- Palladium-catalyzed coupling reaction of 2-iodobiphenyls with alkenyl bromides for the construction of 9-(diorganomethylidene)fluorenes
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An atom economical protocol for the construction of 9-(diorganomethylidene)fluorenes through palladium-catalyzed coupling reactions of 2-iodobiphenyls with alkenyl bromides has been reported. The reaction proceeds through the C-H activation/oxidative addition/reduction elimination/intramolecular Heck coupling reaction to afford a series of 9-(diorganomethylidene)fluorenes with good yields. Control experiments demonstrate that a five-membered palladacycle acts as a key intermediate and β-H elimination serves as the rate-limiting step.
- Zhao, Ya-Heng,Wang, Jian-Long,Zhou, Yun-Bing,Liu, Miao-Chang,Wu, Hua-Yue
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supporting information
p. 8250 - 8253
(2021/10/12)
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- Synthesis of 9-Fluorenylidenes via Pd-Catalyzed C-H Vinylation with Vinyl Bromides
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A facile and efficient approach for the synthesis of 9-fluorenylidenes has been developed via the palladium-catalyzed cross-coupling of 2-iodobiphenyls and vinyl bromides. The reaction involves the C-H activation of 2-iodobiphenyls and dual C-C bond formations. A range of 9-fluorenylidene derivatives, including diphenyldibenzofulvenes, can be synthesized with the reaction.
- Yang, Shuai,Zhang, Yanghui
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supporting information
p. 7746 - 7750
(2021/10/12)
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- An N-heterocyclic carbene-catalyzed switchable reaction of 9-(trimethylsilyl)fluorene and aldehydes: Chemoselective synthesis of dibenzofulvenes and fluorenyl alcohols
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An N-heterocyclic carbene-catalyzed synthesis of dibenzofulvenes and fluorenyl alcohols was developed. In the presence of 10 mol% NHC (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and 4 ? molecular sieves, 9-(trimethylsilyl)fluorene undergoes an olef
- Ma, Yu-Chuan,Luo, Jin-Yun,Zhang, Shi-Chu,Lu, Shu-Hui,Du, Guang-Fen,He, Lin
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supporting information
p. 3717 - 3721
(2021/05/04)
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- Iron(III) nitrate-induced aerobic and catalytic oxidative cleavage of olefins
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Microwave-assisted catalytic oxidative cleavage of olefins using Fe(NO3)3·9H2O under O2 is reported. This reaction system is particularly effective when 9-benzylidene-9H-fluorene derivatives are used as substrates even though they are tri- and tetra-substituted olefins.
- Amaya, Toru,Fujimoto, Hayato
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p. 2657 - 2660
(2018/06/04)
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- Pd-Catalyzed Autotandem Reactions with N-Tosylhydrazones. Synthesis of Condensed Carbo- and Heterocycles by Formation of a C-C Single Bond and a C-C Double Bond on the Same Carbon Atom
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A new Pd-catalyzed autotandem reaction is introduced that consists of the cross-coupling of a benzyl bromide with a N-tosylhydrazone followed by an intramolecular Heck reaction with an aryl bromide. During the process, a single and a double C-C bond are formed on the same carbon atom. Two different arrangements for the reactive functional groups are possible, rendering great flexibility to the transformation. The same strategy led to 9-methylene-9H-fluorenes, 9-methylene-9H-xanthenes, 9-methylene-9,10-dihydroacridines, and also dihydropyrroloisoquinoline and dihydroindoloisoquinoline derivatives.
- Paraja, Miguel,Valdés, Carlos
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p. 2034 - 2037
(2017/04/27)
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- Three-component Pd/Cu-catalyzed cascade reactions of cyclic iodoniums, alkynes, and boronic acids: An approach to methylidenefluorenes
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Linear diaryliodonium salts are widely used as arylating reagents for C-C and C-X bond formation. Meanwhile, synthetic applications of cyclic iodoniums are relatively rare although they offer the opportunity to set up reaction cascades. We demonstrate an atom and step economical three-component reaction involving cyclic diphenyleneiodoniums, alkynes, and boronic acids, resulting in the construction of methylidenefluorenes in a single operation. Our route enables facile access to both symmetrical and unsymmetrical methylidenefluorene derivatives, compounds that have attracted interest due to their optical properties.
- Zhu, Daqian,Wu, Yongcheng,Wu, Baojian,Luo, Bingling,Ganesan,Wu, Fu-Hai,Pi, Rongbiao,Huang, Peng,Wen, Shijun
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supporting information
p. 2350 - 2353
(2014/05/20)
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- Dications of benzylidenefluorene and diphenylmethylidene fluorene: The relationship between magnetic and energetic measures of antiaromaticity
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Oxidation of m- and p-substituted benzylidene fluorenes to antiaromatic dications was attempted by electrochemical and chemical means. Electrochemical oxidation to dications was successful for benzylidene fluorenes with p-methoxy, p-methyl, p-fluoro, and
- Do, Catherine,Hatfield, Julianne,Patel, Shirali,Vasudevan,Tirla, Cornelia,Mills, Nancy S.
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supporting information; experimental part
p. 181 - 187
(2011/03/19)
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- A comparative study in oxidative free radical reactions between 9-benzylidene-9-h fluorene derivatives and β-dicarbony1 compounds in the presence of mn(oac) 3 and can
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The reactions of some 1,3-dicarbonyl compounds with 9-benzylidene-9-H- fluorene derivatives in the presence of manganese(III)acetate and ceric ammonium nitrate (CAN) were searched. 9-benzylidene-9-H-fluorene compounds form mainly [2+3] dipolar cycloadditi
- Demirhan, Hulya,Arslan, Mustafa,Zengin, Mustafa,Kucukislamoglu, Mustafa
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scheme or table
p. 488 - 494
(2012/04/23)
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- Synthesis of fluorenes via the palladium-catalyzed 5-exo-dig annulation of o-alkynylbiaryls
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The direct palladium-catalyzed intramolecular hydro arylation of o-alkynylbiaryls proceeded in a highly stereoselective manner producing fluorenes 2, the products of 5-exo-dig cyclization, in excellent yields. The cascade intermolecular arylation, incorpo
- Chernyak, Natalia,Gevorgyan, Vladimir
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experimental part
p. 1101 - 1114
(2009/12/07)
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- Exclusive 5-exo-dig hydroarylation of o-alkynyl biaryls proceeding via C-H activation pathway
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The first example of the palladium-catalyzed exclusive 5-exo-dig hydroarylation of o-alkynyl biaryls has been demonstrated. In contrast to the reported earlier carbocyclizations proceeding via the Friedel-Crafts mechanism, this hydroarylation efficiently proceeds with electron-neutral and electron-deficient arenes, producing fluorene frameworks with defined stereochemistry of the double bond. On the basis of the high reactivity of electron-deficient arenes toward cyclization, high values of inter- and intramolecular kinetic isotope effects, and the exclusive cis-selectivity of cyclization, a mechanism involving a C-H activation motif has been proposed for this transformation. Copyright
- Chernyak, Natalia,Gevorgyan, Vladimir
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p. 5636 - 5637
(2008/12/22)
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- New strategies for an efficient removal of the 9- fluorenylmethoxycarbonyl (Fmoc) protecting group in the peptide synthesis
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The aluminium trichloride/toluene system is investigated as a novel, unusual and straightforward reagent for the removal of the 9- fluorenylmethoxycarbonyl (Fmoc) protecting group in the solution peptide synthesis. This procedure avoids any undesired side reactions, such as the frequently observed inversion of the amino acid configuration.
- Leggio, Antonella,Liguori, Angelo,Napoli, Anna,Siciliano, Carlo,Sindona, Giovanni
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p. 573 - 575
(2007/10/03)
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- Potassium fluoride supported on alumina induced aldol condensation of fluorene
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In the presence of potassium fluoride supported on alumina as a solid base, fluorene condensated smoothly with aromatic aldehydes in DMF at 150°C to give dibenzofulvenes in fair yield (44-90%).
- Lu, Wen-Xing,Yan, Chao-Guo,Yao, Rong
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p. 3719 - 3723
(2007/10/03)
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- Photochemical Formation and Electrophilic Reactivities of Vinyl Cations. Influence of Substituents, Anionic Leaving Groups, Solvents, and Excitation Wavelength on Photoheterolysis and Photohomolysis of 1-(p-R-Phenyl)-2-(2,2'-biphenyldiyl)vinyl Halides
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Using product analysis and time-resolved laser flash photolysis techniques, the photochemistry at λexc ca. 250 and 310 nm (exc = excitation) of 1-(p-R-phenyl)-2-(2,2'-biphenyldiyl)vinyl halides (R = H, Me, MeO) in methanol and acetonitrile at room temperature was studied.The title compounds undergo photoheterolysis and photohomolysis to give vinyl cations =C+- (carbenium ions) and vinyl radicals =C.-.The cation : radical ratio increases with electron-donating strength of the substituent R, H - - - -, indicating that the cleavage of the C-X bond to yield cation and halide anion proceeds, in the rate-determining step, by heterolysis and not by homolysis followed by electron transfer in the radical pair.The cation : radical ratio is solvent dependent: e.g., for the vinyl bromide with R = MeO and with λexc = 308 nm, in CH2Cl2 as solvent, only radical is observed, in comparison with only cation in the much more polar solvent acetonitrile.In acetonitrile-methanol mixtures, the absolute yields of both cation and radical go through a maximum as the methanol content is increased, however, the catio : radical ratio decreases continuously with increasing .For a particular R, the quantum yield for C-X bond cleavage is higher at ca. 250 than at ca. 310 nm.Also, the cation : radical ratio is wavelength-dependent: at λexc ca. 310 nm there is relatively more heterolysis than at λexc ca. 250 nm.Rate constants for reaction of the cations with nucleophiles were determined in acetonitrile.Those for reaction of the cation with R = MeO (lifetime in acetonitrile 7 μs) with anionic nucleophiles such as the halides are at the diffusion limit in this solvent, ca. 2 * 1010 M-1 s-1, whereas those for reaction with water, alcohols, and cyclic ethers are of the order 105-106 M-1 s-1.The less stabilized cation (R = Me) reacts with alcohols faster by the factor ca. 100, and it decays in acetonitrile ca. 100 times more rapidly.Also, 1-(p-R-phenyl)-2-dimehtylvinyl bromides (R = H, Me, MeO) were photolyzed in acetonitrile.In the case of R = MeO, the cation p-CH3O-C6H4-C+=CMe2 was seen (lifetime 770 ns), and its reactivity with alcohols (k values of 106-107 M-1 s-1) and halides (k values of 1010 M-1 s-1) was determined.The vinyl radicals =C.- react with O2 to yield vinylperoxyl radicals =C-O2. which have absorption maxima at ca. 390 nm.
- Verbeek, Jan-Maarten,Stapper, Marion,Krijnen, Erik S.,Loon, Jan-Dirk van,Lodder, Gerrit,Steenken, Steen
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p. 9526 - 9536
(2007/10/02)
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- Effect of Bulky Size of Carbonyl Systems on Betaine Decomposition of Semi-stablized Arsonium Ylids
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Reactions of substituted benzylidentriphenylarsenanes (2a-i) with 9-anthraldehyde and 9-fluorenone have been studied using benzene-sodamide, chloroform-sodium hydride and methanol-sodium ethoxide as solvent-base pairs.In all the cases olefins (5a-i and 6a-i) are formed exclusively.Variation of solvents and bases has no effect on the course of betaine decomposition formed by the nucleophilic attack of ylids on carbonyl systems.
- Gupta, K. C.,Srivastava, N.,Nigam, R. K.
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p. 802 - 803
(2007/10/02)
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