- THERMOLYSE UND PHOTOLYSE EINIGER SILA- UND DISILACYCLOBUTANE
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The thermolysis of some 1,1-di- or 1,1,2-tri-substituted 1-silacyclobutanes leads to 1,3-disilacyclobutanes or to polymeric products.A possible intermediate silaalkene could not be stabilized, even in the presence of bulky substituents at the silicon atom.Photolysis of some di- or tri-substituted silacyclobutanes in methanol results in ring opening or in elimination of an alkene with further reaction of the intermediates with the solvent.Photolysis of the 1,1-diphenyl-2-methyl-1-silacyclobutane in cyclohexane leads to the 1,1,3,3-tetraphenyl-1,3-disilacyclobutane.The influence of the substituents at the silicon or the carbon atom on the reaction pathways is discussed.Photolysis opening and addition of methanol, whereas the 1,1,3,3-tetraphenyl-1,3-disilacyclobutane does not show any reaction.
- Jutzi, Peter,Langer, Peter
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- Catalytic Disproportionation of Formic Acid to Methanol by using Recyclable Silylformates
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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)
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- Highly Selective Hydroxylation and Alkoxylation of Silanes: One-Pot Silane Oxidation and Reduction of Aldehydes/Ketones
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An efficient chemoselective iridium-catalyzed method for the hydroxylation and alkoxylation of organosilanes to generate hydrogen gas and silanols or silyl ethers was developed. A variety of sterically hindered silanes with alkyl, aryl, and ether groups were tolerated. Furthermore, this atom-economical catalytic protocol can be used for the synthesis of silanediols and silanetriols. A one-pot silane oxidation and chemoselective reduction of aldehydes/ketones was also realized.
- Luo, Nianhua,Liao, Jianhua,Ouyang, Lu,Wen, Huiling,Zhong, Yuhong,Liu, Jitian,Tang, Weiping,Luo, Renshi
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p. 165 - 171
(2020/01/21)
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- Synthesis of phenyl-methyl dialkoxy silane method of the
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The invention relates to a method for synthesizing phenyl methyl dialkoxyl silane with high selectivity. The structural formula of phenyl methyl dialkoxyl silane is PhMeSi(OR)2, in which R is alkyl with 1-6 carbons. The method is characterized by comprising the following steps of: performing reaction with methyl trialkoxyl silane based on non-cyclic ether compounds such as ethyl ether as a reaction liquor and a bromobenzene Grignard reagent as a raw material; and then, obtaining the target compound, i.e., phenyl methyl dialkoxyl silane with high selectivity and high yield through simple filtering and fractional purification, and meanwhile, greatly inhibiting the generation of a byproduct diphenyl methyl alkoxyl silane.
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Paragraph 0048
(2017/03/14)
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- Silica-supported ultra small gold nanoparticles as nanoreactors for the etherification of silanes
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Ultra small gold nanoparticles supported by porous silica (Au-SiO2) were successfully synthesized. Due to enrichment of reactants by silica, the Au-SiO2 particles functioned as nanoreactors for catalytic etherification of silanes wit
- Wang, Cui,Lin, Xijie,Ge, Yuzhen,Shah, Zameer Hussain,Lu, Rongwen,Zhang, Shufen
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p. 102102 - 102108
(2016/11/09)
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- Gold nanoparticles-catalyzed activation of 1,2-disilanes: Hydrolysis, silyl protection of alcohols and reduction of tert-benzylic alcohols
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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
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supporting information
p. 10751 - 10753,3
(2020/09/02)
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- Meerwein's reagent mediated, significantly enhanced nucleophilic fluorination on alkoxysilanes
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We developed a new facile method to fluorosilanes from alkoxysilanes using Meerwein's reagent. Our protocol afforded fluorosilanes in excellent yields in various organic solvents including acetonitrile under mild reaction conditions at room temperature. We also proposed a reaction mechanism with the probable silyloxonium intermediates. Georg Thieme Verlag Stuttgart · New York.
- Jorapur, Yogesh R.,Shimada, Toyoshi
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supporting information; experimental part
p. 1064 - 1068
(2012/06/17)
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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
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supporting information; experimental part
p. 1633 - 1638
(2012/08/07)
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- An efficient solvent-free route to silyl esters and silyl ethers
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Dinuclear metal complexes, especially (p-cymene)ruthenium dichloride dimer {[RuCl2(p-cymene)]2}, have been found to exhibit high catalytic performance for the dehydrosilylation of various kinds of carboxylic acids and alcohols. The dehydrosilylation with [RuCl2(p-cymene)] 2 proceeded efficiently with only one equivalent of silane with respect to substrate (carboxylic acids or alcohols) under solvent-free conditions to give the corresponding silyl esters and ethers in excellent yields with a high turnover number (TON) and frequency (TOF). The 1H NMR spectrum of a toluene-d8 solution of [RuCl2(p-cymene)] 2 and a silane showed a signal assignable to the ruthenium hydride species. In contrast, no new signals were detected in the 1H NMR spectrum of a toluene-d8 solution of [RuCl2(p-cymene)] 2 and a carboxylic acid or an alcohol. There-fore, the ruthenium metal in [RuCl2(p-cymene)]2 activates a silane to afford the hydride intermediate, possibly a silylmetal hydride species. Then, the nucleophilic attack of a substrate (carboxylic acid or alcohol) to the hydride intermediate proceeds to give the corresponding silylated product. The present dehydrosilylation with an optically active silane proceeded exclusively under inversion of stereochemistry at the chiral silicon center, suggesting that the nucleophilic attack of a substrate to the hydride intermediate occurs from the backside of the ruthenium-silicon bond.
- Ojima, Yuko,Yamaguchi, Kazuya,Mizuno, Noritaka
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scheme or table
p. 1405 - 1411
(2009/12/07)
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- Organogermanium reactive intermediates. The direct detection and characterization of transient germylenes and digermenes in solution
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Diphenylgermylene (Ph2Ge) and its Ge=Ge doubly bonded dimer, tetraphenyldigermene (6a), have been characterized directly in solution for the first time by laser flash photolysis methods. The germylene is formed via (formal) cheletropic photocycloreversion of 3,4-dimethyl-1,1- diphenylgermacyclopent-3-ene (4a), which is shown to proceed in high chemical (>95%) and quantum yield (Φ = 0.62) by steady-state trapping experiments with methanol, acetic acid, isoprene, and triethylsilane. Flash photolysis of 4a in dry deoxygenated hexane at 23°C leads to the prompt formation of a transient assigned to Ph2Ge (∈max = 500 nm; ∈max = 1650 M-1 cm-1), which decays with second-order kinetics (τ ≈ 3 μs), with the concomitant growth of a second transient species that is assigned to digermene 6a (τ ≈ 40 μs; λmax = 440 nm). Analogous results are obtained from 1,1-dimesityl- and 1,1-dimethyl-3,4-dimethylgermacyclopent-3-ene (4b and 4c, respectively), which afford Mes2Ge (τ = 20 μs; λmax = 560 nm) and Me2Ge (τ ≈ 2 μs; λs; λmax = 480 nm), respectively, as well as the corresponding digermenes, tetramesityl- (6b; λmax = 410 nm) and tetramethyldigermene (6c; λmax = 370 nm). The results for the mesityl compound are compared to the analogous ones from laser flash photolysis of the known Mes2Ge/6b precursor, hexamesitylcyclotrigermane. The spectra of the three germylenes and two of the digermenes are in excellent agreement with calculated spectra, derived from time-dependent DFT calculations. Absolute rate constants for dimerization of Ph2Ge and Mes2Ge and for their reaction with n-butylamine and acetic acid in hexane at 23°C are also reported.
- Leigh, William J.,Harrington, Cameron R.,Vargas-Baca, Ignacio
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p. 16105 - 16116
(2007/10/03)
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- Steady state and time-resolved spectroscopic studies of the photochemistry of 1-arylsilacyclobutanes and the chemistry of 1-arylsilenes
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Direct photolysis of 1-phenylsilacyclobutane and 1-phenyl-, 1-(2-phenylethynyl)-, and 1-(4'-biphenylyl)-1-methylsilacyclobutane in hexane solution leads to the formation of ethylene and the corresponding 1-arylsilenes, which have been trapped by photolysis in the presence of methanol. Quantum yields for photolysis of the three methyl-substituted compounds have been determined to be 0.04, 0.26, and 0.29, respectively, using the photolysis of 1,1-diphenylsilacyclobutane (Φ(silene) = 0.21) as the actinometer. The corresponding silenes have been detected by laser flash photolysis; they have lifetimes of several microseconds, exhibit UV absorption maxima ranging from 315 to 330 nm, and react with methanol with rate constants on the order of (2-5) x 109 M-1 s-1 in hexane. Absolute rate constants for reaction of 1-phenylsilene and 1-methyl-1-phenylsilene with water, methanol, tert-butanol, and acetic acid in acetonitrile solution have been determined, and are compared to those of 1,1-diphenylsilene under the same conditions. With the phenylethynyl- and biphenyl-substituted methylsilacyclobutanes, the triplet states can also be detected by laser flash photolysis, and are shown to not be involved in silene formation on the basis of triplet sensitization and (or) quenching experiments. Fluorescence emission spectra and singlet lifetimes have been determined for the three 1-aryl-1-methylsilacyclobutanes, 1,1-diphenylsilacyclobutane, and a series of acyclic arylmethylsilane model compounds. These data, along with the reaction quantum yields, allow estimates to be made of the rate constants for the excited singlet state reaction responsible for silene formation. 1-Methyl-1-phenylsilacyclobutane undergoes reaction from its lowest excited singlet state with a rate constant 10-80 times lower than those of the other three derivatives. The results are consistent with a stepwise mechanism for silene formation, involving a 1,4-biradicaloid intermediate that partitions between product and starting material.
- Leigh,Boukherroub,Bradaric,Cserti,Schmeisser
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p. 1136 - 1147
(2007/10/03)
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- Far-UV laser flash photolysis in solution. A time-resolved spectroscopic study of the chemistry of 1,1-dimethyl-1,3-(1-sila)- butadiene
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Laser flash photolysis (193 nm) of 1,1-dimethyl-(1-sila)cyclobut-2-ene in hexane solution leads to the formation of a transient species (τ ~ 1.5 μs at 23°C) assigned to 1,1-dimethyl-1,3-(1-sila)butadiene on the basis of its UV absorption spectrum (λm
- Kerst, Corinna,Byloos, Martin,Leigh, William J.
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p. 975 - 982
(2007/10/03)
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- An Efficient Catalyst for the Conversion of Hydrosilanes to Alkoxysilanes
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The copper(I) hydride 6 is an efficient catalyst for the alcoholysis of primary and secondary silanes.The reactions proceed at room temperature within a few hours and give the alkoxysilanes in high yields.Only with bulky alcohols or silanes are longer reaction times and/or increased temperatures required.The presence of air accelarates the reactions and gives rise to higher yields of alkoxysilanes, particularly with bulky alcohols.Diols react with PhRSiH2 (R = Me, Ph) to afford 1,3-dioxo-2-silacycloalkanes and with tertiary silanes to furnish the bissilylated diols.When unsaturated alcohols (2-propen-1-ol or 2-propyn-1-ol) are employed, the double or triple bond is retained. - Keywords: Catalytic silane alcoholysis; Alkoxysilanes
- Lorenz, Catrin,Schubert, Ulrich
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p. 1267 - 1270
(2007/10/03)
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- Photochemical protodesilylation of 2-R3Si-1,3-dimethoxybenzenes. Direct observation of β-silyl-substituted cyclohexadienyl cations
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Irradiation (254 nm) of the title compounds 5 (R3Si = Me3Si, Ph2MeSi, and 4-XC6H4Me2Si with X = 4-MeO, 4-Me, H, 4-F, and 4-Cl) in 1,1,1,3,3,3-hexafluoroisopropyl alcohol (HFIP) results in q
- Lew, Calvin S. Q.,McClelland, Robert A.
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p. 11516 - 11520
(2007/10/02)
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