Silicon compounds alkylation

Alkoxides of nonmetals are described in articles about the corresponding compounds (see Boron COMPOUNDS, Boron oxides Silicon compounds). Metal alkyls, in which the alkyl group is bound direcdy to the metal, are also discussed elsewhere (see Aluminum compounds). 

Silylene complexes are not only stable with donor substituents but also with simple alkyl residues at silicon. These alkyl complexes still have a sufficient thermodynamic stability, but otherwise are reactive enough to allow a rich and diverse chemistry. Particularly the chlorocompounds 7 and 11 are valuable starting materials for further functionalization reactions the details of these reactions will be discussed in the forthcoming sections. The data for the known compounds are summarized in Table 1. 

Friedel-Crafts Alkylations with Silicon Compounds... 

CHARACTERISTICS OF FRIEDEL-CRAFTS ALKYLATIONS WITH SILICON COMPOUNDS... 

Jung, II Nam, and Yoo, Bok Ryul, Friedel-Crafts Alkylations with Silicon Compounds. 46 145... 

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... 

The presently known silicon chemical shift range is 990 ppm. This includes the Dsd form of decamethylsilicocene 28 (5 Si = —423 (solid state)), which is the most shielded resonance reported to date and the alkyl-substituted silylene 45, which presently defines the high-frequency end of the spectrum at 5 Si = 567. Most silicon chemical shifts occur, however, in a much smaller range from 5 Si = +50 to —190. This includes hexa-, penta- and tetracoordinated silicon compounds and for trivalent, positively charged silicon a significant low-field shift compared to comparable tetravalent silicon species is expected. 

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... 

Gngnard reagents - [BROMINE COMPOUNDS] (Vol 4) - [ESTERS, ORGANIC] (Vol 9) -from benzene [BENZENE] (Vol 4) -chemiluminescence [LUMINESCENTMATERIALS - CHEMILUMINESCENCE] (Vol 15) -magnesium alkyls from [MAGNESIUM COMPOUNDS] (Vol 15) -reaction of propylene oxides [PROPYLENE OXIDE] (Vol 20) -for silanes [SILICON COMPOUNDS - SILANES] (Vol 22) -for sulfoxide synthesis [SULFOXIDES] (Vol 23)... 

A new direction in the chemistry of hypervalent silicon compounds has recently been developed by Tacke and coworkers the chemistry of zwitterionic organosilicates28-31. In these compounds the silicon is formally negative, with a cationic nitrogen attached to it by an alkyl chain. One of the groups of products of this general class is the pentacoordinate zwitterionic fluorosilicates31. 

It is known from electrochemical studies that fullerenes are easily reduced. Up to 6 electrons can be added reversibly [19], and, as mentioned earlier, the excited states are even more easily reduced. A large number of electron donors were investigated including aromatic and alkyl amines [29,43,79,119-140,152,161], ni-troxide radicals [57,117], suspensions of Ti02 [118], polyaromatic compounds, [19,127] organo-silicon compounds, [133,158] phenothiazine, [133] acridine [145,154], (3-carotene [141], tetrathiafulvalenes [146], tetraethoxyethene [147], phthalocyanines [148], porphyrines [151,153], NADH and analogues [150,154, 155], borates [156,159], and naphtoles [23] to name a few representative cases. 

The reaction of benzo[A]-l,3-diazasilole 85 with lithium alkyls yields the insertion product 112. It was suggested that the initial step of this reaction is the formation of the donor-acceptor complex 113 (Scheme 10) <2002JOM272, 2002JOM150>. The tetracoordinated silicon compounds 112 might have synthetic potential as silylene transfer reagents. 

Silyl groups, which tend to increase lipid solubility, may be used as a substitute for alkyl branching in space-filling groups. Direct substitution of a silicon atom for a carbon atom increases the hydrophobic character of a compound, even without the addition of more alkyl groups. Table III lists the relative partition coefficients of two pairs of carbon and silicon compounds in octanol-water, a system used to approximate the lipid-water system within an organism. As may be seen from the table, the silicon compounds are two to five times more soluble in the octanol phase this effect falls off with an increasing number of carbon atoms in the parent structure (36). 

Monomer silicone compounds, especially organochlorosilanes, hydroxyor-ganosilanes, alkylalkoxysilanes with amide groups in the alkyl radical, and acyloxyorganosilanes, have recently found an independent practical application, but their role as parent substances for the production of silicone oligomers and polymers is particularly important. 

Ethers of orthosilicon acid and their derivatives, tetraalkoxy(aroxy)silanes and alkyl(aryl)alkoxy(aroxy)silanes are a rather extensive class of silicone compounds. They are independently applied in various spheres of technology, but are particularly valuable as semi-products for preparing important silicone oligomers and polymers. 

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