- THE STOICHIOMETRIC HYDROGENATION OF 9-METHYLIDENEFLUORENE AND RELATED COMPOUNDS WITH HYDRIDOCOBALT TETRACARBONYL
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9-Methylidenefluorene (IIa) reacts rapidly with HCo(CO)4 at -67 deg C to give a quantitative yield of 9-methylfluorene (IIIa); k2=(13.4 +/- 0.5)*10-2 l mol-1 s-1.Although the internal olefin, 9-ethylidenefluorene (IIb) reacts more slowly than IIa, it is hydrogenated about 2.5 times as fast as the terminal olefin, 1,1-diphenylethylene (I).Measurement of the rate of the reaction of IIb with DCo(CO)4 and comparison with HCo(CO)4 shows a very large inverse isotope effect kH/kD of 0.43.
- Nalesnik, Theodore E.,Orchin, Milton
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Read Online
- Alumina-Mediated π-Activation of Alkynes
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The ability to induce powerful atom-economic transformation of alkynes is the key feature of carbophilic π-Lewis acids such as gold- and platinum-based catalysts. The unique catalytic activity of these compounds in electrophilic activations of alkynes is explained through relativistic effects, enabling efficient orbital overlapping with π-systems. For this reason, it is believed that noble metals are indispensable components in the catalysis of such reactions. In this study, we report that thermally activated γ-Al2O3activates enynes, diynes, and arene-ynes in a manner enabling reactions that were typically assigned to the softest π-Lewis acids, while some were known to be triggered exclusively by gold catalysts. We demonstrate the scope of these transformations and suggest a qualitative explanation of this phenomenon based on the Dewar-Chatt-Duncanson model confirmed by density functional theory calculations.
- Akhmetov, Vladimir,Amsharov, Konstantin,Feofanov, Mikhail,Sharapa, Dmitry I.
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supporting information
p. 15420 - 15426
(2021/09/30)
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- Modular Tandem Mizoroki-Heck/Reductive Heck Reactions to Construct Fluorenes from Cyclic Diaryliodoniums
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Starting from cyclic diaryliodoniums and terminal alkenes, a diverse set of fluorenes is conveniently constructed. The reactions catalyzed by palladium undergo one conventional Mizoroki-Heck reaction and one reductive Heck reaction. The scope of alkenes is general, leading to 29 fluorenes which would expand the structural diversity of fluorene reservoir. (Figure presented.).
- Peng, Xiaopeng,Yang, Yang,Luo, Bingling,Wen, Shijun,Huang, Peng
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p. 222 - 226
(2020/12/01)
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- Ligand-Free Ru-Catalyzed Direct sp3 C-H Alkylation of Fluorene Using Alcohols
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The sp3 C-H alkylation of 9H-fluorene using alcohol and a Ru catalyst via the borrowing hydrogen concept has been described. This reaction was catalyzed by the [Ru(p-cymene)Cl2]2 complex (3 mol %) and exhibited a broad reaction scope with different alcohols, allowing primary and secondary alcohols to be employed as nonhazardous and greener alkylating agents with the formation of environmentally benign water as a byproduct. A variety of 9H-fluorene underwent selective and exclusive mono-C9-alkylation with primary alcohols in good to excellent isolated yield (26 examples, 50-92% yield), whereas this reaction with secondary alcohols in the absence of any external oxidants furnished the tetrasubstituted alkene as the major product. Furthermore, a base-mediated C-H hydroxylation of the synthesized 9H-fluorene derivatives afforded 9H-hydroxy-functionalized quaternary fluorene derivatives in excellent yield.
- Shaikh, Moseen A.,Agalave, Sandip G.,Ubale, Akash S.,Gnanaprakasam, Boopathy
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p. 2277 - 2290
(2020/02/04)
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- Manganese-Catalyzed Synthesis of Quaternary Peroxides: Application in Catalytic Deperoxidation and Rearrangement Reactions
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Highly efficient, selective, and direct C-H peroxidation of 9-substituted fluorenes has been achieved using a Mn-2,2′-bipyridine catalyst via radical-radical cross-coupling. Moreover, this method effectively promotes the vicinal bisperoxidation of sterically hindered various substituted arylidene-9H-fluorene/arylideneindolin-2-one derivatives to afford highly substituted bisperoxides with high selectivity over the oxidative cleavage of Ca C bond that usually forms the ketone of an aldehyde. Furthermore, a new approach for the synthesis of (Z)-6-benzylidene-6H-benzo[c]chromene has been achieved via an acid-catalyzed skeletal rearrangement of these peroxides. For the first time, unlike O-O bond cleavage, reductive C-O bond cleavage in peroxides using the Pd catalyst and H2 is described, which enables the reversible reaction to afford exclusively deperoxidized products. A detailed mechanism for peroxidation, molecular rearrangement, and deperoxidation has been proposed with preliminary experimental evidences.
- Chaudhari, Moreshwar B.,Gnanaprakasam, Boopathy,Shaikh, Moseen A.,Ubale, Akash S.
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p. 10488 - 10503
(2020/09/23)
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- T -BuOK-catalysed alkylation of fluorene with alcohols: A highly green route to 9-monoalkylfluorene derivatives
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A simple, mild and efficient protocol was developed for the alkylation of fluorene with alcohols in the presence of t-BuOK as catalyst, affording the desired 9-monoalkylfluorenes with near quantitative yields in most cases.
- Fan, Jiang-Tao,Fan, Xin-Heng,Gao, Cai-Yan,Wang, Zhenpeng,Yang, Lian-Ming
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p. 35913 - 35916
(2019/11/16)
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- Nickel-catalyzed synthesis of 9-monoalkylated fluorenes from 9-fluorenone hydrazone and alcohols
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A practical protocol was disclosed for the nickel-catalyzed C-alkylation of 9-fluorenone hydrazone with alcohols using t-BuOK as the base, and 9-monoalkylated fluorene derivatives were obtained in good yields under the benign conditions.
- Fan, Jiang-Tao,Fan, Xin-Heng,Chen, Yong-Jie,Gao, Cai-Yan,Yang, Lian-Ming
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p. 2895 - 2902
(2019/08/12)
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- Au-Catalyzed Biaryl Coupling to Generate 5- To 9-Membered Rings: Turnover-Limiting Reductive Elimination versus ?-Complexation
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The intramolecular gold-catalyzed arylation of arenes by aryl-trimethylsilanes has been investigated from both mechanistic and preparative aspects. The reaction generates 5- to 9-membered rings, and of the 44 examples studied, 10 include a heteroatom (N, O). Tethering of the arene to the arylsilane provides not only a tool to probe the impact of the conformational flexibility of Ar-Au-Ar intermediates, via systematic modulation of the length of aryl-aryl linkage, but also the ability to arylate neutral and electron-poor arenes - substrates that do not react at all in the intermolecular process. Rendering the arylation intramolecular also results in phenomenologically simpler reaction kinetics, and overall these features have facilitated a detailed study of linear free energy relationships, kinetic isotope effects, and the first quantitative experimental data on the effects of aryl electron demand and conformational freedom on the rate of reductive elimination from diaryl-gold(III) species. The turnover-limiting step for the formation of a series of fluorene derivatives is sensitive to the reactivity of the arene and changes from reductive elimination to ?-complexation for arenes bearing strongly electron-withdrawing substituents (σ > 0.43). Reductive elimination is accelerated by electron-donating substituents (ρ = -2.0) on one or both rings, with the individual σ-values being additive in nature. Longer and more flexible tethers between the two aryl rings result in faster reductive elimination from Ar-Au(X)-Ar and lead to the ?-complexation of the arene by Ar-AuX2 becoming the turnover-limiting step.
- Ball, Liam T.,Corrie, Tom J. A.,Lloyd-Jones, Guy C.,Russell, Christopher A.
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p. 245 - 254
(2021/09/04)
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- Aldehyde/ketone-catalyzed highly selective synthesis of 9-monoalkylated fluorenes by dehydrative C-alkylation with primary and secondary alcohols
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By using aldehydes or ketones as the catalyst and screening CsOH out as the more effective base than KOH in many instances, an efficient 9-C-alkylation of fluorenes with alcohols was achieved to provide a green and practical method for general synthesis of the useful 9-monoalkylated fluorenes in high selectivities. This new method tolerates a wide range of substrates including activated and unactivated primary and secondary alcohols, thus solving the issues remaining in the field and largely broadening the diversity of the 9-monoalkylated fluorenes. Consequently, fine-tuning of the alkylated fluorenes was made possible to provide specific fluorene monomers for function-oriented polyfluorenes. Preliminary mechanistic studies revealed that the external carbonyl compounds can be quantitatively regenerated and recovered in the reaction cycle.
- Chen, Jianhui,Li, Yang,Li, Shuangyan,Liu, Jianping,Zheng, Fei,Zhang, Zhengping,Xu, Qing
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p. 623 - 628
(2017/08/17)
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- Au-catalyzed biaryl coupling to generate 5- to 9-membered rings: Turnover-limiting reductive elimination versus π-complexation
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The intramolecular gold-catalyzed arylation of arenes by aryl-trimethylsilanes has been investigated from both mechanistic and preparative aspects. The reaction generates 5- to 9-membered rings, and of the 44 examples studied, 10 include a heteroatom (N, O). Tethering of the arene to the arylsilane provides not only a tool to probe the impact of the conformational flexibility of Ar-Au-Ar intermediates, via systematic modulation of the length of aryl-aryl linkage, but also the ability to arylate neutral and electron-poor arenes-substrates that do not react at all in the intermolecular process. Rendering the arylation intramolecular also results in phenomenologically simpler reaction kinetics, and overall these features have facilitated a detailed study of linear free energy relationships, kinetic isotope effects, and the first quantitative experimental data on the effects of aryl electron demand and conformational freedom on the rate of reductive elimination from diaryl-gold(III) species. The turnover-limiting step for the formation of a series of fluorene derivatives is sensitive to the reactivity of the arene and changes from reductive elimination to π-complexation for arenes bearing strongly electron-withdrawing substituents (σ > 0.43). Reductive elimination is accelerated by electron-donating substituents (ρ = -2.0) on one or both rings, with the individual σ-values being additive in nature. Longer and more flexible tethers between the two aryl rings result in faster reductive elimination from Ar-Au(X)-Ar and lead to the π-complexation of the arene by Ar-AuX2 becoming the turnover-limiting step.
- Corrie, Tom J. A.,Ball, Liam T.,Russell, Christopher A.,Lloyd-Jones, Guy C.
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supporting information
p. 245 - 254
(2017/05/29)
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- Gallium-assisted transfer hydrogenation of alkenes
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We report a rare case of alkene transfer hydrogenation using a main-group compound instead of a transition-metal complex as catalyst. We disclosed that 1, 4-cyclo-hexadiene can be used as H2 surrogate towards olefin reduction in the presence of [IPrGaCl2][SbF6]. Hydrogenative cycli-zations have also been carried out because this cationic gallium complex is also a potent hydroarylation catalyst.
- Michelet, Bastien,Bour, Christophe,Gandon, Vincent
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supporting information
p. 14488 - 14492
(2015/04/16)
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- Microwave-assisted synthesis of substituted phenanthrenes, anthracenes, acenaphthenes, and fluorenes
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Rapid coupling reactions of polycyclic aromatic halides with various N-, S-, and Se-nucleophiles under focused microwave irradiation are described. Using this method, the desired products are obtained with good to excellent yields in a short reaction time. Crown Copyright
- Chan, Shiuh-Chuan,Jang, Jing-Pei,Cherng, Yie-Jia
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body text
p. 1977 - 1981
(2009/08/08)
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- Triflic acid promoted synthesis of polycyclic aromatic compounds
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The triflic acid (CF3SO3H) promoted cyclizations of 2-styrylbiaryls are found to be useful for the synthesis of polycyclic aromatic compounds, including functionalized derivatives of polycyclic aromatic compounds and heterocyclic sys
- Li, Ang,DeSchepper, Daniel J.,Klumpp, Douglas A.
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scheme or table
p. 1924 - 1927
(2009/09/05)
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- New cyclopentadienyl, indenyl or fluorenyl substituted phosphine compounds and their use in catalytic reactions
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The invention is directed to a phosphine compound represented by general formula (1) wherein R' and R" independently are selected from alkyl, cycloalkyl and 2-furyl radicals, or R' and R" are joined together to form with the phosphorous atom a carbon-phosphorous monocycle comprising at least 3 carbon atoms or a carbon-phosphorous bicycle; the alkyl radicals, cycloalkyl radicals, and carbon-phosphorous monocycle being unsubstituted or substituted by at least one radical selected from the group of alkyl, cycloalkyl, aryl, alkoxy, and aryloxy radicals; Cps is a partially substituted or completely substituted cyclopentadien-1-yl group, including substitutions resulting in a fused ring system, and wherein a substitution at the 1-position of the cyclopentadien-1-yl group is mandatory when the cyclopentadien-1-yl group is not part of a fused ring system or is part of an indenyl group. Also claimed is the use of these phosphines as ligands in catalytic reactions and the preparation of these phosphines.
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Page/Page column 34
(2008/06/13)
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- Efficient large-scale synthesis of 9-alkylfluorenyl phosphines for Pd-catalyzed cross-coupling reactions
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The reactions of aliphatic alcohols with fluorene coupled with a transfer hydrogenation result in the facile formation of 9-alkylfluorenes, whose deprotonation with nBuLi and quenching of the fluorenyl anion with Cy 2PCl in MTBE gave 9-alkylflu
- Fleckenstein, Christoph A.,Kadyrov, Renat,Plenio, Herbert
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p. 475 - 479
(2013/01/03)
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- 9-Fluorenylphosphines for the Pd-catalyzed Sonogashira, Suzuki, and Buchwald-Hartwig coupling reactions in organic solvents and water
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The lithiation/alkylation of fluorene leads to various 9-alkyl-fluorenes (alkyl = Me. Et, /Pr, -Pr. -C18H25) in > 95% yields, for which lithiation and reaction with R2PCl (R = Cy, iPr, tBu) generates 9-alkyl, 9-PR2fluorenes which constitute electron-rich and bulky phosphine ligands. The in-situ-formed palladium-phosphinc complexes ([Na2PdCl4], phosphonium salt, base, substrates) were tested in the Sonogashira. Suzuki, and Buchwald-Hartwig reactions of aryl chlorides and aryl bromides in organic solvents. The Sonogashira coupling of aryl chlorides at 100-120°C leads to >90% yields with 1 mol % of Pd catalyst. The Suzuki coupling of aryl chlorides typically requires 0.05 mol % of Pd catalyst at 100°C in dioxane for quantitative product formation. To carry out "green" cross-coupling reactions in water, 9-ethylfluorenyldicyclohexylphosphine was reacted in sulphuric acid to generate the respective 2-sulfonated phosphonium salt. The Suzuki coupling of activated aryl chlorides by using this water-soluble catalyst requires only 0.01 mol% of Pd catalyst, while a wide range of aryl chlorides can be quantitatively converted into the respective coupling products by using 0.1-0.5 mol % of catalyst in pure water at 100°C. Difficult substrate combinations, such as naphthylboronic acid or 3-pyridylboronic acid and aryl chlorides are coupled at 100°C by using 0.1-0.5 mol % of catalyst in pure water to obtain the respective N-heterocycles in quantitative yields. The copper-free aqueous Sonogashira coupling of aryl bromides generates the respective tolane derivatives in > 95 % yield.
- Fleckenstein, Christoph A.,Plenio, Herbert
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p. 2701 - 2716
(2008/03/14)
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- Study on the reactivity of diarylmethane derivatives in supercritical alcohols media: Reduction of diarylmethanols and diaryl ketones to diarylmethanes using supercritical 2-propanol
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We found that diarylmethanols and diaryl ketones were smoothly reduced to the corresponding diarylalkanes using supercritical 2-propanol in good yields. Furthermore, we determined the specific reaction of fluorene using supercritical methanol at high temperature.
- Hatano, Bunpei,Kubo, Daisuke,Tagaya, Hideyuki
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p. 1304 - 1307
(2008/09/21)
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- Basicity of a stable carbene, 1,3-di-tert-butylimidazol-2-ylidene, in THF
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The basicity of 1,3-di-tert-butylimidazol-2-ylidene (1) was measured in THF against three hydrocarbon indicators. Both ion pairs and free ions were found and the corresponding equilibrium constants were measured. Homoconjugation was not found in either THF or DMSO. The carbene is effectively more basic in DMSO by several pK units, probably because of hydrogen bonding of 1-H+ to DMSO. Model ab initio computations are consistent with these results.
- Kim, Yeong-Joon,Streitwieser, Andrew
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p. 5757 - 5761
(2007/10/03)
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- ω-phenylalkyl-substituted zirconocene dichloride complexes as catalyst precursors for homogeneous ethylene polymerization
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The reaction of ω-phenyl-1-bromoalkanes with cyclopentadienyl sodium, indenyl lithium or fluorenyl lithium forms ω-phenylalkyl-substituted ligand precursors in high yields. The corresponding anions react with zirconium tetrachloride to give ω-phenylalkyl-
- Licht, Erik H.,Alt, Helmut G.,Karim, M. Manzurul
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p. 275 - 287
(2007/10/03)
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- Systematic ranking of nucleophiles as electron donors
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A systematic ranking of different nucleophiles (including enolates, phenolates, thiophenolates, hydroxide, cyanide) with respect to their ability to stabilise the transition state of substitution reactions has been carried out in acetonitrile and dimethyl sulfoxide. The method is based on a comparison of the rate constant, kSUB, for the substitution reaction between a given nucleophile and benzyl chloride with the rate constant, kET, for the corresponding electron transfer from an aromatic radical anion to benzyl chloride. The ratio kSUB/kET expresses the rate enhancement due to electronic interaction in the transition state, ΔGSta, of the substitution reaction. In this study, kSUB/kET ratios between 5 and 1031 were determined corresponding to ΔGSta-values of 4-175 kJ mol-1. These values cover substitution reactions going from outer-sphere electron transfer to SN2 with partial bond formation in the transition state. The kSUB/kET values are found to be largest for nucleophiles such as OH- and CN- with very poor electron-donating abilities (high oxidation potentials). When different types of nucleophile with similar oxidation potentials are compared, a decrease in kSUB/kET is observed going from sulfur-to carbon- and further to oxygen-centred nucleophiles. The ranking of nucleophiles in reactions involving electrophiles other than benzyl chloride is discussed with emphasis on steric hindrance and electronic effects.
- Daasbjerg, Kim,Knudsen, Stig R.,Sonnichsen, Katrine N.,Andrade, Adalgisa R.,Pedersen, Steen U.
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p. 938 - 948
(2007/10/03)
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- Equilibrium acidities of some sulfones and sulfoxides in tetrahydrofuran
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Ion pair acidities are reported in tetrahydrofuran (THF) solution for the lithium and cesium salts of several sulfones and one sulfoxide. These salts are shown to be monomeric in the THF solutions studied. Thermodynamic constants are reported for several salts. The results and some conductivity studies show that both the lithium and cesium salts are contact ion pairs in THF. Because of ion association the relative pKs are slightly lower for cesium salts and much lower for lithium salts than for the free ions in DMSO solution.
- Streitwieser, Andrew,Wang, George Peng,Bors, Daniel A.
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p. 10103 - 10112
(2007/10/03)
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- CRYPTATE ACIDITY SCALES. V. EQUILIBRIUM ACIDITY OF INDICATOR CH-ACIDS IN TETRAHYDROFURAN
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A scale of equilibrium cryptate acidity in tetrahydrofuran is constructed.Its distinguishing feature is the constancy of the contribution from ionic association.A method is proposed for determination of the constants for the association of the ions into ion pairs in dimethyl sulfoxide.
- Antipin, I. S.,Gareev, R. F.,Vedernikov, A. N.,Konovalov, A. I.
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p. 1039 - 1044
(2007/10/02)
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- CRYPTATE ACIDITY SCALES. VI. EFFECT OF POLARITY OF THE MEDIUM ON CRYPTATE ION-PAIR ACIDITY
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A thermodynamic analysis was made of the effects of various types of solvation interactions on ion-pair acidity.It was shown that the polarity of the medium does not have an effect on the relative cryptate acidity of organic compounds.
- Antipin, I. S.,Vedernikov, A. N.,Solomonov, B. N.,Konovalov, A. I.
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p. 1861 - 1865
(2007/10/02)
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- STEREOSELECTIVE ELECTROCHEMICAL SYNTHESIS AND CATHODIC BEHAVIOUR OF (9-exo-BENZYL-η6-FLUORENE)CHROMIUM TRICARBONYL
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The one-electron electrochemical reductive cleavage of (η6-fluorene)Cr(CO)3 gives the (η6-fluorenyl)Cr(CO)3 anion.This anion reacts at 0 deg C in DMF with benzyl chloride present in excess during electrolysis to give (9-exo-benzylfluorene)Cr(CO)3 stereoselectively in 64percent yield.At higher temperatures there is competing formation of the exo and endo isomers.The reaction of Cr(CO)6 with 9-benzylfluorene is neither stereoselective nor regioselective, and gives moderate yields of the exo and endo isomers (26 and 17percent, respectively).The one-electron reduction of the exo isomer generates the conjugate base which initiates the exo-endo transformation.In the presence of benzyl chloride, the base-catalyzed isomerization competes with a slow benzylation of the base, and (9,9'-dibenzylfluorene)Cr(CO)3 can be isolated.
- Gautheron, B.,Degrand, C.,Bikrani, M.
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p. 207 - 220
(2007/10/02)
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- ACIDIFYING EFFECTS OF AZA GROUPS IN THE NH ACIDITY OF AMINOAZINES AND THE CH ACIDITY OF ACETYLAZINES
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The pK values for a series of aminoazines and acetylazines containing one, two, or three aza groups in the ring were determined in dimethyl sulfoxide.There is a good linear correlation between pK values of the investigated NH and CH acids.The acidifying effects (ΔpK) of the aza groups at positions 2, 3, or 4 in relation to the side chain were determined and had values of 3.1, 2.4, and 4.5 logarithmic units in the aminoazines and 3.5, 2.9 and 4.8 logarithmic units respectively in the acetylazines.Except in the case of two ortho-located aza groups the effects are additive.Compared with dimethyl sulfoxide water has a differentiating effect on the acidity of the aminoazines, and this is explained by the formation of hydrogen bonds between the molecules of the proton-donating solvent and the aza groups of the anions of the aminoazines.
- Terekhova, M. I.,Petrov, E. S.,Mikhaleva, M. A.,Shkurko, O. P.,Mamaev, V. P.,Shatenshtein, A. I.
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- HYDROGENATION REACTIONS WITH HYDRIDOCOBALT TETRACARBONYL
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The tetrasubstituted ethylene, bifluorenylidene, reacts very rapidly (4.06*10-2 l mol-1 sec-1 at 0 deg C) with HCo(CO)4 to give bifluorenyl. α-Phenylacrylonitrile (atroponitrile) reacts even more rapidly under the same conditions (6.0 l mol-1 sec-1).Other highly substituted ethylenes react very slowly with HCo(CO)4, indicating considerable steric effects.The data are consistent with radical type intermediates.
- Nalesnik, Theodore E.,Freudenberger, John H.,Orchin, Milton
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p. 193 - 198
(2007/10/02)
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