- Ga+-catalyzed hydrosilylation? about the surprising system Ga+/HSiR3/olefin, proof of oxidation with subvalent Ga+and silylium catalysis with perfluoroalkoxyaluminate anions
-
Already 1 mol% of subvalent [Ga(PhF)2]+[pf]- ([pf]- = [Al(ORF)4]-, RF = C(CF3)3) initiates the hydrosilylation of olefinic double bonds under mild conditions. Reactions with HSiMe3 and HSiEt3 as substrates efficiently yield anti-Markovnikov and anti-addit
- Barthélemy, Antoine,Glootz, Kim,Hanske, Annaleah,Krossing, Ingo,Scherer, Harald
-
p. 439 - 453
(2022/01/22)
-
- A New Protocol for Catalytic Reduction of Alkyl Chlorides Using an Iridium/Bis(benzimidazol-2′-yl)pyridine Catalyst and Triethylsilane
-
The reduction of alkyl chlorides using triethylsilane is investigated. Primary, secondary, tertiary, and benzylic C-Cl bonds are effectively converted into C-H bonds using an [IrCl(cod)] 2/2,6-bis(benzimidazol-2′-yl)pyridine catalyst system. This catalyst system is quite simple since the tridentate N-ligand can be easily prepared in one step from commercially available reagents.
- Fukuyama, Takahide,Hamada, Yuki,Ryu, Ilhyong
-
supporting information
p. 3404 - 3408
(2021/07/14)
-
- Reversible Silylium Transfer between P-H and Si-H Donors
-
The Mo=PR2 π* orbital in a Mo phosphenium complex acts as acceptor in a new PIII-based Lewis superacid. This Lewis acid (LA) participates in electrophilic Si-H abstraction from E3SiH to give a Mo-bound secondary phosphine ligand, Mo-PR2H. The resulting Et3Si+ ion remains associated with the Mo complex, stabilized by η1-P-H donation, yet undergoes rapid exchange with an η1-Si-H adduct of free silane in solution. The equilibrium between these two adducts presents an opportunity to assess the role of this new LA in catalytic reactions of silanes: is the LA acting as a catalyst or as an initiator? Preliminary results suggest that a cycle including the Mo-bound phosphine-silylium adduct dominates in the catalytic hydrosilylation of acetophenone, relative to a putative cycle involving the silane-silylium adduct or “free” silylium.
- Belli, Roman G.,Pantazis, Dimitrios A.,McDonald, Robert,Rosenberg, Lisa
-
supporting information
p. 2379 - 2384
(2020/12/07)
-
- Hydrosilylative reduction of carbon dioxide by a homoleptic lanthanum aryloxide catalyst with high activity and selectivity
-
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
-
supporting information
p. 7804 - 7809
(2021/06/16)
-
- Catalytic CO2 hydrosilylation with [Mn(CO)5Br] under mild reaction conditions
-
Carbon dioxide hydrosilylation with earth-abundant transition-metal catalysts is an attractive alternative for the design of greener and cost-effective synthetic strategies. Herein, simple [Mn(CO)5Br] is an efficient precatalyst in the hydrosilylation of carbon dioxide with Et3SiH under mild reaction conditions. Using THF as a solvent, triethylsilylformate Et3SiCH(O)O was obtained in 67% yield after 1 h at 50 °C and 4 bar of CO2 pressure. The selectivity of the reaction was tuned by changing the solvent to a mixture of THF and toluene producing bis(triethylsilyl)acetal (Et3SiO)2CH2 in 86% yield. The CO2 hydrosilylation was also effective at room temperature and atmospheric pressure using either THF or the mixture THF/toluene as the solvent resulting in high Et3SiH conversion (92%–99%) but with a decrease in the selectivity. Radical trapping experiments indicated the participation of radical species in the catalytic mechanism. To the best of our knowledge, this is the first report on CO2 hydrosilylation catalyzed by transition-metal radical intermediates.
- García, Juventino J.,González, Tania
-
supporting information
(2021/06/07)
-
- Rapid Broad Spectrum Detection of Carbapenemases with a Dual Fluorogenic-Colorimetric Probe
-
Carbapenems stand as one of the last-resort antibiotics; however, their efficacy is threatened by the rising number and rapid spread of carbapenemases. Effective antimicrobial stewardship thus calls for rapid tests for these enzymes to aid appropriate prescription and infection control. Herein, we report the first effective pan-carbapenemase reporter CARBA-H with a broad scope covering all three Ambler classes. Using a chemical biology approach, we demonstrated that the absence of the 1β-substituent in the carbapenem core is key to pan-carbapenemase recognition, which led to our rational design and probe development. CARBA-H provides a dual colorimetric-fluorogenic response upon carbapenemase-mediated hydrolysis. A clear visual readout can be obtained within 15 min when tested against a panel of carbapenemase-producing Enterobacteriaceae (CPE) clinical isolates that notably includes OXA-48 and OXA-181-producing strains. Furthermore, CARBA-H can be applied to the detection of carbapemenase activity in CPE-spiked urine samples.
- Ma, Chi-Wang,Ng, Kenneth King-Hei,Yam, Bill Hin-Cheung,Ho, Pak-Leung,Kao, Richard Yi-Tsun,Yang, Dan
-
supporting information
p. 6886 - 6894
(2021/05/29)
-
- Oxidation of Triorganosilanes and Related Compounds by Chlorine Dioxide
-
Abstract: Oxidation of triethylsilane, tert-butyldimethylsilane, dimethylphenylsilane, triphenylsilane, 1,1,1,2tetramethyl-2-phenyldisilane, tris(trimethylsilyl)silane, hexamethyldisilane, tetrakis(trimethylsilyl)silane, 1,1,3,3tetraisopropyldisiloxane with chlorine dioxide was carried out. The reaction products of studied triorganosilanes with chlorine dioxide in an acetonitrile solution were the corresponding silanols and siloxanes. A mechanism explaining the formation of products and the observed regularities of the oxidation of silanes with chlorine dioxide has been proposed. A thermochemical analysis of some possible pathways in the gas phase using methods G4, G3, M05, and in an acetonitrile solution by the SMD-M05 method was carried out. The oxidation process can occur both with the participation of ionic and radical intermediates, depending on the structure of the oxidized substrate and medium.
- Grabovskiy, S. A.,Kabal’nova, N. N.
-
p. 2391 - 2402
(2022/01/22)
-
- Novel Si(II)+and Ge(II)+Compounds as Efficient Catalysts in Organosilicon Chemistry: Siloxane Coupling Reaction ?
-
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
-
-
- Silylation of Alcohols, Phenols, and Silanols with Alkynylsilanes – an Efficient Route to Silyl Ethers and Unsymmetrical Siloxanes
-
The formation of several silyl ethers (alkoxysilanes, R3Si-OR') and unsymmetrical siloxanes (R3Si-O-SiR'3) can be catalyzed by the commercially available potassium bis(trimethylsilyl)amide (KHMDS). The reaction proceeds via direct dealkynative coupling between various alcohols or silanols and alkynylsilanes, with a simultaneous formation of gaseous acetylene as the sole by-product. The dehydrogenative and dealkenative coupling of alcohols or silanols are well-investigated, whilst the utilization of alkynylsilanes as silylating agents has never been comprehensively studied in this context. Overall, the presented system allows the synthesis of various attractive organosilicon compounds under mild conditions, making this approach an atom-efficient, environmentally benign, and sustainable alternative to existing synthetic solutions.
- Kuciński, Krzysztof,Stachowiak, Hanna,Hreczycho, Grzegorz
-
p. 4042 - 4049
(2020/07/04)
-
- Chemoselective Hydrosilylation of the α,β-Site Double Bond in α,β- And α,β,γ,δ-Unsaturated Ketones Catalyzed by Macrosteric Borane Promoted by Hexafluoro-2-propanol
-
The B(C6F5)3-catalyzed chemoselective hydrosilylation of α,β- and α,β,γ,δ-unsaturated ketones into the corresponding non-symmetric ketones in mild reaction conditions is developed. Nearly 55 substrates including those bearing reducible functional groups such as alkynyl, alkenyl, cyano, and aromatic heterocycles are chemoselectively hydrosilylated in good to excellent yields. Isotope-labeling studies revealed that hexafluoro-2-propanol also served as a hydrogen source in the process.
- Zhan, Xiao-Yu,Zhang, Hua,Dong, Yu,Yang, Jian,He, Shuai,Shi, Zhi-Chuan,Tang, Lei,Wang, Ji-Yu
-
p. 6578 - 6592
(2020/07/17)
-
- Catalytic Disproportionation of Formic Acid to Methanol by using Recyclable Silylformates
-
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
-
supporting information
p. 14019 - 14023
(2020/06/09)
-
- Cobalt-Catalyzed Selective Synthesis of Disiloxanes and Hydrodisiloxanes
-
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
-
p. 5552 - 5561
(2019/06/05)
-
- Nickel(0) catalyzed oxidation of organosilanes to disiloxanes by air as an oxidant
-
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
-
supporting information
p. 971 - 974
(2019/03/07)
-
- Si-H Bond Activation with Bullock's Cationic Tungsten(II) Catalyst: CO as Cooperating Ligand
-
An in-depth investigation of the reaction of tertiary hydrosilanes with [CpW(CO)2(IMes)]+[B(C6F5)4]- reveals a fundamentally new Si-H bond activation mode. Unlike the originally proposed oxidative addition of the Si-H bond to the tungsten(II) center, there is strong experimental and NMR spectroscopic evidence for the involvement of one of the CO ligands of the cationic complex in the Si-H bond breaking event. The Si-H bond is heterolytically cleaved to form a tungsten(II) hydride and a silylium ion, which is stabilized by one of the CO ligands. This reactive hydrosilane adduct was eventually isolated and characterized by X-ray diffraction analysis. Quantum-chemical calculations support a cooperative mechanism, but a stepwise process consisting of oxidative addition and subsequent tungsten-to-oxygen silyl migration in the tungsten(IV) silyl hydride is also energetically feasible. However, our combined spectroscopic and computational analysis favors the cooperative pathway. The newly identified hydrosilane adduct is the key intermediate of Bullock's ionic carbonyl hydrosilylation.
- Fuchs, Julien,Irran, Elisabeth,Hrobárik, Peter,Klare, Hendrik F. T.,Oestreich, Martin
-
p. 18845 - 18850
(2019/11/28)
-
- Breaking C-O Bonds with Uranium: Uranyl Complexes as Selective Catalysts in the Hydrosilylation of Aldehydes
-
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
-
p. 9025 - 9033
(2019/10/02)
-
- Benzoimidazole-Pyridylamido Zirconium and Hafnium Alkyl Complexes as Homogeneous Catalysts for Tandem Carbon Dioxide Hydrosilylation to Methane
-
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
-
p. 495 - 510
(2019/01/14)
-
- Axially Chiral, Electrophilic Fluorophosphonium Cations: Synthesis, Lewis Acidity, and Reactivity in the Hydrosilylation of Ketones
-
Axially chiral [(C6F5)3PF][B(C6F5)4] analogues based on dihydrophosphepines with a binaphthyl backbone were prepared and structurally characterized by X-ray diffraction analysis. Computational calculations of FIA and GEI values attest that these new fluorophosphonium cations have a higher Lewis acidity compared to the ubiquitous B(C6F5)3. Furthermore, application of these highly electrophilic compounds in the catalytic hydrosilylation of ketones and an investigation of the mechanism lead to a refined picture of the role of highly electrophilic fluorophosphonium cations.
- Süsse, Lars,Lafortune, James H. W.,Stephan, Douglas W.,Oestreich, Martin
-
supporting information
p. 712 - 721
(2019/02/17)
-
- Br?nsted Acid Catalyzed 1,2-Silyl Shift in Propargyl Silanes: Synthesis of Silyl Dienes and Silyl Indenes
-
A general method for generation of allyl carbenium ions from propargyl silanes via a 1,2-silyl shift by Br?nsted acids is reported. Two possible reaction pathways are described. Deprotonation results in silyl dienes with yields from 52% to 92%. Intramolecular Friedel-Crafts reactions of aryl-substituted systems give access to silyl indenes with yields of 18-90% depending on the substitution pattern. The obtained products have been shown to react as alkenyl silanes in Hiyama coupling and electrophilic substitution and as dienes in Diels-Alder cycloaddition.
- Purin?, Mikus,Mishnev, Anatoly,Turks, Maris
-
p. 3595 - 3611
(2019/03/11)
-
- Iron Catalyzed CO2 Activation with Organosilanes
-
Abstract: Iron nanoparticles generated in situ from [Fe3(CO)12] catalyzed CO2 reduction in the presence of Et3SiH as a reductant and tetrabutylammonium fluoride as a promoter to yield silyl formate (1s) under relatively mild reaction conditions. Additionally, when CO2 hydrosilylation was carried out in water, the product of CO2 reduction was formic acid. Additionally, a similar reaction using [Fe3(CO)12] as a catalytic precursor, PhSiH3 as a reductant, and CO2 in the presence of amines allowed the immediate formation of ureas at room temperature. Here, CO2 acted as a C1 building block for value-added products.
- Jurado-Vázquez, Tamara,García, Juventino J.
-
p. 1162 - 1168
(2018/02/22)
-
- Synthesis, characterization and catalytic oxidation of organosilanes with a novel multilayer polyoxomolybdate containing mixed-valence antimony
-
Oxidation of organosilanes is one of the pivotal reactions in organic synthesis and the corresponding products of silanols are widely as raw materials in industrial processes. In this paper, a new type of polyoxomolybdate containing mixed-valence antimony, [SbVSbIII4Mo18O66]7? (1a), has been isolated as tetramethyl ammonium salt in aqueous solution. The compound was structurally characterized by FT-IR, XPRD, TG, XPS, ESI–MS etc. It is the first time that the containing mixed-valence antimony polyoxomolybdate was used as a heterogeneous catalyst to efficaciously catalyze the oxidation of organosilanes to silanols under mild reaction conditions. Furthermore, the catalyst was stable and maintained its catalytic activity after three reaction cycles.
- Wang, Yaping,Lu, Jingkun,Ma, Xinyi,Niu, Yanjun,Singh, Vikram,Ma, Pengtao,Zhang, Chao,Niu, Jingyang,Wang, Jingping
-
p. 167 - 174
(2018/04/24)
-
- Copper-Catalyzed Oxidation of Hydrosilanes: A New Method for the Synthesis of Alkyl- and Siloxysilanols
-
A simple method for the preparation of silanols from the corresponding hydrosilanes is reported. The method employs a commercially available oxidizing system based on CuCO 3 / t -BuOOH (aq) under relatively mild conditions (80 °C, atmospheric pressure) with acetonitrile as the solvent. Furthermore, we present a method that permits the Si-H group to be oxidized to a Si-OH group not only in triethylsilane, but also in bis(trimethylsiloxy)methylsilane, a siloxy derivative of hydrosilane. The products were isolated in gram amounts in yields of 61-73%.
- Arzumanyan, Ashot V.,Goncharova, Irina K.,Novikov, Roman A.,Milenin, Sergey A.,Muzafarov, Aziz M.
-
supporting information
p. 489 - 492
(2017/11/15)
-
- Aerobic Co or Cu/NHPI-catalyzed oxidation of hydride siloxanes: Synthesis of siloxanols
-
A highly efficient preparative method for the synthesis of siloxanols based on aerobic Co(OAc)2 or Cu(OAc)2/NHPI-catalyzed oxidation of hydride siloxanes using "green", commercially available, simple inexpensive reagents and mild reaction conditions has been proposed. This is a general reaction for the synthesis of mono-, oligo- and polymeric siloxanols with various structures (linear, branched and cyclic).
- Arzumanyan, Ashot V.,Goncharova, Irina K.,Novikov, Roman A.,Milenin, Sergey A.,Boldyrev, Konstantin L.,Solyev, Pavel N.,Tkachev, Yaroslav V.,Volodin, Alexander D.,Smol'Yakov, Alexander F.,Korlyukov, Alexander A.,Muzafarov, Aziz M.
-
supporting information
p. 1467 - 1471
(2018/04/12)
-
- A convenient and clean synthetic method for borasiloxanes by Pd-catalysed reaction of silanols with diborons
-
Selective O-borylation of silanols with diborons took place in the presence of Pd catalysts to give the corresponding boryl silyl ethers in high yields.
- Yoshimura, Aya,Yoshinaga, Michiyo,Yamashita, Hiroshi,Igarashi, Masayasu,Shimada, Shigeru,Sato, Kazuhiko
-
p. 5822 - 5825
(2017/07/11)
-
- DMF-activated chlorosilane chemistry: Molybdenum-catalyzed reactions of R3SiH, DMF and R′3SiCl to initially form R′3SiOSiR′3 and R3SiCl
-
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.
-
p. 376 - 381
(2017/06/30)
-
- Transition-Metal-Free Catalytic Hydrodefluorination of Polyfluoroarenes by Concerted Nucleophilic Aromatic Substitution with a Hydrosilicate
-
A transition-metal-free catalytic hydrodefluorination (HDF) reaction of polyfluoroarenes is described. The reaction involves direct hydride transfer from a hydrosilicate as the key intermediate, which is generated from a hydrosilane and a fluoride salt. The eliminated fluoride regenerates the hydrosilicate to complete the catalytic cycle. Dispersion-corrected DFT calculations indicated that the HDF reaction proceeds through a concerted nucleophilic aromatic substitution (CSNAr) process.
- Kikushima, Kotaro,Grellier, Mary,Ohashi, Masato,Ogoshi, Sensuke
-
supporting information
p. 16191 - 16196
(2017/11/27)
-
- Accessing Two-Coordinate ZnII Organocations by NHC Coordination: Synthesis, Structure, and Use as π-Lewis Acids in Alkene, Alkyne, and CO2 Hydrosilylation
-
Discrete two-coordinate ZnII organocations of the type (NHC)Zn?R+ are reported, thanks to NHC stabilization. In preliminary reactivity studies, such entities, which are direct cationic analogues of long-known ZnR2 species,
- Specklin, David,Hild, Frédéric,Fliedel, Christophe,Gourlaouen, Christophe,Veiros, Luis F.,Dagorne, Samuel
-
supporting information
p. 15908 - 15912
(2017/11/15)
-
- Highly Selective Synthesis of Hydrosiloxanes by Au-Catalyzed Dehydrogenative Cross-Coupling Reaction of Silanols with Hydrosilanes
-
We report a highly selective synthesis of siloxane building blocks containing SiH2 or SiH functionalities. AuCl(PPh3)/PPh3 or AuCl(PPh3)/PnBu3 system catalyzed the reaction of trihydrosilanes with silanols giving SiH2-containing siloxanes exclusively. On the other hand, a highly selective reaction of dihydrosilanes with silanols to afford SiH-containing siloxanes was achieved by simply changing the phosphine ligand to a bidentate one, xantphos. Usefulness of SiH2-containing siloxanes was demonstrated by the synthesis of a trisiloxane, Et3SiOSi(Ph)(H)OSitBuMe2, and a pentasiloxane, Ph2Si(OSiHPhOSiEt3)2, bearing SiH functionalities.
- Satoh, Yasushi,Igarashi, Masayasu,Sato, Kazuhiko,Shimada, Shigeru
-
p. 1836 - 1840
(2017/08/14)
-
- SILOXANE COMPOUND PRODUCTION METHOD AND GOLD CATALYST USED THEREIN
-
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
- -
-
Paragraph 0054-0060; 0065
(2017/06/19)
-
- Catalytic reduction of CO2with organo-silanes using [Ru3(CO)12]
-
The reaction of carbon dioxide with Et3SiH in the presence of catalytic amounts of [Ru3(CO)12] as a catalytic precursor was achieved to produce silyl formate (Et3SiOCOH) 1s with a TON of 9000. A similar reaction in the presence of KF yielded potassium formate (8s) in a one-pot protocol with high selectivity using water or MeCN as the solvent. In the current report the complete reduction of carbon dioxide to methane was achieved, with the use of a more reactive silane (phenylsilane). A catalytically relevant species was the ruthenium cluster [H4Ru4(CO)12]. This is the second report on the hydrosilylation of carbon dioxide catalyzed by highly active and readily available ruthenium clusters and this is the first report of hydrosilylation of CO2to methane.
- Jurado-Vázquez, Tamara,Ortiz-Cervantes, Carmen,García, Juventino J.
-
-
- Selective Reduction of CO2 to CH4 by Tandem Hydrosilylation with Mixed Al/B Catalysts
-
This contribution reports the first example of highly selective reduction of CO2 into CH4 via tandem hydrosilylation with mixed main-group organo-Lewis acid (LA) catalysts [Al(C6F5)3 + B(C6F5)3] {[Al] + [B]}. As shown by this comprehensive experimental and computational study, in this unique tandem catalytic process, [Al] effectively mediates the first step of the overall reduction cycle, namely the fixation of CO2 into HCOOSiEt3 (1) via the LA-mediated C - O activation, while [B] is incapable of promoting the same transformation. On the other hand, [B] is shown to be an excellent catalyst for the subsequent reduction steps 2-4, namely the hydrosilylation of the more basic intermediates [1 to H2C(OSiEt3)2 (2) to H3COSiEt3 (3) and finally to CH4] through the frustrated Lewis pair (FLP)-type Si-H activation. Hence, with the required combination of [Al] and [B], a highly selective hydrosilylative reduction of CO2 system has been developed, achieving high CH4 production yield up to 94%. The remarkably different catalytic behaviors between [Al] and [B] are attributed to the higher overall Lewis acidity of [Al] derived from two conflicting factors (electronic and steric effects), which renders the higher tendency of [Al] to form stable [Al]-substrate (intermediate) adducts with CO2 as well as subsequent intermediates 1, 2, and 3. Overall, the roles of [Al] and [B] are not only complementary but also synergistic in the total reduction of CO2, which render both [Al]-mediated first reduction step and [B]-mediated subsequent steps catalytic.
- Chen, Jiawei,Falivene, Laura,Caporaso, Lucia,Cavallo, Luigi,Chen, Eugene Y.-X.
-
supporting information
p. 5321 - 5333
(2016/05/19)
-
- Pyridinium-phosphonium dications: Highly electrophilic phosphorus-based Lewis acid catalysts
-
Using commercially available 2-pyridyldiphenylphosphine (o-NC5H4)PPh2, a family of electrophilic phosphonium cations [(o-NC5H4)PFPh2]+ (2) and dications [(o-MeNC5H4)PRPh2]2+ (R = F (4); Me (5)) were prepared. The Lewis acidity of these pyridinium-phosphonium dications was probed in Friedel-Crafts dimerization, hydrodefluorination, hydrosilylation, dehydrocoupling and hydrodeoxygenation reactions. The influence of the counterion on the catalytic activity of the electrophilic phosphonium cations is also discussed.
- Bayne, Julia M.,Holthausen, Michael H.,Stephan, Douglas W.
-
p. 5949 - 5957
(2016/04/26)
-
- Selective N-methylation of aliphatic amines with CO2 and hydrosilanes using nickel-phosphine catalysts
-
A method using CO2 and PhSiH3 for the methylation of primary and secondary aliphatic amines catalyzed by Ni (0) complexes was developed, selectively producing the monomethylated products in moderate to good yields. For that purpose, two catalysts were used: [(dippe)Ni(μ-H)]2 and the commercially available Ni(COD)2/dcype, both of which were rather efficient in this process. With a slight experimental modification, the reaction allowed the production of monomethylated ureas in good yields by using low amounts of PhSiH3. On the basis of the experimental results, we propose a possible reaction mechanism for the formation of the new C-N bond.
- Gonzlez-Sebastin, Lucero,Flores-Alamo, Marcos,Garca, Juventino J.
-
p. 763 - 769
(2015/05/12)
-
- Aromaticity as stabilizing element in the bidentate activation for the catalytic reduction of carbon dioxide
-
A new transition-metal-free mode for the catalytic reduction of carbon dioxide via bidentate interaction has been developed. In the presence of Li2[1,2-C6H4(BH3)2], CO2 can be selectively transformed to either methane or methanol, depending on the reducing agent. The bidentate nature of binding is supported by X-ray analysis of an intermediate analogue, which experiences special stabilization due to aromatic character in the bidentate interaction. Kinetic studies revealed a first-order reaction rate. The transformation can be conducted without any solvent.
- Lu, Zhenpin,Hausmann, Heike,Becker, Sabine,Wegner, Hermann A.
-
supporting information
p. 5332 - 5335
(2015/05/13)
-
- METHOD OF PRODUCING ARYLSILANES AND CATALYST COMPOSITION FOR ARYLSILANES SYNTHESIS
-
PROBLEM TO BE SOLVED: To provide a new method of producing arylsilanes which can improve in terms of environmental compatibility, versatility, and efficiency. SOLUTION: By use of an iridium complex and a hydrogen acceptor, the oxidative coupling reaction between an aromatic hydrocarbon compound and a hydrosilane compound allows direct and efficient synthesis of arylsilanes. COPYRIGHT: (C)2015,JPO&INPIT
- -
-
Paragraph 0045; 0048; 0049
(2016/12/26)
-
- Photo Lewis acid generators: Photorelease of B(C6F5)3 and applications to catalysis
-
A series of molecules capable of releasing of the strong organometallic Lewis acid B(C6F5)3 upon exposure to 254 nm light have been developed. These photo Lewis acid generators (PhLAGs) can now serve as photoinitiators for several important B(C6F5)3-catalyzed reactions. Herein is described the synthesis of the triphenylsulfonium and diphenyliodonium salts of carbamato- and hydridoborates, their establishment as PhLAGs, and studies aimed at defining the mechanism of borane release. Factors affecting these photolytic reactions and the application of this concept to photoinduced hydrosilylation reactions and construction of siloxane scaffolds are also discussed.
- Khalimon, Andrey Y.,Shaw, Bryan K.,Marwitz, Adam J. V.,Piers, Warren E.,Blackwell, James M.,Parvez, Masood
-
supporting information
p. 18196 - 18206
(2015/10/28)
-
- Hydrosilylation of ketones, imines and nitriles catalysed by electrophilic phosphonium cations: Functional group selectivity and mechanistic considerations
-
The electrophilic phosphonium salt, [(C6F5)3PF][B(C6F5)4], catalyses the efficient hydrosilylation of ketones, imines and nitriles at room temperature. In the presence of this catalyst, adding one equivalent of hydrosilane to a nitrile yields a silylimine product, whereas adding a second equivalent produces the corresponding disilylamine. [(C6F5)3PCl][B(C6F5)4] and [(C6F5)3PBr][B(C6F5)4] are also synthesised and tested as catalysts. Competition experiments demonstrate that the reaction exhibits selectivity for the following functional groups in order of preference: ketone>nitrile>imine>olefin. Computational studies reveal the reaction mechanism to involve initial activation of the Si-H bond by its interaction with the phosphonium centre. The activated complex then acts cooperatively on the unsaturated substrate. Proceed with cation: The electrophilic phosphonium salt, [(C6F5)3PF][B(C6F5)4], catalyses the efficient hydrosilylation of ketones, imines and nitriles at room temperature. In the presence of this catalyst, adding one equivalent of hydrosilane to a nitrile yields a silylimine product, whereas adding a second equivalent produces the corresponding disilylamine.
- Pérez, Manuel,Qu, Zheng-Wang,Caputo, Christopher B.,Podgorny, Vitali,Hounjet, Lindsay J.,Hansen, Andreas,Dobrovetsky, Roman,Grimme, Stefan,Stephan, Douglas W.
-
supporting information
p. 6491 - 6500
(2015/04/22)
-
- An efficient catalytic approach for the synthesis of unsymmetrical siloxanes
-
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
-
-
- A novel iron complex for highly efficient catalytic hydrogen generation from the hydrolysis of organosilanes
-
Hydrolytic oxidation of organosilanes based on an iron catalyst is described for the first time. The novel iron complex, [Fe(C6H 5N2O)(CO)(MeCN)3][PF6], exhibits excellent mediating power in the catalytic hydrolysis of organosilanes to produce dihydrogen and organosilanols with turnover numbers approaching 10 4 and turnover frequencies in excess of 102 min -1 under ambient conditions.
- Liang Teo, Alan Kay,Fan, Wai Yip
-
supporting information
p. 7191 - 7194
(2014/07/07)
-
- An efficient method for the preparation of silyl esters of diphosphoric, phosphoric, and phosphorous acid
-
Tetrakis(trialkylsilyl) diphosphate (alkyl = Me, Et, iPr, tBu) can be obtained in quantitative yield by reacting commercial disodium dihydrogen diphosphate with the respective trialkyl chlorosilane in a triphasic system with formamide. The alkylsilane residues of the diphosphate silyl esters can be either partially or completely hydrolyzed without concurrent cleavage of the P-O-P bond of the diphosphate moiety. The method can be expanded to efficiently produce other persilylated or partially silylated phosphates and phosphites.
- Wessjohann, Ludger A.,Dessoy, Marco A.
-
p. 133 - 137
(2014/02/14)
-
- Gold nanoparticles supported on the periodic mesoporous organosilica SBA-15 as an efficient and reusable catalyst for selective oxidation of silanes to silanols
-
Gold nanoparticles are confined and stabilized within the channels of SBA-15 through the poly(ionic liquid) brushes that are anchored onto the pore walls of SBA-15. The supported gold catalyst exhibited remarkably high catalytic activities for selective oxidation of silanes into silanols using water as an oxidant without the use of organic solvents.
- Ma, Lina,Leng, Wenguang,Zhao, Yaopeng,Gao, Yanan,Duan, Hongdong
-
p. 6807 - 6810
(2014/02/14)
-
- Iridium-catalyzed hydrogen production from hydrosilanes and water
-
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.
-
p. 1691 - 1697
(2014/06/24)
-
- PROCESS FOR PRODUCING HYDROLYSIS-RESISTANT SILICONE COMPOUNDS
-
In one aspect, the invention relates to hydrolysis-resistant silicone compounds. In particular, disclosed are sterically hindered hydrolysis-resistant silicone compounds and improved purity hydrolysis-resistant silicone compounds. Also disclosed are processes for making hydrolysis-resistant silicone compounds; the products of the disclosed processes; compositions and polymers comprising the disclosed compounds and products of the disclosed processes; and ophthalmic lenses, for example contact lenses, intraocular lenses, artificial cornea, and spectacle lenses, comprising the disclosed compositions, disclosed polymers, disclosed compounds, and products of the disclosed processes. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present invention.
- -
-
Paragraph 0275
(2014/05/20)
-
- Salt-free preparation of trimethylsilyl ethers by B(C6F 5)3-catalyzed transfer silylation by using a Me 3SiH surrogate
-
An unprecedented transfer silylation of alcohols catalyzed by the strong Lewis acid B(C6F5)3 is described. Gaseous Me3SiH is released in situ by B(C6F5) 3-catalyzed decomposition of 3-trimethylsilylcyclohexa-1,4-diene and subsequently reacts with an alcohol in a dehydrogenative Si-O coupling promoted by the same boron catalyst. Benzene and dihydrogen are formed during the reaction, but no salt waste is. This expedient protocol is applicable to several silicon groups, and the preparation of trimethylsilyl ethers presented here is potentially useful for alcohol derivatization prior to GLC analysis. Copyright
- Simonneau, Antoine,Friebel, Jonas,Oestreich, Martin
-
supporting information
p. 2077 - 2083
(2014/04/17)
-
- Nickel-catalyzed hydrosilylation of CO2 in the Presence of Et3B for the synthesis of formic acid and related formates
-
The reaction of CO2 with Et3SiH catalyzed by the nickel complex [(dippe)Ni(μ-H)]2 (1) afforded the reduction products Et3SiOCH2OSiEt3 (12%), Et 3SiOCH3 (3%), and CO, which were characterized by standard spectroscopic methods. Part of the generated CO was found as the complex [(dippe)Ni(CO)]2 (2), which was characterized by single-crystal X-ray diffraction. When the same reaction was carried out in the presence of a Lewis acid, such as Et3B, the hydrosilylation of CO2 efficiently proceeded to give the silyl formate (Et3SiOC(O)H) in high yields (85-89%), at 80 C for 1 h. Further reactivity of the silyl formate to yield formic acid, formamides, and alkyl formates was also investigated.
- Gonzalez-Sebastian, Lucero,Flores-Alamo, Marcos,Garcia, Juventino J.
-
p. 7186 - 7194
(2014/01/06)
-
- 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
-
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
-
p. 4122 - 4129
(2013/09/02)
-
- Competitive aryl-fluorine and aryl-halogen (Halogen = Cl, Br) bond cleavage with iridium porphyrin complexes
-
Base-promoted competitive Ar-F and Ar-X (X = Cl, Br) bond cleavage with iridium porphyrin complexes was investigated. Mechanistic studies suggested that Ir(ttp)- (ttp = 5,10,15,20-tetra-p-tolylporphyrinato dianion) cleaves the Ar-F bond via nucleophilic aromatic substitution and Ir 2(ttp)2 cleaves the Ar-X (X = Cl, Br) bond via metalloradical ipso substitution. Therefore, a stronger base, polar solvent, lower temperature, and iridium anion precursor favor Ar-F bond cleavage, while a weaker base, nonpolar solvent, higher temperature, and Ir2(ttp) 2 precursor favor Ar-X (X = Cl, Br) bond cleavage.
- Qian, Ying Ying,Li, Bao Zhu,Chan, Kin Shing
-
supporting information
p. 1567 - 1570
(2013/05/08)
-
- METHODS AND COMPOUNDS FOR PHOTO LEWIS ACID GENERATION AND USES THEREOF
-
There are disclosed masked Lewis acids into compounds in which the Lewis acid can be released by exposure of the compound to light, especially ultraviolet light. These compounds can be represented by the following formula (I): ([(AEX(3-n))(n+1)Yn](n+1)-)m(Qm+)(n+1) (I). wherein briefly, E represents boron or aluminium, X is an aryl group and Y is -Ar'EAX,. These compounds are used as catalyst for hydrosilylation reaction, crosslinking of polymers, or ester deprotection reactions as photo Lewis acid generator (PhLAG).
- -
-
Page/Page column 37; 38
(2013/10/21)
-
- Catalytic synthesis of silyl formates with 1 atm of CO2 and their utilization for synthesis of formyl compounds and formic acid
-
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
-
p. 347 - 352
(2013/02/22)
-
- Gold nanoparticles-catalyzed activation of 1,2-disilanes: Hydrolysis, silyl protection of alcohols and reduction of tert-benzylic alcohols
-
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
-
p. 10751 - 10753,3
(2020/09/02)
-