- Silsesquioxyl rhodium(i) complexes - Synthesis, structure and catalytic activity
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The first bi- and mononuclear rhodium(i) complexes [{Rh(μ-OSi 8O12(i-Bu)7)(cod)}2] (5), [Rh(cod)(PCy3)(OSi8O12(i-Bu)7)] (6) with a hindered hepta(iso-butyl)silsesquiox
- Marciniec, Bogdan,Kownacki, Ireneusz,Franczyk, Adrian,Kubicki, MacIej
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- The two faces of platinum hydrospirophosphorane complexes—Not only relevant catalysts but cytotoxic compounds as well
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Platinum complexes [PtCl2(L)] L = L1, L2 with symmetrical HP (OCH2CMe2NH)2 (L1) and unsymmetrical HP(OCMe2CMe2O)(OCH2CMe2NH) (L2) hydrospirophosphorane (HSP) ligands were demonstrated to play a dual role of catalysts and cytotoxic compounds as well. The structure of new complex [PtCl2(L2)] was confirmed by physicochemical and spectroscopic methods, as well as single X-ray diffraction studies for [PtCl2{P (OCMe2CMe2O)(OCH2CMe2NH2)}]. HSP ligand coordinated to the platinum center in bidentate κ2-P,NH2 chelating mode of fashion. Both complexes were found to exhibit catalytic activity for Heck cross-coupling reactions of iodobenzene with substituted styrenes, with good conversion and yield of stilbenes. Moreover, complexes have been applied as excellent catalysts for highly regioselective hydrosilylation of aromatic and aliphatic terminal olefins, and acetylenes terminal and internal as well. On the other hand, the preliminary biological studies revealed that in the presence of foretinib, drug candidate in clinical trials for the treatment of cancer, platinum complexes revealed increased synergistic effect and efficiently decreased the number of viable cells of triple negative breast cancer MDA-MB-231 cell line.
- Skar?yńska, Anna,Kowalczyk, Marta,Majchrzak, Mariusz,Pi?tka, Marta,Augustyniak, Adam W.,Siczek, Mi?osz,W?odarczyk, Kinga,Simiczyjew, Aleksandra,Nowak, Dorota
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- Caged Iridium Catalyst for Hydrosilylation of Alkynes with High Site Selectivity
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The proximity and orientation of the reacting groups can be different in organic cages from in free solution, thus affecting the selectivity of the reaction. Herein, we reported a synthetic strategy to encapsulate iridium nanoparticles (Ir-NP@COP1-T) within organic cages in the homogeneous solution. Ir-NP@COP1-T showed good selectivity in the hydrosilylation reaction of alkynes. Our work provides a new perspective to the catalysis field by using soluble microporous cages as support for inorganic nano particles.
- Gu, Defa,Li, Qiaosheng,Liu, Yuzhou,Yu, Dongdong
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- Asymmetric Hydrosilylation of β-Silyl Styrenes Catalyzed by a Chiral Palladium Complex
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A palladium complex coordinated with a chiral SIPHOS ligand was evaluated as an efficient catalyst for asymmetric hydrosilylation of β-silyl styrenes with trichlorosilane and 23 1,2-bis(silyl) chiral compounds were produced. Good to excellent enantioselec
- He, Yu-Han,Ji, Yang,Li, Rui,Su, Yan,Wang, Yi-Fan
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- Rh(I)/(III)-N-Heterocyclic Carbene Complexes: Effect of Steric Confinement Upon Immobilization on Regio- and Stereoselectivity in the Hydrosilylation of Alkynes
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Rh(I) NHC and Rh(III) Cp* NHC complexes (Cp=pentamethylcyclopentadienyl, NHC=N-heterocyclic carbene=pyrid-2-ylimidazol-2-ylidene (Py?Im), thiophen-2-ylimidazol-2-ylidene) are presented. Selected catalysts were selectively immobilized inside the mesopores
- Atwi, Boshra,Bauer, Matthias,Buchmeiser, Michael R.,Frey, Wolfgang,Nowakowski, Michal,Panyam, Pradeep K. R.,Ziegler, Felix
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p. 17220 - 17229
(2021/11/10)
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- Manganese-Catalyzed Dehydrogenative Silylation of Alkenes following Two Parallel Inner-Sphere Pathways
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We report on an additive-free Mn(I)-catalyzed dehydrogenative silylation of terminal alkenes. The most active precatalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid Si-H bond cleavage of the silane HSiR3 forming the active 16e- Mn(I) silyl catalyst [Mn(dippe)(CO)2(SiR3)] together with liberated butanal. A broad variety of aromatic and aliphatic alkenes was efficiently and selectively converted into E-vinylsilanes and allylsilanes, respectively, at room temperature. Mechanistic insights are provided based on experimental data and DFT calculations revealing that two parallel reaction pathways are operative: an acceptorless reaction pathway involving dihydrogen release and a pathway requiring an alkene as sacrificial hydrogen acceptor.
- Weber, Stefan,Glavic, Manuel,St?ger, Berthold,Pittenauer, Ernst,Podewitz, Maren,Veiros, Luis F.,Kirchner, Karl
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p. 17825 - 17832
(2021/11/04)
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- Iridium(i) complexes bearing hemilabile coumarin-functionalised N-heterocyclic carbene ligands with application as alkyne hydrosilylation catalysts
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A set of iridium(i) complexes of formula IrCl(κC,η2-IRCouR′)(cod) or IrCl(κC, η2-BzIRCouR′)(cod) (cod = 1,5-cyclooctadiene; Cou = coumarin; I = imidazolin-2-carbene; BzI = benzimidazolin-2-carbene) have beeen prepared from the corresponding azolium salt and [Ir(μ-OMe)(cod)]2 in THF at room temperature. The crystalline structures of 4b and 5b show a distorted trigonal bipyramidal configuration in the solid state with a coordinated coumarin moiety. In contrast, an equilibrium between this pentacoordinated structure and the related square planar isomer is observed in solution as a consequence of the hemilability of the pyrone ring. Characterization of both species by NMR was achieved at the low and high temperature limits, respectively. In addition, the thermodynamic parameters of the equilibrium, ΔHR and ΔSR, were obtained by VT 1H NMR spectroscopy and fall in the range 22-33 kJ mol-1 and 72-113 J mol-1 K-1, respectively. Carbonylation of IrCl(κC,η2-BzITolCou7,8-Me2)(cod) resulted in the formation of a bis-CO derivative showing no hemilabile behaviour. The newly synthesised complexes efficiently catalyze the hydrosilylation of alkynes at room temperature with a preference for the β-(Z) vinylsilane isomer.
- ?zdemir, Ismail,Alici, Bülent,Castarlenas, Ricardo,Karata?, Mert Olgun,Pérez-Torrente, Jesús J.,Passarelli, Vincenzo
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p. 11206 - 11215
(2021/08/24)
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- Continuous-flow Si-H functionalizations of hydrosilanesviasequential organolithium reactions catalyzed by potassiumtert-butoxide
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We herein report an atom-economic flow approach to the selective and sequential mono-, di-, and tri-functionalizations of unactivated hydrosilanesviaserial organolithium reactions catalyzed by earth-abundant metal compounds. Based on the screening of various additives, we found that catalytic potassiumtert-butoxide (t-BuOK) facilitates the rapid reaction of organolithiums with hydrosilanes. Using a flow microreactor system, various organolithiums bearing functional groups were efficiently generatedin situunder mild conditions and consecutively reacted with hydrosilanes in the presence oft-BuOK within 1 min. We also successfully conducted the di-funtionalizations of dihydrosilane by sequential organolithium reactions, extending to a gram-scale-synthesis. Finally, the combinatorial functionalizations of trihydrosilane were achieved to give every conceivable combination of tetrasubstituted organosilane libraries based on a precise reaction control using an integrated one-flow system.
- Lee, Hyune-Jea,Kwak, Changmo,Kim, Dong-Pyo,Kim, Heejin
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p. 1193 - 1199
(2021/02/26)
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- Copper-Photocatalyzed Hydrosilylation of Alkynes and Alkenes under Continuous Flow
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Herein, the photocatalytic hydrosilylation of alkynes and alkenes under continuous flow conditions is described. By using 0.2 mol % of the developed [Cu(dmp)(XantphosTEPD)]PF6 under blue LEDs irradiation, a large panel of alkenes and alkynes was hydrosilylated in good to excellent yields with a large functional group tolerance. The mechanism of the reaction was studied, and a plausible scenario was suggested.
- Zhong, Mingbing,Pannecoucke, Xavier,Jubault, Philippe,Poisson, Thomas
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p. 11818 - 11822
(2021/07/10)
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- Direct Access to α,β-Unsaturated Ketones via Rh/MgCl2-Mediated Acylation of Vinylsilanes
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We report herein the facile and practical construction of α,β-unsaturated ketones via rhodium-catalyzed direct acylation of vinylsilanes with readily available and abundant carboxylic acids. This protocol features access to a diverse array of synthetically useful functionalities with moderate to excellent yields. More importantly, the late-stage functionalization of pharmaceuticals was also realized with synthetically useful yield.
- Chen, Zi-Yan,Deng, Xue-Zu,Song, Yang,Xue, Fei,Yamane, Motoki,Yue, Yan-Ni
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p. 12693 - 12704
(2021/09/28)
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- Stereo-controlledanti-hydromagnesiation of aryl alkynes by magnesium hydrides
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A concise protocol foranti-hydromagnesiation of aryl alkynes was established using 1?:?1 molar combination of sodium hydride (NaH) and magnesium iodide (MgI2) without the aid of any transition metal catalysts. The resulting alkenylmagnesium intermediates could be trapped with a series of electrophiles, thus providing facile accesses to stereochemically well-defined functionalized alkenes. Mechanistic studies by experimental and theoretical approaches imply that polar hydride addition from magnesium hydride (MgH2) is responsible for the process.
- Chiba, Shunsuke,Li, Yihang,Ong, Derek Yiren,Pang, Jia Hao,Takita, Ryo,Wang, Bin,Watanabe, Kohei
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p. 5267 - 5272
(2020/06/04)
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- Carboxylate-Assisted β-(Z) Stereoselective Hydrosilylation of Terminal Alkynes Catalyzed by a Zwitterionic Bis-NHC Rhodium(III) Complex
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The zwitterionic compound [Cp*RhCl{(MeIm)2CHCOO}] is an efficient catalyst for the hydrosilylation of terminal alkynes with excellent regio- and stereoselectivity toward the less thermodynamically stable β-(Z)-vinylsilane isomer under mild reaction conditions. A broad range of linear 1-alkynes, cycloalkyl acetylenes, and aromatic alkynes undergo the hydrosilylation with HSiMe2Ph to afford the corresponding β-(Z)-vinylsilanes in quantitative yields in short reaction times. The reaction of aliphatic alkynes with HSiEt3 is slower, resulting in a slight decrease of selectivity toward the β-(Z)-vinylsilane product, which is still greater than 90%. However, a significant selectivity decrease is observed in the hydrosilylation of aromatic alkynes because of the β-(Z) → β-(E) vinylsilane isomerization. Moreover, the hydrosilylation of bulky alkynes, such as t-Bu-CCH or Et3SiCCH, is unselective. Experimental evidence suggests that the carboxylate function plays a key role in the reaction mechanism, which has been validated by means of density functional theory calculations, as well as by mass spectrometry and labeling studies. On the basis of previous results, we propose an ionic outer-sphere mechanism pathway in which the carboxylate fragment acts as a silyl carrier. Namely, the hydrosilylation mechanism entails the heterolytic activation of the hydrosilane assisted by the carboxylate function to give the hydrido intermediate [Cp*RhH{(MeIm)2CHCOO-SiR3}]+. The transference of the silylium moiety from the carboxylate to the alkyne results in the formation of a flat β-silyl carbocation intermediate that undergoes a hydride transfer from the Rh(III) center to generate the vinylsilane product. The outstanding β-(Z) selectivity results from the minimization of the steric interaction between the silyl moiety and the ligand system in the hydride transfer transition state.
- Puerta-Oteo, Raquel,Munarriz, Julen,Polo, Víctor,Jiménez, M. Victoria,Pérez-Torrente, Jesús J.
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p. 7367 - 7380
(2020/07/21)
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- A Platinum Molecular Complex Immobilised on the Surface of Graphene as Active Catalyst in Alkyne Hydrosilylation
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A platinum complex bearing a N-heterocyclic carbene (NHC) ligand functionalised with a pyrene-tag is immobilised onto the surface of reduced graphene oxide (rGO). The hybrid material composed of an organometallic complex and a graphene derivative is ready
- Mollar-Cuni, Andres,Borja, Pilar,Martin, Santiago,Guisado-Barrios, Gregorio,Mata, Jose A.
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p. 4254 - 4262
(2020/06/08)
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- A Rh(I) complex with an annulated N-heterocyclic carbene ligand for E-selective alkyne hydrosilylation
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A Rh(I) complex supported by a fused π-conjugated imidazo[1,2-a][1,8]naphthyridine-based N-heterocyclic carbene ligand with a Dipp attachment on the imidazole nitrogen has been synthesized and structurally characterized. The title complex is found to be a
- Tyagi, Akshi,Yadav, Suman,Daw, Prosenjit,Ravi, Chitrakar,Bera, Jitendra K.
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p. 167 - 174
(2019/05/15)
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- Ru-Catalyzed Migratory Geminal Semihydrogenation of Internal Alkynes to Terminal Olefins
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Semihydrogenation of alkynes to alkenes represents a fundamentally useful transformation. In addition to the well-known cis- and trans-semihydrogenation, herein a geminal semihydrogenation of internal alkynes featuring 1,2-migration is described, which pr
- Song, Lijuan,Feng, Qiang,Wang, Yong,Ding, Shengtao,Wu, Yun-Dong,Zhang, Xinhao,Chung, Lung Wa,Sun, Jianwei
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p. 17441 - 17451
(2019/11/03)
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- Ligand-Dependent-Controlled Copper-Catalyzed Regio- And Stereoselective Silaboration of Alkynes
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A copper-catalyzed highly regio- and stereoselective silaboration of alkynes was developed. In this work, direct cis-difunctionalization of alkynes was realized with silaboronate reagent and copper catalyst in aprotic solvents. The regiodivergent silabora
- Zhao, Meng,Shan, Cui-Cui,Wang, Zi-Lu,Yang, Chao,Fu, Yao,Xu, Yun-He
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supporting information
p. 6016 - 6020
(2019/08/26)
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- Mononuclear ruthenium complex and organic synthesis reaction using same
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A neutral or cationic mononuclear ruthenium divalent complex represented by formula (1) can actualize exceptional catalytic activity in at least one reaction among a hydrosilylation reaction, hydrogenation reaction, and carbonyl compound reduction reaction. (In the formula, R1-R6 each independently represent a hydrogen atom or an alkyl group, aryl group, aralkyl group, organooxy group, monoorganoamino group, diorganoamino group, monoorganophosphino group, diorganophosphino group, monoorganosilyl group, diorganosilyl group, triorganosilyl group, or organothio group optionally substituted by X; at least one pair comprising any of R1-R3 and any of R4-R6 together represents a crosslinkable substituent; X represents a halogen atom, organooxy group, monoorganoamino group, diorganoamino group, or organothio group; L each independently represent a two-electron ligand other than CO and thiourea ligands; two L may bond to each other; and m represents an integer of 3 or 4.)
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Page/Page column 32; 33; 34
(2018/03/26)
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- Direct Silyl-Heck Reaction of Chlorosilanes
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A nickel complex/Lewis acid combination effectively catalyzed the direct silyl-Heck reaction of chlorosilanes, which are key raw materials in the organosilicon industry, to give synthetically important alkenylsilane products. Trichlorosilanes, dichlorosil
- Matsumoto, Kazuhiro,Huang, Jiadi,Naganawa, Yuki,Guo, Haiqing,Beppu, Teruo,Sato, Kazuhiko,Shimada, Shigeru,Nakajima, Yumiko
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supporting information
p. 2481 - 2484
(2018/04/27)
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- Visible light accelerated hydrosilylation of alkynes using platinum-[acyclic diaminocarbene] photocatalysts
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Platinum-[diaminocarbene] complexes work as transition-metal photocatalysts for the hydrosilylation of alkynes. A catalytic system operates under visible light irradiation (blue LED) enabling the conversion of a range of terminal and internal alkynes to r
- Gee, Jack C.,Fuller, Beth A.,Lockett, Hannah-Marie,Sedghi, Gita,Robertson, Craig M.,Luzyanin, Konstantin V.
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supporting information
p. 9450 - 9453
(2018/08/28)
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- Copper-Catalyzed Cross-Coupling of Vinyliodonium Salts and Zinc-Based Silicon Nucleophiles
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A silylation of vinyliodonium salts using zinc-based silicon reagents as nucleophiles is reported. This cross-coupling is catalyzed by copper, and vinylsilanes are obtained in high yield likely following a Cu(I)/Cu(III) reaction mechanism. The procedure i
- Zhang, Liangliang,Oestreich, Martin
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p. 8061 - 8063
(2019/01/14)
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- Additive-modulated switchable reaction pathway in the addition of alkynes with organosilanes catalyzed by supported Pd nanoparticles: Hydrosilylation: versus semihydrogenation
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We herein report supported Pd nanoparticles on N,O-doped hierarchical porous carbon as a single operation catalyst-enabled additive-modulated reaction pathway for alkynes addition with organosilanes between hydrosilyation and semihydrogenation. In the case of alkynes hydrosilylation, a simple iodide ion as an additive has a promotion effect on the activity and regio- and stereoselectivity, where iodide can coordinate with Pd NPs via strong δ donation to increase the electron density of the Pd atom, resulting in an increased ability for the oxidative addition of hydrosilane as the rate-determining step to make the reaction proceed efficiently to afford vinylsilanes in high yields with excellent regio- and stereoselectivity. For the catalytic transfer semihydrogenation of alkynes, water was introduced to mix with organosilane to form a silanol together with the generation of hydrogen atoms on the Pd NPs surface or the liberation of H2 gas as a reducing agent, whereby the quantitative reduction of alkynes was achieved with exclusive selectivity to alkenes. In both cases, the catalyst could be recycled several times without a significant loss in activity or selectivity. A broad range of alkyl and aryl alkynes with various functional groups are compatible with the reaction conditions. The role the additive exerted in each reaction was extensively investigated through control experiments as well as the kinetic isotopic effect along with spectroscopic characterization. In addition, the respective mechanism operating in both reactions was proposed.
- Duan, Yanan,Ji, Guijie,Zhang, Shaochun,Chen, Xiufang,Yang, Yong
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p. 1039 - 1050
(2018/03/05)
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- In Situ Generation of Silylzinc by Si?B Bond Activation Enabling Silylzincation and Silaboration of Terminal Alkynes
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A new protocol has been designed for the in situ generation of unstable Si?Zn species through the reaction of dialkylzinc, phosphine, and silylborane (Si?B). Successive reactions with various terminal alkynes using this protocol enabled highly controllable regio-/stereo-/chemoselective silylzincation and silaboration on demand without the need for a transition-metal catalyst.
- Nagashima, Yuki,Yukimori, Daiki,Wang, Chao,Uchiyama, Masanobu
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supporting information
p. 8053 - 8057
(2018/06/04)
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- Immobilization of Pyrene-Adorned N-Heterocyclic Carbene Complexes of Rhodium(I) on Reduced Graphene Oxide and Study of their Catalytic Activity
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Two pyrene-tagged N-heterocyclic carbene (NHC) complexes of rhodium(I) were obtained and characterized. The two complexes were supported onto reduced graphene oxide (rGO), generating two new materials in which the molecular complexes are immobilized by π–
- Ruiz-Botella, Sheila,Peris, Eduardo
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p. 1874 - 1881
(2017/12/07)
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- A recyclable and reusable K2PtCl4/Xphos-SO3Na/PEG-400/H2O system for highly regio- and stereoselective hydrosilylation of terminal alkynes
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K2PtCl4/Xphos-SO3Na in a mixture of poly(ethylene glycol) (PEG-400) and water is shown to be a highly regio- and stereoselective catalyst for the hydrosilylation of terminal alkynes with hydrosilanes. The reaction could be conducted under mild conditions, yielding a variety of functionalized β-(E)-vinylsilanes in good to excellent yields with a total β-(E)-selectivity. The isolation of the products is readily performed by extraction with cyclohexane and more importantly, both expensive K2PtCl4 and Xphos-SO3Na in a PEG-400/H2O system could be easily recycled and reused at least eight times without any loss of catalytic activity.
- Xu, Caifeng,Huang, Bin,Yan, Tao,Cai, Mingzhong
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supporting information
p. 391 - 397
(2018/02/07)
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- Highly selective hydrosilylation of olefins and acetylenes by platinum(0) complexes bearing bulky N-heterocyclic carbene ligands
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Platinum complexes bearing bulky N-heterocyclic carbene (NHC) ligands, i.e., [Pt(IPr?)(dvtms)] (where, IPr? = 1,3-bis{2,6-bis(diphenylmethyl)-4-methylphenyl}imidazol-2-ylidene) and [Pt(IPr?OMe)(dvtms)] (where, IPr?OMe = 1,3-bis{2,6-bis(diphenylmethyl)-4-m
- Zak,Bo?t,Kubicki,Pietraszuk
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supporting information
p. 1903 - 1910
(2018/02/17)
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- A Ligand-Free Pt3Cluster Catalyzes the Markovnikov Hydrosilylation of Alkynes with up to 106Turnover Frequencies
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The Pt-catalyzed hydrosilylation of alkynes is the procedure of choice to obtain vinylsilanes, and is claimed to be the most relevant application of Pt in organic synthesis. More than half a century after its discovery, only β-vinylsilanes (anti-Markovnikov addition) are obtained with simple Pt catalysts, whereas α-vinylsilanes (Markovnikov addition) remain elusive compounds. Here the catalysis of the Markovnikov hydrosilylation of terminal alkynes by Pt3clusters, in parts-per-million amounts, to give a wide variety of α-vinylsilanes in reasonable isolated yields and with turnover frequencies that can reach up to one million per hour is reported. Moreover, these α-vinylsilanes are reactive in well-stablished C?C bond-forming cascade reactions, in which the corresponding β-isomers are unreactive. Besides its efficiency and synthetic usefulness, this catalytic system is an excellent example of how the atom-by-atom aggregation of a catalytic metal leads to a different selectivity for a given reaction.
- Rivero-Crespo, Miguel A.,Leyva-Pérez, Antonio,Corma, Avelino
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p. 1702 - 1708
(2017/02/10)
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- Metal Complexes of a Redox-Active [1]Phosphaferrocenophane: Structures, Electrochemistry and Redox-Induced Catalysis
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The synthesis and characterisation of several metal complexes of a redox-active, mesityl(Mes)-substituted [1]phosphaferrocenophane, FcPMes (1), are reported. Cyclic voltammetry studies on the bimetallic complexes [M(κ1P-1)(cod)Cl] (M=Rh: 2; M=I
- Feyrer, Alexander,Armbruster, Markus K.,Fink, Karin,Breher, Frank
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supporting information
p. 7402 - 7408
(2017/06/06)
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- Stereoselective synthesis of vinylsilanes: Via copper-catalyzed silylation of alkenes with silanes
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An efficient and stereoselective synthesis of vinylsilanes via copper-catalyzed direct silylation of alkenes with silanes was developed. This study offers a new and expedient strategy for the synthesis of synthetically useful alkenyl organosilicon compoun
- Gu, Jian,Cai, Chun
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supporting information
p. 10779 - 10782
(2016/09/07)
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- Platinum catalyst on polysiloxane microspheres with N-chelating groups
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Elastic and durable, magnetic and non-magnetic polysiloxane microspheres containing a large number of SiOH groups were obtained by a simple and cheap emulsion process. N-chelating ligands were grafted on these microspheres by the condensation of their silanol groups with N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane. A platinum catalyst was immobilized on these microspheres. At every stage of the microspheres modification they were characterized by spectroscopy methods as well as by SEM microscopy. The catalyst appears only in the form of Pt(II) complex. The Pt(0) form was obtained by reducing this complex using sodium borohydride. The catalytic activity of the obtained catalysts was compared using model reactions, which were the hydrosilylation of phenylacetylene and hydrogenation of cinnamaldehyde. In both of these reactions the new platinum catalysts were recycled several times with the retention of their high catalytic activity. The hydrogenation of cinnamaldehyde leads to two products hydrocinnamaldehyde (HCA) and 3-phenyl-1-propanol (PP). The comparison of the rate of formation of the products with the rate of HCA and cinnamyl alcohol (CA) hydrogenation indicates that neither HCA nor CA are intermediate in the main pathway of the formation of PP.
- Pospiech, Piotr,Chojnowski, Julian,Mizerska, Urszula,Cempura, Grzegorz
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p. 402 - 411
(2016/09/28)
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- Hydrosilylation of Terminal Alkynes Catalyzed by a ONO-Pincer Iridium(III) Hydride Compound: Mechanistic Insights into the Hydrosilylation and Dehydrogenative Silylation Catalysis
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The catalytic activity in the hydrosilylation of terminal alkynes by the unsaturated hydrido iridium(III) compound [IrH(κ3-hqca)(coe)] (1), which contains the rigid asymmetrical dianionic ONO pincer ligand 8-oxidoquinoline-2-carboxylate, has been studied. A range of aliphatic and aromatic 1-alkynes has been efficiently reduced using various hydrosilanes. Hydrosilylation of the linear 1-alkynes hex-1-yne and oct-1-yne gives a good selectivity toward the β-(Z)-vinylsilane product, while for the bulkier t-Bu-C≡CH a reverse selectivity toward the β-(E)-vinylsilane and significant amounts of alkene, from a competitive dehydrogenative silylation, has been observed. Compound 1, unreactive toward silanes, reacts with a range of terminal alkynes RC≡CH, affording the unsaturated η1-alkenyl complexes [Ir(κ3-hqca)(E-CH=CHR)(coe)] in good yield. These species are able to coordinate monodentate neutral ligands such as PPh3 and pyridine, or CO in a reversible way, to yield octahedral derivatives. Further mechanistic aspects of the hydrosilylation process have been studied by DFT calculations. The catalytic cycle passes through Ir(III) species with an iridacyclopropene (η2-vinylsilane) complex as the key intermediate. It has been found that this species may lead both to the dehydrogenative silylation products, via a β-elimination process, and to a hydrosilylation cycle. The β-elimination path has a higher activation energy than hydrosilylation. On the other hand, the selectivity to the vinylsilane hydrosilylation products can be accounted for by the different activation energies involved in the attack of a silane molecule at two different faces of the iridacyclopropene ring to give η1-vinylsilane complexes with either an E or Z configuration. Finally, proton transfer from a η2-silane to a η1-vinylsilane ligand results in the formation of the corresponding β-(Z)- and β-(E)-vinylsilane isomers, respectively.
- Pérez-Torrente, Jesús J.,Nguyen, Duc Hanh,Jiménez, M. Victoria,Modrego, F. Javier,Puerta-Oteo, Raquel,Gómez-Bautista, Daniel,Iglesias, Manuel,Oro, Luis A.
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supporting information
p. 2410 - 2422
(2016/08/02)
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- Phosphine-stabilized, oxide-supported rhodium catalysts for highly efficient silylative coupling reactions
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Oxide-supported rhodium catalysts with excellent activity in silylative coupling reactions have been developed. Reductive pretreatment of the catalysts in the presence of 0.5 equiv triphenylphosphine under a hydrogen atmosphere enhanced and stabilized the
- Tsukada, Shinji,Wada, Kenji,Miura, Hiroki,Hosokawa, Saburo,Abe, Ryu,Inoue, Masashi
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p. 9575 - 9586
(2016/01/12)
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- Platinum(0) olefin complexes of a bulky terphenylphosphine ligand. Synthetic, structural and reactivity studies
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A novel terphenylphosphine PMe2ArDipp2 (1) (Dipp = 2,6-iPr2C6H3) forms stable Pt(0) complexes with ethene and 3,3-dimethylbut-1-ene that behave as sources of the reactive Pt(PMe
- Ortega-Moreno, Laura,Peloso, Riccardo,Maya, Celia,Suárez, Andrés,Carmona, Ernesto
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supporting information
p. 17008 - 17011
(2015/12/01)
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- N-Heterocyclic carbene rhodium(i) complexes containing an axis of chirality: Dynamics and catalysis
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The novel rhodium(i) complexes [RhCl(NBD)(NHC)] [NBD = norbornadiene, NHC = 1-benzyl-3-R-imidazolin-2-ylidene; R = Me (3a), Bz (3b), Tr (3c), tBu (3d)], containing on one nitrogen the benzyl substituent and on the other increasing bulky alkyl substituents were prepared. All the complexes display restricted rotation around the metal-carbene bond and yield conformational enantiomers. The stereodynamics and racemization barriers about the Rh-carbene have been determined by means of NMR spectroscopy for 3a-c, whereas for the bulkiest 3d only the lower limit (91 kJ mol-1) could be calculated. Whilst the racemization barriers obtained by DFT calculations for 3a,b and 3d matched the experimental values, in the case of 3c the latter (62.3 kJ mol-1) was much smaller with respect to the calculated one (101.7 kJ mol-1). The lower experimental barrier has been attributed to a dissociative pathway that produces a solvated ionic pair in the transition state. The catalytic activity of the neutral rhodium(i) complexes 3a and 3d in the hydrosilylation with HSiMe2Ph of the terminal alkynes PhC≡CH, TolC≡CH, nBuC≡CH, Et3SiC≡CH, and (CPh2OH)C≡CH has been investigated, and compared with the amide-functionalized [RhCl(NBD){1-(2-NHBoc-ethyl)-3-Me-imidazolin-2-ylidene}] (4) and with [RhCl(NBD){1-butyl-3-Me-imidazolin-2-ylidene}] (5).
- Cassani, Maria Cristina,Brucka, Marta Anna,Femoni, Cristina,Mancinelli, Michele,Mazzanti, Andrea,Mazzoni, Rita,Solinas, Gavino
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supporting information
p. 1768 - 1779
(2014/05/06)
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- Solid supported palladium(0) nanoparticles: An efficient heterogeneous catalyst for regioselective hydrosilylation of alkynes and suzuki coupling of β-arylvinyl iodides
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The solid supported palladium(0) nanoparticles (NPs) were found as an active heterogeneous catalyst for regioselective hydrosilylation of alkynes with organosilanes in the presence of NaI as additive. Aliphatic as well as aromatic terminal/substituted alkynes with both electron releasing and withdrawing functionalities similarly participated in the hydrosilylation to produce regioselective β-isomers of vinylsilanes under mild reaction conditions. Reducible functional groups such as nitrile, ester, halide, alkene and alkyne were also found to be tolerated under this condition. Furthermore, the triethylsilylstyrene was applied for consecutive iododesilylation followed by Suzuki coupling reaction to produce stilbenes. The air/moisture stable SS-Pd catalyst was recycled for hydrosilylation reaction up to ten runs without significant loss of its catalytic activity. Graphical Abstract: Solid Supported Palladium(0) Nanoparticles: An Efficient Heterogeneous Catalyst for Regioselective Hydrosilylation of Alkynes and Suzuki Coupling of β-Arylvinyl Iodides[Figure not available: see fulltext.]
- Bal Reddy, C.,Shil, Arun K.,Guha, Nitul Ranjan,Sharma, Dharminder,Das, Pralay
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p. 1530 - 1536,7
(2014/10/15)
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- Synthesis and characterization of a 1,3-phenylene-bridged N-alkyl bis(benzimidazole) CCC-NHC pincer ligand precursor: Homobimetallic silver and rhodium complexes and the catalytic hydrosilylation of phenylacetylene
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A new CCC-NHC pincer ligand precursor architecture based on 1,3-bis(N-alkylbenzimidazole)benzene has been synthesized and metalated using Ag2O, forming a homobimetallic Ag complex with a metal to ligand ratio of 1:1. The Ag complex was treated
- Huckaba, Aron J.,Hollis, T. Keith,Howell, Tyler O.,Valle, Henry U.,Wu, Yunshan
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- New organoplatinum (IV) complex with quaterpyridine ligand: Synthesis, structure and its catalytic activity in the hydrosilylation of styrene and terminal alkynes
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The reaction of ligand L with PtCl2 leads to a novel structural motif of octahedral ortho-metalated complex of formula [Pt(L-H) Cl3] 1. This result is a consequence of drastic conditions of reaction and preferred Pt(IV) octahedral coordination geometry. The new compound has been characterised on the basis of the spectroscopic data in solution, and its structure confirmed in the solid state by X-ray crystallography (1a - [Pt(L-H)Cl3]·MeOH, 1b - [Pt(L-H)Cl 3]·C6H5CH3). This article reports organoplatinum (IV) complex 1 as effective and highly selective catalyst precursor in the hydrosilylation of styrene and terminal alkynes.
- Adamski, Ariel,Kubicki, Maciej,Pawlu?, Piotr,Grabarkiewicz, Tomasz,Patroniak, Violetta
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- Exceptionally E- and β-selective NHC-Cu-catalyzed proto-silyl additions to terminal alkynes and site- and enantioselective proto-boryl additions to the resulting vinylsilanes: Synthesis of enantiomerically enriched vicinal and geminal borosilanes
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An exceptionally site- and E-selective catalytic method for preparation of Si-containing alkenes through protosilylation of terminal alkynes is presented. Furthermore, the vinylsilanes obtained are used as substrates to generate vicinal or geminal borosilanes by another catalytic process; such products are derived from enantioselective protoborations of the Si-substituted alkenes. All transformations are catalyzed by N-heterocyclic carbene (NHC) copper complexes. Specifically, a commercially available imidazolinium salt, cheap CuCl (1.0 mol %) and Me2PhSi-B(pin), readily and inexpensively prepared in one vessel, are used to convert terminal alkynes to (E)-β-vinylsilanes efficiently (79-98 % yield) and in >98 % E and >98 % β-selectivity. Vinylsilanes are converted to borosilanes with 5.0 mol % of a chiral NHC-Cu complex in 33-94 % yield and up to 98.5:1.5 enantiomeric ratio (e.r.). Alkyl-substituted substrates afford vicinal borosilanes exclusively; aryl- and heteroaryl-substituted alkenes deliver the geminal isomers preferentially. Different classes of chiral NHCs give rise to high enantioselectivities in the two sets of transformations: C1-symmetric monodentate Cu complexes are most suitable for reactions of alkyl-containing vinylsilanes and bidentate sulfonate-bridged variants furnish the highest e.r. for substrates with an aryl substituent. Working models that account for the observed trends in selectivity are provided. Utility is demonstrated through application towards a formal enantioselective total synthesis of naturally occurring antibacterial agent bruguierol A. Different NHCs for different tasks: Three classes of N-heterocyclic carbene(NHC)-Cu complexes serve to promote two sets of reactions. Catalysts with an achiral monodentate NHC convert terminal alkynes to (E)-β-vinylsilanes with exceptional selectivity through efficient protosilylation. Cu-based catalysts bearing a chiral monodentate NHC bring about protoborations of alkyl-substituted vinylsilanes, generating enantiomerically enriched vicinal borosilanes; however, it is the sulfonate-bridged bidentate NHC-Cu complexes that deliver geminal silylborons with the highest e.r. values. Copyright
- Meng, Fanke,Jang, Hwanjong,Hoveyda, Amir H.
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supporting information
p. 3204 - 3214
(2013/03/28)
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- An alternative mechanistic paradigm for the β-Z hydrosilylation of terminal alkynes: The role of acetone as a silane shuttle
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The β-Z selectivity in the hydrosilylation of terminal alkynes has been hitherto explained by introduction of isomerisation steps in classical mechanisms. DFT calculations and experimental observations on the system [M(I)2{κ-C,C,O,O-(bis-NHC)}]BF4 (M=Ir (3 a), Rh (3 b); bis-NHC=methylenebis(N-2-methoxyethyl)imidazole-2-ylidene) support a new mechanism, alternative to classical postulations, based on an outer-sphere model. Heterolytic splitting of the silane molecule by the metal centre and acetone (solvent) affords a metal hydride and the oxocarbenium ion [R 3Si - O(CH3)2]+, which reacts with the corresponding alkyne in solution to give the silylation product [R 3Si - CHi£C - R]+. Thus, acetone acts as a silane shuttle by transferring the silyl moiety from the silane to the alkyne. Finally, nucleophilic attack of the hydrido ligand over [R3Si - CHi£C - R]+ affords selectively the β-(Z)- vinylsilane. The β-Z selectivity is explained on the grounds of the steric interaction between the silyl moiety and the ligand system resulting from the geometry of the approach that leads to β-(E)-vinylsilanes. Silanes catch the shuttle: An outer-sphere mechanism that explains the β-Z hydrosilylation of terminal alkynes based on the role of acetone as a silane shuttle is disclosed. Heterolytic splitting of the silane molecule by the metal centre and acetone affords a metal hydride and the oxocarbenium ion [R 3Si - O(CH3)2]+, which reacts with the alkyne in solution to give the silylation product [R3Si - CHi£C - R]+ (see figure).
- Iglesias, Manuel,Sanz Miguel, Pablo J.,Polo, Victor,Fernandez-Alvarez, Francisco J.,Perez-Torrente, Jesus J.,Oro, Luis A.
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p. 17559 - 17566
(2014/01/06)
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- Selective hydrosilylation of alkynes with a nanoporous gold catalyst
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The hydrosilylation of acetylenic compounds proceeded smoothly in the presence of a reusable nanoporous gold catalyst under mild conditions and the β-(E)-cis-addition products were obtained in good to high yields regio- and stereoselectively.
- Ishikawa, Yoshifumi,Yamamoto, Yoshinori,Asao, Naoki
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p. 2902 - 2905
(2013/11/06)
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- Controlling the regioselectivity of the hydrosilylation reaction in carbon nanoreactors
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Hollow graphitized carbon nanofibres (GNF) are employed as nanoscale reaction vessels for the hydrosilylation of alkynes. The effects of confinement in GNF on the regioselectivity of addition to triple carbon-carbon bonds are explored. A systematic comparison of the catalytic activities of Rh and RhPt nanoparticles embedded in a nanoreactor with free-standing and surface-adsorbed nanoparticles reveals key mechanisms governing the regioselectivity. Directions of reactions inside GNF are largely controlled by the non-covalent interactions between reactant molecules and the nanofibre channel. The specific π-π interactions increase the local concentration of the aromatic reactant and thus promote the formation of the E isomer of the β-addition product. In contrast, the presence of aromatic groups on both reactants (silane and alkyne) reverses the effect of confinement and favours the formation of the Z isomer due to enhanced interactions between aromatic groups in the cis-orientation with the internal graphitic step-edges of GNF. The importance of π-π interactions is confirmed by studying transformations of aliphatic reactants that show no measurable changes in regioselectivity upon confinement in carbon nanoreactors. Nanoscale reaction vessels: Carbon nanoreactors are prepared by encapsulating catalytic Rh or RhPt nanoparticles in hollow graphitised nanofibres. Inside the nanoreactors, the pathways of the hydrosilylation reactions differ from those on the surface of nanofibres or in the bulk phase (see scheme). Copyright
- Solomonsz, William A.,Rance, Graham A.,Suyetin, Mikhail,La Torre, Alessandro,Bichoutskaia, Elena,Khlobystov, Andrei N.
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supporting information
p. 13180 - 13187
(2013/01/15)
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- Reaction of hydrosilanes with alkynes catalyzed by gold nanoparticles supported on TiO2
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Gold nanoparticles supported on TiO2 (0.8-1.4 mol %) catalyze the β-(E) regioselective hydrosilylation of a variety of functionalized terminal alkynes with alkylhydrosilanes in 1,2-dichloroethane (70 °C). The product yields are excellent, and the reaction times relatively short, while almost equimolar amounts of alkynes and hydrosilanes can be used. Minor side-products in up to 35% relative yield of cis-oxidative (dehydrogenative) disilylation, an unprecedented reaction pathway, are formed in the cases of the less hindered hydrosilanes and alkynes. Triethoxysilane reacts faster and affords apart from β-(E) addition products, minor α-hydrosilylation regio-isomers in upto 15% relative yield. Internal alkynes are generally less reactive or even unreactive. It is proposed that cationic Au(I) species stabilized by the support are the reactive catalytic sites, forming in the presence of hydrosilanes either silyl-Au(III)-H (hydrosilylation pathway) or Au(III)-disilyl species (dehydrogenative disilylation pathway). Regarding the mechanism of hydrosilylation, kinetic experiments are in agreement with silyl carbometallation of the triple bond in the rate determining step of the reaction.
- Psyllaki, Androniki,Lykakis, Ioannis N.,Stratakis, Manolis
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p. 8724 - 8731
(2012/11/13)
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- A synthon for a 14-electron Ir(iii) species: Catalyst for highly selective β-(Z) hydrosilylation of terminal alkynes
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A synthon for a 14-electron Ir(iii) species is described. The geometrical control exerted by the ligand system over the Ir-alkenyl intermediate in hydrosilylation of terminal alkynes precludes formation of the more thermodynamically stable β-(E)-vinylsila
- Iglesias, Manuel,Perez-Nicolas, Maria,Miguel, Pablo J. Sanz,Polo, Victor,Fernandez-Alvarez, Francisco J.,Perez-Torrente, Jesus J.,Oro, Luis A.
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supporting information
p. 9480 - 9482
(2012/10/29)
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- A simple route to chelating, structurally different triazole-based bis(N-heterocyclic carbene) ligands and their coordination to PtII
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Two new bis(triazolium) salts have been prepared and used as N-heterocyclic carbene (NHC) precursors. The structure of the salts is highly dependent on the synthetic route, which implies the sequential alkylation of two of the three N atoms at the triazol
- Zanardi, Alessandro,Mata, Jose A.,Peris, Eduardo
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scheme or table
p. 416 - 421
(2011/05/07)
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- N-heterocyclic carbene-amide rhodium(I) complexes: Structures, dynamics, and catalysis
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The amide-functionalized imidazolium salts [BocNHCH2CH 2ImR]X (R = Me, X = I, 1a; R = benzyl, X = Br, 1b; R = trityl, X = Cl, 1c) bearing increasingly bulky N-alkyl substituents were prepared in high yields by direct alkylation of the (2-imidazol-1-yl-ethyl)carbamic acid tert-butyl ester; 1c is a crystalline solid also characterized by X-ray diffraction. These salts are precursors for the synthesis of rhodium(I) complexes [Rh(NBD)X(NHC)] (NHC = 1-(2-NHBoc-ethyl)-3-R-imidazolin-2-ylidene; X = Cl, R = Me (3a), R = benzyl (3b), R = trityl (3c); X = I, R = Me (4a)). All the complexes display restricted rotation about the metal-carbene bond; however, while the rotation barriers calculated for 3a,b and 4a matched the experimental values, unexpectedly this was not true in the case of 3c, where the experimental value was equal to that obtained for compound 3b (58.6 kJ mol-1) and much smaller with respect to the calculated one (100.0 kJ mol-1). The catalytic activity of the neutral rhodium(I) complexes 3a-c in the hydrosilylation of terminal alkynes with HSiMe2Ph has been investigated with PhC≡CH, TolC≡CH, nBuC≡CH, Et 3SiC≡CH, and (CPh2OH)C≡CH as substrates. The steric hindrance on the N-heterocyclic ligand and on the alkyne substrates affects conversion and selectivity: for the former the best results were achieved employing the less encumbered 3a catalyst with TolC≡CH, whereas by employing hindered alkynes such as Et3SiC≡CH or (CPh 2OH)C≡CH the hydrosilylation leads only to the formation of the β-(E)-vinylsilane and α-bis(silyl)alkene isomers. The complexes 3a,b have also been employed in the addition of arylaldehydes with phenylboronic acid, and like in the hydrosylylation case, the best results were obtained using 3a in the presence of aldehydes bearing electron-withdrawing groups, such as 4-cyanobenzaldehyde and 4-acetylbenzaldehyde as substrates.
- Busetto, Luigi,Cassani, M. Cristina,Femoni, Cristina,Mancinelli, Michele,Mazzanti, Andrea,Mazzoni, Rita,Solinas, Gavino
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experimental part
p. 5258 - 5272
(2011/12/02)
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- Copper-catalyzed highly regioselective silylcupration of terminal alkynes to form α-vinylsilanes
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A highly regioselective synthesis of branched vinylsilanes through silicon-copper additions to terminal alkynes catalyzed by copper(I) was developed using methanol as additive. The corresponding vinylsilanes were obtained with excellent branched to linear selectivity of up to 99/1 in good yields.
- Wang, Peng,Yeo, Xue-Liang,Loh, Teck-Peng
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supporting information; experimental part
p. 1254 - 1256
(2011/04/16)
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- Some synthetic applications of vinylphosphane oxides
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Vinylphosphane oxides have been used as Michael acceptors for the diastereoselective synthesis of anti α-functionalized-β-silylated phosphane oxides and β-stannyl-, β-phenylthio- or β-phosphanyl phosphane oxides. Although the utility of these substrates as dipolarophiles was more limited, we have obtained a mixture of 3- and 4-phosphanylpyrazoles in which the latter is the major regioisomer, by 1,3-cycloaddition with N-phenylsydnone. Moreover, vinylphosphane oxides reacted with aldehydes in the presence of LDA by a Baylis-Hillman type reaction, leading to (E)-β-hydroxyphosphane oxides, which were readily converted in allenes. It is noteworthy that the application of this methodology to silylated substrates has permitted us to synthesize an interesting and more versatile silylallene.
- Gonzalez-Nogal, Ana M.,Cuadrado, Purificacion,Sarmentero, Maria A.
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experimental part
p. 9610 - 9619
(2011/01/03)
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- Sequential hiyaima coupling/narasaka acylation reaction of (e)-1,2-disilylethene: rapid assembly of α,β-unsaturated carbonyl motifs
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The synthesis and application of (E)-1,2-disilylethene 5 as a central functional building block in a sequential Hiyama coupling/Narasaka acylation reaction are described, Its use in the rapid and versatile construction of α,β-unsaturated carbonyl motifs found in a number of polyunsaturated natural products has been demonstrated. It was observed that due to the differential intrinsic reactivity of the two carbon-silicon bonds, this bis-metallated lynchpin-type reagent is activated selectively and sequentially by Pd and Rh catalysis, negating the need for any protecting group, A number of (E)-α,β-unsaturated ketones were efficiently synthesized with complete chemoselectively in the presence of a variety of halides and anhydride acids. Conjugated polyunsaturated ketones and diversely α'-functionalized α,β-enones, such, as chalcones, a heterocyclic dienone and the highly conjugated ethyl (2Z,4E)-6-oxo-6-(2-thienyl)hexa-2,4-dienoate, were obtained in good overall yields. Thus, this coupling sequence provides a high degree of modularity, that is, a single template is likely to produce a large number of synthetic targets.
- Thiot, Carine,Mioskowski, Charles,Wagner, Alain
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experimental part
p. 3219 - 3227
(2009/12/09)
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- Pincer complex-catalyzed redox coupling of alkenes with lodonium salts via presumed palladium(IV) itermediates
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Palladium pincer complexes directly catalyze the redox coupling reactions of functionalized alkenes and iodonium salts. The catalytic process, which Is suitable for mild catalytic functionalization of allylic acetates and electron-rich alkenes, probably o
- Aydin, Juhanes,Larsson, Johanna M.,Selander, Nicklas,Szabo, Kalman J.
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supporting information; experimental part
p. 2852 - 2854
(2009/12/05)
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- Xphos ligand and platinum catalysts: A versatile catalyst for the synthesis of functionalized β-(E)-vinylsilanes from terminal alkynes
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Hydrosilylation of functionalized terminal arylalkynes with a variety of silanes catalyzed by PtCl2 or PtO2 in the presence of the air-stable and bulky Xphos ligand was investigated. Regardless of the electronic nature (electron withdrawing or donating group) and the position (o, m, p) of the substituents on the aromatic ring, a single β-(E)-styrylsilanes was obtained in good to excellent yields. The regioselectivity of the H-Si bond addition was found to be governed by steric effects induced by the bulky Xphos ligand. A dramatic regioselectivity was also observed when functionalized terminal aliphatic alkynes were employed as a substrate and in these cases regioisomeric β-(E)-vinylsilanes were generated with excellent selectivity.
- Hamze, Abdallah,Provot, Olivier,Brion, Jean-Daniel,Alami, Mouad
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p. 2789 - 2797
(2008/12/20)
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