cas 754-05-2, Vinyltrimethylsilane | Articles data

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Radiolytic silylation of alkenes and alkynes by gaseous R3Si+ ions. Stereochemical evidence for the β-silyl effect
Carbocation intermediate stabilized by a β silyl group have been characterized using the silylation of alkenes by R3Si+ ions as a route of formation. Neutral silylated products have been obtained from the reaction of R3Si+ ions, generated in a gaseous medium at atmospheric pressure by a radiolytic technique, with selected alkenes, alkynes, and allene, thereby indicating the occurrence of electrophilic silylation. Notable fectures of the charged silylated intermediates emerge from the isomeric product distribution. The silylation of cis- and trans-2-butene shows a high degree of retention of configuration, as expected if a bridged species (I) were the reaction intermediate. Alternatively, the intermediacy of an open structure (II), whereby C-C bond rotation is inhibited by the hyperconjugative interaction between the β silyl group and the vacant up orbital, should be inferred. The charged intermediates from the silylation of alkenes and alkynes are found to be unreactive toward conceivable isomerizations to more stable species, such as the ones bearing the positive charge of silicon. Stereoelectronic factors affect the deprotonation of the silylated intermediates, which may involves loss of the proton either the α or the γ position with respect to the silylated carbon. A comparison of the reactivity of alkenes and alkynes in the cationic silylation reaction is presented.
Chiavarino, Barbara,Crestoni, Maria Elisa,Fornarini, Simonetta
p. 1523 - 1527
(1998)
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KINETICS AND MECHANISM OF THE PYROLYSIS OF ALLYLTRIMETHYLSILANE.
The gas-phase thermal decomposition of allyltrimethylsilane has been reinvestigated by using deuterium labeling and kinetic studies of variable pressure. Trimethylvinylsilane, the major product at high pressures, is found not to be a primary product of unimolecular decomposition. Silyl radical trapping allowed kinetic separation of the two competitive primary processes of decomposition: a concerted retroene elimination of propene to directly produce a silene and Si-C bond homolysis.
Barton,Burns,Davidson,Ijadi-Maghsoodi,Wood
p. 6367 - 6372
(1984)
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Trimethylsilylacetylene synthesis process
The invention discloses a process route for synthesizing trimethylsilylacetylene, which comprises the following steps of: generating trimethylchlorosilylethylene by taking ethylene bromide and trimethylchlorosilane as initial raw materials through a Grignard method, and forming 1-bromo trimethylchlorosilylethylene under the action of alkali through a bromination reagent; and removing monomolecularhydrogen bromide under the action of strong alkali to generate trimethylsilylacetylene. Compared with the traditional process, the process route has the advantages that the use of gas acetylene is avoided, the risk is reduced, the safety is improved, the used raw materials are easily available, the operation is easy, the safety and the environmental protection are realized, and the industrial production can be realized.
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(2021/01/11)

Platinum(II) Di-ω-alkenyl Complexes as slow-Release Precatalysts for Heat-Triggered Olefin Hydrosilylation
We describe the synthesis, characterization, and catalytic hydrosilylation activity of platinum(II) di-ω-alkenyl compounds of stoichiometry PtR2, where R = CH2SiMe2(vinyl) (1) or CH2SiMe2(allyl) (2), and their adducts with 1,5-cyclooctadiene (COD), dibenzo[a,e]cyclooctatetraene (DBCOT), and norbornadiene (NBD), which can be considered as slow-release sources of the reactive compounds 1 and 2. At loadings of 0.5 × 10-6-5 × 10-6 mol %, 1-COD is an active hydrosilylation catalyst that exhibits heat-triggered latency: no hydrosilylation activity occurs toward many olefin substrates even after several hours at 20 °C, but turnover numbers as high as 200000 are seen after 4 h at 50 °C, with excellent selectivity for formation of the anti-Markovnikov product. Activation of the PtII precatalyst occurs via three steps: slow dissociation of COD from 1-COD to form 1, rapid reaction of 1 with silane, and elimination of both ω-alkenyl ligands to form Pt0 species. The latent catalytic behavior, the high turnover number, and the high anti-Markovnikov selectivity are a result of the slow release of 1 from 1-COD at room temperature, so that the concentration of Pt0 during the initial stages of the catalysis is negligible. As a result, formation of colloidal Pt, which is known to cause side reactions, is minimized, and the amounts of side products are very small and comparable to those seen for platinum(0) carbene catalysts. The latent reaction kinetics and high turnover numbers seen for 1-COD after thermal triggering make this compound a potentially useful precatalyst for injection molding or solvent-free hydrosilylation applications.
Girolami, Gregory S.,Liu, Sumeng
p. 17492 - 17509
(2021/11/04)

Vanadium-Catalyzed Cross Metathesis: Limitations and Implications for Future Catalyst Design
Self-metathesis of terminal olefins using vanadium(V) alkylidenes is presented. Under various reaction conditions, incomplete conversion is observed due to decomposition of the metallocyclobutane intermediate via β-hydride elimination. The activity was observed to decline when a more electron withdrawing, less sterically bulky ligand was used, in contrast to trends observed in ring-opening metathesis polymerization with vanadium catalysts. These results provide insight into the current limitations of olefin metathesis with vanadium catalysts, as well as guidance for catalyst development.
Farrell, Wesley S.
supporting information
p. 3481 - 3485
(2019/11/13)

Bench-Stable Cobalt Pre-Catalysts for Mild Hydrosilative Reduction of Tertiary Amides to Amines and Beyond
The readily synthesized and bench-stable cobalt dichloride complex (dpephos)CoCl2 is employed as a pre-catalyst for a diversity of silane additions to unsaturated organic molecules, including the normally challenging reduction of amides to amines. With regard to hydrosilative reduction of amides even more effective and activator free catalytic systems can be generated from the bench-stable, commercially available Co(acac)2 and Co(OAc)2 with dpephos and PPh3 ligands. These systems operate under mild conditions (100 °C), with many examples of room temperature transformations, presenting a first example of mild cobalt-catalyzed hydrosilylation of amides.
Nurseiit, Alibek,Janabel, Jaysan,Gudun, Kristina A.,Kassymbek, Aishabibi,Segizbayev, Medet,Seilkhanov, Tulegen M.,Khalimon, Andrey Y.
p. 790 - 798
(2019/01/09)

Cobalt-catalyzed hydrosilation/hydrogen-transfer cascade reaction: A new route to silyl enol ethers
Capitalizing on cobalt: A new route to silyl enol ethers employing a Co-catalyzed cascade reaction featuring a tandem hydrosilation/hydrogen-transfer reaction is reported. The low catalyst loading, mild reaction conditions, and unique η2-silane resting state showcase the impressive utility of this seldom used transition-metal catalyst in C-H activation reactions (see scheme; VTMS = vinyltrimethylsilane; Cp* = 1,2,3,4,5- pentamethylcyclopentadiene). Copyright
Lyons, Thomas W.,Brookhart, Maurice
supporting information
p. 10124 - 10127
(2013/09/02)

Enantio- and diastereoselective synthesis of syn-β-hydroxyallylsilanes via a chiral (Z)-γ-silylallylboronate
syn-β-Hydroxyallylsilanes of general structure 11 and 28 are prepared in 50-86% yield and 91-95% ee (for aliphatic aldehydes; 50% ee for benzaldehyde) via the BF3-Et2O-promoted γ-silylallylboration reactions, using reagents 14 and 15.
Lira, Ricardo,Roush, William R.
p. 4315 - 4318
(2008/03/11)

Titanocene-mediated homolytic opening of epoxysilanes
The titanocene(III) chloride mediated opening of silyloxiranes has been examined. Electron transfer from the metal leads to α-silyl radicals with total regiocontrol. The radicals could be trapped by various olefins, and the corresponding adducts were obtained in good yields (Table). Further substitution of the oxirane by alkyl groups proved detrimental to the reactions, but ring opening remained essentially regioselective.
Puljic, Nicolas,Albert, Matthias,Dhimane, Anne-Lise,Fensterbank, Louis,Lacote, Emmanuel,Malacria, Max
p. 2297 - 2305
(2007/10/03)

Catalytic asymmetric Claisen rearrangement in natural product synthesis: Synthetic studies toward (-)-xeniolide F
(Chemical Equation Presented) The catalytic asymmetric Claisen rearrangement (CAC) of a highly substituted and functionalized α-alkoxycarbonyl-substituted allyl vinyl ether has been exploited to gain access to an advanced building block for the projected total synthesis of (-)-xeniolide F, the enantiomer of a xenicane diterpene isolated from a coral of the genus Xenia.
Pollex, Annett,Hiersemann, Martin
p. 5705 - 5708
(2007/10/03)

1-Bromo-1-lithioethene: A practical reagent for the efficient preparation of 2-bromo-1-alken-3-ols
(Matrix presented) A reliable preparative-scale synthesis of 1-bromo-1-lithioethene is reported. This reagent undergoes clean 1,2-addition with a range of aldehydes and ketones at -105°C to afford the corresponding 2-bromo-1-alken-3-ols in moderate to excellent yield. Efficient diastereoselective addition to α-siloxy and α-methylcyclohexanones, as well as protected 3-keto furanose sugars, is achieved in the presence of 10 mol% CeBr3. The resulting bromoallylic alcohol adducts have considerable potential as synthetic building blocks.
Novikov, Yehor Y.,Sampson, Paul
p. 2263 - 2266
(2007/10/03)

Diverse catalytic activity of the cationic actinide complex [(Et2N)3U][BPh4] in the dimerization and hydrosilylation of terminal alkynes. Characterization of the first f-element alkyne π-complex [(Et2N)2U(CCtBu)(η2-HCC tBu)][BPh4]
The cationic actinide complex [(Et2N)3U][BPh4] is an active catalytic precursor for the selective dimerization of terminal alkynes. The regioselectivity is mainly towards the geminal dimer but for bulky alkyne substituents, the unexpected cis-dimer is also obtained. Mechanistic studies show that the first step in the catalytic cycle is the formation of the acetylide complex [(Et2N)2UCCR][BPh4] with the concomitant reversible elimination of Et2NH, followed by the formation of the alkyne π-complex [(Et2N)2UCCR(RCCH)][BPh4]. This latter complex (R=tBu) has been characterized spectroscopically. The kinetic rate law is first order in organoactinide and exhibits a two domain behavior as a function of alkyne concentration. At low alkyne concentrations, the reaction follows an inverse order whereas at high alkyne concentrations, a zero order is observed. The turnover-limiting step is the CC bond insertion of the terminal alkyne into the actinide-acetylide bond to give the corresponding alkenyl complex with ΔH?=15.6(3) kcal mol-1 and ΔS?=-11.4(6) eu. The following step, protonolysis of the uranium-carbon bond of the alkenyl intermediate by the terminal alkyne, is much faster but can be retarded by using CH3CCD, allowing the formation of trimers. The unexpected cis-isomer is presumably obtained by the isomerization of the trans-alkenyl intermediate via an envelope mechanism. A plausible mechanistic scenario is proposed for the oligomerization of terminal alkynes. The cationic complex [(Et2N)3U][BPh4] has been found to be also an efficient catalyst for the hydrosilylation of terminal alkynes. The chemoselectivity and regiospecificity of the reaction depend strongly on the nature of the alkyne, the solvent and the reaction temperature. The hydrosilylation reaction of the terminal alkynes with PhSiH3 at room temperature produced a myriad of products among which the cis- and trans-vinylsilanes, the alkene and the silylalkyne are the major components. At higher temperatures, besides the products obtained at room temperature, the double hydrosilylated alkene, in which the two silicon moieties are connected at the same carbon atom, is obtained. The catalytic hydrosilylation of (TMS)CCH and PhSiH3 with [(Et2N)3U][BPh4] was found to proceed only at higher temperatures. Mechanistically, the key intermediate seems to be the uranium-hydride complex [(Et2N)2U-H][BPh4], as evidenced by the lack of the dehydrogenative coupling of silanes. A plausible mechanistic scenario is proposed for the hydrosilylation of terminal alkynes taking into account the formation of all products.
Dash, Aswini K.,Wang, Jia Xi,Berthet, Jean Claude,Ephritikhine, Michel,Eisen, Moris S.
p. 83 - 98
(2007/10/03)

Investigating the kinetics of homogeneous hydrogenation reactions using PHIP NMR spectroscopy
The combination of parahydrogen induced polarization (PHIP), kinetics and NMR spectroscopy yields a powerful analytical tool: quantitative in situ NMR spectroscopy. Two versions of PHIP NMR experiments are presented to investigate the kinetics of homogeneously catalyzed hydrogenations. The first method, an experimental variation of the ROCHESTER experiment (ROCHESTER = rates of catalytic hydrogenation estimated spectroscopically through enhanced resonances), allows one to determine the hydrogenation rate independently of relaxation and other sources of decay, e.g., subsequent chemical reaction steps. The second method named DYPAS (dynamic PASADENA spectroscopy) uses a variable delay between the end of the hydrogen-addition period and the detection pulse. In principle, all processes during this delay can be described by a set of coupled differential equations. Their solutions can be fitted to the experimental data by a least-squares optimization of the involved kinetic parameters. The DYPAS method can be used to determine the rates of formation as well as the rates of decomposition of stable intermediates and has been applied to the case of freshly hydrogenated and still catalyst-attached product molecules. We provide kinetic data for the formation and decomposition of these unusual product-catalyst complexes during the hydrogenation of different styrene derivatives with a cationic Rh1 catalyst containing a chelating diphosphine ligand. The kinetic measurements indicate that the rate of formation of the catalyst-attached product increases whereas the rate constant of its decomposition diminishes if the para position of the arene ring of styrene carries an electron- donating substituent. In the case of p-aminostyrene as the substrate, the detachment step turned out to be rate limiting for the catalytic cycle. With certain substituted styrenes and cationic Rh1 complexes containing chiral chelating diphosphine ligands, two geometrically different (diastereomeric) product-catalyst adducts can be discriminated via PHIP NMR spectroscopy. The associated alternative reaction pathways have been analyzed by applying the DYPAS method, which can also be used to investigate the mechanism of an asymmetric hydrogenation.
Hübler, Patrick,Giernoth, Ralf,Kümmerle, Günther,Bargon, Joachim
p. 5311 - 5318
(2007/10/03)

Exploratory studies of H-atom abstraction and silyl-transfer photoreactions of silylalkyl ketones and (silylalkyl)phthalimides
Exploratory studies have been conducted to probe competitive H-atom abstraction and SET-promoted, silyl-transfer reactions of excited states of silylalkyl ketones and (silylalkyl)phthalimides. Photochemical investigations with the (silylalkyl)phthalimides have demonstrated that typical γ-H atom abstraction reactions occur upon irradiation in less polar and less silophilic solvents. In contrast, irradiation of these substances in polar-protic-silophilic solvents results in product formation via pathways involving SET-induced desilylation. Photoreactions of silylamido-aryl ketones in either nonsilophilic or silophilic solvents take place almost exclusively by sequential SET silyl-transfer routes to produce azetidine products. Finally, the chemical selectivities of photochemical reactions of silylpropyl-aryl ketones appear to depend on medium polarity and silophilicity. Irradiation of these substrates in less polar-nonsilophilic solvents leads to almost exclusive formation of acetophenone and vinyltrimethylsilane in essentially equal yields by a reaction pathway initiated by γ-H atom abstraction and 1,4-biradical fragmentation. However, irradiation of these substances in polar-silophilic solvents produces acetophenone and vinyltrimethylsilane in an ca. 1.7:1 ratio reflecting the fact that a silyl-transfer pathway competes with H-atom abstraction under these conditions.
Lee, Yean Jang,Ling, Rong,Mariano, Patrick S.,Yoon, Ung Chan,Kim, Dong Uk,Oh, Sun Wha
p. 3304 - 3314
(2007/10/03)

Stereoselective synthesis of homochiral (E)-vinyl phosphonates derived from (-)-ephedrine
A new synthesis of homochiral vinyl phosphonates starting from 1-alkynes is described. The title compounds were obtained in good yields by the reaction of chiral 2-chloro-1,3,2-oxazaphospholidin-2-one (1) with the 'ate'-complexes of vinyl alanes. The latter were prepared by zirconocene dichloride catalyzed hydroalumination of 1-alkynes with diisobutyl aluminum hydride (DIBAH).
Taapken, Thomas
p. 6659 - 6662
(2007/10/02)

Reaction of bis(trifluoromethyl)amino-oxyl with alkylchlorosilanes and allyldichloro(methyl)silane and of perfluoro-2,5-diazahexane 2,5-dioxyl with vinylsilanes and hydrolysis of the products
Treatment of the silanes MeSiHCl2, Me2SiHCl and EtSiMeCl2 with the oxyl (CF3)2NO(.) (1) gives the substitution products (CF3)2NOSiMeCl2 (4) and (CF3)2NOSiMe2Cl (5), and a mixture of (CF3)2NOCHMeSiMeCl2 (8) and (CF3)2NOCH2CH2SiMeCl2 (9) (ratio 20:37), respectively, while the silane EtSiMe2Cl affords mainly the ester (CF3)2NO2CMe (7).Attack of oxyl 1 on the silane CH2=CHCH2SiMeCl2 results in both allylic substitution and addition to give the compounds CH2=CHCH(SiMeCl2)ON(CF3)2 (14) and (CF3)2NOCH2CH(CH2SiMeCl2)ON(CF3)2 (15) (ratio 56:40).Reaction of the dioxyl (.)ON(CF3)CF2CF2N(CF3)O(.) (2) with the vinylsilanes CH2=CHSiX3 (X3 = Me3, Cl3, MeCl2) gives mainly 1:1 copolymers n (17), although the cyclic 1:1 adduct (18) is also formed in low yield.Hydrolysis of the silanes 15, (CF3)2NOCH2CH(SiMeCl2)ON(CF3)2 (19a) and (CF3)2NOCH2CH(SiCl3)ON(CF3)2 (19b) affords the corresponding polysiloxanes 24 and 25, and the polysilsesquioxane 26, respectively; the polymers 25 and 26 undergo rearrangement of the type -CH(Si)ON(CF3)2 --> -CH(OSi)N(CF3)2 on storage.The 1:1 copolymers 17b (X3 = MeCl2) and 17c (X3 = Cl3) are also hydrolysed to the corresponding siloxane and silsesquioxane polymers.In contrast, hydrolysis of the compounds 4,5 and (CF3)2NOCH2CH(OSiX3)N(CF3)2 (20a; X3 = MeCl2) and (20b; X3 = Cl3) results in Si-O bond cleavage.
Tipping, Anthony E.,Yadav, Rajendraprasad B.
p. 1 - 10
(2007/10/02)

The Operation of H-Atom and TMS-Group Transfer Processes in the Photochemistry of Silylamidoalkyl- and Silylalkyl-Ketones and -Phthalimides
Photoreactions of silylamidoalkyl- and silylalkyl-ketones and N-silylethylphthalimide operate by competitive H-atom and TMS-group transfer routes and whose relative efficiencies are influenced by side-chain and carbonyl substituents, and solvent.
Lee, Yean Jang,Lee, Chao Pin,Jeon, Yoon Tag,Mariano, Patrick S.,Yoon, Ung Chan,et al.
p. 5855 - 5858
(2007/10/02)

Oxidation of methylsilenes with molecular oxygen. A matrix isolation study
The photochemical and thermal oxidation of 1-methylsilene (2-silapropene) (1a), 1,1-dimethylsilene (1b), and 1,1,2-trimethylsilene (1c) has been investigated in O2-doped argon matrices. All silenes 1 are easily photooxidized in matrices containing more than 1% O2, but trimethylsilene (1c) is the only silene that exhibits thermal reactivity toward oxygen at temperatures as low as 20-40 K. The photochemical reactivity increases from 1a to 1c with increasing number of methyl groups at the double bond and decreasing ionization potential. Key intermediates in both the photochemical and the thermal oxidation of 1 are siladioxetanes 9. These species are labile even in low-temperature matrices and could not be identified spectroscopically, but evidence comes from the observed oxidation products such as a complex between methylsilanone and formaldehyde 8a and the formylsilanols 10. An additional oxidation pathway is observed for 1c with a methyl group at the C-atom of the silene moiety. Here, the primary adduct of 1c and 3O2, triplet-diradical T-21c, can either ring-close to give dioxetane 9c and the products derived of it or produce dimethylvinylsilyl hydroperoxide (22) via H-abstraction from a methyl group.
Trommer, Martin,Sander, Wolfram,Patyk, Andreas
p. 11775 - 11783
(2007/10/02)

A 1,2-Silicon Shift in Cyclopropylidenes leading to 1-Trialkylsilylcyclopropenes
1,1-Dibromo-2-trialkylsilylcyclopropanes, readily prepared by dibromocyclopropanation of vinyltrialkylsilanes, react with methyllithium at -90 to 20 deg C to give high yields of trialkylsilylcyclopropenes in which the silicon has apparently migrated to C-1.
Baird, Mark S.,Dale, Cynthia M.,Dulayymi, Juma'a R. Al
p. 1373 - 1374
(2007/10/02)

SYNTHESIS OF 1-TRIMETHYLSILYL-2-(METHYLCHLOROSILYL)ETHYLENES. I. REACTIONS OF β-CHLOROVINYLTRIMETHYLSILANE WITH CHLOROSILANES IN THE PRESENCE OF SODIUM
We have studied reactions of β-chlorovinyltrimethylsilane with chlorosilanes MenSiCl4-n (n = 0-3) in the presence of metallic sodium.We have determined the effect of various solvents and types of starting reagents on these reactions.We have isolated and identified liquid and gaseous reaction products.It was shown that these reactions are not of preparative value because of their ususual exothermic nature and the nonselectivity regardless of the type of chlorosilane and the reaction conditions.
Lakhtin, V. G.,Stolyarova, O. V.,Korshunov, A. I.,Turkel'taub, G. N.,Sheludyakov, V. D.
p. 68 - 73
(2007/10/02)

Elimination-Rearrangement in β-Functionalised Silanes-the Direction of the Rearrangement and its Scope
A new eliminative rearrangement of β-silyl carbanions requires phenyl on carbon α to silicon when the conjugate acid has a pKa (DMSO) in the range 12-30; rearrangement involves silicon and not phenyl migration.
Menichetti, Stefano,Stirling, Charles J. M.
p. 741 - 742
(2007/10/02)

A Ru(II) Enynyl Complex Mediates the Catalytic Dimerization of 1-Alkynes to Z-1,4-Disubstituted Enynes
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Bianchini, Claudio,Peruzzini, Maurizio,Zanobini, Fabrizio,Frediani, Piero,Albinati, Alberto
p. 5453 - 5454
(2007/10/02)

Ethylene insertion and β-hydrogen elimination for permethylscandocene alkyl complexes. A study of the chain propagation and termination steps in Ziegler-Natta polymerization of ethylene
The rates of ethylene insertion into the Sc-C bond for Cp*2ScR (Cp* = (η5-C5Me5), R = CH3, CH2CH3, CH2CH2CH3) have been measured at -80 °C by 13C NMR; the second order rate constants (M-1·s-1) are as follows: R = CH3, 8.1 (2) × 10-4; R = CH2CH3, 4.4 (2) × 10-4; R = CH2CH2CH3, 6.1 (2) × 10-3. The slow rate for the ScCH2CH3 complex is attributed to a ground-state stabilization by a β-C-H agostic interaction. The distributions of molecular weights for ethylene oligomers (CH3(CH2)nCH3, n = 11-47) produced from known amounts of ethylene and Cp*2ScCH2CH2CH3 at -80 °C satisfactorily fit a Poisson distribution, indicative of a living Ziegler-Natta polymerization system. From the measured, slower initiation rates of insertion for Cp*2ScCH3 and Cp*2ScCH2CH3 and propagation rates equal to that for Cp*2ScCH2CH2CH3, the molecular weight distributions of ethylene oligomers are also accurately predicted. Cp*2ScCH3 undergoes a single insertion with 2-butyne with a moderate enthalpy of activation and a large, negative entropy of activation. The second-order rate constants for the insertion of 3-phenyl-2-propyne, 2-pentyne, and 4-methyl-2-pentyne have been measured. The rates for β-hydrogen elimination for members of the series of permethylscandocene alkyl complexes Cp*2ScCH2CH2R (R = H, CH3, CH2CH3, C6H5, C6H4-p-CH3, C6H4-P-CF3, C6H4-P-NMe2) have been obtained by rapidly trapping Cp*2ScH with 2-butyne. A transition state for the β-hydrogen elimination is indicated with partial charge on the β-carbon. Hydrogen is thus transferred to the scandium center as hydride in the β-H elimination process.
Burger, Barbara J.,Thompson, Mark E.,Cotter, W. Donald,Bercaw, John E.
p. 1566 - 1577
(2007/10/02)

A homogeneous iron(II) system capable of selectively catalyzing the reduction of terminal alkynes to alkenes and buta-1,3-dienes
Terminal alkynes are selectively hydrogenated to alkenes by the iron(II) catalyst precursors [(PP3)FeH-(N2)]BPh4 and [(PP3)FeH(H2)]BPh4 in THF under very mild conditions [PP3 = P(CH2CH2PPh3)3]. The catalytic reductive dimerization of HC≡CSiMe3 to 1,4-bis(trimethylsilyl)butadiene prevails over alkene formation at reflux temperature.
Bianchini, Claudio,Meli, Andrea,Peruzzini, Maurizio,Vizza, Francesco,Zanobini, Fabrizio,Frediani, Piero
p. 2080 - 2082
(2008/10/08)

Stationary and Pulsed Photolysis and Pyrolysis of 1,1-Dimethylsilacyclobutane
A study of the photolysis of 1,1-dimethylsilacyclobutane at 147 - 214 nm shows that of the four primary processes identified the predominant mode of decomposition is to C2H4 and dimethylsilaethene.Evidence from experiments in the presence of SF6 suggests that the dimethylsilaethene is formed initially in a vibrationally excited state: +hν -> Me2SiCH2v + CH2=CH2.Laser pulsed photolysis experiments at 193 nm have been carried out to measure tha absorption spectrum of Me2SiCH2, its absorption cross section, and the rate constant for Me2SCH2 combination: 2Me2SiCH2 -> (Me2SiCH2)2.The values obtained are ? (240 nm, base e) = (1.0 +/- 0.2)E-17 cm2 and k7 = (3.3 +/- 0.8)E-11 cm3 s-1.The kinetics of the pyrolysis of have also been reexamined, yielding the following rate constant expressions: k1/(s-1) = E(15.46 +/- 0.13) exp(-(31043 +/- 218)/T) and k-1/k71/2/(cm3/2s-1/2) = E(-7.0 +/- 0.3) exp(-(7850 +/- 300)/T).From these results, the heat of formation, ?-bond energy, and entropy of Me2SiCH2, have been deduced: ΔHfθ (g, 298 K) = 36 +/- 7 kJ mol-1, B? = 157 +/- 11 kJ mol-1, and Sθ(g, 298 K) = 332 +/- 8 J mol-1 K-1.
Brix, Th.,Arthur, N. L.,Potzinger, P.
p. 8193 - 8197
(2007/10/02)

Synthesis of Trimethylsilyloxy and Hydroxy Compounds from Carbanions and Bis(trimethylsilyl)peroxide.
The reactions of bis(trimethylsilyl)peroxide with alkyl, vinyl, alkynyl, aromatic and heteroaromatic anions are described.Depending on the reaction conditions, the trimethylsilyloxy derivatives can be obtained alone or together with the corresponding trimethylsilyl derivatives, which is sometimes the major product.Enolates, generated using magnesium diisopropylamide give the corresponding hydroxycarbonyl compounds in good yields.An attempt to rationalise the above results is given, emphasising the wide use of bis(trimethylsilyl)peroxide in organic synthesis as an electrophilic hydroxylation reagent.
Camici, Lucia,Dembech, Pasquale,Ricci, Alfredo,Seconi, Giancarlo,Taddei, Maurizio
p. 4197 - 4206
(2007/10/02)

RADICAL REACTIONS OF (2-TRIMETHYLSILYLALLYL)TRIPHENYLSTANNANE WITH ALKYL HALIDES: A NEUTRAL ACETONE ENOLATE EQUIVALENT
Facile transfer of 2-trimethylsilylallyl group is achieved when (2-trimethylsilylallyl)triphenylstannane is reacted with some halides under radical reaction conditions.
Lee, Eun,Yu, Sang-Gu,Hur, Chang-Uk,Yang, Seung-Min
p. 6969 - 6970
(2007/10/02)

Reversal of electronic Substituent Effects in the Retro-Diels-Alder Reaction. A Charge Neutral Analogue of Oxyanion-Accelerated Cycloreversion
The retro-Diels-Alder reaction of anthracene cycloadducts is influenced by the dienophile substituents in the following ways: (1) electron-withdrawing groups increase the rate of the reaction; (2) strongly conjugating substituents make the reaction much faster than predicted by classical electron-withdrawing or -donating ability, in the best case by a factor of 3 x 106, and (3) there is no observable steric effect, in contrast to literature statements to the contrary.
Nanjappan, Palaniappan,Czarnik, Anthony W.
p. 2851 - 2853
(2007/10/02)

CHEMICAL PROPERTIES OF SILICON DERIVATIVES OF HEXACARBONYL-(S,S')-μ3-(1,2-ETHANEDITHIOLATO)DIIRON
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Lebedev, A. V.,Kuz'min, O. V.,Chernyshev, E. A.
p. 1624 - 1627
(2007/10/02)

Alkylsilyl Cyanides as Silylating Agents
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Mai, Khuong,Patil, Ghanshyam
p. 3545 - 3548
(2007/10/02)

SILYL AND SILYLMETHYL RADICALS, SILYLENES, SILA-ALKENES, AND SMALL RING SILACYCLES IN REACTIONS OF ORGANOCHLOROSILANES WITH ALKALI METAL VAPOURS
Dehalogenation of the organochlorosilanes Me3SiCl (I), Me2PrSiCl (II), Me3SiSiMe2Cl (III), Me3SiCH2SiMe2Cl (IV), ClCH2SiMe3 (V), ClCH2SiMe2SiMe3 (VI), ClCH2Me2SiSiMe2CH2Cl (VII), Me2SiCl2 (VIII), MePrSiCl2 (IX), Me3SiCH2SiMeCl2 (X), Me3SiCH2CH2SiMeCl2 (XI), Me3SiCH2CH2CH2SiMeCl2 (XII), ClCH2Si(H)MeCl (XIII), ClCH2SiMe2Cl (XIV), ClMe2SiSiMe2Cl (XV), ClCH2CH2CH2Si(H)MeCl (XVI), ClCH2CH2CH2SiMe2Cl (XVII), ClCH2CH2OSiMe2Cl (XVIII), ClMe2SiCH2SiMe2Cl (XIX), ClMe2SiCH2CH2SiMe2Cl (XX), and ClMe2SiCH2CH2CH2SiMe2Cl (XXI) with K/Na alloy vapours at 0.1-1 Torr and 300-320 deg C yields products derived from the reactions of short-lived intermediates, such as silyl and silylmethyl radicals, silylenes, and sila-alkenes.In addition, small-ring silacycles of low stability are formed as the intermediates in some of the dehalogenation reactions.Combination and H-atom abstraction are the main reactions of silyl and silyl-methyl radicals.These radicals are not prone to decomposition reactions when C-H, C-C, or Si-C bonds are at the β(Si-Si) bond with the formation of Me2Si=CH2 and the trimethylsilyl radical.The generation of alkylmethylsilylenes is accompanied by their decomposition processes, which involves intramolecular β(C-H) insertion of alkylmethylsilylenes and 2+1>-thermocyclodecomposition of intermediate silacyclopropanes.The contribution of δ(C-H) and ε(C-H) insertion reactions is much less pronounced, and in the formation of five- or six-membered silacycles.We did not succeed in obtaining monosilacyclobutanes, as the intramolecular γ(C-H) insertion is not typical for silylenes with alkyl substituents.Dehalogenation of chloromethylchlorosilanes with alkali metal vapours yields sila-alkenes, and that of 1,2-dichlorodisilanes gives disilenes. 1-Methyl-1-silaethylene, obtained by this method, does not rearrange into dimethylsilene, but dimerizes to give 1,3-dimethyl-1,3-disilacyclobutane.The formation of 1,3,5-trisilacyclohexanes takes place due to subsequent radical addition at the silicon-carbon double bond and cyclization of 1,6-biradicals.Dehalogenation of organochlorosilanes XVI, XVII, and XX opens up possibilities for the gas-phase synthesis of small organosilicon heterocycles: monosilecyclobutanes and 1,2-disilacyclobutanes.A new, low-stability heterocycle, i.e. 1,1,2,2-tetramethyl-1,2-disilacyclobutane, has been obtained, which enables a new, high polymer, polyethylenetetramethyldisilene, to be obtained.In the case of organochlorosilanes XVIII and XIX, cyclization is accompanied by secondary reactions of silacycles, rearrangements, dimerization, or decomposition.
Gusel'nikov, L. E.,Polyakov, Yu. P.,Volnina, E. A.,Nametkin, N. S.
p. 189 - 204
(2007/10/02)

REACTIONS OF DERIVATIVES OF PHOSPHORUS THIO ACIDS CONTAINING S-H, S-SI, AND S-Cl BONDS WITH ALKENYL-SILANES AND -STANNANES
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Kutyrev, G. A.,Kapura, A. A.,Cherkasov, R. A.,Pudovik, A. N.
p. 1919 - 1930
(2007/10/02)

PYROLYSIS OF SILICON-CONTAINING CYCLIC POLYSULPHIDES
Thermal decomposition of silicon-containing monocyclic polysulphides (1-methyl-3-trimethylsilyl-2,5-dithiacyclopentane (I), 1,4-bis(trimethylsilyl)-2,3,6,7-tetrathiacyclooctane (II) and 1-trimethylsilyl-2,3,4,5,6-pentathiacycloheptane (III)) has been stud
Chernyshev, E. A.,Kuz'min, O. V.,Lebedev, A. V.,Zaikin, V. G.,Mikaya, A. I.
p. 231 - 238
(2007/10/02)

SIDE REACTIONS IN THE HYDROSILYLATION OF VINYLSILANES IN PRESENCE OF SPEIER'S CATALYST
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Sheludyakov, V. D.,Zhun', V. I.,Vlasenko, S. D.
p. 1594 - 1597
(2007/10/02)

SOME CHEMICAL PROPERTIES OF (CHLOROVINYL)- AND ETHYNYL-SILANES
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Sheludyakov, V. D.,Zhun', V. I.,Lakhtin, V. G.,Bokharev, V. N.,Slyusarenko, T. F.,et al.
p. 566 - 571
(2007/10/02)

THERMAL DECOMPOSITION OF 1-TRIMETHYLSILYL-μ3-S,S'-ETHYLENEDITHIOLATOHEXACARBONYLDIIRON
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Chernyshev, E.A.,Kuz'min, O.V.,Lebedev, A.V.,Kabanov, B.K.,Tyurin, V.D.,et al.
p. 2184 - 2187
(2007/10/02)

REDUCTION OF TRIMETHYLSILYL-μ3-S,S'-ETHYLENEDITHIOLATOHEXACARBONYLDIIRON
Reduction of the dithiolatodiiron hexacarbonyl complex of trimethylvinylsilane (I) with LiAlH4 leads to the formation of thioiron carbonyl clusters, and is not accompanied with the generation of the corresponding dithiol.
Lebedev, A.V.,Chernyshev, E.A.,Kuz'Min, O.V.,Nametkin, N.S.,Tyurin, V.D.,Nekhaev, A.I.
p. 215 - 218
(2007/10/02)

VINYLSILYLENE REARRANGEMENT. A POSSIBLE SILACYCLOPROPANYLIDENE INTERMEDIATE
It is proposed that trimethylsilylvinylsilylene undergoes sequential rearrangement to a silacyclopropanylidene by silene to silylene isomerization of an intermediate 1-silacyclopropene.
Barton, Thomas J.,Burns, Gary T.
p. 159 - 162
(2007/10/02)

Catalytic Chemistry of Palladium Surfaces under Ultrahigh Vacuum Conditions
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Gentle, T. M.,Grassian, V. H.,Klarup, D. G.,Muetterties, E. L.
p. 6766 - 6767
(2007/10/02)

1,1-Dilithioethan
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Maercker, Adalbert,Theis, Manfred,Kos, Alexander J.,Schleyer, Paul von Rague
p. 755 - 757
(2007/10/02)

Gas-Phase Photolysis of 2,2-Dimethylbutane, 2,2,3-Trimethylbutane, 2,2,3-Trimethyl-2-silabutane, and 2,2,3,3-Tetramethyl-2-silabutane at 147 nm.
The 147-nm photolyses of 2,2-dimethylbutane, 2,2,3-trimethylbutane, 2,2,3-trimethyl-2-silabutane (isopropyltrimethylsilane), and 2,2,3,3-tetramethyl-2-silabutane (tert-butyltrimethylsilane) are reported.In addition, the mercury-sensitized photolyses of i-C4H10, trimethylsilane, and mixtures of i-C4H10 and trimethylsilane are reported which give disproportionation to combination (D/C) ratios of 2.1+- 0.2 and 0.28+-0.05 for (CH3)3C + (CH3)3C and (CH3)3Si + (CH3)3Si, respectively, and D/C ratios of 1.86+- 0.15and 0.55+- 0.08 for (CH3)C + (CH3)3Si to form 2-methyl-2-silapropene and i-C4H8, respectively.With the completion of this work, several trends and generalizations can be drawn concerning the importance of various processes in linear vs. branched alkanes and alkylsilanes.These conclusions are summarized in this report.
Doyle, Daryl J.,Tokach, S. K.,Gordon, M. S.,Koob, R. D.
p. 3626 - 3634
(2007/10/02)

Silylene to Silene Thermal Rearrangement. Generation and Rearrangement of Cyclopropylsilylene and Vinylsilylene
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Barton, Thomas J.,Burns, Gary T.,Goure, William F.,Wulff, Wlliam D.
p. 1149 - 1150
(2007/10/02)

REACTIVITY OF Si-H BONDS IN ORGANOSILANES
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Zhun', V. I.,Zhun', A. B.,Vlasenko, S. D.,Belorusskaya, L. A.,Chernyshev, E. A.,Sheludyakov, V. D.
p. 2266 - 2270
(2007/10/02)

The Mechanism of the Gas-Phase Pyrolysis of Esters. Part 13. The Very Strong Activating Effects of β-Trialkylmetal Groups
The rates of gas-phase pyrolysis of β-substituted ethyl acetates AcOCH2CH2X where X=SiMe3, SiEt3, GeEt3, and SiMe2Ph, and of 1-aryl-2-trimethylsilylethyl acetates have each been measured over a minimum of 50 deg C, between 282 and 397 deg C; the rates of pyrolysis of 2-aryldimethylsilylethyl acetates have been measured at 396.9 and 378.2 deg C.The β-organometallic substituents are not themselves eliminated (except at considerably higher temperatures) but strongly accelerate the normal elimination of acetic acid, the relative rates per β-hydrogen at 327 deg C for X being: H, 1.0; SiMe3, 125; SiEt3, 179; GeEt3, 108; SiMe2Ph, 144.These groups appear to activate by a combination of increasing the acidity of the β-hydrogen via stabilisation of the forming β-carbanion through (p->d)? bonding, stabilisation of the incipient α-carbocation by C-X hyperconjugation, and steric acceleration.The effect of substituents in the aryl ring of 1-aryl-2-trimethylsilylethyl acetates gave an excellent correlation with ?+ values with ρ - 0.52 at 327 deg C.The lower ρ-factor for this reaction compared to that for 1-arylethyl acetates (-0.66) is consistent with either conjugative stabilisation of the α-carbocation or increased β-hydrogen acidity.Substituents in the aryl ring of 2-aryldimethylsilylethyl acetates gave a very small positive ρ-factor indicating that overall their effect on β-hydrogen acidity is larger than that on the forming carbocation.The product of pyrolysis of AcO.CH2.CH2.GeEt3 viz.CH2=CHGeEt3 underwent increasingly rapid elimination of successive moieties, believed to be ethylene, in a reaction of stoicheiometry 4.0, which did not occur with the silicon analogue.
Eaborn, Colin,Mahmoud, Foad M. S.,Taylor, Roger
p. 1313 - 1320
(2007/10/02)

CHEMISTRY OF ORGANOSILICON COMPOUNDS. CXXIII. NEW PHOTOCHEMICAL AND THERMAL DEGRADATION REACTIONS OF VINYLDISILANES TO VINYLSILANES THROUGH (η3-1-SILAPROPENYL)TRICARBONYLIRON COMPLEXES
Vinyldisilanes (II) of the type R1CH=CR2SiMe2SiMe3 (a, R1 = Ph, R2 = H; b, R1 = H, R2 = Me; c, R1 = R2 = H) and (R1CH = CHSiMeR3-)2 (d, R1 = Ph, R3 = Me; e, R1 = H, R3 = Ph) undergo a novel degradation reaction to give the corresponding vinylsilanes, R1CH = CR2SiMe3 and (R1CH=CH)2SiMeR3, respectively, under photochemical or thermal conditions in the presence of a stoichiometric amount of pentacarbonyliron.Two α-styryldisilanes (IIf, CH2=CPhSiMe2SiMe3 and IIg, 2) undergo similar degradation reactions, but gave β-styryl- silanes.In the presence of additional benzophenone, IIb, IIc, and IIf gave (E)-Me3SiCH=CRSiMe2OCHPh2 (b, R = Me; c, R = H; f, R = Ph) under either photochemical or thermal conditions, but IIa gave under photochemical, or Ph2CHSiMe3 under thermal conditions as main product.Mechanisms involving η3-1-silapropenyltricarbonyliron intermediates are proposed, and indeed separately prepared (η3-1-silapropenyl)(trimethylsilyl)tricarbonyliron gave the same products under similar conditions.
Sakurai, Hideki,Kamiyama, Yoshiyasu,Nakadaira, Yasuhiro
p. 13 - 30
(2007/10/02)

Organosilicon Chemistry. Part 28. Reaction of Bis(trimethylsilyl)mercury with Fluoro-olefins and with Perfluoro-(3-methylbuta-1,2-diene)
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Datta, Ashok K.,Fields, Roy,Haszeldine, Robert N.
p. 235 - 265
(2007/10/02)

Radical Rearrangements in the Pyrolysis of Allyldisilanes
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Barton, Thomas J.,Jacobi, Stephanie A.
p. 7979 - 7981
(2007/10/02)

GENERATION AND REACTIONS OF METHYL(TRIMETHYLSILYLALKYL)SILYLENES Me3Si(CH2)nSi..Me IN THE GAS PHASE
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Gusel'nikov, L. E.,Lopatnikova, E.,Polyakov, Yu. P.,Nametkin, N. S.
p. 401 - 403
(2007/10/02)

NMR STUDY (1H, 13C and 29Si) OF (CH3)4-xSi(CH=CH2)x COMPOUNDS WHERE x = 0, 1, 2, 3, 4
The 1H, 13C and 29Si NMR spectra of the various methylvinylsilanes have been analysed with the aid of a special simulation program.From considerations of the chemical shifts and of the coupling constants 2,3J1H-1H, 1J13C-1H, 1J29Si-13C and 2J29Si-C-1H it is shown that a mesomeric-M effect from the vinyl group to the Me-Si group is important, in very good agreement with previously published PES results .The mesomeric interaction in this series is ascribed to a hyperconjugation in accordance with theoretical considerations .
Delmulle, L.,Kelen, G. P. van der
p. 309 - 314
(2007/10/02)