- Lewis acid-catalyzed tandem synthesis of 9-sulfonylamino- and 9-arylfluorenes
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A Lewis acid-catalyzed three-step tandem synthesis of 9-arylfluorene was developed by simply heating a mixture of 2-formyl biphenyl, TsNCO and an arene. In the absence of arene, a two-step tandem synthesis of 9-sulfonylaminofluorene was achieved. These ad
- Huang, Dayun,Yang, Weiguang,Zhang, Jianlan,Wang, Xuesong,Wang, Xinyan,Hu, Yuefei
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p. 47570 - 47578
(2016/06/06)
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- Solvent control of product diversity in palladium-catalyzed addition of arylboronic acid to aryl aldehydes
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In Pd-catalyzed arylboronic acid addition to aryl aldehydes, the expected carbinol or asymmetrical ether can be obtained as the major product by altering aqueous solvent composition. Exploiting this methodology with 2-formylbiphenyls as reaction partner, a fluorene scaffold can be readily constructed in two steps.
- Das, Tuluma,Chakraborty, Amarnath,Sarkar, Amitabha
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p. 5174 - 5178
(2014/12/10)
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- TfOH catalyzed synthesis of 9-arylfluorenes via tandem reaction under warm and efficient conditions
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A tandem ring-closing reaction was developed for the synthesis of 9-arylfluorenes and their derivatives. The reaction is metal-free, straightforward and efficient under warm conditions. More than 99% yield is obtained. This journal is the Partner Organisations 2014.
- Li, Qingcui,Xu, Wengang,Hu, Jiaxing,Chen, Xiaoqing,Zhang, Fanglin,Zheng, Hua
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p. 27722 - 27725
(2014/07/21)
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- Iron-catalyzed arylation of aromatic ketones and aldehydes mediated by organosilanes
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A simple and efficient iron-catalyzed method for arylation of aromatic carbonyl compounds is reported. The use of 4-% FeCl3 or Fe(acac) 3 as the catalyst, in combination with a slight excess of chlorotrimethylsilane and triethylsilane, chlorination of benzylic ketones and aldehydes with subsequent Friedel-Crafts alkylation of arenes is achieved. Although the method is limited by the general constraints associated with Friedel-Crafts alkylation reactions, robust applications for the synthesis of pharmaceutical intermediates and so on can be envisioned. A robust one-pot, iron-catalyzed chlorination Friedel-Crafts alkylation reaction of benzylic carbonyl compounds, mediated by chlorotrimethylsilane and triethylsilane, has been developed to yield substituted diaryl and triaryl building blocks. Copyright
- Savela, Risto,Majewski, Marcin,Leino, Reko
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p. 4137 - 4147
(2014/07/08)
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- Flash photolysis study of a Friedel-Crafts alkylation. Reaction of the photogenerated 9-fluorenyl cation with aromatic compounds
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A combination of flash photolysis and product analysis is employed to investigate the reaction of aromatic compounds (ArH) with the 9-fluorenyl cation (Fl+) photogenerated from 9-fluorenol in 1,1,1,3,3,3-hexafluoroisopropyl alcohol (HFIP).The availability of the photochemical route to Fl+ means that the reaction of benzylic-type cation with ArH can be directly followed by flash photolysis.An additional feature with electron-rich ArH is that the cyclohexadienyl cation is observed to grow as Fl+ decays.Thus both cationic intermediates of a Friedel-Crafts alkylation are observed in the same experiment.The formation of the cyclohexadienyl cation is demonstrated to be reversible, or at least quasi-reversible, with the kinetic analysis furnishing absolute rate constants for the formation of this cation as well as for its loss of H+ and Fl+.Values of kH:kD for benzene:benzene and toluene:toluene are ca. 1.5 and demonstrate that Fl+ addition is at least partly reversible with these compounds as well.The Hammett ρ+ value obtained for a series of the less electron-rich ArH is -8, indicative of a transition state with considerable cyclohexadienyl cation character.Anisole shows a negative deviation from from Hammett correlation line, explained by the addition of Fl+ to ArH becoming encounter-controlled.This behaviour is dramatically illustrated in a comparison of data for Fl+ and Br2.For the less electron-rich ArH, rate constants for the two electrophiles are parallel.However, from m-xylene through pentamethylbenzene, the rate with Fl+ is unchanged, while the rate with Br2 increases over 1000-fold.The concept of encounter control with Fl+ is strongly supported by the absolute rate constants, which for the electron-rich ArH are all in the range 1-2 E9 dm3 mol-1 s-1, a magnitude typical of diffusion-controlled reactions.The electron-rich ArH also show no intermolecular selectivity since their reactions are encounter-controlled, but have a high intramolecular selectivity.It is suggested that a factor influencing the latter is the reversibility of formation of the cyclohexadienyl cation from the encounter complex.
- McClelland, Robert A.,Cozens, Frances L.,Li, Jianhui,Steenken, Steen
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p. 1531 - 1544
(2007/10/03)
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- Unverbrueckte fluorenylkomplexe des typs (C5H5)(9-R-C13H8)ZrCl2 (R = Me3Si, Alkyl, Aryl): Synthese, charakterisierung und anwendung als katalysatoren bei der homogenen olefinpolymerisation
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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
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- A Novel Redox Reaction of the Disulphide Dication Salt (R2S+-+SR2*2X-) with Carbanions and Alkoxides
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The disulphide dication salt, 1,5-dithioniabicyclooctane bis(trifluoromethanesulphonate) (1) was reduced upon treatment with carbanions or alkoxides; it did not deprotonate.
- Fujihara, Hisashi,Akaishi, Ryouichi,Furukawa, Naomichi
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p. 147 - 148
(2007/10/02)
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- Kinetics and Mechanism of the Reaction of 9-Arylfluoren-9-yl Cations with Polymethylbenzenes in Trifluoroacetic Acid Solution
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9-Arylfluoren-9-yl cations, ArFl+, generated from the alcohol in CF3CO2H solution, are reduced to ArFlH by the polymethylated aromatic hydrocarbons (Ar1CH3) hexamethylbenzene, pentamethylbenzene, 1,2,3,4-, 1,2,3,5-, and 1,2,4,5-tetra
- Bethell, Donald,Clare, Peter N.,Hare, Gerard J.
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p. 1889 - 1894
(2007/10/02)
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- Stabilization of Carbanions by Polarization of Alkyl Groups on Nonadjacent Atoms
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Equilibrium acidities in dimethyl sulfoxide solution have been found to increase along the series Me, Et, i-Pr, t-Bu for 9-substituted fluorenes when the alkyl group, R, is separated from the fluorene ring by a CH2, S, or SO2 moiety.This is a reversal of
- Bordwell, Frederick G.,Drucker, George E.,McCollum, Gregory J.
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p. 2504 - 2510
(2007/10/02)
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- Kinetic Hydrogen Isotope Effects in Intermolecular Hydride Transfer from Arylalkanes to 9-Arylfluoren-9-yl Cations
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Rates of hydride-ion transfer to a series of 9-phenylfluoren-9-yl cations, substituted in the phenyl group, from triphenylmethane and 4,4'-dimethoxydiphenylmethane have been measured at 30 degC in trifluoroacetic acid solution containing 6percent v/v acet
- Bethell, Donald,Hare, Gerard J.,Kearney, Paul A.
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p. 684 - 691
(2007/10/02)
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