- Iron-catalysed allylation-hydrogenation sequences as masked alkyl-alkyl cross-couplings
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An iron-catalysed allylation of organomagnesium reagents (alkyl, aryl) with simple allyl acetates proceeds under mild conditions (Fe(OAc)2 or Fe(acac)2, Et2O, r.t.) to furnish various alkene and styrene derivatives. Mechanistic studies indicate the operation of a homotopic catalyst. The sequential combination of such iron-catalysed allylation with an iron-catalysed hydrogenation results in overall C(sp3)-C(sp3)-bond formation that constitutes an attractive alternative to challenging direct cross-coupling protocols with alkyl halides.
- Bernauer, Josef,Wu, Guojiao,Von Wangelin, Axel
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p. 31217 - 31223
(2019/10/19)
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- Visible-Light-Promoted Iron-Catalyzed C(sp2)–C(sp3) Kumada Cross-Coupling in Flow
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A continuous-flow, visible-light-promoted method has been developed to overcome the limitations of iron-catalyzed Kumada–Corriu cross-coupling reactions. A variety of strongly electron rich aryl chlorides, previously hardly reactive, could be efficiently coupled with aliphatic Grignard reagents at room temperature in high yields and within a few minutes’ residence time, considerably enhancing the applicability of this iron-catalyzed reaction. The robustness of this protocol was demonstrated on a multigram scale, thus providing the potential for future pharmaceutical application.
- Wei, Xiao-Jing,Abdiaj, Irini,Sambiagio, Carlo,Li, Chenfei,Zysman-Colman, Eli,Alcázar, Jesús,No?l, Timothy
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supporting information
p. 13030 - 13034
(2019/07/18)
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- Umpolung of Carbonyl Groups as Alkyl Organometallic Reagent Surrogates for Palladium-Catalyzed Allylic Alkylation
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Palladium-catalyzed allylic alkylation of nonstabilized carbon nucleophiles is difficult and remains a major challenge. Reported here is a highly chemo- and regioselective direct palladium-catalyzed C-allylation of hydrazones, generated from carbonyls, as a source of umpolung unstabilized alkyl carbanions and surrogates of alkyl organometallic reagents. Contrary to classical allylation techniques, this umpolung reaction utilizes hydrazones prepared not only from aryl aldehydes but also from alkyl aldehydes and ketones as renewable feedstocks. This strategy complements the palladium-catalyzed coupling of unstabilized nucleophiles with allylic electrophiles by providing an efficient and selective catalytic alternative to the traditional use of highly reactive alkyl organometallic reagents.
- Zhu, Dianhu,Lv, Leiyang,Li, Chen-Chen,Ung, Sosthene,Gao, Jian,Li, Chao-Jun
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p. 16520 - 16524
(2018/11/23)
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- Palladium-Catalyzed Electrochemical Allylic Alkylation between Alkyl and Allylic Halides in Aqueous Solution
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A new route for the direct cross-coupling of alkyl and allylic halides using electrochemical technique has been developed in aqueous media under air. Catalyzed by Pd(OAc)2, the Zn-mediated allylic alkylations proceed smoothly between a full range of alkyl halides (primary, secondary, and tertiary) and substituted allylic halides. Protection-deprotection of acidic hydrogen in the substrates is avoided.
- Lai, Yin-Long,Huang, Jing-Mei
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supporting information
p. 2022 - 2025
(2017/04/28)
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- Selective hydrogenolysis of phenols and phenyl ethers to arenes through direct C-O cleavage over ruthenium-tungsten bifunctional catalysts
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Direct hydrogenolysis of the aromatic Csp2-O bonds in both phenols and phenyl ethers to form arenes selectively is a core enabling technology that can expand greatly the scope of chemical manufacture from biomass. However, conventional hydrogenolysis of phenols typically led to aromatic ring saturation instead of the cleavage of the Csp2-O bonds. Herein, we report a recyclable Ru-WOx bifunctional catalyst that showed high catalytic activities for the hydrogenolysis of a wide range of phenols and phenyl ethers, including dimeric lignin model compounds and the primitive phenols separated from pyrolysis lignin, to form arenes selectively in water. Preliminary mechanistic studies supported that the reactions occurred via a direct cleavage of the Csp2-O bonds and the concerted effects of the hydrogenating Ru sites and the Lewis acidic W sites are the key to such an unusual reactivity.
- Huang, Yao-Bing,Yan, Long,Chen, Meng-Yuan,Guo, Qing-Xiang,Fu, Yao
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p. 3010 - 3017
(2015/05/27)
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- Regioselective allene hydroarylation via one-pot allene hydrosilylation/Pd-catalyzed cross-coupling
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Advances in hydroarylation have been achieved by the development of a one-pot regioselective allene hydrosilylation/Pd(0)-catalyzed cross-coupling protocol. The regioselectivity is primarily governed by N-heterocyclic carbene (NHC) ligand identity in the hydrosilylation step and is preserved in the subsequent cross-coupling reaction. This methodology affords streamlined access to functionalized 1,1-disubstituted alkenes with excellent regiocontrol. (Chemical Equation Presented).
- Miller, Zachary D.,Montgomery, John
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supporting information
p. 5486 - 5489
(2015/01/09)
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- Copper-catalyzed selective semihydrogenation of terminal alkynes with hypophosphorous acid
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A novel copper-catalyzed selective semihydrogenation of terminal alkynes using hypophosphorous acid as hydrogen donor took place efficiently to afford the corresponding alkenes in high yields. A broad range of substituted terminal aromatic and aliphatic alkenes, including terminal dienes and enynes bearing internal triple bonds, can be efficiently synthesized by this reaction.
- Cao, Huanyang,Chen, Tieqiao,Zhou, Yongbo,Han, Daoqing,Yin, Shuang-Feng,Han, Li-Biao
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p. 765 - 769
(2014/04/03)
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- Efficient and exceptionally selective semireduction of alkynes using a supported gold catalyst under a CO atmosphere
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A new efficient method for chemo- and regio-selective semireduction of alkynes using CO/H2O as the hydrogen source catalyzed by gold supported on high surface area TiO2 was developed. A facile and practical synthesis of 1,2-dideuterioalkenes was also realized by using CO/D2O as the reducing agent. the Partner Organisations 2014.
- Li, Shu-Shuang,Liu, Xiang,Liu, Yong-Mei,He, He-Yong,Fan, Kang-Nian,Cao, Yong
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supporting information
p. 5626 - 5628
(2014/05/20)
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- High-yielding and rapid carbon-carbon bond formation from alcohols: Allylation by means of TiCl4
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TiCl4 efficiently promotes high yield (80-99%) replacement of OH in tertiary, benzylic, and allylic alcohols, and even nonactivated secondary alcohols, by an allyl group. The reaction usually proceeds within minutes at room temperature. Georg Thieme Verlag Stuttgart. New York.
- Hassner, Alfred,Bandi, Chennakesava Reddy
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p. 1275 - 1279
(2013/07/11)
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- IRON BISPHENOLATE COMPLEXES AND METHODS OF USE AND SYNTHESIS THEREOF
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The present application, relates to iron bisphenolate complexes and methods of use and synthesis thereof. The iron complexes are prepared from tridentate or tetradentate ligands of Formula I: wherein R1 and R2 are as defined herein. Also provided are methods and processes of using the iron bisphenolate complexes as catalysts in cross-coupling reactions and in controlled radical polymerizations.
- -
-
Paragraph 00193-00195
(2013/04/25)
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- Copper-catalyzed highly selective semihydrogenation of non-polar carbon-carbon multiple bonds using a silane and an alcohol
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A copper catalyst bearing a suitable Xantphos derivative or NHC ligand was found to be highly efficient for the selective semihydrogenation of non-polar unsaturated compounds using a mixture of a silane and an alcohol as reducing agent. The catalytic system was useful for the selective semihydrogenation of internal alkynes to (Z)-alkenes with suppression of overreduction to the corresponding alkanes. Furthermore, semihydrogenations of terminal alkyne, 1,2-diene, 1,3-diene, 1,3-enyne and 1,3-diyne systems were also achieved selectively. Copyright
- Semba, Kazuhiko,Fujihara, Tetsuaki,Xu, Tinghua,Terao, Jun,Tsuji, Yasushi
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supporting information; experimental part
p. 1542 - 1550
(2012/08/08)
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- Cobalt-catalyzed reductive allylation of alkyl halides with allylic acetates or carbonates
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An efficient method for the direct allylation of alkyl halides catalyzed by simple cobalt(II) bromide has been developed. This reaction, using a variety of substituted allylic acetates or carbonates, provides the linear product as the major product. It displays broad substrate scope and good functional group tolerance. Copyright
- Qian, Xin,Auffrant, Audrey,Felouat, Abdellah,Gosmini, Corinne
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supporting information; experimental part
p. 10402 - 10405
(2011/12/03)
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- Structure and C-C cross-coupling reactivity of iron(III) complexes of halogenated amine-bis(phenolate) ligands
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The preparation of tetradentate amine-bis(phenol) proligands with dichloro and difluoro substituted phenol groups and their reaction with FeX3 (X = Cl or Br) is described. The compounds, 2-pyridylamino-N,N-bis(2-methylene- 4,6-dichlorophenol), H2[L1]; 2-pyridylamino-N,N-bis(2- methylene-4,6-difluorophenol), H2[L2]; dimethylaminoethylamino-N,N-bis(2-methylene-4,6-dichlorophenol), H 2[L3]; 2-tetrahydrofurfuryl-N,N-bis(2-methylene-4,6- dichlorophenol), H2[L4]; and methoxyethylamino-N,N-bis(2- methylene-4,6-dichlorophenol), H2[L5] were prepared in aqueous medium and obtained as white powders in good to excellent yield. Ten new iron(III) halide complexes supported by these tetradentate ligands are reported. Representative single crystal X-ray diffraction structures were obtained for H2[L1] and a water adduct of the iron(III) complex, aquachloro{2-pyridylamino-N,N-bis(2-methylene-4,6-dichlorophenolato)} iron(III), 2·H2O. The structure of the proligand H 2[L1] shows intramolecular hydrogen bonding. In the solid-state structure, the iron complex exhibits intermolecular hydrogen bonding between the water ligand and the phenolate oxygen of a neighbouring complex. The anhydrous complexes were studied for catalytic activity towards C-C cross-coupling of Grignard reagent nucleophiles with alkyl halide electrophiles.
- Reckling, Amy M.,Martin, Dana,Dawe, Louise N.,Decken, Andreas,Kozak, Christopher M.
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scheme or table
p. 787 - 794
(2011/03/20)
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- Nanoparticle-supported and magnetically recoverable nickel catalyst: A robust and economic hydrogenation and transfer hydrogenation protocol
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A magnetic nanoparticle-supported leach-proof Ni catalyst was readily prepared from inexpensive starting materials which catalyzes various hydrogenation and transfer hydrogenation reactions; high catalytic activity and ease of recovery using an external magnetic field are additional eco-friendly attributes of this catalytic system.
- Polshettiwar, Vivek,Baruwati, Babita,Varma, Rajender S.
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experimental part
p. 127 - 131
(2010/04/22)
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- Factors controlling photochemical cleavage of the energetically unfavorable Ph-Se bond of alkyl phenyl selenides
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(Chemical Equation Presented) Primary photochemical paths of alkyl phenyl selenides (1) were investigated, and an origin of large deviations in the chemical yields of products obtained by carbon radical reactions induced by photolysis of phenyl selenides was clarified. KrF excimer laser photolyses of n-pentyl phenyl selenide (1a) yielded 1-pentene (2a), n-pentane (3a), n-decane (4a), dipentyl selenide (5a), benzene (6), dipentyl diselenide (7a), and diphenyl diselenide (7) as major photoproducts, with compounds 2a, 3a, 4a, 5a, and 7 formed by pentyl-Se bond cleavage, and 5a, 6, and 7a by Ph-Se bond cleavage. The selectivity of the photoproducts revealed the occurrence of an unexpected amount of Ph-Se bond cleavage (35% in n-hexane at 248 nm) during photolysis. Solvent viscosity, wavelength of light, and the structure of alkyl substituents were the major factors that controlled Ph-Se bond cleavage. The ratio of Ph-Se bond cleavage decreased with increasing solvent viscosity and laser wavelength. The effect of alkyl substituents on the ratio of bond cleavages, Ph-Se/total C-Se, was investigated for five alkyl phenyl selenides; the ratio decreased in the order pentyl > 2-methylallyl > allyl > 1-ethylpropyl > tert-butyl groups. The contribution of Ph-Se bond cleavage is most probably the origin of the large deviations in the yields of radical reactions induced by photolyses of 1, which can be minimized by selecting appropriate solvents and wavelength of light.
- Ouchi, Akihiko,Liu, Suyou,Li, Zhong,Kumar, S. Ajaya,Suzuki, Toshiaki,Hyugano, Takeshi,Kitahara, Haruo
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p. 8700 - 8706
(2008/03/12)
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- Semivolatile and volatile compounds in combustion of polyethylene
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The evolution of semivolatile and volatile compounds in the combustion of polyethylene (PE) was studied at different operating conditions in a horizontal quartz reactor. Four combustion runs at 500 and 850°C with two different sample mass/air flow ratios and two pyrolytic runs at the same temperatures were carried out. Thermal behavior of different compounds was analyzed and the data obtained were compared with those of literature. It was observed that α,ω-olefins, α-olefins and n-paraffins were formed from the pyrolytic decomposition at low temperatures. On the other hand, oxygenated compounds such as aldehydes were also formed in the presence of oxygen. High yields were obtained of carbon oxides and light hydrocarbons, too. At high temperatures, the formation of polycyclic aromatic hydrocarbons (PAHs) took place. These compounds are harmful and their presence in the combustion processes is related with the evolution of pyrolytic puffs inside the combustion chamber with a poor mixture of semivolatile compounds evolved with oxygen. Altogether, the yields of more than 200 compounds were determined. The collection of the semivolatile compounds was carried out with XAD-2 adsorbent and were analyzed by GC-MS, whereas volatile compounds and gases were collected in a Tedlar bag and analyzed by GC with thermal conductivity and flame ionization detectors.
- Font, Rafael,Aracil, Ignacio,Fullana, Andrés,Conesa, Juan A.
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p. 615 - 627
(2007/10/03)
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- A highly selective arene hydrogenation catalyst that operates in ionic liquid
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The synthesis and structural characterization of [Ru(η6-p-cymene)(η2-TRIPHOS)Cl][PF6] is described. The complex is a highly active, homogeneous arene hydrogenation catalyst that is selective toward the hydrogenation of aromatic rings in preference to alkenes, as demonstrated by the hydrogenation of allylbenzene to allylcyclohexane. The catalyst operates in both dichloromethane and ionic liquids and undergoes no decomposition in the latter solvent. Copyright
- Boxwell, Clive J.,Dyson, Paul J.,Ellis, David J.,Welton, Thomas
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p. 9334 - 9335
(2007/10/03)
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- Strategies for protodesilylation of C-2 trialkylsilyl terminal alkenes
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The mild and high yielding protodesilylation of C-2 trialkylsilyl terminal alkenes can be effected via a hydroboration-Peterson elimination protocol or, in the case of the phenyldimethylsilyl analogues, a one pot procedure using t-BuOK-18-C-6-TBAF can be used. The Royal Society of Chemistry 2000.
- Anderson, James C.,Flaherty, Alice
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p. 3025 - 3027
(2007/10/03)
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- Cobalt-Catalyzed Carbon-Carbon Bond Formation via Radicals
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Catalytic amounts of cobalt complexes 2 and 3 are capable of generating alkyl radicals from the corresponding bromides under mild reaction conditions, allowing the selective preparation of either saturated or unsaturated radical cyclization products.
- Giese, Bernd,Erdmann, Peter,Goebel, Thomas,Springer, Ronald
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p. 4545 - 4548
(2007/10/02)
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- A SIMPLE PROCEDURE FOR THE SYNTHESIS OF THREE-CARBON HOMOLOGATED BORONATE ESTERS AND TERMINAL ALKENES VIA NUCLEOPHILIC DISPLACEMENT IN α-HALOALLYLBORONATE ESTER
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The transfer reactions of α-haloallylboronate ester 1 with representative organolithium and Grignard reagents provide α-alkyl- or α-aryl-substituted allylboronate esters, readily converted into three-carbon homologated boronate esters and terminal alkenes.
- Brown, Herbert C.,Rangaishenvi, Milind V.
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p. 7115 - 7118
(2007/10/02)
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- Approximate rate constants for the addition of alkyl radicals to allylstannanes
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Rate constants for the addition of alkyl radicals to allylstannanes lie in the range of 104-105 M-1 s-1 at 50-80°C.
- Curran,Van Elburg
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p. 2861 - 2864
(2007/10/02)
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- Allylic and Propargylic Substitution Reactions Involving Radicals Generated from Alkylmercury Halides
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Addition of alkyl radicals to allyl or propargyl derivatives forms adduct radicals which can undergo β-elimination with substituents such as halogen, PhS, PhSO2, Bu3Sn, or HgCl to form the alkyl-substituted propene or allene and an eliminated radical which regenerates the alkyl radical by displacement from an alkylmercurial.With β-oxy substituents, such as O2CR, OP(O)(OEt)2, O3SAr, OPh, OSiMe3, or OH, the adduct radicals can displace the alkyl radical from the alkylmercurial to yield β-substituted alkylmercurials which spontaneously, or in the presence of nucleophiles, undergo an elimination reaction to yield the alkene or allene.Relative reactivities toward tert-butyl radical attack, such as k(allyl chloride)/k(propargyl chloride) = ca. 10, have been determined.A similar relative reactivity is observed in reaction with (t-Bu)2CuLi implicating attack by free tert-butyl radicals.With allyl or propargyl iodide, radical attack leads to iodine atom abstraction.Reaction of propargyl iodide with t-BuHgCl/hν, (t-Bu)2CuLi, or (t-Bu)3ZnLi leads to a mixture of hydrocarbons in which tert-butylallene is present in only trace amounts.Benzene is an important reaction product which seems to be formed via the cyclodimerization of two "propargyl" (C3H3.) radicals.
- Russell, Glen A.,Ngoviwatchai, Preecha,Wu, Yuh Wern
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p. 4921 - 4927
(2007/10/02)
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- SYNTHESIS OF CYCLOHEXYLALIPHATIC ACIDS AND THEIR PHARMACOLOGICAL PROPERTIES
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A series of substituted cyclohexylacetic acids I has been obtained by hydrogenation of the unsaturated analogues II and III.Esters of these analogues were prepared by the Horner-Wittig reaction of the corresponding cyclohexanones IV and/or 2-cyclohexenones V with triethyl phosphonoacetate.These esters were obtained in two isomeric forms (Z and E), differing in the double bond in the exo-position.The derivatives with a substituent in the 2-position exhibited a partial shift of the double bond to the cyclohexane ring; this shift was especially marked in the 2-phenyl derivative.With the acids I-III, activation of fibrinolysis was assessed by the hanging clot method; the anti-inflammatory effect was assessed by inhibition of two experimental model inflammations.The regression equation relating fibrinolytic capacity to lipophilicity was a quadratic one, the logarithm of optimum lipophilicity being log Popt = 5.55.A qualitative assessment of the anti-inflammatory effect in relation to lipophilicity suggests that log Popt is probably higher than with arylaliphatic acids.These acids seem to have an active site different from that of the acids I-III.
- Kuchar, Miroslav,Brunova, Bohumila,Grimova, Jaroslava,Vanecek, Stanislav,Holubek, Jiri
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p. 2896 - 2908
(2007/10/02)
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- Decomposition et proprietes electrophiles des carbenoides monohalogenes non fonctionnels
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Geminal substitution of a carbon atom by a halogen atom and a lithium atom gives rise to electrophilic properties and great instability to the corresponding α-monohalogenoalkyllithium.From NMR data, it appears that the functional carbon atom exhibits an electron deficiency in connection with an intramolecular halogen-lithium coordination.This description is in agreement with the structure proposed for LiCH2F on the basis of "ab initio" calculations.Electronic and steric effects of the other substituents of the functional carbon atom and the influence of the reaction medium (basicity of solvents, Lewis acidity of associated salts) on the variation of electrophilic and nucleophilic behaviour and stability of carbenoids (mono, di, trihalogeno) can be rationalized on the basis of this metallocarbenium halogenide structure.
- Villieras, J.,Rambaud, M.,Kirschleger, B.,Tarhouni, R.
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p. 837 - 843
(2007/10/02)
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- ONE ELECTRON C-C BOND FORMING REACTIONS VIA ALLYLSTANNANES: SCOPE AND LIMITATIONS
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Free radical (or "one-electron") methodology for carbon-carbon bond forming reactions using allylstannanes is described in detail.Such reactions have the advantages of tolerating quite complex functionality in the substrate and of being nearly stoichiometric in reagents, and not requiring extensive experimentation for application to new substrates.
- Keck, Gary E.,Enholm, Eric J.,Yates, John B.,Wiley, Michael R.
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p. 4079 - 4094
(2007/10/02)
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- Reactions of Cyclanyl Radicals in the Gas Phase. II. Cyclohexyl Radicals from Mixtures of Azomethane and Cyclohexane
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Cyclohexane-azomethane mixtures in argon as diluent were converted by temperatures between 400 and 480 deg C in a stirred flow system.All products were analytically determined in a comprehesive way.In this way not only isomeric C6H11-radicals, which were already known from former investigations, but also hitherto unknown C6H11-radicals, especially the 3-methylcyclopentyl radical, could be detected as a recombination product with methyl radicals or as the corresponding olefinic compounds.From the results the stationary concentrations of important radical species were estimated and mechanistic consequences discussed.
- Ondruschka, B.,Zimmermann, G.,Anders, G.
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p. 853 - 862
(2007/10/02)
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