- CpRhIII-Catalyzed Allyl-Aryl Coupling of Olefins and Arylboron Reagents Enabled by C(sp3)-H Activation
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Herein, we present a mild CpRhIII-catalyzed Suzuki-Miyaura-type allyl-aryl coupling of readily accessible arylboron reagents with a broad range of olefins. Allylic arylation was achieved without the need for prefunctionalized alkenes, and the general Heck-type reactivity between olefins and arenes was not observed. Mechanistic studies indicate that the reaction was enabled through the fast generation of a RhIII-allyl species via undirected C(sp3)-H activation. Moreover, the developed protocol was applied to the highly concise synthesis of the anti-inflammatory drug flurbiprofen.
- Knecht, Tobias,Pinkert, Tobias,Dalton, Toryn,Lerchen, Andreas,Glorius, Frank
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- Tailored quinones support high-turnover Pd catalysts for oxidative C-H arylation with O2
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Palladium(II)-catalyzed carbon-hydrogen (C-H) oxidation reactions could streamline the synthesis of pharmaceuticals, agrochemicals, and other complex organic molecules. Existing methods, however, commonly exhibit poor catalyst performance with high palladium (Pd) loading (e.g., 10 mole %) and a need for (super)stoichiometric quantities of undesirable oxidants, such as benzoquinone and silver(I) salts. The present study probes the mechanism of a representative Pd-catalyzed oxidative C-H arylation reaction and elucidates mechanistic features that undermine catalyst performance, including substrate-consuming side reactions and sequestration of the catalyst as an inactive species. Systematic tuning of the quinone cocatalyst overcomes these deleterious features. Use of 2,5-di-tert-butyl-p-benzoquinone enables efficient use of molecular oxygen as the oxidant, high reaction yields, and >1900 turnovers by the Pd catalyst.
- Salazar, Chase A.,Flesch, Kaylin N.,Haines, Brandon E.,Zhou, Philip S.,Musaev, Djamaladdin G.,Stahl, Shannon S.
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- Water as Solvent for Nickel-2,2′-Bipyridine-Catalysed Electrosynthesis of Biaryls from Haloaryls
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Reductive homocoupling of aryl halides into biaryls was achieved by electrolysis of aqueous emulsions, either in an undivided cell fitted with a sacrificial anode, or in a divided diaphragm cell, and in the presence of nickel-2,2′-bipyridine as catalyst. Reactions were also run in a filter-press cell.
- Raynal, Frederic,Barhdadi, Rachid,Perichon, Jacques,Savall, Andre,Troupel, Michel
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- Reactivity studies of cationic Au(III) difluorides supported by N ligands
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The reactivity of difluoro Au(III) cations supported by pyridine or imidazole ligands is reported. The Au(III)?F bond is found to be susceptible to metathesis by TMS reagents and reagents bearing acidic protons such as H?CC?Ph and HOAc. In the last case the reactions are slower than analogous reactions reported by other groups, where strong trans donors are present opposite the Au?F bond. This, coupled with the inability to effect metathesis on only one Au?F bond in our system, indicates that the trans effect is a key consideration in Au?F chemistry.
- Sharp-Bucknall, Lachlan,Barwise, Lachlan,Bennetts, Jason D.,Albayer, Mohammad,Dutton, Jason L.
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- Palladium-Catalyzed (4 + 4) Annulation of Silacyclobutanes and 2-Iodobiarenes to Eight-Membered Silacycles via C-H and C-Si Bond Activation
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Construction of eight-membered silacycles via Pd-catalyzed (4 + 4) annulation of silacyclobutanes and 2-iodobiphenyl derivatives is described. This strategy involves direct C-H and C-Si bond activation followed by a ring annulation and features low catalyst loading, ligand-free conditions, and readily available starting materials. Mechanistic studies revealed the involvement of five-membered palladacycle species in the reaction.
- Zhu, Ming-Hui,Zhang, Xiao-Wen,Usman, Muhammad,Cong, Hengjiang,Liu, Wen-Bo
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- Ligand promoted palladium-catalyzed homo-coupling of arylboronic acids
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Palladium-catalysed homo-coupling of arylboronic acids can be promoted by phosphine or phosphite ligands thereby offering a simple and efficient protocol for the synthesis of symmetrical bi-aryl molecules and their higher homologues.
- Wong, Man Shing,Zhang, Xiao Ling
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- Pre-transmetalation intermediates in the Suzuki-Miyaura reaction revealed: The missing link
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Despite the widespread application of Suzuki-Miyaura cross-coupling to forge carbon-carbon bonds, the structure of the reactive intermediates underlying the key transmetalation step from the boron reagent to the palladium catalyst remains uncertain. Here we report the use of low-temperature rapid injection nuclear magnetic resonance spectroscopy and kinetic studies to generate, observe, and characterize these previously elusive complexes. Specifically, this work establishes the identity of three different species containing palladium-oxygen-boron linkages, a tricoordinate boronic acid complex, and two tetracoordinate boronate complexes with 2:1 and 1:1 stoichiometry with respect to palladium. All of these species transfer their boron-bearing aryl groups to a coordinatively unsaturated palladium center in the critical transmetalation event.
- Thomas, Andy A.,Denmark, Scott E.
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- Palladium-catalyzed aryl group transfer from triarylphosphines to arylboronic acids
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A study of Pd-catalyzed arylation of arylboronic acids with triarylphosphines is presented. Various parameters of this transformation, such as the oxygen presence, choice of solvent, temperature, palladium source, bases and oxidants, were tested and the optimal conditions of the aryl transfer were determined. The effect of electron-withdrawing and electron-donating substituents on the aryl groups of both reactants was also investigated. The unusual transfer of the acetate group from Pd(OAc)2 to p-nitrophenylboronic acid in the presence of PAr3 is reported. A plausible mechanism of the Pd-catalyzed aryl group transfer from PAr3 to the arylboronic acid is proposed.
- Enright, Dale R.,Gogate, Akash R.,Smoliakova, Irina P.,Vasireddy, Purna C. R.
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- Competitive gold/nickel transmetalation
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Transmetalation is a key method for the construction of element-element bonds. Here, we disclose the reactivity of [NiII(Ar)(I)(diphosphine)] compounds with arylgold(i) transmetalating agents, which is directly relevant to cross-coupling catalysis. Both aryl-for-iodide and unexpected aryl-for-aryl transmetalation are witnessed. Despite the strong driving force expected for Au-I bond formation, aryl scrambling can occur during transmetalation and may complicate the outcomes of attempted catalytic cross-coupling reactions.
- Austen, Brady J. H.,Demchuk, Mitchell J.,Drover, Marcus W.,Nelson, David J.,Zurakowski, Joseph A.
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supporting information
p. 68 - 71
(2021/12/29)
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- Pd-catalyzed oxidative homocoupling of arylboronic acids in WEPA: A sustainable access to symmetrical biaryls under added base and ligand-free ambient conditions
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Symmetrical and unsymmetrical biaryls comprises a diverse class of biologically eloquent organic compounds. We herein report, a quick and eco-friendly protocol for the synthesis of biaryls by an oxidative (aerobic) homocoupling of arylboronic acids (ABAs) using Pd(OAc)2 in water extract of pomogranate ash (WEPA) as an efficient agro-waste(bio)-derived aqueous (basic) media. The reactions were executed at ambient aerobic conditions in the absence of external base and ligand to result symmetrical biaryls in excellent yields. The use of renewable media with an effective exploitation of waste, short reaction times, excellent yields of products, easy separation of the products, unnecessating the external base, oxidant, ligand or volatile organic solvents and ambient reaction conditions are the vital insights of the present protocol.
- Appa, Rama Moorthy,Lakshmidevi, Jangam,Naidu, Bandameeda Ramesh,Venkateswarlu, Katta
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- Rapid gram-scale synthesis of Au/chitosan nanoparticles catalysts using solid mortar grinding
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Owing to the abundant functional groups present in the chitosan polymer, high density catalytic tiny gold particles with greater dispersion can be anchored on the chitosan powder using simple mortar and pestle. Chitosan-supported gold nanoparticles (NPs) with excellent control of size and shape were rapidly synthesized in gram-scale by solid-grinding without the need of any toxic solvents. The structure of catalysts and products was established by advanced instrumental and spectroscopic methods. The supported gold NPs functions as a heterogeneous catalyst for the homocoupling of phenylboronic acid and the aerobic oxidation of benzyl alcohol in water. The catalytic behaviour and activity of supported gold NPs was tuned/modulated by varying the ratio of chitosan polymer and gold precursor. Comparative studies showed that the solid chitosan supported gold catalyst exhibits superior catalytic activity and selectivity than the well known hydrophilic polymer-stabilized gold NPs catalysts prepared by the conventional solution-based methods.
- Reddy, K. Paul,Meerakrishna,Shanmugam,Satpati, Biswarup,Murugadoss
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p. 438 - 446
(2021/01/11)
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- Sustainable Synthesis of Biaryls Using Silica Supported Ferrocene Appended N-Heterocyclic Carbene-Palladium Complex
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Abstract: A novel silica supported ferrocene appended N-heterocyclic carbene-palladium complex (SilFemBenzNHC@Pd) has been prepared and characterized by using fourier transform infrared (FT-IR), fourier transform Raman (FT-Raman), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and energy dispersive X-ray analysis (EDX). This novel complex served as a robust heterogeneous catalyst for the synthesis of biaryls via homocoupling of aryl boronic acids under base-free conditions in water. Recyclability experiments were executed successfully for six successive runs. Graphic Abstract: [Figure not available: see fulltext.]
- Khanapure, Sharanabasappa,Pore, Dattaprasad,Jagadale, Megha,Patil, Vaishali,Rashinkar, Gajanan
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p. 2237 - 2249
(2021/01/11)
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- "benchtop" Biaryl Coupling Using Pd/Cu Cocatalysis: Application to the Synthesis of Conjugated Polymers
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Typically, Suzuki couplings used in polymerizations are performed at raised temperatures in inert atmospheres. As a result, the synthesis of aromatic materials that utilize this chemistry often demands expensive and specialized equipment on an industrial scale. Herein, we describe a bimetallic methodology that exploits the distinct reactivities of palladium and copper to perform high yielding aryl-aryl dimerizations and polymerizations that can be performed on a benchtop under ambient conditions. These couplings are facile and can be performed by simple mixing in the open vessel. To demonstrate the utility of this method in the context of polymer synthesis: polyfluorene, polycarbazole, polysilafluorene, and poly(6,12-dihydro-dithienoindacenodithiophene) were created at ambient temperature and open to air.
- Minus, Matthew B.,Moor, Sarah R.,Pary, Fathima F.,Nirmani,Chwatko, Malgorzata,Okeke, Brandon,Singleton, Josh E.,Nelson, Toby L.,Lynd, Nathaniel A.,Anslyn, Eric V.
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supporting information
p. 2873 - 2877
(2021/05/05)
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- Synthesis of biaryl compounds via Suzuki homocoupling reactions catalyzed by metal organic frameworks encapsulated with palladium nanoparticles
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Heterogeneous homocoupling reactions of phenylboronic acids were greatly accelerated via Suzuki homocoupling reactions. In this work, a tandem route was designed which firstly one part of phenylboronic acids reacted with iodine to form iodobenzenes, then another part of phenylboronic acids coupled with iodobenzenes to produce biaryl compounds. The tandem reaction were catalyzed by a bifunctional heterogeneous catalyst of metal organic frameworks encapsulated with palladium nanoparticles (Pd?MOFs). This strategy for forming symmetric C-C bond between benzene rings has obvious advantages such as high efficiency, easy separation, good recyclability and no addition of toxic halogenated benzene.
- Bao, Yan-Sai,Cui, Xin-Yu,Han, Zheng-Bo,Li, Xin,Tang, Hong,Yang, Ming,Zhang, Yu-Yang,Zhao, Kun,Zhou, Mei-Li
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- Porphyrin n-pincer pd(Ii)-complexes in water: A base-free and nature-inspired protocol for the oxidative self-coupling of potassium aryltrifluoroborates in open-air
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Metalloporphyrins (and porphyrins) are well known as pigments of life in nature, since representatives of this group include chlorophylls (Mg-porphyrins) and heme (Fe-porphyrins). Hence, the construction of chemistry based on these substances can be based on the imitation of biological systems. Inspired by nature, in this article we present the preparation of five different porphyrin, meso-tetraphenylporphyrin (TPP), meso-tetra(p-anisyl)porphyrin (TpAP), tetra-sodium meso-tetra(p-sulfonatophenyl)porphyrin (TSTpSPP), meso-tetra(m-hydroxyphenyl)porphyrin (TmHPP), and meso-tetra(m-carboxyphenyl)porphyrin (TmCPP) as well as their N-pincer Pd(II)-complexes such as Pd(II)-meso-tetraphenylporphyrin (PdTPP), Pd(II)-meso-tetra(p-anisyl)porphyrin (PdTpAP), Pd(II)-tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (PdTSTpSPP), Pd(II)-meso-tetra(m-hydroxyphenyl)porphyrin (PdTmHPP), and Pd(II)-meso-tetra(m-carboxyphenyl)porphyrin (PdTmCPP). These porphyrin N-pincer Pd(II)-complexes were studied and found to be effective in the base-free self-coupling reactions of potassium aryltrifluoroborates (PATFBs) in water at ambient conditions. The catalysts and the products (symmetrical biaryls) were characterized using their spectral data. The high yields of the biaryls, the bio-mimicking conditions, good substrate feasibility, evading the use of base, easy preparation and handling of catalysts, and the application of aqueous media, all make this protocol very attractive from a sustainability and cost-effective standpoint.
- Hanafiah, Marlia M.,Lakkaboyana, Sivarama Krishna,Lakshmidevi, Jangam,Marella, Ravi Kumar,Naidu, Bandameeda Ramesh,Prasad, Sana Siva,Venkateswarlu, Katta
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- Palladium nanoparticle supported on nitrogen-doped porous carbon: Investigation of structural properties and catalytic activity on Suzuki–Miyaura reactions
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Novel palladium-doped nanoporous carbon composite material obtained via thermolysis of amorphous zeolitic imidazolate framework (aZIF) was synthesized and used as an efficient catalyst on Suzuki–Miyaura cross-coupling reactions of aryl bromides. With this developed catalytic system, the Suzuki–Miyaura cross-coupling reaction was accomplished in aqueous solutions, and biaryls were obtained in good to excellent yields in a short reaction time. The APC-750@Pd catalyst was characterized by Fourier Transform Infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Eicroscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM), Thermal Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA), Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Brunauer–Emmett–Teller (BET) analysis tecniques. N-doped porous carbon material (NPC-1000) was synthesized by thermolysis from aZIF. Activated porous carbon material (APC-750) was fabricated via fused at 750°C with KOH from NPC-1000. The APC-750@Pd was obtained as a result of the interaction of APC-750 and PdCl2 in deionized water. The cross-coupling reaction of different aryl bromides with phenylboronic acid was investigated to show the potential of the APC-750@Pd in the Suzuki–Miyaura cross-coupling reactions. The APC-750@Pd catalyst could be recycled at least five times with a 15% loss of catalytic efficiency in this catalytic system.
- Bu?day, Nesrin,Alt?n, Serdar,Ya?ar, Sedat
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- Ligand and Base Free Synthesis of Biaryls from Aryl Halides in Aqueous Media with Recyclable Ti0.97Pd0.03O1.97 Catalyst
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Abstract: Facile protocol for the synthesis of biaryls from aryl halides in presence of magnesium metal without prior formation of organometallic intermediate has been exploited. Irrespective of aqueous medium, Ti0.97Pd0.03O1.97 catalyst supports C–C bond formation reaction in presence of metals rather than dehalogenation without any additives. Homocoupling of 16 different aryl halides furnished corresponding biphenyls in good yield with better functional group tolerance. The recovery of the catalyst was carried out by employing catalyst coated cordierite monolith up to 7th cycle with high yields. A new approach for the cross-coupling reaction is also attempted. Graphic Abstract: [Figure not available: see fulltext.]
- Prasanna,Bhat, Shrikanth K.,Usha,Hegde
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p. 3313 - 3322
(2021/03/04)
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- Reductive Coupling of Aryl Halides via C—H Activation of Indene
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This paper describes the first case of a reductive coupling reaction with indene, a non-heteroatom olefin used as a reducing agent. The scope of the substrate is wide. The homo-coupling, cross-coupling, and synthesis of 12 and 14-membered rings were realized. The control experiment, indene-product curve and density functional theory calculations showed that the η3-palladium indene intermediate was formed by C—H activation in the presence of cesium carbonate. We speculate that the final product was obtained through a Pd (IV) intermediate or aryl ligand exchange. In addition, we excluded the formation of palladium anion (Pd(0)?) intermediates.
- Zhang, Bo-Sheng,Yang, Ying-Hui,Wang, Fan,Gou, Xue-Ya,Wang, Xi-Cun,Liang, Yong-Min,Li, Yuke,Quan, Zheng-Jun
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p. 1573 - 1579
(2021/05/28)
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- Tandem Mn–I Exchange and Homocoupling Processes Mediated by a Synergistically Operative Lithium Manganate
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Pairing lithium and manganese(II) to form lithium manganate [Li2Mn(CH2SiMe3)4] enables the efficient direct Mn–I exchange of aryliodides, affording transient (aryl)lithium manganate intermediates which in turn undergo spontaneous C?C homocoupling at room temperature to furnish symmetrical (bis)aryls in good yields under mild reaction conditions. The combination of EPR with X-ray crystallographic studies has revealed the mixed Li/Mn constitution of the organometallic intermediates involved in these reactions, including the homocoupling step which had previously been thought to occur via a single-metal Mn aryl species. These studies show Li and Mn working together in a synergistic manner to facilitate both the Mn–I exchange and the C?C bond-forming steps. Both steps are carefully synchronized, with the concomitant generation of the alkyliodide ICH2SiMe3 during the Mn–I exchange being essential to the aryl homocoupling process, wherein it serves as an in situ generated oxidant.
- Uzelac, Marina,Mastropierro, Pasquale,de Tullio, Marco,Borilovic, Ivana,Tarrés, Màrius,Kennedy, Alan R.,Aromí, Guillem,Hevia, Eva
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supporting information
p. 3247 - 3253
(2020/12/11)
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- Pd-NHCs Enabled Suzuki-Miyaura Cross-Coupling of Arylhydrazines via C–N Bond Cleavage
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We describe a highly efficient protocol for cross-coupling of phenylhydrazines with arylboronic acids by Pd-NHCs under aerobic reaction condition. A series of well-defined Pd-NHCs complexes were evaluated and the relationship between the structure and the catalytic properties was investigated. It was disclosed that the Pd-PEPPSI-IPr proved to be the robust precatalyst, providing access to a range of (hetero)biaryls in good to excellent yields.
- Zeng, Xiao-Xiao,Li, Dong-Hui,Zhou, Zhen,Xu, Chang,Liu, Feng-Shou
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supporting information
(2021/03/01)
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- Identification of a Surprising Boronic Acid Homocoupling Process in Suzuki-Miyaura Cross-Coupling Reactions Utilizing a Hindered Fluorinated Arene
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The Suzuki-Miyaura cross-coupling reaction of 2-bromo-1,3-bis(trifluoromethyl)benzene with arylboronic acids was evaluated and determined to suffer from the formation of large amounts of boronic acid homocoupling products in conjunction with dehalogenation. Homocoupling product formation in this process likely occurs through a rare protonolysis/second transmetalation event rather than by the well-established mechanism requiring the involvement of O 2. The scope of this boronic acid homocoupling reaction was investigated and shown to predominate with electron-deficient arylboronic acids. Finally, a good yield of cross-coupling products could be obtained by employing dicyclohexyl(2′,6′-dimethoxybiphenyl-2-yl)phosphine (SPhos) as the ligand.
- Gargaro, Samantha L.,Dunson, Bre'Shon,Sieber, Joshua D.
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supporting information
p. 511 - 516
(2020/09/21)
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- Relevance of Single-Transmetalated Resting States in Iron-Mediated Cross-Couplings: Unexpected Role of σ-Donating Additives
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Control of the transmetalation degree of organoiron(II) species is a critical parameter in numerous Fe-catalyzed cross-couplings to ensure the success of the process. In this report, we however demonstrate that the selective formation of a monotransmetalated FeII species during the catalytic regime counterintuitively does not alone ensure an efficient suppression of the nucleophile homocoupling side reaction. It is conversely shown that a fine control of the transmetalation degree of the transient FeIII intermediates obtained after the activation of alkyl electrophiles by a single-electron transfer (SET), achievable using σ-donating additives, accounts for the selectivity of the cross-coupling pathway. This report shows for the first time that both coordination spheres of FeII resting states and FeIII short-lived intermediates must be efficiently tuned during the catalytic regime to ensure high coupling selectivities.
- Rousseau, Lidie,Touati, Nadia,Binet, Laurent,Thuéry, Pierre,Lefèvre, Guillaume
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p. 7991 - 7997
(2021/05/26)
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- Palladium Ion Catalysed Oxidative C–C Bond Formation Reactions in Arylboronic Acid: Application of Cordierite Monolith Coated Catalyst
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Abstract: Catalytic efficiency of palladium ion substituted in TiO2, Ti0.97Pd0.03O1.97 is successfully exploited for the oxidative homocoupling of arylboronic acid and oxidative Heck coupling reactions between arylboronic acid and olefins. The reaction protocol provides direct approach to synthesize biphenyls and cinnamates from moderate to good yield with good functional group tolerance. As a result, 11 symmetrical biaryls and 14 cinnamates were synthesized from readily available arylboronic acids. Ti0.97Pd0.03O1.97 powder catalyst is synthesized by solution combustion method and characterized by powder X-ray diffraction. The C–C bond formation reactions were carried out by catalyst cartridge method using Ti0.97Pd0.03O1.97 catalyst coated cordierite monolith. Coating of the catalyst on a cordierite monolith enhanced the applicability of the catalyst and made handling and recycling of the catalyst very easy. Catalyst was recovered and recycled for eight times in both homocoupling and oxidative Heck coupling reactions. The turnover number for both the reactions found to be 443 and 424, respectively. Graphic Abstract: [Figure not available: see fulltext.].
- Bhat, Shrikanth K.,Prasanna,Dasappa, Jagadeesh Prasad,Hegde
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p. 2911 - 2927
(2020/03/31)
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- Glucopyranoside-substituted imidazolium-based chiral ionic liquids for Pd-catalyzed homo-coupling of arylboronic acids in water
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Chiral ionic liquids (CILs) are widely used solvents and materials with prominent properties. Carbohydrate-derived imidazolium-based CILs represent a distinctive type of CILs possessing multiple chiral centers from natural chiral pool. Herein, a series of glucopyranoside-substituted imidazolium-based CILs (Glu-imi-CILs) were synthesized and evaluated as ligands for Pd-catalyzed homo-coupling reactions of arylboronic acids in water. The glucopyranoside substituent was instrumental for improving the catalytic activity of the resulting catalysts. Moreover, a Glu-imi-CIL with a free hydroxyl group for additional coordination was found to be the most efficient ligand. A series of symmetric biaryl compounds (13 examples) were synthesized from arylboronic acids by this method in high isolated yields (85?99percent).
- Huang, Zhiqiang,Kong, Lingfang,Li, Jing,Wu, Yue,Xue, Jun,Yuan, Yangyang,Zhou, Zhonggao
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- Synthesis of Enaminone-Pd(II) Complexes and Their Application in Catalysing Aqueous Suzuki-Miyaura Cross Coupling Reaction
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A series of Pd(II)-enaminone complexes, termed Pd(eao)2, have been synthesized and characterized. The investigation on the catalytic activities of these new Pd(II)-reagents has proved that the Pd(eao)2-1 possesses excellent catalytic activity for the Suzuki- Miyaura cross coupling reactions of aryl bromides/chlorides with aryl/vinyl boronic acids in the environmentally benign media of aqueous PEG400 at low loading (5 mol‰). The superiority of this Pd(II)-reagent to those commercial Pd(II) and Pd(0) catalysts in catalyzing the reactions has been confirmed by parallel experiments. What's more, Pd(eao)2-2 has been found as a practical catalyst for the homo-coupling reactions of aryl boronic acids.
- Fu, Leiqing,Cao, Xiaoji,Wan, Jie-Ping,Liu, Yunyun
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p. 254 - 258
(2020/01/25)
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- Efficient Pd-catalyzed oxidative homocoupling of arylboronic acids in aqueous NaClO
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An efficient, mild and practical method was developed for the synthesis of biaryls via the Pd-catalyzed oxidative homocoupling of aromatic/heteroaromatic boronic acids in aqueous NaClO.
- Li, Min-Xin,Tang, Yan-Ling,Gao, Hui,Mao, Ze-Wei
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supporting information
(2020/03/04)
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- Synthesis method of biphenyl compounds
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The invention discloses a synthesis method of biphenyl compounds. The synthesis method comprises the following steps: by using an aromatic boric acid as a reaction substrate and palladium as a catalyst, adding a catalytic amount of a phase transfer catalyst, reacting in a sodium hypochlorite water solution at 50 DEG C for 1-5 hours, carrying out oxidative coupling, and carrying out post-reaction treatment to obtain a target product biphenyl compound. The method has the characteristics of mild reaction conditions, simplicity in operation and purification, wide substrate application range, highyield, high reaction speed and the like, and has practicability.
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Paragraph 0098-0115
(2020/02/06)
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- A Bio-Inspired Magnetically Recoverable Palladium Nanocatalyst for the Ullmann Coupling reaction of Aryl halides and Arylboronic acids In Aqueous Media
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Palladium nanoparticles supported on polydopamine-coated iron oxide nanoparticles (Pd/Fe3O4@PDA) were found to catalyze the Ullmann homocoupling of a wide variety of aryl halides, arylboronic acids and aryldiazonium salts in aqueous media in the presence of randomly methylated β-cyclodextrin (RM-β-CD). The synthesized nanoparticles were characterized by techniques such as TEM, SEM, EDX, XPS, ICP-AES and XRD. The synthesized catalyst can be easily recovered magnetically and reused up to five cycles without any significant loss of activity. This is the first report demonstrating the use of magnetically recoverable catalyst for Ullmann homocoupling reactions of aryl halides, arylboronic acids and aryldiazonium salts in water.
- Dubey, Abhishek V.,Kumar, A. Vijay
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- Electrochemical Synthesis of Biaryls via Oxidative Intramolecular Coupling of Tetra(hetero)arylborates
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We report herein versatile, transition metal-free and additive-free (hetero)aryl-aryl coupling reactions promoted by the oxidative electrocoupling of unsymmetrical tetra(hetero)arylborates (TABs) prepared from ligand-exchange reactions on potassium trifluoroarylborates. Exploiting the power of electrochemical oxidations, this method complements the existing organoboron toolbox. We demonstrate the broad scope, scalability, and robustness of this unconventional catalyst-free transformation, leading to functionalized biaryls and ultimately furnishing drug-like small molecules, as well as late stage derivatization of natural compounds. In addition, the observed selectivity of the oxidative coupling reaction is related to the electronic structure of the TABs through quantum-chemical calculations and experimental investigations.
- Music, Arif,Baumann, Andreas N.,Spie?, Philipp,Plantefol, Allan,Jagau, Thomas C.,Didier, Dorian
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p. 4341 - 4348
(2020/03/04)
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- Exploring the coordination confinement effect of divalent palladium/zero palladium doped polyaniline-networking: As an excellent-performance nanocomposite catalyst for C-C coupling reactions
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A pre-formed catalyst Pd2+/PANI composite for C-C coupling reaction was synthesized by combining the self-stabilized dispersion polymerization method with the in-situ composite material. Experiments have confirmed that the relatively high reduced structure (75%) in the polyaniline carrier is more favorable for the coupling reaction. Raman spectroscopy, solid nuclear magnetic, and X-ray photoelectron spectroscopy were performed to characterize the structures. The pre-formed catalyst has uniform coordination of divalent palladium and nitrogen in different valence states of the carrier polyaniline, which shows a good synergistic effect in the catalytic Ullmann reaction, and greatly reduces the use of reducing agents such as hydrazine hydrate. Compared with other studies, we analyzed the catalytic reaction mechanism in detail through real-time online infrared and XPS characterization. The results show that the divalent palladium in the catalyst and the zero-valent palladium generated by the in-situ reaction synergistically promote the reaction, while the polyaniline support acts as a stabilizer and dispersant, which prevents the agglomeration of the metal particles and prolongs increased catalyst life. The prepared Pd2+/PANI composites will become the most attractive alternative to traditional organic materials due to their wide applicability, high catalytic activity, stable recycling and relatively low price. This work provides a new theoretical basis for the understanding of the essential driving force of PANI catalytic activity and the cognition of the micro mechanism of action.
- Liang, Yanping,Liu, Wanyi,Song, Manrong,Sun, Yanyan,Wang, Gang,Wu, Zhiqiang,Zhan, Haijuan
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p. 177 - 188
(2020/03/17)
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- Palladium/Sensory Component-Catalyzed Homocoupling Reactions of Aryl Halides
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A novel and efficient catalyst system was developed for homocoupling reactions of aryl halides. The catalyst system consists of Pd(OAc) 2and the peppery sensory component of tobacco leaves. This is the first time that a sensory component has been used in an organic reaction. Experiments using the catalyst system showed that the reactions proceeded smoothly under air in the absence of both an additional ligand and a reductant. Furthermore, the catalyst system can be applied to the coupling reactions of hetaryl iodides. Many functional groups (including a hydroxy group) are tolerated.
- Bai, Haixin,Bao, Fengyu,Chai, Guobi,Liu, Pengfei,Liu, Zhikai,Zhang, Haiyan,Zhang, Qidong
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supporting information
(2020/09/09)
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- The Cyclopropane Ring as a Reporter of Radical Leaving-Group Reactivity for Ni-Catalyzed C(sp3)-O Arylation
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The ability to understand and predict reactivity is essential for the development of new reactions. In the context of Ni-catalyzed C(sp3)-O functionalization, we have developed a unique strategy employing activated cyclopropanols to aid the design and optimization of a redox-active leaving group for C(sp3)-O arylation. In this chemistry, the cyclopropane ring acts as a reporter of leaving-group reactivity, since the ring-opened product is obtained under polar (2e) conditions, and the ring-closed product is obtained under radical (1e) conditions. Mechanistic studies demonstrate that the optimal leaving group is redox-active and are consistent with a Ni(I)/Ni(III) catalytic cycle. The optimized reaction conditions are also used to synthesize a number of arylcyclopropanes, which are valuable pharmaceutical motifs.
- Mills, L. Reginald,Monteith, John J.,Dos Passos Gomes, Gabriel,Aspuru-Guzik, Alán,Rousseaux, Sophie A. L.
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p. 13246 - 13254
(2020/09/01)
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- Mechanistic Insights into C(sp2)?C(sp)N Reductive Elimination from Gold(III) Cyanide Complexes
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A new family of phosphine-ligated dicyanoarylgold(III) complexes has been prepared and their reactivity towards reductive elimination has been studied in detail. Both, a highly positive entropy of activation and a primary 12/13C KIE suggest a late concerted transition state while Hammett analysis and DFT calculations indicate that the process is asynchronous. As a result, a distinct mechanism involving an asynchronous concerted reductive elimination for the overall C(sp2)?C(sp)N bond forming reaction is characterized herein, for the first time, complementing previous studies reported for C(sp3)?C(sp3), C(sp2)?C(sp2), and C(sp3)?C(sp2) bond formation processes taking place on gold(III) species.
- Genoux, Alexandre,González, Jorge A.,Merino, Estíbaliz,Nevado, Cristina
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supporting information
p. 17881 - 17886
(2020/08/19)
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- Cobalt-catalyzed C(sp2)?CN bond activation: Cross-electrophile coupling for biaryl formation and mechanistic insight
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Herein, we report a cross-electrophile coupling of benzonitrile derivatives and aryl halides with a simple cobalt-based catalytic system under mild conditions to form biaryl compounds. Even though the cobalt catalyst is able to activate the C(sp2)?CN bond alone, the use of the AlMe3 Lewis acid enhances the reactivity of benzonitriles and improves the cross-selectivity with barely any influence on the functional group compatibility. X-ray structure determination of an original low-valent cobalt species combined with catalytic and stoichiometric reactions reveals a catalytically active cobalt(I) species toward the aryl halide partner. On the other hand, experimental insights, including cyclic voltammetry experiments, suggest the involvement of a cobalt complex of a lower oxidation state to activate the benzonitrile derivative. Finally, density functional theory calculations support the proposed mechanistic cycle involving two low-valent cobalt species of different oxidation states to perform the reaction.
- Dorval, Céline,Tricoire, Maxime,Begouin, Jeanne-Marie,Gandon, Vincent,Gosmini, Corinne
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p. 12819 - 12827
(2020/11/18)
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- Oxidative Addition of Alkenyl and Alkynyl Iodides to a AuI Complex
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The first isolated examples of intermolecular oxidative addition of alkenyl and alkynyl iodides to AuI are reported. Using a 5,5′-difluoro-2,2′-bipyridyl ligated complex, oxidative addition of geometrically defined alkenyl iodides occurs readily, reversibly and stereospecifically to give alkenyl-AuIII complexes. Conversely, reversible alkynyl iodide oxidative addition generates bimetallic complexes containing both AuIII and AuI centers. Stoichiometric studies show that both new initiation modes can form the basis for the development of C?C bond forming cross-couplings.
- Bower, John F.,Cadge, Jamie A.,Russell, Christopher A.,Sparkes, Hazel A.
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supporting information
p. 6617 - 6621
(2020/03/13)
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- Aerobic Homocoupling of Arylboronic Acids Catalyzed by Regenerable Pd(II)@MIL-88B-NH2(Cr)
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A fast and operationally simple method for the aerobic homocoupling of arylboronic acids is described. The process is catalyzed by Pd(II) complexes supported on the metal-organic framework MIL-88B-NH2(Cr). The benefits of this approach include the use of a benign oxidant/solvent mixture at room temperature with catalytic amounts of base, easy recovery of the catalyst, and easy isolation of the products. Very high conversions and good yields were achieved for a variety of substrates, and the process was also carried out on a larger scale with the same efficiency. The catalyst was found to suffer deactivation due to progressive reduction and agglomeration of palladium into inactive metal clusters/particles. An innovative procedure for the oxidative redispersion and regeneration of the active Pd(II)@MOF species is presented.
- Valiente, Alejandro,Carrasco, Sergio,Sanz-Marco, Amparo,Tai, Cheuk-Wai,Bermejo Gómez, Antonio,Martín-Matute, Belén
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p. 3933 - 3940
(2019/05/22)
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- Photocatalyzed borylation using water-soluble quantum dots
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The synthesis of arylboronates by Sandmeyer-type reactions in the presence of water still remains a significant challenge. Herein, we report the use of water-soluble MPA-capped quantum dot (QD) photocatalysts for the borylation of diazonium salts in the presence of water. A biphasic system under mild acidic conditions remains critical to prevent decomposition and competitive disulphide bond formation. The present protocol offers a broader scope of substrates and borylating agents. Additionally, this catalytic system offers a significantly high turnover number (TON). The present methodology can effectively distinguish subtle reactivity differences between boronic acids and boronates. Mechanistic investigation suggests an excited-state electron transfer pathway.
- Chandrashekar, Hediyala B.,Maji, Arun,Halder, Ganga,Banerjee, Sucheta,Bhattacharyya, Sayan,Maiti, Debabrata
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supporting information
p. 6201 - 6204
(2019/06/07)
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- Synergistic Activities in the Ullmann Coupling of Chloroarenes at Ambient Temperature by Pd-Supported Calcined Ferrocenated La2O3
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Novel palladium-doped nanoparticles have been explored to serve as the first metal oxide-derived heterogeneous catalyst for Ullmann reaction of chloroarenes under mild condition (34?°C). This heterogeneous catalyst exhibited high catalytic activity towards the Ullmann homocoupling of chloroarenes into a series of useful symmetrically biaryl products with good to excellent yields in the presence of ethanol and NaOH, thereby leading to green and economical Ullmann reaction. The produced nanoparticles were successfully characterized by various techniques including PXRD, XPS, HRTEM, SEM-EDS, BET, TGA techniques, elemental mapping analysis and ICP-OES. Interestingly, based on characterization and experimental data, a reasonable mechanism has been proposed. Also, the formation of aryl methyl ketone as a by-product has been further confirmed by isotopic labelling experiments that the acetyl moiety is derived from ethanol. Moreover, the catalyst was stable and could be easily reused up to 5 times under atmospheric air without suffering significant loss in catalytic activity.
- Chumkaeo, Peerapong,Poonsawat, Thinnaphat,Meechai, Titiya,Somsook, Ekasith
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- Photocatalytic coupled redox cycle for two organic transformations over Pd/carbon nitride composites
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Heterogeneous photocatalysis offers a means for "green" organic transformations. Generally, photogenerated electrons and holes are not utilized simultaneously and effectively. Here we report a coupling approach to promote simultaneously two organic transformations of the Ullmann C-C coupling reaction and the value-added aromatic alcohol oxidation reaction in inert solvent and under anaerobic conditions using a carbon nitride based composite (Pd/CN-450) prepared by loading Pd nanoparticles (NPs) on CN-450 (N defect and O dopant co-modified g-C3N4 with high crystallinity). Upon photo-excitation of the photocatalyst, the activation of carbon-halogen bonds of the adsorbed aryl halides can be promoted by the photogenerated electrons on Pd NPs and the aromatic alcohols undergo dissociation and dehydrogenation, and finally can be oxidized by the captured photogenerated holes from CN-450 in the presence of a Br?nsted base. N defects, O doping, and improved crystallinity, controlled by changing the post-annealing temperature in molten salts, enhance the visible light absorption and improve charger carrier separation of the functionalized carbon nitride. The smaller size and high dispersity of Pd NPs give the higher surface area-to-volume ratio resulting in efficient adsorption and activation of reactant molecules on Pd NPs and allow for the effective interfacial interaction of CN-450 with Pd NPs for promoting electron transfer from CN-450 to Pd NPs. As a result, Pd/CN-450 displays a superior photocatalytic activity of the coupled reaction compared to Pd/g-C3N4 (Pd NP supported pristine g-C3N4). Moreover, the coupled reaction system has general applicability for various substrates and shows reusability.
- Jia, Qiaohui,Zhang, Sufen,Jia, Xiaoxia,Dong, Xiaoyang,Gao, Ziwei,Gu, Quan
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p. 5077 - 5089
(2019/10/05)
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- Ligand-free palladium catalyzed Ullmann biaryl synthesis: 'Household' reagents and mild reaction conditions
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A palladium catalysed Ullmann biaryl synthesis has been developed using hydrazine hydrate as the reducing reagent at room temperature. The combination of Pd(OAc)2 and hydrazine hydrate works smoothly for the coupling of both electron-rich and electron-deficient aryl iodides, as well as hetero-aryl iodides, leading to a wide range of biaryls in good to excellent yields. The reaction requires only 1 mol% Pd(OAc)2 and the in situ generated palladium naoparticles are found to be active catalysts.
- Gong, Xinchi,Wu, Jie,Meng, Yunge,Zhang, Yulan,Ye, Long-Wu,Zhu, Chunyin
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supporting information
p. 995 - 999
(2019/03/12)
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- Desulfurization of Diaryl(heteroaryl) Sulfoxides with Benzyne
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Two benzyne-enabled desulfurization reactions have been demonstrated which convert diaryl sulfoxides and heteroaryl sulfoxides to biaryls and desulfurized heteroarenes, respectively. The reaction accessing biaryls tolerates a variety of functional groups, such as halides, pseudohalides, and carbonyls. Mechanistic studies reveal that both reactions proceed via a common assembly process but divergent disassemblies of the generated tetraaryl(heteroaryl) sulfuranes.
- Chen, De-Li,Sun, Yan,Chen, Mengyuan,Li, Xiaojin,Zhang, Lei,Huang, Xin,Bai, Yihui,Luo, Fang,Peng, Bo
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supporting information
(2019/06/13)
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- Connecting Organometallic Ni(III) and Ni(IV): Reactions of Carbon-Centered Radicals with High-Valent Organonickel Complexes
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This paper describes the one-electron interconversions of isolable NiIII and NiIV complexes through their reactions with carbon-centered radicals (R?). First, model NiIII complexes are shown to react with alkyl and aryl radicals to afford NiIV products. Preliminary mechanistic studies implicate a pathway involving direct addition of a carbon-centered radical to the NiIII center. This is directly analogous to the known reactivity of NiII complexes with R?, a step that is commonly implicated in catalysis. Second, a NiIV-CH3 complex is shown to react with aryl and alkyl radicals to afford C-C bonds via a proposed SH2-type mechanism. This pathway is leveraged to enable challenging H3C-CF3 bond formation under mild conditions. Overall, these investigations suggest that NiII/III/IV sequences may be viable redox pathways in high-oxidation-state nickel catalysis.
- Bour, James R.,Ferguson, Devin M.,McClain, Edward J.,Kampf, Jeff W.,Sanford, Melanie S.
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supporting information
p. 8914 - 8920
(2019/06/13)
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- Are phosphines viable ligands for Pd-Catalyzed aerobic oxidation reactions? Contrasting insights from a survey of six reactions
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Phosphines are the broadest and most important class of ligands in homogeneous catalysis, but they are typically avoided in Pd-catalyzed aerobic oxidation reactions because of their susceptibility to oxidative degradation. Recent empirical reaction-development efforts have led to a growing number of Pd/phosphine catalyst systems for aerobic oxidative coupling reactions, but few of these studies have assessed the fate of the phosphine ligand. Here, we assess six different oxidative coupling reactions, including the homocoupling of boronic acids, amino- and alkoxycarbonylation reactions, intramolecular C-H annulation, and enantioselective Fujiwara-Moritani C-C coupling. The fate and role of the phosphine, analyzed by 31P NMR spectroscopy throughout the reaction time course in each case, varies in different reactions. In one case, the phosphine has an inhibitory effect and leads to lower selectivity relative to ligand-free conditions. In other cases, the phosphine ligands have a beneficial effect on the reaction but undergo oxidative decomposition in parallel with productive catalytic turnover. Inclusion of MnO2 in one of the reactions slows phosphine oxidation by catalyzing disproportionation of H2O2 and thereby supports productive catalytic turnover. Negligible oxidation of the chiral phosphine (S,S)-chiraphos is observed during the enantioselective C-C coupling reaction, due to strong chelation of the ligand to PdII. The results of this study suggest that phosphines warrant broader attention as ligands for Pd-catalyzed aerobic oxidation reactions, particularly by implementing strategies identified for ligand stabilization.
- Tereniak, Stephen J.,Landis, Clark R.,Stahl, Shannon S.
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p. 3708 - 3714
(2018/04/14)
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- Water-soluble superbulky (η6- p -cymene) ruthenium(ii) amine: An active catalyst in the oxidative homocoupling of arylboronic acids and the hydration of organonitriles
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A phosphine free water-soluble superbulky amine-ruthenium-arene complex (2) encompassing 2,6-bis(diphenylmethyl)-4-methylaniline was synthesised in good yield. 2 was characterized by FT-IR, 1H NMR, and 13C NMR spectroscopies, TGA and elemental analyses. The structure of 2 was confirmed by a single-crystal X-ray diffraction study. The ruthenium centre in 2 adopts the pseudo-octahedral geometry due to the η6-p-cymene ring and bulky aniline ligand along with two chloro groups. Besides, complex 2 was efficaciously employed as a catalyst in the hydration of organonitriles to amides. This reaction proceeds efficiently for a wide range of substrates in an environmentally benign medium and is an economically reasonable synthetic route to amides in good yields. In addition, 2 acts as an excellent catalyst in the oxidative homocoupling of arylboronic acids in water. A range of arylboronic acids undergo a homocoupling reaction in the presence of catalyst 2 to yield symmetrical biaryls in reasonable to good yields.
- Nirmala, Muthukumaran,Adinarayana, Mannem,Ramesh, Karupnaswamy,Maruthupandi, Mannarsamy,Vaddamanu, Moulali,Raju, Gembali,Prabusankar, Ganesan
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supporting information
p. 15221 - 15230
(2018/09/29)
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- Elucidating the Role of the Boronic Esters in the Suzuki-Miyaura Reaction: Structural, Kinetic, and Computational Investigations
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The Suzuki-Miyaura reaction is the most practiced palladium-catalyzed, cross-coupling reaction because of its broad applicability, low toxicity of the metal (B), and the wide variety of commercially available boron substrates. A wide variety of boronic acids and esters, each with different properties, have been developed for this process. Despite the popularity of the Suzuki-Miyaura reaction, the precise manner in which the organic fragment is transferred from boron to palladium has remained elusive for these reagents. Herein, we report the observation and characterization of pretransmetalation intermediates generated from a variety of commonly employed boronic esters. The ability to confirm the intermediacy of pretransmetalation intermediates provided the opportunity to clarify mechanistic aspects of the transfer of the organic moiety from boron to palladium in the key transmetalation step. A series of structural, kinetic, and computational investigations revealed that boronic esters can transmetalate directly without prior hydrolysis. Furthermore, depending on the boronic ester employed, significant rate enhancements for the transfer of the B-aryl groups were observed. Overall, two critical features were identified that enable the transfer of the organic fragment from boron to palladium: (1) the ability to create an empty coordination site on the palladium atom and (2) the nucleophilic character of the ipso carbon bound to boron. Both of these features ultimately relate to the electron density of the oxygen atoms in the boronic ester.
- Thomas, Andy A.,Zahrt, Andrew F.,Delaney, Connor P.,Denmark, Scott E.
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supporting information
p. 4401 - 4416
(2018/04/05)
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- Organic transformations catalyzed by palladium nanoparticles on carbon nanomaterials
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Abstract: An efficient C–C bond coupling reactions (Suzuki–Miyaura and Glaser) catalyzed by PdO/GO nano-catalyst is presented. In addition, PdO/MWCNT nano-catalyst-mediated domino one-pot synthesis of 2-alkyl/2-aryl benzofurans has been accomplished from 2-iodophenols and terminal alkynes. The formation of benzofurans proceeds through intermolecular Sonogashira reaction followed by intramolecular nucleophilic addition of internal hydroxyl group onto the acetylenic bond. The catalyst PdO/GO has been reused successfully, with nearly no loss of activity up to 5 cycles. Graphical Abstract: : Synopsis: An efficient PdO/GO and PdO/MWCNT nanocatalysts have been developed for C–C coupling reactions like Suzuki and Glaser coupling reactions, multi-catalytic one-pot synthesis of 2-aryl, 2-alkyl benzofurans staring from 2-iodophenols and terminal alkynes. The protocol involves formation of benzofuran derivatives, i.e., Sonogashira reaction followed by 2-ethynyl phenol cyclization. [Figure not available: see fulltext.]
- Lakshminarayana, Bhairi,Mahendar, Lodi,Chakraborty, Jhonti,Satyanarayana, Gedu,Subrahmanyam, Ch
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- Recyclable Pd/CuFe2O4 nanowires: A highly active catalyst for C-C couplings and synthesis of benzofuran derivatives
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Pd/CuFe2O4 nanowire-catalyzed cross coupling transformations are described. Notably, these reactions showed excellent functional group tolerance. Further, the protocol is applied to a one-pot synthesis of benzofurans via a Sonogashira coupling and intramolecular etherification sequence. The catalyst was reused and found to maintain its activity and stability.
- Lakshminarayana, Bhairi,Chakraborty, Jhonti,Satyanarayana,Subrahmanyam, Ch.
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p. 21030 - 21039
(2018/06/13)
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- Fast, Efficient and Low E-Factor One-Pot Palladium-Catalyzed Cross-Coupling of (Hetero)Arenes
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The homocoupling of aryl halides and the heterocoupling of aryl halides with either aryl bromides or arenes bearing an ortho-lithiation directing group are presented. The use of a Pd catalyst, in combination with t-BuLi, allows for the rapid and efficient formation of a wide range of polyaromatic compounds in a one pot procedure bypassing the need for the separate preformation of an organometallic coupling partner. These polyaromatic structures are obtained in high yields, in 10 min at room temperature, with minimal waste generation (E-factors as low as 1.5) and without the need for strict inert conditions, making this process highly efficient and practical in comparison to classical methods. As illustration, several key intermediates of widely used BINOL-derived structures are readily prepared.
- Pinxterhuis, Erik B.,Visser, Paco,Esser, Iwan,Gualtierotti, Jean-Baptiste,Feringa, Ben L.
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supporting information
p. 9452 - 9455
(2017/10/23)
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- WEPA: a bio-derived medium for added base, π-acid and ligand free Ullmann coupling of aryl halides using Pd(OAc)2
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A bio-derived sustainable medium based on water extract of pomegranate ash (WEPA) has, for the first time, been developed for the homocoupling of aryl halides under palladium-assistance. Avoiding the requirement of an external base, ligand and π-acid, the use of the proposed renewable medium offers remarkable attributes like wide substrate scope, good to nearly quantitative yields of biphenyls with exceptional chemoselectivity and scale up viability.
- Lakshmidevi, Jangam,Appa, Rama Moorthy,Naidu, Bandameeda Ramesh,Prasad, S. Siva,Sarma, Loka Subramanyam,Venkateswarlu, Katta
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supporting information
p. 12333 - 12336
(2018/11/30)
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- Nickel-Catalyzed Electrochemical Reductive Homocouplings of Aryl and Heteroaryl Halides: A Useful Route to Symmetrical Biaryls
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Due to their widespread presence in functional materials and pharmaceuticals, biaryls are of fundamental importance in organic chemistry. Methods for the synthesis of symmetrical biaryls generally involve both metallic reduction and transition-metal catalysis. In this work, we show that electroreduction can also constitute a very relevant way to achieve the nickel-catalyzed reductive synthesis of symmetrical biaryl compounds. Therefore, it is demonstrated that both aryl and heteroaryl halides undergo reductive coupling to furnish the corresponding symmetrical biaryls in fair to excellent yields. Reactions are performed under very mild conditions thus ensuring important functional group tolerance.
- Rahil, Rima,Sengmany, Stéphane,Le Gall, Erwan,Léonel, Eric
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p. 146 - 154
(2017/09/28)
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- Oxidative Addition, Transmetalation, and Reductive Elimination at a 2,2′-Bipyridyl-Ligated Gold Center
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Three-coordinate bipyridyl complexes of gold, [(κ2-bipy)Au(η2-C2H4)][NTf2], are readily accessed by direct reaction of 2,2′-bipyridine (bipy), or its derivatives, with the homoleptic gold ethylene complex [Au(C2H4)3][NTf2]. The cheap and readily available bipyridyl ligands facilitate oxidative addition of aryl iodides to the Au(I) center to give [(κ2-bipy)Au(Ar)I][NTf2], which undergo first aryl-zinc transmetalation and second C-C reductive elimination to produce biaryl products. The products of each distinct step have been characterized. Computational techniques are used to probe the mechanism of the oxidative addition step, offering insight into both the origin of the reversibility of this process and the observation that electron-rich aryl iodides add faster than electron-poor substrates. Thus, for the first time, all steps that are characteristic of a conventional intermolecular Pd(0)-catalyzed biaryl synthesis are demonstrated from a common monometallic Au complex and in the absence of directing groups.
- Harper, Matthew J.,Arthur, Christopher J.,Crosby, John,Emmett, Edward J.,Falconer, Rosalyn L.,Fensham-Smith, Andrew J.,Gates, Paul J.,Leman, Thomas,McGrady, John E.,Bower, John F.,Russell, Christopher A.
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p. 4440 - 4445
(2018/04/05)
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- A Copper-Catalyzed Reductive Defluorination of β-Trifluoromethylated Enones via Oxidative Homocoupling of Grignard Reagents
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An efficient copper-catalyzed reductive defluorination of β-trifluoromethylated enones via an oxidative homocoupling of Grignard reagents is reported. The reaction proceeded smoothly with a wide range of substrates, including the ones bearing aromatic heterocycles, such as furyl and thienyl ring systems in high yields (80-92%, except one example) under mild conditions. This provides a practical method for synthesis of gem-difluoroolefin ketones. It is also worth noting that this homocoupling process of Grignard reagents using β-trifluoromethylated enones as oxidizing reagents is effective for both the Csp2-Csp2 and Csp3-Csp3 bond formations, including for substrates whose β-hydride elimination of the corresponding transition metal alkyl complex is particularly facile, affording coupling products with high yields (83-95%), simultaneously.
- Wu, Xiaoting,Xie, Fang,Gridnev, Ilya D.,Zhang, Wanbin
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p. 1638 - 1642
(2018/03/23)
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- Ni-Catalyzed Carbon-Carbon Bond-Forming Reductive Amination
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This report describes a three-component, Ni-catalyzed reductive coupling that enables the convergent synthesis of tertiary benzhydryl amines, which are challenging to access by traditional reductive amination methodologies. The reaction makes use of iminium ions generated in situ from the condensation of secondary N-trimethylsilyl amines with benzaldehydes, and these species undergo reaction with several distinct classes of organic electrophiles. The synthetic value of this process is demonstrated by a single-step synthesis of antimigraine drug flunarizine (Sibelium) and high yielding derivatization of paroxetine (Paxil) and metoprolol (Lopressor). Mechanistic investigations support a sequential oxidative addition mechanism rather than a pathway proceeding via α-amino radical formation. Accordingly, application of catalytic conditions to an intramolecular reductive coupling is demonstrated for the synthesis of endo- and exocyclic benzhydryl amines.
- Heinz, Christoph,Lutz, J. Patrick,Simmons, Eric M.,Miller, Michael M.,Ewing, William R.,Doyle, Abigail G.
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p. 2292 - 2300
(2018/02/19)
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