- New Arylene-Germylene-Vinylene Compounds: Stereoselective Synthesis, Characterization, and Photophysical Properties
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The stereoselective route toward new molecular and macromolecular compounds containing arylene-germylene-vinylene units is described. The reagents for germylative coupling reaction were 1,4-bis(dimethylvinylgermyl)benzene (1) and vinyl- and divinylarenes
- Ludwiczak, Monika,Bayda, Ma?gorzata,Dutkiewicz, Micha?,Fra?kowiak, Dawid,Majchrzak, Mariusz,Marciniak, Bronis?aw,Marciniec, Bogdan
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- A new class of stereoregular vinylene-arylene copolymers with double-decker silsesquioxane in the main chain
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A synthesis of a new macromolecular class of vinylene-arylene copolymers with double-decker silsesquioxane in the main chain is presented. Two transition-metal-catalyzed processes, which is silylative-coupling copolycondensation (SCC) and ADMET copolymerization of divinyl-substituted double-decker silsesquioxanes (DDSQ-2SiVi) with selected diolefins, are reported to be highly efficient tools for the formation of stereoregular copolymers containing DDSQ-silylene-vinylene-arylene units. The copolymeric products are studied in terms of their structural, thermal, and mechanical properties.
- Zak, Patrycja,Dudziec, Beata,Dutkiewicz, Micha?,Ludwiczak, Monika,Marciniec, Bogdan,Nowicki, Marek
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- Living anionic polymerization of 1,4-divinylbenzene and its isomers
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The anionic polymerization of 1,4-divinylbenzene (1) and its ortho (2) and meta isomers (3) were studied under a variety of conditions. One of the two vinyl groups of 1 was selectively and exclusively polymerized in a living manner by the addition of a suitable additive under the conditions of -78 C for 1 min and -95 C for 30 min. Under such conditions, the unwanted addition reaction of the chain-end anion to the pendant vinyl group was almost suppressed and soluble polymers with predictable molecular weights of up to 60 500 g/mol and narrow molecular weight distributions (Mw/Mn 1.05) were quantitatively obtained. The amount of dimerized chain produced by the addition reaction was negligible or very small (5%). The effective additives in the polymerization involve potassium alkoxides and phenoxides, derived from tert-butyl alcohol, sec-butyl alcohol, 2,4-dimethyl-3-pentanol, 1-methylcyclohexanol, 1:2,5:6-di-O-isopropylidene-α-d-glucofuranose, phenol, 1-naphthol, and 2,6-di(tert-butyl)-4-methylphenol, and potassium carboxylate derived from pivalic acid. The living polymer of 1 was not stable at -78 C after 5 min or longer times, but very stable at -95 C even for 30 min. The chain-end anion could be stabilized by end-capping with tert-butyl methacrylate and 1,1-diphenylethylene, and the resulting anions remained unchanged at -78 C even after several hours.
- Tanaka, Shunsuke,Matsumoto, Masayoshi,Goseki, Raita,Ishizone, Takashi,Hirao, Akira
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- New synthetic applications of indium organometallics in cross-coupling reactions
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The use of indium organometallics in multifold and sequential cross-coupling reactions is reported. Triorganoindium reagents (R3In) react, under palladium catalysis, with oligohaloarenes affording the multiple cross-coupling products in a single operation. In the reaction, the three organic groups (alkyl, aryl, alkenyl or alkynyl) attached to indium are efficiently transferred to the electrophile, with only a slight excess of organometallic reagent. We demonstrate that indium organometallics are useful reagents for sequential cross-coupling reactions. This reaction illustrates the high chemoselectivity of R3In. Georg Thieme Verlag Stuttgart.
- Pena, Miguel A.,Perez Sestelo, Jose,Sarandeses, Luis A.
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- Synthesis of core cross-linked star polymers consisting of well-defined aromatic polyamide arms
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Homopolymer-arm, block-arm, and miktoarm star polymers consisting of poly(N-octylm-benzamide) and poly(N-H-m-benzamide) were synthesized by means of a core cross-linking method. Macromonomers (MM) with the styryl terminal moiety were synthesized by chain-growth condensation polymerization of 3-(alkylamino)benzoic acid esters 1 in the presence of phenyl 4-vinylbenzoate as an initiator, and copolymerization with N,N'-methylenebis(acrylamide) as a divinyl monomer in the presence of 2,2'-azobis(isobutyronitrile) at 60 °C yielded the corresponding star polymers. In the synthesis of star polymers containing poly(N-H-m-benzamide) arms, the 4-(octyloxy)benzyl group on the amide nitrogen of the obtained star polymers was removed with trifluoroacetic acid. The number of arms per molecule, determined by multiangle laser light scattering, varied in the range of 36-100 depending on the N-alkyl group of 1 and the molecular weight of MM. The 1H NMR spectra of the star polymers in dimethyl sulfoxide revealed that the poly(N-octyl-m-benzamide) segments and arms of the block-arm and miktoarm star polymers, respectively, were compactly packed at room temperature and became extended at higher temperatures.
- Ohishi, Tomoyuki,Masukawa, Tomohiro,Fujii, Shuichi,Yokoyama, Akihiro,Yokozawa, Tsutomu
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- New heck-type coupling reactions of natural tetrapyrroles - Synthesis of porphyrinoligomers bridged by divinyl- and trivinylbenzene
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Using palladium(0)-catalyzed coupling reactions we were able to synthesize mono-, di-, and trimeric porphyrins linked by di- and trivinylbenzenes. The reactions were carried out with palladium(II) acetate in DMF under phase-transfer conditions. These coupling conditions are new in the field of porphyrin chemistry and proved to be a useful tool in the synthesis of C-C linked oligomeric porphyrins, as these compounds can be obtained in a simple one pot reaction with good yields.
- Gauler, Rainer,Risch, Nikolaus
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- Fluorescent sensor based on a novel conjugated polyfluorene derivative
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A novel water-soluble polyfluorene derivative, poly[(9,9-bis(3′-((N, N-dimethylamino)N-ethylammonium)propyl)-2,7-fluorene)-alt-2,7-(9, 9-p-divinylbenzene)]dibromide (P-2) was synthesized by the palladium-catalyzed Suzuki coupling reaction and it's quaternized ammonium polyelectrolyte derivatives was obtained through a postpolymerization treatment on the terminal amino groups. The electrochemical and optical properties of the copolymers was fully investigated. The results showed that the new polyfluorene derivative had high electronic conductivity and strong fluorescence, therefore it had good potential to be used in chemical and biological sensors, as shown in optical sensing of bovine albumin (BSA) in this study.
- Gao, Weiqiang,Yan, Mei,Ge, Shenguang,Liu, Xiaoxia,Yu, Jinghua
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- Catalytic chain transfer mediated autopolymerization of divinylbenzene: Toward facile synthesis of high alkene functional group density hyperbranched materials
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A facile and highly reproducible autopolymerization method, mediated by catalytic chain transfer, for the synthesis of hyperbranched materials with high alkene functional group density is reported. The rapid autopolymerization of divinylbenzene at 150 °C in the absence of any catalytic chain transfer agent was demonstrated to result in the formation of highly cross-linked networks/gels in less than 10 min. Exploitation of the extremely high chain transfer coefficient of bis[(difluoroboryl)diphenylglyoximato]cobalt(II) delayed gelation and produced good yields of high molecular weight hyperbranched divinylbenzene in under 1 h on a multigram scale. Gas chromatography was employed to monitor the levels of conversion over the course of the reaction. The materials produced were characterized by GPC, MALLS, and viscometry.
- Barker, Ian A.,El Harfi, Jaouad,Adlington, Kevin,Howdle, Steven M.,Irvine, Derek J.
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- Nickel-Catalyzed Reductive Cross-Coupling of Aryl Bromides with Vinyl Acetate in Dimethyl Isosorbide as a Sustainable Solvent
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A nickel-catalyzed reductive cross-coupling has been achieved using (hetero)aryl bromides and vinyl acetate as the coupling partners. This mild, applicable method provides a reliable access to a variety of vinyl arenes, heteroarenes, and benzoheterocycles, which should expand the chemical space of precursors to fine chemicals and polymers. Importantly, a sustainable solvent, dimethyl isosorbide, is used, making this protocol more attractive from the point of view of green chemistry.
- Huang, Xia,Jin, Jian,Lei, Chuanhu,Su, Mincong
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supporting information
(2022/01/15)
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- Copper-Catalyzed Defluorinative Hydroarylation of Alkenes with Polyfluoroarenes
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A catalytic defluorinative hydroarylation of alkenes with polyfluoroarenes in the presence of dppbz-ligated Cu catalyst and silanes was developed. This method provides a straightforward and alternative avenue to synthetic important polyfluorinated arenes with readily available and bench-stable alkenes as latent nucleophiles, and therefore avoids conventional reliance on stoichiometric quantities of organometallic reagents. This reaction proceeds under very mild conditions and exhibits good functional group compatibility and high level of regioselectivity. The synthetic potential of this method was further demonstrated by a gram-scale synthesis, and an array of experimental studies were also carried out to elaborate the probable mechanism.
- Fu, Bin,Li, Xiaohong,Xiong, Tao,Yuan, Xiuping,Zhang, Qian,Zhang, Qiao
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supporting information
p. 23056 - 23060
(2020/10/19)
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- A Strategy To Obtain o-Naphthoquinone Methides: Ag(I)-Catalyzed Cyclization of Enynones for the Synthesis of Benzo[ h]chromanes and Naphthopyryliums
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A new strategy to obtain o-NQM intermediates through a ring-formation strategy by Ag(I)-catalyzed cyclization of 2-alkenylphenyl alkynyl ketones and its [4 + 2] annulations with styrenes has been developed. This reaction features high efficiency, mild reaction conditions, as well as flexible substitutions and atom economy. The obtained benzo[h]chromane products were further oxidized to naphthopyryliums, which displayed tunable photophysical properties.
- Wu, Feng,Zhu, Shifa
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supporting information
(2019/03/08)
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- Method for synthesizing olefin compound by photo-induced one-pot process
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The invention discloses a method for synthesizing an olefin compound by a photo-induced one-pot process. The method comprises the following step of subjecting a halohydrocarbon and an aldehyde compound to a reaction under the condition of irradiation in an inert atmosphere by taking alkali metal carbonate as a base, taking an organic phosphine compound as an adjuvant and taking a photosensitizer as a catalyst, thereby obtaining the olefin compound. According to the method disclosed by the invention, the olefin compound is produced from the halohydrocarbon and the aldehyde compound in a high-yield manner under the condition of irradiation in the inert atmosphere under normal-temperature reaction conditions by taking acetonitrile, DMF (N,N-dimethylformamide) or DMA (N,N-dimethylacetamide) asa solvent, taking an organic phosphine reagent as a reaction adjuvant, taking the alkali metal carbonate as the base and taking the photosensitizer as the catalyst. Compared with the conventional olefin synthesis methods, the method disclosed by the invention has the obvious advantages that the reaction raw materials are readily available, the tolerance to a variety of functional groups on halohydrocarbons and aldehydes is high, the yield is high, the separation and purification of a product are simple and convenient, and the like.
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Paragraph 0077-0079
(2018/11/03)
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- Phenylenevinylene oligomers by Mizoroki-Heck cross coupling reaction. Structural and optoelectronic characterization
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In order to study the effect of the molecular structure on the optical properties of totally trans-trans phenylenevinylene oligomers (OPVs), sixteen 1,4-distyrylbenzene derivatives (1a-i and 2a-g) functionalized with different electron-donating (ED) and electron-withdrawing (EW) groups were synthesized by the Mizoroki-Heck cross coupling reaction in moderate to good yields (40–95%). The implemented methodology, with a small modification previously reported by our group, allows obtaining the desired vinyl configuration as well as one novel OPV compound (1h). After structural characterization by several techniques (e.g. FTIR, 1H, 13C and Solid-State NMR), particular emphasis was placed upon the investigation of their optical properties by UV–vis and fluorescence spectroscopies. The results showed that, with only one exception, the ED and EW groups at the ends of OPV systems lead to a bathochromic shift. This effect is intensified with the introduction of methoxy groups on the central ring. Consistent with these, the HOMO-LUMO gaps (ΔE) decreases as the strength of ED and EW substituents increases. The ED and EW substituents also lead to a decrease in the Φf values. This contribution in the area of organic electronics can be used as a reference to better select the most appropriate technological application for each OPV and this can be extrapolated to their respective structurally analogous segmented polymer.
- Estrada, Sandra E.,Ochoa-Puentes, Cristian,Sierra, Cesar A.
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p. 448 - 457
(2016/12/30)
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- In Situ Generation of Formaldehyde and Triphenylphosphine from (Hydroxymethyl)triphenylphosphonium and Its Application in Wittig Olefination
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The reaction of (hydroxymethyl)triphenylphosphonium with benzylic or allylic halide under basic conditions at room temperature affords terminal alkenes in 61-89% yields. In this reaction, both formaldehyde and triphenylphosphine are in situ generated from (hydroxymethyl)triphenylphosphonium and further undergo Wittig olefination with benzylic or allylic halide.
- Huang, Wenhua,Xu, Jie
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supporting information
p. 1777 - 1782
(2015/08/06)
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- Polyaniline-anchored palladium catalyst-mediated Mizoroki-Heck and Suzuki-Miyauraa reactions and one-pot Wittig-Heck and Wittig-Suzuki reactions
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A polyaniline-anchored palladium catalyst was prepared and screened for coupling reactions of aryl halides. The robust and recyclable catalyst was effective in Mizoroki-Heck and Suzuki-Miyaura reactions of aryl bromides and aryl iodides. The catalyst system was further employed for one-pot Wittig-Heck and Wittig-Suzuki combinations to build conjugated compounds in good conversions.
- Patel, Heta A.,Patel, Arun L.,Bedekar, Ashutosh V.
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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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- Flow Chemistry Syntheses of Styrenes, Unsymmetrical Stilbenes and Branched Aldehydes
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Two tandem flow chemistry processes have been developed. A single palladium-catalysed Heck reaction with ethylene gas provides an efficient synthesis for functionalised styrenes. Through further elaboration the catalyst becomes multi-functional and performs a second Heck reaction providing a single continuous process for the synthesis of unsymmetrical stilbenes. In addition, the continuous, rhodium-catalysed, hydroformylation of styrene derivatives with syngas affords branched aldehydes with good selectivity. Incorporation of an in-line aqueous wash and liquid-liquid separation allowed for the ethylene Heck reaction to be telescoped into the hydroformylation step such that a single flow synthesis of branched aldehydes directly from aryl iodides was achieved. The tube-in-tube semi-permeable membrane-based gas reactor and liquid-liquid separator both play an essential role in enabling these telescoped flow processes.
- Bourne, Samuel L.,O'Brien, Matthew,Kasinathan, Sivarajan,Koos, Peter,Tolstoy, Paeivi,Hu, Dennis X.,Bates, Roderick W.,Martin, Benjamin,Schenkel, Berthold,Ley, Steven V.
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p. 159 - 172
(2013/03/13)
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- Supported palladium nanoparticles as heterogeneous ligand-free catalysts for the Hiyama C-C coupling of vinylsilanes and halobenzenes leading to styrenes
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The Hiyama C-C coupling reaction of a wide range of aryl iodides and vinylsilanes has been performed using ligand-free solid catalysts based on supported palladium nanoparticles. Among the supports tested (Mg, TiO 2, CeO2 and active carbon), the most active catalysts were those in which palladium is supported on MgO and TiO2. Analogous Pt and Au materials were inefficient to promote this reaction. Leaching tests suggest that there is some contribution of dissolved Pd since Pd in solution has been detected and the scavenging test decreases the initial reaction rate. Although the solid Pd catalysts can be reused, it was, however, observed that they undergo a certain deactivation upon use that can be attributed to several factors including the presence of inorganic compounds on the catalyst, Pd leaching or agglomeration of Pd NPs.
- Grirrane, Abdessamad,Garcia, Hermenegildo,Corma, Avelino
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- Expeditious synthesis of fluorinated styrylbenzenes and polyaromatic hydrocarbons
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A series of fluorinated styrylbenzene derivatives were synthesized by the Mizoroki-Heck reaction using phosphine-free catalytic conditions or by adopting the one-pot Wittig-Heck reaction sequence. The fluorinated styrylbenzenes were converted into polyaromatic hydrocarbons such as phenanthrenes, [4]helicenes, and benzo[ghi]perylene by a modified photocyclization procedure involving I 2-THF condition.
- Bedekar, Ashutosh V.,Chaudhary, Anju R.,Shyam Sundar,Rajappa, Murali
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p. 392 - 396
(2013/02/23)
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- Selective iron-catalyzed transfer hydrogenation of terminal alkynes
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A novel iron-catalyzed transfer hydrogenation of alkynes to the corresponding alkenes applying formic acid as a hydrogen donor is reported. An in situ combination of Fe(BF4)2·6H2O and tetraphos allows for highly selective hydrogenation of a broad range of aromatic and aliphatic alkynes tolerating different functional groups.
- Wienhoefer, Gerrit,Westerhaus, Felix A.,Jagadeesh, Rajenahally V.,Junge, Kathrin,Junge, Henrik,Beller, Matthias
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supporting information; experimental part
p. 4827 - 4829
(2012/06/04)
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- An easy access to styrenes: Trans aryl 1,3-, 1,4- and 1,5-dienes, and 1,3,5-trienes by Hiyama cross-coupling catalyzed by palladium nanoparticles
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A convenient and efficient procedure has been developed for the vinylation of aryl-, styrenyl-, cinnamyl- and dienyl-halides by a Pd(0) nanoparticle-catalyzed Hiyama cross-coupling to provide the corresponding dienes and trienes in high yields. The reaction does not require any ligand or co-catalyst, and is carried out using PdCl2 and tetrabutyl ammonium fluoride (TBAF) in THF. Pd nanoparticles are generated in situ and are the active catalytic species in this reaction. A wide range of functionalized styrenes, trans aryl 1,3-, 1,4- and 1,5- dienes, 1,2-, 1-3 and 1,4-bis(1,3-dienes), and 1,3,5-trienes can be obtained by this procedure. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011.
- Chatterjee, Tanmay,Dey, Raju,Ranu, Brindaban C.
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experimental part
p. 1103 - 1110
(2011/07/08)
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- Wittig like methylenation of aldehydes in a microflow system: Selective methylenation by differential of plural reactions
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Methylenation of aldehydes with bis(iodozincio)methane was performed using a microflow system. Treatment of a dialdehyde with bis(iodozincio)methane in the system can divide two methylenation reactions and realize selective transformation.
- Takada, Yoshiaki,Matsubara, Seijiro
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scheme or table
p. 364 - 365
(2011/05/04)
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- Highly stereoselective synthesis of novel trans-thiophenylene-silylene- vinylene-arylene molecular and macromolecular compounds
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Novel stereoregular molecular compounds 8-13 containing thiophenylene-silylene-vinylene-phenylene units have been synthesised via highly effective silylative coupling of styrene and 1,4-divinylbenzene (7) with respective vinylsilylthiophenes (3, 4) and bis(vinylsilyl)thiophenes (5, 6) catalyzed by RuHClCO(PCy3)2. Respective copolymers (14, 15) were produced via silylative copolycondensation of 5 and 6 with 7. All products were isolated and characterised by NMR, MS, HRMS and two of them 10 and 11 by X-ray method. Catalytic study as well as stoichiometric reactions of Ru-H (1) with 2-(vinylsilyl)thiophene (3) and Ru-Si (16) with styrene confirmed the mechanism of the silylative coupling olefins with vinylsilicon compounds.
- Ludwiczak, Monika,Majchrzak, Mariusz,Marciniec, Bogdan,Kubicki, MacIej
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experimental part
p. 1456 - 1464
(2011/05/09)
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- Vinylation of aromatic halides using inexpensive organosilicon reagents. Illustration of design of experiment protocols
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The preparation of styrenes by palladium-catalyzed cross-coupling of aromatic iodides and bromides with divinyltetramethyldisiloxane (DVDS) in the presence of inexpensive silanolate activators has been developed. To facilitate the discovery of optimal reaction conditions, Design of Experiment (DoE) protocols were used. By the guided selection of reagents, stoichiometries, temperatures, and solvents, the vinylation reaction was rapidly optimized with three stages consisting of ca. 175 experiments (of a possible 1440 combinations). A variety of aromatic iodides undergo cross-coupling at room temperature in the presence of potassium trimethylsilanoate using Pd(dba) 2 in DMF in good yields. Triphenylphosphine oxide is needed to extend catalyst lifetime. Application of these conditions to aryl bromides was accomplished by the development of two complementary protocols. First, the direct implementation of the successful reaction conditions using aryl iodides at elevated temperature in THF provided the corresponding styrenes in good to excellent yields. Alternatively, the use of potassium triethylsilanolate and a bulky "Buchwald-type" ligand allows for the vinylation reactions to occur at or just above room temperature. A wide range of bromides underwent coupling in good yields for each of the protocols described.
- Denmark, Scott E.,Butler, Christopher R.
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p. 3690 - 3704
(2008/10/09)
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- COMPOUNDS
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The present invention relates to compounds of formula (I), or pharmaceutically acceptable salts thereof, wherein X is selected from (II) and (III), Y is selected from SO2NH, CONH, CH=N, CH2NH and CH=CH; R1-5 are each independently selected from H, OH, OR6, CO2H, C02R7, NO2, CN CONR8R9, CONHR10, CO2(CH2)nCO2R11, CO2(CH2)mO(CO)R12, CO2CHR13COR14, CONH(CH2)pCO2R15, CONH(CH2)qO(CO)R16, CONHCHRI7COR18; R6-18 are each independently hydrocarbyl; n, m, p and q are each independently 1, 2, 3 or 4; with the proviso that when X is phenyl, Y is CH=CH, R3 is OH and R1, R4 and R5 are H, R2 is other than COON. Further aspects of the invention relate to the use of such compounds in the preparation of a medicament for the treatment or prevention of transmissible spongiform encephalopathies (TSEs), and pharmaceutical compositions comprising the same.
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Page/Page column 17
(2010/02/14)
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- Synthesis of analogues of Congo red and evaluation of their anti-prion activity
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No cure as of yet exists for any of the transmissible spongiform encephalopathies. In this paper, we describe the synthesis of analogues of Congo red and evaluation against a cellular model of infection, the SMB (scrapie mouse brain) persistently infected cell line, for their ability to inhibit the infectivity of the abnormal form of prion protein (PrP-res). The compounds have also been tested for their ability to inhibit the polymerization of PrP C by PrP-res. A number of analogues showed inhibition of PrP-res infectivity at nanomolar concentrations. Several analogues show promise; the most active compound, 2a, inhibits the formation of PrP-res in SMB cells with an EC50 of 25-50 nM.
- Sellarajah, Shane,Lekishvili, Tamuna,Bowring, Claire,Thompsett, Andrew R.,Rudyk, Helene,Birkett, Christopher R.,Brown, David R.,Gilbert, Ian H.
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p. 5515 - 5534
(2007/10/03)
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- Tetraorganoindates as Nucleophilic Coupling Partners in Pd-Catalyzed Cross-Coupling Reactions
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(Equation presented) In situ generated ate complex In situ-generated tetraorganoindate complexes from the reaction of 1 equiv of indium trichloride with 4 equiv of appropriate organometallics are efficient nucleophiles in Pd-catalyzed cross-coupling reactions. In this novel reaction tetraorganoindates containing methyl, 1°- and 2°-alkyl, vinyl, alkynyl, and aryl groups transfer the four organic groups to a variety of electrophiles with high atom efficiency.
- Lee, Phil Ho,Lee, Sung Wook,Seomoon, Dong
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p. 4963 - 4966
(2007/10/03)
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- Preparation of preparing substituted indanones
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a process for the preparation of indanones of the formula II from, indanones of the formula I or of indanones of the formula IIa from indanones of the formula Ia comprises reacting an indanone of the formula I or Ia with a coupling component.
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- Synthesis of Substituted 1,4-Divinylbenzenes by Heck Reactions with Compressed Ethene
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Substituted 1,4-divinylbenzenes 3a-i were synthesized by twofold Heck coupling from the corresponding 1,4-dibromo- (electron withdrawing substituents) or 1,4-diiododialkoxybenzenes 1a-i and ethene. Oligomerizations could be suppressed by increasing the pressure of ethene to 30 bar, simultaneously improving the yields of the title compounds.
- Detert, Heiner,Sugiono, Erli
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p. 358 - 362
(2007/10/03)
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- Nickel-Catalyzed Olefination of Cyclic Benzylic Dithioacetals by Grignard Reagents. Scope and Mechanism
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The details of the first nickel-catalyzed olefination of cyclic dithioacetals to form substituted styrenes and aryl-substituted 1,4-pentadienes are described.The reaction represents a new synthetic use of the dithioacetal functionality.Only nickel complexes catalyzes these cross-coupling reactions; palladium complexes displayed no catalytic activity under the reaction conditions employed.Selective coupling occurred.A mechanism for the reaction is proposed.The experimental evidence indicates that, in these nickel-catalyzed couplings, cyclic dithioacetals are more reactive than their acyclic analogues.This increased reactivity appears to be the result of maintaining the two sulfur atoms in close proximity to each other by the use of a short chain of methylene groups.
- Ni, Zhi-Jie,Mei, Nai-Wen,Shi, Xian,Tzeng, Yih-Ling,Wang, Maw Cherng,Luh, Tien-Yau
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p. 4035 - 4042
(2007/10/02)
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- Optically active styrene derivatives, polymers obtained from these, complexes with iridium(I) and their use
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Optically active compounds of the formula I STR1 in which R1 is C1 -C4 -alkyl, phenyl or benzyl, R2 is a radical of the formula II or IIa STR2 in which R3 is H or --CH3, or R1 and R2 together form a radical of the formula STR3 in which R2 has the meaning given above; and * represents predominantly R or predominantly S configuration. The compounds can be polymerized to give homopolymers or copolymers. The compounds and the polymers can be complexed with iridium(I) salts in the presence of a diene. The complexes are suitable as enantioselective catalysts.
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- Cross-Coupling of Organosilanes with Organic Halides Mediated by Palladium Catalyst and Tris(diethylamino)sulfonium Difluorotrimethylsilicate
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In the presence of tris(diethylamino)sulfonium difluorotrimethylsilicate (TASF) and allylpalladium chloride dimer as a catalyst, organosilicon compounds like vinyl-, ethynyl-, and allylsilanes react with such organic halides as aryl, vinyl, and allyl halides to give the corresponding coupled products in synthetically useful yields in a stereospecific and chemoselective manner.
- Hatanaka, Yasuo,Hiyama, Tamejiro
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p. 918 - 920
(2007/10/02)
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- FLASH VACUUM THERMOLYSIS OF DISPIROALKADIENES
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The Flash Vacuum Thermolysis (FVT) of dispirotetradeca -4,13-diene (7a). dispirotrideca-4,12-diene (7b) and dispirodeca-4,9-diene (7e) at 500-750 deg C is reported.The complicated reaction mixture from 7a and 7b (Scheme 3) included at lower temperatures vinylspiroalkadienes 9, ethylidenespiroalkadiene 10b, β-ethylcycloalkabenzenes 11, while at higher temperatures, p-n-alkyl-(5) and p-sec-alkylstyrenes 14 and p-divinylbenzene (15) dominated.Product formation is explained by invoking diradicals 8,6 and 12 as well as the cyclophanes 1 and 13 as intermediates.For 7e, the product mixture was less complicated and consisted of p-ethylstyrene (5e), 15 and, unexpectedly,p-isopropylstyrene (14e) which contains one carbon more than the starting material.The analysis and interpretation of product formation largely confirms previously suggested reaction pathways and furnishes further interesting details.However, new and unexpected features are also encountered, especially in the fragmentations of 1 and 13 which may stimulate future investigations on the thermal behaviour of these relatively simple hydrocarbons.
- Kraakmann, P. A.,Nibbering, E. T. J.,Wolf, W. H. de,Bickelhaupt, F.
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p. 5109 - 5124
(2007/10/02)
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- Synthesis of Functionalized Styrenes via Palladium-Catalyzed Coupling of Aryl Bromides with Vinyl Tin Reagents
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Highly functionalized styrene derivatives have been synthesized in a single step by the palladium-catalyzed coupling of aryl bromides with tributylethenylstannane.Aryl bromides substituted with electron-withdrawing groups couple rapidly under the reaction conditions while bromides containing electron-donating substituents require further addition of catalyst for complete conversion. 1,4-Dibromobenzene can be coupled in a highly selective fashion with either 1 or 2 equiv of tin reagent to give 4-bromostyrene or diethenylbenzene, respectively.
- McKean, D. R.,Parrinello, G.,Renaldo, A. F.,Stille, J. K.
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p. 422 - 424
(2007/10/02)
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- THERMAL CONVERSION OF 1,5,9-TRIYNES. CYCLOADDITIONS OR SIGMATROPIC SHIFTS?
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The gas phase pyrolyses of variously labeled 1,5,9-decatriynes (1) and 1,5,9-cyclododecatriynes (2) were investigated to determine possible modes of thermal isomerizations.Conditions included temperatures in the range 400-600 deg C, pressures of 40 -10E-4 Torr, and contact times of ca 1 ms to 15 s.The labeling patterns in 1 and 2 were chosen such as to be able to distinguish direct intramolecular cycloadditions of the alkyne units to form an aromatic ring (perhaps with subsequent rearrangements), and sigmatropic shifts of the 1,5-diyne moieties.Methods for synthesizing the isotopically (particularly (13)C) labeled triynes were devised and implemented.The route to 5,6-(13)C2-1,5,9-decatriyne (1c) made use of a new procedure for the synthesis of symmetrically disubstituted alkynes involving coupling between two equivalents of an alkyl copper reagent and diiodoacetylene-(13)C2.The synthesis of 1,10-(13)C2-1,5,9-cyclododecatriyne (2b) was accomplished starting with K(13)CN, elaboration to labeled diethyl succinate, a crucial bis-Wittig condensation to labeled 1,5,9-cyclododecatriene 10, and bromination-dehydrobromination of the latter (NaOH-ethylene glycol).Products from the pyrolysis of unlabeled 1a included dicyclobutabenzene, naphtalene and 3,4-dimethylidene-1-(but-3-ynyl)cyclobutene.Pyrolysis of 1b gave 3,6-dideuteriodicyclobutabenzene and partially deuterated naphthalene, that of 1c produced 1,2-(13)C2-dicyclobutabenzene and 9,10-(13)C2-naphthalene.While the pyrolysis of 2a resulted in hexamethylidenecyclohexane (hexaradialene), 2b furnished 1,4-(13)C2-hexaradialene.The results rule out the occurence of cycloadditions of the alkyne units, but are consistent with the intervention of a series sigmatropic shifts which connect starting materials with products.
- Dower, William V.,Vollhardt, K. Peter C.
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p. 1873 - 1882
(2007/10/02)
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- Flash Pyrolysis of Selenides. Syntheses of Bibenzyls, Olefins, and Related Compounds
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Pyrolyses of a series of selenides and diselenides were studied. Selenides and diselenides bound with an active methylene group like benzyl gave a variety of substituted bibenzyls and related ethane derivatives in high yields. Other diselenides were easily caused to cleave to give various aromatic and aliphatic olefins in good yields together with elemental selenium. Lepidopterene, paracyclophane, and benzocyclobutene were prepared by thermal cleavage of their corresponding phenylselenomethyl-substituted compounds as an application of the pyrolysis concerned.
- Higuchi, Hiroyuki,Otsubo, Tetsuo,Ogura, Fumio,Yamaguchi, Hachiro,Sakata, Yoshiteru,Misumi, Soichi
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p. 182 - 187
(2007/10/02)
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