- (η2-alkyne)methyl(dioxo)rhenium complexes as aldehyde-olefination catalysts
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Complexes CH3ReO2L (L = 2-butyne, 3-hexyne, diphenylacetylene) are catalysts for the olefination of aldehydes, using 4-nitrobenzaldehyde (4-nba) as the standard aldehyde and ethyldiazoacetate (eda) as the diazo compound. Spectroscopic studies including in situ 31P, 17O, 13C, and 1H NMR spectroscopy are used to elucidate the mechanism and the nature of the active species. One of the key steps of the mechanism is the rapid formation of phosphazine at the beginning of the cycle and its subsequent reaction with the metal dioxide complex to form the catalytically active carbene species. Copyright
- Santos, Ana M.,Romao, Carlos C.,Kuehn, Fritz E.
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- The Mizoroki-Heck reaction in mesoionic 1-butyl-3-methyltetrazolium-5-olate
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1-Butyl-3-methyltetrazolium-5-olate (1), a mesoionic compound, exists as a liquid at room temperature and can be used as a polar solvent for the Mizoroki-Heck reaction, wherein it has been proven to be a superior solvent to other solvents. The reaction of iodobenzene with ethyl acrylate in the presence of palladium acetate in mesoionic liquid 1 at 40 °C for 24 h gave ethyl cinnamate in 78% yield in the absence of ligands, while the use of other solvents, such as [bmim][BF4], [bmim][PF6], and DMF gave lower yields (43%, 37%, and 17%, respectively) under the same conditions. Heck-type coupling reactions of electron-deficient or electron-rich aryl iodides and bromobenzenes with olefins (15 examples, 7%–97%) were performed in 1. When a phosphine ligand was added to the reaction mixture, aryl bromides could be used, and the mesoionic liquid containing the catalysts could be reused at least five times.
- Araki, Shuki,Hirashita, Tsunehisa,Kurabayashi, Hideaki
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- Pd/Cu-Free Cobalt-Catalyzed Suzuki and Heck Using Green Bio-Magnetic Hybrid and DFT-Based Theoretical Study
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Abstract: Several highly efficient and magnetically recyclable cobalt catalytic systems were prepared using magnetic chitosan and some safe and available organic compounds (Co-ligand@MNPs/Ch). The structure of these nanocomposites was confirmed by various physicochemical techniques such as FT-IR, XRD, TGA, VSM, TEM, SEM, CHNS and ICP-OES. These nano composites exhibit remarkable catalytic efficiency for Suzuki and Heck cross-coupling reactions in mild and green reaction conditions. The facile accessibility of starting materials, possible performance in air and eco-friendly conditions are merits of our catalysts. In addition, to describe and go insight to role and effect of ligands present in these catalysts, electrostatic interactions, density functional theory (DFT) model in molecular method were employed. Graphic Abstract: [Figure not available: see fulltext.]
- Hajipour, Abdol R.,Khorsandi, Zahra,Ahmadi, Mehnoosh,Jouypazadeh, Hamidreza,Mohammadi, Bahareh,Farrokhpour, Hossein
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p. 2842 - 2850
(2021/02/01)
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- Design, synthesis and antitumor activity evaluation of Chrysamide B derivatives
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Marine natural products derived from special or extreme environment provide an important source for the development of anti-tumor drugs due to their special skeletons and functional groups. In this study, based on our previous work on the total synthesis and structure revision of the novel marine natural product Chrysamide B, a group of its derivatives were designed, synthesized, and subsequently of which the anti-cancer activity, structure-activity relationships and cellular mechanism were explored for the first time. Compared with Chrysamide B, better anti-cancer performance of some derivatives against five human cancer cell lines (SGC-7901, MGC-803, HepG2, HCT-116, MCF-7) was observed, especially for compound b-9 on MGC-803 and SGC-7901 cells with the IC 50 values of 7.88 ± 0.81 and 10.08 ± 1.08 μM, respectively. Subsequently, cellular mechanism study suggested that compound b-9 treatment could inhibit the cellular proliferation, reduce the migration and invasion ability of cells, and induce mitochondrial-dependent apoptosis in gastric cancer MGC-803 and SGC-7901 cells. Furthermore, the mitochondrial-dependent apoptosis induced by compound b-9 is related with the JAK2/STAT3/Bcl-2 signaling pathway. To conclude, our results offer a new structure for the discovery of anti-tumor lead compounds from marine natural products.
- Zhu, Longqing,Li, Junfang,Fan, Xiaohong,Hu, Xiaoling,Chen, Jinhong,Liu, Yonghong,Hao, Xiangyong,Shi, Tao,Wang, Zhen,Zhao, Quanyi
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- Asymmetric synthesis of piperidines using the nitro-Mannich reaction☆
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A method for the synthesis of functionalized piperidines containing 3 contiguous stereocentres in the 2-,3- and 4- positions uses a diastereoselective nitro-Mannich to control stereochemistry. The nitro-Mannich reaction between a β-aryl/heteroaryl substituted nitroalkanes and glyoxylate imine provides β-nitro-amines with good selectivity (70:30 to >95:5) for the syn, anti-diastereoisomers. Reductive cyclisation with BF3.OEt2 and Et3SiH gave, after purification, stereochemically pure piperidines in 19–57% yield for ten examples with different 4-aryl/heteroaryl substituents.
- Anderson, James C.,Bouvier-Israel, Eva,Rundell, Christopher D.,Zhang, Xiangyu
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- Asymmetric Synthesis of Functionalized 9-Methyldecalins Using a Diphenylprolinol-Silyl-Ether-Mediated Domino Michael/Aldol Reaction
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Substituted 9-methyldecalin derivatives containing an all carbon quaternary chiral center were synthesized with excellent enantioselectivity via an organocatalyst-mediated domino reaction. The first reaction is a diphenylprolinol silyl ether-mediated Michael reaction, and the second reaction is an intramolecular aldol reaction. The enantiomerically pure catalyst is involved in both reactions.
- Hayashi, Yujiro,Salazar, Hugo A.,Koshino, Seitaro
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supporting information
p. 6654 - 6658
(2021/09/11)
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- Synthesis and characterization of a new bis-NHC palladium complex and its catalytic activity in the Mizoroki–Heck reaction
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A new bis-N-heterocyclic carbene palladium complex, (C13H9N2F2)2PdCl2, is synthesized by a three-step reaction and characterized by 1H NMR and 13C NMR spectroscopy as well as by X-ray crystallography. This new bis-N-heterocyclic carbene palladium complex has excellent stability and is capable of efficiently catalyzing the Mizoroki–Heck coupling reaction of aryl halides with acrylates.
- Cui, Jin,Feng, Can,Liu, Cheng-Xin,Wang, Yu-Fang,Zhang, Ming-Jie
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p. 684 - 688
(2020/05/22)
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- Biogenic synthesis of palladium nanoparticles using Boswellia sarrata and their applications in cross-coupling reactions
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A facile and green route for biogenic synthesis of palladium nanoparticles (PdNPs) using aqueous extract of nontoxic and renewable Boswellia sarrata leaves is reported. The as-synthesized PdNPs were systematically characterized by using ultraviolet (UV)–visible spectroscopy, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The PdNPs were crystalline and cubic in nature with average particle size of ~6 nm and successfully employed as heterogeneous catalyst in the Suzuki–Miyaura and Mizoroki–Heck cross-coupling reactions. The PdNPs could be recycled up to five times with modest change in the catalytic activity.
- Arde, Satyanarayan M.,Rashinkar, Gajanan S.,Jadhav, Sanjay N.,Patil, Audumbar D.,Salunkhe, Rajashri S.
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- Promising new catalytic properties of a Co (II)-carboxamide complex and its derived Co3O4 nanoparticles for the Mizoroki-Heck and the Epoxidation reactions
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The new Co(II) - carboxamide complex (1) and Co3O4 nanoparticles (2), by way of thermal decomposition of (1) have been efficiently synthesised in the environment-friendly. X-ray diffraction reveals a slightly distorted octahedral coordination of cobalt (four nitrogens and two oxygens) in (1) and regular octahedral or tetrahedral ones (oxygens only) in (2). The investigation of (1) and (2) in the Mizoroki-Heck and epoxidation of alkens reactions showed them both to be powerful, green and inexpensive catalysts.
- Kiani, Mahsa,Bagherzadeh, Mojtaba,Meghdadi, Soraia,Fadaei-Tirani, Farzaneh,Babaie, Maryam,Schenk-Jo?, Kurt
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- Palladium Immobilized on 2,2′-Dipyridyl-Based Hypercrosslinked Polymers as a Heterogeneous Catalyst for Suzuki–Miyaura Reaction and Heck Reaction
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Abstract: 2,2′-Bipyridine was successfully integrated into the skeleton of hypercrosslinked polymers networks (HCPs-bipy) via Friedel–Crafts reaction and Scholl coupling reaction, and PdCl2 was locked in this network polymers by coordination with pyridine motif. The preparation of HCPs-bipy has the advantages of low cost, mild conditions, easy separation and high yield. FT-IR, TGA, N2 sorption, ICP, XPS, SEM, EDX and TEM was employed to characterize the structure and composition of the heterogeneous catalysts. The result indicates that HCPs-bipy-Pd possess high specific surface areas, large microporous volume, thermal stability, and highly dispersion of palladium species. HCPs-bipy-Pd can be applied in Suzuki–Miyaura reactions and Heck reactions as robust heterogeneous catalyst to afford high yield. The reusability test demonstrates that HCPs-bipy-Pd could be recovered and reused for at least five times without losing catalytic activity. Graphic Abstract: [Figure not available: see fulltext.].
- Liu, Cijie,Xu, Wei,Xiang, Dexuan,Luo, Qionglin,Zeng, Shunqin,Zheng, Lijuan,Tan, Yujie,Ouyang, Yuejun,Lin, Hongwei
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p. 2558 - 2565
(2020/03/23)
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- A de novo peroxidase is also a promiscuous yet stereoselective carbene transferase
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By constructing an in vivo-assembled, catalytically proficient peroxidase, C45, we have recently demonstrated the catalytic potential of simple, de novo-designed heme proteins. Here, we show that C45's enzymatic activity extends to the efficient and stereoselective intermolecular transfer of carbenes to olefins, heterocycles, aldehydes, and amines. Not only is this a report of carbene transferase activity in a completely de novo protein, but also of enzyme-catalyzed ring expansion of aromatic heterocycles via carbene transfer by any enzyme.
- Stenner, Richard,Steventon, Jack W.,Seddon, Annela,Anderson, J.L. Ross
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p. 1419 - 1428
(2020/01/28)
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- METHOD FOR THE SYNTHESIS AND PURIFICATION OF ARYL ACID ESTERS
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The general inventive concepts are directed to the discovery that certain aryl acids can be esterified under particular conditions to provide the resulting ester as a solid that precipitates in good yield from the reaction mixture. The esters may then be isolated and purified with relative ease. Accordingly, a method for the esterification, isolation, and purification of aryl acids is provided.
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Paragraph 0028
(2019/10/17)
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- Synthesis of new Pro-PYE ligands as co-catalysts toward Pd-catalyzed Heck-Mizoroki cross coupling reactions
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The present research work describes the synthesis of five new ligands containing pyridinium amine, [H2L1][OTf]2-[H2L5][I]2 from two new precursors, [P3Et][I] and [P2Me][CF3SO3]. The structure elucidations of the compounds were confirmed by multinuclear NMR (1H, 13C), FT-IR and by single crystal XRD techniques. Theoretical DFT studies were carried out to get better insight into the electronic levels and structural features of all the molecules. These synthesized new Pro-PYE ligands [H2L1][OTf]2-[H2L5][I]2 were found to be significantly active as co-catalysts for Pd(CH3CO2)2 toward Heck-Mizoroki coupling reactions with wide substrate scope in the order of [H2L1][OTf]2 ? [H2L2][OTf]2 > [H2L3][OTf]2 > [H2L4][OTf]2 > [H2L5][I]2.
- Munir, Naima,Masood, Sara,Liaqat, Faroha,Tahir, Muhammad Nawaz,Yousuf, Sammer,Kalsoom, Saima,Mughal, Ehsan Ullah,Sumrra, Sajjad Hussain,Maalik, Aneela,Zafar, Muhammad Naveed
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p. 37986 - 38000
(2019/12/03)
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- Palladium-melamine complex anchored on magnetic nanoparticles: A novel promoter for C-C cross coupling reaction
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A palladium-melamine complex deposited on Fe3O4@SiO2 nanoparticles (MNPs-Mel-Pd) was considered as an effective catalyst for C-C cross-coupling (Mirozoki-Heck) reaction. Surface and magnetic properties of the prepared core-shell hybrid nanocatalyst was characterized using Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, energy-dispersive X-ray, vibrating sample magnetometry, transmission and scanning electron microscopy techniques and ICP/OES analysis. It was found that the heterogeneous nanocatalyst could be recovered simply and reused numerous times without loss of its catalytic activity. The advantages of this new methodology are: isolation of highly pure products without chromatography techniques, reusability of the catalyst using a magnet, easy workup procedure and negligible leaching of palladium.
- Bodaghifard, Mohammad Ali
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- Sequential Palladium-Catalyzed Allylic Alkylation/retro-Dieckmann Fragmentation Strategy for the Synthesis of α-Substituted Acrylonitriles
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A straightforward synthesis of α-substituted acrylonitriles is described using 4-cyano-3-oxotetrahydro-thiophene (c-THT) as an acrylonitrile surrogate. This unprecedented two-step sequence featuring a palladium-catalyzed allylic alkylation (Pd-AA) and a retro-Dieckmann fragmentation provides a general entry into diversely substituted 1,4-dienes.
- Katsina, Tania,Sharma, Sachi Prem,Buccafusca, Roberto,Quinn, Derek J.,Moody, Thomas S.,Arseniyadis, Stellios
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supporting information
p. 9348 - 9352
(2019/11/20)
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- Spectral and crystallography studies of new palladacycle complexes with P,C- and C,C-donor ligands; Application of (OAL16) to optimizing the yield of Mizoroki-Heck reaction
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The new symmetrical diphosphonium salt [Ph2P(CH2)2PPh2(CH2C(O)C6H4Br)2] Br2 (S) was synthesized in the reaction of 1,2-bis (diphenylphosphino) ethane (dppe) and related ketone. Further treatment with NEt3 gave the symmetrical α-keto stabilized diphosphine ylide [Ph2P(CH2)2PPh2(CHC(O)C6H4Br)2] (Y1). The unsymmetrical α-keto stabilized diphosphine ylide [Ph2P(CH2)2PPh2(CHC(O)C6H4Br)] (Y2) was synthesized in the reaction of diphosphine in 1:1 ratio with 2.3′-dibromoacetophenone, then treatment with NEt3. The reaction of dibromo (1,5-cyclooctadiene)palladium (II), [PdBr2(COD)] with this ligand (Y1) in equimolar ratio gave the new C,C-chelated [PdBr2(Ph2P(CH2)2PPh2(C(H)C(O)C6H4Br)2)] (1) and with unsymmetrical phosphorus ylide [Ph2P(CH2)2PPh2C(H)C(O)C6H4Br] (Y2) gave the new P, C-chelated palladacycle complex [PdBr2(Ph2P(CH2)2PPh2C(H)C(O)Br)] (2). These compounds were characterized successfully by FT-IR, NMR (1H, 13C and 31P) spectroscopic methods and the crystal structure of Y1 and 2 were elucidated by single crystal X-ray diffraction. The results indicated that the complex 1 was C, C-chelated whereas complex 2 was P, C-chelated. These air/moisture stable complexes were employed as efficient catalysts for the Mizoroki-Heck cross-coupling reaction of several aryl chlorides, and the Taguchi method was used to optimize the yield of Mizoroki-Heck coupling. The optimum condition was found to be as followed: base; K2CO3, solvent; DMF and loading of catalyst; 0.005?mmol.
- Sabounchei, Seyyed Javad,Badpa, Khadijeh,Hashemi, Ali,Moniriyan, Faezeh,Gable, Robert W.
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- Palladium catalyst immobilized on functionalized microporous organic polymers for C-C coupling reactions
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Two microporous organic polymer immobilized palladium (MOP-Pd) catalysts were prepared from benzene and 1,10-phenanthroline by Scholl coupling reaction and Friedel-Crafts reaction, respectively. The structure and composition of the catalyst were characterized by FT-IR, TGA, N2 sorption, SEM, TEM, ICP-AES and XPS. MOP-Pd catalysts were found to possess high specific surface areas, large pore volume and low skeletal bone density. Moreover, the immobilized catalyst also had advantages, such as readily available raw materials, chemical and thermal stability, and low synthetic cost. The Pd catalyst is an effective heterogeneous catalyst for carbon-carbon (C-C) coupling reactions, such as the Heck reaction and Suzuki-Miyaura reaction, affording good to high yields. In these reactions, the catalyst was easily recovered and reused five times without significant activity loss.
- Xu, Wei,Liu, Cijie,Xiang, Dexuan,Luo, Qionglin,Shu, You,Lin, Hongwei,Hu, Yangjian,Zhang, Zaixing,Ouyang, Yuejun
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p. 34595 - 34600
(2019/11/11)
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- Pd-chelated 1,3,5-triazine organosilica as an active catalyst for Suzuki and Heck reactions
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Design of novel functional periodic mesoporous organosilica with molecular level control finds applications in several fields of energy and environmental research including adsorption, catalysis, nanotechnology, and energy harvesting. Herein we present a melamine (1,3,5-triazine) functionalized periodic mesoporous silica (MPMO) by self-assembly of N2,N4,N6-tris(3-(triethoxysilyl)propyl)-1,3,5-triazine-2,4,6-triamine (TTET) with tetraethylorthosilicate (TEOS) via cocondensation strategy. The TTET silsesquioxane precursor was synthesized by the condensation reaction between cyanuric chloride and 3-aminopropyl triethoxysilane. The resultant MPMO material serves as an effective solid chelating agent through amine and triazine functionalities for Pd(II) to provide Pd-MPMO. The Pd-MPMO material was thoroughly characterized by a small-angle XRD, HRTEM, N2 sorption, 13C CP-MAS NMR, 29Si CP-MAS NMR, and ICP analyses. The Pd-MPMO serves as an active catalyst for C–C bond formation reactions by Suzuki- and Heck cross-coupling methodologies under ligand- and cocatalyst-free conditions. Notably, the present catalytic protocol demonstrates a wide spectrum of substrate scope towards Suzuki coupling between aryl halides (I?, Br?, Cl?) and aryl boronic acids with high turn-over-number (TON) in aqueous phase under air ambience. Whereas for Heck-coupling reaction, the phenyl iodides furnished high TON than the other aryl halides. Investigation of Pd-leaching by a hot filtration test as well as reusability experiments confirms the true heterogeneous nature of present Pd-MPMO and its robustness in terms of substrate scope, catalyst stability, and durability.
- Elavarasan,Kala,Muhammad, Ibrahim,Bhaumik,Sasidharan
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- "water soluble" palladium nanoparticle engineering for C-C coupling, reduction and cyclization catalysis
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The use of Pd nanoparticles (Pd-NPs) to realize several important organic reactions allows efficient catalysis with low metal loading (1000 ppm), hence providing a greener catalytic system. However, to be truly green Pd-NPs need to be synthesized in a sustainable manner and be able to react in aqueous media in order to avoid the use of organic solvents. Here we describe an original and eco-friendly synthesis of Pd-NPs (using benign reactants and simple conditions) perfectly stable in water. Remarkably, this synthesis allows for control over their size and morphology by simply tuning the pH of the stabilizer. We then evaluate the catalytic efficiency of these Pd-NPs on six different model reactions (Suzuki Miyaura, Sonogashira, Heck, nitrophenol reduction and pentynoic cycloisomerization) in aqueous media. We show that the stabilizer structure influences the activity owing to its ability to promote the mass transfer of the organic substrates towards the NP surface in the aqueous environment. Finally, catalytic evaluations show that our nano-catalysts prepared in an eco-friendly manner are among the best catalysts described so far in the literature in each case, with high turnover frequencies reached with a low loading of palladium.
- Iben Ayad,Belda Marín,Colaco,Lefevre,Méthivier,Ould Driss,Landoulsi,Guénin
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supporting information
p. 6646 - 6657
(2019/12/26)
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- Boron-Catalyzed C?C Functionalization of Allyl Alcohols
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Tris(pentafluorophenyl)borane-catalyzed C?C bond functionalization of arylallyl alcohols using donor-acceptor carbenes is presented. The allylic hydroxyl group is found to assist the product formation by neighboring group participation providing a clue towards mechanistic understanding. This method can also be employed to effect homologation of allyl alcohols to homoallyl alcohols. Overall, this metal-free transformation presents a novel disconnection strategy towards carbon-carbon bond scission and formation. (Figure presented.).
- Rao, Santhosh,Kapanaiah, Raja,Prabhu, Kandikere Ramaiah
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supporting information
(2019/02/14)
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- One-pot synthesis of new N-(1-methylpyridin-4(1H)-ylidene)amine ligands for palladium-catalyzed heck coupling reaction
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A series of new derivatives of N -(1-methylpyridin-4(1 H) -ylidene)amines, [L1 ]–[L 5 ], were synthesized and characterized by FTIR, NMR, MS, and XRD analysis. These targeted compounds were synthesized by the melt reaction between N -methylated-4-chloropyridinium triflate and corresponding amines (1-naphthyl amine, o-ansidine, 2-nitroaniline, p-ansidine, and cyclohexyl amine) followed by the addition of sodium hydride in dichloromethane in the same pot. These highly electron-donating N -(1-methylpyridin-4(1 H) -ylidene)amine ligands considerably improve the catalytic activity of palladium acetate towards Heck–Mizoroki carbon–carbon cross-coupling reactions.
- Zafar, Muhammad,Zahra, Sabeen,Tahir, Muhammad,Mughal, Ehsan,Nazar, Muhammad,Rafique, Hummera
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- Pd(II)-NHDC-Functionalized UiO-67 Type MOF for Catalyzing Heck Cross-Coupling and Intermolecular Benzyne-Benzyne-Alkene Insertion Reactions
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A novel palladium N-heterocyclic bis-carbene dicarboxylate ligand (Pd-NHDC-H2L) was successfully synthesized. In addition, an Pd-NHDC-containing UiO-67 type MOF (UiO-67-Pd-NHDC) was prepared on the basis of a size-matched ligand mixture of biphenyl-4,4′-dicarboxylic acid/Pd-NHDC-H2L (9/1) and ZrCl4 under solvothermal conditions. The obtained UiO-67-Pd-NHC MOF can be a highly heterogeneous catalyst to promote Heck cross-coupling and intermolecular benzyne-benzyne-alkene insertion reactions.
- Wei, Yong-Liang,Li, Yue,Chen, Yun-Qi,Dong, Ying,Yao, Jia-Jia,Han, Xin-Yue,Dong, Yu-Bin
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supporting information
p. 4379 - 4386
(2018/04/25)
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- Fabrication of Pd/CuFe2O4 hybrid nanowires: A heterogeneous catalyst for Heck couplings
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The development of environmentally benign transformations is indispensable in organic synthesis. Herein, a hybrid heterogeneous catalyst, palladium(0) on copper ferrite nanowires, has been synthesized, characterized, and for the first time, employed in the Jeffrey Heck reaction between iodoarenes and allylic alcohols, and good to excellent yields have been obtained. In addition, the catalyst was found to be suitable for the usual Heck coupling. The nanocatalyst was recovered and reused up-to multiple runs without any noticeable loss of its catalytic activity.
- Lakshminarayana,Mahendar,Ghosal,Sreedhar,Satyanarayana,Subrahmanyam, Ch.
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p. 1646 - 1654
(2018/02/09)
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- Palladium on Polydopamine: Its True Potential in Catalytic Transfer Hydrogenations and Heck Coupling Reactions
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The application of Pd–polydopamine and magnetic Fe3O4@Pd–polydopamine catalysts in catalytic transfer hydrogenation reactions and the Heck arylation is reported. The reduction of a wide range of aromatic nitro-compounds bearing both electron-donating and -withdrawing substituents to the corresponding anilines could be efficiently performed, although the reduction of carbonyl compounds was found to be less general. In the latter case, only aromatic ketones could be reduced to the corresponding alcohols, whereas aldehyde substrates were unaffected, which may be owing to their reaction with the catalyst support leading to catalyst deactivation. By using magnetic Fe3O4@Pd–polydopamine system, facilitated catalyst recovery and reuse for five consecutive cycles without considerable loss of activity in nitro-group reduction. The efficiency of the catalyst in Heck reactions was comparable to that in transfer hydrogenation, however, no catalytic activity was observed upon reuse in this case, likely as a result of metal leaching. We also explored tandem Heck reaction/catalytic transfer hydrogenation sequences, however, the two reactions showed limited compatibility under the applied conditions.
- Kunfi, Attila,Szabó, Vivien,Mastalir, ágnes,Bucsi, Imre,Mohai, Miklós,Németh, Péter,Bertóti, Imre,London, Gábor
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p. 3236 - 3244
(2017/08/29)
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- Expanding the substrate scope of phenylalanine ammonia-lyase from: Petroselinum crispum towards styrylalanines
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This study focuses on the expansion of the substrate scope of phenylalanine ammonia-lyase from Petroselinum crispum (PcPAL) towards the l-enantiomers of racemic styrylalanines rac-1a-d-which are less studied and synthetically challenging unnatural amino acids-by reshaping the aromatic binding pocket of the active site of PcPAL by point mutations. Ammonia elimination from l-styrylalanine (l-1a) catalyzed by non-mutated PcPAL (wt-PcPAL) took place with a 777-fold lower kcat/KM value than the deamination of the natural substrate, l-Phe. Computer modeling of the reactions catalyzed by wt-PcPAL indicated an unproductive and two major catalytically active conformations and detrimental interactions between the aromatic moiety of l-styrylalanine, l-1a, and the phenyl ring of the residue F137 in the aromatic binding region of the active site. Replacing the residue F137 by smaller hydrophobic residues resulted in a small mutant library (F137X-PcPAL, X being V, A, and G), from which F137V-PcPAL could transform l-styrylalanine with comparable activity to that of the wt-PcPAL with l-Phe. Furthermore, F137V-PcPAL showed superior catalytic efficiency in the ammonia elimination reaction of several racemic styrylalanine derivatives (rac-1a-d) providing access to d-1a-d by kinetic resolution, even though the d-enantiomers proved to be reversible inhibitors. The enhanced catalytic efficiency of F137V-PcPAL towards racemic styrylalanines rac-1a-d could be rationalized by molecular modeling, indicating the more relaxed enzyme-substrate complexes and the promotion of conformations with higher catalytic activities as the main reasons. Unfortunately, ammonia addition onto the corresponding styrylacrylates 2a-d failed with both wt-PcPAL and F137V-PcPAL. The low equilibrium constant of the ammonia addition, the poor ligand binding affinities of 2a-d, and the non-productive binding states of the unsaturated ligands 2a-d within the active sites of either wt-PcPAL or F137V-PcPAL-as indicated by molecular modeling-might be responsible for the inactivity of the PcPAL variants in the reverse reaction. Modeling predicted that the F137V mutation is beneficial for the KRs of 4-fluoro-, 4-cyano- and 4-bromostyrylalanines, but non-effective for the KR process of 4-trifluoromethylstyrylalanine.
- Bencze, László Csaba,Filip, Alina,Bánóczi, Gergely,To?a, Monica Ioana,Irimie, Florin Dan,Gellért, ákos,Poppe, László,Paizs, Csaba
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supporting information
p. 3717 - 3727
(2017/07/07)
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- Magnetic nanoparticle-supported tetrazole-functionalized palladium catalyst: synthesis, DFT study and application for Sonogashira and Heck cross-coupling reactions
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Abstract: A novel magnetic catalyst-immobilized nano-palladium was efficiently prepared via a (2?+?3) cycloaddition pathway and characterized with different analyses, including FT-IR, FE-SEM, EDS, XRD, TEM and VSM methods. Also, topological and NBO analysis of a simple model of the catalyst with the M06/6-311?g(d,p)-LANL2DZ model chemistry have been introduced. In addition, the catalytic pursuit of this novel magnetic nanocatalyst was successfully evaluated in Sonogashira and Heck cross-coupling reactions. Furthermore, the catalyst could be easily separated by a conventional method using a permanent magnet and reused repeatedly in the model reaction without noteworthy loss of its catalytic activity.
- Elhampour, Ali,Nemati, Firouzeh,Nahzomi, Hossein Taherpour,Mohagheghi, Vahid
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p. 6737 - 6761
(2017/10/06)
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- Ligand-accelerated non-directed C-H functionalization of arenes
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The directed activation of carbon-hydrogen bonds (C-H) is important in the development of synthetically useful reactions, owing to the proximity-induced reactivity and selectivity that is enabled by coordinating functional groups. Palladium-catalysed non-directed C-H activation could potentially enable further useful reactions, because it can reach more distant sites and be applied to substrates that do not contain appropriate directing groups; however, its development has faced substantial challenges associated with the lack of sufficiently active palladium catalysts. Currently used palladium catalysts are reactive only with electron-rich arenes, unless an excess of arene is used, which limits synthetic applications. Here we report a 2-pyridone ligand that binds to palladium and accelerates non-directed C-H functionalization with arene as the limiting reagent. This protocol is compatible with a broad range of aromatic substrates and we demonstrate direct functionalization of advanced synthetic intermediates, drug molecules and natural products that cannot be used in excessive quantities. We also developed C-H olefination and carboxylation protocols, demonstrating the applicability of our methodology to other transformations. The site selectivity in these transformations is governed by a combination of steric and electronic effects, with the pyridone ligand enhancing the influence of sterics on the selectivity, thus providing complementary selectivity to directed C-H functionalization.
- Wang, Peng,Verma, Pritha,Xia, Guoqin,Shi, Jun,Qiao, Jennifer X.,Tao, Shiwei,Cheng, Peter T. W.,Poss, Michael A.,Farmer, Marcus E.,Yeung, Kap-Sun,Yu, Jin-Quan
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p. 489 - 493
(2017/11/28)
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- Gold-Catalyzed [2,3]-Sigmatropic Rearrangement: Reaction of Aryl Allyl Alcohols with Diazo Compounds
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A gold-catalyzed [2,3]-sigmatropic rearrangement reaction has been developed. The intermolecular rearrangement occurs between in situ generated donor-acceptor gold-carbenes and cinnamyl alcohols via tandem oxonium ylide formation. The desired rearranged product has been accomplished selectively over more conventional O-H insertion, cyclopropanation, cycloaddition, and C-H functionalization products under mild, open-air conditions. The scope of the work has been illustrated by synthesizing a new class of substrates that can be used for constructing complex molecular targets.
- Rao, Santhosh,Prabhu, Kandikere Ramaiah
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supporting information
p. 846 - 849
(2017/02/26)
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- Stereodivergent allylic substitutions with aryl acetic acid esters by synergistic iridium and lewis base catalysis
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The preparation of all possible stereoisomers of a given chiral molecule bearing multiple stereocenters by a simple and unified method is a significant challenge in asymmetric catalysis. We report stereodivergent allylic substitutions with aryl acetic acid esters catalyzed synergistically by a metallacyclic iridium complex and benzotetramisole. Through permutations of the enantiomers of the two chiral catalysts, all four stereoisomers of the products bearing two adjacent stereocenters are accessible with high diastereoselectivity and enantioselectivity. The resulting chiral activated ester products can be converted readily to enantioenriched amides, unactivated esters, and carboxylic acids in a onepot manner.
- Jiang, Xingyu,Beiger, Jason J.,Hartwig, John F.
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supporting information
p. 87 - 90
(2017/05/16)
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- Synthesis and evaluation of thiochroman-4-one derivatives as potential leishmanicidal agents
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The S-containing heterocyclic compounds benzothiopyrans or thiochromones stand out as having promising biological activities due to their structural relationship with chromones (benzopyrans), which are widely known as privileged scaffolds in medicinal chemistry. In this work, we report the synthesis of 35 thiochromone derivatives and the in vitro antileishmanial and cytotoxic activities. Compounds were tested against intracellular amastigotes of Leishmania panamensis and cytotoxic activity against human monocytes (U-937 ATCC CRL-1593.2). Compounds bearing a vinyl sulfone moiety, 4h, 4i, 4j, 4k, 4l and 4m, displayed the highest antileishmanial activity, with EC50 values lower than 10 μM and an index of selectivity over 100 for compounds 4j and 4l. When the double bond or the sulfone moiety was removed, the activity decreased. Our results show that thiochromones bearing a vinyl sulfone moiety are endowed with high antileishmanial activity and low cytotoxicity.
- Vargas, Esteban,Echeverri, Fernando,Vélez, Iván D.,Robledo, Sara M.,Qui?ones, Wiston
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- Investigation of two- and three-bond carbon–hydrogen coupling constants in cinnamic acid based compounds
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Two- and three-bond coupling constants (2JHC and 3JHC) were determined for a series of 12 substituted cinnamic acids using a selective 2D inphase/antiphase (IPAP)-single quantum multiple bond correlation (HSQMBC) and 1D proton coupled 13C NMR experiments. The coupling constants from two methods were compared and found to give very similar values. The results showed coupling constant values ranging from 1.7 to 9.7 Hz and 1.0 to 9.6 Hz for the IPAP-HSQMBC and the direct 13C NMR experiments, respectively. The experimental values of the coupling constants were compared with discrete density functional theory (DFT) calculated values and were found to be in good agreement for the 3JHC. However, the DFT method under estimated the 2JHC coupling constants. Knowing the limitations of the measurement and calculation of these multibond coupling constants will add confidence to the assignment of conformation or stereochemical aspects of complex molecules like natural products. Copyright
- Pierens, Gregory K.,Venkatachalam, Taracad K.,Reutens, David C.
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p. 941 - 946
(2016/11/16)
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- Improved synthesis method of palladium complex
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The invention discloses an improved synthesis method of a palladium complex (X in a general formula is equal to Br or I) and belongs to the field of organic chemistry. The improved synthesis method is characterized by including: using PdCl2(PPh3)2 and sodium iodide or sodium bromide as raw materials, wherein a feeding molar ratio is 1:10; using dichloromethane and water as solvents according to a volume ratio of 1:1, reacting to obtain a product, and subjecting the product to extracting, washing and filtering to obtain high-quality PdX2(PPh3) palladium complex. The palladium complex is high in yield, the method is simpler, the raw materials are cheaper, and the method has good industrial application prospect.
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Paragraph 0006
(2017/06/02)
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- Flexible, dicationic imidazolium salts for in situ application in palladium-catalysed Mizoroki–Heck coupling of acrylates under aerobic conditions
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The synthesis, characterization and in situ catalytic performance of new unsymmetric N,N′-disubstituted imidazolium-based dicationic salts in Mizoroki–Heck coupling of acrylates with aryl bromides under aerobic conditions are described. A series of flexible dicationic salts with varying steric and electronic properties were synthesized in good to excellent yields. All the salts were well characterized using spectroscopic techniques. X-ray diffraction analysis of two salts with the same dicationic backbone and different counter anions shows that the ligand adopts two different conformations which are influenced by the nature of the anion. Thus, the ligand is capable of changing its conformation according to the change in environment due to its flexible nature. All the synthesized imidazolium salts were found to be active in in situ palladium-catalysed Mizoroki–Heck coupling under aerobic conditions. Amongst the salts, the hydroxyl-functionalized imidazolium salt, incorporating the features of both bidentate chelating O,O ligand and carbene, shows the maximum catalytic activity. A variety of aryl and heteroaryl methyl and ethyl cinnamates were synthesized using these imidazolium salts as preligands. In addition, NMR studies confirm in situ generation of normal N-heterocyclic carbenes from the C-2 position of imidazol-2-ylidene ring. The mercury poisoning test was also performed to ascertain the nature of catalytically active palladium species. Aerobic conditions, low catalytic loading (0.5?mol%), shorter reaction times, broad functional group tolerance and good to excellent isolated yields are some of the significant features of the novel catalytic systems described here. Copyright
- Milton, Marilyn Daisy,Garg, Parul
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p. 759 - 766
(2016/09/04)
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- Green synthesis of palladium nanoparticles via branched polymers: A bio-based nanocomposite for C-C coupling reactions
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Catalytic process is the key process for many chemical industries. In this study, a novel heterogeneous Pd (CMH-Pd(0)) has been prepared by the deposition of palladium nanoparticles (Pd NPs) onto the surface of carboxymethyl functionalized hemicelluloses using ethanol as solvent and in situ reducing agent. The as prepared catalyst was characterized by TEM, HR-TEM, XRD, FT-IR, TGA and XPS. The loading level of Pd in the CMH-Pd(0) catalyst was 0.38 mmol g-1. The catalyst showed high catalytic activity and versatility towards Heck coupling reactions under aerobic conditions and could be readily recovered and reused in at least five successive cycles without obvious loss in activity. The catalyst is promising for its renewability, environmental benefits, efficient catalytic activity, mild reaction conditions, simple product work-up and easy catalyst recovery.
- Wu, Changyan,Peng, Xinwen,Zhong, Linxin,Li, Xuehui,Sun, Runcang
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p. 32202 - 32211
(2016/04/26)
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- New Pd(II) complexes of sulfur ylides; Synthesis, X-ray characterization, a theoretical study and catalytic activity toward the Mizoroki-Heck reaction
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The reaction of sulfur ylides (L) SMe2C(H)C(O)R (R = 4-nitrophenyl, phenyl, and 3-nitrophenyl) with the dichloro(1,5-cyclooctadiene)palladium(II) complex, [PdCl2(cod)], in a 2:1 ratio gives the new Pd(II) complexes of type cis- and trans-[PdCl2(SMe2C(H)C(O)R)2] (R = phenyl (1), 3-nitrophenyl (2), and 4-nitrophenyl (3)). Characterization of the obtained complexes was performed by elemental analysis, IR, 1H, 13C NMR and mass spectroscopies. Also, the structure of complex trans-[PdCl2(SMe2C(H)C(O)C6H4-p-NO2)2] (3) was characterized by single crystal X-ray analysis. The X-ray crystallography results reveal that the structure of complex 3 contains two Cα-coordinated sulfur ylide ligands in trans geometry. These air/moisture stable complexes were also employed as efficient catalysts for the Mizoroki-Heck cross-coupling reaction of several aryl halides with olefins. The coupled products of these reactions were obtained in good to excellent yields and purity, short reaction times and low catalyst loading. Also a theoretical study on the structure of the complexes 1-3 have been investigated at the BP86/def2-SVP level of theory. The bonding situation between the [PdCl2] and L2 fragments [(Ylide)2] in the [L2PdCL2] complexes, were carried out by NBO and energy-decomposition analysis (EDA), as well as their natural orbitals for chemical valence variation (EDA-NOCV). The results confirmed that the contribution of the electrostatic interactions in the Pd-C bond in the complexes is about 50%.
- Sabounchei,Ahmadianpoor,Yousefi,Hashemi,Bayat,Sedghi,Akhlaghi Bagherjeri,Gable
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p. 28308 - 28315
(2016/04/09)
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- Multi walled carbon nanotubes supported N-heterocyclic carbene-cobalt (II) as a novel, efficient and inexpensive catalyst for the Mizoroki-Heck reaction
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In this paper, an N-heterocyclic carbene-cobalt complex (NHC-Co2+) was immobilized onto the surface of multi-walled carbon nanotubes (MWCNTs) via direct grafting amination approach for the first time. The resultant composite (Co - NHC@MWCNTs) was characterized by FT-IR, TGA, XRD, ICP-OES, FE-SEM, TEM and CHN analyses. It was demonstrated that Co-NHC@MWCNTs can act as an efficient and inexpensive catalyst for Heck reactions in normal conditions which provided the corresponding products in moderate to good yields. More importantly, this phosphine and palladium-free catalyst can be reused for at least six successive runs without any discernible decrease in its catalytic activity and no remarkable changes were observed in catalyst structure.
- Hajipour, Abdol R.,Khorsandi, Zahra
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- Imidazolyl-Functionalized Ordered Mesoporous Polymer from Nanocasting as an Effective Support for Highly Dispersed Palladium Nanoparticles in the Heck Reaction
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New imidazolyl-functionalized ordered mesoporous cross-linked polymers were prepared by the copolymerization of the ionic liquid 3-benzyl-1-vinyl-1H-imidazolium bromide with divinylbenzene as the cross-linker and azobisisobutyronitrile as the radical initiator in the presence of O-silylated SBA-15 as the hard template. The materials were characterized by N2 adsorption–desorption analysis, TEM, thermogravimetric analysis, elemental analysis, and FTIR spectroscopy. The material, which benefits from the use of entrapped ionic liquid in the prepared polymer matrix in combination with its ordered mesoporous structure, is an excellent environment for the stabilization of highly dispersed Pd nanoparticles to result in a recyclable catalyst system with a significant activity in the Heck coupling reaction of aryl halides. The presence of well-distributed imidazolium functionalities in the polymeric framework might be responsible for the relatively uniform and nearly atomic scale distribution of Pd nanoparticles throughout the mesoporous structure and the prevention of Pd agglomeration during the reaction, which results in high durability, high stability, and good recycling characteristics of the catalyst. Although our catalyst system operates in a homogeneous pathway, it is also very stable and recyclable.
- Karimi, Babak,Marefat, Mohammad Reza,Hasannia, Maliheh,Akhavan, Pari Fadavi,Mansouri, Fariborz,Artelli, Zahra,Mohammadi, Fariba,Vali, Hojatollah
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p. 2508 - 2515
(2016/08/25)
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- Synthesis of polystyrene-supported Pd(II)-NHC complex derived from theophylline as an efficient and reusable heterogeneous catalyst for the Heck-Matsuda cross-coupling reaction
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The polystyrene-supported palladium(II)-N-heterocyclic carbene complex PS-NHC-Pd(II) was successfully synthesized from theophylline as an environmentally benign NHC precursor, using chloromethylated polystyrene resin. The PS-NHC-Pd(II) complex was characterized by various techniques including Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), thermal analysis (TGA-DTG), inductively coupled plasma (ICP), and CHN elemental analysis. The morphology of the polymer beads was also studied using scanning electron microscope. The polymer supported Pd(II)-NHC complex exhibits excellent catalytic activity and stability for the Heck-Matsuda cross-coupling reaction under mild conditions. A variety of arenediazonium tetrafluoroborate salts was coupled with the olefinic substrates in ethanol, in the presence of the 0.9 mol% of the catalyst to afford the corresponding cross-coupling adducts in high yields under aerial conditions. Moreover, the heterogeneous catalyst can be easily recovered by simple filtration and reused for seven cycles without significant loss in its activity.
- Mohammadi, Elmira,Movassagh, Barahman
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p. 158 - 167
(2016/04/20)
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- Ligand-free C-C and C-N cross-couplings with Pd/Nf-G nanocomposite
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Abstract The catalytic activity of electrochemical deposited Pd nanoparticles on nafion-graphene support was examined for Buchwald-Hartwig amination reaction and Heck coupling reaction. The developed protocol is very efficient and ecofriendly, providing excellent product yield. The Pd/Nf-G catalyst can be used up to four cycles with slight decrease in catalytic activity.
- Shelkar, Radheshyam S.,Shendage, Suresh S.,Nagarkar, Jayashree M.
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supporting information
p. 4463 - 4467
(2015/06/30)
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- Pd nanoparticles immobilized on Fe3O4 @ poly(ethylene glycol) bridged amine functionalized imidazolium ionic liquid: A magnetically separable catalyst for heck in water
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A palladium-based catalyst supported on novel Fe3O4 @ Poly(ethylene glycol) bridged amine functionalized imidazolium ionic liquid (Fe3O4@PEG-AIm-NH2- IL) was successfully prepared by a facile method. The catalyst was characterized by FT-IR, TEM, VSM, XRD, XPS and TGA-DSC, which showed high activity and stability for the Heck reaction in pure water. Furthermore, the catalyst could be recovered in a facile manner from the reaction mixture and recycled five times without any loss in activity.
- Liu, Xiang,Zhao, Xiaohua,Lu, Ming
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p. 1549 - 1556
(2019/11/28)
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- β-cyclodextrin-capped palladium nanoparticle-catalyzed ligand-free Suzuki and Heck couplings in low-melting β-cyclodextrin/NMU mixtures
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Low-melting β-cyclodextrin/N-methylurea (NMU) mixture, an efficient catalytic system for ligand-free Suzuki and Heck couplings in the presence of fresh native β-CD-capped Pd0 nanoparticles, has been successfully reported. This natural and convenient system can be performed in air and could afford the corresponding cross-coupled products in good to excellent isolated yields after a simple workup under every low Pd loading (0.05 mol%). Remarkably, the catalytic system can be recycled and reused without loss of catalytic activity. Copyright
- Zhao, Xiaohua,Liu, Xiang,Lu, Ming
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p. 635 - 640
(2014/08/05)
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- Silica-supported terpyridine palladium(II) complex as an efficient and reusable catalyst for Heck and Suzuki cross-coupling reactions
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Silica-supported terpyridine palladium(II) was prepared and used as an effective and recyclable catalyst in Mizoroki-Heck and Suzuki-Miyaura coupling reactions. The catalyst was very effective for the Mizoroki-Heck reaction of aryl halides with olefins and conversion was in most cases excellent. The catalyst showed good thermal stability (up to 230 °C) and could be recovered and reused for four reaction cycles. The Suzuki coupling of aryl iodides with aryl boronic acids in the presence of the catalyst was also investigated and the reaction proceeded with a short reaction time and excellent conversion.
- Amini, Mostafa M.,Feiz, Afsaneh,Dabiri, Minoo,Bazgir, Ayoob
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- Nano Pd-Fe3O4@Alg beads: As an efficient and magnetically separable catalyst for Suzuki, Heck and Buchwald-Hartwig coupling reactions
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Catalytic processes are the backbone of many chemical industries. In a comparative study of various heterogeneous catalytic systems, we report efficient and magnetically separable nano Pd-Fe3O4@Alg beads as catalysts for Suzuki, Heck and Buchwald-Hartwig coupling reactions. This catalyst was characterized by SEM, TEM, HRTEM, XRD, EDAX, FT-IR, VSM, DSC-TGA, BET, and UV-Visible spectroscopy. This heterogeneous catalyst showed high catalytic activity and stability for C-C and C-N bond forming coupling reactions with excellent product yield under ligand free conditions. The beads of nano Pd-Fe3O4@Alg can be separated from the reaction mixture by an external magnet and reused for several successive cycles with no appreciable loss in the catalytic activity. The Suzuki and Heck coupling reactions in aqueous medium are greener routes, which is an added advantage of this protocol. This journal is
- Shelkar, Radheshyam S.,Gund, Sitaram H.,Nagarkar, Jayashree M.
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p. 53387 - 53396
(2015/02/05)
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- Palladium supported on zinc oxide nanoparticles: Synthesis, characterization, and application as heterogeneous catalyst for Mizoroki-Heck and Sonogashira reactions under ligand-free and air atmosphere conditions
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In this paper, a novel Palladium (Pd) supported on ZnO nanoparticles was readily synthesized and characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and BET specific surface area measurement. The total amount of palladium particles on ZnO was determined by induced coupled plasma (ICP) analysis and atomic absorption spectroscopy (AAS) which is 9.8 wt%. Percentage of accessible Pd as active catalyst is also estimated to 2.72% based on the thermogravimetric (TG) analysis. Nano Pd/ZnO was found as a new, novel, and excellent heterogeneous catalyst for ligand-free C-C bond formation through the Mizoroki-Heck and Sonogashira reactions under air atmosphere without the use of any Ar or N2 flow. The catalyst can be recovered and recycled several times without marked loss of activity.
- Hosseini-Sarvari, Mona,Razmi, Zahra,Doroodmand, Mohammad Mehdi
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p. 477 - 486
(2014/03/21)
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- Phosphine mono- and bis-ylide palladacycles as homogeneous molecular precatalysts: Simple and efficient protocol greatly facilitate Suzuki and Heck coupling reactions
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Moisture/air-stable and robust phosphine mono- and bis-ylide palladacycles as catalyst precursors were used in Suzuki and Heck cross-coupling reactions with different aryl halides including electron-rich and electron-deficient substituents. These coupling
- Sabounchei, Seyyed Javad,Ahmadi, Mohsen,Panahimehr, Mohammad,Bagherjeri, Fateme Akhlaghi,Nasri, Zahra
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p. 249 - 259
(2014/02/14)
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- Investigation on the coordination mode of IL-supported diols used as phosphine-free ligands for palladium catalyzed heck reaction
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The coordination mode of IL-supported diols used as phosphine-free ligands for palladium catalyzed Heck reaction has been investigated by tuning their compositions. The difference in coordination of these IL-supported diols with metal Pd in Heck reaction was related to the changes of the cation rings, leading to the different activities of Pd catalyst in the reaction. The experimental results indicated that the activities of Pd catalyst were affected mainly by π-electron density of the cation rings. Compared to pyridinium and piperidinium cations, imidazolium cations showed the best coordination to metal Pd. In the meantime, C-2 hydrogen and the length of alkyl side chains had impacts on the coordination as well. Copyright
- Cai, Yueqin,Song, Gonghua,Chen, Xiao
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p. 1250 - 1256
(2013/11/06)
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- A metallosalen-based microporous organic polymer as a heterogeneous carbon-carbon coupling catalyst
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A novel microporous organic polymer framework with built-in metal sites in the skeleton has been synthesized by the Sonogashira-Hagihara reaction using salen-palladium as building units. The new microporous organic polymer possesses a high BET surface area, large pore volume, good stability and acts as a highly efficient robust recyclable heterogeneous catalyst towards carbon-carbon coupling reactions with low catalyst loading.
- Li, He,Xu, Bo,Liu, Xiaoming,Sigen,He, Chuanyi,Xia, Hong,Mu, Ying
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p. 14108 - 14114
(2013/11/19)
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- Palladium nanoparticles stabilized by metal-carbon covalent bond: An efficient and reusable nanocatalyst in cross-coupling reactions
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Palladium nanoparticles stabilized by PdC(binaphthyl) covalent bonds have been designed and synthesized. This new class of Pd nanoparticles was efficiently used as reusable catalysts for CC bond forming Heck, Suzuki-Miyaura and Sonogashira cross coupling reactions with high turnover. Even after the several catalytic cycles the Pd NPs had the same reactivity and particle size without any apparent agglomerization.
- Ganapathy, Dhandapani,Sekar, Govindasamy
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- Palladium supported on zinc ferrite: An efficient catalyst for ligand free C-C and C-O cross coupling reactions
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An efficient superparamagnetic Pd-ZnFe2O4 solid catalyst has been synthesized by loading Pd(0) species on zinc ferrite nanoparticles. Sonogashira cross couplings between terminal alkynes and aryl halides were achieved in the absence of any Cu co-catalyst. A Heck-Matsuda coupling reaction of structurally different aryldiazonium tetrafluoroborate substrates was preceded at 40 C in water. Cyanation of aryl halides was successfully done using K4[Fe(CN)6] as the cyanide source over Pd-ZnFe2O4. The catalyst was also employed for Ullmann type cross coupling reactions. Excellent yield of the products, reusability, and uncomplicated work-up make this catalyst efficient for C-C and C-O coupling reactions. Good yield of products, easy separation, and negligible leaching of Pd from the catalyst surface confirm the true heterogeneity in these catalytic reactions.
- Singh, Abhilash S.,Shendage, Suresh S.,Nagarkar, Jayashree M.
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p. 6319 - 6323
(2013/11/06)
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- Influence of electronically and sterically tunable cinnamate ligands on the spectroscopic, kinetic, and thermodynamic properties of bis(triphenylphosphine) palladium(0) olefin complexes
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A detailed study of the influence of electronic and steric characteristics of cinnamic acid esters on the spectroscopic, kinetic, and thermodynamic properties of bis(triphenylphosphine)palladium(0) cinnamic acid ester complexes is presented (51 different new complexes included). These complexes show a dynamic behavior on the NMR spectroscopic time scale. Therefore, the rotational barriers of the olefin about the metalolefin bond as well as the dissociation entropy and enthalpy of the olefin and the dissociation mechanism could be determined. These findings are interpreted together with the NMR spectroscopic, IR spectroscopic, and X-ray structural data (7 new structures included) concerning the influence of the different olefin ligands on the complex properties by means of Hammett plots. DFT calculations were performed to support the mechanistic conclusions.
- Buchner, Magnus R.,Bechlars, Bettina,Wahl, Bernhard,Ruhland, Klaus
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body text
p. 588 - 601
(2012/03/22)
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