Other Organosilanes

Trimethylsilyldiazomethane, 327 Silyl substituted arenes Bis(trimethylsilyl)acetylene, 97 Chromium carbene complexes, 82 Titanium(IV) chloride-Diethylalu-minum chloride, 309 Other organosilanes Osmium tetroxide-Trimethylamine N-oxide-Pyridine, 223 Tributyltin chloride, 315 Di- x-carbonylhexacarbonyldicobalt, 99 Trimethylsilyl trifluoromethanesul-fonate, 329... 

In this part, we wish to focus on the study of two types of silanes. Aminoorganosilanes are special members of the alkoxysilanes group. They carry the catalyzing amine function, required for chemical bonding with the silica surface, inside the molecule. This makes them more reactive than other organosilanes and reduces the complexity of the liquid phase reaction system to be studied. Only three components, silica, silane and solvent, are present. Furthermore there is a large interest in the reaction mechanism of silica gel with APTS, since this aminosilane is the most widely used compound of the organosilane family. 

In the discussion of the loading and curing step, we have focused on the conformation of the silicon side of the aminosilane molecules. Siloxane bond formation and effect of hydrolysis of the alkoxy groups have been characterized clearly. The special reactivity of aminosilanes, compared to other organosilanes, however, is due to the presence of the amino group inside the molecule. The inter- and intramolecular interactions of this group cause special stability and reactivity according to the conditions used. Therefore we will now focus on this side of the bifunctional molecule. 

The compound can be a very useful intermediate for the production of other organosilanes, for example, l,l-bis(silyl)ethenes as well as the previously mentioned exocyclic siloxane (P. Pawluc, Y. Itami, B. Marciniec, unpublished results). 

APS is known for its stability in basic solutions (10). The amine functionality facilitates the coupling of other desired molecules to a particle. For these reasons, this alkoxide was chosen to coat the surface of the Stober silica spheres. A simple procedure was followed, first described by Philipse and Vrij (4), who used other coupling agents. Badley et al. (11) also described the coupling of APS and other organosilanes to silica. 

Pentacoordinated silicate TASF, one of the best activators of organosilicon compounds in the Pd-catalyzed cross-coupUng reaction as we have seen, is found to be involved in the coupling reaction with aryl hahdes in the absence of other organosilanes to give methylated arenes (Scheme 1A)S Recently, DeShong and co-workers also reported that tetrabutylammonium triphenyldifluorosilicate, another pentacoordinated silicate, is applicable for the phenylation of allyl benzoates and aryl haUdes in the presence of a palladium catalyst. 

The effect of other organosilanes on deteriorated limestone was investigated. Particular attention was paid to the depth of penetration, effects on color, and the degree of consohdation. A solution of acryhc silane in methyltrimethoxysilane was found to be the most suitable consolidants for use on limestone (Bradley, 1987). It was also shown that organosilanes do not encapsulate salt in stone and that soluble salts could be removed by a poulticing technique following consolidation. 

Fukuzumi, S., Fujita, M., Otera, J., and Fujita, Y, Electron-transfer oxidation of ketene silyl acetals and other organosilanes. The mechanistic insight into Lewis acid mediated electron transfer, /. Am. Chem. Soc., 114, 10271, 1992. 

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