Phenylsilanes synthesis

In the course of studying the reactions of Si-H compounds with dialkyltitanocenes, with a view to the synthesis of new hydridosilyltitanocene complexes, we adventitiously discovered that phenylsilane undergoes facile, quantitative dehydrogenative coupling to a linear poly(phenylsilylene) under the catalytic influence of dimethyltitanocene. The ease with which this reaction proceeds initially induced us to underestimate the significance of the observation. 

We describe herein the synthesis of iodosilane by the reaction of phenylsilane with hydrogen iodide and the preparation of the methylated iodosilanes, namely (CH3) SiH3 I (n = 0-3), by the reaction of the parent hydride with hydrogen... 

Lanthanide-catalyzed enyne cyclization/hydrosilylation was also applied to the synthesis of silylated alkylidene cyclohexane derivatives. For example, reaction of the 3-silyloxy-l,7-enyne 17 with methylphenylsilane catalyzed by Gp 2YMe(THF) at 50°G for 8h gave 18 in quantitative yield as a 4 1 mixture of trans cis isomers (Equation (11)). Employment of methylphenylsilane in place of phenylsilane was required to inhibit silylation of the initially formed yttrium alkenyl complex, prior to intramolecular carbometallation (see Scheme 8). 

Yttrium-catalyzed diene cyclization/hydrosilylation was applied to the synthesis of aliphatic nitrogen heterocycles such as the indolizidine alkaloid ( )-epilupinine. l-Allyl-2-vinylpiperidine 30 was synthesized in four steps in 59% overall yield from commercially available ( )-2-piperidinemethanol (Scheme 10). Treatment of 30 with phenylsilane and a catalytic amount of Gp 2YGH3(THF) gave silylated quinolizidine derivative 31 in 84% yield, resulting from selective hydrometallation of the A-allyl G=G bond in preference to the exocyclic vinylic G=G bond. Oxidation of the crude reaction mixture with tert-huVf hydrogen peroxide and potassium hydride gave (i)-epilupinine in 51-62% yield from 30 (Scheme 10). 

Yttrium-catalyzed cyclization/hydrosilylation was also applied to the synthesis of silylated heteroaromatic bicyclic compounds. Reaction of l-allyl-2-vinyl pyrrole (32, n = R = H) with phenylsilane catalyzed by [(Gp )2YMe]2 at room temperature for 6 h followed by oxidation gave the corresponding heterobicycle amine 33 in 90% yield as a 98 2 mixture of isomers (Equation (23)). It was noteworthy that selective conversion of 32 to 33 required initial... 

FIGURE 1. Synthesis of substituted poly(phenylsilane)s. (Reprinted from Ref. 11.)... 

Below let us use poly [4-[2-(hydroxyphenyl)propyl-2]-phenyl]phenyl siloxane as an example and illustrate the production of polyphenylsiloxanes from trialkoxyphenylsilane (in our case tributoxy-phenylsilane) synthesised by the second technique, the etherification of phenyltrichlorosilane. The production comprises the following main stages the synthesis of tributoxyphenylsilane and its partial hydrolytic condensation the re-etherification of polybutoxyphenylsiloxane with diphenylolpropane. 

Fig. 11. Production diagram of polymethyl(phenyl)silsesquioxane from triace-toxyderivatives of methyl- and phenylsilanes 1 - synthesis reactor 2, 3, 5, 6, 21 -batch boxes 4, 17 - weight batch boxes 7, 15, 19 - coolers 8 - neutraliser 9, 12, 14, 16, 20 - collectors 10, 22 - settling boxes 11, 23 - ultracentrifuges 13 - distillation tank 18 - condensation apparatus 24 - container...

Bis(hydrazino)silanes are better stabilized with silyl groups bound to the nitrogen atoms. Although Zn-, Cd-, and Hg- connected silylhydrazines were described in 1970,52 silyl-substituted bis(hydrazino)silanes were not known until later. The first bis(hydrazino)silane that was silyl substituted at the terminal nitrogen atom and that showed no tendency to condensation was the terf-butyl-bis[iV,iV -bis(trimethylsilyl)hydrazino]phenylsilane 106, described in 1981.53 A decade later the synthesis of other stable bis(hydrazino)silanes was reported via different preparative methods using (a) mono-, (b) bis-, (c) tris-, and (d) tetrakis(silyl)hydrazines as precursors. 

Recently, sodium phenylsiloxanolate synthesis has been reported. For example, cyclo tetra siloxanolate [(Na ) C HjSi(0)0"] was synthesized by reacting tri-n-butoxyphenylsilane with sodium hydroxide in the presence of water [4], partial cage stracture [(Na )C HjSi(0(,5)20 ]3[C HjSi(0j 5)] was obtained that reacts with trimethoxy-phenylsilane and sodium hydroxide in the presence of water [5]. In 2003, we have... 

A large number of different a,(o-bis[(trifluoromethyl)sulfonyloxy]-substituted organosilicon compounds can be obtained by relatively simple methods from the corresponding amino-, allyl-, or phenylsilanes. Moreover, it is remarkable that these silyl triflate derivatives are often easily formed, when the synthesis of the corresponding chloro- or bromosilanes is difficult or does not appear to have been attempted. Eq. 2 and Eq. 3 show selected examples of this synthesis [10-12]. The products were prepared in high purities and yields. The resulting triflates should be used for the polycondensation without further purification, because they often cannot be destilled without decomposition. 

Isomerization of alkenes is catalyzed by bis(j7 -allyl)(jj -cyclopentadienyl)vanadium(IV). Cyclohexene nndergoes catalytic stereoselective aerobic oxidation with CpV(CO)4. Reductive coupling (see Reductive Coupling) of aldehydes and aldimines is catalyzed by a Cp-substituted vanadium compound in the presence of a chlorosilane and zinc or aluminum. Vanadocene or bis( ] -cyclopentadienyl)dimethylvanadium(IV) catalyzes the synthesis of 1,2-diphenyldisilane and 1,2,3-triphenyltrisilane from phenylsilane. ... 

A special one-pot deprotection-transacylation method involves coupling of activated Fmoc amino acids with Aloc-protected amino acid esters.The Aloc-deprotection proceeds with palladium/phenylsilane in the presence of the acylating species. Using Fmoc-Phe-F the synthesis of the sterically demanding dipeptide Fmoc-Phe-(Me)Aib-OMe was accomplished in a yield of 65% A similar one-pot approach to the acylation of the even more difficult hindered and weakly nucleophilic a-trifluoromethyl amino acid esters involves the intermediate A-Teoc protection. Thus treatment of ( )-Teoc-a-(a-CF3)Leu-OMe with Fmoc-Gly-F and a catalytic amount of tetraethylammonium fluoride in acetonitrile at 50 °C for 1-2 weeks gave ( )-Fmoc-Gly-(a-CF3)Leu-OMe (77%... 

Phenylsilanes are also accessible by direct synthesis from silicon and chlorobenzene, but they are currently predominantly produced by other processes. 

The dimethylamide function in 27 was reduced by the action of Ti(0/-Pr)4 and phenylsilane [35] to give aldehyde 29, which was then treated with p-TsOH in toluene at room temperature (Scheme 6). Under these reaction conditions, the intramolecular Friedel—Crafts-type cyclization occurred, and the subsequent dehydration of a benzylic alcohol also took place to afford phenanthrofuran skeleton (A-B-C-E ring) 30. The formation of the B-ring by way of intramolecular Friedel—Crafts acylation was first reported by Ginsburg in his synthesis of dihy-drothebainone in 1954 [36]. This transformation was also employed by White in the synthesis of (+)-morphine [37], and by Multzer in the synthesis of dihydrocodei-none [38 -0]. The Friedel—Crafts-type cyclization with an aldehyde function was used by Evans [41] in the formal synthesis of morphine and by Hudlicky in the... 

From benzophenone (560) and phenylsilane (559), mono- (561) and bis(diphenylmethyl)phenylsilane (562) can be obtained (equation 282)315. The asymmetric dimethyl(2,2-dimethyl-l-phenylprop-l-yloxy)phenylsilane (563) can be synthesized in the presence of a cationic rhodium complex (equation 283)316. An alkoxy replacement can be used for the synthesis of alkoxysilanes with non-identical alkoxy moieties, e.g. for diethoxymethoxysilane (565) (equation 284)317. 

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