- Nickel-catalyzed synthesis of 9-monoalkylated fluorenes from 9-fluorenone hydrazone and alcohols
-
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
-
supporting information
p. 2895 - 2902
(2019/08/12)
-
- T -BuOK-catalysed alkylation of fluorene with alcohols: A highly green route to 9-monoalkylfluorene derivatives
-
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
-
p. 35913 - 35916
(2019/11/16)
-
- Transition-metal-free intramolecular carbene aromatic substitution/Büchner reaction: Synthesis of fluorenes and [6,5,7]benzo-fused rings
-
Intramolecular aromatic substitution and Büchner reaction have been established as powerful methods for the construction of polycyclic compounds. These reactions are traditionally catalyzed by RhII catalysts with a-diazocarbonyl compounds as the substrates. Herein a transition-metal-free intramolecular aromatic substitution/Büchner reaction is presented. These reactions use readily available N-tosylhydrazones as the diazo compound precursors and show wide substrate scope.
- Liu, Zhenxing,Tan, Haocheng,Wang, Long,Fu, Tianren,Xia, Ying,Zhang, Yan,Wang, Jianbo
-
supporting information
p. 3056 - 3060
(2015/03/30)
-
- A zwitterionic carbanion frustrated by boranes - Dihydrogen cleavage with weak lewis acids via an "inverse" frustrated lewis pair approach
-
The synthesis, structural characterization, and acid-base chemistry of [C(SiMe2OCH2CH2OMe)3]Na (2), a sterically encumbered zwitterionic organosodium compound, is reported. 2 is a strong Bronsted base that forms frustrated Lewis pairs (FLPs) with a number of boron-containing Lewis acids ranging from weakly Lewis acidic aryl and alkyl boranes to various alkyl borates. These intermolecular FLPs readily cleave H2, which confirms that even poor Lewis acids can engage in FLP-mediated H2 cleavage provided that the present bulky base is of sufficiently high Bronsted basicity.
- Li, Hui,Aquino, Adelia J. A.,Cordes, David B.,Hung-Low, Fernando,Hase, William L.,Krempner, Clemens
-
supporting information
p. 16066 - 16069
(2013/11/19)
-
- Steric effects which determine the conformational preferences and stereodynamic processes of aryl fluorenyl ketones
-
The stereodynamic processes and conformational preferences of two classes of aryl fluorenyl ketones have been investigated by means of dynamic NMR spectroscopy, DFT calculations and X-ray diffraction. When the aryl substituent has two hydrogens in the ortho positions, its rotation is independent of that of the fluorene ring. In contrast, if the two ortho hydrogens are replaced by the bulkier methyl groups (e.g. mesityl fluorenyl ketones), the motion of the aryl ring interacts with the fluorene, and the two rings rotate in a correlated manner.
- Casarini, Daniele,Lunazzi, Lodovico,Mazzanti, Andrea
-
supporting information; experimental part
p. 1619 - 1626
(2009/06/27)
-
- New cyclopentadienyl, indenyl or fluorenyl substituted phosphine compounds and their use in catalytic reactions
-
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.
- -
-
Page/Page column 34
(2008/06/13)
-
- Stereomutation of conformational enantiomers of 9-isopropyl-9- formylfluorene and related acyl derivatives
-
(Figure Presented) Low-temperature NMR spectra show that the title compound exists as a pair of conformational enantiomers, generated by the restricted rotation about the C9-Pri bond, the corresponding interconversion barrier being 6.9 kcal mol-1. This interpretation is supported by theoretical (MM and DFT) calculations and by the experimental determination of the analogous barriers occurring in the related MeC=O and ButC=O derivatives.
- Casarini, Daniele,Lunazzi, Lodovico,Mazzanti, Andrea
-
p. 6382 - 6385
(2008/12/22)
-
- 9-Fluorenylphosphines for the Pd-catalyzed Sonogashira, Suzuki, and Buchwald-Hartwig coupling reactions in organic solvents and water
-
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
-
p. 2701 - 2716
(2008/03/14)
-
- Unverbrueckte fluorenylkomplexe des typs (C5H5)(9-R-C13H8)ZrCl2 (R = Me3Si, Alkyl, Aryl): Synthese, charakterisierung und anwendung als katalysatoren bei der homogenen olefinpolymerisation
-
The reaction of various 9-substituted fluorene compounds (9-R-C13H9) (R = Me3Si, alkyl, aryl) (1a-i) with butyllithium followed by treatment with (C5H5)ZrCl3 leads to unbridged fluorenyl complexes of the type (C5H5)(9-R-C13H8)ZrCl2 (2a-i). In combination with methylaluminoxane, complexes 2a-i show a high catalytic activity as homogeneous ethylene polymerization catalysts. Compounds 2c (R = iPr), 2d (R = cyclohexyl), and 2e (R = tBu) were characterized by X-ray structure analyses.
- Schmid, Michael A.,Alt, Helmut G.,Milius, Wolfgang
-
-
- Proton-Transfer Reactions between 9-Alkylfluorene and (9-Alkylfluorenyl)lithium in Ether
-
The rates of proton-transfer reactions between 9-substituted fluorenes and 9-substituted fluorenyllithium have been examined in ether at 25 and 71 deg C.A high primary isotope effect (kH/kD = 9.5) and substantial secondary kinetic (1.11 +/- 0.04) and equilibrium (1.19 +/- 0.04) isotope effects are observed for fluorene.Surprisingly, intermolecular steric effects seem to play only a minor role in spite of the fact that the alkyl groups are located directly at the carbon involved in the proton transfer.The barriers for the endergonic cross reactions (i.e., those involving different alkyl groups in the anion and hydrocarbon) are half of the sum of the barriers for the two corresponding identity reactions (i.e., those involving the same alkyl groups in the anion and hydrocarbon).This leads to Broensted slopes which vary from 0.7 for reactions of fluorenyl anion to 1.8 for reactions of 9-(tert-butyl)fluorenyl anion.The rates of the identity and cross reactions give approximate linear correlations with each other and with ΔpK and are dominated by an effect which correlates with ?*.The substituent effect correlated by ?* is inconsistent with a classical field or repulsive steric effect and may originate from solvatation effects.The thermodynamic and kinetic relationships between the identity and cross reactions show that the transition states for the cross reac tions are only responding to half of the substituent effect on the identity reactions and that the substituent effect on the equilibria appears absent from the cross-reaction transition states.The results can be consistent with Marcus' theory only if the substituent effect on the equilibria appears in steps separate from proton transfer.The results suggest that changes in solvation and proton transfer occur as discrete kinetic steps.
- Murdoch, J. R.,Bryson, J.A.,McMillen, D.F.,Brauman, J.I.
-
p. 600 - 610
(2007/10/02)
-
- HYDROGENATION REACTIONS WITH HYDRIDOCOBALT TETRACARBONYL
-
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
-
p. 193 - 198
(2007/10/02)
-