- Ruthenium-catalysed oxidative coupling of vinyl derivatives and application in tandem hydrogenation
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The first ruthenium-catalyzed oxidative homo- and cross-coupling of exclusive vinyl derivatives giving highly valued 1,3-diene building blocks is reported. The catalytic system is based on readily available reagents and it mainly delivers the E,E isomer. This methodology also enables the synthesis of adipic acid ester derivatives in a one-pot fashion after in situ ruthenium-catalyzed hydrogenation.
- Abuhafez, Naba,Bruneau, Christian,Gramage-Doria, Rafael,Kamaraj, Raghu,Ruffin, Hervé
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p. 5772 - 5776
(2021/09/10)
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- Sequential Transformation of Terminal Alkynes to 1,3-Dienes by a Cooperative Cobalt Pyridonate Catalyst
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We describe the cobalt(II) catalyst 1 bearing a phosphinopyridonate ligand for sequential transformation of aryl terminal alkynes to (E,Z)-1,3-dienes with excellent stereoselectivity. By cooperative metal-ligand reactivity, 1 reacts readily with the termi
- Zhuang, Xuewen,Chen, Jia-Yi,Yang, Zhuoyi,Jia, Mengjing,Wu, Chengjuan,Liao, Rong-Zhen,Tung, Chen-Ho,Wang, Wenguang
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supporting information
p. 3752 - 3759
(2019/11/13)
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- Carbon-carbon bond forming reactions via Pd-catalyzed detellurative homocoupling of diorganyl tellurides
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A simple and highly efficient method for the constructions of Csp-Csp, Csp2-Csp2 and Csp3-Csp3 bonds is reported. The symmetrical diaryl tellurides undergo detellurative homocouplings to afford symmetrical biaryl products. The reactions are carried out at ambient temperature using PdCl2 as a catalyst in the presence of Ag2O and Na2CO3. Similarly, the detellurative homocouplings of dibenzyl telluride and bis(phenylethynyl)telluride give bibenzyl and the conjugated diyne, respectively.
- Zhang, Shaozhong,Kolluru, Lalitha,Vedula, Souseelya K.,Whippie, Drew,Jin, Jin
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supporting information
p. 3594 - 3597
(2017/08/23)
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- Copper(I)-catalyzed stereoselective hydrogenation of 1,3-diynes and enynes
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A stereoselective hydrogenation of 1,3-diynes with an air-stable copper(I)/N-heterocyclic carbene complex, [IPrCuOH], has been developed. The corresponding products, 1,3-dienes, are obtained in a stereoselective manner depending on their substitution pattern: Diaryl-diynes yield E,E-1,3-dienes, whereas dialkyl-diynes are converted to the corresponding Z,Z-1,3-dienes. Hydrogenation and deuteration experiments with enynes indicate that these are competent reaction intermediates in the hydrogenation of diynes.
- Thiel, Niklas O.,Kemper, Sebastian,Teichert, Johannes F.
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p. 5023 - 5028
(2017/07/27)
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- Catalytic Dehydrogenative C-C Coupling by a Pincer-Ligated Iridium Complex
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The pincer-iridium fragment (iPrPCP)Ir (RPCP = ?3-2,6-C6H3(CH2PR2)2) has been found to catalyze the dehydrogenative coupling of vinyl arenes to afford predominantly (E,E)-1,4-diaryl-1,3-butadienes. The eliminated hydrogen can undergo addition to another molecule of vinyl arene, resulting in an overall disproportionation reaction with 1 equiv of ethyl arene formed for each equivalent of diarylbutadiene produced. Alternatively, sacrificial hydrogen acceptors (e.g., tert-butylethylene) can be added to the solution for this purpose. Diarylbutadienes are isolated in moderate to good yields, up to ca. 90% based on the disproportionation reaction. The results of DFT calculations and experiments with substituted styrenes indicate that the coupling proceeds via double C-H addition of a styrene molecule, at β-vinyl and ortho-aryl positions, to give an iridium(III) metalloindene intermediate; this intermediate then adds a β-vinyl C-H bond of a second styrene molecule before reductively eliminating product. Several metalloindene complexes have been isolated and crystallographically characterized. In accord with the proposed mechanism, substitution at the ortho-aryl positions of the styrene precludes dehydrogenative homocoupling. In the case of 2,4,6-trimethylstyrene, dehydrogenative coupling of β-vinyl and ortho-methyl C-H bonds affords dimethylindene, demonstrating that the dehydrogenative coupling is not limited to C(sp2)-H bonds.
- Wilklow-Marnell, Miles,Li, Bo,Zhou, Tian,Krogh-Jespersen, Karsten,Brennessel, William W.,Emge, Thomas J.,Goldman, Alan S.,Jones, William D.
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supporting information
p. 8977 - 8989
(2017/07/12)
-
- Cyclobutene vs 1,3-Diene Formation in the Gold-Catalyzed Reaction of Alkynes with Alkenes: The Complete Mechanistic Picture
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The intermolecular gold(I)-catalyzed reaction between arylalkynes and alkenes leads to cyclobutenes by a [2 + 2] cycloaddition, which takes place stepwise, first by formation of cyclopropyl gold(I) carbenes, followed by a ring expansion. However, 1,3-butadienes are also formed in the case of ortho-substituted arylalkynes by a metathesis-type process. The corresponding reaction of alkenes with aryl-1,3-butadiynes, ethynylogous to arylalkynes, leads exclusively to cyclobutenes. A comprehensive mechanism for the gold(I)-catalyzed reaction of alkynes with alkenes is proposed on the basis of density functional theory calculations, which shows that the two pathways leading to cyclobutenes or dienes are very close in energy. The key intermediates are cyclopropyl gold(I) carbenes, which have been independently generated by retro-Buchner reaction from stereodefined 1a,7b-dihydro-1H-cyclopropa[a]naphthalenes.
- De Orbe, M. Elena,Amenós, Laura,Kirillova, Mariia S.,Wang, Yahui,López-Carrillo, Verónica,Maseras, Feliu,Echavarren, Antonio M.
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supporting information
p. 10302 - 10311
(2017/08/09)
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- Unsupported Nanoporous Gold Catalyst for Chemoselective Hydrogenation Reactions under Low Pressure: Effect of Residual Silver on the Reaction
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For the first time, H-H dissociation on an unsupported nanoporous gold (AuNPore) surface is reported for chemoselective hydrogenation of C=C, C=C, C=N, and C=O bonds under mild conditions (8 atm H2 pressure, 90 °C). Silver doping in AuNPore, which was inevitable for its preparation through a process of dealloying of Au-Ag alloy, exhibited a remarkable difference in catalytic activity between two catalysts, Au>99Ag1NPore and Au90Ag10NPore.The former was more active and the latter less active in H2 hydrogenation, while the reverse tendency was observed for O2 oxidation. This marked contrast between H2 reduction and O2 oxidation is discussed. Further, Au>99Ag1NPore showed a high chemoselectivity toward reduction of terminal alkynes in the presence of internal alkynes which was not achieved using supported gold nanoparticle catalysts and other previously known methods. Reductive amination, which has great significance in synthesis of amines due to its atom-economical nature, was also realized using Au>99Ag1NPore, and the Au>99Ag1NPore/H2 system showed a preference for the reduction of aldehydes in the presence of imines. In addition to this high chemoselectivity, easy recovery and high reusability of AuNPore make it a promising heterogeneous catalyst for hydrogenation reactions.
- Takale, Balaram S.,Feng, Xiujuan,Lu, Ye,Bao, Ming,Jin, Tienan,Minato, Taketoshi,Yamamoto, Yoshinori
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supporting information
p. 10356 - 10364
(2016/08/31)
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- Stereoselective alkyne semihydrogenations with an air-stable copper(i) catalyst
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An air-stable and preactivated copper(i) hydroxide/N-heteroyclic carbene (NHC) complex for alkyne semihydrogenations is reported. Next to an enhanced practicability of the process, the resulting alkenes are obtained with high Z-selectivities and no overreduction to the corresponding alkanes.
- Thiel, Niklas O.,Teichert, Johannes F.
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p. 10660 - 10666
(2016/11/30)
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- Salt-Free Reduction of Nonprecious Transition-Metal Compounds: Generation of Amorphous Ni Nanoparticles for Catalytic C-C Bond Formation
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A salt-free procedure for the generation of a wide variety of metal(0) particles, including Fe, Co, Ni, and Cu, was achieved using 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (1), which reduced the corresponding metal precursors under mild conditions. Notably, Ni particles formed in situ from the treatment of Ni(acac)2 (acac=acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C-C bond-forming reactions of aryl halides in the presence of excess amounts of 1. By examination of high-magnification transmission electron microscopy images and electron diffraction patterns, we concluded that amorphous Ni nanoparticles (Ni aNPs) were essential for the high catalytic activity.
- Yurino, Taiga,Ueda, Yohei,Shimizu, Yoshiki,Tanaka, Shinji,Nishiyama, Haruka,Tsurugi, Hayato,Sato, Kazuhiko,Mashima, Kazushi
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supporting information
p. 14437 - 14441
(2016/01/25)
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- Quinonediimine-induced oxidative coupling of organomagnesium reagents
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N,N′-Diphenyl-p-benzoquinonediimine, a redox-active unit of polyaniline, efficiently induced the oxidative homocoupling of various aryl- and vinylmagnesium reagents in suppressing the side reactions, such as 1,2- or 1,4-addition reaction. Copyright
- Amaya, Toru,Suzuki, Riyo,Hirao, Toshikazu
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p. 653 - 656
(2014/01/23)
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- METHODS FOR PHOSPHINE OXIDE REDUCTION IN CATALYTIC WITTIG REACTIONS
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A method for increasing the rate of phosphine oxide reduction, preferably during a Wittig reaction comprising use of an acid additive is provided. A room temperature catalytic Wittig reaction (CWR) the rate of reduction of the phosphine oxide is increased due to the addition of the acid additive is described. Furthermore, the extension of the CWR to semi-stabilized and non-stabilized ylides has been accomplished by utilization of a masked base and/or ylide-tuning.
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Page/Page column 58; 59; 62
(2014/09/29)
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- Catalytic wittig reactions of semi- and nonstabilized ylides enabled by ylide tuning
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The first examples of catalytic Wittig reactions with semistabilized and nonstabilized ylides are reported. These reactions were enabled by utilization of a masked base, sodium tert-butyl carbonate, and/or ylide tuning. The acidity of the ylide-forming proton was tuned by varying the electron density at the phosphorus center in the precatalyst, thus facilitating the use of relatively mild bases. Steric modification of the precatalyst structure resulted in significant enhancement of E selectivity up to >95:5, E/Z. Time for a tune up: Catalytic Wittig reactions with semi- and nonstabilized ylides were enabled by use of a masked base (NaOCO2tBu) and/or ylide tuning. The acidity of the ylide-forming proton was tuned by varying the electron density at the P center in the precatalyst, thus facilitating the use of relatively mild bases. Steric modification of the precatalyst structure resulted in significant enhancement of E selectivity.
- Coyle, Emma E.,Doonan, Bryan J.,Holohan, Andrew J.,Walsh, Killian A.,Lavigne, Florie,Krenske, Elizabeth H.,O'Brien, Christopher J.
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supporting information
p. 12907 - 12911
(2016/02/18)
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- Regio- and stereoselective hydrosilylation of 1,3-enynes catalyzed by palladium
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In the presence of Pd(0) and a phosphine, hydrosilylation of 1,3-enynes with Me2SiHCl proceeds to yield dienylsilanes with the silicon function added to the internal alkyne carbon atom and with (E)-configuration of newly formed olefinic bond. The silanols isolated after hydrolysis of the primarily obtained products serve as precursors to conjugated dienes with different substitution patterns.
- Zhou, Hui,Moberg, Christina
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supporting information
p. 1444 - 1447
(2013/06/27)
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- Diastereoselective liquid assisted grinding: 'Cracking' functional resins to advance chromatography-free synthesis
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As regulations that restrict the use of organic solvents become more stringent, ball milling remains an attractive substitute for traditional organic synthesis. However, the mechanochemistry community does not have a purification pathway to complement the solvent-free, ball milling process. Functional resins have proven to be powerful synthetic tools that simplify purification, but traditional handling of these resins restricts their utility, as hazardous organic solvents are needed to swell the resin. Ball milling the functional resin exposes the functional groups as a function of surface area. This report details the use of ball milling and functional resins to perform an environmentally attractive version of the Wittig reaction.
- Shearouse, William C.,MacK, James
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p. 2771 - 2775,5
(2020/09/14)
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- Iron-catalyzed chemo- and stereoselective hydromagnesiation of diarylalkynes and diynes
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Diarylalkynes are chemo- and stereoselectively hydromagnesiated in high yields at room temperature with an iron species generated in situ from FeCl 2and EtMgBr. Functional groups such as bromide, iodide, amine, phenoxide, and alkene are well tolerated. Under similar conditions, diynes are chemo-, regio-, and stereoselectively hydromagnesiated. The resulting alkenylmagnesium compounds are a platform for further functionalization as a one-pot reaction.
- Ilies, Laurean,Yoshida, Takumi,Nakamura, Eiichi
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supporting information
p. 16951 - 16954,4
(2020/09/02)
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- An efficient, overall [4+1] cycloadditon of 1,3-dienes and nitrene precursors
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Intermolecular cycloadditions of conjugated dienes and nitrene precursors usually produce aziridines. A generally useful method was lacking to directly provide the [4+1] cycloadducts, 3-pyrrolines. We have realized this transformation by using an uniquely active catalyst, copper(II) 1,1,1,5,5,5-hexafluoroacetylacetonate ([Cu(hfacac)2]). The method is applicable to a wide array of dienes with good yields. When 1,4-disubsituted dienes are used as substrates, good-to-excellent cis or trans selectivity can be obtained. Interestingly, the cis or trans preference depends on the nature of the substituents, rather than diene geometry. Mechanistic studies reveal that the [4+1] cycloaddition proceeds through diene aziridination and subsequent ring expansion. Among common copper catalysts, only [Cu(hfacac)2] can efficiently catalyze both steps, which explains the unique efficiency of the catalyst.
- Wu, Qiong,Hu, Jian,Ren, Xinfeng,Zhou, Jianrong
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p. 11553 - 11558
(2011/11/29)
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- Medium effects on the direct cis-trans photoisomerization of 1,4-diphenyl-1,3-butadiene in solution
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Quantum yields for the photoisomerization of trans,trans-1,4-diphenyl-1,3- butadiene (tt-DPB), determined in benzene, cyclohexane, methylcyclohexane, hexane, and perfluorohexane, confirm the low values reported earlier for benzene and cyclohexane and reveal even lower values in the last two solvents. In contrast to trans-stilbene (t-St), fluorescence and torsional relaxation leading to photoisomerization do not account exclusively for S1tt-DPB decay. Competing radiationless singlet excited-state decay pathways exist in tt-DPB, which do not lead to photoisomerization and may not involve large-amplitude torsional motions. Our results invalidate analyses of tt-DPB fluorescence quantum yields and lifetimes that assign all radiationless decay to the isomerization channel. Gas-phase chromatography analysis of tt-DPB photoisomerization in hexane shows the reaction to be concentration-independent and reveals, for the first time, a significant, two-bond photoisomerization pathway, βtt→tc = 0.092 and βtt→cc = 0.020. The dominant one-bond-twist (OBT) process is accompanied by a bicycle pedal (BP) process that accounts for almost 20% of tt-DPB photoisomerization. The OBT tt-DPB photoisomerization quantum yield is largest in benzene (Bz) and smallest in perfluorohexane (PFH). Contrary to expectations, reduction in medium friction in PFH is accompanied by a decrease in βtt→tc. The 11Bu/21Ag order and energy gap appear to control the contribution of torsional relaxation to radiationless decay. Lowering the 11Bu energy as in Bz favors photoisomerization. Reversal of the 11Bu/2 1Ag order in PFH is accompanied by short τf and small βf and βtt→tc values that suggest the presence of competing 21Ag → 1 1Ag relaxation paths that are unproductive with respect to photoisomerization. We conclude that the Birks extension to diphenylpolyenes of the Orlandi-Siebrand cis-trans photoisomerization mechanism is not valid. Photoisomerization appears to occur in the 1IBu state, and we argue that this applies to t-St as well.
- Saltiel, Jack,Krishna, Talapragada R. S.,Laohhasurayotin, Kritapas,Ren, Yanjun,Phipps, Kathleen,Davis, Paul H.,Yee, W. Atom
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scheme or table
p. 2120 - 2129
(2011/05/16)
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- Photosensitized oxidation of alkenes with dendrimers as microreactors: Controllable selectivity between energy and electron transfer pathway
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Carboxylic acid terminated poly(aryl ether) dendrimers were used as microreactors to conduct the photooxidation of trans-stilbene and trans,trans-1,4-diphenyl-1,3-butadiene (DPB) sensitized by 9,10- dicyanoanthracene (DCA) in aqueous media. The photooxidation pathways can be successfully controlled by encapsulating the substrate and sensitizer molecules in the same or different sets of dendrimers. The singlet oxygen can transfer from one dendrimer to another. After the photoreaction, products could be more easily extracted from a dendrimer than from a micelle or a vesicle, and the dendrimer can be simply recovered by neutralization of the solution and reused. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
- Yuan, Zhao,Zheng, Shaojun,Zeng, Yi,Chen, Jinping,Han, Yongbin,Li, Yingying,Le, Yi
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experimental part
p. 718 - 722
(2010/06/19)
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- ZWITTERIONIC PHOSPHONIUM SALTS
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A zwitterionic phosphonium salt of Formula I: wherein n is 0 or 1; R is H or SO3-; R' is selected from the group consisting of C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C3-C10 cycloalkyl, phenyl, substituted phenyl, benzyl and C1-C10 alkoxycarbonyl; R' is CX3 when n is O; and X is selected from the group consisting of F, Cl, Br and I. The zwitterionic phosphonium salts are useful reagents for the preparation of alkenes and acetals from the corresponding aldehyde.
- -
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Page/Page column 15; 25
(2010/04/03)
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- A highly tunable stereoselective olefination of semistabilized triphenylphosphonium ylides with N -Sulfonyl imines
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The Wittig reaction involving direct olefination of triphenylphosphonium ylides (Ph3PCHR) with aldehydes is arguably the most often used method for alkene synthesis, but in general it yields mixtures of Z- and E-alkenes for semistabilized triphenylphosphonium ylides (R = aryl or vinyl). We have developed a simple and efficient protocol to improve the stereoselectivity significantly by replacing the aldehydes used in the Wittig reaction with N-sulfonyl imines, which possess distinct electronic and steric properties relative to aldehydes. A broad range of aromatic, α,β-unsaturated, and aliphatic imines bearing appropriate N-sulfonyl groups smoothly undergo olefination reaction with various benzylidenetriphenylphosphoranes or allylidenetriphenylphosphoranes under mild reaction conditions to afford an array of both Z- and E-isomers of conjugated alkenes in good to excellent yields and with greater than 99:1 stereoselectivity. Moreover, this tunable protocol has been successfully applied to the highly stereoselective synthesis of two anticancer agents, DMU-212 and its Z-isomer.
- Dong, De-Jun,Li, Hai-Hua,Tian, Shi-Kai
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supporting information; experimental part
p. 5018 - 5020
(2010/06/13)
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- Synthesis of stilbenes promoted by the mixture of zinc and iron powder
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Stilbenes have been synthesised by a one-pot reaction of aldehydes with benzyl bromide. The reaction was promoted by both triphenylphosphine and the mixture of zinc and iron together in sealed tube. The yields ranged from moderate to excellent.
- Zhanga, Zhiying,Xieb, Yuanyuan,Yua, Xiaochun
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experimental part
p. 140 - 142
(2009/10/15)
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- A highly selective catalytic system for the cross-coupling of (E)-Styryl Bromide with Benzeneboronic acid: Application to the synthesisof all-trans poly(arylenevinylene)s
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Ahighlyselective system for palladium-catalyzed polycondensation of (E, E)-1,4-bis(2-bromoethenyl)benzene ((E, E)-1)with 2,5-dioctyloxybenzene-1,4- diboronicacid(2a)togive all-trans poly[(p-phenylenevinylene)-alt-(2,5- dioctyloxy-1,4-phenylenevinylene)] (all-trans 3) has been investigated using (E)-styryl bromide ((E)-4) and 2,5-dioctyl- oxybenzeneboronicacid(5a) as model compounds of and 2a, respectively. The reaction of (E)-4 and 5a in toluene in the presence of Pd(PPh3)4 catalyst and aqueous K 2CO3 base affords considerable amounts of homocoupling products (i.e., 1,4-diphenylbutadiene (13%) and 2,2',5,5'-tetraoctyloxybiphenyl (22%)), together with (E)-2,5-dioctyl- oxystilbene ((E)-6a) as the cross-coupling product (30%). The use of aqueous NaOH as a strong base and Bu4NBr as a phase-transfer catalyst notably reduces the homocoupling products, and the use of Pd(PBut3)2 instead of Pd(PPh3)4 results inalmost perfect selectivity of the cross-coupling product (E)-6a. Under optimized catalytic conditions, the desired all- trans 3 has been successfully prepared without notabledefects in the polymer chain.
- Wakioka, Masayuki,Mutoh, Yuichiro,Takita, Ryo,Ozawa, Fumiyuki
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experimental part
p. 1292 - 1298
(2010/01/30)
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- Palladium-nanoparticle-catalysed ullmann reactions in ionic liquids with aldehydes as the reductants: Scope and mechanism
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An efficient Ullmann-type reductive homocoupling of aryl, vinyl and heteroaryl halides can be promoted by an aldehyde in tetraalkylammonium ionic liquids under very mild reaction conditions. This simple procedure generates symmetrical biaryls under relatively mild conditions. The ionic liquid is crucial for this process because it behaves simultaneously as a base, ligand and reaction medium. The role of the aldehyde is also discussed and a general mechanism for this unusual reaction is proposed. These results open the way to a new efficient method of Pd-catalysed dehydrogenation of carbonyl compounds.
- Calo, Vincenzo,Nacci, Angelo,Monopoli, Antonio,Cotugno, Pietro
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experimental part
p. 1272 - 1279
(2009/08/14)
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- Aqueous sodium hydroxide promoted cross-coupling reactions of alkenyltrialkoxysilanes under ligand-free conditions
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(Chemical Equation Presented) Fluoride-free cross-coupling reactions of alkenyltrialkoxysilanes with aryl iodides, bromides, and chlorides are performed on water using sodium hydroxide as activator at 120 °C under normal or microwave heating. This process occurs in the presence of Pd(OAc)2 or 4-hydroxyacetophenone oxime-derived palladacycle 1 as precatalysts under ligand-free conditions with low Pd loadings (0.01-1 mol %) and using tetra-n-butylammonium bromide as additive. Different commercially available vinylalkoxylsilanes can be cross-coupled under these reaction conditions to the corresponding styrenes, the best substrates being vinyltrimethoxy- or vinyltriethoxysilane. Alkenyltriethoxysilanes, prepared by Wilkinson-catalyzed hydrosilylation of alkynes with triethoxysilane, are stereospecifically arylated with aryl and vinyl halides under microwave irradiation in moderate to high β/α regioselectivity affording unsymmetrical stilbenes, alkenylbenzenes, and conjugate dienes, respectively. This simple procedure allows the palladium recycling from the aqueous phase during three runs by extractive separation of the products, which contain very low levels of Pd (21-27.5 ppm for an aryl iodide and up to 76 ppm for a bromide).
- Alacid, Emilio,Najera, Carmen
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p. 2315 - 2322
(2008/09/19)
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- Stereoselective hydroxycarbonylation of vinyl bromides to α,β-unsaturated carboxylic acids in the ionic liquid [BMIM]PF 6
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(E/Z)-Isomers containing vinyl bromides were stereoselectively carbonylated to the corresponding (E)-α,β-ethylenic carboxylic acids in the ionic liquid [BMIM]PF6. Vinyl dibromides also underwent hydroxycarbonylation to give monoacids. The products are pure by proton NMR spectroscopic determination without purification by silica gel column chromatograghy or recrystallization.
- Zhao, Xiaodan,Alper, Howard,Yu, Zhengkun
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p. 3988 - 3990
(2007/10/03)
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- Photoisomerization of cis,cis-1,4-diphenyl-1,3-butadiene in glassy media at 77 K: The bicycle-pedal mechanism
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The cis-trans photoisomerization of cis,cis-1,4-diphenyl-1,3-butadiene in a soft isopentane glass at 77 K gives significant two-bond photoisomerization in contrast to solution and hard glassy media where only one-bond photoisomerization takes place. The Royal Society of Chemistry 2006.
- Saltiel, Jack,Krishna, Tallapragada S. R.,Turek, Andrzej M.,Clark, Ronald J.
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p. 1506 - 1508
(2008/02/10)
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- The first fluoride-free Hiyama reaction of vinylsiloxanes promoted by sodium hydroxide in water
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The first cross-coupling reaction between vinylalkoxysilanes and aryl bromides or chlorides promoted by aqueous sodium hydroxide under fluoride-free conditions to provide styrenes is reported. The reaction is catalyzed by palladium(II) acetate or a 4-hydroxyacetophenone oxime-derived palladacycle either under thermal or microwave heating at 120°C with low catalyst loading (0.01-1 mol% of palladium) in the presence of tetra-n-butylammonium bromide (TBAB) as additive in air. In the case of styryltriethoxysilane, the coupling with aryl or vinyl bromides takes place stereospecifically to give the corresponding stilbenes or dienes, respectively. These mild and simple reaction conditions prevent undesirable polymerization of the products.
- Alacid, Emilio,Najera, Carmen
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p. 2085 - 2091
(2007/10/03)
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- Palladium-catalyzed cross-coupling of vinylic tellurides and potassium vinyltrifluoroborate salt: synthesis of 1,3-dienes
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Here we report an ultrasound-assisted synthesis of stereodefined 1,3-dienes by Suzuki-Miyaura cross-coupling reactions of vinylic tellurides and potassium β-styryl trifluoroborate salt.
- Cella, Rodrigo,Orf?o, Aline T.G.,Stefani, Hélio A.
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p. 5075 - 5078
(2007/10/03)
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- Palladium-catalyzed inter- and intramolecular coupling reactions of aryl and vinyl halides mediated by indium
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(Chemical Equation Presented) Treatment of aryl and vinyl halides with 50 mol % of 100 mesh indium, 2.5 mol % of Pd-C, and 1.5 equiv of LiCl under mild conditions (DMF, 100°C, 1-3 h) could produce coupling products efficiently in good to excellent yields in which the Csp2-Csp2 bond was formed. This reagent worked equally well with both intermolecular and intramolecular coupling reactions, producing a variety of biaryls, 1,3-dienes, and cyclic compounds.
- Phil, Ho Lee,Seomoon, Dong,Lee, Kooyeon
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p. 343 - 345
(2007/10/03)
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- Divergent oxidative rearrangements in solution and in a zeolite: Distal vs proximal bond cleavage of methylenecyclopropanes
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Irradiation of 9,10-dicyanoanthracene (DCA) or p-chloranil in the presence of E-1-benzylidene-2-phenylcyclopropane (E-5) in CH2CI2 causes E-5 to undergo methylenecyclopropane rearrangement. An adduct, Z-7, between DCA and 5 firmly supports the involvement of a bifunctional trimethylenemethane radical cation. In contrast, incorporation of E-5 into HZSM-5 produces trans,trans-1,4-diphenyl-1,3-butadiene radical cation sequestered in the HZSM-5 interior, tt-8·+ @ HZSM-5, identified by ESR and diffuse reflectance spectroscopy. In addition, low yields of tt-8, its cis, trans-isomer (ct-8), and 1-phenyl-1,2-dihydronaphthalene (9) were isolated from the supernatant solution. The sharp contrast between the photoinduced electrontransfer reaction with photosensitizers in solution and the spontaneous reaction with redox-active acidic zeolite offers the prospect of further zeolite-induced regiodivergent reactions in a range of additional substrates.
- Ikeda, Hiroshi,Nomura, Tsuyoshi,Akiyama, Kimio,Oshima, Mitsuhiro,Roth, Heinz D.,Tero-Kubota, Shozo,Miyashi, Tsutomu
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p. 14497 - 14504
(2007/10/03)
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- Generation of phosphoranes derived from phosphites. A new class of phosphorus ylides leading to high E selectivity with semi-stabilizing groups in Wittig Olefinations
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Tosylhydrazones derived from aryl aldehydes react with t-BuOK, ClFeTPP, (MeO)3P, and aldehydes to furnish olefins with high E selectivity. These reactions occur through a Wittig-type pathway via the corresponding diazo compounds, metal carbenes and phosphorous ylides, with the water-soluble trimethyl phosphate as the byproduct. Similar reactions can also be performed using ethyl diazoacetate; however, high E selectivity was only observed in the presence of LiBr. In this case, the reaction is believed to occur via the phosphonate anion, formed through an Arbuzov reaction. Thus this olefination reaction occurs through a Horner-Wadsworth-Emmons (HWE) reaction but the phosphonate anion is generated under completely base-free conditions. Copyright
- Aggarwal, Varinder K.,Fulton, J. Robin,Sheldon, Chris G.,De Vicente, Javier
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p. 6034 - 6035
(2007/10/03)
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- Nickel-catalyzed electrochemical couplings of vinyl halides: Synthetic and stereochemical aspects
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Homo- and cross-coupling involving alkenyl halides have been performed efficiently using an electroassisted nickel-complex catalysis. Valuable product such as conjugated dienes, β,γ- or γ,δunsaturated esters, ketones, or nitriles, as well as alkenylated aryl compounds are thus prepared with high yields and high stereoselectivity. Partial isomerization is only observed in a few cases, when the alkenyl halide is involved in a late step of the catalytic cycle. This is the case in the preparation of (Z,Z)-1,3-diene.
- Cannes,Condon,Durandetti,Perichon,Nedelec
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p. 4575 - 4583
(2007/10/03)
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- Oxovanadium(V)-induced oxidation of alkenylzirconocenes for facile inter- and intramolecular coupling
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The oxidation reaction of (E)-1-alkenylchlorozirconocenes with an oxovanadium(V) compound at room temperature led to intermolecular homocoupling, giving the corresponding (E,E)-dienes stereoselectively. (E)-1-Alkenyl-1-alkynylzirconocenes underwent the oxovanadium(V)-induced intramolecular cross-coupling of organic substituents on zirconium, leading to the stereoselective formation of the (E)-enynes.
- Ishikawa, Takuji,Ogawa, Akiya,Hirao, Toshikazu
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- Trans-Selective Olefination of Carbonyl Compounds by Low-Valent Titanium-Mediated Dehydroxybenzotriazolylation
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Lithiation with n-butyllithium of a variety of benzotriazole derivatives 1a-f and 5a-d, all containing a proton α to the benzotriazolyl moiety, gave anions which underwent addition to aliphatic, aromatic, and α,β-unsaturated aldehydes and cyclic and acyclic ketones. The resultant N-(β-hydroxyalkyl)benzotriazole derivatives 3a-m, 6a-g, 9a-d, and 10a were dehydroxybenzotriazolylated when treated with low-valent titanium to give alkenes 4a-m, dienes 7a- j, and triene 11a, with selectivity for the trans isomers without separation of diastereoisomeric intermediates. This method offers an alternative to the three most frequently used methods for the formation of alkenes from carbonyl compounds-the Wittig, Peterson, and Julia reactions-especially in the formation of tri- and tetrasubstituted alkenes.
- Katritzky, Alan R.,Cheng, Dai,Henderson, Scott A.,Li, Jianqing
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p. 6704 - 6709
(2007/10/03)
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- Polymer-bound palladium-catalyzed cross-coupling of organoboron compounds with organic halides and organic triflates
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The polymer-bound palladium-catalyzed cross-coupling reaction of electrophiles (i.e., halides and triflates) with oganoboron compounds to form carbon-carbon bonds was achieved at mild conditions with very high activity in the Suzuki coupling reaction. The polymeric catalyst can be easily separated from a reaction mixture and reused more than 10 times with no decrease in activity.
- Jang, Su-Bum
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p. 1793 - 1796
(2007/10/03)
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- Hydrazinolysis of (E)- and (Z)-2-Phenyl-3-Phenylethenyl-1-Phthalimidoaziridines
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Hydrazinolysis of stereoisomeric trans-2-phenyl-3-[(E)- and (Z)-phenylethenyl]-1-phthalimidoaziridines proceeds stereospecifically and yields not the expected 1-amino-2-phenyl-3-phenylethenylaziridines but isomeric 1-amino-2,5-diphenyl-3-pyrrolines. Oxidation of the latter with lead tetraacetate is also stereo-specific, and it results in formation of stereoisomeric 1,4-diphenylbutadienes. Hydrazinolysis of (E)-phthalimidoaziridines under milder conditions yields a product of incomplete removal of the phthaloyl group, whose oxidation affords cis-1,4-dihydro-1,4-diphenylpyridazino[1,2-b]phthalazine-6,11-dione.
- Belov,Blandov,Kuznetsov
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p. 641 - 646
(2007/10/03)
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- Palladium-catalyzed homocoupling reactions of organic tellurides
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Organic tellurides containing a styryl moiety react in acetonitrile to give the corresponding homocoupling products, 1,3-dienes, with moderate to quantitative yields in the presence of a catalytic amount of Pd(OAc)2 together with AgOAc at 25 °C. In contrast, such homocoupling reactions hardly occur with diaryl, alkyl aryl, dialkyl, and alkynyl aryl tellurides, even at reflux temperature and in the presence of a stoichiometric amount of palladium salt, in disagreement with reported results. The result of cross-over experiments suggests that this homocoupling reaction occurs between an alkenyl telluride and an alkenylpalladium species, the latter being formed via the migration of an alkenyl moiety from Te to Pd (transmetallation).
- Nishibayashi, Yoshiaki,Cho, Chan Sik,Ohe, Kouichi,Uemura, Sakae
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p. 335 - 339
(2007/10/03)
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- Action spectra of non-resonant two-photon (NRTP) isomerization of α, ω-diphenylpolyenes
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The efficiency of the non-resonant two-photon (NRTP) isomerizations of stilbenes and 1,4-diphenyl-1,3-butadienes were found to depend strongly on the wavelength of the laser pulses. The results not only confirm the 21Ag nature of the excited states responsible for the cis-trans isomerizations but also demonstrate that the action spectra of the NRTP reactions correspond to the two-photon allowed absorption bannds.
- Miyazawa, Takashi,Liu, Zhenlin,Liu, Chengyou,Koshihara, Shin-Ya,Kira, Mitsuo
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p. 1023 - 1024
(2007/10/03)
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- Electron transfer induced isomerization of cis,trans- and trans,trans-1,4-diphenyl-1,3-butadiene
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Irradiation of cis,trans- or trans,trans-1,4-diphenyl-1,3-butadiene with 9,10-dicyanoanthracene as a sensitizer results in predominant cis,trans → trans,trans geometric isomerization in acetonitrile. A cation radical chain mechanism is proposed to be oper
- Wakamatsu, Kan,Takahashi, Yasutake,Kikuchi, Koichi,Miyashi, Tsutomu
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p. 5681 - 5684
(2007/10/02)
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- PARTIAL HYDROGENATION OF 2-ALKYNYL-1-PHTHALIMIDOAZIRIDINES
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Partial hydrogenation of the CC bond in 2-alkynyl-1-phthalimidoaziridines over Pd/BaSO4 yields up to 85percent of the corresponding vinylaziridines.An exception is the substrates containing substituents at both triple-bonded C atoms and an unsubstitute
- Belov, V. N.,Blandov, A. N.,Kuznetsov, M. A.,Gindin, V. A.
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p. 1791 - 1795
(2007/10/03)
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- Quantum chain processes in direct photoisomerisation of diphenylpolyenes
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Photoisomerisation quantum yield under direct irradiation (330 nm) and fluorescence lifetime of diphenylbutadiene (DPB)increase as the concentration of the diene is increased.The results are discussed in terms of quantum chain process, which is believed to occur due to exchange of energy between the excited state s-trans-DPB and ground state s-cis-DPB.
- Krishna, T. S. R.,Singh, Anil K.
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p. 413 - 414
(2007/10/02)
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- Ni(0)-Triphenylphosphine Complex-Catalyzed Homo-Coupling of 1-Alkenyl Halides with Zinc Powder
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The homo-coupling of 1-alkenyl halides was examined in the presence of NiBr2(PPh3)2, PPh3, and excess zinc.The reactions proceed under very mild conditions to give high yields of conjugated dienes.The addition of KI or thiourea was unnecessary for a successful reaction, in contrast with systems without an external phosphine ligand.
- Sasaki, Ken,Nakao, Kikuji,Kobayashi, Yoshihiko,Sakai, Mutsuji,Uchino, Norito,et al.
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p. 2446 - 2448
(2007/10/02)
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- Synthesis of cis-Olefins via Palladium-Catalyzed Coupling of Organic Halides, Norbornadiene, and Organotin Compounds
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Palladium-catalyzed cross-coupling of organic halides with organotin compounds in the presence of norbornadiene gave 5,6-disubstituted norbornene, which was treated by a retro Diels-Alder reaction yielding cis-ethene and cyclopentadiene.
- Kosugi, Masanori,Kimura, Tomoyuki,Oda, Hiroshi,Migita, Toshihiko
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p. 3522 - 3524
(2007/10/02)
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- Styryl coupling vs. styryl acetate formation in reactions of styryl tellurides with palladium(II) salts
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In sharp contrast to the expected formation of a telluride-palladium complex, the treatment of either (E,E)- and (Z,Z)-distyryl tellurides (1 and 2) or (E)- and (Z)-styryl phenyl tellurides (5 and 6) with Li2PdCl4 in acetonitrile at 25 deg C results in the formation of stereoisomeric 1,4-diphenylbuta-1,3-dienes, whereas the treatment of 1 and 2 with Pd(OAc)2 produces styryl acetates solely or mainly.
- Uemura, Sakae,Takahashi, Hidetaka,Ohe, Kouichi
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- REDUCTIVE DIMERIZATION OF VINYL HALIDES IN AN Ni/Pb/Al THREE METAL REDOX SYSTEM. A FACILE ACCESS TO TERPHENYL DERIVATIVES
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A novel three metal redox system, NiCl2(bpy)/PbBr2/Al, is found to be potent in the reductive coupling of vinyl halides, affording 1,4-biaryl-1,3-butadienes, precursors of terphenyl derivatives.
- Tanaka, Hideo,Kosaka, Atsuko,Yamashita, Shiro,Morisaki, Kazuo,Torii, Sigeru
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p. 1261 - 1264
(2007/10/02)
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- Pulse Radiolysis Study of Ion Pairing of Diphenylpolyene Radical Anions with Tetrabutylammonium and Sodium Cations in Tetrahydrofuran
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Pulse radiolysis of tetrahydrofuran (THF) solutions of all-trans α,ω-diphenyl-substituted polyenes, such as 1,4-diphenylbuta-1,3-diene, 1,6-diphenylhexa-1,3,5-triene and 1,8-diphenylocta-1,3,5,7-tetraene, has been undertaken in the absence and presence of Bu4NPF6 and NaBPh4.In the presence of the salts, the absorption maxima of the diphenylpolyene radical anions are shifted to shorter wavelengths by ion pairing with Bu4N+ and Na+ as well as that of the trans-stilbene radical anion previously investigated.When Ph(CH=CH)nPH.- (n=1-4) is paired with Bu4N+, the magnitude of the spectroscopic shift is larger for n=2-4 than for n=1.On the other hand, the magnitude of the spectroscopic shift due to the ion pairing with Na+ decreases with increasing n and becomes very small in the case of n=3 or 4.The decay of the radical anions, which is due to neutralization reactions with THF(H+), is retarded by the addition of the salts.The retarding effect of the salts is attributed to the ion pairing of the reactant ions with the counterions derived from the salts.In acetonitrile solution the absorption spectra and the decay rates of the radical anions are not affected by the addition of the salts, demonstrating that the ion pairing is not important in such a polar solvent.Results for the radical anions of pyrene, perylene and triphenylethylene are presented for the sake of comparison.The appreciable spectroscopic shift due to the ion pairing with the large Bu4N+ ion was found to be characteristic of the diphenylpolyene radical anions.
- Aoyama, Takahisa,Yamamoto, Yukio,Hayashi, Koichiro
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p. 3353 - 3358
(2007/10/02)
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- A Pulse Radiolysis Study of the Formation of Dimer Radical Cations of Aromatic Olefins
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The formation of dimer radical cations of several aromatic olefins has been studied by the pulse radiolysis technique.The aromatic olefins examined are 2-vinylnaphthalene (VN), 2-(1-propenyl)naphthalene (PN), 4-vinylbiphenyl (VBP), trans,trans-1,4-diphenyl-1,3-butadiene (1,4-DPB), and s-trans-2,3-diphenyl-1,3-butadiene (2,3-DPB).The formation of dimer radical cations were observed with all of them except 1,4-DPB, although it was very limited with VBP.Two types of dimer radical cations, bonded and associated ones, are formed with VN, whereas only the associated dimer radical cation is formed with PN.The influence of the aromatic substituents on the formation of the dimer radical cations is described.
- Chikai, Yukio,Yamamoto, Yukio,Hayashi, Koichiro
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p. 2281 - 2286
(2007/10/02)
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- Stereoselective E and Z Olefin Formation by Wittig Olefination of Aldehydes with Allylic Phosphorus Ylides. Stereochemistry
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Sterically crowded allylic tributylphosphorus ylides such as β-γ-disubstituted allylic ylides react with various aldehydes to afford E olefins with high stereoselectivity (E>92percent).As the steric demand of the ylides was decreased, bulky aldehydes were required to achieve high E selectivity.On the other hand, predominant or exclusive formation of Z olefins was achieved by using allylic triphenylphosphorus ylides and tertiary aldehydes like pivaldehyde, while the combination of allylic triphenylphosphorus ylides and such large secondary aldehydes as cyclohexanecarboxaldehyde led to E olefin formation under the lithium salt free conditions.The distinct lithium salt effect was observed in the reaction effected with triphenylphosphorus ylides.The origin of the observed E or Z selectivity can be reasonably explained according to Vedejs' rationale on the Wittig reaction stereochemistry.
- Tamura, Rui,Saegusa, Koji,Kakihana, Masato,Oda, Daihei
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p. 2723 - 2728
(2007/10/02)
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