- The cyclopropylmethylsilane terminated prins reaction: Stereoelectronic controlled formation of (E)-skipped dienes
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The reaction of 1-phenyldimethylsilylmethyl-2-vinyl cyclopropane with acetals under the influence of TMSOTf proceeds smoothly to provide skipped dienes with exclusive E-olefin geometry regardless of the initial cis/trans configuration of the starting cyclopropane. The reaction is under stereoelectronic control where the intermediate Prins cation formed is stabilised by the adjacent cyclopropane grouping in a bisected conformation before undergoing silyl-directed collapse.
- Braddock,Badine,Gottschalk
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Read Online
- Experimental and theoretical investigations on the catalytic hydrosilylation of carbon dioxide with ruthenium nitrile complexes
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Ruthenium complexes, mer-[RuX3(MeCN)3] and cis/trans-[RuX2-(MeCN)4] with X = Br, Cl, were investigated as precatalysts in homogeneously catalyzed hydrosilylation of CO2, The oxidation state of ruthenium and nature of the halide in the precatalysts were found to influence the catalytic activity in the conversion of Me2PhSiH to the formoxysilane Me2PhSiOCHO, with Ru III having chloride ligands being most active. Monitoring the reactions by in-situ IR spectroscopy in MeCN as the solvent indicates an interaction of the precatalyst with the silane prior to activation of CO 2. In the absence of CO2, hydrosilylation of the MeCN solvent occurs. Catalytic activity in CO2 hydrosilylation is enhanced by Me2PhSiCl, generated during reduction of RuIII in mer-[RuX3(MeCN)3] to RuII or, when added as promoter to RuII precatalysts. The reaction mechanism for the catalytic cycle has been calculated by DFT methods for the reaction of Me 3SiH. The key steps are: Transfer of the Me3Si moiety to a coordinated halide ligand, resulting in an LnRuH-(XSiMe3) intermediate → CO2 coordination → Me3Si transfer to CO2 → reductive elimination of formoxysilane product. This reaction sequence is more favorable energetically for chloride complexes than for the analogous bromide complexes, which accounts for their differences in catalytic activity. Calculations also explain the rate increase observed experimentally in the presence of Me2PhSiCl. A parallel reaction pathway leads to (Me3Si)2O as a minor byproduct which arises from the condensation of two initially formed Me3SiOH molecules.
- Deglmann, Peter,Ember, Erika,Hofmann, Peter,Pitter, Stephan,Walter, Olaf
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- Volumetric and Refractive Properties of the Mixtures of 1,1,3,3-Tetramethyl-1,3-diphenyldisiloxane with Various Organosilicon Compounds at T = (308.15 to 328.15) K
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The density and refractive index were determined for four binary mixtures of 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane with 2,4,6,8-tetramethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, and 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane at different temperatures (T = 308.15, 313.15, 318.15 323.15 and 328.15 K) and atmospheric pressure using a DMA4500/RXA170 combined system. The excess molar volume, partial excess volume at infinite dilution, isobaric coefficient of thermal expansion, excess refraction indices, Lorentz-Lorenz molar refraction, and the deviation in molar refraction have been calculated using these data. The results have been incorporated into the Redlich-Kister equation and used to estimate the binary interaction parameters and standard deviation. The values of partial excess volume at infinite dilution and excess refraction indices for the four binary systems at different temperatures were calculated using the adjustable parameters of the Redlich-Kister smoothing equation. The factors that affect these excess quantities have been discussed.
- Dong, Hong,Yu, Lijiao,Hu, Yuqian,Wu, Chuan
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Read Online
- Silylating Disulfides and Thiols with Hydrosilicones Catalyzed by B(C6F5)3
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Hydrosilanes and silicones, catalyzed with B(C6F5)3, may be used to silylate thiols or cleave disulfides giving silyl thio ethers. Alcohols were found to react faster than thiols or disulfides, while alkoxysilanes (the Piers-Rubinsztajn reaction) were slower such that the overall order of reactivity was found to be HO>HS>SS>SiOEt. The resulting silane and silicone-protected thio ethers produced from the sulfur-based functional groups could be cleaved to thiols using alcohols or mild acid with rates that depend on the steric bulk of the siloxane.
- Brook, Michael A.,Liao, Mengchen,Zheng, Sijia
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supporting information
p. 2694 - 2700
(2021/06/25)
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- Metal-free hydrogen evolution cross-coupling enabled by synergistic photoredox and polarity reversal catalysis
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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
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supporting information
p. 8988 - 8994
(2021/11/23)
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- Charge Modified Porous Organic Polymer Stabilized Ultrasmall Platinum Nanoparticles for the Catalytic Dehydrogenative Coupling of Silanes with Alcohols
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Developing an ideal stabilizer to prevent the aggregation of nanoparticles is still a big challenge for the practical application of noble metal nanocatalysts. Herein, we develop a charge (NTf2?) modified porous organic polymer (POP-NTf2) to stabilize ultrasmall platinum nanoparticles. The catalyst is characterized and applied in the catalytic dehydrogenative coupling of silanes with alcohols. The catalyst exhibits excellent catalytic performance with highly dispersed ultrasmall platinum nanoparticles (ca. 2.22?nm). Moreover, the catalyst can be reused at least five times without any performance significant loss and Pt NPs aggregation. Graphic Abstract: [Figure not available: see fulltext.]
- Chen, Chao,Cheng, Dan,Ding, Shunmin,Liang, Sanqi,Liu, Senqun,Ma, Xiaohua,Su, Tongtong,Wu, Shaohua,Zeng, Rong
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- Hydrosilylative reduction of carbon dioxide by a homoleptic lanthanum aryloxide catalyst with high activity and selectivity
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An efficient tandem hydrosilylation of CO2, which uses a combination of a simple, homoleptic lanthanum aryloxide and B(C6F5)3, was performed. Use of a less sterically hindered silane led to an exclusive reduction of CO2to CH4, with a turnover frequency of up to 6000 h?1at room temperature. The catalytic system is robust, and 19?400 turnovers could be achieved with 0.005 mol% loading of lanthanum. The reaction outcome depended highly on the nature of the silane reductant used. Selective production of the formaldehyde equivalent,i.e., bis(silyl)acetal, without over-reduction, was observed when a sterically bulky silane was used. The reaction mechanism was elucidated by stoichiometric reactions and DFT calculations.
- Chang, Kejian,Maron, Laurent,Xu, Xin,Zheng, Xizhou,del Rosal, Iker
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supporting information
p. 7804 - 7809
(2021/06/16)
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- Novel Si(II)+and Ge(II)+Compounds as Efficient Catalysts in Organosilicon Chemistry: Siloxane Coupling Reaction ?
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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
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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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- Cobalt-Catalyzed Selective Synthesis of Disiloxanes and Hydrodisiloxanes
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Selective syntheses of symmetrical siloxanes and cyclotetrasiloxanes are attained from reactions of silanes and dihydrosilanes, respectively, with water, and the reactions are catalyzed by a NNNHtBu cobalt(II) pincer complex. Interestingly, when phenylsilane was subjected to catalysis with water, a siloxane cage consisting 12 silicon and 18 oxygen centers was obtained and remarkably the reaction proceeded with liberation of 3 equiv of molecular hydrogen (36 H2) under mild experimental conditions. Upon reaction of silane with different silanols, highly selective and controlled syntheses of higher order monohydrosiloxanes and disiloxymonohydrosilanes were achieved by cobalt catalysis. The liberated molecular hydrogen is the only byproduct observed in all of these transformations. Mechanistic studies indicated that the reactions occur via a homogeneous pathway. Kinetic and independent experiments confirmed the catalytic oxidation of silane to silanol, and further dehydrocoupling processes are involved in syntheses of symmetrical siloxanes, cyclotetrasiloxanes, and siloxane cage compounds, whereas the unsymmetrical monohydrosiloxane syntheses from silanes and silanols proceeded via dehydrogenative coupling reactions. Overall these cobalt-catalyzed oxidative coupling reactions are based on the Si-H, Si-OH, and O-H bond activation of silane, silanol, and water, respectively. Catalytic cycles consisting of Co(II) intermediates are suggested to be operative.
- Pattanaik, Sandip,Gunanathan, Chidambaram
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p. 5552 - 5561
(2019/06/05)
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- Nickel(0) catalyzed oxidation of organosilanes to disiloxanes by air as an oxidant
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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)
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- Catalytic Metal-Free Deoxygenation of Nitrous Oxide with Disilanes
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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)
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- Breaking C-O Bonds with Uranium: Uranyl Complexes as Selective Catalysts in the Hydrosilylation of Aldehydes
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We report herein the possibility to perform the hydrosilylation of carbonyls using actinide complexes as catalysts. While complexes of the uranyl ion [UO2]2+ have been poorly considered in catalysis, we show the potentialities of the Lewis acid [UO2(OTf)2] (1) in the catalytic hydrosilylation of a series of aldehydes. [UO2(OTf)2] proved to be a very active catalyst affording distinct reduction products depending on the nature of the reductant. With Et3SiH, a number of aliphatic and aromatic aldehydes are reduced into symmetric ethers, while iPr3SiH yielded silylated alcohols. Studies of the reaction mechanism led to the isolation of aldehyde/uranyl complexes, [UO2(OTf)2(4-Me2N-PhCHO)3], [UO2(μ-κ2-OTf)2(PhCHO)]n, and [UO2(μ-κ2-OTf)(κ1-OTf)(PhCHO)2]2, which have been fully characterized by NMR, IR, and single-crystal X-ray diffraction.
- Monsigny, Louis,Thuéry, Pierre,Berthet, Jean-Claude,Cantat, Thibault
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p. 9025 - 9033
(2019/10/02)
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- METHOD FOR PRODUCING HALOSILANE
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PROBLEM TO BE SOLVED: To provide a method for producing halosilane that can efficiently produce halosilane. SOLUTION: Alkoxy halomethane is used as a halogenating agent and reacted with oxysilane having a structure represented by formula (a), to efficiently produce halosilane having a structure represented by formula (b) (In the formula (b), X is a chlorine atom, a bromine atom, or an iodine atom). SELECTED DRAWING: None COPYRIGHT: (C)2019,JPOandINPIT
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Paragraph 0028; 0031; 0032
(2019/07/31)
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- Selective reduction of formamides to O-silylated hemiaminals or methylamines with HSiMe2Ph catalyzed by iridium complexes
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The reaction of (4-methyl-pyridin-2-iloxy)ditertbutylsilane (NSitBu-H, 1) with [IrCl(coe)2]2 affords the iridium(iii) complex [Ir(H)(Cl)(κ2-NSitBu)(coe)] (2), which has been fully characterized including X-ray diffraction studies. The reaction of 2 with AgCF3SO3 leads to the formation of species [Ir(H)(CF3SO3)(κ2-NSitBu)(coe)] (3). The iridium complexes 2 and 3 are effective catalysts for the reduction of formamides with HSiMe2Ph. The selectivity of the reduction process depends on the catalyst. Thus, by using complex 2, with a chloride ancillary ligand, it has been possible to selectively obtain the corresponding O-silylated hemiaminal by reaction of formamides with one equivalent of HSiMe2Ph, while complex 3, with a triflate ligand instead of chloride, catalyzed the selective reduction of formamides to the corresponding methylamine.
- Guzmán, Jefferson,Bernal, Ana M.,García-Ordu?a, Pilar,Lahoz, Fernando J.,Oro, Luis A.,Fernández-Alvarez, Francisco J.
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p. 4255 - 4262
(2019/04/01)
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- Benzoimidazole-Pyridylamido Zirconium and Hafnium Alkyl Complexes as Homogeneous Catalysts for Tandem Carbon Dioxide Hydrosilylation to Methane
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Neutral ZrIV and HfIV alkyl/amido complexes stabilized by a tridentate N ligand that contains a “rolling” heterodentate benzoimidazole fragment have been prepared and characterized. The ultimate nature of the ligand denticity, the electronic properties of the ligand binding pocket and the metal coordination environment are controlled by the protection/deprotection of the benzoimidazole NH group. The metal precursor used [MIV(Bn)4 or MIV(NMe2)4] also has an influence on the final coordination sphere of the complex; indeed, a permanent central pyridine dearomatization occurs in the presence of dimethylamido ancillary groups. DFT calculations on the real system have been used to elucidate the mechanism. Selected alkyl species from this series have been scrutinized for the tandem hydrosilylation of CO2 to CH4 in combination with the strong Lewis acid B(C6F5)3 using a variety of hydrosilanes. A positive effect of the hardness modification of the ligand donor atom set is observed in the catalytic outcomes. Indeed, κ3{N?,N,N?}ZrIV(Bn)2 catalyzes the process to methane selectively with a turnover frequency as high as 272 h?1 (at 96 % substrate conversion) almost twice as much as that claimed for the benchmark κ3{O?,O,O?}ZrIV(Bn)2 complex under similar experimental conditions.
- Luconi, Lapo,Rossin, Andrea,Tuci, Giulia,Gafurov, Zufar,Lyubov, Dmitrii M.,Trifonov, Alexander A.,Cicchi, Stefano,Ba, Housseinou,Pham-Huu, Cuong,Yakhvarov, Dmitry,Giambastiani, Giuliano
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p. 495 - 510
(2019/01/14)
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- Site-selective C-H bond carbonylation with CO2 and cobalt-catalysis
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Utilization of anthropogenic greenhouse gas CO2 for catalytic C-C bond formation via conversion to essentially valuable C1 synthons like CO is very challenging. The requirement of an efficient catalyst that has the ability to convert CO2 into CO and activate inert C-H bonds is the bottleneck. We herein demonstrate a tandem approach accomplished in a two-chamber system for efficient fluoride-mediated generation of CO from CO2 using disilane as a deoxygenating reagent and utilization of the in situ-produced CO gas for C-H bond carbonylation using earth-abundant cobalt catalysts. The ease of handling CO2 gas at atmospheric pressure allows us to prepare 13C labelled compounds which are otherwise difficult to achieve. The procedure developed makes it possible to utilize CO2 as a CO source, which can be widely applied as a C1 synthon that can be incorporated between C-H and N-H bonds of aromatic, hetero-aromatic and aliphatic carboxamides for the synthesis of various cyclic imides including spirocycles in a site-selective fashion. The late-stage derivatization of a well-known angiotensin receptor blocker (ARB), Telmisartan, and a well-known drug for very low-density lipoproteins (VLDLs), Gemfibrozil, is demonstrated. Further, to showcase the generality of the reaction, various pharmacologically important and privileged scaffolds like xanthone, coumarin and isatin have been synthesized with CO2 under atmospheric pressure.
- Barsu, Nagaraju,Kalsi, Deepti,Sundararaju, Basker
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p. 5963 - 5969
(2018/11/24)
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- Cesium Carbonate-Catalyzed Oxidation of Substituted Phenylsilanes for the Efficient Synthesis of Polyhedral Oligomeric Silsesquioxanes
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Cesium carbonate-catalyzed oxidation of substituted phenylsilanes (ArSiH3) in N,N-dimethylformamide (DMF) at room temperature for the efficient synthesis of polyhedral oligomeric silsesquioxanes (POSS) was described. This protocol allowed the rapid and selective access to several types of new POSS cages in modest to good yields under nonaqueous conditions. Depending on the bulkiness of the substituents on the phenyl rings, hexa- (T6), octa- (T8), and dodecaphenylsilsesquioxanes (T12) can be selectively obtained. With the more bulky 2-(2′,4′,6′-trimethylphenyl)phenyl group, the cyclic tetrasiloxane (D4) bearing four hydroxyl groups was isolated. Mechanism studies disclosed that the initial step involved the Cs2CO3-catalyzed hydrosilylation of DMF with a hydrosilane to generate a siloxymethylamine intermediate followed by the dehydrocarbonative cross-coupling of the hydrosilane with the siloxymethylamine.
- Li, Yuefeng,Cui, Chunming
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supporting information
p. 13477 - 13485
(2018/10/24)
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- meso-tetraaryl(porphyrinato)cobalt(III)-catalyzed oxygenation of disilanes under aerobic conditions
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Cobalt(III) porphyrin-catalyzed oxygenation of disilanes is investigated. Five- and six-membered cyclic disilanes are readily oxygenated, providing the corresponding cyclic disiloxanes in 75%-quant yield. We propose a reaction mechanism involving intermediates with a Co(III)Si bond based on spectroscopic analysis of the reaction mixtures.
- Ohshita, Joji,Matsumura, Yohei,Nakayama, Takahiro,Yoshida, Hiroto,Kunai, Atsutaka,Hisaeda, Yoshio,Hayashi, Takashi
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supporting information
p. 1807 - 1809
(2017/11/23)
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- Controlled synthesis of cyclosiloxanes by NHC-catalyzed hydrolytic oxidation of dihydrosilanes
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Hydrolytic oxidation of various hydrosilanes in acetonitrile and in the absence of organic solvents catalyzed by an N-heterocyclic carbene organocatalysis is described. The NHC organocatalyst exhibited a very high activity with only 0.1 mol% loading of the catalyst in acetonitrile for aryl-substituted dihydrosilanes to produce hydrogen gas and cyclosiloxanes almost quantitatively in several minutes. The calculated TOF (15 000 h-1) of this organocatalyst is comparable to those of precious metal-based heterogeneous catalysts and much superior to those of the existing homogeneous metal catalysts. The catalytic reaction selectively yielded cyclosiloxanes in high yield without the contamination of silanols. Furthermore, the catalytic reaction can also be furnished under solvent-free conditions at elevated temperatures with 2.5 mol% loading of the NHC in 5-12 hours.
- Qing, Guoping,Cui, Chunming
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supporting information
p. 8746 - 8750
(2017/07/22)
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- SILOXANE COMPOUND PRODUCTION METHOD AND GOLD CATALYST USED THEREIN
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PROBLEM TO BE SOLVED: To provide a technique for synthesizing a siloxane compound from a silane compound with high efficiency using a catalytic reaction under a safe and low environmental load condition. SOLUTION: In a siloxane compound production method, a silane compound is brought into contact with a gold catalyst carrying nano-sized gold particles on a carbon carrier, using water as a solvent in an inert gas atmosphere. A gold catalyst carrying nano-sized gold particles on a carbon carrier can be used in the method, and the gold particles have a crystallite size of 10-100 nm. SELECTED DRAWING: None COPYRIGHT: (C)2017,JPOandINPIT
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Paragraph 0054-0060
(2017/06/19)
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- DMF-activated chlorosilane chemistry: Molybdenum-catalyzed reactions of R3SiH, DMF and R′3SiCl to initially form R′3SiOSiR′3 and R3SiCl
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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)
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- Visible Light Photocatalysis Using a Commercially Available Iron Compound
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[CpFe(CO)2]2 (1) (Cp = η5-C5H5) is an effective precatalyst for the hydrophosphination of alkenes with Ph2PH under visible light irradiation, which appears to be a unique way to promote metal-catalyzed hydrophosphination. Additionally, 1 is a photocatalyst for the dehydrogenation of amine boranes and formation of siloxanes from tertiary silanes. These reactions have similar, if not improved, reactivity over the same transformations using 1 or related CpFeMe(CO)2 under UV irradiation, consistent with the notion that hydrophosphination with 1 proceeds via formation of CpFe(CO)2?. These results demonstrate that catalyst selection can avail the use of commercially available LED bulbs as photon sources, potentially replacing mercury arc lamps or other energy intensive processes in known or new catalytic reactions.
- Pagano, Justin K.,Bange, Christine A.,Farmiloe, Sarah E.,Waterman, Rory
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p. 3891 - 3895
(2017/10/30)
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- Hydrogenation and Hydrosilylation of Nitrous Oxide Homogeneously Catalyzed by a Metal Complex
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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
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supporting information
p. 5720 - 5723
(2017/05/04)
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- Cu3(BTC)2 catalyzed oxidation of silane to silanol using TBHP or water as oxidants
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In the present work, a series of metal organic frameworks are examined for the conversion of Si-H to Si-OH using either t-butylhydroperoxide (TBHP) or water as oxidants. The reaction is optimized using dimethylphenylsilane (1) as a model substrate. It is observed that Cu3(BTC)2 (BTC: 1,3,5-benzenetricarboxylate) exhibits a comparable activity with Zr(BDC) (BDC: 1,4-benzenedicarboxylate) while the activity of Fe(BTC) is lower than Cu3(BTC)2 using TBHP as oxidant. On the other hand, the reaction of 1 with water in the presence of Cu3(BTC)2 as a catalyst showed complete conversion of 1 with 99% selectivity to the corresponding silanol, but other MOFs like Fe(BTC) and Zr(BDC) are inactive under identical reaction conditions. A series of control experiments indicate that Cu2+ is essential to convert 1 to 2 under the present experimental conditions. Further, Cu2+ in Cu3(BTC)2 acts as redox centre with TBHP whereas it behaves as a Lewis acid using water as oxidant. High conversion and selectivity is observed for all the silanes studied under the present experimental conditions. The catalyst stability is assessed by powder XRD, FT-IR and SEM images and observing no structural deterioration of Cu3(BTC)2 either in TBHP or water as oxidants. Furthermore, hot filtration test indicated the absence of copper under the present reaction conditions, thus confirming the stability of Cu3(BTC)2.
- Anbu, Nagaraj,Dhakshinamoorthy, Amarajothi
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p. 145 - 153
(2017/07/26)
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- Synthesis of borasiloxanes by oxidative hydrolysis of silanes and pinacolborane using Cu3(BTC)2 as a solid catalyst
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A convenient method for the synthesis of borasiloxanes from silanes and pinacolboranes using Cu3(BTC)2 as a heterogeneous catalyst in acetonitrile at 70 °C is reported. This procedure is more convenient than Ru and Pd based homogeneous catalysts because it avoids the use of noble metals, easy handling of starting materials and the catalyst can be reused.
- Dhakshinamoorthy, Amarajothi,Asiri, Abdullah M.,Concepcion, Patricia,Garcia, Hermenegildo
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supporting information
p. 9998 - 10001
(2017/09/12)
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- Silanol Compound, Composition, and Method for Producing Silanol Compound
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The purpose of the present invention is to provide silanol compounds that can be used as raw materials of siloxane compounds and the like, and a composition of the silanol compounds, as well as to provide a production method that makes it possible to produce silanol compounds at excellent yield. A composition comprising 5 mass % to 100 mass % of a silanol compound represented by Formulas (A) to (C) can be prepared by devising to produce silanol compounds under water-free conditions, to produce silanol compounds in a solvent having the effect of suppressing the condensation of silanol compounds, and to perform other such processes, the composition being able to be used as a raw material or the like of siloxane compounds because the silanol compounds can be stably present in the resulting composition.
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Paragraph 0171; 0172; 0173; 0174
(2017/07/14)
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- Preparation method of 1,3-diphenyl-1,1,3,3-tetramethyl disiloxane
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The invention discloses a preparation method of 1,3-diphenyl-1,1,3,3-tetramethyl disiloxane. The preparation method is characterized in that the Wurtz method or Grignard method is adopted, and 1,3-diphenyl-1,1,3,3-tetramethyl disiloxane is synthesized through disiloxane rectified from an organosilicon high-boiling component and a halogenated compound. According to the preparation method, market application and high-value utilization of the organosilicon high-boiling component are expanded, and a raw material basis can be further provided for preparation of organosilicon materials with special functions.
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Paragraph 0015; 0019
(2017/05/25)
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- Synthesis of nitrogen and sulfur co-doped hierarchical porous carbons and metal-free oxidative coupling of silanes with alcohols
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Hierarchically porous N and S co-doped carbon was prepared by using 2,5-dihydroxy-1,4-benzoquinone as the carbon source, thiourea as the N and S source, and SiO2 particles as the template. Using the material as the catalyst, oxidative coupling of silanes with alcohols was conducted for the first time under metal-free conditions.
- Chen, Bingfeng,Li, Fengbo,Mei, Qingqing,Yang, Youdi,Liu, Huizhen,Yuan, Guoqing,Han, Buxing
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supporting information
p. 13019 - 13022
(2017/12/15)
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- Disiloxane Synthesis Based on Silicon-Hydrogen Bond Activation using Gold and Platinum on Carbon in Water or Heavy Water
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Disiloxanes possessing a silicon-oxygen linkage are important as frameworks for functional materials and coupling partners for Hiyama-type cross coupling. We found that disiloxanes were effectively constructed of hydrosilanes catalyzed by gold on carbon in water as the solvent and oxidant in association with the emission of hydrogen gas at room temperature. The present oxidation could proceed via various reaction pathways, such as the hydration of hydrosilane into silanol, dehydrogenative coupling of hydrosilane into disilane, and the subsequent corresponding reactions to disiloxane. Additionally, the platinum on carbon catalyzed hydrogen-deuterium exchange reaction of arylhydrosilanes as substrates in heavy water proceeded on the aromatic nuclei at 80 °C with high deuterium efficiency and high regioselectivity at the only meta and para positions of the aromatic-silicon bond to give the deuterium-labeled disiloxanes.
- Sawama, Yoshinari,Masuda, Masahiro,Yasukawa, Naoki,Nakatani, Ryosuke,Nishimura, Shumma,Shibata, Kyoshiro,Yamada, Tsuyoshi,Monguchi, Yasunari,Suzuka, Hiroyasu,Takagi, Yukio,Sajiki, Hironao
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p. 4190 - 4195
(2016/06/09)
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- Dehydrogenative coupling of silanes with alcohols catalyzed by Cu3(BTC)2
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Cu3(BTC)2 is an efficient and reusable heterogeneous catalyst for the dehydrogenative coupling of silanes with alcohols. Activity data and CO adsorption suggest that Cu(ii) and in situ generated Cu(i) are the active species. Other MOFs such as Fe(BTC), MIL-101(Cr) and UiO-66(Zr) are unable to promote this cross-coupling.
- Dhakshinamoorthy, Amarajothi,Concepcion, Patricia,Garcia, Hermenegildo
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p. 2725 - 2728
(2016/02/19)
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- Silicone wastes as reducing agents for carbon dioxide transformation: Fluoride-catalyzed formic acid synthesis from CO2, H2O, and disilanes
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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
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supporting information
p. 1464 - 1466
(2015/11/24)
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- Synthesis and reactions of donor cyclopropanes: efficient routes to cis- and trans-tetrahydrofurans
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Abstract A detailed study on the synthesis and reactions of silylmethylcyclopropanes is reported. In their simplest form, these donor-only cyclopropanes undergo Lewis acid promoted reaction to give either cis- or trans-tetrahydrofurans, with the selectivity being reaction condition-dependant. The adducts themselves are demonstrated to be an important scaffold for structural diversification. The combination of a silyl-donor group in a donor-acceptor cyclopropane with novel acceptor groups is also discussed.
- Dunn, Jonathan,Dobbs, Adrian P.
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supporting information
p. 7386 - 7414
(2015/08/24)
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- Copper-catalyzed α-selective hydrostannylation of alkynes for the synthesis of branched alkenylstannanes
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A variety of branched alkenylstannanes can directly be synthesized with excellent α-selectivity by the copper-catalyzed hydrostannylation using a distannane or a silylstannane, irrespective of the electronic and steric characteristics of terminal alkynes employed. Synthetic utility of the resulting branched alkenylstannane has been demonstrated by the total synthesis of bexarotene.
- Yoshida,Shinke,Kawano,Takaki
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supporting information
p. 10616 - 10619
(2015/06/30)
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- Palladium nanoparticles supported on graphene as catalysts for the dehydrogenative coupling of hydrosilanes and amines
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Palladium nanoparticles (Pd NPs) were supported on undoped and N- or B-doped graphenes (Gs) and these materials have been used as catalysts for the dehydrogenative coupling of hydrosilanes and amines to form silazanes. Working under optimal conditions, a conversion over 99% and a selectivity of 84% were achieved for the reaction of dimethylphenylsilane with morpholine. In contrast, copper (Cu NPs) or nickel nanoparticles (Ni NPs) supported on G did not promote the formation of the corresponding Si-N coupling product. It was found that Pd/G performed better for this coupling than analogous catalysts, in which Pd NPs were supported on active carbon, multiwall carbon nanotubes or diamond NPs. Pd/G as a catalyst has a wide substrate scope, including aliphatic and aromatic amines and mono or dihydrosilanes. Pd/G undergoes a gradual deactivation due to the growth and partial agglomeration of Pd NPs and the aggregation of G sheets, as observed by TEM. This journal is
- Blandez, Juan F.,Esteve-Adell, Iván,Alvaro, Mercedes,García, Hermenegildo
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p. 2167 - 2173
(2015/04/14)
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- An efficient catalytic approach for the synthesis of unsymmetrical siloxanes
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The potential for expanding the variety of catalytic methods for siloxane bond formation is explored. Alkoxysilanes react with methylallylsilanes in the presence of scandium(III) trifluoromethanesulfonate to yield disiloxanes and isobutene. The reaction p
- Hreczycho, Grzegorz
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- Plasma synthesis of carbon nanotube-gold nanohybrids: Efficient catalysts for green oxidation of silanes in water
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We report the green synthesis of silanols from hydrosilanes in high yields by using oleylamine (OA) stabilized gold nanoparticles (AuNPs) supported on oxidized multi-walled carbon nanotubes (o-CNTs) as catalysts in H2O. The Au catalyst can be easily synthesized by a one-pot gas-liquid interfacial plasma method, and the catalyst exhibited much more remarkable catalytic activity in the oxidation of various organosilanes by using water as the solvent compared with other organic solvents (for example THF, ethyl acetate, and acetone), which is very important for organic synthesis from both the standpoint of practical reasons and an economic perspective. The Au catalyst can be readily recovered and reused without any loss of catalytic activity. In addition, our findings indicate that o-CNTs and OA are the key components of the catalyst in which the o-CNT support makes the hybrid materials hydrophilic, and the OA stabilizer makes the hybrid materials lipophilic, resulting in the high activity of the catalyst in H2O. The Royal Society of Chemistry.
- Liu, Ting,Yang, Fan,Li, Yongfeng,Ren, Liang,Zhang, Liqiang,Xu, Kai,Wang, Xian,Xu, Chunming,Gao, Jinsen
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p. 245 - 250
(2014/01/06)
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- N-Methylacridinium Salts: Carbon Lewis Acids in Frustrated Lewis Pairs for σ-Bond Activation and Catalytic Reductions
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N-methylacridinium salts are Lewis acids with high hydride ion affinity but low oxophilicity. The cation forms a Lewis adduct with 4-(N,N-dimethylamino)pyridine but a frustrated Lewis pair (FLP) with the weaker base 2,6-lutidine which activates H2, even in the presence of H2O. Anion effects dominate reactivity, with both solubility and rate of H2 cleavage showing marked anion dependency. With the optimal anion, a N-methylacridinium salt catalyzes the reductive transfer hydrogenation and hydrosilylation of aldimines through amine-boranes and silanes, respectively. Furthermore, the same salt is active for the catalytic dehydrosilylation of alcohols (primary, secondary, tertiary, and ArOH) by silanes with no observable over-reduction to the alkanes.
- Clark, Ewan R.,Ingleson, Michael J.
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supporting information
p. 11306 - 11309
(2016/02/19)
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- Nonhydrolytic synthesis of silanols by the hydrogenolysis of benzyloxysilanes
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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
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p. 429 - 431
(2014/04/17)
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- METHOD FOR THE CATALYTIC REDUCTION OF ACID CHLORIDES AND IMIDOYL CHLORIDES
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The present application relates to methods for the catalytic reduction of acid chlorides and/or imidoyl chlorides. The methods comprise reacting the acid chloride or imidoyl chloride with a silane reducing agent in the presence of a catalyst such as [Cp(Pri3P)Ru(NCMe)2]+[PF6]?.
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-
Paragraph 0176; 0196; 0197
(2014/08/19)
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- Highly selective oxidation of organosilanes with a reusable nanoporous silver catalyst
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Room temperature highly selective oxidation of organosilanes to organosilanols and organosilyl ethers is achieved in liquid-phase with dealloyed nanoporous silver catalysts. In both cases, aromatic and aliphatic silanes can be effectively converted into the corresponding silanols and silyl ethers by using water and alcohols as oxidant, respectively. Moreover, hydrogen gas is the only by-product and the catalyst can be recycled for several times without evident loss of activity and selectivity.
- Li, Zhiwen,Zhang, Congcong,Tian, Jing,Zhang, Zhonghua,Zhang, Xiaomei,Ding, Yi
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- Iridium-catalyzed hydrogen production from hydrosilanes and water
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The iridium(III) complex [Ir(H)(CF3SO3)(NSiN)(coe)] (NSiN=fac-coordinated bis(pyridine-2-yloxy)methylsilyl, coe=cyclooctene) has been proven to be an effective catalyst precursor for hydrogen production from the hydrolysis of hydrosilanes at room temperature. The reaction performance depends both on the nature of the silane and the solvent. Interestingly, high turnover frequencies of around 105 h-1 were obtained by using Et2SiH2 or (Me2HSi)2O as hydrogen sources and THF as the solvent. Moreover a mechanistic insight into this Ir-catalyzed hydrogen generation process, based on both theoretical calculations and NMR spectroscopy, is reported. The overall catalytic cycle can be viewed as a two-stage process that involves water-promoted Si-H bond activation followed by water splitting by a proton transfer. From hydrosilanes to hydrogen: The iridium(III) complex [Ir(H)(CF3SO 3)(NSiN)(coe)] is an effective homogeneous catalyst precursor for hydrogen production from the hydrolysis of hydrosilanes (NSiN=fac-coordinated bis(pyridine-2-yloxy)methylsilyl, coe=cyclooctene).
- Garces, Karin,Fernandez-Alvarez, Francisco J.,Polo, Victor,Lalrempuia, Ralte,Perez-Torrente, Jesus J.,Oro, Luis A.
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p. 1691 - 1697
(2014/06/24)
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- Efficient fluoride-catalyzed conversion of CO2 to CO at room temperature
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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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supporting information
p. 6142 - 6147
(2014/05/20)
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- Nanogold-catalyzed cis -silaboration of alkynes with abnormal regioselectivity
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The first example of gold-catalyzed silaboration of alkynes with PhMe 2SiBpin is documented in the presence of supported gold nanoparticles. In the case of terminal alkynes, the reaction proceeds at ambient conditions in very good yields and th
- Gryparis, Charis,Stratakis, Manolis
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supporting information
p. 1430 - 1433
(2014/04/03)
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- Direct evidence for intermolecular oxidative addition of σ(Si-Si) bonds to gold
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Oxidative addition plays a major role in transition-metal catalysis, but this elementary step remains very elusive in gold chemistry. It is now revealed that in the presence of GaCl3, phosphine gold chlorides promote the oxidative addition of disilanes at low temperature. The ensuing bis(silyl) gold(III) complexes were characterized by quantitative 31P and 29Si NMR spectroscopy. Their structures (distorted Y shape) and the reaction profile of σ(Si-Si) bond activation were analyzed by DFT calculations. These results provide evidence for the intermolecular oxidative addition of σ(Si-Si) bonds to gold and open promising perspectives for the development of new gold-catalyzed redox transformations. Oxidative addition is the most elusive elementary step in reactions with gold. Now, evidence for the intermolecular oxidative addition of σ(Si-Si) bonds is reported. Phosphine gold chlorides readily reacted with disilanes at low temperature in the presence of GaCl3. The ensuing bis(silyl) gold(III) complexes were characterized by 31P and 29Si NMR spectroscopy, and their structures were analyzed by DFT calculations. Copyright
- Joost, Maximilian,Gualco, Pauline,Coppel, Yannick,Miqueu, Karinne,Kefalidis, Christos E.,Maron, Laurent,Amgoune, Abderrahmane,Bourissou, Didier
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p. 747 - 751
(2014/01/23)
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- Catalytic 1,4-selective hydrosilylation of pyridines and benzannulated congeners
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Radically different! The hydrosilylation of pyridines and quinolines is strictly 1,4-selective and likely involves an ionic one-step rather than the established radical two-step hydride transfer from a ruthenium(II) hydride complex onto the respective pyridinium and quinolinium ion intermediates (see scheme; ArF=3,5-(CF3)2C6H 3). Even 4-substituted substrates react highly regioselectively. Isoquinolines yield the 1,2-reduced heterocycles.
- Koenigs, C. David F.,Klare, Hendrik F. T.,Oestreich, Martin
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supporting information
p. 10076 - 10079
(2013/10/01)
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- Chemo- and regioselective catalytic reduction of N-heterocycles by silane
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The ruthenium complex [Cp(iPr3P)Ru(NCCH3) 2]+ (1) catalyzes the regioselective hydrosilylation of pyridines to 1,4-dihydropyridines. Substitution in the 3- and 5-positions is tolerated, whereas pyridines with substituents in the 2-, 4-, and 6-positions are not reduced. Reduction of functionalized pyridines having keto and ester substituents results in a mixture of products. N-Silyl-1,4-dihydropyridine reacts with ketones and aldehydes to give products of N-Si addition across the C=O bond. Hydrosilylation of pyridine in acetone results quantitatively in the addition product PhMe2SiO-CMe2-NC5H 6, which decomposes in hexane to give the parent dihydropyridine HNC5H6. The phenanthroline complex [Cp(phen)Ru(NCCH 3)2]+ (10) catalyzes regioselective 1,4-reduction of phenanthroline by a 3-4-fold excess of silane/water or silane/alcohol mixtures. The Cp* analogue [Cp*(ph n)Ru(NCCH 3)2]+ (9) catalyzes 1,4-regioselective monohydrosilylation of phenanthroline, quinoline, acridine, and 1,3,5-triazine and the 1,2-reduction of isoquinoline. In contrast, 2-substituted phenanthroline, pyrazine, 2-ethylpyridine, 2,6-lutidine, 2,4-lutidine, and pyrimidine are not reduced under these conditions by either of the catalysts studied.
- Lee, Sun-Hwa,Gutsulyak, Dmitry V.,Nikonov, Georgii I.
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p. 4457 - 4464
(2013/09/23)
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- Reactivity of a titanocene pendant Si-H group toward alcohols. Unexpected formation of siloxanes from the reaction of hydrosilanes and Ph3COH catalyzed by B(C6F5)3
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The reaction of [Cp(η5-C5H4CH 2SiMe2H)TiCl2] (1; Cp = η5- C5H5) and methanol in the presence of catalytic amounts of B(C6F5)3 afforded a complex with a pendant silyl ether group, [Cp(η5-C5H4CH 2SiMe2OMe)TiCl2] (2), in good yield. The analogous reaction of 1 and Ph3COH resulted in the unexpected formation of [CpTiCl2{μ-η5:η5- (C5H4)CH2SiMe2OSiMe 2CH2(C5H4)}TiCl2Cp] (4). The formation of siloxanes from the reaction of 2 equiv of hydrosilane with Ph3COH mediated by B(C6F5)3 has a general applicability and proceeds in two consecutive steps: (i) transfer of the hydroxyl group from the trityl moiety to the silicon atom and (ii) silylation of the silanol formed in situ with the second equivalent of hydrosilane. The different hydrosilane reactivity toward Ph3COH in comparison with other alcohols can be attributed to the easy generation of the borate salt [Ph3C]+[(C6F5)3B(μ-OH) B(C6F5)3]- (5) under catalytic conditions. The intramolecular Si-H and Ti-Cl exchange in 1 is catalyzed by B(C6F5)3 in the presence of no alcohol. This process affords presumably a transient titanocene hydrido chloride, which is either chlorinated to give [Cp(η5-C5H 4CH2SiMe2Cl)TiCl2] (3) in CD 2Cl2 or decomposes into several paramagnetic Ti(III) species in toluene-d8. Complex 3 was independently synthesized from 1 and Ph3CCl in a good yield.
- Strasak, Tomas,Sykora, Jan,Lamac, Martin,Kubista, Jiri,Horacek, Michal,Gyepes, Robert,Pinkas, Jiri
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p. 4122 - 4129
(2013/09/02)
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- Heterogeneous-gold-catalyzed acceptorless cross-dehydrogenative coupling of hydrosilanes and isocyanic acid generated in situ from urea
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Support structure: In the presence of gold nanoparticles supported on alumina (Au/Al2O3), various hydrosilanes can be converted into the corresponding silyl isocyanates using urea as an isocyanate source. The observed catalysis is truly heterogeneous, and the retrieved Au/Al 2O3 catalyst can be reused several times without any loss of its high catalytic performance. Copyright
- Taniguchi, Kento,Itagaki, Shintaro,Yamaguchi, Kazuya,Mizuno, Noritaka
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supporting information
p. 8420 - 8423
(2013/09/02)
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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
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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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- 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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p. 10751 - 10753,3
(2020/09/02)
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- Rhodium carbene complexes as versatile catalyst precursors for Si-H bond activation
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Rhodium(III) complexes comprising monoanionic C,C,C-tridentate dicarbene ligands activate Si-H bonds and catalyse the hydrolysis of hydrosilanes to form silanols and siloxanes with concomitant release of H2. In dry MeNO2, selective formation of siloxanes takes place, while changing conditions to wet THF produces silanols exclusively. Silyl ethers are formed when ROH is used as substrate, thus providing a mild route towards the protection of alcohols with H2 as the only by-product. With alkynes, comparably fast hydrosilylation takes place, while carbonyl groups are unaffected. Further expansion of the Si-H bond activation to dihydrosilanes afforded silicones and polysilyl ethers. Mechanistic investigations using deuterated silane revealed deuterium incorporation into the abnormal carbene ligand and thus suggests a ligand-assisted mechanism involving heterolytic Si-H bond cleavage. Ligand-assisted Si-H bond cleavage: Rhodium-catalysed Si-H bond activation provides a methodology for the silyl group to be transferred to oxygen centres, thus providing access to siloxanes and silanols (using H 2O), alkoxysilanes (using ROH) and to polysiloxanes, such as silicones, when using difunctional silanes. The process is pH neutral, avoids sensitive silylating agents and produces H2 as useful and exclusive side product. Copyright
- Krueger, Anneke,Albrecht, Martin
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experimental part
p. 652 - 658
(2012/03/08)
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