Oxygenation tris silane

Derivatives (3) of DL-thrcose and 4-deoxy-DL-threose are available from C-1 oxygenated allylic silanes (1) via a,P-dialkoxyacylsilanes (2) as shown in Scheme 2. The di- and tri-merisation of the acetal protected glycolaldehyde (4) under strongly basic conditions furnished, after deacetalization, DL-thieose (ca.10%) and a 2 1 mixture of DL-allose and -mannose (ca.20%), respectively. ... 

Alkyl silyl ethers are cleaved by a variety of reagents Whether the silicon-oxygen or the carbon-oxygen bond is cleaved depends on the nature of the reagent used Treatment of alkoxysilanes with electrophilic reagents like antimony tri-fluonde, 40% hydrofluonc acid, or a boron tnfluonde-ether complex results in the cleavage of the silicon-oxygen bond to form mono-, di-, and tnfluorosiloxanes or silanes [19, 20, 21) (equations 18-20)... 

Because of the expense, toxicity, and purification problems associated with use of stoichiometric amounts of tin hydrides, there has been interest in finding other hydrogen-atom donors. The trialkylboron-oxygen system for radical initiation has been used with tris(trimethylsily)silane or diphenylsilane as a hydrogen-donor system.133... 

An alternative system for initiating radical cyclization uses triethylborane and oxygen. Under these conditions, tris(trimethylsilyl)silane is an effective hydrogen atom donor.239... 

Figure 4. Bronsied plot of the logarithm of the general base catalyzed hydrolysis rate constants vs. the p/C of the conjugate acids of the oxygen and nitrogen bases (buffers) for phenyl tris-(2-methoxyethoxy)silane ( ) and phenyl bis-(2-methoxyethoxy)silanol ( ) in aqueous solution at 30 C. and for tert-butyldimethyl-3-nitrophenoxysilane ( ) in 70% water/dioxane at 37°C.

The CVI-experiments with silane as precursor did not show any increase in permselectivity of the membranes. The reaction temperature was in all cases 275°C and several oxygen pressures were tried. In each experiment, however, white powder was obtained on the membrane surface, indicating the decomposition of silane at the surface of the membrane. Reaction conditions could not be chosen in such a way that a highly separative layer was obtained. This was probably related to with the fact that the reactor temperature or the concentration of silane in the precursor gas was too low. Safety regulations, however, prohibited an increase of the silane concentration in the precursor flow. 

Et3B as a simple radical initiator was first discovered in hydrostannylation of alkynes [5], The reactions were performed at room temperature or below in the presence of a trace amount of oxygen (Scheme 2). Hydrostannylation was applied to the synthesis of dehydroiridodiol (1) and a-methylene-y-butyrolactone (2). Et3B-induced radical addition reactions of triphenylgermane [7], tris(trimethylsilyl)silane... 

Exemplificative of a third type of oxygen-bonded acetylacetonate derivative is the compound formed from the reaction trimethylchloro-silane and acetylacetone (77). The product from this reaction is 2-tri-methylsiloxy-2-pentene-4-one. It is to be noticed that this silicon compound contains a dangling ligand even though several chelated acetyl-acetonates of silicon are known. Dangling complexation of potential... 

The amount of iodomethane recovered suggested that some cleavage also occurred at the central oxygen of the polyether to yield MeOCH CH I and ISiHjOCH CH OMe, Dimethyl ether reacted even more readily with the hexylpyridine adduct to give, after one hour at 0, silane, iodomethane, and tri-methoxysilane. This is consistent with an initial cleavage to yield methoxy-silane (3), which then disproportionates in a base-catalysed reaction (4),... 

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