- Metal-free hydrogen evolution cross-coupling enabled by synergistic photoredox and polarity reversal catalysis
-
A synergistic combination of photoredox and polarity reversal catalysis enabled a hydrogen evolution cross-coupling of silanes with H2O, alcohols, phenols, and silanols, which afforded the corresponding silanols, monosilyl ethers, and disilyl ethers, respectively, in moderate to excellent yields. The dehydrogenative cross-coupling of Si-H and O-H proceeded smoothly with broad substrate scope and good functional group compatibility in the presence of only an organophotocatalyst 4-CzIPN and a thiol HAT catalyst, without the requirement of any metals, external oxidants and proton reductants, which is distinct from the previously reported photocatalytic hydrogen evolution cross-coupling reactions where a proton reduction cocatalyst such as a cobalt complex is generally required. Mechanistically, a silyl cation intermediate is generated to facilitate the cross-coupling reaction, which therefore represents an unprecedented approach for the generation of silyl cationviavisible-light photoredox catalysis.
- Cao, Jilei,Lu, Kanghui,Ma, Lishuang,Yang, Xiaona,Zhou, Rong
-
supporting information
p. 8988 - 8994
(2021/11/23)
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- Novel Si(II)+and Ge(II)+Compounds as Efficient Catalysts in Organosilicon Chemistry: Siloxane Coupling Reaction ?
-
Novel catalytically active cationic Si(II) and Ge(II) compounds were synthesized and isolated in pure form. The Ge(II)+-based compounds proved to be stable against air and moisture and therefore can be handled very easily. All compounds efficiently catalyze the oxidative coupling of hydrosil(ox)anes with aldehydes and ketones as oxidation reagents and simultaneously the reductive ether coupling at very low amounts of 0.01 mol %. Because the catalysts also catalyze the reversible cyclotrimerization of aldehydes, paraldehyde can be used as a convenient source for acetaldehyde in siloxane coupling. It is shown that the reaction is especially suitable to make siloxane copolymers. Moreover, a new fluorine-free weakly coordinating boronate anion, B(SiCl3)4-, was successfully combined with the Si(II) and Ge(II) cations to give the stable catalytically active ion pairs Cp*Si:+B(SiCl3)4-, Cp*Ge:+B(SiCl3)4-, and [Cp(SiMe3)3Ge:+]B(SiCl3)4-.
- Fritz-Langhals, Elke,Kneissl, Sotirios,Piroutek, Phillip,Werge, Sven
-
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- Catalytic Disproportionation of Formic Acid to Methanol by using Recyclable Silylformates
-
A novel strategy to prepare methanol from formic acid without an external reductant is presented. The overall process described herein consists of the disproportionation of silyl formates to methoxysilanes, catalyzed by ruthenium complexes, and the production of methanol by simple hydrolysis. Aqueous solutions of MeOH (>1 mL, >70 percent yield) were prepared in this manner. The sustainability of the reaction has been established by recycling of the silicon-containing by-products with inexpensive, readily available, and environmentally benign reagents.
- Cantat, Thibault,Chauvier, Clément,Imberdis, Arnaud,Thuéry, Pierre
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supporting information
p. 14019 - 14023
(2020/06/09)
-
- Catalytic oxidation of diorganosilanes to 1,1,3,3-tetraorganodisiloxanes with gold nanoparticle assembly at the water-chloroform interface
-
The formation of the spherical self-assembly of gold nanoparticles (AuNPs) of 200 ± 20 nm size at the water-chloroform interface is achieved by employing the cyclotetrasiloxane [RSCH2CH2SiMeO]4 (R = CH2CH2OH) as the stabilizing ligand. The interfacially stabilized AuNPs act as a versatile catalyst for selective hydrolytic oxidation of only one of the Si-H bonds in secondary organosilanes, RR1SiH2 (R, R1 = alkyl, aryl, and sila-alkyl), to afford the high yield synthesis of 1,1,3,3-tetraorganodisiloxanes, (HRR1Si)2O. The study unravels for the first time the role of the photothermal effect arising from the excitation of the surface plasmon resonance of the AuNPs under visible light irradiation in enhancing the catalytic activity at ambient temperature.
- Shankar, Ravi,Sharma, Asmita,Jangir, Bhawana,Chaudhary, Manchal,Kociok-K?hn, Gabriele
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p. 813 - 819
(2019/01/09)
-
- Nickel(0) catalyzed oxidation of organosilanes to disiloxanes by air as an oxidant
-
We report here an efficient non-aqueous route to symmetrical disiloxanes from their corresponding organosilanes using Ni(COD)2 with 3,4,7,8-tetramethyl-1,10-phenanthroline in air. Our methodology is very simple and high yielding. The reaction mechanism is also proposed.
- Lv, Haiping,Laishram, Ronibala Devi,Li, Jiayan,Shi, Guangrui,Sun, Weiqing,Xu, Jianbin,Yang, Yong,Luo, Yang,Fan, Baomin
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supporting information
p. 971 - 974
(2019/03/07)
-
- Catalytic Metal-Free Deoxygenation of Nitrous Oxide with Disilanes
-
Because of its high kinetic stability, conditions to reduce the greenhouse gas N2O are limited; therefore, a better understanding of N2O chemistry and N-O bond cleavage is required. In this work, N2O was deoxygenated under metal-free conditions. Using disilanes as reducing agents and a catalytic amount of fluoride anions or alkoxides allowed a mild reduction at ambient pressure and temperature. DFT calculations unveiled the mechanism, which shows a nucleophilic addition of a silyl anion to the central N atom of N2O and release of N2 from a pseudo-Brook rearrangement.
- Anthore-Dalion, Lucile,Nicolas, Emmanuel,Cantat, Thibault
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p. 11563 - 11567
(2019/12/02)
-
- Synthesis, characterization and catalytic oxidation of organosilanes with a novel multilayer polyoxomolybdate containing mixed-valence antimony
-
Oxidation of organosilanes is one of the pivotal reactions in organic synthesis and the corresponding products of silanols are widely as raw materials in industrial processes. In this paper, a new type of polyoxomolybdate containing mixed-valence antimony, [SbVSbIII4Mo18O66]7? (1a), has been isolated as tetramethyl ammonium salt in aqueous solution. The compound was structurally characterized by FT-IR, XPRD, TG, XPS, ESI–MS etc. It is the first time that the containing mixed-valence antimony polyoxomolybdate was used as a heterogeneous catalyst to efficaciously catalyze the oxidation of organosilanes to silanols under mild reaction conditions. Furthermore, the catalyst was stable and maintained its catalytic activity after three reaction cycles.
- Wang, Yaping,Lu, Jingkun,Ma, Xinyi,Niu, Yanjun,Singh, Vikram,Ma, Pengtao,Zhang, Chao,Niu, Jingyang,Wang, Jingping
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p. 167 - 174
(2018/04/24)
-
- DMF-activated chlorosilane chemistry: Molybdenum-catalyzed reactions of R3SiH, DMF and R′3SiCl to initially form R′3SiOSiR′3 and R3SiCl
-
The room temperature reactions between R3SiH (R3?=?Et3, PhMe2, Ph2Me) and R′3SiCl (R′3?=?Me3, PhMe2, Ph2Me), with an excess of dimethylformamide (DMF) in the presence of (Me3N)Mo(CO)5 as a catalyst, result in the initial formation of R3SiCl, R′3SiOSiR′3 and Me3N as detected by 29Si, 13C, 1H NMR spectroscopy and GC/MS. As the reaction proceeds, the more so if the reaction temperature is raised, mixed disiloxanes R3SiOSiR′3 and ultimately lesser amounts of R3SiOSiR3 may be detected. A mechanism involving the activation of chlorosilanes by the nucleophilic DMF is proposed to produce transient imminium siloxy ion pairs, [Me2N[dbnd]CHCl]+[R′3SiO]? ? [Me2N[dbnd]CH(OSiR′3)]+Cl? which react with R3SiH to form Me2NCH2OSiR′3 and R3SiCl. A secondary reaction of Me2NCH2OSiR′3 with R′3SiCl produces the symmetrical disiloxane R′3SiOSiR′3 and ClCH2NMe2. The final stage of the reaction is the reduction of ClCH2NMe2 by R3SiH, a reaction which is reported for the first time. The newly created chlorosilane R3SiCl can become involved in the initial DMF activation chemistry thereby forming the other disiloxanes observed as the reaction proceeds.
- Gonzalez, Paulina E.,Sharma, Hemant K.,Pannell, Keith H.
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p. 376 - 381
(2017/06/30)
-
- Hydrogenation and Hydrosilylation of Nitrous Oxide Homogeneously Catalyzed by a Metal Complex
-
Due to its significant contribution to stratospheric ozone depletion and its potent greenhouse effect, nitrous oxide has stimulated much research interest regarding its reactivity modes and its transformations, which can lead to its abatement. We report the homogeneously catalyzed reaction of nitrous oxide (N2O) with H2. The reaction is catalyzed by a PNP pincer ruthenium complex, generating efficiently only dinitrogen and water, under mild conditions, thus providing a green, mild methodology for removal of nitrous oxide. The reaction proceeds through a sequence of dihydrogen activation, "O"-atom transfer, and dehydration, in which metal-ligand cooperation plays a central role. This approach was further developed to catalytic O-transfer from N2O to Si-H bonds.
- Zeng, Rong,Feller, Moran,Ben-David, Yehoshoa,Milstein, David
-
supporting information
p. 5720 - 5723
(2017/05/04)
-
- Reactions of silicon hydrides catalyzed by rhodium(III) sulfoxide complexes
-
Dehydrocondensation reactions of silicon hydrides catalyzed by the rhodium(III) complex [RhCl3(Me2SO)3] in the absence of the second substrate were studied. It was found that the complex [RhCl3(Me2SO)3] catalyzed the dehydrocondensation reaction with the formation of compounds containing siloxane bonds. Analysis of NMR spectra has shown that the reaction of [RhCl3(Me2SO)3] with silicon hydride includes sequential desoxygenation of sulfoxide ligands to sulfide ligands with the complex [RhCl3(Me2S)3] formation.
- Eliseeva,Prudnikova,Panikorovskii,Skvortsov
-
p. 1884 - 1886
(2017/09/25)
-
- Instantaneous Conversion of [11C]CO2 to [11C]CO via Fluoride-Activated Disilane Species
-
The development of a fast and novel methodology to generate carbon-11 carbon monoxide ([11C]CO) from cyclotron-produced carbon-11 carbon dioxide ([11C]CO2) mediated by a fluoride-activated disilane species is described. This methodology allows up to 74 % conversion of [11C]CO2 to [11C]CO using commercially available reagents, readily available laboratory equipment and mild reaction conditions (room temperature). As proof of utility, radiochemically pure [carbonyl-11C]N-benzylbenzamide was successfully synthesized from produced [11C]CO in up to 74 % radiochemical yield (RCY) and >99 % radiochemical purity (RCP) in ≤10 min from end of [11C]CO2 delivery.
- Taddei, Carlotta,Bongarzone, Salvatore,Gee, Antony D.
-
supporting information
p. 7682 - 7685
(2017/06/06)
-
- Gold(i)-catalyzed C-glycosylation of glycosyl: Ortho -alkynylbenzoates: The role of the moisture sequestered by molecular sieves
-
C-Glycosylation of glycosyl ortho-hexynylbenzoates with allyltrimethylsilane or silyl enol ethers could proceed smoothly under the catalysis of Ph3PAuNTf2 to provide the corresponding C-glycosides in high yields and stereoselectivity, wherein the moisture sequestered by the molecular sieves was disclosed to play a critical role in the gold(i)-catalytic cycle.
- Chen, Xiaoping,Wang, Qiaoling,Yu, Biao
-
supporting information
p. 12183 - 12186
(2016/10/21)
-
- Scope and selectivity of B(C6F5)3-catalyzed reactions of the disilane (Ph2SiH)2
-
The diverse catalytic activity of the electrophilic borane B(C6F5)3 in reactions of silanes with organic substrates has been exploited extensively in studies that mostly focus on very particular, useful functional group transformations in organic synthesis. This study examines the potential for harnessing the collective, broad scope of these transformations in the preparation of new oligosilane derivatives. Borane-catalyzed hydrosilation, heterodehydrogenative coupling, and dealkylative coupling reactions of a wide range of substrates with the disilane (Ph2SiH)2 were investigated. These allowed new mono- and disubstituted disilanes to be prepared that contain Si-O, Si-S, and Si-C linkages. Challenges and opportunities are described that arise from competing "over-reduction" chemistry, and the sensitivity of the catalysis to both the Lewis basicity and steric bulk of the substrates is examined.
- Lee, Peter T.K.,Rosenberg, Lisa
-
-
- Pinacol couplings of a series of aldehydes and ketones with SmI2/Sm/Me3SiCl in DME
-
The pinacol coupling is one of the most significant methods to synthesize vic-diols. The combination of samarium diiodide (SmI2) and samarium metal successfully induces the selective pinacol couplings of not only aromatic aldehydes and ketones but also aliphatic ones in the presence of trimethylchlorosilane (Me3SiCl) in 1,2-dimethoxyethane (DME). DME is the most suitable solvent for the reduction system using SmI2 and Me3SiCl. Me3SiCl, a widely available additive, prevents the decomposition of the formed vic-diols, i.e., meso-isomers, and controls their stereochemistry. In particular, the pinacol couplings of sterically hindered aliphatic aldehydes and ketones proceed with excellent diastereoselectivities to afford dl-isomers in good yields.
- Yoshimura, Aya,Saeki, Tomokazu,Nomoto, Akihiro,Ogawa, Akiya
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p. 5347 - 5355
(2015/07/15)
-
- Silicone wastes as reducing agents for carbon dioxide transformation: Fluoride-catalyzed formic acid synthesis from CO2, H2O, and disilanes
-
Disilanes were found to be reactive reducing agents for the transformation of carbon dioxide to formic acid in the presence of H2O. The reaction is catalyzed by fluoride salts such as tetrabutylammonium fluoride. Isotopic experiments revealed that the proposed reaction pathway includes Si-Si bond cleavage to afford hydrosilane followed by the hydrosilylation of CO2, and, finally, the hydrolysis of silyl formate.
- Motokura, Ken,Naijo, Masaki,Yamaguchi, Sho,Miyaji, Akimitsu,Baba, Toshihide
-
supporting information
p. 1464 - 1466
(2015/11/24)
-
- Nonhydrolytic synthesis of silanols by the hydrogenolysis of benzyloxysilanes
-
The hydrogenolysis of benzyloxysilanes was smoothly catalyzed by Pd/C in THF to give corresponding silanols under nonhydrolytic conditions. The reaction proved to be applicable to various benzyloxysilanes giving silanemonools, diol, and triol.
- Igarashi, Masayasu,Matsumoto, Tomohiro,Sato, Kazuhiko,Ando, Wataru,Shimada, Shigeru
-
supporting information
p. 429 - 431
(2014/04/17)
-
- Efficient fluoride-catalyzed conversion of CO2 to CO at room temperature
-
A protocol for the efficient and selective reduction of carbon dioxide to carbon monoxide has been developed. Remarkably, this oxygen abstraction step can be performed with only the presence of catalytic cesium fluoride and a stoichiometric amount of a disilane in DMSO at room temperature. Rapid reduction of CO2 to CO could be achieved in only 2 h, which was observed by pressure measurements. To quantify the amount of CO produced, the reduction was coupled to an aminocarbonylation reaction using the two-chamber system, COware. The reduction was not limited to a specific disilane, since (Ph 2MeSi)2 as well as (PhMe2Si)2 and (Me3Si)3SiH exhibited similar reactivity. Moreover, at a slightly elevated temperature, other fluoride salts were able to efficiently catalyze the CO2 to CO reduction. Employing a nonhygroscopic fluoride source, KHF2, omitted the need for an inert atmosphere. Substituting the disilane with silylborane, (pinacolato)BSiMe2Ph, maintained the high activity of the system, whereas the structurally related bis(pinacolato)diboron could not be activated with this fluoride methodology. Furthermore, this chemistry could be adapted to 13C-isotope labeling of six pharmaceutically relevant compounds starting from Ba13CO 3 in a newly developed three-chamber system.
- Lescot, Camille,Nielsen, Dennis U.,Makarov, Ilya S.,Lindhardt, Anders T.,Daasbjerg, Kim,Skrydstrup, Troels
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p. 6142 - 6147
(2014/05/20)
-
- Possibilities of using trimethylpentaphenyltrisiloxane as coolant for removing low-potential heat
-
The resistance of commercial trimethylpentaphenyltrisiloxane to heat and to thermal oxidation was studied. The limits of its use as coolant in systems for removing low-potential heat were determined. Instrumental methods were developed and tested for moni
- Lebedev,Sheludyakov,Storozhenko,Gurskii,Tsapko, Yu. V.,Yasnev,Egorov,Osetrova
-
p. 1529 - 1535
(2015/02/05)
-
- DISILOXANE COMPOUNDS AND THEIR USES
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A disiloxane having the following structure. Formula (I), Where R1, R3, R4 and R5 are each independently selected from monovalent hydrocarbon radicals having 1 to 4 carbon atoms, aryl, and a hydrocarbon group of 6 to 20 carbon atoms containing an aryl group; R2 is selected from a branched or linear hydrocarbon group of 7 to 15 carbons, a substituted branched or substituted linear hydrocarbon group of 7 to 15 carbons an optionally substituted aryl group, and an alkyl hydrocarbon chain of 4 to 9 carbons having one or more aryl substituents of 6 to 20 carbon atoms or a branched or linear hydrocarbon group of 1 to 6 carbons when R1 and R3 are independently an aryl group, or a hydrocarbon group of 6 to 20 carbon atoms containing an aryl group; Z is a linear or branched divalent hydrocarbon radical of from 2 to 10 (inclusive) carbon atoms and R8 is selected from OH, H, monovalent hydrocarbon radicals of from 1 to 6 carbon atoms and acetyl and each of the subscripts a, b and c are zero or positive provided that a + b + c ≥ 1.
- -
-
Paragraph 0040
(2014/05/24)
-
- Supported gold nanoparticle-catalyzed cis -selective disilylation of terminal alkynes by σ disilanes
-
Supported gold nanoparticles on metal oxides (1 mol %) catalyze for the first time the cis-selective disilylation of terminal alkynes by 1,2-disilanes in isolated yields up to 94%. It is likely that the reaction proceeds through oxidative insertion of the
- Gryparis, Charis,Kidonakis, Marios,Stratakis, Manolis
-
p. 6038 - 6041
(2014/01/06)
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- Catalytic synthesis of silyl formates with 1 atm of CO2 and their utilization for synthesis of formyl compounds and formic acid
-
In the presence of simple Rh2(OAc)4 and K 2CO3, the hydrosilylation of CO2 (1 atm) with various hydrosilanes efficiently proceeded to afford the corresponding silyl formates in moderate to high yields (53-90% yields). By using the dimethylphenylsilyl formate produced by the hydrosilylation, formamides, formic acid, and a secondary alcohol (via an aldehyde) could be synthesized by the reaction with various nucleophilic reagents such as amines, aniline, water, and the Grignard reagent.
- Itagaki, Shintaro,Yamaguchi, Kazuya,Mizuno, Noritaka
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p. 347 - 352
(2013/02/22)
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- Copper-catalyzed formic acid synthesis from CO2 with hydrosilanes and H2O
-
A copper-catalyzed formic acid synthesis from CO2 with hydrosilanes has been accomplished. The Cu(OAc)2?H 2O-1,2-bis(diphenylphosphino)benzene system is highly effective for the formic acid synthesis under 1 atm of CO2. The TON value approached 8100 in 6 h. The reaction pathway was revealed by in situ NMR analysis and isotopic experiments.
- Motokura, Ken,Kashiwame, Daiki,Miyaji, Akimitsu,Baba, Toshihide
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experimental part
p. 2642 - 2645
(2012/08/13)
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- An efficient method for the synthesis of symmetrical disiloxanes from alkoxysilanes using Meerwein's reagent
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We report here a new and efficient route to symmetrical disiloxanes from their corresponding alkoxysilanes using Meerwein's reagent as mediator and potassium carbonate as additive under mild reaction conditions in acetonitrile. Our methodology is very simple, economic, and high yielding. We have also proposed a reaction mechanism with the plausible silyloxonium intermediates. Georg Thieme Verlag Stuttgart · New York.
- Jorapur, Yogesh R.,Shimada, Toyoshi
-
supporting information; experimental part
p. 1633 - 1638
(2012/08/07)
-
- Metal-catalyzed reduction of HCONR'2, R' = Me (DMF), et (DEF), by silanes to produce R'2NMe and disiloxanes: A mechanism unraveled
-
We demonstrate that using Mo(CO)6, Mo(CO)5NMe 3, and (η5-C5H5)Mn(CO) 3 as catalysts for the silane, R3SiH, reduction of N,N-dimethylformamide (DMF), and N,N-diethylformamide (DEF), we can observe, intercept, and isolate, the important siloxymethylamine intermediates, R 3SiOCH2NR'2, R' = Me, Et, for the first time. In the presence of excess DMF such intermediates thermally react with a variety of silanes to form the corresponding disiloxanes in the absence of a metal catalyst. We also show that the germanium hydrides, Et3GeH and Bu3GeH, also reduce DMF to form trimethylamine and the corresponding digermoxane but observe no intermediates R3GeOCH2NMe 2. Bu3SnH reduces DMF, but along with the low yields of Bu3SnOSnBu3 (but no Bu3SnOCH 2NMe2) significant side products are obtained including (Bu3Sn)2 and Bu4Sn. In the absence of DMF the siloxymethylamines can undergo metal-catalyzed reactions with silanes, germanes and stannanes to form disiloxanes, and R3SiOER3 E = Ge, Sn, respectively. To date, the most efficient catalyst for this latter process is (η5-C5H5)Mo(CO)3CH 3 via a photochemical reaction.
- Arias-Ugarte, Renzo,Sharma, Hemant K.,Morris, Andrew L.C.,Pannell, Keith H.
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scheme or table
p. 848 - 851
(2012/03/07)
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- Gold nanoparticles-catalyzed activation of 1,2-disilanes: Hydrolysis, silyl protection of alcohols and reduction of tert-benzylic alcohols
-
Gold nanoparticles supported on TiO2 catalyze under mild conditions the activation of a series of 1,2-disilanes towards hydrolysis and alcoholysis, with concomitant evolution of H2 gas. For the case of tert-benzyl alcohols, the main or only pathway is reduction to the corresponding alkanes.
- Gryparis, Charis,Stratakis, Manolis
-
p. 10751 - 10753,3
(2020/09/02)
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- An efficient and simple method for the preparation of symmetrical disiloxanes from hydrosilanes by Lewis acid-catalyzed air oxidation
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Symmetrical disiloxanes were prepared in high yields by air oxidation of mono, di, and trihydrosilanes under Lewis acid catalysis.
- Sridhar, Madabhushi,Ramanaiah, Beeram China,Narsaiah, Chinthala,Kumara Swamy, Mudam,Mahesh, Bellam,Kumar Reddy, Mallu Kishore
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experimental part
p. 7166 - 7168
(2010/02/27)
-
- Supported gold nanoparticle catalyst for the selective oxidation of silanes to silanols in water
-
Hydroxyapatite-supported gold nanoparticles (AuHAP) can act as highly efficient and reusable catalysts for the oxidation of diverse silanes into silanols in water; this is the first catalytic methodology for the selective synthesis of aliphatic silanols using water under organic-solvent-free conditions.
- Mitsudome, Takato,Noujima, Akifumi,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
-
supporting information; experimental part
p. 5302 - 5304
(2010/01/31)
-
- Catalysis by cationic oxorhenium(v): Hydrolysis and alcoholysis of organic silanes
-
The cationic [2-(2′-hydroxyphenyl)-2-oxazolinato(-2)]oxorhenium(v) complex 1 promotes oxidative dehydrogenation of organosilanes with water and alcohols in a catalytic manner to give excellent yields of silanols and silyl ethers, respectively. The reactions proceed conveniently under ambient and open-flask conditions with low catalyst loading (≤1 mol%). The scope of the reaction with water is quite broad and includes aliphatic, aromatic, tertiary, secondary and primary silanes. The rate of reaction depends on the catalyst and silane concentrations and kinetic isotope effect measurements demonstrate involvement of the Si-H bond in the activated complex. The most influential factor on the silane affecting reactivity is steric hindrance and a quantitative correlation with the Taft steric parameter (E) is presented. A combination of kinetic data and isotope labelling results are used to discuss plausible mechanisms for the oxidative dehydrogenation reaction pathway.
- Corbin, Rex A.,Ison, Elon A.,Abu-Omar, Mahdi M.
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experimental part
p. 2850 - 2855
(2009/06/27)
-
- A higher yielding route to octasilsesquioxane cages using tetrabutylammonium fluoride, Part 2: Further synthetic advances, mechanistic investigations and X-ray crystal structure studies into the factors that determine cage geometry in the solid state
-
The recently-reported reaction of triethoxysilanes with tetrabutylammonium fluoride in the presence of scarce water provides a higher yielding route to substituted octasilsesquioxane cages. Further cages have now been prepared in good yield using this route and their X-ray crystal structures demonstrate that their cage geometries in the solid state are very similar with the packing constraints of the crystal lattices appearing to have the greatest influence on the geometry of the cage core. The mechanism of the reaction has been examined and the proposed mechanism of cage formation validated, though its exclusivity has not been categorically proven. By careful choice of reaction conditions, dramatic increases in rate and yield have been demonstrated.
- Bassindale, Alan R.,Chen, Huiping,Liu, Zhihua,MacKinnon, Iain A.,Parker, David J.,Taylor, Peter G.,Yang, Yuxing,Light, Mark E.,Horton, Peter N.,Hursthouse, Michael B.
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p. 3287 - 3300
(2007/10/03)
-
- A facile synthesis of 1,1-disilylethenes via Me3MgLi-induced monomethylation of dibromodisilylmethanes
-
Lithium trimethylmagnesate (Me3MgLi) induces monomethylation of dibromodisilylmethanes in excellent yields. Subsequent dehydrobromination of the resulting 1-bromo-1,1-disilylethanes with DBU affords 1,1-disilylethenes in good yields.
- Inoue, Atsushi,Kondo, Junichi,Shinokubo, Hiroshi,Oshima, Koichiro
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p. 956 - 957
(2007/10/03)
-
- Electrochemical Reduction of Dichlorosilanes in the Presence of 2,3-Dimethylbutadiene
-
Electrolytic reduction of dichloromethylphenyl-, dichlorodiphenyl-, dichloro-o-tolyl-, and dichlorodi-p-tolylsilanes in the presence of 2,3-dimethylbutadiene afforded 1-methyl-1-phenyl-, 1,1-diphenyl-, 1,1-di-o-tolyl-, and 1,1-di-p-tolyl-3,4-dimethyl-1-silacyclopent-3-ene, respectively, while the similar reaction of chloromethyldiphenylsilane with 2,3-dimethylbutadiene afforded 1-(methyldiphenylsilyl)- and 1,4-bis(methyldiphenylsilyl)-2,3-dimethyl-2-butene.A reaction mechanism leading to these products has been discussed.
- Kunai, Atsutaka,Ueda, Takafumi,Toyoda, Eiji,Ishikawa, Mitsuo
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p. 287 - 289
(2007/10/02)
-
- Electrochemical Oxidation of Hydrosilanes. A Synthetic Approach to Halosilanes and Disilanes
-
Electrolytic oxidation of dimethylphenylsilane (1) in the presence of CuCl2 or CuCl afforded chlorodimethylphenylsilane in high yields (>90percent), while similar electrolysis of 1 in the presence of BF4- ions afforded fluorodimethylphenylsilane in 90percent yield. 1,2-Diphenyltetramethyldisilane was obtained from 1 in 48percent yield by the electrolysis with a Pt-Cu electrode system.A "paired" electrolysis of methyldiphenylsilane on the anode and chloromethyldiphenylsilane on the cathode afforded 1,2-dimethyltetraphenyldisilane in 64percent yield.
- Kunai, Atsutaka,Kawakami, Toshihiro,Toyoda, Eiji,Sakurai, Tomohiro,Ishikawa, Mitsuo
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p. 1945 - 1948
(2007/10/02)
-
- Electrochemical Halogenation of Trisubstituted Germanes and Silanes
-
Electrochemical halogenation of trisubstituted germanes and silanes in acetonitrile occured in the cathode compartment in contrast to the well-known electrochemical halogenations which always occur in the anode compartment.
- Okano, Mitsutoshi,Mochida, Kunio
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p. 1381 - 1382
(2007/10/02)
-
- Synthesis of siloxanes. XVII. Increment system for prediction of 17O NMR shifts of siloxanes
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17O NMR data have been obtained for a series of siloxanes and an incremental system derived for predicting the 17O shift of variously-substituted siloxanes.
- Scheim, U.,Ruehlmann, K.,Kelly, J. W.,Evans, S. A.
-
-
- Determination of Reactive Components in Silicone Foams
-
Analytical methods have been developed for the determination of reactive components used in the formulation of room temperature vulcanized (RTV) sislicone foams.The reactive components include total silanol (SiOH), silane hydrogen (SiH), tetrapropoxysilane (TPS), and diphenylmethylsilanol (DPMS).Total SiOH and SiH are determined by Fourier transform infrared (FTIR) spectrometry. the SiOH peak at 3687 cm-1 and the SIH peak at 2168 cm-1 were used for quantitation.The TPS content was determined by gas chromatography (GC), using a solid capillary open tubular (SCOT) column and linear programmed temperature control.The DPMS content was determined by gel permeation chromatography (GPC) using THF solvent.
- Dubiel, S. V.,Griffith, G. W.,Long, C. L.,Baker, G. K.,Smith, Robert E.
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p. 1533 - 1537
(2007/10/02)
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- Process for the preparation of alkyl and aryl substituted oligosiloxanes suitable for use as diffusion pump oils
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An improved process for preparing 1,3-dialkyl-1,1,3,3-tetraryldisiloxanes and 1,3,5-trialkyl-1,1,3,5,5-pentaaryltrisiloxanes is disclosed. The process utilizes an aryl Grignard reagent to affect displacement of alkoxy, preferably methoxy, groups in the corresponding alkyl-alkoxy substituted di-, and trisiloxanes. Alternatively, partial replacement of the alkoxy groups in an alkyltrialkoxysilane with aryl groups in a Grignard reaction, and subsequent hydrolyis of the remaining alkoxy groups yield the above-noted desired compounds.
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