- Substituent Dependence Charge Transfer and Photochemical Properties of Donor-Acceptor Substituted Ethenyl Thiophenes
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Donor-acceptor conjugated molecules with efficient light induced properties represent interesting material for electronic device application. In this context, we have calculated excited state dipole moment of three ethenyl thiophenes (1–3) bearing varied
- Kumar, Naresh,Kumar, Jagdeep,Hota, Prasanta Kumar
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- Heterobimetallic Pd/Mn and Pd/Co complexes as efficient and stereoselective catalysts for sequential Cu-free Sonogashira coupling–alkyne semi-hydrogenation reactions
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A series of heterobimetallic PdII/MII complexes (MII = Mn, Co) were synthesised and tested as precatalysts for sequential Sonogashira coupling–alkyne semi-hydrogenation reactions to form Z-aryl alkenes. The carbometalated heterobimetallic PdII/CoII complex CoPdL3′ demonstrated an apparent cooperative effect compared to the corresponding monometallic counterparts. This compound was identified as a potent single-molecule catalyst for the one-pot Cu-free Sonogashira coupling of aryl bromides with terminal alkynes followed by chemo- and stereoselective semi-hydrogenation of the alkyne intermediate using NH3·BH3 as a hydrogen source. Furthermore, different aromatic substrates have been tested to show the generality of the reaction for the synthesis of Z-alkenes, including biologically active combretastatin A-4. In addition, the homogeneous nature of the catalytically active species was demonstrated.
- Baweja, Saral,Clauss, Reike,Gelman, Dmitri,Hey-Hawkins, Evamarie
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p. 1344 - 1356
(2022/02/03)
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- Palladium Loaded Dendronized Polymer as Efficient Polymeric Sustainable Catalyst for Heck Coupling Reaction
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The palladium incorporated amine-functionalized dendronized polymer was synthesized by the addition of palladium acetate to dendronized polymer in methanol at room temperature. Palladium species are immobilized onto the dendritic structure by their coordination with amino functional groups. The newly developed dendritic system showed high palladium content in the low generation level itself, which was found to be 4.19?mmol/g. This was fairly higher than, the other palladium-based catalysts. Energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, UV–Visible spectroscopy, and X-ray photoelectron spectroscopy were used to confirm the successful synthesis of the new catalyst. It was used as a homogeneous palladium catalyst for Heck coupling reaction between olefins and differently substituted aryl halides and the products were isolated in high yield. The products isolated were in trans configuration, which indicated the selectivity of the newly developed catalytic system. Also, this catalyst system was reused up to nine times without a significant decrease in its catalytic activity. The easy accessibility of catalytic sites, stability, resistance to metal leaching, high catalytic activity and remarkable stereoselectivity with a low amount of catalyst are all due to the dendritic support. The docking study was carried out for all the stilbene derivatives obtained by the Heck coupling reaction against DprE1 protein to study its potential antitubercular activity. All the compounds displayed superior docking score values over the range ??6.5 to ??8.2?kcal/mol, compared to the standard drug isoniazid with docking score of ??6.1?kcal/mol against DprE1. Graphic Abstract: [Figure not available: see fulltext.]
- Hiba, K.,Krishna, G. Anjali,Prathapan, S.,Sreekumar, K.
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- N-Heterocyclic carbene palladium (II)-pyridine (NHC-Pd (II)-Py) complex catalyzed heck reactions
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A mild, efficient, and practical catalytic system for the synthesis of highly privileged stilbene pharmacophores is reported. This system uses N-heterocyclic carbene palladium (II) Pyridine (NHC-Pd (II)-Py) complex to catalyze the formation of carbon-carbon bonds between olefin derivatives and various bromide. This simple, gentle and user-friendly method can offer a variety of stilbene products in excellent yields under solvent-free condition. And its scale-up reaction has excellent yield and this system can be applied to industrial fields. The utility of this method is highlighted by its universality and modular synthesis of a series of bioactive molecules or important medical intermediates.
- Li, Dan,Tian, Qingqiang,Wang, Xuetong,Wang, Qiang,Wang, Yin,Liao, Siwei,Xu, Ping,Huang, Xin,Yuan, Jianyong
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supporting information
p. 2041 - 2052
(2021/05/25)
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- Biogenic synthesis of Pd-nanoparticles using Areca Nut Husk Extract: a greener approach to access α-keto imides and stilbenes
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An eco-friendly green method for a one-step synthesis of palladium nanoparticles and their synthetic utility are reported. Phytochemicals like amines, alcohols, and phenols present in the Areca Nut Husk extract facilitate the reduction of Pd(ii) to Pd(0). The phytochemicals serve as stabilising agents and ligands for palladium reduction and the need for an external ligand is avoided. The Field Emission Scanning Electron Microscopy and Transmission Electron Microscopy of newly synthesized palladium nanoparticles revealed a spherical morphology. The catalytic activity of the nanoparticles was tested for 1,2-difunctionalization of ynamides, Heck coupling, denitrogenative coupling of phenylhydrazine and C-H arylation of indole. Moreover, catalyst recyclability, control experiments, mechanistic elucidation, and gram-scale synthesis are elaborated.
- Dateer, Ramesh B.,Ghosh, Arnab,Hegde, Rajeev V.,Jadhav, Arvind H.,Nizam, Aatika,Patil, Siddappa A.,Peter, Febina
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supporting information
p. 16213 - 16222
(2021/09/22)
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- Antiradical Properties of trans-2-(4-substituted-styryl)-thiophene
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2-substituted thiophene compounds with electron donating and electron withdrawing p-phenyl substitution were synthesized and studied their radical scavenging properties using DPPH assay and DFT method. It is shown that p-hydroxy and p-amino phenyl substit
- Gusain, Anamika,Kumar, Naresh,Kumar, Jagdeep,Pandey, Gunjan,Hota, Prasanta Kumar
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- Ruthenium-Catalyzed E-Selective Partial Hydrogenation of Alkynes under Transfer-Hydrogenation Conditions using Paraformaldehyde as Hydrogen Source
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E-alkenes were synthesized with up to 100 % E/Z selectivity via ruthenium-catalyzed partial hydrogenation of different aliphatic and aromatic alkynes under transfer-hydrogenation conditions. Paraformaldehyde as a safe, cheap and easily available solid hydrogen carrier was used for the first time as hydrogen source in the presence of water for transfer-hydrogenation of alkynes. Optimization reactions showed the best results for the commercially available binuclear [Ru(p-cymene)Cl2]2 complex as pre-catalyst in combination with 2,2-bis(diphenylphosphino)-1,1-binaphthyl (BINAP) as ligand (1 : 1 ratio per Ru monomer to ligand). Mechanistic investigations showed that the origin of E-selectivity in this reaction is the fast Z to E isomerization of the formed alkenes. Mild reaction conditions plus the use of cheap, easily available and safe materials as well as simple setup and inexpensive catalyst turn this protocol into a feasible and promising stereo complementary procedure to the well-known Z-selective Lindlar reduction in late-stage syntheses. This procedure can also be used for the production of deuterated alkenes simply using d2-paraformaldehyde and D2O mixtures.
- Fetzer, Marcus N. A.,Tavakoli, Ghazal,Klein, Axel,Prechtl, Martin H. G.
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p. 1317 - 1325
(2021/02/11)
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- Electrochemical Aziridination of Internal Alkenes with Primary Amines
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An electrochemical approach to prepare aziridines via an oxidative coupling between alkenes and primary alkyl amines was realized. The reaction is carried out in an electrochemical flow reactor, leading to short reaction/residence times (5 min), high yields, and broad scope. At the cathode, hydrogen is generated, which can be used in a second reactor to reduce the aziridine yielding the corresponding hydroaminated product.Aziridines are useful synthetic building blocks, widely employed for the preparation of various nitrogen-containing derivatives. As the current methods require the use of prefunctionalized amines, the development of a synthetic strategy toward aziridines that can establish the union of alkenes and amines would be of great synthetic value. Herein, we report an electrochemical approach, which realizes this concept via an oxidative coupling between alkenes and primary alkylamines. The reaction is carried out in an electrochemical flow reactor leading to short reaction/residence times (5 min), high yields, and broad scope. At the cathode, hydrogen is generated, which can be used in a second reactor to reduce the aziridine, yielding the corresponding hydroaminated product. Mechanistic investigations and DFT calculations revealed that the alkene is first anodically oxidized and subsequently reacted with the amine coupling partner.The central tenet in modern synthetic methodology is to develop new methods only using widely available organic building blocks. As a direct consequence, new activation strategies are required to cajole the coupling partners to react and, subsequently, forge new and useful chemical bonds. Using electrochemical activation, our methodology enables for the first time the direct coupling between olefins and amines to yield aziridines. Aziridines display interesting pharmacological activity and serve as valuable synthetic intermediates to prepare diverse nitrogen-containing derivatives. Interestingly, the sole byproduct generated in this process is hydrogen, which can be subsequently used to reduce the aziridine into the corresponding hydroaminated product. Hence, this electrochemical methodology can be regarded as green and sustainable from the vantage point of upgrading simple and widely available commodity chemicals.
- Bartolomeu, Aloisio de A.,Dyga, Marco,Goo?en, Lukas J.,Laudadio, Gabriele,No?l, Timothy,O?eka, Maksim,de Bruin, Bas,de Oliveira, Kleber T.,van Leest, Nicolaas P.
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supporting information
p. 255 - 266
(2021/01/19)
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- A Solid-Phase Assisted Flow Approach to In Situ Wittig-Type Olefination Coupling
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Described herein is the development of a continuous flow, solid-phase triphenylphosphine (PS-PPh3) assisted protocol to facilitate the in situ coupling of reciprocal pairs of halogen and carbonyl functionalised molecular pairs by a Wittig olefination within 15 mins. The protocol entails injecting a single solution (1 : 1 CHCl3 : EtOH) containing the halogenated and carbonyl-based substrates into a continuously flowing stream of CHCl3 : EtOH (1 : 1), passed through a fixed bed of K2CO3 and PS-PPh3. With advancement to the previous PS-PPh3 coupling procedures, the method employs a traditional polystyrene-based immobilisation matrix, the substrate scope of the protocol extended to substituted ketones, secondary alkyl chlorides, and an unprotected maleimide scaffold.
- Aldrich-Wright, Janice R.,Dankers, Christian,Gordon, Christopher P.,Polyzos, Anastasios,Tadros, Joseph
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supporting information
p. 4184 - 4194
(2021/08/24)
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- A photocatalyst-free visible-light-mediated solvent-switchable route to stilbenes/vinyl sulfones from β-nitrostyrenes and arylazo sulfones
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Photocatalyst-free visible-light-mediated reactions, based on the presence of a visible-light-absorbing functional group in the starting material itself in order to exclude the often costly, hazardous, degradable and difficult to remove or recover photoredox catalysts, have been gaining momentum recently. We have employed this approach to develop a denitrative photocatalyst-free visible-light-mediated protocol for the arylation/sulfonylation of β-nitrostyrenes employing arylazo sulfones (bench-stable photolabile compounds) in a switchable solvent-controlled manner. Arylazo sulfones served as the aryl and sulfonyl radical precursors under blue LED irradiation for the synthesis oftrans-stilbenes and (E)-vinyl sulfones in CH3CN and dioxane/H2O 2?:?1, respectively. The absence of any metal, photocatalyst and additive; excellent selectivity (E-stereochemistry) and solvent-switchability; and the use of visible light and ambient temperature are the prime assets of the developed method. Moreover, we report the first photocatalyst-free visible light-driven route to synthesize stilbenes and vinyl sulfones from readily available β-nitrostyrenes.
- Chawla, Ruchi,Dutta, P. K.,Jaiswal, Shefali,Yadav, Lal Dhar S.
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supporting information
p. 6487 - 6492
(2021/08/03)
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- Tandem Acceptorless Dehydrogenative Coupling-Decyanation under Nickel Catalysis
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The development of new catalytic processes based on abundantly available starting materials by cheap metals is always a fascinating task and marks an important transition in the chemical industry. Herein, a nickel-catalyzed acceptorless dehydrogenative coupling of alcohols with nitriles followed by decyanation of nitriles to access diversely substituted olefins is reported. This unprecedented C=C bond-forming methodology takes place in a tandem manner with the formation of formamide as a sole byproduct. The significant advantages of this strategy are the low-cost nickel catalyst, good functional group compatibility (ether, thioether, halo, cyano, ester, amino, N/O/S heterocycles; 43 examples), synthetic convenience, and high reaction selectivity and efficiency.
- Babu, Reshma,Balaraman, Ekambaram,Midya, Siba P.,Subaramanian, Murugan,Yadav, Vinita
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p. 7552 - 7562
(2021/06/28)
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- New 1,2,3-triazole based bis- And trisphosphine ligands: Synthesis, transition metal chemistry and catalytic studies
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The syntheses and transition metal chemistry of triazole-based bis- and tris-phosphines, 5-(diphenylphosphanyl)-1-(2-(diphenylphosphanyl)phenyl)-4-phenyl-1H-1,2,3-triazole (2), 5-(diphenylphosphanyl)-4-(2-(diphenylphosphanyl)phenyl)-1-phenyl-1H-1,2,3-tria
- Balakrishna, Maravanji S.,Butcher, Ray J.,Kunchur, Harish S.,Namdeo, Pavan K.,Radhakrishna, Latchupatula
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p. 3434 - 3449
(2020/03/27)
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- Catalytic activity of Pd dithiolate complexes with large-bite-angle diphosphines in Heck coupling reactions
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Palladium(II) complexes of aryl dithiolates and wide-bite-angle diphosphines Xantphos and dppf have been developed as efficient catalysts in Suzuki and Suzuki carbonylation reactions. The catalytic activity of these highly stable, discrete and charged complexes was investigated in Heck coupling reactions of styrene and a variety of aryl bromides. Under optimized reaction conditions these palladium complexes showed excellent activity with high turnover number (6 × 106) and high turnover frequency (4 × 105 h?1). The effect of bite angle of diphosphines on the catalytic activity of the complexes [Pd2(P∩P)2(SC12H8S)]2(OTf)4 followed the trend P∩P = Xantphos > dppf > dppe as the order of their bite angles. The catalyst could be reused, and after three cycles the formation of significant amount of Pd nanoparticles was noticed, which were characterized using powder X-ray diffraction, energy-dispersive X-ray analysis and transmission electron microscopy. The high catalytic activity has been attributed to the Pd nanoparticles.
- Mane, Pravin A.,Neogy, Suman,Dey, Sandip
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- Stereo-controlledanti-hydromagnesiation of aryl alkynes by magnesium hydrides
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A concise protocol foranti-hydromagnesiation of aryl alkynes was established using 1?:?1 molar combination of sodium hydride (NaH) and magnesium iodide (MgI2) without the aid of any transition metal catalysts. The resulting alkenylmagnesium intermediates could be trapped with a series of electrophiles, thus providing facile accesses to stereochemically well-defined functionalized alkenes. Mechanistic studies by experimental and theoretical approaches imply that polar hydride addition from magnesium hydride (MgH2) is responsible for the process.
- Chiba, Shunsuke,Li, Yihang,Ong, Derek Yiren,Pang, Jia Hao,Takita, Ryo,Wang, Bin,Watanabe, Kohei
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p. 5267 - 5272
(2020/06/04)
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- A Bidentate Ru(II)-NC Complex as a Catalyst for Semihydrogenation of Alkynes to (E)-Alkenes with Ethanol
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Four Ru(II)-NC complexes were tested as catalysts for semihydrogenation of internal alkynes to (E)-alkenes with ethanol, and the complex {(C5H4N)(C6H4)}RuCl(CO)(PPh3)2 (1a) showed the highest activity. The reactions proceeded well with 1 mol % catalyst loading and 0.1 equiv of t-BuONa at 110 °C for 1 h, and 32 alkenes were synthesized with excellent E:Z selectivity. This is the first ruthenium-catalyzed semihydrogenation of internal alkynes to (E)-alkenes using ethanol as the hydrogen donor.
- Chen, Dafa,Gong, Dawei,Hu, Bowen,Kong, Degong,Xia, Haiping,Yang, Weiwei
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- A Simple Nickel Catalyst Enabling an E-Selective Alkyne Semihydrogenation
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Stereoselective alkyne semihydrogenations are attractive approaches to alkenes, which are key building blocks for synthesis. With regards to the most atom-economic reducing agent dihydrogen (H2), only few catalysts for the challenging E-selective alkyne semihydrogenation have been disclosed, each with a unique substrate scope profile. Here, we show that a commercially available nickel catalyst facilitates the E-selective alkyne semihydrogenation of a wide variety of substituted internal alkynes. This results in a simple and broadly applicable overall protocol to stereoselectively access E-alkenes employing H2, which could serve as a general method for synthesis.
- Thiel, Niklas O.,Kaewmee, Benyapa,Tran Ngoc, Trung,Teichert, Johannes F.
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supporting information
p. 1597 - 1603
(2020/02/05)
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- Chemoselective Hydrogenation of Alkynes to (Z) -Alkenes Using an Air-Stable Base Metal Catalyst
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A highly selective hydrogenation of alkynes using an air-stable and readily available manganese catalyst has been achieved. The reaction proceeds under mild reaction conditions and tolerates various functional groups, resulting in (Z)-alkenes and allylic alcohols in high yields. Mechanistic experiments suggest that the reaction proceeds via a bifunctional activation involving metal-ligand cooperativity.
- Zubar, Viktoriia,Sklyaruk, Jan,Brzozowska, Aleksandra,Rueping, Magnus
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supporting information
p. 5423 - 5428
(2020/07/24)
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- Methanol as the Hydrogen Source in the Selective Transfer Hydrogenation of Alkynes Enabled by a Manganese Pincer Complex
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The first base metal-catalyzed transfer hydrogenation of alkynes with methanol is described. An air and moisture stable manganese pincer complex catalyzes the reduction of a variety of different alkynes to the corresponding (Z)-olefins in high yields. The
- Sklyaruk, Jan,Zubar, Viktoriia,Borghs, Jannik C.,Rueping, Magnus
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supporting information
p. 6067 - 6071
(2020/08/28)
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- Aqueous phase semihydrogenation of alkynes over Ni-Fe bimetallic catalysts
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Bimetallic Ni-Fe catalysts (Ni/Fe, 1?:?1, 1?:?3, and 3?:?1) are synthesized and explored for their catalytic activity in semihydrogenation of internal alkynes using H2 gas in water-ethanol solution. Our findings revealed that over the Ni1Fe3 catalyst a high diastereoselectivity for Z-alkenes with a high conversion for a wide range of internal alkynes can be achieved at moderate reaction temperature (40 °C). Notably, the selectivity for the Z-alkenes is enhanced in the presence of n-butyl amine as an additive. Deuterium labeling experiments evidenced that H2 gas becomes dissociated homolytically over the catalyst surface to hydrogenate alkynes to alkenes. Synthesized catalysts were successfully characterized by HR-TEM, SEM, XPS, EDS, P-XRD and H2-TPD.
- Awasthi, Mahendra K.,Barman, Sudipta Roy,Behrens, Silke,Rai, Rohit K.,Singh, Sanjay K.,Singh, Vipin K.
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p. 4968 - 4980
(2020/08/19)
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- HIGHLY SELECTIVE ELECTROCHEMICAL HYDROGENATION OF ALKYNES
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Disclosed are electrochemical methods to prepare an alkane or an alkene, such as a cis- alkene, from an alkyne, or an alkane from an alkene. The method utilizes an electrochemical cell having a cathode and an anode and a reactor.
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Page/Page column 7; 12
(2020/10/20)
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- Functionalization of the Imidazole Backbone by Means of a Tailored and Optimized Oxidative Heck Cross-Coupling
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A general and selective Pd-catalyzed cross-coupling of aromatic boronic acids with vinyl-imidazoles is disclosed. Unlike most cross-coupling reactions, this method operates well in absence of bases avoiding the formation of by-products. The reactivity is highly enhanced by the presence of nitrogen-based ligands, in particular bathocuproine. The method involves MnO2 as oxidant for the oxidation Pd (0)→Pd (II), a much weaker oxidant than previously reported in the literature. This allows for the use of reactants that possess a multitude of functional groups. A scope and limitation study involving a series of 24 boronic acids, whereof 18 afforded TMs in yields in the range 41–95%. The disclosed method constitutes the first general method for the oxidative Heck cross-coupling on the imidazole scaffold, which moreover operates with a selection of other heterocycles. (Figure presented.).
- Cirillo, Davide,Angelucci, Francesco,Bj?rsvik, Hans-René
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p. 5079 - 5092
(2020/09/23)
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- Diboron-Assisted Copper-Catalyzed Z-Selective Semihydrogenation of Alkynes Using Ethanol as a Hydrogen Donor
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We herein describe a B2Pin2-assisted copper-catalyzed semihydrogenation of alkynes. A variety of alkenes were obtained in good to excellent yields with Z-selectivity under mild reaction conditions. Mechanistic studies indicated that a transfer hydrogenation process was involved and ethanol acted as both a solvent and a hydrogen donor in this reaction. The present protocol enabled convenient synthesis of deuterium-substituted Z-alkenes such as Z-Combretastain A4-d2 in a high deuteration ratio by using readily available ethanol-d1 as the deuterium source.
- Bao, Hanyang,Zhou, Bingwei,Jin, Hongwei,Liu, Yunkui
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p. 3579 - 3589
(2019/03/11)
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- Cobalt catalyzed stereodivergent semi-hydrogenation of alkynes using H2O as the hydrogen source
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Cobalt-catalyzed stereodivergent semi-hydrogenation of internal alkynes to alkenes is developed. The reaction proceeded through transfer hydrogenation under mild conditions using a base metal CoI2 as the catalyst, and H2O/MeOH as the hydrogen source with Zn as the reductant. The E/Z-selectivity of the product could be switched by changing the solvent and by inclusion/exclusion of a bidentate phosphine ligand (dppe). This method provides a simple and cost effective pathway for the synthesis of 1,2-dideuterioalkenes.
- Li, Kangkui,Khan, Ruhima,Zhang, Xuexin,Gao, Yang,Zhou, Yongyun,Tan, Heng,Chen, Jingchao,Fan, Baomin
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supporting information
p. 5663 - 5666
(2019/05/21)
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- Proton-Coupled Electron Transfer: Transition-Metal-Free Selective Reduction of Chalcones and Alkynes Using Xanthate/Formic Acid
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Highly chemoselective reduction of α,β-unsaturated ketones to saturated ketones and stereoselective reduction of alkynes to (E)-alkenes has been developed under a transition-metal-free condition using a xanthate/formic acid mixture through proton-coupled electron transfer (PCET). Mechanistic experiments and DFT calculations support the possibility of a concerted proton electron-transfer (CPET) pathway. This Birch-type reduction demonstrates that a small nucleophilic organic molecule can be used as a single electron-transfer (SET) reducing agent with a proper proton source.
- Prasanna, Ramanathan,Guha, Somraj,Sekar, Govindasamy
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supporting information
p. 2650 - 2653
(2019/04/17)
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- Synthesis of 1,3-disubstituted cyclohexenes from dienylethers: Via sequential hydrozirconation/deoxygenative cyclisation
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Access to 1,3-disubstituted cyclohexenes from zirconocenes containing a latent electrophilic allylic fragment is described. Requiring a specific conformation, 6-endo-trig cyclisation is based on the TMSOTf-mediated generation of a stabilized carbocation.
- Payet, Amandine,Blondeau, Benjamin,Behr, Jean-Bernard,Vasse, Jean-Luc
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p. 798 - 802
(2019/02/01)
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- A tailored polymeric cationic tag-anionic Pd(ii) complex as a catalyst for the low-leaching Heck-Mizoroki coupling in flow and in biomass-derived GVL
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The [PdCl4]2- palladium complex has been immobilized on a polystyrene-type resin loaded with pincer-type imidazolium ionic tag binding sites. The catalytic system (Pd(ii)-POLI-TAG) has proved to be highly active in the definition of an efficient protocol for the Heck-Mizoroki coupling reaction under batch and flow conditions. Importantly, it is shown to be highly robust in combination with a safe non-toxic reaction medium, i.e. biomass-derived GVL, since it could be reused for multiple runs without significantly losing its activity.
- Mahmoudi, Hamed,Valentini, Federica,Ferlin, Francesco,Bivona, Lucia Anna,Anastasiou, Ioannis,Fusaro, Luca,Aprile, Carmela,Marrocchi, Assunta,Vaccaro, Luigi
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supporting information
p. 355 - 360
(2019/01/28)
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- Templating effect of carbon nanoforms on highly cross-linked imidazolium network: Catalytic activity of the resulting hybrids with Pd nanoparticles
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Two different carbon nanoforms (CNFs), namely multi-walled carbon nanotubes (MWCNTs) and carbon nanohorns (CNHs), have been chosen as support for the direct polymerization of a bis-vinylimidazolium salt. Transmission electron microscopy analyses revealed a templating effect of the CNFs on the growth of the polymeric network, which perfectly covers their whole surfaces creating a cylindrical or spherical coating for MWCNTs and CNHs, respectively. Subsequently, the CNFs-polyimidazolium have been used as stabilizers for Pd nanoparticles (Pd NPs), and the obtained materials have been characterized by means of analytical and spectroscopic techniques and then employed as easily recoverable and recyclable catalysts for Suzuki and Heck reactions. Quantitative conversions have been obtained in almost all the explored reactions, even employing low loading of catalyst (down to 0.007 mol%). Suzuki reactions were carried out in pure water under aerobic conditions. Both materials showed excellent activity and recyclability for the investigated C-C coupling reactions, with the CNHs-based material resulting slightly more active than the MWCNTs-based one due to a higher superficial exposure of Pd NPs.
- Campisciano, Vincenzo,Calabrese, Carla,Liotta, Leonarda Francesca,La Parola, Valeria,Spinella, Alberto,Aprile, Carmela,Gruttadauria, Michelangelo,Giacalone, Francesco
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- SBA-15/POSS-Imidazolium Hybrid as Catalytic Nanoreactor: the role of the Support in the Stabilization of Palladium Species for C?C Cross Coupling Reactions.
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Supported imidazolium modified polyhedral oligomeric silsesquioxanes (POSS) on SBA-15 have been used as platform for Pd(II) species. The so-obtained material was firstly characterized by means of TGA, solid state NMR, TEM, XPS, SAXS, porosimetry and ICP-OES and it was successfully tested as pre-catalyst in C?C cross couplings, namely Suzuki-Miyaura and Heck reactions. In both cases, the solid proved to be highly efficient and easily recoverable from the reaction mixture. The recyclability was verified for up to seven cycles without showing any activity decrease. Interestingly, only Pd(II) was detected in the reused catalyst in the Heck reaction. Therefore, the versatility of the material was investigated by using various aryl halides. Our palladium nanocomposite was able to promote both Suzuki and Heck reactions down to 0.0007 mol% showing outstanding turnover frequency (TOF) values of 114,286 and 32,381 h?1, respectively. Comparison with the palladium catalyst on SiO2-POSS-imidazolium support showed interesting differences in terms of stabilization of Pd species and recyclability. The excellent outcome of the reactions could be ascribed to the textural properties of the SBA-15 support and the presence of the imidazolium-POSS nanocage within the pores of SBA-15, that worked as a sort of nanoreactor. (Figure presented.).
- Calabrese, Carla,Campisciano, Vincenzo,Siragusa, Fabiana,Liotta, Leonarda F.,Aprile, Carmela,Gruttadauria, Michelangelo,Giacalone, Francesco
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p. 3758 - 3767
(2019/05/15)
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- Water as a Hydrogenating Agent: Stereodivergent Pd-Catalyzed Semihydrogenation of Alkynes
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Palladium-catalyzed transfer semihydrogenation of alkynes using H2O as the hydrogen source and Mn as the reducing reagent is developed, affording cis- and trans-alkenes selectively under mild conditions. In addition, this method provides an efficient way to access various cis-1,2-dideuterioalkenes and trans-1,2-dideuterioalkenes by using D2O instead of H2O.
- Zhao, Chuan-Qi,Chen, Yue-Gang,Qiu, Hui,Wei, Lei,Fang, Ping,Mei, Tian-Sheng
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supporting information
p. 1412 - 1416
(2019/03/07)
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- Stereoselective Alkyne Hydrogenation by using a Simple Iron Catalyst
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The stereoselective hydrogenation of alkynes constitutes one of the key approaches for the construction of stereodefined alkenes. The majority of conventional methods utilize noble and toxic metal catalysts. This study concerns a simple catalyst comprised of the commercial chemicals iron(II) acetylacetonate and diisobutylaluminum hydride, which enables the Z-selective semihydrogenation of alkynes under near ambient conditions (1–3 bar H2, 30 °C, 5 mol % [Fe]). Neither an elaborate catalyst preparation nor addition of ligands is required. Mechanistic studies (kinetic poisoning, X-ray absorption spectroscopy, TEM) strongly indicate the operation of small iron clusters and particle catalysts.
- Gregori, Bernhard J.,Schwarzhuber, Felix,P?llath, Simon,Zweck, Josef,Fritsch, Lorena,Schoch, Roland,Bauer, Matthias,Jacobi von Wangelin, Axel
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p. 3864 - 3870
(2019/07/31)
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- Determining the excited-state substituent constants of furyl and thienyl groups
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Six series of styrene derivatives XCH═CHArY (total of 65) containing the styrene parent molecular skeleton were synthesized (here, Y is OMe, Me, H, F, Cl, CF3, CN, and NO2, and X is 2-furyl, 3-furyl, 2′-methyl-2-furyl, 2-thienyl, 3-thienyl, and 2′-methyl-2-theniyl). Their ultraviolet absorption spectra were measured in anhydrous ethanol, and their wavelength of absorption maximum λmax was recorded. For the wavenumber νmax (cm?1, νmax?=?1/λmax) of the obtained λmax, a quantitative correlation analysis was performed, and 6 excited-state substituent constants σexcc(p) of groups X were obtained by means of curve-fitting method. Taking the νmax values of total 90 compounds of styrene derivatives as a data set (including 25 compounds from reference and 65 compounds of this work), a quantitative correlation analysis was performed, and the reliability of the obtained σexcc(p) was verified. In addition, 12 samples of disubstituted Schiff bases (XCH═NArY) involving the above groups X were synthesized, and their νmax values were recorded. Using these 12 νmax together with the 14 νmax values of Schiff bases taken from reference (total of 26 compounds), it was further verified that the σexcc(p) values are reliable by means of quantitative correlation method.
- Qu, Junyan,Cao, Chao-Tun,Cao, Chenzhong
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supporting information
(2018/04/24)
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- Pd(OAc)2 immobilized on imine-functionalized microporous covalent triazine polymer as efficient heterogeneous catalyst for Mizoroki–Heck cross-coupling reaction
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A template consisting of Pd(OAc)2 immobilized on imine-functionalized microporous covalent triazine polymer network (Pd/TATAE) was synthesized and found to be an efficient and recyclable heterogeneous solid catalyst for Mizoroki–Heck C–C coupling of styrene with substituted aryl halides under mild reaction conditions and without addition of any ligand or additives. Furthermore, Pd/TATAE could be recycled for nine consecutive cycles with minor loss of catalytic activity. Finally, the Pd/TATAE catalyst showed good catalytic activity with excellent yield of 96?% and high turnover number of 3349.
- Sadhasivam, Velu,Mathappan, Mariyappan,Harikrishnan, Muniyasamy,Chithiraikumar, Chinnadurai,Murugesan, Sepperumal,Siva, Ayyanar
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p. 2853 - 2866
(2018/02/16)
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- Substituent Dependent Optical Properties of p-phenyl Substituted ethenyl-E-thiophenes
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Various electron donor and acceptor substituted (NO2, CN, Cl, H, OCH3, NH2) p-phenyl ethenyl-E- thiophenes (1–6) were synthesized and substituent dependent optical properties (dipole moment, transition dipole moment, oscillator strength, optical band gap, hyperpolarizability) were studied using Solvatochromism and Density functional theory. It is shown that thiophene acts as a weak electron donor in presence of an electron withdrawing p-phenyl substituent (NO2, CN, Cl), whereas thiophene acts as a weak electron acceptor in presence of an electron donating p-phenyl substituent (OCH3, NH2). In comparison to ethenyl thiophene 4, the HOMO-LUMO energy band gap is decreased upon increasing the electron donating or electron withdrawing capacity of p-phenyl substituent. From the excited state dipole moment calculation, it is shown that the excited state is highly dipolar for nitro and amino compounds 1 and 6, whereas compounds 2–5 show a non-polar excited state. As compared to the ethenyl thiophene 4, the first hyperpolarizability (β) increases upon substitution either with a strong electron withdrawing or strong electron donating p-phenyl substituent. A large β value is found for p-nitro phenyl ethenyl-E-thiophene and p-amino phenyl ethenyl-E- thiophene. Overall, these studies provide useful information in understanding the optical properties of phenyl and heterocyclic based ethenyl systems.
- Kumar, Naresh,Paramasivam, Mahalingavelar,Kumar, Jagdeep,Gusain, Anamika,Hota, Prasanta Kumar
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p. 1207 - 1216
(2018/09/10)
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- Synthesis of bench-stable solid triorganoindium reagents and reactivity in palladium-catalyzed cross-coupling reactions
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Bench-stable solid triorganoindium compounds have been prepared by coordination with 4-(dimethylamino)pyridine (DMAP). The solid R3In(DMAP) complexes are obtained from the corresponding solution of R3In in quantitative yield and can
- Gil-Negrete, José M.,Pérez Sestelo, José,Sarandeses, Luis A.
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supporting information
p. 1453 - 1456
(2018/02/19)
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- Transition-Metal-Free Highly Chemoselective and Stereoselective Reduction with Se/DMF/H2O System
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A novel metal-free reduction system, in which H2Se (or HSe-) produced in situ from Se/DMF/H2O acts as the active reducing species, has been developed. By using water as an inexpensive, safe, and environmentally friendly surrogate as the hydrogen donor, this new reduction system incorporating Se/DMF/H2O displayed high selectivity and good activity in the reduction of α,β-unsaturated ketones and alkynes. Therefore, this reduction system has great potential to be a general and practical reduction methodology in organic transformation.
- Li, Hong-Chen,An, Cui,Wu, Ge,Li, Guo-Xing,Huang, Xiao-Bo,Gao, Wen-Xia,Ding, Jin-Chang,Zhou, Yun-Bing,Liu, Miao-Chang,Wu, Hua-Yue
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supporting information
p. 5573 - 5577
(2018/09/12)
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- Preparation method of trans-stilbene compound
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The invention relates to a synthesis method of a trans-stilbene compound. In an atmosphere of nitrogen or inert gas and an organic solvent, diphenylacetylene serves as a reaction substrate, and the trans-stilbene compound is obtained through chemically se
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Paragraph 0193; 0194; 0195; 0196; 0197; 0198; 0199-0202
(2018/11/03)
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- COBALT COMPLEXES, PROCESS FOR PREPARATION AND USE THEREOF
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The present invention discloses a cobalt compound of formula (I), a process for the preparation and use thereof. The present invention further relates to a pharmaceutical composition and a method inhibition of Tau Aggregation in a subject in need thereof using compound of formula (I).
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Page/Page column 15; 16
(2019/01/06)
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- Carbonyl–Olefin Cross-Metathesis Through a Visible-Light-Induced 1,3-Diol Formation and Fragmentation Sequence
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A visible-light-mediated approach to carbonyl–olefin cross-metathesis is described. Photoinduced hole catalysis was used to promote the formation of 1,3-diols from aldehydes and styrenes, which were then readily fragmented under acidic conditions to form the cross-metathesis products. The use of 1,3-diols as intermediates, rather than the energetically more demanding oxetanes, provides a new, orthogonal mechanistic strategy for carbonyl–olefin cross-metathesis. Furthermore, this approach does not require any metals, ligands, or additives, and provides the products with high levels of E selectivity. A mechanistic rationale is provided and supported by both theoretical calculations and experiments. Additionally, a practical synthesis of a new acridinium-based photocatalyst, including full characterization, is presented.
- Pitzer, Lena,Sandfort, Frederik,Strieth-Kalthoff, Felix,Glorius, Frank
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p. 16219 - 16223
(2018/11/23)
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- One-Pot Intermolecular Reductive Cross-Coupling of Deactivated Aldehydes to Unsymmetrically 1,2-Disubstituted Alkenes
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The phospha-Peterson reaction between a lithiated secondary phosphane, MesP(Li)TMS, and an aldehyde affords Mes-phosphaalkenes which, upon methanol addition and P-oxidation, react with a second carbonyl compound site specifically to produce unsymmetric alkenes. The E/Z selectivity of the one-pot cross coupling is largely determined by the electronic nature of the aryl substituent of the first aldehyde, with electron-donating groups giving rise to increased amounts of Z-alkenes.
- Arkhypchuk, Anna I.,D'Imperio, Nicolas,Ott, Sascha
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supporting information
p. 5086 - 5089
(2018/09/13)
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- Semireduction of Alkynes Using Formic Acid with Reusable Pd-Catalysts
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The treatment of PdCl2 with K2CO3 and HCO2H in dioxane gives black precipitates, which are an effective catalyst for the semireduction of alkynes to alkenes using formic acid as a reductant. Even 0.05 mol % Pd promoted the reduction reaction of tolane in high yield with high selectivity.
- Iwasaki, Riku,Tanaka, Eikichi,Ichihashi, Toshinari,Idemoto, Yasushi,Endo, Kohei
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p. 13574 - 13579
(2018/11/02)
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- Phosphine-free cobalt pincer complex catalyzed: Z -selective semi-hydrogenation of unbiased alkynes
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Herein, we report a novel, molecularly defined NNN-type cobalt pincer complex catalyzed transfer semi-hydrogenation of unbiased alkynes to Z-selective alkenes. This unified process is highly stereo- and chemo-selective and exhibits a broad scope as well as wide functional group tolerance. Ammonia-borane (AB), a bench-stable substrate with high gravimetric hydrogen capacity, was used as a safe and practical transfer hydrogenating source.
- Landge, Vinod G.,Pitchaimani, Jayaraman,Midya, Siba P.,Subaramanian, Murugan,Madhu, Vedichi,Balaraman, Ekambaram
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p. 428 - 433
(2018/02/07)
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- Highly Chemo- and Stereoselective Transfer Semihydrogenation of Alkynes Catalyzed by a Stable, Well-Defined Manganese(II) Complex
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Herein we report unprecedented manganese-catalyzed semihydrogenation of internal alkynes to (Z)-alkenes using ammonia borane as a hydrogen donor. The reaction is catalyzed by a pincer complex of the earth-abundant manganese(II) salt in the absence of any
- Brzozowska, Aleksandra,Azofra, Luis Miguel,Zubar, Viktoriia,Atodiresei, Iuliana,Cavallo, Luigi,Rueping, Magnus,El-Sepelgy, Osama
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p. 4103 - 4109
(2018/05/22)
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- Decarboxylative Arylation of α,β-Unsaturated Carboxylic Acids Using Aryl Triazenes by Copper/Ionic Liquid Combination in PEG-400
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A practical method for the construction of stilbene derivatives has been developed via catalytic cross-coupling of cinnamic acids with aryl triazenes. The methodology offers high stereoselectivity and is endowed with broad substrate scope, high yield, and significant functional group tolerance.
- Kumar, Saurabh,Kumar Pandey, Anand,Singh, Rahul,Nand Singh, Krishna
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supporting information
p. 5942 - 5946
(2018/11/10)
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- Group 4 Metallocene Difluoride/Palladium Bimetallic Catalysts for the Reductive Cross-Coupling of Alkynes with Aryl Iodides and Bromides
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A novel protocol has been developed for the selective synthesis of (E)-alkenes via the reductive cross-coupling of alkynes and aryl halides using a bimetallic catalyst system composed of a group 4 metallocene difluoride (Cp2[M]F2; [M] = Hf or Zr; Cp = cyclopentadienide) and palladium dichloride. This reaction proceeds via a coupling between an aryl halide and an in situ generated alkenyl metallocene intermediate derived from the group 4 metallocene difluoride, a hydrosilane, and an alkyne. For a catalytic reductive coupling, the addition of sodium fluoride (NaF) to the reaction system is required. Moreover, in the presence of NaF, a ligand exchange was observed by NMR spectroscopy in hafnocene diiodide (Cp2HfI2) to afford hafnocene difluoride (Cp2HfF2).
- Takahashi, Keita,Morishita, Hiromitsu,Ogiwara, Yohei,Sakai, Norio
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p. 13734 - 13742
(2018/11/03)
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- Palladium-Catalyzed Reductive Coupling Reaction of Terminal Alkynes with Aryl Iodides Utilizing Hafnocene Difluoride as a Hafnium Hydride Precursor Leading to trans-Alkenes
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Herein, we describe a reductive cross-coupling of alkynes and aryl iodides by using a novel catalytic system composed of a catalytic amount of palladium dichloride and a promoter precursor, hafnocene difluoride (Cp2HfF2, Cp=cyclopentadienyl anion), in the presence of a mild reducing reagent, a hydrosilane, leading to a one-pot preparation of trans-alkenes. In this process, a series of coupling reactions efficiently proceeds through the following three steps: (i) an initial formation of hafnocene hydride from hafnocene difluoride and the hydrosilane, (ii) a subsequent hydrohafnation toward alkynes, and (iii) a final transmetalation of the alkenyl hafnium species to a palladium complex. This reductive coupling could be chemoselectively applied to the preparation of trans-alkenes with various functional groups, such as an alkyl group, a halogen, an ester, a nitro group, a heterocycle, a boronic ester, and an internal alkyne.
- Takahashi, Keita,Ogiwara, Yohei,Sakai, Norio
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supporting information
p. 809 - 814
(2018/03/13)
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- O -Iodoxybenzoic acid mediated generation of aryl free radicals: Synthesis of stilbenes through C-C cross-coupling with β-nitrostyrenes
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The generation of an aryl free radicals in the presence of nitrostyrenes through a combination of aryl hydrazines and o-iodoxybenzoic acid led to the synthesis of stilbenes by forming a new carbon-carbon bond after subsequent elimination of a nitrosyl radical. The symmetrical and unsymmetrical stilbenes with excellent E-selectivity were synthesized in good yields, with advantages of broad substrate scope and transition metal free, mild reaction conditions, under an open atmosphere in a short reaction time. A free radical mediated mechanism was postulated and supported by radical trapping experiments. Application of the developed methodology is demonstrated through a simple, two step synthesis of resveratrol, a valuable stilbenoid for anticancer and neurological studies via its prodrug E-1,3-dimethoxy-5-(4-methoxystyryl)benzene.
- Wagh, Ganesh,Autade, Snehalata,Patil, Pravin C.,Akamanchi, Krishnacharya G.
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p. 3301 - 3309
(2018/03/06)
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- Direct Wittig Olefination of Alcohols
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A base-promoted transition metal-free approach to substituted alkenes using alcohols under aerobic conditions using air as the inexpensive and clean oxidant is described. Aldehydes are relatively difficult to handle compared to corresponding alcohols due to their volatility and penchant to polymerize and autoxidize. Wittig ylides are easily oxidized to aldehydes and consequently form homo-olefination products. By the strategy of simultaneously in situ generation of ylides and aldehydes, for the first time, alcohols are directly transferred to olefins with no need of prepreparation of either aldehydes or ylides. Thus, the di/monocontrollable olefination of diols is accomplished. This synthetically practical method has been applied in the gram-scale synthesis of pharmaceuticals, such as DMU-212 and resveratrol from alcohols.
- Li, Qiang-Qiang,Shah, Zaher,Qu, Jian-Ping,Kang, Yan-Biao
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p. 296 - 302
(2018/02/19)
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- Piperidine-appended imidazolium ionic liquid as task-specific basic-IL for Suzuki and Heck reactions and for tandem Wittig-Suzuki, Wittig-Heck, Horner-Emmons-Suzuki, and Horner-Emmons-Heck protocols
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Facile, high yielding, one-pot methods for the synthesis of a library of diversely substituted bi-aryls, diarylethenes, and aryl-enoates, via Suzuki and Heck reactions, and by sequential Wittig-Suzuki, Wittig-Heck, Horner-Emmons-Suzuki, and Horner-Emmons-Heck reactions are reported. The reactions employ piperidine-appended imidazolium ionic liquid [PAIM][NTf2] as a task-specific basic-IL, butyl-methyl-imidazolium ionic liquid [BMIM][X] (X?=?PF6, BF4) as solvent, and catalytic amounts of Pd(OAc)2 with no other additives. Wittig and Horner-Emmons reactions are effected by reacting substituted benzaldehydes with 4-bromobenzyl-PPh3 (or bromomethyl-PPh3) phosphonium salts, or diethylphosphonate with bromobenzaldehydes respectively, to form the corresponding ethenes. Subsequent cross-coupling reactions are accomplished by addition of aryl-boronic acid or phenyl-ethenes along with Pd(OAc)2 to bring about the aforementioned hyphenated transformations. The feasibility to perform double-olefination via Wittig and Horner-Emmons reactions with dialdehydes to form highly conjugated bis-styryl and bis-enoate compounds is also shown. The [BMIM][X] solvent is recycled and reused.
- Savanur, Hemantkumar M.,Kalkhambkar, Rajesh G.,Laali, Kenneth K.
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p. 150 - 161
(2017/06/30)
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- Encaging palladium(0) in layered double hydroxide: A sustainable catalyst for solvent-free and ligand-free Heck reaction in a ball mill
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In this paper, the synthesis of a cheap, reusable and ligand-free Pd catalyst supported on MgAl layered double hydroxides (Pd/MgAl-LDHs) by co-precipitation and reduction methods is described. The catalyst was used in Heck reactions under highspeed ball milling (HSBM) conditions at room temperature. The effects of milling-ball size, milling-ball filling degree, reaction time, rotation speed and grinding auxiliary category, which would influence the yields of mechanochemical Heck reactions, were investigated in detail. The characterization results of XRD, ICP-MS and XPS suggest that Pd/MgAl-LDHs have excellent textural properties with zero-valence Pd on its layers. The reaction results indicate that the catalyst could be utilized in HSBM systems to afford a wide range of Heck coupling products in satisfactory yields. Furthermore, this catalyst could be easily recovered and reused for at least five times without significant loss of catalytic activity.
- Shi, Wei,Yu, Jingbo,Jiang, Zhijiang,Shao, Qiaoling,Su, Weike
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supporting information
p. 1661 - 1668
(2017/09/27)
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- Macrocyclic Pd(II) dithiolate complexes as catalysts in Heck reactions
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The supramolecular palladium dithiolate complexes, [Pd2(dppe)2{S(C6H4)nS}]2(OTf)4and [Pd2(dppe)2(SCH2C6H4CH2S)]
- Mane, Pravin A.,Dey, Sandip,Vivekananda
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