylated monomers as shown below ... 

The silyl method does not liberate water, like certain conventional methods and, thus, avoids... 

The purpose of the experiment is to illustrate the application of derivatisation in the analysis of sugar and related substances by gas-liquid chromatography. The silylation method described is an almost universal derivatisation procedure for carbohydrate analysis by GC.79... 

The goal for the future is to set and optimize on-line silylation methods with improved silylation efficiency. As silylated derivatives are expected to be more volatile and stable, detection should be enhanced making this method of great potential interest in the cultural heritage field where tiny amounts of sample are available. 

Many manufacturers sell the same types of stationary phase materials,6 but the most popular stationary phase materials, e.g. octadecyl-bonded silica gels, from different sources, even from the same manufacturer, often demonstrate different retention capacities and selectivities. Such differences are due to the aggressive reactivity of the silylation method and the different bonding reactions that are used, as described earlier. 

To a mixture of 30 g of zinc powder (Merck, analytical grade) and 30 ml of absolute ethanol is added 3.5 ml of 1.2-dibromoethane. The mixture is heated until an exothermic reaction (evolution of ethene and temporary reflux) starts. The activation is completed by heating the mixture for an additional 10 min under reflux. After cooling to about 50 C, the trimethylsilylated diyne (0.05 mol, see Chap. VI for silylation methods) is added in one portion. The introduction of N2 is started and the mixture is heated for 30 min under reflux. After cooling to room temperature, the work-up is carried out in a way similar to that in exp. 2 (no aqueous ammonia is nsed). Z-CjH- CI CHC CSiMe, b.p. 75 020 mmHg, njy(20 ) 1.4592, is obtained in a high yield. 

The dehydrogenative double silylation method is extended to the synthesis of fused cyclic polycarbosilanes by the condensation of various diynes with l,2,4,5-tetrakis(dimethylsilyl)benzene.62 Polymeric compounds are formed with elimination of H2 [Eq. (20)]. 

The mechanism of the /V6-acyladeninc and silylating method for the ribosylation of adenine has been determined.131 The kinetic product formed by ribosylation at N(l) has been isolated. The reaction occurs here because the N(7) position is sterically... 

The great breakthrough for silylation methods was its great analytical applicability. It could be shown that silyl derivatives258 of alcohols, phenols, carboxylic acids (incl. fatty acids), amino acids, amines and carbohydrates are useful tools for analyzing mixtures of several unknown compounds via GLC by means of their retention time251, 258. ... 

The synthesis of pteridine nucleosides from pteridones can be considered as an electrophilic attack on a ring N-atom forming an 0,iV-acetal. A large number of N-l, N-3, and N-8 substituted ribo-, 2 -deoxyribo, arabino, xylo-, and gluconucleosides have been synthesized and described silyl-method based on the Hilbert-Johnson-Birkofer reaction. Lumazine (3) reacts with hexamethyldisilazane to 2,4-bis-trimethylsilyloxypteridine (85), which condenses with l-0-acetyl-2,3,5-tri-0-benzoyl-/ -i>ribo-furanose (86) under SnCl4, BF3 or trimethylsilyl triflate catalysis to a mixture of A(-l)-mono (87),... 

Up to now, covalent anchorages have been performed in anhydrous conditions by silylation (method a) with 3-choropropyltrimethoxysilane (CPTMS) (A1-MTS-C1 la) followed by the nucleophilic substitution of the chlorine by the amino group of (-)-ephedrine (A1-MTS-C1-E la). Alternatively, the surface coating of the MTS surface with CPTMS was achevied by a sol-gel method13 14 (method b, A1-MTS-C1 lb, A1-MTS-C1 2b) and reaction withe (-)-ephedrine led to new hybride chiral materials (Al-MTS-Cl-E lb, A1-MTS-C1-E 2b) (Scheme 2). 

We performed the synthesis of a new class of hybrid solids by grafting the coupling CPTMS agent by the sol-gel method rather than the silylation method. Supporting (-)-ephedrine on Al-MTS support with large pores by this new grafting method leads to a chiral hybrid material with a high efficiency in the enantioselective alkylation of benzaldehyde by diethylzinc.15... 

Phosphazenyl cyclophosphazenes have been synthesized by a silylation method (15, 17). 

This work showed also that MMS materials are more stable towards prolonged exposure to pure water vapour than MCM-41 materials. Finally, the proposed silicification post-synthesis procedure seems to be more promissing than the previously studied methods, including the widely used silylation method, for increasing the hydrophobicity of MCM-41 samples and stabilising the structure in the presence of water vapour. 

O-Alkylation of quinoxalines usually occurs under conditions of kinetic control, while A-alkylation proceeds under thermodynamic control. The quinoxalin-2(l H)-ones have been A-ribosylated via the silyl method under boron trifluoride-diethyl ether complex catalysis leading to the corresponding nucleosides in low to moderate yields. ... 

This silyl method has become one of the most used among the various methods for the synthesis of nucleosides. The introduction of the trimethylsilyl groups greatly enhances the solubility of the purine. Condensation of 0 ,9-bis(trimethylsilyl)hypoxanthine and 1-O-acetyl-2,3,5-tri-0-benzoyl-j8-D-ribofuranose, with tin(IV) chloride as catalyst, gives 2, 3, 5 -tri-0-ben-zoylinosine (16) in 71 /o yield after removal of the silyl groups by water treatment. ... 

These methods of synthesis of the Af-carboxyanhydrides do not involve elimination of hydrogen chloride, and thus permit retention of configuration of the ester groups. The silyl esters can be vacuum distilled without decomposition, and since (unlike their unsilylated analogues) they are readily soluble in non-polar solvents, the silylation methods constitute a suitable means of preparing this important class of compounds [1409]. 

In early 1980s, Vansant proposed the silylation method to modify zeolite channels.[46 52] The principle is to use silicanes to react with the surface hydroxygroups in H-form zeolites, and after hydrolysis the formed oxides narrow the channels so as to achieve the goal of pore-size adjustment. Figure 6.18 shows the Xe-adsorption-dynamic curves for the H-form mordenite samples silylated to various degrees. From the Figure... 

Silyl methods of penicillin and cephalosporin modification 82KGS147. Synthesis of 1-carbapenems and 1-carbapenams 83YGK62. 

Nucleosides, regioselective elongation of carbon chain of 86YGK9. Nucleosides, silyl method of their synthesis (monograph) 85MI17. Nucleosides, stereochemistry of enzymatic reactions of phosphates in ... 

Purine nucleosides, syntheses using transglycosylation 81YGK205. Pyrimidine and purine nucleosides and their analogues, silyl methods of... 

Discuss the main advantages of the organocatalytic approach to amine syn thesis, the environmental issues, and the current limitations of the hydro silylation method. 

Figure 5.27 Fluorinated PBOs synthesized by the silylation method [57].

Y. Oishi, A. Konno, J. Oravec, K. Mori, Synthesis and properties of fiuorine containing polybenzoxazole by in-situ silylation method, Photopolym. Sci. Technol. 19 (5) (2(X)6) 669-672. 

Figure 3.6. Schematic illustration of the silylation method of preparing hydrophobic silica aerogels. The precursor, solvent, catalyst (and water) are mixed and allowed to gel. The wet gel is then rinsed, soaked in a silylating agent, rinsed again and then dried at ambient pressure and elevated temperature.

Silylation Method used to make hydrophobic aerogels via post gelation derivatization with an additional silane compounds SiOx Silica aerogels SOFCs Solid oxide fuel cells... 

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