Silane, substituted

A four-armed star polymer consisting of silane substituted with different block polymer chains ... 

A three-armed star polymer consisting of silane substituted with poly(vinyl chloride), poly(ethylene oxide) and polystyrene chains, the last of which is linked to the central unit through an oxygen atom. 

Unsymmetrical silylmercurials are more resistant to symmetrization than dialkylmercur-ials, RR Hg. The low steric factor in these silane substitution reactions is apparent in the reaction ... 

In method (d) of Fig. 18, in the sol-gel counterpart of (b), the alkoxy-silane-substituted metal complex is formed prior to its incorporation into the material by sol-gel processing. 

Concomitant rise in the viscosity of the reaction mixture was also noticed. NMR spectroscopy manifested the appearance of a new peak at 8 69.83 (Me3C-OSi) representative of a silane substituted tertiary carbon center of tert-butanol beside the peak at 8 68.02 (Me3C-OH). After 34 h, the intensity of the silane substituted tert-carbon peak reached optimum level, while the unsubstituted carbon peak disappeared completely. Si NMR spectra also corroborated complete transformation of Si-H... 

Table 2. Selected C-NMR data of silane-substituted 1,3,5-triethinylbenzene [ppm]. ...

Additives can also be used to improve the hydrolytic stability of polyester polyurethanes. Glycol-cured materials are reported to be stabilized with cyclic imines. Substituted ureas or thioureas ethylene-diaminetetraacetic acid-derived chelating agents oxycarbonyl isocyanates epoxies carbodiimides, alone " or in combination with silica silanes " substituted phthalimides and an undisclosed combination of additives have all been cited as stabilizers for polyester polyurethanes. 

Related diene synthesis using silane-substituted allylic organometallics (a) Chan T-H, Li J-S (1982) J Chem Soc Chem Commun 969 (b) Sato F, Suzuki Y, Sato M (1982) Tetrahedron Lett 23 4589 (c) Reetz MT, Wenderoth B (1982) ibid. 23 5259 (d) Murai A, Abiko A, Shimada N, Masamune T (1984) ibid. 25 4951 (e) Ikeda Y, Ukai J, IkedaN, Yamamoto H (1987) Tetrahedron 43 731 and references therein... 

Silane-substituted vinyl aluminum reagents can also be added to five- or six-membered cyclic enones. The silane moiety in these molecules presents an excellent opportunity for further functionalization to synthesize useful chiral molecules. 

Silanes substituted with allyl groups are known to give alternating copolymers with Copolymerization of various mixtures of trimethylallylsilane... 

Hydrogenolysis of ally acetates 80 with triethylammonium formate gives aDyl-silanes substituted at the a-position (81) (Scheme 5.20) [28]. Disilyl reagent 81a reacts with octanal in the presence of BFj-OEtj at —40°C to yield tert-butyldi-methylsilyl-substutited product 82a solely, while allylation with 81b proceeds at -78 °C to give 82b. Thus, the carbon-tin bond in 81b is cleaved much faster than the carbon-silicon bond. 

Hydride attacks regioselectively at the Si-substituted carbon in the hydro-genolysis of the silylated allylic carbonate 626 with formate, affording the allylic silane 627[I42]. 

The reaction of HCl and silicon, germanium, and boron hydrides is cataly2ed by aluminum chloride and is useful for preparing chloro-substituted silanes andgermanes. 

At 165°C and in the presence of chloroplatinic acid as catalyst, isoprene reacts with trichlorosilane, metbyldicblorosilane, ethyldichlorosilane, ben2yldichlorosilane, and diben2ylchlorosilane (72). The addition is 1,4- with the substituted silane group attaching to the first carbon atom. 

Catalysis. Platinum-catalyzed hydrosilation is used for cross-linking siUcone polymers and for the preparation of functionally substituted silane monomers (250). The most widely used catalyst is chloroplatinic acid (Spier s catalyst), H2PtCl3. Other compounds that catalyze the reaction include Pt(Il)... 

Silicon reacts at elevated temperatures with the halogens, forming SiCl, Sil, SiBr, and SiF. There is also a series of halogen-substituted silanes such as trichlorosilane, SiH Cl, and dichlorosilane, S1H2CI2. Both SiCl and SiH Cl are relatively easy to make, purify, and reduce to silicon. These are the silicon compounds most often used as feedstocks in the manufacture of high purity silicon. 

Silanes react with alkyllithium compounds, forming various alkylsilanes. Complete substitution is generally favored however, less substituted products can be isolated by proper choice of solvent. AH four methylsHanes, vinylsHane [7291-09-1and divinylsilane [18142-56-8] have been isolated from the reaction of SiH and the appropriate alkyllithium compound with propyl ether as the solvent (35). MethylsHane and ethyldisHane [7528-37-2] have been obtained in a similar reaction (36). 

Dialkylanaino-substituted silanes have also been obtained by a similar process (149—151). 

In comparison to the Si—OR bond, the Si—C bond can be considered essentially unreactive if the organic moiety is a simple unsubstituted hydrocarbon. If the organic moiety is substituted as in the case of a trialkoxysilane, the chemistry is more appropriately considered elsewhere (see Silicon COMPOUNDS, SILANES SILICON COMPOUNDS, SILYLATING AGENTS). 

Trialkyltin substituents are also powerful ipso-directing groups. The overall electronic effects are similar to those in silanes, but the tin substituent is a better electron donor. The electron density at carbon is increased, as is the stabilization of /S-carbocation character. Acidic cleavage of arylstannanes is formulated as an electrophilic aromatic substitution proceeding through an ipso-oriented c-complex. ... 

The six-position may be functionalized by electrophilic aromatic substitution. Either bromination (Br2/CH2Cl2/-5°) acetylation (acetyl chloride, aluminum chloride, nitrobenzene) " or chloromethylation (chloromethyl methyl ether, stannic chloride, -60°) " affords the 6,6 -disubstituted product. It should also be noted that treatment of the acetyl derivative with KOBr in THF affords the carboxylic acid in 84% yield. The brominated crown may then be metallated (n-BuLi) and treated with an electrophile to form a chain-extender. To this end, Cram has utilized both ethylene oxide " and dichlorodimethyl-silane in the conversion of bis-binaphthyl crowns into polymer-bound resolving agents. The acetylation/oxidation sequence is illustrated in Eq. (3.54). 

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