16303-58-5Relevant academic research and scientific papers
Efficient Homocoupling of Aryl- and Alkenylboronic Acids in the Presence of Low Loadings of [{Pd(μ-OH)Cl(IPr)} 2 ]
Ostrowska, Sylwia,Rogalski, Szymon,Lorkowski, Jan,Walkowiak, Jedrzej,Pietraszuk, Cezary
, p. 1735 - 1740 (2018)
NHC-palladium(II) complex [{Pd(μ-OH)Cl(IPr)} 2 ] (IPr = bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) catalyzes the oxidative coupling of a broad spectrum of aryl- and alkenylboronic acids at loadings down to 5 ppm. At the concentration of 0.05 mol% the catalyst permits an efficient reaction under base-free conditions.
Palladium-Catalyzed C-H Homocoupling of Thiophenes: Facile Construction of Bithiophene Structure
Masui, Kentaro,Ikegami, Haruka,Mori, Atsunori
, p. 5074 - 5075 (2004)
Palladium-catalyzed C-H homocoupling of thiophene derivatives takes place in the presence of silver(I) fluoride or acetate. A variety of bithiophenes are obtained in good to excellent yields. In particular, the reaction of 2-bromothiophene proceeds at room temperature to afford 5,5′-dibromo-2,2′-bithiophene, where the bromine atom is completely intact in the palladium-catalyzed reaction. XRD analysis reveals that silver fluoride is reduced to silver(0) during the reaction. Copyright
Conducting Polymers from Dimethyl-2,2'-bithiophenes
Krische, Bernd,Hellberg, Jonas,Lilja, Cristina
, p. 1476 - 1478 (1987)
Electrochemical oxidation of symmetrical dimethylbithiophenes with free α-positions yields electroactive polymers with excellent cycling ability.
Perfluorocyclopentadienyl Radical Derivative as an Organocatalyst for Oxidative Coupling of Aryl- and Thienylmagnesium Compounds under Atmospheric Oxygen
Korenaga, Toshinobu,Nitatori, Kaoru,Muraoka, Hiroki,Ogawa, Satoshi,Shimada, Kazuaki
, p. 4835 - 4839 (2018)
The oxidative homocoupling reaction of Grignard reagents in the presence of atmospheric oxygen molecules proceeded in the presence of a heptafluorotolyl-substituted perfluorocyclopentadienyl radical. The turnover number (TON) was over 30 for the coupling reactions of PhMgBr to give biphenyl. The organocatalyst could couple thienylmagnesium compounds to give bithiophene derivatives in up to 94% yield. Furthermore, a gram-scale synthesis of 6,6'-dimethoxybiphenyl-2,2'-diyl-bis(phosphonic acid diethyl ester) was demonstrated. Stabilization of the phenyl radical for the inhibition of the side reaction was also considered using DFT calculations.
Expanding tetra[2,3-thienylene]-based molecular muscles to larger [4n]annulenes
Marsella, Michael J.,Piao, Guangzhe,Tham, Fook S.
, p. 1133 - 1135 (2002)
The synthesis, X-ray structure, and predicted redox-induced conformational dynamics of a thiophene-fused [12]annulene is reported. Regiospecific halogenation of the thiophene ring system and transition-metal catalyzed cross-couplings are key elements in the synthetic strategy. It is predicted (B3LYP/6-31G*) that redox-induced conformational changes yield significant dimensional changes in this annulene, thus establishing it as a candidate for single molecule actuation.
Role of silver salts in palladium-catalyzed arene and heteroarene C-H functionalization reactions
Lotz, Monica D.,Camasso, Nicole M.,Canty, Allan J.,Sanford, Melanie S.
, p. 165 - 171 (2017)
Silver carboxylate salts are widely used as additives in palladium-catalyzed C-H functionalization reactions. However, the role of these silver additives is often not fully understood. This paper describes an investigation of the role of AgOPiv in the stoichiometric activation of C6F5H at a well-defined PdII complex as well as in the PdII-catalyzed oxidative dimerization of 2-alkylthiophenes. Both in situ NMR spectroscopy and H/D exchange studies of the reactions of C6F5H implicate a role for AgOPiv in the C-H cleavage event, generating Ag-C6F5 as an intermediate. The catalytic studies show similar trends despite the different conditions and substrates, suggesting that AgOPiv promotes a similar metalation of the thiophene in the catalytic transformations. This proposal is supported by DFT calculations, which show energetically feasible pathways for concerted metalation-deprotonation of both 2-methylthiophene and pentafluorobenzene at [Ag(OPiv)]2. These studies suggest that initial metalation of C-H substrates at AgI carboxylates should be considered as a plausible pathway in C-H functionalization reactions involving mixtures of Ag and Pd salts.
Studies on the Electronic Absorption Spectra of 2,2'-Bithienyl and Some of Its Derivatives. A Molecular Orbital Treatment
Abu-Eittah, Rafie H.,Al-Sugeir, Fakhreia A.
, p. 2126 - 2132 (1985)
The electronic absorption spectra of 2,2'-bithienyl and a number of its derivatives have been investigated.The predominant conformer as well as the polarity of the molecule were predicted from the spectrum.Molecular orbital calculations were performed on different conformers of 5-formyl-2,2'-bithienyl and the s-trans geometry proved to be the predominant conformer of the molecule.A good agreement is observed between calculated and observed transition energy and intensity.
An Exception to the Carothers Equation Caused by the Accelerated Chain Extension in a Pd/Ag Cocatalyzed Cross Dehydrogenative Coupling Polymerization
Xing, Liwen,Liu, Ji-Ren,Hong, Xin,Houk, Kendall N.,Luscombe, Christine K.
, p. 2311 - 2322 (2022/02/09)
The Carothers equation is often used to predict the utility of a small molecule reaction in a polymerization. In this study, we present the mechanistic study of Pd/Ag cocatalyzed cross dehydrogenative coupling (CDC) polymerization to synthesize a donor-acceptor (D-A) polymer of 3,3′-dihexyl-2,2′-bithiophene and 2,2′,3,3′,5,5′,6,6′-octafluorobiphenyl, which go counter to the Carothers equation. It is uncovered that the second chain extension cross-coupling proceeds much more efficiently than the first cross-coupling and the homocoupling side reaction (at least 1 order of magnitude faster) leading to unexpectedly low homocoupling defects and high molecular weight polymers. Kinetic analyses show that C-H bond activation is rate-determining in the first cross-coupling but not in the second cross-coupling. Based on DFT calculations, the high cross-coupling rate in the second cross-coupling was ascribed to the strong Pd-thiophene interaction in the Pd-mediated C-H bond activation transition state, which decreases the energy barrier of the Pd-mediated C-H bond activation. These results have implications beyond polymerizations and can be used to ease the synthesis of a wide range of molecules where C-H bond activation may be the limiting factor.
Sterically controlled C-H/C-H homocoupling of arenes: Via C-H borylation
Pei, Xiaocong,Zhou, Guan,Li, Xuejing,Xu, Yuchen,Panicker, Resmi C.,Srinivasan, Rajavel
supporting information, p. 5703 - 5707 (2019/06/19)
A mild one-pot protocol for the synthesis of symmetrical biaryls by sequential Ir-catalyzed C-H borylation and Cu-catalyzed homocoupling of arenes is described. The regiochemistry of the biaryl formed is sterically controlled as dictated by the C-H borylation step. The methodology is also successfully extended to heteroarenes. Some of the products obtained by this approach are impossible to obtain via the Ullmann or the Suzuki coupling protocols. Finally, we have shown a one-pot sequence describing C-H borylation/Cu-catalyzed homocoupling/Pd-catalyzed Suzuki coupling to obtain π-extended arene frameworks.
Microwave-assisted, ligand-free, direct C-H arylation of thiophenes in biomass-derived γ-valerolactone
Tabasso, Silvia,Calcio Gaudino, Emanuela,Rinaldi, Laura,Ledoux, Audrey,Larini, Paolo,Cravotto, Giancarlo
, p. 9210 - 9215 (2017/08/29)
The Pd-catalyzed C-H arylation of heterocycles with aryl halides is a straightforward and more environmentally-friendly route to the synthesis of well-defined, pi-conjugated polymers for challenging applications in electronic devices. Although this type of transformation is more atom efficient than cross-couplings, it still poses environmental issues in the form of reaction media and the use of phosphine ligands. A procedure for the C-H arylation of thiophenes, with a substantially improved environmental impact, and a promising application of this protocol to the synthesis of regioregular polythiophenes are reported in this work. γ-Valerolactone (GVL), a non-toxic biomass-derived solvent, has been used in this phosphine-free microwave-assisted process and replaces commonly used dipolar aprotic media. Activated aryl bromides gave arylthiophenes in good yields, while iodides were used and pivalic acid was added when electron-withdrawing groups were present. The reaction was also extended to C-H (hetero)arylation polycondensation and a high molecular weight poly(3-hexyl)thiophene was obtained, using low Pd loading, in high yields and good regioregularity in short reaction times. Computational studies have shed light on GVL's role as a ligand in the catalytic system.
