- A facile and efficient synthesis of organocyclosiloxanes
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A new facile preparative method for the synthesis of organocyclosiloxanes is reported. Ring closure of the dichlorosilanes with NaHCO3 and pyridine gave mixture of organocyclosiloxanes with cyclotrisiloxane as a main product.
- Zuev, Vjacheslav V.,Kalinin, Alexei V.
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- Renewable Isohexide-Based, Hydrolytically Degradable Poly(silyl ether)s with High Thermal Stability
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Several degradable poly(silyl ether)s (PSEs) have been synthesized by dehydrogenative cross-coupling between bio-based 1,4:3,6-dianhydrohexitols (isosorbide and isomannide) and commercially available hydrosilanes. An air-stable manganese salen nitrido complex [MnVN(salen-3,5-tBu2)] was employed as the catalyst. High-molecular-weight polymer was obtained from isosorbide and diphenylsilane (Mn up to 17000 g mol?1). Thermal analysis showed that these PSEs possessed high thermal stability with thermal decomposition temperatures (T?5 %) of 347–446 °C and glass transition temperatures of 42–120 °C. Structure–property analysis suggested that steric bulk and molecular weight have a significant influence to determine the thermal properties of synthesized polymers. Importantly, these polymers were degraded effectively to small molecules under acidic and basic hydrolysis conditions.
- Vijjamarri, Srikanth,Hull, Marianne,Kolodka, Edward,Du, Guodong
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- Novel palladium-catalyzed atom-efficient cross-coupling reaction by means of hexaarylcyclotrisiloxane
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Hexaarylcyclotrisiloxane, which is one of the most stable derivatives of diarylsilanediol, was found to undergo palladium-catalyzed cross-coupling reaction with aryl halides in good yields. The reaction is performed in an aqueous medium taking potassium hydroxide as an activator. Both of the two aryl groups attached to each silicon atom could be utilized. Some base-sensitive functionality such as acetyl and nitro groups survived the reaction. Georg Thieme Verlag Stuttgart.
- Endo, Mayuko,Sakurai, Tomoyuki,Ojima, Satoshi,Katayama, Takako,Unno, Masafumi,Matsumoto, Hideyuki,Kowase, Susumu,Sano, Hiroshi,Kosugi, Masanori,Fugami, Keigo
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p. 749 - 752
(2008/01/08)
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- Supramolecular aggregates of silanols and solid-state synthesis of siloxanes
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Cocrystallization of all-cis-tetraisopropylcyclotetrasiloxanetetraol and diisopropylsilanediol gave single crystals, which were proved to have a nano-size tube-like aggregate structure. Six molecules of the cyclic tetraol and four molecules of the dial form an asymmetric unit by means of hydrogen bonding. The structure and properties of the aggregates are discussed in detail, and also the possibility of solid-state synthesis of siloxanes is described.
- Unno, Masafumi,Takada, Keisuke,Kawaguchi, Yasuaki,Matsumoto, Hideyuki
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p. 259 - 264
(2007/10/03)
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- Electrochemical activation of diorganyl dialkoxysilanes for siloxane backbone extension
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The reaction of diorganyl dialkoxysilanes PhRSi(OAlk)2 (R = Ph, vinyl, OMe; Alk = Me, Et) with electrochemically reduced forms of oxygen provides reactive intermediates that insert into hexamethyldisiloxane or permethyl cyclosiloxanes, D3
- Keyrouz, Robert,Jouikov, Viatcheslav
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p. 902 - 904
(2007/10/03)
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- Matrix isolation infrared and density functional theoretical studies of organic silanones, (CH3O)2Si=O and (C6H5)2Si=O
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Transient organic silanones (CH3O)2Si=O (3) and (C6H5)2Si=O (4) were generated by vacuum pyrolysis from 3,3-dimethoxy-6-oxa-3-silabicyclo[3.1.0]hexane (6) and its 3,3-diphenyl derivative (7), respectively, and after being trapped in argon cryogenic matrices at 12 K directly studied by IR spectroscopy. Vibrational assignments in the observed IR spectra of 3 and 4 have been made by comparison with the density functional theory B3LYP/6-311G(d, p) calculated harmonic frequencies and infrared intensities for these molecules and for the other silanones, H2Si=O (1), (CH3)2Si=O (2), and CH3(CH3O)Si=O (5), studied earlier by matrix isolation techniques. The observed bands at 1247 cm-1 in 3 and at 1205 cm-1 in 4 were assigned to the Si=O stretching modes, which under the influence of the same substituents show the similar frequency shifts as ν (M=O) in ketones, phosphinoxides, and sulfoxides. Under the conditions of vacuum pyrolysis studied the diphenylsilanone 4 was found to be more thermodynamically stable than the dimethoxy derivative 3, while the latter indicated a higher kinetic stability towards cyclooligomerization than the silanones 2 and 4.
- Khabashesku, Valery N.,Kerzina, Zoya A.,Kudin, Konstantin N.,Nefedov, Oleg M.
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- Product-Specific Methods of Syntheses of Hexaphenylcyclotrisiloxane and Octaphenylcyclotetrasiloxane - Monomers of Phenylsilicones
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Pure hexaphenylcyclotrisiloxane (P3) and octaphenylcyclotetrasiloxane (P4) were synthesized with high yields via proper choice of preparation conditions, such as catalysts, solvents and reaction temperatures, from diphenylsilanediol.Up to 98percent yield of this pure starting material can be obtained from diphenyldichlorosilane through modifying a known procedure on carefully adjusting the temperature of hydrolysis and washing procedure.This method produced pure P3 exclusively with high yield (approximately 90percent) in ethanol in the presence of concentrated sulfuric acid as the catalyst at various reaction temperatures.P4 was produced exclusively in high yield (approximately 90percent) in alcohols in the presence of sodium hydroxide.A method applying HPLC was used to analyze the reaction products quantitatively. - Key words: Hexaphenylcyclotrisiloxane; Octaphenylcyclotetrasiloxane; Diphenylsilanediol.
- Yang, Mei-Hui,Chou, Chyuan,Lin, Chih-Hwa
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p. 923 - 928
(2007/10/03)
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- THE SILICON-OXYGEN DOUBLE-BONDED INTERMEDIATES. A NEW METHOD FOR THE FORMATION OF ORGANOSILANONES
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The kinetics and mechanism of thermal decomposition of R1R2(H)SiOOR3 silylperoxides have been studied.It has been shown that peroxides generated diorganosilanones, R1R2Si=O, with a high yield in the temperature range 130-180 deg C.A mechanism is suggested for the silanone formation.The interaction of silanones with cyclosiloxanes, triethylsilane, α-methylstyrene has been investigated as well as the cyclisation of silanones.
- Tomadze, A. V.,Yablokova, N. V.,Yablokov, V. A.,Razuvaev, G. A.
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