- REVERSIBILITY IN THE HOMOLYTIC AROMATIC SUBSTITUTION WITH SILYL AND GERMYL RADICALS
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The 3,6-bis(trimethylsilyl)cyclohexadienyl radical (1), generated from the corresponding cyclohexadiene, gave the expected p-bis(tri-methylsilyl)benzene (4) at 0 deg.C.At 130 deg.C, however, the reaction afforded trimethylsilylbenzene, 4, and m-bis(trimethylsilyl)benzene in 62, 17, and 5percent yield, respectively.The suggested elimination of the trimethylsilyl radical from the cyclohexadienyl radical is demonstrated by ESR.
- Sakurai, Hideki,Kira, Mitsuo,Sugiyama, Hisashi
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- Diphenylphosphinophenolate: A ligand for the palladium-catalysed silylation of aryl halides activating simultaneously both palladium and silicon
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Diphenylphosphinophenolate was found to be an effective ligand for the palladium-catalysed silylation of aryl halides, activating not only palladium but also silicon of a disilane, where aryl bromides and iodides having such substituents as methyl, methoxy, amino, ethoxycarbonyl, trifluoromethyl, formyl or phenyl are applicable to the reaction with hexamethyldisilane to give the corresponding trimethylsilylarenes.
- Shirakawa,Kurahashi,Yoshida,Hiyama
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Read Online
- Preparation method of aromatic silicon organic compound
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The invention provides a preparation method of an aromatic silicon organic compound. The aromatic silicon organic compound is a compound as shown in a formula 3 shown in the specification, the aromatic silicon organic compound is prepared by reacting a compound as shown in a formula 1 with a compound as shown in a formula 2, and the reaction formula is as shown in the specification. In the formulas, a is selected from any integer of 0-5, n is selected from any integer of 1-6, R is selected from one of alkyl, alkoxy, fluorine, trifluoromethyl and trifluoromethoxy; m is any integer selected from 1-3, and R2 is selected from C1-C6 alkyl; a catalyst used in the reaction is MIc, MIc is iodized salt, M is metal ion, and c is selected from 1 or 2 according to the valence state of M; and magnesium is added in the reaction process. The method has the advantages of low cost, effective avoidance of heavy metal residues, simplicity and convenience in operation, high yield, mild reaction conditions and easiness in industrialization.
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Paragraph 0084-0087
(2021/07/08)
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- Building responsive materials by assembling {Fe4Co4} switchable molecular cubes
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Responsive materials that can answer to chemical or physical external stimuli offer numerous prospects in material science. Here, we have elaborated a two-step synthetic approach that allows incorporating molecular cubic switches into a polymeric material
- Benchohra, Amina,Boillot, Marie-Laure,Borkiewicz, Olaf J.,Catala, Laure,Chamoreau, Lise-Marie,Dambournet, Damien,Flambard, Alexandrine,Glatz, Jana,Jiménez, Juan-Ramón,Lescou?zec, Rodrigue,Li, Yanling,Lisnard, Laurent,Plamont, Rémi,Tissot, Antoine,Xuan, Qui Pham
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supporting information
p. 8882 - 8890
(2021/07/28)
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- Hydrocarbon-Soluble Bis(trimethylsilylmethyl)calcium and Calcium-Iodine Exchange Reactions at sp2-Hybrized Carbon Atoms
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Hydrocarbon-soluble and highly reactive [(L)xCa(CH2SiMe3)2] (L = tetrahydropyran, x = 4 (2a); L = tmeda, x = 2 (2b)) is synthesized by the metathesis reaction of Me3SiCH2CaI (1-I) with KCH2SiMe3. The durability of 2a in tetrahydropyran solution at 0 °C is sufficiently high for subsequent chemical transformations. The reaction of ICH2SiMe3 with calcium in diethyl ether yields unique cage compound [(Et2O)2Ca(I)2·(Et2O)2Ca(I)(OEt)·(Et2O)Ca(I)(CH2SiMe3)] (3). We demonstrate that alkylcalcium complexes are valuable reagents for calcium-iodine exchange reactions at Csp2-I functionalities.
- Koch, Alexander,Wirgenings, Marino,Krieck, Sven,G?rls, Helmar,Pohnert, Georg,Westerhausen, Matthias
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p. 3981 - 3986
(2017/10/31)
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- Rhodium-catalyzed silylation and intramolecular arylation of nitriles via the silicon-assisted cleavage of carbon-cyano bonds
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A rhodium-catalyzed silylation reaction of carbon - cyano bonds using disilane has been developed. Under these catalytic conditions, carbon-cyano bonds in aryl, alkenyl, allyl, and benzyl cyanides bearing a variety of functional groups can be silylated. The observation of an enamine side product in the silylation of benzyl cyanides and related stoichiometric studies indicate that the carbon-cyano bond cleavage proceeds through the deinsertion of silyl isocyanide from η2-iminoacyl complex B. Knowledge gained from these studies has led to the development of a new intramolecular biaryl coupling reaction in which aryl cyanides and aryl chlorides are cross-coupled.
- Tobisu, Mamoru,Kita, Yusuke,Ano, Yusuke,Chatani, Naoto
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supporting information; experimental part
p. 15982 - 15989
(2009/05/16)
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- Reactions of trimethylstannide and trimethylsiliconide anions with aromatic and heteroarornatic substrates
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A parallel study was carried out on the reactions of Me3Sn- and Me3Si- ions towards aromatic and heteroaromatic substrates in hexamethylphosphoramide (HMPA) as solvent. It was found that Me3Si- ions are more reactive and therefore less selective than Me3Sn- ions. In HMPA, PhI and PhBr react with Me3Sn- ions through an HME pathway. PhCl also reacts by an HME reaction, but under photostimulation the SRN1 mechanism competes with the HME process, With PhF as sabstrate, Me3Sn- ions afford (4-fluorophenyl)trimethylstannane, presumably through a hypervalent tin species. Under irradiation, the SRN1 mechanism operates concurrently with the formation of the hypervalent tin species. Me3Si- ions, on the other hand, react with PhX (X = Cl, Br, I) to yield the ipso substitution product, presumably through the intermediacy of a hypervalent silicon species. PhF affords, upon reaction with Me3Si- ions, o- and p-fluorotrimethylsilylbenzenes together with the ipso substitution product PhSiMe3. A novel type of nucleophilic substitution mechanism takes place with Me3Si- ions upon reaction with aromatic and heteroaromatic substrates without classical leaving groups in HMPA. Copyright
- Postigo, Al,Vaillard, Santiago E.,Rossi, Roberto A.
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p. 889 - 893
(2007/10/03)
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- Synthesis of low-generation, aryl-/alkyl-type, nonpolar dendrons carrying protected hydroxyalkyl groups in the periphery
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An efficient convergent synthesis of first- and second-generation aryl-/alkyl-type nonpolar dendrons via Suzuki cross-coupling is described. The dendrons carry either one or two benzyl-protected hydroxyalkyl groups/terminus. Iododesilylation reactions of aryltrimethylsilanes with iodo chloride are used as a tool for the incorporation of iodo, an important functionality for transition-metal-catalyzed cross-coupling reactions. In the case of sensitive aromatics, the addition of some donor solvent like diethyl ether proved effective in suppressing side reactions through electrophilic aromatic iodination.
- Bo, Zhishan,Schlueter, A. Dieter
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p. 5327 - 5332
(2007/10/03)
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- A novel type of nucleophilic substitution reactions on nonactivated aromatic compounds and benzene itself with trimethylsiliconide anions.
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[reaction: see text]. The reaction of fluorobenzene with Me3Si- anion (1) in HMPA at room temperature surprisingly affords o- and p-fluorotrimethylsilylbenzenes (substitution of aromatic H for TMS, 76% yield) 7a and 7b and also 14% of trimethylsilylbenzene (2). Benzene itself reacts at 50 degrees C to furnish 4 in 45% yield. Pyridine affords p-trimethylsilylpyridine quantitatively. Mechanistic studies are presented.
- Postigo,Rossi
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p. 1197 - 1200
(2007/10/03)
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- Novel organoborane Lewis acids via selective boron-tin exchange processes - Steric constraints to electrophilic initiation by the boron halide
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With the purpose of preparing novel mono- and bidentate organoboron Lewis acids, the scope and limitations of synthesizing the requisite organoboranes by the boron-tin exchange between a boron halide and the appropriate organostannane have been examined in detail. The following organotin derivatives have been obtained either from the corresponding RMgBr or RLi reagent and MenSnCl4-n or from a Barbier procedure using the organic halide, Me3SnCl and magnesium metal: 1,2-bis(trimethylstannyl)ethyne, o-, m-, and p-bis(trimethylstannyl)benzenes, α,o-bis(trimethylstannyl)toluene, α,α-bis(trimethylstannyl)-o-xylene, and 2,2-dimethyl-2-stannaindane. The individual interaction of the 1,2-bis(trimethylstannyl)ethyne and the isomeric bis(trimethylstannyl)benzenes with Et2BBr produced the corresponding bis(diethylboryl)-derivatives. By contrast, with Et2BCl the α,o-bis(trimethylstannyl)toluene gave only o-diethylboryl-α-trimethylstannyltoluene and with BCl3 the α,α′-bis(trimethylstannyl)-o-xylene formed only α,α′-bis-(chlorodimethylstannyl)-o-xylene. Furthermore, in the attempted double boron-tin exchange between o-bis(trimethylstannyl)benzene and BCl3, an unprecedented rearrangement of the 1-(dichloroboryl)-2-(trimethylstannyl)benzene intermediate into its 1-[chloro(methyl)boryl]-2-(chlorodimethylstannyl) isomer was observed. Likewise, o-bis(trimethylstannyl)benzene with PhBCl2 produced by a similar rearrangement 1-[methyl(phenyl)boryl]-2-(chloro-dimethylstannyl)benzene. The thermolysis of such boranes led variously to definite dimers or ill-defined oligomers. Preliminary studies of the properties of these organoboranes have identified the heightened Lewis acidity of 1,2-bis(diethylboryl)ethyne and the π-electron delocalization involving the 2pΖ-boron orbitals in the 9,10-dihydro-9,10-diboraanthracene system. Finally, an electronic mechanism for the boron-tin exchange has been developed to account for the selectivity of the boron halide's attack at unsaturated carbon-tin bonds.
- Eisch, John J.,Kotowicz, Boguslaw W.
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p. 761 - 769
(2007/10/03)
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- SELECTIVE MONO- OR DIMETALATION OF ARENES BY MEANS OF SUPERBASIC REAGENTS
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If employed in tetrahydrofuran, stoichiometric amounts of butyllithium and potassium tert-butoxide react with benzene under clean monometalation.In hexane suspension, however, considerable amounts of meta- and para-disubstituted by-products are obtained (approx. 10percent).They become preponderant if a three-fold excess of the metalating agent is used.Naphthalene leads under the same conditions to a mixture of two mono- and ten di-substituted derivatives. - Alkyl groups, as present in tert-butylbenzene, retard the metalation at both m- and p-positions, while trialkylsilyl groups deactivate only m-position.In either case exclusive monosubstitution occurs. - Perdeuterobenzene undergoes metalation and subsequent electrophilic mono- or disubstitution to afford isotope labeled compounds with moderate, though synthetically attractive yields.The kinetic isotope effects and product ratios can be taken as evidence for aggregate formation at the level of both the superbasic metalating reagent and the organometallic intermediates.
- Schlosser, Manfred,Choi, Jung Hoon,Takagishi, Sadahito
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p. 5633 - 5648
(2007/10/02)
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- Electron Rich Olefins, 2. Structure and Electron Transfer Reactivity of the Cyclically ?/?-Hyperconjugated Carbosilane 3,3,6,6-Tetrakis(trimethylsilyl)-1,4-cyclohexadiene
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Crystal and molecular structure analysis of the title compound 1, a most electron rich carbosilane, exhibits a shallow boat conformation for the cyclohexadiene ring which is shielded by four bulky Me3Si groups.Multiple hyperconjugative interaction occures between the two non-conjugated olefinic ? systems and the four rather long (192 pm) carbon-silicon ? bonds which form an angle of about 34 deg with the assumed ? axis.The HOMO destabilization caused by this unique structural arrangement explains the energetically facile formation and subsequent reactivity of the cation radical 1(+) which was found to undergo oxidative desilylation to the aromatic 1,4-bis(trimethylsilyl)benzene precursor in the single electron transfer reaction with TCNE. - Keywords: Organosilicon Compounds, Molecular Conformation, Electron Transfer, Hyperconjugation, Electronic Structure
- Hausen, Hans-Dieter,Bessenbacher, Christian,Kaim, Wolfgang
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p. 1087 - 1093
(2007/10/02)
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- ELECTRON SPIN RESONANCE AND CHEMICAL STUDIES ON THE 6-(TRIMETHYLSILYL)CYCLOHEXADIENYL AND RELATED RADICALS.
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Various 3,6-disubstituted cyclohexadienyl radicals were generated and investigated by ESR at low temperature. Analysis of the ESR parameters indicated that the significant out-of-plane deformation of the carbon framework of 6-Me//3Si- and 6-Me//3Ge-substituted cyclohexadienyl radicals occurred to gain stabilization due to the effective hyperconjugation between the substituted methylene pseudo- pi orbital and the pi SOMO, while the 6-unsubstituted and 6-t-Bu cyclohexadienyl radicals were essentially planar. Investigation of the fate of the 3,6-bis(trimethylsilyl)cyclohexadienyl radical showed strong evidence for the temperature-dependent reversibility of the silyl radical addition to aromatics. The spontaneous elimination of the trimethylsilyl radical was proved by spin-trapping experiments.
- Kira,Sugiyama,Sakurai
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p. 6436 - 6442
(2007/10/02)
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- PREPARATION OF SILICA-SUPPORTED DIARYL KETONES FOR USE AS PHOTOSENSITIZERS: A NOVEL SYNTHETIC APPLICATION OF SILICA-SUPPORTED PHENYLLITHIUM
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Reaction of silica-supported phenyllithium, GSiC6H4Li (G=silica support) with p-(CH3)2NC6H4CO2CH3 gives a silica-supported diaryl ketone of the type GSiC6H4COC6H4N(CH3)2 which is an active sensitiezer for the photoisomerization of norbornadiene to q
- Hautala, R. R.,King, R. B.,Sweet, E. M.,Little, J. L.,Shields, Audrey W.
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p. 281 - 286
(2007/10/02)
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- Substituent Effects and Perturbation of ?-Systems, XXXVI. Me3C-, Me3Si-, Me3Ge-, Me3Sn-, and Me3Pb-Substituted Benzene and Naphthalene Derivatives and Their Radical Anions
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The effects of substituents -X(CH3)3 (X=C, Si, Ge, Sn, Pb) in 1,4-disubstituted benzenes and naphthalenes are investigated: PE spectra and CT excitation energies yield the energy differences between the ground state of the neutral molecule M and the vario
- Kaim, Wolfgang,Tesmann, Holger,Bock, Hans
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p. 3221 - 3234
(2007/10/02)
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