- Chemoselective Hydrogenation of Olefins Using a Nanostructured Nickel Catalyst
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The selective hydrogenation of functionalized olefins is of great importance in the chemical and pharmaceutical industry. Here, we report on a nanostructured nickel catalyst that enables the selective hydrogenation of purely aliphatic and functionalized olefins under mild conditions. The earth-abundant metal catalyst allows the selective hydrogenation of sterically protected olefins and further tolerates functional groups such as carbonyls, esters, ethers and nitriles. The characterization of our catalyst revealed the formation of surface oxidized metallic nickel nanoparticles stabilized by a N-doped carbon layer on the active carbon support.
- Klarner, Mara,Bieger, Sandra,Drechsler, Markus,Kempe, Rhett
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supporting information
p. 2157 - 2161
(2021/05/21)
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- Photo-Initiated Cobalt-Catalyzed Radical Olefin Hydrogenation
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Outer-sphere radical hydrogenation of olefins proceeds via stepwise hydrogen atom transfer (HAT) from transition metal hydride species to the substrate. Typical catalysts exhibit M?H bonds that are either too weak to efficiently activate H2 or too strong to reduce unactivated olefins. This contribution evaluates an alternative approach, that starts from a square-planar cobalt(II) hydride complex. Photoactivation results in Co?H bond homolysis. The three-coordinate cobalt(I) photoproduct binds H2 to give a dihydrogen complex, which is a strong hydrogen atom donor, enabling the stepwise hydrogenation of both styrenes and unactivated aliphatic olefins with H2 via HAT.
- Sang, Sier,Unruh, Tobias,Demeshko, Serhiy,Domenianni, Luis I.,van Leest, Nicolaas P.,Marquetand, Philipp,Schneck, Felix,Würtele, Christian,de Zwart, Felix J.,de Bruin, Bas,González, Leticia,V?hringer, Peter,Schneider, Sven
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p. 16978 - 16989
(2021/08/09)
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- Direct Synthesis of Mono-α-arylated Ketones from Alcohols and Olefins via Ni-Catalyzed Oxidative Cross-Coupling
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Controlled synthesis of α-monoarylated ketones is significant yet challenging due to the site-selectivity issues and nonproductive overarylation reactions. Herein, we reported the direct synthesis of α-arylated ketones enabled by Ni-catalyzed dehydrogenative cross-coupling reaction cascade between alcohols and olefins. The use of readily available and cost-effective alcohols and olefins provides a straightforward access to monoarylated ketones in good yields with exclusive selectivity without using any advanced synthetic intermediates.
- Yang, Peng-Fei,Shu, Wei
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supporting information
p. 6203 - 6208
(2020/08/12)
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- Generalized Chemoselective Transfer Hydrogenation/Hydrodeuteration
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A generalized, simple and efficient transfer hydrogenation of unsaturated bonds has been developed using HBPin and various proton reagents as hydrogen sources. The substrates, including alkenes, alkynes, aromatic heterocycles, aldehydes, ketones, imines, azo, nitro, epoxy and nitrile compounds, are all applied to this catalytic system. Various groups, which cannot survive under the Pd/C/H2 combination, are tolerated. The activity of the reactants was studied and the trends are as follows: styrene'diphenylmethanimine'benzaldehyde'azobenzene'nitrobenzene'quinoline'acetophenone'benzonitrile. Substrates bearing two or more different unsaturated bonds were also investigated and transfer hydrogenation occurred with excellent chemoselectivity. Nano-palladium catalyst in situ generated from Pd(OAc)2 and HBPin extremely improved the TH efficiency. Furthermore, chemoselective anti-Markovnikov hydrodeuteration of terminal aromatic olefins was achieved using D2O and HBPin via in situ HD generation and discrimination. (Figure presented.).
- Wang, Yong,Cao, Xinyi,Zhao, Leyao,Pi, Chao,Ji, Jingfei,Cui, Xiuling,Wu, Yangjie
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supporting information
p. 4119 - 4129
(2020/08/10)
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- Environmentally responsible, safe, and chemoselective catalytic hydrogenation of olefins: ppm level Pd catalysis in recyclable water at room temperature
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Textbook catalytic hydrogenations are typically presented as reactions done in organic solvents and oftentimes under varying pressures of hydrogen using specialized equipment. Catalysts new and old are all used under similar conditions that no longer reflect the times. By definition, such reactions are both environmentally irresponsible and dangerous, especially at industrial scales. We now report on a general method for chemoselective and safe hydrogenation of olefins in water using ppm loadings of palladium from commercially available, inexpensive, and recyclable Pd/C, together with hydrogen gas utilized at 1 atmosphere. A variety of alkenes is amenable to reduction, including terminal, highly substituted internal, and variously conjugated arrays. In most cases, only 500 ppm of heterogeneous Pd/C is sufficient, enabled by micellar catalysis used in recyclable water at room temperature. Comparison with several newly introduced catalysts featuring base metals illustrates the superiority of chemistry in water.
- Gallou, Fabrice,Gao, Eugene S.,Lipshutz, Bruce H.,Takale, Balaram S.,Thakore, Ruchita R.
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supporting information
p. 6055 - 6061
(2020/10/14)
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- Regioselective differentiation of vicinal methylene C-H bonds enabled by silver-catalysed nitrene transfer
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Silver-catalyzed nitrene insertion enables the formation of benzosultams in good yield and with regioselectivity complementary to other transition metal nitrene-transfer catalysts. Preferential formation of six-membered benzosultam rings predominates for alkyl-substituted benzenesulphonamide precursors. Ligand-controlled tunability is also achieved for benzenesulphonamides with γ-branched alkyl substituents. Mechanistic probes suggest that the reaction pathway differs depending on whether a α (benzylic) or β (homobenzylic) C-H bond undergoes amidation, as well as the catalyst identity.
- Scamp, Ryan J.,Scheffer, Bradley,Schomaker, Jennifer M.
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p. 7362 - 7365
(2019/06/27)
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- Exploiting the trifluoroethyl group as a precatalyst ligand in nickel-catalyzed Suzuki-type alkylations
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We report herein the exploitment of the partially fluorinated trifluoroethyl as precatalyst ligands in nickel-catalyzed Suzuki-type alkylation and fluoroalkylation coupling reactions. Compared with the [LnNiII(aryl)(X)] precatalysts, the unique characters of bis-trifluoroethyl ligands imparted precatalyst [(bipy)Ni(CH2CF3)2] with bench-top stability, good solubilities in organic media and interesting catalytic activities. Preliminary mechanistic studies reveal that an eliminative extrusion of a vinylidene difluoride (VDF, CH2CF2) mask from [(bipy)Ni(CH2CF3)2] is a critical step for the initiation of a catalytic reaction.
- Yang, Yi,Zhou, Qinghai,Cai, Junjie,Xue, Teng,Liu, Yingle,Jiang, Yan,Su, Yumei,Chung, Lungwa,Vicic, David A.
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p. 5275 - 5282
(2019/05/29)
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- Nickel-Catalyzed Stereodivergent Synthesis of E- and Z-Alkenes by Hydrogenation of Alkynes
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A convenient protocol for stereodivergent hydrogenation of alkynes to E- and Z-alkenes by using nickel catalysts was developed. Simple Ni(NO3)2?6 H2O as a catalyst precursor formed active nanoparticles, which were effective for the semihydrogenation of several alkynes with high selectivity for the Z-alkene (Z/E>99:1). Upon addition of specific multidentate ligands (triphos, tetraphos), the resulting molecular catalysts were highly selective for the E-alkene products (E/Z>99:1). Mechanistic studies revealed that the Z-alkene-selective catalyst was heterogeneous whereas the E-alkene-selective catalyst was homogeneous. In the latter case, the alkyne was first hydrogenated to a Z-alkene, which was subsequently isomerized to the E-alkene. This proposal was supported by density functional theory calculations. This synthetic methodology was shown to be generally applicable in >40 examples and scalable to multigram-scale experiments.
- Murugesan, Kathiravan,Bheeter, Charles Beromeo,Linnebank, Pim R.,Spannenberg, Anke,Reek, Joost N. H.,Jagadeesh, Rajenahally V.,Beller, Matthias
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p. 3363 - 3369
(2019/06/28)
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- Iridium-Catalyzed Alkene-Selective Transfer Hydrogenation with 1,4-Dioxane as Hydrogen Donor
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The iridium-catalyzed transfer hydrogenation of alkenes using 1,4-dioxane as a hydrogen donor is described. The use of 1,2-bis(dicyclohexylphosphino)ethane (DCyPE), featuring bulky and highly electron-donating properties, led to high catalytic activity. A polystyrene-cross-linking bisphosphine PS-DPPBz produced a reusable heterogeneous catalyst. These homogeneous and heterogeneous protocols achieved chemoselective transfer hydrogenation of alkenes over other potentially reducible functional groups such as carbonyl, nitro, cyano, and imino groups in the same molecule.
- Zhang, Deliang,Iwai, Tomohiro,Sawamura, Masaya
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supporting information
p. 5867 - 5872
(2019/08/26)
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- Monodisperse CuPt alloy nanoparticles assembled on reduced graphene oxide as catalysts in the transfer hydrogenation of various functional organic groups
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We present herein a new nanocatalyst, namely binary CuPt alloy nanoparticles (NPs) supported on reduced graphene oxide (CuPt-rGO), as a highly active heterogeneous catalyst for the transfer hydrogenation (TH) protocol that is demonstrated to be applicable over the reduction of various unsaturated organic compounds (olefins, aldehydes/ketones and nitroarenes) in aqueous solutions at room temperature. CuPt alloy NPs were synthesized by the co-reduction of metal (II) acetylacetonates by borane-tert-butylamine (BTB) complex in hot oleylamine (OAm) solution and then assembled on reduced graphene oxide (rGO) via ultrasonic-assisted liquid phase self-assembly method. The structure of yielded CuPt NPs and CuPt-rGO nanocatalyst were characterized by TEM, XRD and ICP-MS. The activity of Cu7Pt3-rGO nanocatalysts were then tested for the THs that were conducted in a commercially available high-pressure tube using water as sole solvent and ammonia borane as a hydrogen donor at room temperature. The presented catalytic TH protocol was successfully applied over nitroarenes, olefines and aldehydes/ketones, and all the tested compounds were converted to corresponding reduction products with the yields reaching up to 99% under ambient conditions. Moreover, the Cu7Pt3-rGO nanocatalyst was also reusable in the TH by providing 99% yield after five consecutive runs in TH of nitrobenzene as an example.
- Ganjehyan, Khadijeh,Ni?anc?, Bilal,Sevim, Melike,Da?tan, Arif,Metin, ?nder
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- Dendrimer-Encapsulated Pd Nanoparticles, Immobilized in Silica Pores, as Catalysts for Selective Hydrogenation of Unsaturated Compounds
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Heterogeneous Pd-containing nanocatalysts, based on poly (propylene imine) dendrimers immobilized in silica pores and networks, obtained by co-hydrolysis in situ, have been synthesized and examined in the hydrogenation of various unsaturated compounds. The catalyst activity and selectivity were found to strongly depend on the carrier structure as well as on the substrate electron and geometric features. Thus, mesoporous catalyst, synthesized in presence of both polymeric template and tetraethoxysilane, revealed the maximum activity in the hydrogenation of various styrenes, including bulky and rigid stilbene and its isomers, reaching TOF values of about 230000 h?1. Other mesoporous catalyst, synthesized in the presence of polymeric template, but without addition of Si(OEt)4, provided the trans-cyclooctene formation with the selectivity of 90–95 %, appearing as similar to homogeneous dendrimer-based catalysts. Microporous catalyst, obtained only on the presence of Si(OEt)4, while dendrimer molecules acting as both anchored ligands and template, demonstrated the maximum activity in the hydrogenation of terminal linear alkynes and conjugated dienes, reaching TOF values up to 400000 h?1. Herein the total selectivity on alkene in the case of terminal alkynes and conjugated dienes reached 95–99 % even at hydrogen pressure of 30 atm. The catalysts synthesized can be easily isolated from reaction products and recycled without significant loss of activity.
- Karakanov, Edward A.,Zolotukhina, Anna V.,Ivanov, Andrey O.,Maximov, Anton L.
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p. 358 - 381
(2019/04/04)
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- Room temperature catalytic dehydrogenation of cyclic amines with the liberation of H2 using water as a solvent
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Catalytic dehydrogenation of cyclic amines, in particular partially saturated N-heterocycles to N-heterocyclic arenes, with the removal of molecular hydrogen as the sole byproduct in water is reported. This dehydrogenation reaction proceeds smoothly under very mild and benign conditions and operates at room temperature. This distinctive reactivity has been achieved under dual catalytic conditions by merging the visible-light active [Ru(bpy)3]2+ as the photoredox catalyst and a newly synthesized cobalt complex as the proton-reduction catalyst. A detailed mechanistic study (control experiments, electrochemical studies, UV-visible experiments) is presented for the present dual catalysis.
- Sahoo, Manoj K.,Balaraman, Ekambaram
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supporting information
p. 2119 - 2128
(2019/04/26)
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- Mechanism of the Bis(imino)pyridine-Iron-Catalyzed Hydromagnesiation of Styrene Derivatives
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Iron-catalyzed hydromagnesiation of styrene derivatives offers a rapid and efficient method to generate benzylic Grignard reagents, which can be applied in a range of transformations to provide products of formal hydrofunctionalization. While iron-catalyzed methodologies exist for the hydromagnesiation of terminal alkenes, internal alkynes, and styrene derivatives, the underlying mechanisms of catalysis remain largely undefined. To address this issue and determine the divergent reactivity from established cross-coupling and hydrofunctionalization reactions, a detailed study of the bis(imino)pyridine iron-catalyzed hydromagnesiation of styrene derivatives is reported. Using a combination of kinetic analysis, deuterium labeling, and reactivity studies as well as in situ 57Fe M?ssbauer spectroscopy, key mechanistic features and species were established. A formally iron(0) ate complex [iPrBIPFe(Et)(CH2a?CH2)]- was identified as the principle resting state of the catalyst. Dissociation of ethene forms the catalytically active species which can reversibly coordinate the styrene derivative and mediate a direct and reversible β-hydride transfer, negating the necessity of a discrete iron hydride intermediate. Finally, displacement of the tridentate bis(imino)pyridine ligand over the course of the reaction results in the formation of a tris-styrene-coordinated iron(0) complex, which is also a competent catalyst for hydromagnesiation.
- Neate, Peter G. N.,Greenhalgh, Mark D.,Brennessel, William W.,Thomas, Stephen P.,Neidig, Michael L.
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supporting information
p. 10099 - 10108
(2019/07/04)
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- Mechanistic Aspects of a Surface Organovanadium(III) Catalyst for Hydrocarbon Hydrogenation and Dehydrogenation
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Understanding the mechanisms of action for base metal catalysis of transformations typically associated with precious metals is essential for the design of technologies for a sustainable energy economy. Isolated transition-metal and post-transition-metal catalysts on oxides such as silica are generally proposed to effect hydrogenation and dehydrogenation by a mechanism featuring either σ-bond metathesis or heterolytic bond cleavage as the key bond activation step. In this work, an organovanadium(III) complex on silica, which is a precatalyst for both olefin hydrogenation and alkane dehydrogenation, is interrogated by a series of reaction kinetics and isotopic labeling studies in order to shed light on the operant mechanism for hydrogenation. The kinetic dependencies of the reaction components are potentially consistent with both the σ-bond metathesis and the heterolytic bond activation mechanisms; however, a key deuterium incorporation experiment definitively excludes the simple σ-bond metathesis mechanism. Alternatively, a two-electron redox cycle, rarely invoked for homologous catalyst systems, is also consistent with experimental observations. Evidence supporting the formation of a persistent vanadium(III) hydride upon hydrogen treatment of the as-prepared material is also presented.
- Kaphan, David M.,Ferrandon, Magali S.,Langeslay, Ryan R.,Celik, Gokhan,Wegener, Evan C.,Liu, Cong,Niklas, Jens,Poluektov, Oleg G.,Delferro, Massimiliano
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p. 11055 - 11066
(2019/11/16)
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- Improving Catalytic Hydrogenation Performance of Pd Nanoparticles by Electronic Modulation Using Phosphine Ligands
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Tuning the activity and selectivity of metal nanoparticles (NPs) is a long-term pursuit in the field of catalysis. Herein, we report successfully improving both the activity and chemoselectivity of Pd NPs (1.1 nm) with triphenylphosphine (PPh3) cross-linked in the nanopore of FDU-12. The electron-donating effect of PPh3 increases the surface electronic density of Pd NPs and weakens the Pd-H bond, as evidenced by the results of XPS, in situ FT-IR adsorption of CO, and H2-D2 exchange reactions. Consequently, Pd NPs modified with PPh3 obtain >99% selectivity to 1-phenylethanol in acetophenone hydrogenation and 94% selectivity to styrene in phenylacetylene hydrogenation. Furthermore, the activity of Pd NPs is enhanced and suppressed by PPh3, respectively, in the hydrogenation of electrophilic nitro compounds and nucleophilic carbonyl substrates. Our primary results shed some light on judiciously choosing organic ligands for modifying the catalytic performance of metal NPs toward specific chemical transformations.
- Guo, Miao,Li, He,Ren, Yiqi,Ren, Xiaomin,Yang, Qihua,Li, Can
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p. 6476 - 6485
(2018/06/18)
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- Palladium-catalyzed regioselective hydroboration of aryl alkenes with B2pin2
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A palladium(ii)-catalyzed hydroboration of aryl alkenes with stable and easy-to-handle (pinacolato)diboron (B2pin2) under mild conditions has been developed. Acetic acid acted as the solvent and the hydrogen source, which has been identified by deuterium experiments. Notably, isomerization-hydroboration of allyl benzene derivatives was observed. As a result, a series of benzyl boronic esters were obtained in moderate to excellent yields with exclusive regioselectivity.
- Huang, Jiuzhong,Yan, Wuxin,Tan, Chaowei,Wu, Wanqing,Jiang, Huanfeng
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supporting information
p. 1770 - 1773
(2018/02/21)
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- Reduction of phenylacetylenes using Raney Ni-Al alloy, Al powder in the presence of noble metal catalysts in water
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The chemoselective reduction is based on the reaction between Al either as powder or from the alloy and water which generates in situ hydrogen to effect the reduction of the targeted functional groups. Raney Ni-Al alloy with Al powder can reduce phenylacetylenes to the corresponding ethylbenzene (3) in water in excellent yield at 120 °C for 6 h in a sealed tube. In addition, the complete reduction of the aromatic ring to ethylcyclohexane required 60 °C for 12 h with Raney Ni-Al alloy, Al powder in the presence of Pt/C. Appropriate selection of reaction conditions allowed the selective preparation of ethylbenzene as well as ethylcyclohexane from phenylacetylene.
- Rayhan, Ummey,Kowser, Zannatul,Islam, Md. Nurul,Redshaw, Carl,Yamato, Takehiko
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supporting information
p. 241 - 251
(2018/02/07)
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- A Pd-Cu2O nanocomposite as an effective synergistic catalyst for selective semi-hydrogenation of the terminal alkynes only
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A new type lead-free catalyst of a Pd-Cu2O nanocomposite was developed for highly selective semi-hydrogenation of alkynes. With unprecedented selectivity for the semi-hydrogenation of terminal alkynes to alkenes, we show for the first time that the catalyst only hydrogenated the terminal alkynes, i.e. did not hydrogenate the internal alkynes.
- Yang, Shuliang,Cao, Changyan,Peng, Li,Zhang, Jianling,Han, Buxing,Song, Weiguo
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supporting information
p. 3627 - 3630
(2016/03/05)
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- Immobilized ruthenium metal-containing ionic liquid-catalyzed dehydrogenation of dimethylamine borane complex for the reduction of olefins and nitroarenes
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An efficient immobilized ruthenium metal containing ionic liquid (ImmRu-IL) catalyst has been developed for the transfer hydrogenation of olefins and nitroarenes. Various olefins and nitroarenes were reduced in excellent yields within 2-6 h at room temperature. This methodology uses eco-friendly dimethylamine borane as a reducing agent which is nontoxic, water soluble, highly stable and easy to handle. The reactions take place through tandem dehydrogenation and hydrogenation of dimethylamine borane complex in the presence of ImmRu-IL catalyst. The catalyst was reused in up to four consecutive cycles without any significance loss in its activity. The fresh and reused catalysts have been studied by XPS analysis.
- Patil, Nilesh M.,Sasaki, Takehiko,Bhanage, Bhalchandra M.
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supporting information
p. 52347 - 52352
(2016/06/13)
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- Metal-Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations
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New and active earth-abundant metal catalysts are critically needed to replace precious metal-based catalysts for sustainable production of commodity and fine chemicals. We report here the design of highly robust, active, and reusable cobalt-bipyridine- and cobalt-phenanthroline-based metal-organic framework (MOF) catalysts for alkene hydrogenation and hydroboration, aldehyde/ketone hydroboration, and arene C-H borylation. In alkene hydrogenation, the MOF catalysts tolerated a variety of functional groups and displayed unprecedentedly high turnover numbers of ~2.5 × 106 and turnover frequencies of ~1.1 × 105 h-1. Structural, computational, and spectroscopic studies show that site isolation of the highly reactive (bpy)Co(THF)2 species in the MOFs prevents intermolecular deactivation and stabilizes solution-inaccessible catalysts for broad-scope organic transformations. Computational, spectroscopic, and kinetic evidence further support a hitherto unknown (bpy?-)CoI(THF)2 ground state that coordinates to alkene and dihydrogen and then undergoing σ-complex-assisted metathesis to form (bpy)Co(alkyl)(H). Reductive elimination of alkane followed by alkene binding completes the catalytic cycle. MOFs thus provide a novel platform for discovering new base-metal molecular catalysts and exhibit enormous potential in sustainable chemical catalysis.
- Zhang, Teng,Manna, Kuntal,Lin, Wenbin
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supporting information
p. 3241 - 3249
(2016/03/19)
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- Enhanced Reactivity of Aerobic Diimide Olefin Hydrogenation with Arylboronic Compounds: An Efficient One-Pot Reduction/Oxidation Protocol
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A catalyst-free and efficient method for simultaneous olefin hydrogenation and oxidation of arylboronate esters to phenols with hydrazine hydrate and molecular oxygen is presented. The process is based on the utilization of a readily available Lewis acidic arylboron compound, which evades common problems associated with the catalyst-free aerobic hydrogenation of olefins with diimide. Using an operationally simple procedure, the protocol smoothly delivers phenol derivatives and various alkanes in excellent yields with remarkable functional group compatibility. The method allows the reaction to be scaled up to 1 g of the starting materials.
- Santra, Surojit,Guin, Joyram
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supporting information
p. 7253 - 7257
(2015/11/25)
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- Alkylation of pyridines at their 4-positions with styrenes plus yttrium reagent or benzyl grignard reagents
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A new regioselective alkylation of pyridines at their 4-position was achieved with styrenes in the presence of yttrium trichloride, BuLi, and diisobutylaluminium hydride (DIBAL-H) in THF. Alternatively, similar products were more simply prepared from pyridines and benzyl Grignard reagents. These reactions are not only a useful preparation of 4-substituted pyridines but are also complementary to other relevant reactions usually giving 2-substituted pyridines.
- Mizumori, Tomoya,Hata, Takeshi,Urabe, Hirokazu
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supporting information
p. 422 - 426
(2015/02/19)
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- A green approach for the decoration of Pd nanoparticles on graphene nanosheets: An in situ process for the reduction of C-C double bonds and a reusable catalyst for the Suzuki cross-coupling reaction
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A new strategy for in situ synthesis of palladium nanoparticles (Pd NPs) decorated on reduced graphene oxide (rGO) nanosheets with controlled size and shape is reported. This strategy was designed as three processes in one pot, namely, (a) reduction of graphene oxide, (b) formation of Pd NPs on the rGO nanosheets and (c) simultaneous reduction of olefin. In this synthesis process, a hydrogen atmosphere was used to develop the Pd NPs-rGO nanocatalyst, which is reusable and easily separable. The influence of the size and morphology of the Pd-rGO-H2 catalyst on the catalytic activity in the Suzuki cross-coupling reaction was investigated by comparing with other catalysts, Pd-rGO-As and Pd-rGO-Gl, and they were synthesized by different reducing agents, ascorbic acid and glucose, respectively. The catalysts were characterized by electron microscopy (HRTEM, SEM), FT-IR, XRD and XPS. The Pd-rGO-H2 catalyst was found to possess excellent catalytic activity and recyclability in the Suzuki cross-coupling reaction under mild reaction conditions.
- Hussain, Najrul,Borah, Ashwini,Darabdhara, Gitashree,Gogoi, Pranjal,Azhagan, Vedi Kuyil,Shelke, Manjusha V.,Das, Manash R.
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p. 6631 - 6641
(2015/08/06)
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- Palladium nanoparticles encapsulated in a dendrimer networks as catalysts for the hydrogenation of unsaturated hydrocarbons
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A novel method has been proposed for encapsulating palladium nanoparticles up to 5 nm in the matrix of polymeric support networks based on polyamidoamine dendrimers. The shape of the particle size distribution and the catalytic activity of the materials obtained during the hydrogenation of unsaturated compounds depend strongly on the support structure. High activity (TOF up to 86,000 h-1) has been observed during the hydrogenation of styrene.
- Karakhanov, Edward A.,Maksimov, Anton L.,Zakharian, Elena M.,Kardasheva, Yulia S.,Savilov, Sergey V.,Truhmanova, Nadezhda I.,Ivanov, Andrey O.,Vinokurov, Vladimir A.
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- Flavin-functionalized gold nanoparticles as an efficient catalyst for aerobic organic transformations
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Monolayer-protected gold clusters functionalized with synthetic flavins were synthesized and their catalytic activity in aerobic organic transformations investigated. Gold nanoparticles with 5-ethyl-3-(8-thiooctyl)lumiflavinium perchlorate acts as an efficient catalyst for the aerobic oxidation of organic sulfides to the corresponding sulfoxides upon treatment with hydrazine at room temperature and under atmospheric pressure in oxygen. With a catalytic amount of gold nanoparticles with 3-(8-thiooctyl)lumiflavin, diimide reduction of various olefins can be performed with hydrazine at room temperature under atmospheric pressure in air with greater yields of product alkanes than with non-supported 3-methyllumiflavin catalyst under the same conditions. Kinetic studies revealed that the mono-layer-protected gold cluster-catalyzed reactions proceeded faster than those with non-supported catalysts over the full substrate concentration range for the hydrogenation of olefins and at lower substrate concentrations for sulfoxidation. This positive effect was rationalized by assuming a Michaelis-Menten-type mechanism in which the specific inclusion of substrates into the enzyme-like reaction cavities was a key factor in the high efficiency of the supported flavin catalysts.
- Imada, Yasushi,Osaki, Motonari,Noguchi, Mikiko,Maeda, Takatoshi,Fujiki, Misa,Kawamorita, Soichiro,Komiya, Naruyoshi,Naota, Takeshi
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- An unprecedented anionic Ln-MOF with a cage-within-cage motif: Spontaneous reduction and immobilization of ion-exchanged Pd(II) to Pd-NPs in the framework
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An unprecedented microporous anionic Ln-MOF, [Me2NH2]24[Tb12(TATB)16(HCOO)12]·12DMF·48H2O (1) (H3TATB = 4,4′,4′′-s-triazine-2,4,6-tribenzoic acid), which is a rare cage-within-cage structure through interpenetration rather than covalent bonding, has been synthesized. Compound 1 contains a 3D net which is constructed using a large and a small Ln-carboxylate cage alternately arranged by sharing faces with each other. Interpenetration of two identical 3D nets occurs in such a way that each small cage of one net is encapsulated within the large cage of the other and vice versa, generating an overall 3D double-walled cage framework. Such interpenetration creates a unique structure of double-shelled hollow space to accommodate Pd nanoparticles (Pd-NPs), which could effectively prevent Pd-NPs from aggregation and leaching. Moreover, the ion-exchanged Pd(ii) embedded in the framework can be readily reduced at room temperature with no requirement of any chemical or thermal treatments, affording Pd-NPs with uniform size and even distribution. As a result, the as-prepared Pd-NPs@1 exhibits excellent activity and cycling stability for the hydrogenation of styrene and its derivatives.
- Han, Yun-Hu,Tian, Chong-Bin,Lin, Ping,Du, Shao-Wu
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p. 24525 - 24531
(2015/12/09)
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- BMIm-PF6@SiO2 Microcapsules: Particulated ionic liquid as a new material for the heterogenization of catalysts
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A method for the preparation of silica microcapsules containing a high loading of ionic liquids (ILs) is described. The method paves the way to the conversion of ionic liquids into particulated materials, which results in ILs with new properties without changing their molecular structures. The synthesis of these new materials is based on the emulsification of ionic liquids in water, using surfactants or dispersants, and the resulting ionic liquid droplets are then confined in a silica shell formed via interfacial hydrolysis and polycondensation of tetraethoxysilane. This material can be isolated by centrifugation, followed by drying to yield a fine powder of ionic liquid-silica microcapsules, which are water and organic solvents redispersible. These new materials are utilized in the heterogenization of palladium catalyst and then applied in the hydrogenation of alkynes. The catalyst shows chemoselectivity in the hydrogenation of internal alkynes such as 4-octyne. Comparative studies have shown that the same catalyst loses this selectivity when it is applied under homogeneous conditions.
- Weiss, Ester,Dutta, Bishnu,Kirschning, Andreas,Abu-Reziq, Raed
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p. 4781 - 4787
(2014/11/07)
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- Photodriven Transfer Hydrogenation of Olefins
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An improved practical method for the photodriven diimide reduction of olefins was investigated. This catalyst-free procedure proceeds at ambient temperature, utilizes air as oxidant and a lower hydrazine loading, and produces inert nitrogen gas as the sole byproduct. Several functional groups were tolerated, and in some cases, the reaction was chemoselective. Challenging substrates such as cinnamate ester derivatives and trans-stilbene were reduced in excellent yields. The small amount of UVA rays emitted from a household compact fluorescent light bulb was proposed to enable the cis/trans isomerization of the diimide and to promote the loss of hydrogen from the diimide.
- Leow, Dasheng,Chen, Ying-Ho,Hung, Tzu-Hang,Su, Ying,Lin, Yi-Zhen
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supporting information
p. 7347 - 7352
(2016/02/18)
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- Iron-catalysed, general and operationally simple formal hydrogenation using Fe(OTf)3 and NaBH4
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An operationally simple and environmentally benign formal hydrogenation protocol has been developed using highly abundant iron(iii) salts and an inexpensive, bench stable, stoichiometric reductant, NaBH4, in ethanol, under ambient conditions. This reaction has been applied to the reduction of terminal alkenes (22 examples, up to 95% yield) and nitro-groups (26 examples, up to 95% yield). Deuterium labelling studies indicate that this reaction proceeds via an ionic rather than radical mechanism.
- MacNair, Alistair J.,Tran, Ming-Ming,Nelson, Jennifer E.,Sloan, G. Usherwood,Ironmonger, Alan,Thomas, Stephen P.
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supporting information
p. 5082 - 5088
(2014/07/08)
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- Room-temperature transfer hydrogenation and fast separation of unsaturated compounds over heterogeneous catalysts in an aqueous solution of formic acid
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The facile conversion of olefins and unsaturated biomass to saturated compounds is achieved over heterogeneous catalysts composed of noble metal nanoparticles and carbon nitride. Reactions could proceed smoothly at room temperature in water using formic acid as the hydrogen source. The reusability of such a hybrid catalyst is high due to the strong Mott-Schottky effect between the metal nanoparticles and the carbon nitride support. The fast and automatic separation of the as-formed saturated hydrocarbons from water combined with the mild reaction conditions and the excellent reusability of catalysts make the catalytic process a highly "green" path for hydrogenation of unsaturated compounds and biofuel upgrading. This journal is the Partner Organisations 2014.
- Gong, Ling-Hong,Cai, Yi-Yu,Li, Xin-Hao,Zhang, Ya-Nan,Su, Juan,Chen, Jie-Sheng
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p. 3746 - 3751
(2014/08/05)
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- Effects of crystallinity of ZSM-5 zeolite on para-selective tert-butylation of ethylbenzene
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Highly crystalline ZSM-5 zeolites are important for para-selective alkylation of alkyl aromatics, because they carry few external acid sites for isomerization of p-dialkyl products. Such zeolites (Si/Al = 25, 50, and 75) were synthesized in a fluoride medium between pH 4 and 6. Their crystallinities, crystal sizes, and surface areas were higher than those of a commercial ZSM-5 zeolite. Their para selectivities in alkylation were tested for vapor-phase tert-butylation of ethylbenzene between 200 and 400 °C. As expected, all the catalysts showed more than 90% para selectivity. At 300 °C, ethylbenzene conversion decreased in the order ZSM-5(25, commercial) > ZSM-5(25) > ZSM-5(50) > ZSM-5(75). The catalysts had weak, medium, and strong acid sites, but all the acid sites of ZSM-5(75) were weaker than those of ZSM-5(25) and ZSM-5(50). The high activity of commercial ZSM-5 was caused by its strong acid sites being stronger than those of the synthesized zeolites. Although the activity of the commercial catalyst was higher than those of the present catalysts, the selectivity for 4-t-butylethylbenzene (4-t-BEB) was low. The optimum feed ratio (ethylbenzene:t-butyl alcohol) was 2:1 and the feed rate was 1.65 h-1 for high ethylbenzene conversion and 4-t-BEB selectivity. Time-on-stream studies showed slow catalyst deactivation. Highly crystalline ZSM-5 zeolites are therefore better than a commercial zeolite for para-selective alkylation of alkyl aromatics. They do not require much post-modification for high para selectivity. A fluoride medium is therefore better than an alkaline medium for obtaining highly crystalline para-selective ZSM-5 zeolites.
- Pushparaj, Hemalatha,Mani, Ganesh,Muthiahpillai, Palanichamy,Velayutham, Murugesan,Park, Yong-Ki,Choi, Won Choon,Jang, Hyun Tae
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p. 294 - 304
(2013/04/10)
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- Hydrogen-free alkene reduction in continuous flow
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The first continuous hydrogenation that requires neither H2 nor metal catalysis generates diimide by a novel reagent combination. The simple flow reactor employed minimizes residence time by enabling safe operation at elevated temperature.
- Kleinke, Andrew S.,Jamison, Timothy F.
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supporting information
p. 710 - 713
(2013/03/29)
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- Iron-catalysed reduction of olefins using a borohydride reagent
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The iron-catalysed reduction of olefins has been achieved using a simple iron salt and sodium triethylborohydride. A wide range of mono- and trans-1,2-disubstituted alkenes have been reduced (91-100%) using 25 mol% iron(II) triflate, 1 mol% N-methyl-2-pyrrolidinone and 4 equivalents of sodium triethylborohydride. The reduction of alkynes to alkanes is also reported (up to 84%). Significantly, the reduction of trisubstituted alkenes has also been achieved (60-86%). Copyright
- Carter, Tom S.,Guiet, Lea,Frank, Dominik J.,West, James,Thomas, Stephen P.
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supporting information
p. 880 - 884
(2013/05/08)
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- Iron-catalysed alkene hydrogenation and reductive cross-coupling using a bench-stable iron(II) pre-catalyst
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Operationally simple, iron-catalysed hydrogenation and reductive cross-coupling protocols have been developed using a bench-stable iron(ii) pre-catalyst. The hydrogenation of 18 alkenes (50-99%) and reductive cross-coupling of vinyl halides with aryl- and alkyl Grignard reagents (8 examples, 18-99%) is reported using 3 mol% pre-catalyst and hydrogen as stoichiometric reductant (1-50 bar).
- Frank, Dominik J.,Guiet, Lea,Kaeslin, Alexander,Murphy, Elliot,Thomas, Stephen P.
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p. 25698 - 25701
(2013/12/04)
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- Pd-aminoclay nanocomposite as an efficient recyclable catalyst for hydrogenation and suzuki cross coupling reactions
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A highly water dispersible Pd-aminoclay nanocomposite is found to be effective catalytic system for the hydrogenation of α,β-unsaturated carbonyl compounds and Suzuki coupling reactions in aqueous media. The catalytic hydrogenation of α,β-unsaturated carbonyl compounds proceeds at room temperature to afford the corresponding products in excellent yields with high chemoselectivity. The cross coupling of aryl bromides and iodides with aryl boronic acids proceeds efficiently under aqueous conditions at 90 °C to afford the corresponding biaryls in excellent yields with high selectivity. The Suzuki reaction proceeds smoothly even in the absence of external base due to the basic nature of the catalyst support. The catalyst could be easily recovered and recycled three times without a significant loss of activity in hydrogenation and Suzuki cross coupling reactions. Copyright
- Kumar, A. Sravanth,Datta,Rao, T. Srinivasa,Raghavan,Eswaramoorthy,Reddy, B.V. Subba
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experimental part
p. 2000 - 2007
(2012/07/28)
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- Chemoselective hydrogenation using molecular sieves-supported Pd catalysts: Pd/MS3A and Pd/MS5A
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Palladium catalysts embedded on molecular sieves (MS3A and MS5A) were prepared by the adsorption of Pd(OAc)2 onto molecular sieves with its in situ reduction to Pd0 by MeOH as a reducing agent and solvent. 0.5% Pd/MS3A and 0.5% Pd/MS5A catalyzed the hydrogenation of alkynes, alkenes, and azides with a variety of coexisting reducible functionalities, such as nitro group, intact. It is noteworthy that terminal alkenes of styrene derivatives possessing electron-donating functionalities on the benzene nucleus were never hydrogenated under 0.5% Pd/MS5A-catalyzed conditions, while internal alkenes of 1-propenylbenzene derivatives were readily reduced to the corresponding alkanes.
- Takahashi, Tohru,Yoshimura, Masatoshi,Suzuka, Hiroyasu,Maegawa, Tomohiro,Sawama, Yoshinari,Monguchi, Yasunari,Sajiki, Hironao
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experimental part
p. 8293 - 8299
(2012/09/21)
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- Palladium nanoparticles on dendrimer-containing supports as catalysts for hydrogenation of unsaturated hydrocarbons
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A new method has been proposed for encapsulation of palladium nanoparticles with a size of up to 2.5 nm in the matrix of special supports, the polymer networks based on poly(propylene imine) dendrimers, synthesized for this purpose. It has been shown that the particle size distribution of the materials obtained and their catalytic activity in the hydrogenation reactions of unsaturated compounds substantially depend on the specific features of the support structure. A high activity (TOF up to 15000 h-1) has been observed in the hydrogenation of styrene. The catalysts can be repeatedly used without loss of activity. Pleiades Publishing, Ltd., 2012.
- Karakhanov,Maksimov,Zolotukhina,Kardashev,Filippova
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p. 289 - 298
(2013/01/16)
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- Aerobic reduction of olefins by in situ generation of diimide with synthetic flavin catalysts
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A versatile reducing agent, diimide, can be generated efficiently by the aerobic oxidation of hydrazine with neutral and cationic synthetic flavin catalysts 1 and 2. This technique provides a convenient and safe method for the aerobic reduction of olefins, which proceeds with 1 equiv of hydrazine under an atmosphere of O2 or air. The synthetic advantage over the conventional gas-based method has been illustrated through high hydrazine efficiency, easy and safe handling, and characteristic chemoselectivity. Vitamin B2 derivative 6 acts as a highly practical, robust catalyst for this purpose because of its high availability and recyclability. Association complexes of 1b with dendritic 2,5-bis(acylamino)pyridine 15 exhibit unprecedented catalytic activities, with the reduction of aromatic and hydroxy olefins proceeding significantly faster when a higher-generation dendrimer is used as a host pair for the association catalysts. Contrasting retardation is observed upon similar treatment of non-aromatic or non-hydroxy olefins with the dendrimer catalysts. Control experiments and kinetic studies revealed that these catalytic reactions include two independent, anaerobic and aerobic, processes for the generation of diimide from hydrazine. Positive and negative dendrimer effects on the catalytic reactions have been ascribed to the specific inclusion of hydrazine and olefinic substrates into the enzyme-like reaction cavities of the association complex catalysts. Copyright
- Imada, Yasushi,Iida, Hiroki,Kitagawa, Takahiro,Naota, Takeshi
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supporting information; experimental part
p. 5908 - 5920
(2011/07/07)
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- Comparison of the regiochemical behavior of zirconium and hafnium in the polyinsertion of styrenes
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The hafnocene-based catalyst ethylenebis(1-indenyl)hafnium dichloride/methylalumoxane, as well as its zirconium analogue, is able to oligomerize styrene, p-methylstyrene, and p-tert-butylstyrene in the presence of hydrogen to produce hydrooligomers. The c
- Galdi, Nunzia,Izzo, Lorella,Oliva, Leone
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experimental part
p. 4434 - 4439
(2011/01/07)
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- Neutral flavins: Green and robust organocatalysts for aerobic hydrogenation of olefins
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"Chemical Equation Presented" Various olefins can be hydrogenated quantitatively with neutral flavin 2 catalysts in the presence of 1 -2 equiv of hydrazine under 1 atm of O2. Vitamin B2 derivative 2g acts as a highly efficient and robust catalyst for the present environmentally benign process producing water and nitrogen gas as the only waste products
- Imada, Yasushi,Kitagawa, Takahiro,Ohno, Takashi,Iida, Hiroki,Naota, Takeshi
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supporting information; experimental part
p. 32 - 35
(2010/03/04)
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- Discovery and characterization of the N-phenyl-N′-naphthylurea class of p38 kinase inhibitors
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An effort aimed at exploring structural diversity in the N-pyrazole-N′-naphthylurea class of p38 kinase inhibitors led to the synthesis and characterization of N-phenyl-N′-naphthylureas. Examples of these compounds displayed excellent inhibition of TNF-α production in vitro, as well as efficacy in a mouse model of lipopolysaccharide induced endotoxemia. In addition, perspective is provided on the role of a sulfonamide functionality in defining inhibitor potency.
- Cirillo, Pier F.,Hickey, Eugene R.,Moss, Neil,Breitfelder, Steffen,Betageri, Raj,Fadra, Tazmeen,Gaenzler, Faith,Gilmore, Thomas,Goldberg, Daniel R.,Kamhi, Victor,Kirrane, Thomas,Kroe, Rachel R.,Madwed, Jeffrey,Moriak, Monica,Netherton, Matthew,Pargellis, Christopher A.,Patel, Usha R.,Qian, Kevin C.,Sharma, Rajiv,Sun, Sanxing,Swinamer, Alan,Torcellini, Carol,Takahashi, Hidenori,Tsang, Michele,Xiong, Zhaoming
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scheme or table
p. 2386 - 2391
(2009/12/07)
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- A general and efficient suzuki-miyaura cross-coupling protocol using weak base and no water: The essential mole of acetate
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A weak base, CsOAc, promotes Suzuki-Miyaura cross-coupling and related Pd-catalyzed reactions under anhydrous conditions as effectively as stronger bases. Aryl triflates exhibit unusual reaction rates, which are comparable to that: of bromoarenes. A negle
- Wang, Bing,Sun, Hui-Xia,Sun, Zhi-Hua
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experimental part
p. 3688 - 3692
(2009/12/03)
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- Para-selective ethylation of t-butylbenzene with diethyl carbonate over mesoporous molecular sieves
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The vapour phase ethylation of t-butylbenzene (t-BB) with diethyl carbonate has been studied over mesoporous Al-MCM-41 (Si/Al = 50 and 90) and Al, Mg-MCM-41 [Si/(Al+Mg) = 50] from 200 to 400°C. The products are benzene, ethylbenzene (EB), p-diethylbenzene (p-DEB), p-t-butylethylbenzene (p-tBEB) and p-t-butylvinylbenzene (p-tBVB). t-Butylbenzene conversion increases with increase in temperature up to 300°C, but above this temperature it decreases. Ortho and meta-products are completely absent. Ethylbenzene is the product of ethylation of benzene and cracking of p-tBEB.The selectivity of para-t-butylated products is favoured at lower temperature while higher temperature favours ethylbenzene selectivity. The influence of time on stream is examined over Al-MCM-41 (50) and the results are discussed in this paper.
- Umamaheswari,Palanichamy,Arabindoo, Banumathi,Murugesan
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p. 259 - 265
(2007/10/03)
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- Perfluorooctanesulfonic acid catalyzed Friedel-Crafts alkylation with alkyl halides
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A new procedure to prepare superacid perfluorooctanesulfonic acid (POSA) is reported. POSA catalyzed Friedel-Crafts alkylation of aromatic compounds with alkyl halides in liquid-phase reactions. Alkylation gave higher total yields than the corresponding reactions with Nafion-H, without the need of any complex decomposition or work-up. The reactions do not need to be carried out under absolutely anhydrous condition. The catalyst POSA can be easily separated from the reaction mixture and reused or recovered. The reactivity of the alkylation reagents and the mechanism of the reaction are discussed.
- Fu,He,Lei,Luo
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p. 1273 - 1279
(2007/10/02)
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- Etude de l'alkylation du toluene en ethylbenzene et styrene. III. Etude de l'alkylation par le methylal et le methanol de derives benzeniques polysubstitues
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This work shows the possibility of side chain alkylation of polysubstituted aromatics (xylenes and p. tertiobutyltoluene) by methanol or methylal CH2(OCH3)2 on a Cs exchanged and doped 13X zeolite.The formed p. vinyltoluene and p. tertiobutylstyrene can be used in place of styrene in paints. The yield of alkylation decreased by passing from toluene to the xylenes of the p. tertiobutyltoluene.The difference of reactivity between the xylenes are discussed.As for the toluene, the results agree with the primordial role of the preparating method of the zeolite: washing or not after exchange, adding of promotors: boron and essentially copper.The role of hydrogen is confirmed.The mechanistic conclusion drawn from toluene alkylation can also be applied in the case of polysubstituted aromatics.
- Lacroix, C.,Deluzarche, A.,Kiennemann, A.,Boyer, A.
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p. 487 - 490
(2007/10/02)
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- Arene-Metal Complexes. 12. Reaction of Substituted (Benzene)tricarbonylchromium Complexes with n-Butyllithium
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Reaction of a series of substituted (benzene)tricarbonylchromium complexes with n-butyllithium has been examined.The reaction appears to proceed via proton abstraction to yield an (aryllithium)tricarbonylchromium intermediate which may then be quenched by the addition of primary alkyl halides,usually methyl iodide.New alkylated complexes may be obtained,or the material may be decomplexed to yield alkylated benzene derivatives.In this manner,(monoalkylbenzene)tricarbonylchromium complexes yield mainly m-dialkylbenzenes;(fluorobenzene)tricarbonylchromium yields o-fluorotoluene;(anisole)tricarbonylchromium yields mainly 2,6-dimethylanisole;and (N,N-dimethylaniline)tricarbonylchromium yields several isomeric N,N-dimethyltoluidines.(Iodobenzene)tricarbonylchromium undergoes metal-halogen exchange with n-butyllithium and may be converted to either toluene or n-butylbenzene depending on the reaction conditions.Comparison with known chemistry of the uncomplexed analogues demonstrates the strongly activating effect of the tricarbonylchromium moiety on these reactions.It is especially interesting that under these conditions reaction of (fluorobenzene)tricarbonylchromium with n-butyllithium results in proton abstraction rather than net nucleophilic displacement,as observed when less basic nucleophiles are used.
- Card, Roger J.,Trahanovsky, Walter S.
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p. 2560 - 2566
(2007/10/02)
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