- Confirmation of Suzuki-Miyaura Cross-Coupling Reaction Mechanism through Synthetic Architecture of Nanocatalysts
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Despite widespread use of heterogeneous Pd catalysts in Suzuki-Miyaura coupling reactions, detailed roles of Pd, especially the nature of its active species, are still a topic of controversial debate. While some studies showed an active surface of Pd nanoparticles or nanoclusters acting heterogeneously, others claimed soluble Pd species leached from the metallic Pd to be active species which are homogeneous in nature. Besides, within the homogeneous mechanism, how the Pd leaches and promotes the cross-coupling reaction is then another question that needs to be addressed. It could be envisioned that if the soluble Pd species and solid-phase Pd are physically separated, the mechanism of Suzuki-Miyaura coupling could then be confirmed through examining the catalytic activity in different reaction regions. Herein we use microporous St?ber silica as a membrane to separate the soluble Pd species from solid Pd and conduct size-selective reactions which allow the passage of leaching Pd species, but not of reactants or products larger than the membrane aperture. With this strategy, we have been able to differentiate the surface reaction from the solution cross-coupling. We find that the leached Pd species are the only genuine catalytic intermediate in the cross-coupling reactions. We also confirm that oxidative addition of aryl halides to the solid Pd leads to leaching of the soluble Pd species which is necessary to promote Suzuki-Miyaura reactions.
- Sun, Bo,Ning, Lulu,Zeng, Hua Chun
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supporting information
p. 13823 - 13832
(2020/09/21)
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- CuO grafted triazine functionalized covalent organic framework as an efficient catalyst for C-C homo coupling reaction
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Designing of low cost catalytic system for new C-C bond formation reactions is very challenging in synthetic organic chemistry. Herein, we report a new copper oxide immobilized covalent organic framework (COF) material CuII-TRIPTA by grafting of CuO nanoparticles at the surface of a nitrogen rich porous COF material TRIPTA. TRIPTA has been synthesized through the extended Schiff base reaction between 2,4,6-triformylphloroglucinol and 1,3,5-tris-(4-aminophenyl) triazine. The COF as well as CuO loaded materials are characterized by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG) and EPR spectroscopic analyses. CuII-TRIPTA material has been successfully applied as heterogeneous nanocatalyst for the C-C homo-coupling reaction of phenylboronic acids to synthesise wide range of biaryl compounds under mild and eco-friendly conditions (60 °C, methanol solvent). Remarkably high specific surface area of CuII-TRIPTA (583 m2 g?1) and highly accessible catalytic sites in the 2D-hexagonal COF nano-architecture potentially makes it excellent catalyst in the C-C bond formation reaction, which is evident from the high TON of the catalyst in this reaction. The catalyst was recollected and reused till 6th cycles without any noticeable change of its catalytic activity, suggesting its high catalytic efficiency in this C-C bond formation reaction.
- Das, Sabuj Kanti,Krishna Chandra, Bijan,Molla, Rostam A.,Sengupta, Manideepa,Islam, Sk. Manirul,Majee, Adinath,Bhaumik, Asim
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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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- Green synthesis of stable Cu(0) nanoparticles onto reduced graphene oxide nanosheets: A reusable catalyst for the synthesis of symmetrical biaryls from arylboronic acids under base-free conditions
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Highly stable Cu(0) nanoparticles were synthesized on reduced graphene oxide (rGO) sheets using a cost-effective and green method. The synthesized Cu(0)-nanoparticle-rGO composites exhibit excellent catalytic activity for the synthesis of symmetrical biaryls from arylboronic acids under microwave irradiation. The reaction proceeds smoothly in base-free conditions with easy recovery and reuse of the catalyst. The methodology is compatible with various functional groups and provides an attractive protocol for the synthesis of symmetrical biaryls with very good yields. HRTEM, XPS and XRD analyses showed the catalyst to be recyclable. The Cu(0) nanoparticles are stable in the rGO nanosheets, and the particle size distribution and oxidation state of the Cu(0) nanoparticle remain the same after performing the chemical reaction.
- Hussain, Najrul,Gogoi, Pranjal,Azhaganand, Vedi Kuyil,Shelke, Manjusha V.,Das, Manash R.
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p. 1251 - 1260
(2015/02/19)
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- Pd-catalyzed chemo-selective mono-arylations and bis-arylations of functionalized 4-chlorocoumarins with triarylbismuths as threefold arylating reagents
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Cross-coupling reactions of differently substituted 4-chlorocoumarins were studied under palladium catalysis using triarylbismuths as threefold arylating reagents. The high reactivity of 4-chlorocoumarins was demonstrated delivering mono- and bis-arylation products in a chemo-selective manner. The reaction conditions employed are simple, robust and the threefold coupling reactivity of triarylbismuth reagents was witnessed with good to high yields in 2-4 h conditions. The utility of the methodology was explored in the synthesis of a few natural occurring neoflavones (3.27-3.30). In addition, the 4-arylcoumarin 3.1 product is a useful precursor for the preparation of (R)-tolterodine.
- Rao, Maddali L.N.,Kumar, Abhijeet
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p. 6995 - 7005
(2015/03/14)
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- Synthesis of substituted dihydrobenzofurans and bis-dihydrobenzofurans
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Several substituted dihydrobenzofurans and bis-dihydrobenzofurans were prepared in accepted yields from 4,4'-biphenyl via a series of reasonable transformations.
- Chang, Meng-Yang,Lee, Tein-Wei,Wu, Ming-Hao
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body text
p. 1607 - 1613
(2012/08/29)
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- Synthesis of unnatural amino acid derivatives via palladium-catalyzed 1,4-addition of boronic acids
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Aryl and alkenyl amino acid derivatives were synthesized by a palladium-catalyzed 1,4-addition of the corresponding boronic acids to 2-acetamidoacrylate.
- Ray, Devalina,Nyong, Abijah M.,Natarajan, Amarnath
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experimental part
p. 2655 - 2656
(2010/06/19)
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- Cobalt-catalyzed arylzincation of alkynes
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Cobalt(II) bromide catalyzes arylzincation of alkynes with arylzinc iodide·lithium chloride complexes in acetonitrile. The scope of the arylzincation is wide enough to use unfunctionalized alkynes, such as 6-dodecyne, as well as arylacetylenes. The inherent functional group compatibility of arylzinc reagents allows preparation of various functionalized styrene derivatives. The reaction is applicable to the efficient and stereoselective synthesis of a synthetic estrogen and its derivative.
- Murakami, Kei,Yorimitsu, Hideki,Oshima, Koichiro
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experimental part
p. 2373 - 2375
(2009/12/01)
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- Unsymmetrical three-dimensional macromolecules: Preparation and characterization of strongly dipolar dendritic macromolecules
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The preparation and characterization of a series of strongly dipolar monodisperse dendritic molecules ranging in molecular weight from 604 to 10 530 are described. The molecules are designed to achieve high dipole moments through the placement of electron
- Wooley, Karen L.,Hawker, Craig J.,Fréchet, Jean M. J.
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p. 11496 - 11505
(2007/10/02)
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- Aromatic tertiary amines, enamines, deoxybenzoins and benzils
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A novel synthesis of aromatic tertiary amines involves reacting an aromatic anil and an aromatic ether in a molar ratio of 1:1; adjusting the ratio to 2:1 produces novel enamines and by employing a two step process for enamine production, various unsymmetrically substituted enamines can be obtained which are readily hydrolyzed to corresponding deoxybenzoins which in turn are readily oxidized to benzils, the aromatic tertiary amines may be used to produce charge transport layers in xerography, while the benzils may be used to produce a variety of desired polymers.
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- Novel Synthesis of N,N-Diarylarylmethanamines from N-(Arylmethylene)arenamines and (Arylmethoxy)arenes
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Various N,N-diarylarylmethanamines were synthesized by the reaction of N-(arylmethylene)arenamines with (arylmethoxy)arenes in dimethylformamide solution in the presence of a strong base as a catalyst which is obtained in situ by reacting metallic sodium with this solvent.In general, the reaction may be depicted as the reduction of the imine and addition, on the original imino nitrogen atom, of the aryl group (of the aryloxy moiety) of the ether and presumably oxidation of the arylmethoxy group of the ether to its corresponding aldehyde.Side reactions and a proposed reaction mechanism are discussed.
- Paventi, Martino,Hay, Allan S.
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p. 5875 - 5882
(2007/10/02)
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