The Organosilicon-Oxygen Compounds

Cyanotriethylsilane [196]. (64%, b.p. 181-183°C) was obtained from 3,3-dimethyl-2-oxobutanoic nitrile and triethylmethoxysilane by boiling under reflux (Eq. 3.77)  

Heating (130 C) chlorotrimethylsilane with NaCN or KCN in sulfolane in the presence of CuCN gives cyanotrimethylsilane in 90% yield [197]. The current literature on cyano-, isocyanato-, isothiocyanato and azidosilanes has recently been reviewed [198, 199]. 

If an organosilicon compoimd with functional groups on the silicon atom is exposed to water or alcohol, only the silicon-carbon bonds are preserved. The other silicon bonds are converted more or less rapidly into silicon-oxygen bonds. 

A summary of the stability of silicon-oxygen bonds compared to silicon-carbon bonds is given in Chapter 1. Cyclic, straight or branched polysiloxanes, in which the elements 

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The Organosilicon-Oxygen Compounds 49 Table 3.5 Organopolysiloxanes from the hydrolysis of haloorganosilanes. 

It is well known that strong electrophiles such as carbocations are reduced by organosilicon hydrides (Eq. 1).3,70,71 On the other hand, simple mixtures of organosilicon hydrides and compounds with weakly electrophilic carbon centers such as ketones and aldehydes are normally unreactive unless the electrophilicity of the carbon center is enhanced by complexation of the carbonyl oxygen with Brpnsted acids3,70 73 or certain Lewis acids (Eq. 2).1,70,71,74,75 Using these acids, hydride transfer from the silicon center to carbon may then occur to give either alcohol-related or hydrocarbon products. 

Reduction to Alcohols. The organosilane-mediated reduction of ketones to secondary alcohols has been shown to occur under a wide variety of conditions. Only those reactions that are of high yield and of a more practical nature are mentioned here. As with aldehydes, ketones do not normally react spontaneously with organosilicon hydrides to form alcohols. The exceptional behavior of some organocobalt cluster complex carbonyl compounds was noted previously. Introduction of acids or other electrophilic species that are capable of coordination with the carbonyl oxygen enables reduction to occur by transfer of silyl hydride to the polarized carbonyl carbon (Eq. 2). This permits facile, chemoselective reduction of many ketones to alcohols. 

We propose that the carbonyl oxygen of the (+)-ethyl lactate acts as a Lewis base forming an intramolecular pentacoordinated organosilicon compound. Pentacoordination from a... 

Silicon is one of the most oxophilic elements (see Silicon Organosilicon Chemistry). Therefore, organosilicon sulfides react with certain sulfur oxygen compounds, as shown in equations (39) and (40). ... 

A substitution route to organosilicon compounds is described. In this route, the silicon-oxygen framework of the compound wanted or a framework similar to it, is made by rearrangement of the framework in a silicate or silica or is secured by obtaining a silicate in which the framework is present from an outside source. The compound wanted is made from this framework by displacement of the pendent oxygen atoms and, where needed, by additional rearrangement of it. This route opens a way to syntheses of [(CH3)2SiO] that do not entail the reduction of tetravalent silicon to elemental silicon. 

Our English word silica has a very broad connotation it includes silicon dioxide in all its crystalline, amorphous, soluble, or chemically combined forms in which the silicon atom is surrounded by four or six oxygen atoms. This definitely excludes all the organosilicon compounds made by man in which carbon atoms have been linked directly to silicon atoms—commonly referred to as silicones , which do not occur in nature. Silica is soluble enough in water to play important roles in many forms of life. It forms the skeletons of diatoms, the earliest form of life that absorbed sunlight and began to release oxygen into the atmosphere. Many plants use silica to stiffen stems and form needles on the surface for protection. 

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