Triethylsilane studies

A teehnique that is a convenient source of radieals for study by EPR involves photolysis of a mixture of di-t-butyl peroxide, triethylsilane, and the alkyl bromide corresponding to the radieal to be studied. Photolysis of the peroxide gives t-butoxy radieals, whieh selectively abstract hydrogen from the silane. This reactive silicon radieal in turn abstracts bromine, generating the alkyl radieal at a steady-state eoncentration suitable for EPR study. 

The most common way to generate sulfonyl radicals for spectroscopic studies has been the photolysis of solutions containing di-t-butyl peroxide, triethylsilane and the corresponding sulfonyl chloride in a variety of solvents (equations 4-6). The slowest step in this sequence is the reaction between t-butoxyl radicals and triethylsilane (ks = 5.3 x 106m 1s-1)26 since that for chlorine abstraction (equation 6) is extremely efficient (cf. Table 4). 

The tertiary alcohol m,m,/ra ,v-perhydro-9h-phcnalcnol (7) is converted stereospecifically and in high yield (92%) to /ran.v,/ran.v,/ran.v-pcrhydrophcnalcnc (10) when treated with either triethylsilane or triphenylsilane and trifluoroacetic acid in dichloromethane (Eq. 15). Studies indicate that the reaction path follows the cation rearrangement 8 9 and that the trans trifluoroacetate ester related to... 

Further on, Sawamura et al. [37] investigated the influence of different counter anions on the catalytic activity of cationic silicon Lewis acids. In the studies an achiral salt was used. In previous cases [30] acetonitrile was used as a solvent, which is known to coordinate strongly the silicon cation species. Therefore, the application of toluene as a solvent was investigated with a silicon cationic species. Although even toluene coordinates a silicon cation [25, 38], an enhanced activity compared to other solvents, was found. The achiral salt was prepared in situ from triethylsilane and [Ph3C][B(CgFj) ] (17) as depicted in Scheme 10. 

Aluminum chloride induces polymerization of 1,1-dimethylsilacyclobutane but causes (66) to ring expand to th trisilacyclohexane and, remarkably, the tetrasilaadamantane (Scheme 115) (75IZV953). The polymerization of 1,3-disilacyclobutanes, variously substituted, both thermally and catalyzed has been widely studied by Russian workers. Di-/jl -chlorobis(cyclohexene)diplatinum(II) is most effective at catalyzing the polymerization of (66). The reaction is vigorous at 20-60 °C with small amounts of triethylsilane or carbon tetrabromide (Scheme 116) <66JCS(C)1137>. 

Another conceivable, but probably less likely, explanation of these experimental results56 is that the triethylsilane somehow catalyzes the decomposition of silylenoid into free silylene, which can then insert into the Si—H bond. In any case, the intermediacy of silylenes in a-dehalogenations remains an open question, worthy of further study. 

The fluorescence spectra of 9-anthrol (58) were studied in the sol-gel-xe-rogel transitions of Si-Al glasses of various composition prepared from tetraethyl orthosilicate and diisobutoxyaluminium triethylsilane [205], A biprotonic ESIPT between the anthrone and anthrol tautomers was observed in which a proton of the surface Brpnsted acid site on the —O—Si—O—A1—O— network was implicated. 

One example of minor variation in the catalytic cycle above is shown by Brookhart and co-workers, who performed a low temperature NMR study of their catalyst [Cp(CO)(PR.3)Fe+] in the alcoholysis of triethylsilane with ethanol and phenol.15 They observed catalyst deactivation during the reaction and upon evaluation of the system using low temperature NMR, they discovered that the ethanol disrupts the catalytic cycle in two ways (Figure 6). Ethanol... 

The efficiency of this approach was first studied through the radical reduction of 1-bromoadamantane by Et3SiH in presence of the polyHIPE-supported thiol catalyst (table l).The conversion of 1-bromoadamantane is complete after 1 hour at 80°C with a catalytic amount of dodecanethiol and two equivalents of triethylsilane. In the same conditions, 70% of the bromide were reduced in the presence of the supported thiol, showing a lower reactivity of this last one. The absence of reduction without thiol proved the role of the supported thiol. 

Ketones in alcohol solutions give mixed ethers with triethylsilane and trifluoroacetic acid, presumably via the hemiketal (or ketal). Similar results were obtained with ketones and silylated alcohols. Studies of the acid-catalyzed reduction of alcohols with silanes provide strong support for the postulate that carbonium ions are intermediates. ... 

In order to study the influence of different parameters on the reaction, specially the role of the support on the intrinsic activity and selectivity of heterogenized catalysts, as well as, the surface concentration effect and the geometrical constraints, three different silanes with a wide range of steric bulkiness, phenyldimethylsilane, diphenylsilane and triethylsilane have been used. 

Partial reductions of qnatemary salts to dihydro-componnds can be achieved with borohydride, bnt snch processes are much less well studied than in pyridininm salt chemistry (8.6). 1,4-Dihydropyrazines have been produced with either silicon or amide protection at the nitrogen atoms, and all the diazines can be rednced to tetrahydro derivatives with carbamates on nitrogen, which aids in stabilisation and thns allows isolation. 2-Amino-pyrimidines are rednced to 3,4,5,6-tetrahydro derivatives with triethylsilane in trifluo-roacetic acid at room temperature, the products thus retaining a gnanidine nnit. ... 

The intermediacy of the complex [Os(SiEt3)Cl(H2)(CO)(P Pr3)2] in the catalytic hydrosilylation of phenylacetylene was first observed by Oro and co-workers when the neutral hydride [OsHCl(CO)(P Pr3)2] was reacted with triethylsilane and the alkyne [81]. A theoretical study of silane addition across the C-C triple bond has also been reported [82] and the general scope of this reaction has been amply reviewed [17],... 

Competition between Two Silanes Containing Si—H for Ozone. The silanes studied included triethylsilane, tri-n-butylsilane, tri-n-hexylsilane, tricyclohexylsilane, fert-butyldicyclohexylsilane, tris(l-perhydronaphthyl)-silane, dimethyl(3,3,3-trifluoropropyl)silane and tris(3,3,3-trifluoropropyl)-silane. 

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