- Addition and cyclization reactions in the thermal conversion of hydrocarbons with an enyne structure, 5: High-temperature ring closures of 1,3-hexadien-5-ynes to naphthalenes - Competing reactions via isoaromatics, alkenylidene carbenes, and vinyl-type radicals
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The 4-substituted 1-phenyl-1-butene-3-ynes 1a-c and the 2-ethynylstyrenes 7a-c were subjected to high-temperature pyrolysis. The cycloisomerization products isolated suggest that these are formed by three competing processes: by (i) an electrocyclic or a molecule-induced, (ii) an alkenylidene carbene controlled, and (iii) a radical-controlled ring-closure . To estimate the relative importance of these three reactions here mentioned, the substrates have been isomerized in oxygen-free nitrogen and in nitrogen proportionally substituted by toluene at 700 and 650°C, respectively. The relative contributions of these isomerizations depend not only on the conversion temperature but also on the substituent R in 1 or 7. Wiley-VCH Verlag GmbH, 1997.
- Hofmann, Joerg,Schulz, Kathrin,Altmann, Annett,Findeisen, Matthias,Zimmermann, Gerhard
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- Time-resolved fluorescence of α,ω-di(1-naphthyl)oligosilanes and 1-naphthyloligosilanes: Intramolecular excimer formation and charge-transfer interactions
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The intramolecular photochemical processes excimer formation and charge-transfer (CT) complex formation were investigated by comparing the behavior of α,ω-di(1-naphthyl)permethyloligosilanes ((1-naphthyl)-(SiMe2) n -(1-naphthyl); NS n N, n = 1, 3, and 6) and 1-(1-naphthyl)permethyloligosilanes ((1-naphthyl)-(SiMe2) n -Me; NS n, n = 1, 3, and 6) by use of stationary and time-resolved fluorescence (TR-FL) measurements. Formation of excimer and CT complexes is highly dependent on the silicon chain length and polarity of the medium. Graphical Abstract: Intramolecular excimer formation between the two naphthyl groups and charge transfer interactions between the naphthyl and silane moieties were investigated by use of a time-correlated single-photon counting method.[Figure not available: see fulltext.]
- Karatsu, Takashi,Nakamura, Takashi,Terasawa, Masato,Yagai, Shiki,Kitamura, Akihide,Nishimura, Yoshinobu,Yamazaki, Iwao
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- Protodesilylation of Arylsilanes by Visible-Light Photocatalysis
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The first visible-light-mediated photocatalytic, metal- and base-free protodesilylation of arylsilanes is presented. The C(sp2)-Si bond cleavage process is catalyzed by a 5 mol % loading of a commercially available acridinium salt upon blue-light irradiation. Two simple approaches have been identified employing either aerobic or hydrogen atom transfer cocatalytic conditions, which enable the efficient and selective desilylation of a broad variety of simple and complex arylsilanes under mild conditions.
- García Manche?o, Olga,Kuhlmann, Jan H.,Uygur, Mustafa
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supporting information
p. 1689 - 1694
(2022/03/14)
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- Generation of Aryllithium Reagents from N -Arylpyrroles Using Lithium
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Treatment of 1-aryl-2,5-diphenylpyrroles with lithium powder in tetrahydrofuran at 0 °C results in the generation of the corresponding aryllithium reagents through reductive C-N bond cleavage.
- Ozaki, Tomoya,Kaga, Atsushi,Saito, Hayate,Yorimitsu, Hideki
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p. 3019 - 3028
(2021/06/02)
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- Cobalt-Catalyzed Defluorosilylation of Aryl Fluorides via Grignard Reagent Formation
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Transition-metal-catalyzed transformations of the carbon-fluorine bond not only tackle an interesting problem of challenging bond activation but also offer new synthetic strategies where the relatively inert C-F bond is converted to versatile functional groups. Herein we report a practical cobalt-catalyzed silylation of aryl fluorides that uses a cheap electrophilic silicon source with magnesium. This method is compatible with various silicon sources and can be operated under aerobic conditions. Mechanistic studies support the in situ formation of a Grignard reagent, which is captured by the electrophilic silicon source.
- Cho, Hyungdo,Cho, Seung Hwan,Jang, Minjae,Jeong, Jongheon,Kim, Hyunseok,Lee, Eunsung,Lim, Soobin
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supporting information
p. 7387 - 7392
(2020/10/12)
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- Nickel-Catalyzed Decarbonylation of Acylsilanes
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Nickel-catalyzed decarbonylation of acylsilanes is developed. In sharp contrast to cross-coupling reactions of acylsilanes, in which the silyl group serves as a leaving group, the silyl group is retained in the product in this decarbonylation reaction. Although the strong binding of the dissociated CO to the nickel center frequently hinders catalyst turnover in nickel-mediated decarbonylative reactions, this reaction can be catalyzed by nickel complexes bearing a CO ligand.
- Ito, Yuri,Kodama, Takuya,Nakatani, Syun,Sakurai, Shun,Tobisu, Mamoru
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p. 7588 - 7594
(2020/06/27)
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- Nickel-catalyzed cross-coupling reaction of carbamates with silylmagnesium reagents
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The C–O bonds are kinetically inert in cross-coupling reactions compared to those of carbon–halogen bonds. Thus, developing methodologies for the activation of C–O bonds in cross-coupling reactions remains a major challenge. We disclose an unprecedented nickel mediated cross-coupling of carbamates with silylmagnesium reagents that does not require the expensive silylboranes. Silylmagnesium reagents were prepared from either silyllithium or silyl iodides. This methodology is distinguished by the synthesis of trimethylsilyl coupled product and its synthetic applications. Kinetic studies and radical clock experiments revealed the rate-limiting C–O bond cleavage, half order with respect to the catalyst and a non-radical transition state.
- Murugesan, Vetrivelan,Balakrishnan, Venkadesh,Rasappan, Ramesh
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p. 293 - 298
(2019/08/12)
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- Absorption and fluorescence spectroscopic properties of 1- and 1,4-silyl-substituted naphthalene derivatives
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Silyl-substituted naphthalene derivatives at the 1- and 1,4-positions were synthesized and their UV absorption, fluorescence spectroscopic properties, and fluorescence lifetimes were determined. Analysis of the results shows that the introduction of silyl groups at these positions of the naphthalene chromophore/fluorophore causes shifts of the absorption maxima to longer wavelengths and increases in fluorescence intensities. Bathochromic shifts of the absorption maxima and increases in fluorescence intensities are also promoted by the introduction of methoxy and cyano groups at the naphthalene 4- and 5-positions. In addition, the fluorescence of 9,10-dicyanoanthracene is efficiently quenched by these naphthalene derivatives with Stern-Volmer plot calculated rate constants that depend on the steric bulk of the silyl groups.
- Maeda, Hajime,Maeda, Tomohiro,Mizuno, Kazuhiko
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p. 5108 - 5125
(2012/08/28)
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- Gold-catalysed oxyarylation of styrenes and mono- and gem-disubstituted olefins facilitated by an iodine(III) oxidant
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1-Hydroxy-1,2-benziodoxol-3(1H)-one (IBA) is an efficient terminal oxidant for gold-catalysed, three-component oxyarylation reactions. The use of this iodine(III) reagent expands the scope of oxyarylation to include styrenes and gem-disubstituted olefins, substrates that are incompatible with the previously reported Selectfluor-based methodology. Diverse arylsilane coupling partners can be employed, and in benzotrifluoride, homocoupling is substantially reduced. In addition, the IBA-derived co-products can be recovered and recycled. The I's have it: The unprecedented use of an iodine(III) reagent as the terminal oxidant for gold-catalysed oxyarylation allows the substrate scope to be significantly expanded; in addition to monosubstituted olefins, styrenes and gem-disubstituted olefins are well tolerated (see scheme). With benzotrifluoride as solvent, unproductive homodimerisation of the arylsilane coupling partner is effectively suppressed. Copyright
- Ball, Liam T.,Lloyd-Jones, Guy C.,Russell, Christopher A.
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supporting information; experimental part
p. 2931 - 2937
(2012/04/23)
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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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- Rh(I)-catalyzed silylation of aryl and alkenyl cyanides involving the cleavage of C-C and Si-Si bonds
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The Rh(I)-catalyzed silylation of nitriles with disilanes is described. The cleavage of inert carbon-cyano and silicon-silicon bonds occurs in this catalysis. Copyright
- Tobisu, Mamoru,Kita, Yusuke,Chatani, Naoto
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p. 8152 - 8153
(2007/10/03)
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- Experimental determination of the α and β C-H bond dissociation energies in naphthalene
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The acidities of the two different sites in naphthalene (1α and 1β) and the electron affinities of the α- and β-naphthyl radicals were measured using a Fourier transform mass spectrometer. Both carbon-hydrogen bond dissociation energies for naphthalene also were obtained, in this case via the application of a thermodynamic cycle. The final results are ΔH(acid)(o) (1α) = 394.2 ± 1.2 kcal mol-1, ΔH(acid)(o) (1β) = 395.5 ± 1.3 kcal mol-1, EA(α) = 31.6 ± 0.5 kcal mol-1, EA(β) = 31.6 ± 0.5 kcal mol-1, BDE(1α) = 112.2 ± 1.3 kcal mol-1 and BDE(1α) = 111.9 ± 1.4 kcal mol-1, and they are compared to benzene and phenyl radical as well as ab initio and density functional theory (B3LYP) calculations. Copyright (C) 2000 John Wiley and Sons, Ltd.
- Reed, Dana R.,Kass, Steven R.
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p. 534 - 539
(2007/10/03)
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- Aryl fluoride syntheses involving reactions of aryllead triacetates with boron trifluoride-diethyl ether complex
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Aryllead(IV) triacetates react at room temperature with BF3.Et2O to give the corresponding aryl fluoride in moderate to good yields; triarylboroxines, electron rich aryltrimethylsilanes and some arenes, which yield aryllead triacetates in acid catalysed reactions with lead tetraacetate, are converted directly into aryl fluorides when stirred with lead tetraacetate in BF3.Et2O. An investigation of the mechanism of the fluoro-deplumbation reaction indicates that it probably proceeds by acid catalysed heterolytic cleavage of the C-Pb bond to produce an aryl cation.
- De Meio,Morgan,Pinhey
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p. 8129 - 8138
(2007/10/02)
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- SILICON-MODIFIED BIRCH REDUCTION AND REDUCTIVE ALKYLATION OF POLYNUCLEAR AROMATICS
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A trimethylsilyl substituent is used to control regiochemistry, overreduction, and prevent bond cleavage during the metal/ammonia reduction of aromatic and polynuclear aromatic compounds.The trimethylsilyl group is then removed by tetrabutylammonium fluoride and replaced by either hydrogen or primary alkyl, the latter case representing overall reductive alkylation.Results are presented for naphtalene together with its 1-methyl, 2-methyl and 2-methoxy derivatives, phenanthrene and its 9-methyl and 9-ethyl derivatives, biphenyl and triptycene.
- Marcinow, Z.,Clawson, D. K.,Rabideau, P. W.
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p. 5441 - 5448
(2007/10/02)
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- Palladium-mediated silylation of organic halides with disilane/F- reagent
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Under catalytic influence of tetrakis(triphenylphosphine)palladium, tris(diethylamino)sulfonium trimethyldiflourosilicate promoted the reaction of vynil halides with hexamethyldisilane to give corresponding vinyl silanes in good yields chemoselectivity and stereospecifically.
- Hatanaka, Yasou,Hiyama, Tamajiro
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p. 4715 - 4718
(2007/10/02)
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- Electrochemical Synthesis of Organosilicon Compounds
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Electrochemical reduction of allyl, aryl, and vinyl halides in the presence of a silylating agent (Me3SiCl, HMe2SiCl, and PhMe2SiCl) in a solution of tetraethylammonium tosylate in dimethylformamide (DMF) gave the corresponding organosilicon compounds.The regioselectivity of the reaction of allylic halides depends on the nature of the silylating agent.Trimethylsilyl and dimethylphenylsilyl groups were introduced to the less substituted end of the allyl group, whereas the dimethylsilyl group was introduced to both ends of the allyl group.High chemoselectivity of the present approach was demonstrated by selectivity monosilylations of p-bromoiodobenzene and p-bromocinnamyl chloride to obtain (p-bromophenyl)trimethylsilane and (p-bromocinnamyl)trimethylsilane, respectively.A mechanism involving a carbanion intermediate is suggested.
- Yoshida, Jun-ichi,Muraki, Katsuhiko,Funahashi, Hirokatsu,Kawabata, Nariyoshi
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p. 3996 - 4000
(2007/10/02)
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- AN UMPOLUNG OF ARYL AND VINYL HALIDES USING TRIS-(TRIMETHYLSILYL)ALUMINUM AND APROACH TO META- AND PARA-BRIDGED AROMATICS
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Nickel and palladium catalysts effect the chemoselective and stereocontrolled umpolung of aryl and vinyl halides to trimethylsilyl derivatives; this reaction permits a regioselective approach to cyclophanes.
- Trost, Barry M.,Yoshida, Jun-ichi
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p. 4895 - 4898
(2007/10/02)
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