- Improved synthesis of a terthiophene-based monomeric ligand that forms a highly active polymer for the carbon dioxide reduction
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Background: The carbon-dioxide reduction to obtain important chemicals such as fuels is a topic of high current interest. Recently, monomeric thiophenes and terthiophenes linked to a bipyridine ligand were designed and their polymeric films achieved very high turnover numbers during electrocatalytic CO2 reduction. In this paper we improved the protocol to access the ligand that shows the best performances, in view of opening the way to a general method to obtain side-functionalized terthiophenes. Methods: Several reactions were attempted to improve the synthetic pathway. Different approaches were attempted to convert the 3-bromothiophene into its 3-iodo analog and to brominate it to obtain the 2,5-dibromo-3-iodothiophene. The synthetic pathway was completed by using Pd-catalyzed crosscoupling reactions such as Sonogashira and Suzuki. The removal of a trimethylsilyl protection was attempted by common methods. However, with the use of a one-pot reaction, both the alkyne deprotection and the final Sonogashira coupling were performed as the key point of the pathway to obtain the final product. Results: The key intermediate 2,5-dibromo-3-iodothiophene was obtained by a CuI assisted electrophilic aromatic substitution, followed by a bromination with NBS in ethyl acetate. This compound was reacted with TMS-acetylene to obtain the ((2,5-dibromothiophen-3-yl)ethynyl)trimethylsilane which, by a Suzuki reaction, afforded the ([2,2':5',2''-terthiophen]-3'-ylethynyl)trimethylsilane. Using a onepot reaction for the last step, the deprotection of the TMS-protected alkyne and its coupling with 4- bromo-2,2'-bipyridine was accomplished easily. A final 52% yield was achieved over 5 steps. Conclusion: The ligand 4-([2,2':5',2''-terthiophen]-3'-ylethynyl)-2,2'-bipyridine was prepared in a 52% yield, over 5 steps, improving the previous protocol (17% yield over 4 steps). The rhenium complex of this ligand is still under study for CO2 reduction. This novel protocol can be used to produce a series of analog terthiophene monomers bearing side-attached ligands.
- Quagliotto, Pierluigi,Prosperini, Simona,Viscardi, Guido
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- A facile synthesis of aryl iodides via potassium aryltrifluoroborates
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Aryl- and heteroaryltrifluoroborates are rapidly converted to aryl and heteroaryl iodides under mild conditions using sodium iodide in the presence of mild oxidizing agents.
- Kabalka, George W.,Mereddy, Arjun R.
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- Synthesis of N-Substituted Condensed Tetrahydropyridine-Based Enaminones via Palladium-Catalyzed Intramolecular C–N Cross-coupling
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A number of β-enaminones with secondary amino group (alkyl, cyclopropyl, and aryl) were prepared from corresponding β-diketones. Two general protocols for their palladium-catalyzed intramolecular C–N cross-coupling were established to give corresponding N-substituted condensed tetrahydropyridines in good yields. The methodology is applicable for a wide variety of structural motifs. The work also extends the applicability of novel, recently established, palladium precatalysts to new substrates.
- Dou?ová, Hana,R??i?ková, Zdeňka,?im?nek, Petr
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- Selective metallation of 3-halothiophenes: Practical methods for the synthesis of 2-bromo-3-formylthiophene
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Selective lithiation of 3-bromothiophene was accomplished under controlled conditions without formation of undesired thienyllithium compounds. A thienyl Grignard reagent derived from 2-bromo-3-iodothiophene was transformed into 2-bromo-3-formylthiophene in high selectivity by formylation with dimethylformamide (DMF) at optimal reaction temperature. Copyright Taylor & Francis Group, LLC.
- Sonoda, Motohiro,Kinoshita, Shoko,Luu, Thanh,Fukuda, Hiroshi,Miki, Koji,Umeda, Rui,Tobe, Yoshito
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- Incorporation of perfluorohexyl-functionalised thiophenes into oligofluorene-truxenes: Synthesis and physical properties
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Oligofluorene-functionalised truxenes containing perfluorohexylthiophene units at the terminal positions on the arms were synthesised, and their optical and electrochemical properties were investigated to determine the effect that the perfluorohexylthiophene unit has on the HOMO and LUMO properties of the oligomers. By synthesising a molecule with longer oligofluorene arms the effects of the perfluorohexylthiophene unit on larger oligomers was explored. The effect of steric hindrance from the perfluorohexyl chain was also evaluated by altering the position of the chain on the thiophene moiety.
- Thomson, Neil,Kanibolotsky, Alexander L.,Cameron, Joseph,Tuttle, Tell,Findlay, Neil J.,Skabara, Peter J.
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- Impact of pendant 1,2,3-triazole on the synthesis and properties of thiophene-based polymers
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π-Conjugated moieties are often attached to conjugated polymers to systematically alter their electronic properties. Herein, we report the synthesis and properties of a thiophene polymer bearing a triazole moiety in the third position. Through NMR-based quenching studies, we show that the placement of the triazole moiety alters reaction pathway of the Ni(0)-mediated Grignard metathesis polymerization possibly through chelation. When compared with a triazole on the main chain, the pendant triazole moiety acts as an electron donor and lowers the band gap of the polymer. The triazole moiety also does not hinder the packing of the conjugated backbone. We also show that the fluorescence of this polymer is quenched with PCBM, indicating its potential as a candidate for organic photovoltaic devices.
- Nagarjuna,Yurt, Serkan,Jadhav, Kedar G.,Venkataraman
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- Domino Direct Arylation and Cross-Aldol for Rapid Construction of Extended Polycyclic π-Scaffolds
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Five-membered aromatic heterocycles are a ubiquitous skeleton of π-conjugated organic compounds, and their incorporation requires synthetic protocols that are not easily industrially sustainable or scalable. Improved methodologies for their insertion into π-scaffolds are therefore necessary. We report an efficient and scalable protocol involving a one-pot cross-Aldol direct arylation reaction protocol for the rapid construction of thiophene- and furan-based π-extended organic materials.
- Nitti, Andrea,Bianchi, Gabriele,Po, Riccardo,Swager, Timothy M.,Pasini, Dario
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- Regioselective iodination of arenes using iodine/NaBO3· 4H2O system in ionic liquid
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A mild, efficient, and simple protocol was developed for iodination of arenes and heterocyclic compounds with molecular iodine catalyzed by sodium perborate in ionic liquid. The methodology offered iodoarenes in good to excellent yields at room temperature. The protocol proved to be highly selective, as a single isomer was formed exclusively in most of the substrates. Copyright Taylor & Francis Group, LLC.
- Bhilare, Sachin V.,Deorukhkar, Amol R.,Darvatkar, Nitin B.,Salunkhe, Manikrao M.
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- Copper-catalyzed conversion of aryl and heteroaryl bromides into the corresponding iodide
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An efficient method for the synthesis of aryl and heteroaryl iodides is described in this study. The reactions of aryl and heteroaryl bromides with potassium iodide proceeded smoothly in the presence of a copper catalyst under mild reaction conditions to produce the corresponding iodides in satisfactory to excellent yields.
- Feng, Xiujuan,Li, Lingyu,Yu, Xiaoqiang,Yamamoto, Yoshinori,Bao, Ming
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- Mild preparation of haloarenes by ipso-substitution of arylboronic acids with N-halosuccinimides
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Aryl and heteroaryl boronic acids react with N-iodosuccinimide and N-bromosuccinimide to give the corresponding iodo-and bromo- arenes in good to excellent yields. The reaction is usually highly regioselective and yields only the ipso-substituted product. Esters of arylboronic acids react similarly, but less readily.
- Thiebes, Christoph,Prakash, G. K. Surya,Petasis, Nicos A.,Olah, George A.
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- Room Temperature Stable 3-Lithiothiophene: a Facile Synthesis of 3-Functional Thiophenes
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3-Functionalized thiphenes were readily prepared by reacting electrophiles with 3-lithiothiophene at room temperature. 3-Lithiothiophene was found to be stable in hexane at room temperature.
- Wu, Xiaoming,Chen, Tian-An,Zhu, Lishan,Rieke, Reuben D.
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- Nucleophilic C-H Etherification of Heteroarenes Enabled by Base-Catalyzed Halogen Transfer
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We report a general protocol for the direct C-H etherification of N-heteroarenes. Potassium tert-butoxide catalyzes halogen transfer from 2-halothiophenes to N-heteroarenes to form N-heteroaryl halide intermediates that undergo tandem base-promoted alcohol substitution. Thus, the simple inclusion of inexpensive 2-halothiophenes enables regioselective oxidative coupling of alcohols with 1,3-azoles, pyridines, diazines, and polyazines under basic reaction conditions.
- Bandar, Jeffrey S.,Klaus, Danielle R.,Puleo, Thomas R.
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supporting information
p. 12480 - 12486
(2021/08/24)
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- Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations
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While halogenation is of key importance in synthesis and radioimaging, the currently available repertoire is largely designed to introduce a single halogen per molecule. This report makes the selective introduction of several different halogens accessible. Showcased here is the privileged stability of nontoxic aryl germanes under harsh fluorination conditions (that allow selective fluorination in their presence), while displaying superior reactivity and functional-group tolerance in electrophilic iodinations and brominations, outcompeting silanes or boronic esters under rapid and additive-free conditions. Mechanistic experiments and computational studies suggest a concerted electrophilic aromatic substitution as the underlying mechanism.
- Deckers, Kristina,Fricke, Christoph,Schoenebeck, Franziska
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supporting information
p. 18717 - 18722
(2020/08/25)
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- Cobalt-catalyzed preparation of arylindium reagents from aryl and heteroaryl bromides
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A cobalt-bathophenanthroline catalyst has been developed for the direct preparation of a variety of arylindium reagents from the corresponding aryl and heteroaryl bromides in the presence of indium metal and lithium chloride. The thus-formed arylindium reagents undergo efficient palladium-catalyzed cross-coupling reactions with aryl iodides, tolerating various functional groups including hydroxy and free amino groups.
- Adak, Laksmikanta,Yoshikai, Naohiko
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experimental part
p. 7563 - 7568
(2011/11/12)
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- Enhancing sensing of nitroaromatic vapours by thiophene-based polymer films
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Optical sensing, via fluorescence quenching, of nitroaromatic vapours using polythiophenes has received limited attention due to their rather low sensory response. We hypothesized that a dipolar 1,2,3-triazole moiety can enhance the interaction of DNT and TNT with the polymer in thin films and bulky side chains can decrease the chain packing in thin films resulting in enhanced analyte diffusion. Herein we show that thin films of thiophene-based polymers containing 1,2,3-triazole with appropriate alkyl side chains show enhanced fluorescence quenching in the presence of nitroaromatic vapours.
- Nagarjuna,Kumar, Abhishek,Kokil, Akshay,Jadhav, Kedar G.,Yurt, Serkan,Kumar, Jayant,Venkataraman
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scheme or table
p. 16597 - 16602
(2012/06/18)
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- Co-thermolysis: A one-pot synthetic method for novel 2-substituted-5- (trifluoromethoxy)thiophenes
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A new 'green' process to obtain trifluoromethoxylated compounds by a gas-phase method has been accomplished. Through it, new 2-substituted-5- (trifluoromethoxy)thiophenes have been obtained in moderate to good yields. Though the reaction occurs in the gas-phase and radicals are involved, an electron transfer mechanism is also postulated to explain the appearance of all detected products.
- Peláez,Argüello
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scheme or table
p. 5242 - 5245
(2010/11/03)
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- Synthesis of 2,3-Substituted Thienylboronic Acids and Esters
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A noncryogenic protocol for the synthesis of 2-substituted 3-thienylboronic acids and esters as well as 3-substituted 2-thienylboronic acids and esters has been developed. Electrophiles were introduced regiospecifically in the 2-position of 2,3-dibromothiophene and in the 3-position of 2-bromo-3-iodothiophene by halogen-magnesium exchange followed by quenching with electrophiles. Palladium-catalyzed borylation of the 2,3-substituted halothiophenes with pinacolborane and P(t-Bu)3 as ligand for Pd produced 9 and 10. The borylation protocol was tolerated by a range of functional groups; however, strongly electron-withdrawing substituents decreased the stability of the thienylboronic acids and esters.
- Christophersen, Claus,Begtrup, Mikael,Ebdrup, Soren,Petersen, Henning,Vedso, Per
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p. 9513 - 9516
(2007/10/03)
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- Photochemical Synthesis of Phenyl-2-thienyl Derivatives
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The irradiation (in benzene solution) of 5-bromo- and 5-iodo-thiophene-2-carbaldehyde or the corresponding methyl ketones furnishes the corresponding 5-phenyl derivatives.The same reactivity for other halogenothiophenes is reported: 3,5-dibromothiophene-2-carbaldehyde furnishes the 3-bromo-5-phenyl-2-thienyl derivative while the corresponding di-iodo compound yields 3,5-diphenylthiophene-2-carbaldehyde.In contrast, 5-acetyl-2,3-di-iodothiophene furnishes only the photosubstitution pruduct at C-5.Generally the iodine-containing compounds are more reactive and more stable under the reaction conditions than ones bearing bromine, in agreement with previous reports on the corresponding furan photochemistry.
- Antonioletti, Roberto,Auria, Maurizio D',Onofrio, Franco D',Piancatelli, Giovanni,Scettri, Arrigo
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p. 1755 - 1758
(2007/10/02)
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- The electroreduction of halogenated thiophenes
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Electroreduction of polyhalothiophenes results in the preferential reduction of the α-halogen atoms.Preparative electrochemical reduction of these compounds at controlled potential can be used to synthesize 2,3,4-trihalo, 3,4-dihalo, and 3-halothiophenes.Experimental conditions were developed under which these reductions could be done selectively, giving good yields of the desired products.Electroreduction of tetrabromothiophene can also lead to the formation of a polybromodithyenyl mercury compound.
- Gedye, Richard Neville,Sadana, Yoginder Nath,Leger, Raymond
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p. 2669 - 2672
(2007/10/02)
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- SYNTHESIS AND TRANSFORMATIONS OF SULFIDES OF THE THIOPHENE SERIES.
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Isomeric alkoxy(alkylthio)formylthiophenes were synthesized from 4-iodo-2-methoxythiophene, and the structures of the products of Vilsmeier formylation of 2-methoxy-5-methythiothiophene were confirmed.
- Gol'dfarb, Ya. L.,Kalik, M. A.,Zav'yalova, V. K.
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p. 126 - 132
(2007/10/02)
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- Preparation of a 3-thienylmalonic acid and the corresponding diesters
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Preparation of a 3-thienylmalonic acid or a diester thereof comprising reacting in a polar solvent in the presence of a copper (I) halide a thiophene compound of formula: STR1 wherein X=I or Br, R1 =H or a C1-4 alkyl group, R2 =H or a C1-2 alkyl group and R3 =H or a C1-2 alkyl group, with the proviso that R2 and R3 cannot be an alkyl group simultaneously, with a mono-deprotonated methylene compound of formula: STR2 wherein a cation is present and Z'=Z" is CN or COOR in which R is a C1-4 alkyl group, or Z'=CN and Z"=COOR' in which R' is a C1-2 alkyl group, followed by hydrolysis by methods known per se to get the corresponding free acid.
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