Unsaturated alkyl silicones

Heterocyclic Sulfur Compounds with Two or More Rings Hexachlorobenzene under Ring-Substituted Aromatics Hexachlorobutadiene under Unsaturated Alkyl Halides Hexachlorocyclohexane Lindane under Saturated Alkyl Halides Hexachlorocyclopentadiene under Unsaturated Alkyl Halides Hexachloroethane under Saturated Alkyl Halides Hexadecane under Alkanes and Cyclic Alkanes Hexafluoroethane under Saturated Alkyl Halides Hexamethyldisihzane under Silicon Compounds—Other Significant Hexanes under Alkanes and Cyclic Alkanes Hexylamine under Primary Aliphatic Amines and Diamines... 

The attachment of ODNs to silicon wafers is described in which hydrogen terminated Si(III) surfaces are modified with (o-unsaturated alkyl esters. Deprotection with tBuOK yielded a carboxyl modified surface, which was used to attach DNA. The silicon wafers were shown to exhibit excellent specificity and stability. UV-mediated attachment of alkenes has been used to functionalise silicon surfaces using t-BOC protected 10-aminodec-l-ene. After removal of the... 

Silicone emulsion Wollastonite extender, polishes Calcium monocarbonate extender, polishing powders Calcium sulfate dihydrate extender, polyamide resins Tosylamide/formaldehyde resin extender, polymeric systems Amines, C18-unsaturated alkyl, dimers extender, printing inks Coumarone/indene resin Kaolin extender, PU... 

It was found that treatment of a mixture of 120 and 121 with tris(diethylamino-sulfonium) trimethyldifluorosilicate [TASF(Et)] resulted in smooth addition-elimination to the naphthoquinone to form the y-alkylation product 125 (85 %). TASF(Et) is a convenient source of soluble, anhydrous fluoride ion [47]. It is believed that exposure of 121 to TASF(Et) results in fluoride transfer to generate a hypervalent silicate anion, as depicted in structure 124. The transfer of fluoride between TASF(Et) and 121 may be driven by stabilization of the anionic species 124 by delocalization of the carbon-silicon bond into the LUMO of the unsaturated ketone. 1,4-Addition-elimination of this species to the naphthoquinone 120 would then form the observed product. 

The reaction described is of considerable general utility for the preparation of benzoyloxy derivatives of unsaturated hydrocarbons.2"8 Reactions of 2-butyl perbenzoate with various other classes of compounds in the presence of catalytic amounts of copper ions produce benzoyloxy derivatives. Thus this reaction can also be used to effect one-step oxidation of saturated hydrocarbons,9, 10 esters,6,11 dialkyl and aryl alkyl ethers,12 14 benzylic ethers,11,15 cyclic ethers,13,16 straight-chain and benzylic sulfides,12, 17-19 cyclic sulfides,11,19 amides,11 and certain organo-silicon compounds.20... 

Cyclic alkyl nitronates may be used in tandem [4+2]/[3+2] cycloadditions of nitroalkanes, and this reaction has been extensively studied by Denmark et al. (64,333-335). In recent work, they developed the silicon-tethered heterodiene-alkene 219 (Scheme 12.63). Steric hindrance and the fact that both the nitroalkene and the a,p-unsaturated ester in 219 are electron deficient renders the possibility of self-condensation. Instead, 219 reacts with the electron-rich chiral vinyl ether 220 in the presence of the catalyst 224 to form the intermediate chiral nitronate 221. The tandem reaction proceeds from 221 with an intramolecular 1,3-dipolar cycloaddition to form 222 with 93% de. Further synthetic steps led to the formation of ( )-detoxinine 223 (333). A similar type of tandem reaction has also been applied by Chattopadhyaya and co-workers (336), using 2, 3 -dideoxy-3 -nitro-2, 3 -didehydrothymidine as the starting material (336). 

Comparison of all reported cleavages gives the apparent ordering H > Ph (or aryl) > alkyl in terms of tendency for groups to be cleaved from silicon, with the exception that at least one aryl substituent is retained on silicon in the anion VI. It is clear that reduction of aryl silanes leads to significant weakening of Si—R bonds that have appropriate symmetry for hyperconjugative interactions with the reduced n systems, a point that has been cited as evidence for the importance of n — type interactions in unsaturated silanes (86). 

The hydroxide anion catalyzed rate constants for the scries of alkyl tris-(2-methoxyethoxy)silanes obtained by Fohl were used to define a modified Taft equation, log(/cHO//cHO ) = 2.48cr +1.67 Es [42], A good correlation was obtained, except for vinyl and phenyl substituents. The anomalous behavior observed for phenyl and vinyl tris-(2-methoxyethoxy)silanes may have resulted because the steric parameter or the polar parameter may be influenced by the carbon-carbon double bond. The steric parameter for a,yS-unsaturated substituents may include an appreciable resonance effect. The polar parameter values may be influenced by the ability of silicon to back-bond through d orbitals with the a,/J-unsaturated system [37,49]. 

Assessing on the whole the method of the production of alkyl- and aryl-chlorosilanes based on the interaction of alkyl- and arylchlorides with free silicon (i.e. direct synthesis), we should say that this method in comparison with metalorganic synthesis is more efficient, especially for the production of methyl- and phenylchlorosilanes. As for unsaturated chlorosi-lanes (vinyl- and allylchlorosilanes) and organochlorosilanes with higher radicals (hexyl-, heptyl-, octyl- and nonylchlorosilanes), no direct synthesis technique has yet been developed. 

These substances are very promising for the synthesis of organochloro-silanes with various radicals at the silicon atom, i.e. by direct alkylation (or arylation) of hydrideorganochlorosilanes with chlorine derivatives of unsaturated and aromatic hydrocarbons. 

Trichlorosilane is of certain interest in the production of many or-ganochlorosilanes with one unsaturated, aromatic or higher alkyl group at the silicon atom thus, below we consider its production technique. 

Many of the results reviewed here suggest that a replacement of the usual alkyl or aryl substituents by silyl substituents in unsaturated silicon and germanium compounds may be rewarding. As we noted, silyl substituents do tilt the properties of silylenes, silyl radicals, and sequential BDE trends toward those in carbon chemistry. They have already been shown to stabilize disilenes with respect to dissociation to two silylenes, and this may be crucial to the further development of digermene and distannene chemistry. 

In the benzoin condensation, one molecule of aldehyde serves as an electrophile. If a carbanion is generated from protected cyanohydrins, a-aminonitriles or dithioacetals, it can react with electrophiles such as alkyl halides, strongly activated aryl halides or alkyl tosylates to form ketones. Amongst other electrophiles which are attacked by the above carbanions are heterocyclic A -oxides, carbonyl compounds, a,p-unsaturated carbonyl compounds, a,3-unsaturated nitriles, acyl halides, Mannich bases, epoxides and chlorotiimethyl derivatives of silicon, germanium and tin. 

As a general mle, unless an anion-stabilizing group, such as phenyl, or a heteroatom such as sulfur is present, the alkylsilane is not readily deprotonated. The a-halosilane can be deprotonated but, unlike the readily available chloromethyltrimethylsilane, there are few general methods to this approach. Al-kyllithium reagents add to vinylsilanes ( ) to produce the carbanion (287). Silyl derivatives with heteroatoms, such as sulfur, selenium, silicon or tin, in the a-position (288) may be transmetallated (Scheme 41). Besides the difficulty in synthesizing the anion, alkene formation lacks specificity for simple di- and tri-alkyl-substituted alkenes. As a result, the Peterson reaction of an a-silyl carbanion with a carbonyl has found the greatest utility in the synthesis of methylene derivatives, (as discussed in Section 3.1.3), heterosubstituted alkenes and a,p-unsaturated esters, aldehydes and nitriles. 

Acylation of a simple thiol with an alkyl carboxylate is not a very suitable method for preparation of S-alkyl thiocarboxylates. Transesterification is, however, possible if either the thiol or the carboxylic ester is activated. The enhanced reactivity of boron, aluminum and silicon thiolates has been utilized for the synthesis of a large variety of thiocarboxylic S-esters, including hydroxy derivatives (from lactones). a,P-Unsaturated thiol esters, e.g. cinnamoyl or 2-butenoyl derivatives, are also accessible. Michael addition, an undesirable side reaction of thiols, is completely avoided if alkyl trimethylsilyl sulfides ortris(arylthio)boranes are applied. ... 

U.S. 6162423 (2000) Sebag etal. (L Oreal) Dialkylether with ( 12-C30 alkyl radicals, same or different, linear or branched, saturated or unsaturated Improved homogeneity and stability of silicone sufficient foaming power... 

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