- Semisynthetic Antimycobacterial C-3 Silicate and C-3/C-21 Ester Derivatives of Fusidic Acid: Pharmacological Evaluation and Stability Studies in Liver Microsomes, Rat Plasma, and Mycobacterium tuberculosis culture
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Fusidic acid (FA), a natural product fusidane triterpene-based antibiotic with unique structural features, is active in vitro against Mycobacterium tuberculosis, the causative agent of tuberculosis (TB). While possessing good pharmacokinetics in man, FA is rapidly metabolized in rodents, thus complicating proof-of-concept studies in this model. Toward the repositioning of FA as an anti-TB agent, we herein describe the synthesis, activity, and metabolism of FA and semisynthesized ester derivatives in rat liver microsomes, rat plasma, and mycobacterial cell culture. FA and derivative molecules with a free C-3 OH underwent species-specific metabolism to the corresponding 3-OH epimer, 3-epifusidic acid (3-epiFA). FA was also metabolized in rat plasma to form FA lactone. These additional routes of metabolism may contribute to the more rapid clearance of FA observed in rodents. C-3 alkyl and aryl esters functioned as classic prodrugs of FA, being hydrolyzed to FA in microsomes, plasma, and Mycobacterium tuberculosis culture. In contrast, C-3 silicate esters and C-21 esters were inert to hydrolysis and so did not act as prodrugs. The antimycobacterial activity of the C-3 silicate esters was comparable to that of FA, and these compounds were stable in microsomes and plasma, identifying them as potential candidates for evaluation in a rodent model of tuberculosis.
- Njoroge, Mathew,Kaur, Gurminder,Espinoza-Moraga, Marlene,Wasuna, Antonina,Dziwornu, Godwin Akpeko,Seldon, Ronnett,Taylor, Dale,Okombo, John,Warner, Digby F.,Chibale, Kelly
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- Synthesis of a 12-membered cyclic siloxane possessing alkoxysilyl groups as a nanobuilding block and its use for preparation of gas permeable membranes
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A 12-membered cyclic siloxane possessing alkoxysilyl groups was synthesized as a nanobuilding block for siloxane-based materials by the alkoxysilylation of organometallasiloxane containing a 12-membered ring with Si-Me and Si-O- groups as the side groups. The cyclic structure was retained not only in the hydrolysis and condensation reactions (sol-gel process) of the alkoxysilyl groups but also in the xerogel and membrane preparation processes. The degree of condensation of the xerogel derived from the 12-membered ring siloxane was higher than that derived from alkoxysilane monomers, indicating that the alkoxysilylated cyclic oligosiloxane is useful for controlling siloxane networks. A membrane composed of the cyclic siloxane was prepared by coating the hydrolyzed solution onto a porous alumina tube for evaluating the gas permeation properties. The membrane showed a molecular sieving effect for H2/SF6.
- Yoshikawa, Masashi,Shiba, Hiroya,Kanezashi, Masakoto,Wada, Hiroaki,Shimojima, Atsushi,Tsuru, Toshinori,Kuroda, Kazuyuki
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- Synthesis of triethoxysilanol
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Triethoxysilanol was isolated for the first time by hydrolysis of chloro(triethoxy)silane in an organic solvent in the presence of a heterogeneous base and identified as an individual compound. The synthesis of this compound made it possible to study its physicochemical properties and substantially extended its potentialities for the synthesis of hyperbranched polyethoxysiloxanes and functional oligomers.
- Kazakova,Gorbatsevich,Skvortsova,Demchenko,Muzafarov
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- Method for removing methyldichlorosilane and silicon tetrachloride impurities in trimethyl chlorosilane
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The invention relates to a method for removing methyldichlorosilane and silicon tetrachloride impurities in trimethyl chlorosilane, which comprises a hydrosilylation reaction, a partial esterification reaction and a complete esterification reaction. Firstly, a mixture of trimethylsilyl chloride containing methyldichlorosilane and silicon tetrachloride impurities is added to a reactor for hydrosilylation reaction, and the reaction product enters a separation system. The silicon tetrachloride in the mixture is partially esterified and reacted by adding the low-carbon alcohol as an esterifying agent, and the reaction product enters a separation system. Finally, the partially esterified product is further fully esterified to valuable tetraalkoxy silicon products. The high-efficiency recycling of trimethylchlorosilane is realized, and high-value utilization is also realized.
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Paragraph 0037-0038; 0042-0044; 0049; 0051-0052; 0063; ...
(2021/08/25)
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- Industrial synthesis method of triethoxychlorosilane
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The invention relates to the field of organic synthesis, aims to overcome the defects of high content of byproducts, low selectivity of triethoxychlorosilane and the like in preparation of triethoxychlorosilane by using triethoxysilane as a raw material and adopting a chlorination reaction, and provides a method for converting the triethoxysilane into the triethoxychlorosilane by using trichloroisocyanuric acid as a chlorination reagent and halogenated metal salt as an additive. The method for converting the triethoxysilane into the triethoxychlorosilane has the advantages of high conversion rate of the triethoxysilane, low content of byproducts, high selectivity of the triethoxychlorosilane and small separation load, and is particularly suitable for industrial preparation of the triethoxychlorosilane.
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Paragraph 0040-0077
(2021/05/05)
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- Synthesis of Polycyclic and Cage Siloxanes by Hydrolysis and Intramolecular Condensation of Alkoxysilylated Cyclosiloxanes
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The controlled synthesis of oligosiloxanes with well-defined structures is important for the bottom-up design of siloxane-based nanomaterials. This work reports the synthesis of various polycyclic and cage siloxanes by the hydrolysis and intramolecular condensation of monocyclic tetra- and hexasiloxanes functionalized with various alkoxysilyl groups. An investigation of monoalkoxysilylated cyclosiloxanes revealed that intramolecular condensation occurred preferentially between adjacent alkoxysilyl groups to form new tetrasiloxane rings. The study of dialkoxy- and trialkoxysilylated cyclotetrasiloxanes revealed multistep intramolecular condensation reactions to form cubic octasiloxanes in relatively high yields. Unlike conventional methods starting from organosilane monomers, intramolecular condensation enables the introduction of different organic substituents in controlled arrangements. So-called Janus cubes have been successfully obtained, that is, Ph4R4Si8O12, in which R=Me, OSiMe3, and OSiMe2Vi (Vi=vinyl). These findings will enable the creation of siloxane-based materials with diverse functions.
- Sugiyama, Tomoaki,Shiba, Hiroya,Yoshikawa, Masashi,Wada, Hiroaki,Shimojima, Atsushi,Kuroda, Kazuyuki
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p. 2764 - 2772
(2019/02/01)
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- Method of producing arylhalosilane alkoxyphthalocyanine (by machine translation)
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PROBLEM TO BE SOLVED: alkoxyphthalocyanine arylhalosilane compd. alkoxy halo silane can be efficiently manufactured to provide a novel method of producing and purpose. SOLUTION: arylhalosilane compd. alkylalkoxysilane compound having a functional group and in exchange reaction, by utilizing a bismuth halide (III), alkoxyphthalocyanine arylhalosilane compd. can be efficiently manufactured. Selected drawing: no (by machine translation)
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Paragraph 0015; 0021-0022; 0027
(2016/10/09)
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- Selective Formation of Alkoxychlorosilanes and Organotrialkoxysilane with Four Different Substituents by Intermolecular Exchange Reaction
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Alkoxychlorosilanes are scientifically and industrially important toward preparing silicone and silica as well as preparation of siloxane-based nanomaterials by stepwise reactions of Si?OR (R=alkyl) and Si?Cl groups. Intermolecular exchange of alkoxy and chloro groups between alkoxysilanes and chlorosilanes (functional group exchange reaction) provides an efficient and environmentally benign route to alkoxychlorosilanes. BiCl3 as a Lewis acid catalyst can promote the functional group exchange reactions more efficiently than conventional acid catalysts. Higher reactivity has been observed for chlorosilanes with smaller numbers of Si?CH3 groups and for alkoxysilanes with larger numbers of Si?CH3 groups. The reaction mechanism is proposed and selective syntheses of alkoxychlorosilanes are demonstrated. These findings also enable us to synthesize an organotrialkoxysilane with four different substituents.
- Komata, Yuma,Yoshikawa, Masashi,Tamura, Yasuhiro,Wada, Hiroaki,Shimojima, Atsushi,Kuroda, Kazuyuki
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p. 3225 - 3233
(2016/11/29)
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- Mechanistic insights into the hydrosilylation of allyl compounds - Evidence for different coexisting reaction pathways
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The hydrosilylation of allyl compounds is often accompanied by the formation of high amounts of byproducts. The formation processes have not been fully understood so far. In this work, the allyl hydrosilylation mechanism is investigated in detail and experimental and theoretical evidence for multiple, coexisting reaction pathways is provided. Based on earlier reports and the observations during an extensive catalytic study, different pathways, leading to the observed byproducts, were identified and proven by labeling experiments and DFT calculations. Oxidative addition of the silane and the insertion of the allyl compound into the Pt-H bond turned out to be the crucial, selectivity-determining steps within the catalytic cycle. Based on these findings, it should be possible to systematically influence these steps and pave the way to a rational and straightforward design of more selective catalysts.
- Gigler, Peter,Drees, Markus,Riener, Korbinian,Bechlars, Bettina,Herrmann, Wolfgang A.,Kuehn, Fritz E.
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- Ethylene polymerization reactions with multicenter Ziegler-Natta catalysts-manipulation of active center distribution
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This article describes ethylene/1-hexene copolymerization reactions with a supported titanium-based, multicenter Ziegler-Natta catalyst. The catalyst was modified by pretreating its solid precursor with AlEt2Cl and with similar organoaluminum chlorides, Al2Et3Cl3, AlEtCl2, and AlMe2Cl. Testing of the untreated and the pretreated catalysts in copolymerization reactions under standard reaction conditions demonstrated that the modifying agents produce two changes in the catalyst. First, the pretreatment significantly reduces the reactivity of active centers that produce high molecular weight, highly crystalline copolymer components with a low 1-hexene content. Second, the pretreatment noticeably increases the reactivity of active centers that produce low molecular weight copolymer components with a high 1-hexene content. The first effect is caused by Lewis acidbase interactions of the modifiers with the active centers, whereas the second (activating) effect is due to the removal of catalyst poisons (organosilicon compounds generated in the process of the catalyst synthesis) by AlEt2Cl.
- Kissin, Yury V.,Mink, Robert I.
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scheme or table
p. 4219 - 4229
(2011/12/15)
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- PROCESS FOR THE PREPARATION OF HALOALKYLALKOXYSILANCS AND HALOALKYLHALOSILANES
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This invention involves a process for the preparation of haloalkylalkoxysilanes and haloalkylhalosilancs. The process comprises reacting an alkoxyhydridosilane or a halohydridosilanc silane with an alkenylhalide compound in the presence of a catalytic amount of an iridium containing catalyst. When a halohydridosilane is the silane rcactant. the resulting haloalkylhalosilane may be alkoxylatcd by reaction with a C1-C6, alcohol, In another aspect of the invention, the reacting is conducted under a reduced oκygen atmosphere to improve the catalyst activity and the yield of the resulting haloalkylhalosilane or halυalkylalkυx vsi lane.
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Page/Page column 17-19
(2009/10/22)
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- Utility of trichloroisocyanuric acid in the efficient chlorination of silicon hydrides
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The potential of trichloroisocyanuric acid (TCCA) as a chlorination agent for efficient conversion of Si-H functional silanes and siloxanes to the corresponding Si-Cl functional moieties was explored. In comparison to methods using other chlorinating agents, TCCA is inexpensive, results in a much faster reaction and produces a high purity product with a conversion that is essentially quantitative. A variety of chloro derivatives of linear and cyclic structures have been synthesized from silicon hydrides using this reagent with impressive yields that typically exceed 90%: PhSiCl3 (97.5%); PhMeSiCl2 (95.5%); Ph3SiCl (97.5%); Vi3SiCl (98.7%); (EtO)3SiCl (99.7%); t-Bu3SiCl (~100%); (MeClSiO)4 (86.5%); (MeClSiO)5 (95%); (MeClSiO)7 (96.5%); Ph(OEt)2SiCl (98%); ClMe2SiOSiMe2Cl (98.6%); ClMe2SiOSiMeClOSiMe2Cl (94.6%); ClMe2Si(OSiMeCl)2OSiMe2C l (92.3%); (Me3SiO)3SiCl (97%); Me3SiOSiClPhOSiMe3 (99%); Me3SiO(SiMeClO)3SiMe3 (95.7%); ClSi(OSiMe3)2OSi(OSiMe3) 2Cl (93.6%). For monohydridosilanes, dichloromethane (CH2Cl2) was a suitable solvent in which nearly quantitative conversion was observed within several minutes following the addition of the silanes to TCCA. For certain cyclic and linear siloxanes, and especially silanes containing multiple hydrogen atoms on the same silicon for which the reaction is sluggish in CH2Cl2, tetrahydrofuran (THF) was the preferred solvent. For a sterically demanding silane that did not undergo chlorination even in THF viz., HSi(OSiMe3)2O-Si(OSiMe3)2H, 1,2-dichloroethane was the best solvent.
- Varaprath, Sudarsanan,Stutts, Debra H.
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p. 1892 - 1897
(2007/10/03)
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- Intramolecular allylation of the azo group of 2-(allylsilyl)azobenzenes and its photocontrol
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Pentacoordinate allylsilanes bearing an azobenzene moiety were synthesized and their structures were elucidated. The reaction of allyldifluorosilane (E)-7a with BF3 · OEt2 did not proceed, but (E)-7a was allowed to react with a fluoride ion to give tetrafluorosilicate 8a via intramolecular allyl-migration from the silicon atom onto the azo group. Activation of both the nucleophilic and electrophilic parts by the Si?N interaction was found to be important for promotion of the allyl-migration reaction. The azobenzene moiety of the allylsilane was reversibly isomerized by photoirradiation. The (Z)-7a formed by photoirradiation of (E)-7a is in a tetracoordinate state in contrast to the (E)-7a, and it did not react with a fluoride ion at all under the conditions where (E)-7a reacted quantitatively. The reactivity was successfully controlled without changing any conditions other than the change of the coordination number of the silicon atom induced by photoirradiation.
- Yamamura, Masaki,Kano, Naokazu,Kawashima, Takayuki
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p. 313 - 325
(2008/02/03)
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- PROCESS FOR PRODUCTION OF TRIALKOXYHALOSILANES, PROCESS FOR PRODUCTION OF ALKOXY(DIALKYLAMINO)SILANES, CATALYSTS FOR (CO)POLYMERIZATION OF ALPHA-OLEFINS, CATALYST COMPONENTS THEREFOR, AND PROCESS ES FOR POLYMERIZATION OF ALPHA-OLEFINS WITH THE CATALYSTS
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A process for the production of trialkoxyhalosilanes which comprises reacting a tetrahalosilane [37] with a tetra- alkoxysilane [38] in the presence of an alcohol whose alkoxy group is the same as those of the tetraalkoxysilane to thereby obtain a trialkoxyhalosilane [39], characterized in that the alcohol is used in an amount of 5 to 50 % by mole based on the total amount of Si of the tetrahalosilane and the tetraalkoxysilane: SiX4 [37] (wherein X is halogeno) Si(OR1)4 [38] (wherein R1 is a hydrocarbon group having 1 to 6 carbon atoms) XSi(OR1)3 [39] (wherein X and R1 are each as defined above).
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Page/Page column 16-17
(2010/11/08)
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- CATALYSTS FOR POLYMERIZATION OR COPOLYMERIZATION OF a-OLEFINS, CATALYST COMPONENTS THEREOF, AND PROCESSES FOR POLYMERIZATION OF a-OLEFINS WITH THE CATALYSTS
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The invention has an object to provide a catalyst for polymerizing or copolymerizing an α-olefin, catalyst constituent thereof, and method of polymerizing α-olefins with the catalyst, for production of α-olefin polymers or copolymers with high hydrogen response, high polymarization reaction rate, high stereoregularity and excellent melt fluidity. The invention discloses a catalyst constituent of the catalyst for polymerizing or copolymerizing an α-olefin, represented by Formula 37 or 38:Formula 37 Si(OR1)3(NR2R3) (where in Formula 37, R1 is a hydrocarbon group with 1 to 6 carbon atoms; R2 is a hydrocarbon group with 1 to 12 carbon atoms or hydrogen; and R3 is a hydrocarbon group with 1 to 12 carbon atoms)Formula 38 RNSi(OR1)3 (where in Formula 38, R1 is a hydrocarbon group with 1 to 6 carbon atoms; and RN is a cyclicl amino group).
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- Synthesis, structure, immobilization and solid-state NMR of new dppp- and tripod-type chelate linkers
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Chelating phosphines incorporating ethoxysilane functions for immobilizations have been synthesized and fully characterized. (EtO)Si(CH 2PPh2)3, (EtO)2Si(CH 2PPh2)2, and Si(CH2PPh 2)4 could be prepared in high yields from cheap starting materials. The ethoxysilanes, as well as a Pd complex thereof have been characterized by X-ray structures, and immobilized on silica. The success of the immobilization was proved by 31P solid-state NMR of the dry materials and of the suspensions. Two representative chelate metal complexes, (EtO)2Si(CH2PPh2)2PdCl2 and (EtO)Si(CH2PPh2)3W(CO)3 have been synthesized, characterized and immobilized.
- Bogza, Mona,Oeser, Thomas,Blümel, Janet
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p. 3383 - 3389
(2007/10/03)
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- Process for making haloalkylalkoxysilanes
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A haloalkylalkoxysilane is prepared by reacting an olefinic halide with an alkoxysilane in which the alkoxy group(s) contain at least two carbon atoms in the presence of a catalytically effective amount of ruthenium-containing catalyst. The process can be used to prepare, inter alia, chloropropyltriethoxysilane which is a key intermediate in the manufacture of silane coupling agents.
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- Exchange reactions in alkoxy derivatives of silicon and germanium
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Reaction SiCl4+ Ge(OR)4 → GeCl4+ Si(OR)4 was carried out for the first time. Triethoxysilane reduces tetraethoxygermane via intermediate formation of unstable GeH(OEt)3 that transforms into GeO·Et2O or Ge(OH)2.
- Chernyshev,Belyakova,Knyazev,Turkel'Taub',Ovsyankina,Ugarova,Yakovleva
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p. 650 - 652
(2007/10/03)
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- Recovery of trimethylchlorosilane from its azeotropic mixture with SiCl4
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Reaction of tetraethoxysilane with the azeotropic mixture Me3SiCl-SiCl4 in the presence of certain cyclic (tetrahydrofuran, dioxane) and acyclic (diethyl ether) ethers, ethanol, or dimethylformamide was studied with the aim of SiMe3Cl recovery.
- Voronkov,Baryshok,Kuznetsova
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p. 2091 - 2094
(2007/10/03)
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- Synthesis and reactivity of bis(triethoxysilyl)methane, tris(triethoxysilyl)methane and some derivatives
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Syntheses of new poly(trifunctional-silyl)alkanes, which are potent coupling agents of hybrid organic-inorganic materials have been thoroughly examined. Optimization of the Benkeser reaction using chloroform, trichlorosilane and tri-n-butylamine (respective ratios 1:4.5:3) afforded bis(trichlorosilyl)methane isolated as bis(triethoxysilyl)methane after ethanolysis (overall yield 60%). With nine equivalents of trichlorosilane, tris(trichlorosilyl)methane is preferentially formed, isolated as tris(triethoxysilyl)methane (30% yield). C-Substituted bis(triethoxysilyl) methanes were obtained after metallation of the α-carbon and trapping experiments with the corresponding alkyl halides. In the case of tris(triethoxysilyl)carbanion, only MeI and Br2 were able to give the anticipated products. Unexpectedly, CO2 insertion afforded the stable ketene, [(EtO)3Si]2C=C=O.
- Corriu, Robert J.P.,Granier, Michel,Lanneau, Gerard F.
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- Reaction of Tetraalkoxysilanes with Alkyl(aryl)chlorosilanes
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Alkyl(aryl)trichloro- or dialkyl(diaryl)dichlorosilanes react with tetraalkoxysilanes Si(OMe)4, Si(OEt)4, and Si(OBu)4 to give partially etherfied alkyl(aryl)chlorosilanes RSiCl2(OAlk), RSiCl(OAlk)2, and R2SiCl(OAlk).
- Chernyshev, E. A.,Komalenkova, N. G.,Tagachenkov, A. A.,Bykovchenko, V. G.
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p. 241 - 243
(2007/10/03)
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