- PREPARATION OF α-QUATER-, α-SEXI, AND α-OCTITHIOPHENES
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α-Quaterthiophene (1), α-sexithiophene (2), and α-octithiophene (3) (the highest member of α-oligothiophenes ever synthesized) were prepared from α-bithiophene, α-terthiophene, and α-quaterthiophene, respectively, via monobromination with N-bromosuccinimide followed by reductive coupling reaction with an activated nickel(0) reagent.
- Nakayama, Juzo,Konishi, Toru,Murabayashi, Shigeru,Hoshino, Masamatsu
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- One-pot, regioselective consecutive multihalogenation of 2,2′-bithiophene
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The one-pot regioselective consecutive multihalogenation of 2,2′-bithiophene (1) was demonstrated. Compound 1 was consecutively halogenated with lithium halides such as lithium bromide, chloride, and/or iodide in the presence of lead tetraacetate in chloroform at room temperature or under reflux conditions to give 5-bromo(or chloro)-5′-iodo(or chloro)-, 3-bromo(or chloro)-5,5′-dibromo(or dichloro, diiodo)-, 3,3′-dibromo-(or dichloro)-5,5′-diiodo(or dibromo, dichloro)-, and 3,3′,5-tribromo(or trichloro)-5′-iodo(or bromo)-2,2′- bithiophenes. Notably, this process offers a regioselective method for consecutive multihalogenation in one pot, and the yields and selectivity are also higher than those obtained in the step-by-step and concurrent halogenation methods. Copyright
- Kim, Bo Ram,Kim, Eun Jung,Sung, Gi Hyeon,Kim, Jeum-Jong,Shin, Dong-Soo,Lee, Sang-Gyeong,Yoon, Yong-Jin
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p. 2788 - 2791
(2013/06/27)
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- Green halogenation of aromatic heterocycles using ammonium halide and hydrogen peroxide in acetic acid solvent
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The green generation of X+ (X = Br, I) using hydrogen peroxide in aqueous acetic acid allows access to aromatic heterocyclic halides in yields and purities comparable to syntheses employing N-bromosuccinimide. In activated and unsubstituted thiophene rings, regioselectivity is quantitative for positions α to the sulfur; pyrroles also give quantitative reactions, at least initially. Deactivated rings, including furans and thiazoles, as well as thiophenes with strongly electron-withdrawing groups showed little to no reactivity under the conditions investigated. The reaction shows remarkable functional group tolerance (to alcohol, nitro, alkyl, halo, and carbonyl groups), as shown through reaction with substituted phenols. In all bromination reactions, reaction yields and regiochemistry were very similar to reactions involving N-bromosuccinimide in tetrahydrofuran solvent.
- D'Aleo, Danielle N.,Allard, Sheena R.,Foglia, Cassandra C.,Parent, Shawna L.M.,Rohr, David J.,Gottardo, Christine,MacKinnon, Craig D.
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supporting information
p. 679 - 683
(2013/08/23)
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- Direct alkynylation of thiophenes: Cooperative activation of TIPS-EBX with gold and Bronsted acids
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United we stand! Cooperative activation of the hypervalent-iodine reagent TIPS-EBX with a gold catalyst and a Bronsted acid allowed the first direct ethynylation of thiophenes at room temperature (see scheme; TFA = trifluoroacetic acid). The obtained ethynylthiophenes are important building blocks for organic dyes and electronic materials.
- Brand, Jonathan P.,Waser, Jerome
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supporting information; experimental part
p. 7304 - 7307
(2010/11/05)
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- A novel method for the bromination of thiophenes
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A novel, fast and convenient method for the bromination of thiophenes and oligothiophenes with N-bromosuccinimide (NBS) using ultrasonic irradiation is elaborated. The yield of bromothiophenes strongly depends on the initial thiophene structure and nature of the solvent.
- Arsenyan, Pavel,Paegle, Edgars,Belyakov, Sergey
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scheme or table
p. 205 - 208
(2010/03/24)
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- Selective halogenation of bithiophenes using 2-halopyridazin-3(2H)-ones under ambient conditions
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2,2′-Bithiophene and halogenated-2,2′-bithiophenes were halogenated with 2-halo-4,5-dichloropyridazin-3(2H)-one in the presence of zinc halide to give selectively the corresponding dihalo-, trihalo-, and tetrahalo-2,2′-bithiophenes involving the same or different halogens in excellent yields, respectively. Georg Thieme Verlag Stuttgart.
- Jung, Kwang-Ju,Seung, Beom Kang,Won, Ju-Eun,Park, Song-Eun,Ki, Hun Park,Jong, Keun Park,Lee, Sang-Gyeong,Yoon, Yong-Jin
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experimental part
p. 490 - 494
(2009/08/09)
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- Selective monolithiation of dibromobiaryls using microflow systems
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(Chemical Equation Presented) Selective monolithiation of dibromobiaryls, such as 2,2′-dibromobiphenyl, 4,4′-dibromobiphenyl, 2,7-dibromo-9,9-dioctylfluorene, 2,2′-dibromo-1,1′-binaphthyl, and 5,5′-dibromo-2,2′-bithiophene, with 1 equiv of n-butyllithium followed by the reaction with electrophiles was achieved using a microflow system by virtue of fast micromixing and precise temperature control. Sequential introduction of two different electrophiles based on this method was also achieved using a microflow system composed of four micromixers and four microtube reactors.
- Nagaki, Aiichiro,Takabayashi, Naofumi,Tomida, Yutaka,Yoshida, Jun-ichi
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supporting information; experimental part
p. 3937 - 3940
(2009/06/18)
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- Solvent-free, microwave-assisted synthesis of thiophene oligomers via suzuki coupling
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The purpose of this study was to obtain a rapid, efficient, and environmentally friendly methodology for the synthesis of highly pure thiophene oligomers. The solvent-free, microwave-assisted coupling of thienyl boronic acids and esters with thienyl bromides, using aluminum oxide as the solid support, allowed us to rapidly check the reaction trends on changing times, temperature, catalyst, and base and easily optimize the experimental conditions to obtain the targeted product in fair amounts. This procedure offers a novel, general, and very rapid route to the preparation of soluble thiophene oligomers. Thus, for example, quaterthiophene was obtained in 6 min by reaction of 2-bromo-2,2′-bithiophene with bis(pinacolato)diboron (isolated yield 65%), whereas quinquethiophene was obtained in 11 min by reaction of dibremoterthiophene with thienylboronic acid (isolated yield 74%). The synthesis of new chiral 2,2′-bithiophenes is reported. The detailed analysis of the byproducts of some reactions allowed us to elucidate a few aspects of reaction mechanisms. While the use of microwaves proved to be very convenient for the coupling between conventional thienyl moieties, the same was not true for the coupling of thienyl rings to thienyl-S,S-dioxide moieties. Indeed, in this case, the targeted product was obtained in low yields because of the competitive, accelerated, Diels-Alder reaction that affords a variety of condensation products.
- Melucci, Manuela,Barbarella, Giovanna,Sotgiu, Giovanna
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p. 8877 - 8884
(2007/10/03)
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- Novel nucleoside analogues with fluorophores replacing the DNA base
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We describe the preparation and fluorescence properties of a set of new nucleosides in which a known hydrocarbon or oligothiophene fluorophore replaces the DNA base at C(1) of the deoxyribose moiety (see 3af). These compounds are potentially useful as pro
- Straessler, Christoph,Davis, Newton E.,Kool, Eric T.
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p. 2160 - 2171
(2007/10/03)
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- SYNTHESIS AND (13)C NMR CHARACTERIZATION OF SOME π-EXCESSIVE HETEROPOLYAROMATIC COMPOUNDS
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Several ?-excessive heteropolyaromatic compounds, which contain furan and thiophen ring and are possible antifungal agents, have been synthesized in good yields according to two general methods.The first method has been used to prepare compounds possessing thiophens linked by their 2- and 5-positions, such as the ter-aryls 2b, 2d and 2a.Two precursors of these compounds have been obtained either by the Glaser reaction, or using a novel Pd-mediated reaction.The second method, which consists of the Ni- or Pd-catalyzed heteroarylation of heteroarene halides via cross-coupling with heteroaryl Grignard reagents or zinc halides, has been used to prepare the bi-aryls 1a-e, which contain two heteroaromatic units, and the ter-aryl 2c.Compound 1e has been also prepared starting from 2-(2-thienyl)furan (1c) by selective lithiation, followed by bromination.The (13)C NMR signals of 1a-e and 2a-d have been assigned on the basis of the literature data and by relaxation measurements.Relaxation data have been also used to obtain qualitative informations on the conformational equilibria of the bi-aryls 1a, 1c and the ter-aryls 2a-d.
- Carpita, Adriano,Rossi, Renzo,Veracini, Carlo Alberto
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p. 1919 - 1930
(2007/10/02)
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- PALLADIUM-CATALYZED SYNTHESES OF BI- AND TER-THIOPHENES
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Several heteropolyaromatic compounds containing thiophen rings, of general formula 2, 3, and 5, which are possible antifungal agents, have been synthesized in good yields by Pd-catalyzed reactions.In particular, cross-coupling reactions between 2- or 3-thienylmagnesium bromide and dibromothiophens of general formula 8 in the presence of catalytic amounts of PdCl2, have been used to prepare three isomers (2a, 2b, and 2c) of the naturally occurring 2,2':5',2"-terthiophen, 1, as well as several bromobithienyls of general formula 3.An analogous procedure has been employed for the regioselective synthesis of 3'-bromo-2,2':5',2"-terthiophen, 4, starting from 2-thienylmagnesium bromide, 7a, and 2,3,5-tribromothiophen, 8.On the other hand, heterocyclic esters of general formula 5, which are not readily accessible using conventional organic methods, have been conveniently prepared by Pd-catalyzed ethoxycarbonylation of bromobithienyls 3 under mild experimental conditions.A short synthesis of 5'-(1-propynyl)-2,2'-bithienyl-5-carboxylic acid, 6, a compound isolated from the roots of Arctium lappa, shows the efficacy of the reported Pd-catalyzed reactions.
- Carpita, Adriano,Rossi, Renzo
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p. 575 - 584
(2007/10/02)
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- REACTIONS OF WITH ARYL HALIDES. A NEW SOURCE OF ARYL RADICALS
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The complex (dppe = Ph2PCH2CH2PPh2) reacts with aryl halides to give molybdenum chloride complexes and arylation products of the aromatic nucleus, which are typical of homolytic aromatic substitution.The results of experiments carried out directly with MoCl5 and Na(Hg) in the presence of PPh3 or dppe confirm the essential role of the chelating diphosphine in favouring aromatic substitution instead of aryl coupling.The molybdenum complex was also caused to react with heteroaryl halides.In accord with a homolytic mechanism, selectivity towards the o-substituted isomers appears to be a general feature of these reactions.
- Minzoni, Ferruccio,Nardelli, Mario,Pelizzi, Corrado,Predieri, Giovanni
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p. 221 - 224
(2007/10/02)
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