- How a Thermally Unstable Metal Hydrido Complex Can Yield High Catalytic Activity Even at Elevated Temperatures
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Despite their instability in ethereal solvents, organotitanium hydride catalysts are successfully employed in catalysis at moderate to high temperatures (110 °C), even in the presence of alcohols. It is shown computationally (bond dissociation energy (BDE) analysis and energetic profile for regeneration) and experimentally (EPR studies and kinetic studies), with the specific example of hydrodefluorination (HDF), that despite the long standing belief, regeneration of Ti?H bonds from Ti?F bonds using silanes is endergonic. The resulting low concentration of Ti?H species is crucial for the catalytic stability of those systems. The resting state in the catalysis is a Ti?F species. The most promising silanes for regeneration are not the ones that have the strongest Si?F bond, but the ones that show the largest difference in Si?F and Si?H BDEs.
- Ehm, Christian,Krüger, Juliane,Lentz, Dieter
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Read Online
- Sustainable Catalytic Synthesis of Diethyl Carbonate
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New sustainable approaches should be developed to overcome equilibrium limitation of dialkyl carbonate synthesis from CO2 and alcohols. Using tetraethyl orthosilicate (TEOS) and CO2 with Zr catalysts, we report the first example of sustainable catalytic synthesis of diethyl carbonate (DEC). The disiloxane byproduct can be reverted to TEOS. Under the same conditions, DEC can be synthesized using a wide range of alkoxysilane substrates by investigating the effects of the number of ethoxy substituent in alkoxysilane substrates, alkyl chain, and unsaturated moiety on the fundamental property of this reaction. Mechanistic insights obtained by kinetic studies, labeling experiments, and spectroscopic investigations reveal that DEC is generated via nucleophilic ethoxylation of a CO2-inserted Zr catalyst and catalyst regeneration by TEOS. The unprecedented transformation offers a new approach toward a cleaner route for DEC synthesis using recyclable alkoxysilane.
- Putro, Wahyu S.,Ikeda, Akira,Shigeyasu, Shinji,Hamura, Satoshi,Matsumoto, Seiji,Lee, Vladimir Ya.,Choi, Jun-Chul,Fukaya, Norihisa
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p. 842 - 846
(2020/12/07)
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- Mechanochemical method of producing triethoxysilane
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A mechanochemical method for synthesis of triethoxysilane from silicon-copper contact mass and ethyl alcohol in the developed vibration reactor is presented. It is shown that the process of a direct alkoxysilane synthesis in the vibro-boiling layer is affected by a series of control parameters such as the ratio between the contact mass and the mass of grinding bodies, the grinding body sizes and their ratios in a polydisperse mixture, power density. Optimization of these parameters allowed us to obtain HSi(OEt)3 with a selectivity of 50% at a silicon conversion of 90% without the use of promoters.
- Temnikov,Anisimov,Chistovalov,Zhemchugov,Kholodkov,Zimovets,Vysochinskaya, Yu. S.,Muzafarova
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p. 270 - 274
(2019/04/27)
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- Calyciphylline B-Type Alkaloids: Total Syntheses of (-)-Daphlongamine H and (-)-Isodaphlongamine H
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The first total synthesis of the complex hexacylic Daphniphyllum alkaloid (-)-daphlongamine H has been accomplished. Key to the success of the strategy are a complexity-building Mannich reaction, efficient cyclizations, and a highly diastereoselective hydrogenation to assemble multigram quantities of the tricyclic core bearing four contiguous stereocenters. Following construction of the hydro-indene substructure by means of a Pauson-Khand reaction, endgame redox manipulations delivered the natural product. Importantly, the synthetic studies have also given access to (-)-isodaphlongamine H and led to a revision of the reported structure of deoxyisocalyciphylline B.
- Hugelshofer, Cedric L.,Palani, Vignesh,Sarpong, Richmond
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supporting information
p. 8431 - 8435
(2019/06/13)
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- METHOD FOR PRODUCING HYDROSILANE
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PROBLEM TO BE SOLVED: To provide a method for producing hydrosilane capable of efficiently producing hydrosilane under mild conditions. SOLUTION: Provided is a method for producing hydrosilane where hydrosilane can be efficiently produced by reacting alkoxysilane having a structure represented by formula (a) with hydroborane and/or hydrogen under the presence of a complex with at least one kind of atom selected from the group consisting of a yttrium atom (Y), a zirconium atom (zr) and a hafnium atom (Hf) as a central metal(s)(in the formula (a), R denotes a 1 to 20C hydrocarbon group). SELECTED DRAWING: None COPYRIGHT: (C)2018,JPO&INPIT
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Paragraph 0026
(2019/01/06)
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- Mechanochemistry-a new powerful green approach to the direct synthesis of alkoxysilanes
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The present work shows a new one-stage mechanochemical method for the direct synthesis of alkoxysilanes by silicon mechanoactivation followed by a reaction with an alcohol. Alkoxysilanes were obtained with nearly complete silicon and alcohol conversion. This method allows for a considerable simplification of the traditional multistage process by eliminating three stages that include silicon and catalyst preparation, and adapts it to green chemistry requirements. Vibration milling removed the oxide film, and the mechanoactivation of the large silicon fraction (1000-2000 μm) occurs in the reactor working space. Abrasion of the reactor walls and grinding bodies made of brass results in a developed catalytic surface on silicon, as it has been proven by a set of physical analytical methods such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (PXRD), and X-ray photoelectron spectroscopy (XPS).
- Temnikov, Maxim N.,Anisimov, Anton A.,Zhemchugov, Pavel V.,Kholodkov, Dmitry N.,Goloveshkin, Alexander S.,Naumkin, Alexander V.,Chistovalov, Sergey M.,Katsoulis, Dimitris,Muzafarov, Aziz M.
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supporting information
p. 1962 - 1969
(2018/05/23)
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- New vinyl alkoxy silane preparation process
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The present invention discloses a new vinyl alkoxy silane preparation process, which is characterized in that hydrogen chloride produced during a preparation process is adopted as a reactant to synthesize an initial raw material trichlorosilane, the hydrogen chloride is recycled, and the byproduct bis(trialkoxy)silyl ethane is adopted as a reaction solvent during a hydrogen silicon addition process, such that the byproduct emission is reduced, the new impurity introduction is avoided, and the product purity is improved. According to the present invention, the new process has characteristics of stable production, simple preparation process, and mild reaction conditions, and the yield of the product vinyl alkoxy silane is high, and the product purity is more than 99%.
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Paragraph 0041; 0042
(2016/10/08)
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- METHOD FOR HYDROGENATING SILANE COMPOUND
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In the present invention, provided is a method for hydrogenating silane compounds, comprising the steps of supplying hydrogen to a low-temperature plasma reaction apparatus and accordingly generating low-temperature plasmas including hydrogen ions, electrons and hydrogen atom radicals; supplying raw materials including the silane compound to the low-temperature plasma reaction apparatus; and making the silane compound, the hydrogen ion, the electrons and the hydrogen atom radical have the hydrogenating reaction.
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Paragraph 0086 - 0095
(2016/12/12)
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- Amorphous silicon: New insights into an old material
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Amorphous silicon is synthesized by treating the tetrahalosilanes SiX4 (X=Cl, F) with molten sodium in high boiling polar and non-polar solvents such as diglyme or nonane to give a brown or a black solid showing different reactivities towards suitable reagents. With regards to their technical relevance, their stability towards oxygen, air, moisture, chlorine-containing reaction partners RCl (R=H, Cl, Me) and alcohols is investigated. In particular, reactions with methanol are a versatile tool to deliver important products. Besides tetramethoxysilane formation, methanolysis of silicon releases hydrogen gas under ambient conditions and is thus suitable for a decentralized hydrogen production; competitive insertion into the MeO-H versus the Me-OH bond either yields H- and/or methyl-substituted methoxy functional silanes. Moreover, compounds, such as MenSi(OMe)4-n (n=0-3) are simply accessible in more than 75% yield from thermolysis of, for example, tetramethoxysilane over molten sodium. Based on our systematic investigations we identified reaction conditions to produce the methoxysilanes MenSi(OMe)4-n in excellent (n=0:100%) to acceptable yields (n=1:51%; n=2:27%); the yield of HSi(OMe)3 is about 85%. Thus, the methoxysilanes formed might possibly open the door for future routes to silicon-based products. Amorphous silicon is easily synthesized from tetrahalosilanes SiX4 (X=Cl, F) and molten sodium in different solvents. Reactivity studies prove the resulting materials as versatile tools for the formation of technical important silanes, such as the silicon chloro-, alkoxy-, and methylalkoxy-substituted derivatives (see figure; bl=black, br=brown).
- Spomer, Natalie,Holl, Sven,Zherlitsyna, Larissa,Maysamy, Fariba,Frost, Andreas,Auner, Norbert
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p. 5600 - 5616
(2015/03/30)
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- METHOD FOR PREPARING TRIALKOXYSILANE
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The present invention relates to a method for preparing SiH(OR3)-type trialkoxysilane (wherein, R is a C1-C3 methyl, ethyl, propyl or isopropyl group), and more specifically, the method comprises the steps of: preventing the oxidation of a silicon surface by pulverizing raw silicon material in a solvent environment without contact with the air so that the initial induction period of the direct synthesis of trialkoxysilane is dramatically reduced; and removing impurities from a reaction environment by continuously selecting a part of the solvent through a membrane filter provided in a reactor body.
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Paragraph 0062
(2014/07/23)
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- METHOD FOR PREPARING TRIALKOXYSILANE
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The present invention relates to a method for preparing SiH(OR3)-type trialkoxysilane (wherein, R is a C1-C3 methyl, ethyl, propyl or isopropyl group), and more specifically, the method comprises the steps of: preventing the oxidation of a silicon surface by pulverizing raw silicon material in a solvent environment without contact with the air so that the initial induction period of the direct synthesis of trialkoxysilane is dramatically reduced; and removing impurities from a reaction environment by continuously selecting a part of the solvent through a membrane filter provided in a reactor body.
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Paragraph 0100
(2015/01/06)
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- Nonhydrolytic synthesis of branched alkoxysiloxane oligomers Si[OSiH(OR)2]4 (R = Me, Et)
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Beyond silanol: A branched siloxane oligomer bearing terminal dialkoxysilyl groups was nonhydrolytically synthesized by direct alkoxysilylation of a tetraalkoxysilane with a chlorodialkoxysilane in the presence of the Lewis acid BiCl3 (see scheme). The reaction proceeds without the formation of intermediate silanol groups, and provides a selective route for siloxane-based oligomers. (Chemical equation presented)
- Wakabayashi, Ryutaro,Kawahara, Kazufumi,Kuroda, Kazuyuki
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supporting information; experimental part
p. 5273 - 5277
(2010/10/21)
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- Process for preparation of alkoxysilanes
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Alkoxysilanes are prepared by a process which uses microwave or RF energy. Thus, silicon metal and a copper catalyst are exposed to microwave radiation in the presence of an appropriate hydroxy compound, such as, an alcohol, and a catalyst, to yield the corresponding trialkoxysilane. The desired alkoxysilanes are prepared with high selectivity and at lower temperatures and shorter times than traditional approaches allow.
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Page/Page column 5
(2008/12/05)
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- Process for the direct synthesis of trialkoxysilane
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This invention discloses a process to improve reaction stability in the Direct Synthesis of trialkoxysilanes. The process is particularly effective in the Direct Synthesis of triethoxysilane and its higher alkyl cognates providing improved triethoxysilane yields.
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Page/Page column 19
(2008/06/13)
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- Method for making triorganooxysilanes
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A method for the preparation of triorganooxysilanes containing one silicon-hydrogen bond is provided which comprises reacting at least one tetraorganooxysilane with at least one metal hydride.
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- Direct synthesis of alkyldialkoxysilanes by the reaction of silicon, alcohol and alkene using a high-pressure flow reactor
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In the reaction of silicon, methanol and ethylene, use of a high-pressure flow reactor operating at 240°C at 0.86 MPa of ethylene and 0.18 MPa of methanol gave a 33% selectivity for ethyldimethoxysilane, which was much higher than that using an atmospheric-pressure flow reactor (8%) or using an autoclave (4%). The selectivity increased proportionally with the ethylene pressure below 0.5 MPa. This indicates that the addition of ethylene or methanol to a surface silylene intermediate determines the selectivity and that the ethylene addition is a first-order reaction. Above 0.5 MPa the slope of the selectivity change was smaller. By feeding propylene instead of ethylene, n- and iso-propyldimethoxysilanes were obtained as organosilanes with 15 and 2% of selectivity, respectively. The reaction of silicon, ethanol and ethylene resulted in 28% selectivity for ethyldiethoxysilane at 0.99 MPa of ethylene and 0.21 MPa of ethanol at 240°C.
- Okamoto, Masaki,Komai, Jun-Ichi,Uematsu, Miwa,Suzuki, Eiichi,Ono, Yoshio
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p. 235 - 240
(2007/10/03)
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- Direct synthesis of methyldimethoxysilane from metallic silicon and methanol using copper(I) chloride catalyst
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When the reaction of metallic silicon with methanol in the presence of a small amount of thiophene was carried out at 653 K, methyldimethoxysilane was formed together with trimethoxysilane and tetramethoxysilane, the selectivity for methyldimethoxysilane being 22%. Further adding a small amount of trioxane, trimer of formaldehyde, to the reaction system improved the selectivity for methyldimethoxysilane. This indicates that formaldehyde formed by the dehydrogenation of methanol takes part in methyldimethoxysilane formation. The reaction of silicon with ethanol also gave a 14% selectivity of ethyldiethoxysilane with a 43% silicon conversion.
- Okamoto, Masaki,Abe, Hidenori,Kusama, Yukari,Suzuki, Eiichi,Ono, Yoshio
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- Symetrical hydroxyphenyl-s-triazine compositions
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The invention is concerned with compounds of formula I: STR1 which are useful as sun screening agents.
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- Process for preparing hydrogenalkoxysilanes
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Hydrogenalkoxysilanes are prepared by direct reaction of finely divided metallic silicon with alcohols in the presence of copper-containing catalysts in a heat-transfer oil comprising tritoluenes, tetratoluenes or mixtures thereof at from 100° to 350° C.
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- Process for producing trialkoxysilane
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A process for producing a trialkoxysilane comprising reacting metallic silicon and an alkyl alcohol having from 1 to 4 carbon atoms in the presence of a catalyst, in which the reaction is carried out in a gaseous phase in the presence of a halide. The process achieves a high selectivity of a trialkoxysilane and a high conversion of silicon while inhibiting formation of by-products. Where the process of the present invention is carried out in a fluidized bed system, a satisfactory fluid state can be maintained, and the reaction temperature can easily be controlled.
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- Vapor phase alcoholysis of aminosilanes and carbamatosilanes
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A vapor phase process for the synthesis of alkoxysilanes of the general formula HSi(OR' )x (R )3-x which comprises reacting (a) a silane of the general formula wherein R, R' and R are individually hydrogen or an aryl or alkyl group optionally containing unsaturation, each having from one to eight carbon atoms inclusive, and where R' may also be an alkoxy or carbamato group and where x has a value of from one to three; with (b) an alcohol of the general formula wherein R' is an aryl group, or an alkyl group optionally containing unsaturation, each having from one to twenty carbon atoms inclusive and optionally substituted said reaction taking place in the presence of (c) a catalyst in which both the silane and the alcohol are present in gaseous form in a stoichiometric ratio of 0.4 to 1.05 moles of alcohol per mole of silicon-nitrogen bonds and where said catalyst is present in an amount from 0.01 to 10 mole percent of the silicon-nitrogen bonds.
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- REDUCTION SELECTIVE DE COMPOSES CARBONYLES PAR CATALYSE HETEROGENE A LA SURFACE DES SELS
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The reduction of carbonyl compounds carried out with ethoxyhydrogenosilanes and alkali metal fluorides as catalysts and without solvent is highly selective.The reactivity order is aldehyde> ketone> ester.The reduction of aldehydes is possible in the presence of ketones, and of ketones in the presence of esters.The keto-group in a keto-ester can be selectively reduced.The high selectivity of this system is due to three factors: hydrogenosilane reactivity (EtO)2SiMeH (EtO)3SiH, nature of the salt (KFCsF) and temperature.Chlorides, amides, anhydrides and ethylenic, bromo, nitro groups are not reduced.This enables the selective reduction of the carbonyl group in bifunction compounds.
- Boyer, J.,Corriu, R. J. P.,Perz, R.,Reye, C.
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p. 2165 - 2172
(2007/10/02)
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- The direct synthesis of organic derivatives of silicon using nonhalogenated organic compounds
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Some trialkoxysilanes, (RO)3SiH (R = CH3, C2H5, n-C3H7, i-C4H9), and tetraalkoxysilanes were prepared directly by the reactions of the appropriate primary alcohol with a silicon-copper contact mixture. Similar attempts with secondary and tertiary alcohols, ethers, and secondary amines gave no silicon-containing products.
- Newton,Rochow
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p. 1071 - 1075
(2007/10/05)
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