- Hydration of Diethyl Maleate in the Presence of Bimetallic Hydroxy Palladium(II) Complexes of 1,2-Bis(diphenylphosphino)ethane(dppe) as Catalysts
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The hydration of diethyl maleate is catalysed by the presemce of 2(BF4)2 in solution.
- Ganguly, Sanjoy,Roundhill, D. Max
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- Catalysis of Olefin Isomerization by Tight Ion Pairs
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Tight ion pairs of 3-bromo-3-phenyldiazirine and triphenylmethyl bromide catalyze the isomerization of diethyl maleate to diethyl fumarate.
- Liu, Michael T. H.,Doyle, Michael P.,Loh, Kuo-Liang,Anand, Surinder M.
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- Thiyl radical induced isomerisations of maleate esters provide a convenient route to fumarates and furanones
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Maleate esters can be converted into fumarate esters in near quantitative yield through exposure to thiyl radicals generated in refluxing hexane by photolysis of diphenyl disulfide. When conditions are applied to dialkyl (hydroxyalkyl)maleate esters akin to 3, 2(5H)-furanones are given in good yield.
- Harrowven, David C.,Hannam, Joanne C.
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- Bottom-Up Synthesis of Acrylic and Styrylic RhII Carboxylate Polymer Beads: Solid-Supported Analogs of Rh2(OAc)4
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We have developed a short and efficient bottom-up synthesis of acrylic and styrylic polymer beads containing dirhodium(II) tetracarboxylates. The solid supported dirhodium(II) tetracarboxylate catalysts were synthesized in as little as two steps overall from dirhodium tetratrifluoroacetate and commercially available carboxylic acids, making the bottom-up approach a viable alternative to the post-modification approach commonly used. The dirhodium(II) tetracarboxylate polymer beads have a convenient size (ca. 100 μm), are easy to handle, and can be considered solid-supported analogs of Rh2(OAc)4. Beads generated from dirhodium(II) tetracarboxylates with four polymerizable carboxylate ligands displayed the best catalytic performance and compared favorably to Rh2(OAc)4 in benchmarked cyclopropanation reactions. The results imply that the cumbersome synthesis of monomeric dirhodium(II) tetracarboxylates with mixed ligands systems can be avoided and that immobilized dirhodium(II)-catalysts with a higher degree of crosslinking is a viable option to catalysts linked in an anchor-like fashion. We demonstrate recovery and recycling, and a potential use of the beads as catalysts in a cyclopropanation reaction towards the insecticide chrysanthemic acid.
- Levchenko, Vladimir,Sundsli, B?rd,?ien-?degaard, Sigurd,Tilset, Mats,Hansen, Finn K.,Bonge-Hansen, Tore
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- Synthesis of 17-epi-calcitriol from a common androstane derivative, involving the ring B photochemical opening and the intermediate triene ozonolysis
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An efficient synthesis of 17-epi-calcitriol 2, an epimer of natural hormone, via 17-epi-cholesterol 5a is described. Synthesis of 5a includes palladium-catalyzed cyclopropanation of the common androstane derivative 7 with an alkyl diazoacetate, reductive fission of the less shielded side of cyclopropane carboxylic acid esters 6, oxidation of the products into acid 11a, and alkylation of ester 11b. Photolysis of 7,8-dedydro-17-epi-25- hydroxycholesterol 19b and consecutive thermal rearrangement gave a mixture of several products that was subjected to ozonolysis to provide, after chromatography, hydroxy ketone 3a. The silyl derivative 3b was coupled with the respective ring A building block.
- Kurek-Tyrlik, Alicja,Michalak, Karol,Wicha, Jerzy
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- Zwitterion-Catalyzed Isomerization of Maleic to Fumaric Acid Diesters
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Fumaric acid diesters are important building blocks for organic synthesis. A class of zwitterionic organocatalysts based on an amide anion/iminium cation charge pair were found to be effective in catalyzing the isomerization of maleic acid diesters to give fumaric acid diesters. Comparison of the performance of different zwitterionic organocatalysts toward the reaction revealed that nonclassical hydrogen bonding was involved in the stabilization of the Michael adduct intermediate.
- Lam, Ying-Pong,Lam, Zachary,Yeung, Ying-Yeung
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p. 1183 - 1190
(2021/01/09)
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- Synthesis, structure and reactivity of iridium complexes containing a bis-cyclometalated tridentate C^N^C ligand
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In an effort to synthesize cyclometalated iridium complexes containing a tridentate C^N^C ligand, transmetallation of [Hg(HC^N^C)Cl] (1) (H2C^N^C = 2,6-bis(4-tert-butylphenyl)pyridine) with various organoiridium starting materials has been studied. The treatment of1with [Ir(cod)Cl]2(cod = 1,5-cyclooctadiene) in acetonitrile at room temperature afforded a hexanuclear Ir4Hg2complex, [Cl(κ2C,N-HC^N^C)(cod)IrHgIr(cod)Cl2]2(2), which features Ir-Hg-Ir and Ir-Cl-Ir bridges. Refluxing2with sodium acetate in tetrahydrofuran (thf) resulted in cyclometalation of the bidentate HC^N^C ligand and formation of trinuclear [(C^N^C)(cod)IrHgIr(cod)Cl2] (3). On the other hand, refluxing [Ir(cod)Cl]2with1and sodium acetate in thf yielded [Ir(C^N^C)(cod)(HgCl)] (4). Chlorination of4with PhICl2gave [Ir(C^N^C)(cod)Cl]·HgCl2(5·HgCl2) that reacted with tricyclohexylphosphine to yield Hg-free [Ir(C^N^C)(cod)Cl] (5). Chloride abstraction of5with silver(i) triflate (AgOTf) gave [Ir(C^N^C)(cod)(H2O)](OTf) (6) that can catalyze the cyclopropanation of styrene with ethyl diazoacetate. Reaction of1and [Ir(CO)2Cl(py)] (py = pyridine) with sodium acetate in refluxing thf afforded [Ir(C^N^C)(HgCl)(py)(CO)] (7), in which the carbonyl ligand is coplanar with the C^N^C ligand. On the other hand, refluxing1with (PPh4)[Ir(CO)2Cl2] and sodium acetate in acetonitrile gave [Ir(C^N^C)(κ2C,N-HC^N^C)(CO)] (8), the carbonyl ligand of which istransto the pyridyl ring of the bidentate HC^N^C ligand. Upon irradiation with UV light8in thf was isomerized to8′, in which the carbonyl istransto a phenyl group of the bidentate HC^N^C ligand. The isomer pair8and8′exhibited emission at 548 and 514 nm in EtOH/MeOH at 77 K with lifetime of 84.0 and 64.6 μs, respectively. Protonation of8withp-toluenesulfonic acid (TsOH) afforded the bis(bidentate) tosylate complex [Ir(κ2C,N-HC^N^C)2(CO)(OTs)] (9) that could be reconverted to8upon treatment with sodium acetate. The electrochemistry of the Ir(C^N^C) complexes has been studied using cyclic voltammetry. Reaction of [Ir(PPh3)3Cl] with1and sodium acetate in refluxing thf led to isolation of the previously reported compound [Ir(κ2P,C-C6H4PPh2)2(PPh3)Cl] (10). The crystal structures of2-5,8,8′,9and10have been determined.
- Cheng, Shun-Cheung,Cheung, Wai-Man,Chong, Man-Chun,Ko, Chi-Chiu,Leung, Wa-Hung,Sung, Herman H.-Y.,Williams, Ian D.
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p. 8512 - 8523
(2021/06/28)
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- One-pot production of diethyl maleate via catalytic conversion of raw lignocellulosic biomass
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The conversion of lignocellulose into a value-added chemical with high selectivity is of great significance but is a big challenge due to the structural diversities of biomass components. Here, we have reported an efficient approach for the one-step conversion of raw lignocellulose into diethyl maleate by the polyoxometalate ionic liquid [BSmim]CuPW12O40 in ethanol under mild conditions. The results reveal that all of the fractions in biomass, i.e., cellulose, lignin and hemicellulose, were simultaneously converted into diethyl maleate (DEM), achieving a 329.6 mg g-1 yield and 70.3% selectivity from corn stalk. Importantly, the performance of the ionic liquid catalyst [BSmim]CuPW12O40 was nearly twice that of CuHPW12O40, which can be attributed to the lower incorporation of the Cu2+ site in [BSmim]CuPW12O40. Hence, this process opens a promising route for producing bio-based bulk chemicals from raw lignocellulose without any pretreatment.
- Cai, Zhenping,Chen, Rujia,Jiang, Lilong,Li, Fukun,Li, Xuehui,Long, Jinxing,Zhang, Hao
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supporting information
p. 10116 - 10122
(2021/12/24)
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- Mechanochemical defect engineering of HKUST-1 and impact of the resulting defects on carbon dioxide sorption and catalytic cyclopropanation
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Metal-organic frameworks (MOFs) are recognized as ideal candidates for many applications such as gas sorption and catalysis. For a long time the properties of these materials were thought to essentially arise from their well-defined crystal structures. It is only recently that the importance of structural defects for the properties of MOFs has been evidenced. In this work, salt-assisted and liquid-assisted grinding were used to introduce defects in a copper-based MOF, namely HKUST-1. Different milling times and post-synthetic treatments with alcohols allow introduction of defects in the form of free carboxylic acid groups or reduced copper(i) sites. The nature and the amount of defects were evaluated by spectroscopic methods (FTIR, XPS) as well as TGA and NH3temperature-programmed desorption experiments. The negative impact of free -COOH groups on the catalytic cyclopropanation reaction of ethyl diazoacetate with styrene, as well as on the gravimetric CO2sorption capacities of the materials, was demonstrated. The improvement of the catalytic activity of carboxylic acid containing materials by the presence of CuIsites was also evidenced.
- Barozzino-Consiglio, Gabriella,Filinchuk, Yaroslav,Grégoire, Nicolas,Hermans, Sophie,Steenhaut, Timothy
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p. 19822 - 19831
(2020/06/03)
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- Iron/N-doped graphene nano-structured catalysts for general cyclopropanation of olefins
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The first examples of heterogeneous Fe-catalysed cyclopropanation reactions are presented. Pyrolysis of in situ-generated iron/phenanthroline complexes in the presence of a carbonaceous material leads to specific supported nanosized iron particles, which are effective catalysts for carbene transfer reactions. Using olefins as substrates, cyclopropanes are obtained in high yields and moderate diastereoselectivities. The developed protocol is scalable and the activity of the recycled catalyst after deactivation can be effectively restored using an oxidative reactivation protocol under mild conditions. This journal is
- Bartling, Stephan,Beller, Matthias,Ferretti, Francesco,Formenti, Dario,Junge, Kathrin,Kreyenschulte, Carsten,Ragaini, Fabio,Sarkar, Abhijnan
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p. 6217 - 6221
(2020/08/24)
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- CATALYZED AND GREEN PROCESS OF MALATHION
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The present invention relates to an improved synthesis of malathion. The presence of an acid facilitates the reaction between O,O-dimethyldithiophosphoric acid (O,O-DMDTPA) and maleate and leads to excellent product yield in shorter reaction time with fewer impurities.
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Paragraph 0030-0032
(2020/05/12)
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- Deoxygenation of Epoxides with Carbon Monoxide
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The use of carbon monoxide as a direct reducing agent for the deoxygenation of terminal and internal epoxides to the respective olefins is presented. This reaction is homogeneously catalyzed by a carbonyl pincer-iridium(I) complex in combination with a Lewis acid co-catalyst to achieve a pre-activation of the epoxide substrate, as well as the elimination of CO2 from a γ-2-iridabutyrolactone intermediate. Especially terminal alkyl epoxides react smoothly and without significant isomerization to the internal olefins under CO atmosphere in benzene or toluene at 80–120 °C. Detailed investigations reveal a substrate-dependent change in the mechanism for the epoxide C?O bond activation between an oxidative addition under retention of the configuration and an SN2 reaction that leads to an inversion of the configuration.
- Maulbetsch, Theo,Jürgens, Eva,Kunz, Doris
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p. 10634 - 10640
(2020/07/30)
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- New N-methylimidazolium hexachloroantimonate: Synthesis, crystal structure, Hirshfeld surface and catalytic activity of in cyclopropanation of stryrene
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The N-methylimidazolium hexachloroantimonate salt Cl6Sb·C4H7N2 (MIMSb), was prepared and fully characterized. In 1H NMR spectrum, the N-H proton shifted to downfield because of the presence of SbCl6? and appears as a triplet at 13.19 ppm. Characterization with IR spectroscopy shows strong absorption band at around 699 cm?1 which is attributed to Sb?Cl stretching. Furthermore, UV–visible analysis at high concentrations in DMSO suggested that MIMSb interacts with DMSO leading to an absorption in visible region at λmax of 426 nm. Electrochemical characterization using cyclic voltammetry demonstrates three redox processes with reduction peaks at 0.69, ?0.13 and ?0.50 V. Finally, molecular structure of the product was determined by X-ray diffraction analysis. The crystal structure determination was carried out with Mo-Kα X-ray and data measured at 100 K. The title compound crystallizes in monoclinic P21/c space group with unit cell parameters a = 7.1131 (5) ?, b = 12.4436 (9) ?, c = 14.1658 (11) ?, V = 1241.86 (16) ?3 and Z = 4. The crystal packing is stabilized by H—Cl interaction. The analysis of intermolecular interactions was realized through the mapping of contact descriptors dnorm, shape-index and the fingerprint reveling that the most significant contribution to the Hirshfeld surface (69.4%) is from H—Cl contacts. Finally, the catalytic activity of MIMSb was probed in the cyclopropanation of styrene with ethyl diazoacetate.
- Boschini, Frédéric,Mahmoud, Abdelfattah,Sénam Etsè, Koffi,Zaragoza, Guillermo
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- Thermal defect engineering of precious group metal-organic frameworks: Impact on the catalytic cyclopropanation reaction
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We report on the engineering of defects in precious group metal (PGM)-based HKUST-1 (Hong Kong University of Science and Technology) analogues (RhII,II, RuII,II, RuII,III) and the ramification on the catalytic activity by using the cyclopropanation of styrene with ethyl diazoacetate (EDA) as an analytical probe to investigate complex metal-organic framework (MOF) structures. We have characterized the active sites within the extended frameworks by their activity, product distribution and stereoselectivity. The role of the metal, its oxidation state and the availability of open metal sites is elucidated. With a set of 17 samples including reference to Cu-HKUST-1, metal nanoparticles and existing literature, conclusions on the tuneability of paddlewheel complexes within self-supported porous and crystalline frameworks are presented. In particular, additional axial ligands (OAc-/Cl-) accounting for charge compensation at the mixed-valent RuII,III nodes seem responsible for side-product formation during catalysis. Thermal defect-engineering allows for controlled and preferential removal of those axial ligands accompanied by reduction of the average metal oxidation state. This enhances the number of open metal sites (OMS) and the catalytic activity as well as improving the chemoselectivity towards cyclopropanes. The preference towards formation of trans-cyclopropane is assigned to the steric crowding of the paddlewheel moiety. This diastereoselectivity gradually diminishes with rising defectiveness of the PGM-HKUST-1 analogues featuring modified paddlewheel nodes.
- Heinz, Werner R.,Junk, Raphael,Agirrezabal-Telleria, Iker,Bueken, Bart,Bunzen, Hana,G?lz, Thorsten,Cokoja, Mirza,De Vos, Dirk,Fischer, Roland A.
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p. 8077 - 8085
(2020/12/31)
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- Deoxydehydration using a commercial catalyst and readily available reductant
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We have explored the use of a commercially available molybdenum compound, ammonium heptamolybdate (AHM) in catalyzing the deoxydehydration (DODH) reaction using sodium sulfite (Na2SO3) as reductant. The catalytic reactions were effected at relatively lower temperatures (170–190 °C) yielding the alkenes in moderate yields.
- Navarro, Christine A.,John, Alex
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p. 145 - 148
(2018/11/27)
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- Re-catalyzed deoxydehydration of polyols to olefins using indoline reductants
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A rhenium (CH3ReO3, MTO) catalyzed deoxydehyradration (DODH) of glycols to alkenes has been achieved using hydroaromatic compounds as H-transfer reductants. Of the hydroaromatics examined, indoline was the most efficient and proved to be better potential hydrogen donor. The yield of the products is moderate to excellent and the reaction is very clean with the only indole, the oxidized byproduct of indoline detected.[Figure presented]
- Jefferson, Alana,Srivastava, Radhey S.
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p. 268 - 271
(2019/01/23)
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- Gold-catalyzed ethylene cyclopropanation
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Ethylene can be directly converted into ethyl 1-cyclopropylcarboxylate upon reaction with ethyl diazoacetate (N2CHCO2Et, EDA) in the presence of catalytic amounts of IPrAuCl/NaBArF4 (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene; BArF4 = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate).
- Rull, Silvia G.,Olmos, Andrea,Pérez, Pedro J.
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- Generation and Reactivity of Electron-Rich Carbenes on the Surface of Catalytic Gold Nanoparticles
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The reactive nature of carbenes can be modulated, and ultimately reversed, by receiving additional electron density from a metal. Here, it is shown that Au nanoparticles (NPs) generate an electron-rich carbene on surface after transferring electron density to the carbonyl group of an in situ activated diazoacetate, as assessed by Fourier transformed infrared (FT-IR) spectroscopy, magic angle spinning nuclear magnetic resonance (MAS NMR), and Raman spectroscopy. Density functional theory (DFT) calculations support the observed experimental values and unveil the participation of at least three different Au atoms during carbene stabilization. The surface stabilized carbene shows an extraordinary stability against nucleophiles and reacts with electrophiles to give new products. These findings showcase the ability of catalytic Au NPs to inject electron density in energetically high but symmetrically allowed valence orbitals of sluggish molecules.
- Oliver-Meseguer, Judit,Boronat, Mercedes,Vidal-Moya, Alejandro,Concepción, Patricia,Rivero-Crespo, Miguel ángel,Leyva-Pérez, Antonio,Corma, Avelino
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supporting information
p. 3215 - 3218
(2018/03/13)
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- MODULATOR OF CYSTIC FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR, PHARMACEUTICAL COMPOSITIONS, METHODS OF TREATMENT, AND PROCESS FOR MAKING THE MODULATOR
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Compounds of Formula (I) pharmaceutically acceptable salts thereof, deuterated derivatives of any of the foregoing, and metabolites of any of the foregoing are disclosed. Pharmaceutical compositions comprising the same, methods of treating cystic fibrosis using the same, and methods for making the same are also disclosed. Also disclosed are solid state forms of Compound 1 and salts and solvates thereof.
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Page/Page column 285; 287; 288
(2018/06/30)
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- Confinement of Fe-Al-PMOF catalytic sites favours the formation of pyrazoline from ethyl diazoacetate with an unusual sharp increase of selectivity upon recycling
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The catalytic properties of a chemically stable iron porphyrin MOF were evaluated in a reaction with ethyl diazoacetate. In contrast to its homogeneous counterpart, an Fe-porphyrin-MOF features a different reaction pathway leading to the formation of pyrazoline due to the confinement of catalytic sites within the MOF network. Unexpectedly, a sharp increase of the selectivity from 35% (run 1) to 86% (run 5) occurs upon catalyst recycling.
- Abeykoon, Brian,Devic, Thomas,Grenèche, Jean-Marc,Fateeva, Alexandra,Sorokin, Alexander B.
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supporting information
p. 10308 - 10311
(2018/09/21)
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- Synthesis, characterization, and catalytic evaluation of ruthenium-diphosphine complexes bearing xanthate ligands
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The reaction of [RuCl2(p-cymene)]2 with potassium O-ethylxanthate and a set of nine representative Ph2P-X-PPh2 bidentate phosphines (dppm, dppe, dppp, dppb, dpppe, dppen, dppbz, dppf, and DPEphos) afforded monometallic [Ru(S2COEt)2(diphos)] chelates 1-9 in 62-96% yield. All the products were fully characterized by using various analytical techniques and their molecular structures were determined by X-ray crystallography. They featured a highly distorted octahedral geometry with a S-Ru-S bite angle close to 72° and P-Ru-P angles ranging between 73° and 103°. Bond lengths and IR stretching frequencies recorded for the anionic xanthate ligands strongly suggested a significant contribution of the EtO+CS22- resonance form. 1H NMR and XRD analyses showed that the methylene protons of the ethyl groups were diastereotopic due to a strong locking of their conformation by a neighboring phenyl ring. On cyclic voltammetry, quasi-reversible waves were observed for the Ru2+/Ru3+ redox couples with E1/2 values ranging between 0.65 and 0.80 V vs. Ag/AgCl. The activity of chelates 1-9 was probed in three catalytic processes, viz., the synthesis of vinyl esters from benzoic acid and 1-hexyne, the cyclopropanation of styrene with ethyl diazoacetate, and the atom transfer radical addition of carbon tetrachloride and methyl methacrylate. In the first case, 31P NMR analysis of the reaction mixtures showed that the starting complexes remained mostly unaltered despite the harsh thermal treatment that was applied to them. In the second case, monitoring the rate of nitrogen evolution revealed that all the catalysts under investigation behaved similarly and were rather slow initiators. In the third case, [Ru(S2COEt)2(dppm)] was singled out as a very active and selective catalyst already at 140 °C, whereas most of the other complexes resisted degradation up to 160 °C and were only moderately active. Altogether, these results were in line with the high stability displayed by [Ru(S2COEt)2(diphos)] chelates 1-9.
- Zain Aldin, Mohammed,Maho, Anthony,Zaragoza, Guillermo,Demonceau, Albert,Delaude, Lionel
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p. 13926 - 13938
(2018/10/20)
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- Method of selectively catalytically oxidizing biomass-based furan compound
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The invention discloses a method of selectively catalytically oxidizing a biomass-based furan compound. The method comprises the following step of: by taking a heteropolyacid functional ionic liquid as a catalyst and an alcohol solution as a reaction medium, obtaining dicarboxylic acid or dicarboxylate in the conditions that the reaction temperature is 100-150 DEG C, the reaction time is 1-3h and the oxygen pressure is 0.5-1.0MPa, wherein over 62.35% of difumarate selectivity is obtained. The single chemical yield and selectivity for oxidizing preparation of a biomass-based furan derivative are far higher than those of the prior art. The method has the remarkable advantage that an ionic liquid catalyst can be recovered and recycled by simply adjusting the temperature. The method disclosed by the invention is mild in reaction condition, green and safe in process and simple to operate, and can realize intermittent and continuous production.
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Paragraph 0098-0101
(2017/07/19)
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- Rhenium-catalyzed deoxydehydration of renewable biomass using sacrificial alcohol as reductant
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Catalytic deoxydehydration (DODH) of vicinal diols is studied. We find that NH4ReO4 (ammonium perrhenate, APR) catalyzes the DODH of glycols to alkenes by sacrificial alcohol (2,4-dimethyl-3-pentanol) at 140–165 °C. The product yields range from good to excellent and no isomers detected. The catalytic DODH reaction of glycols to alkene is of potential value for the production of chemicals and fuels from the renewable biomass-derived polyols.[Figure presented]
- Gossett, Justin,Srivastava, Radhey
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p. 3760 - 3763
(2017/09/09)
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- Unexpected formation of a μ-carbido diruthenium(IV) complex during the metalation of phthalocyanine with Ru3(CO)12 and its catalytic actIVity in carbene transfer reactions
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A μ-carbido diruthenium(iv) phthalocyanine complex was prepared for the first time from the free-base octabutoxyphthalocyanine by direct metalation with Ru3(CO)12. The first examples of the catalytic activity of Ru(iv) binuclear phthalocyanines were demonstrated by the cyclopropanation of aromatic olefins and carbene insertion into the N-H bonds of aromatic or aliphatic amines with turnover numbers of 680-1000 and 580-1000, respectively.
- Kroitor, Andrey P.,Cailler, Lucie P.,Martynov, Alexander G.,Gorbunova, Yulia G.,Tsivadze, Aslan Yu.,Sorokin, Alexander B.
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supporting information
p. 15651 - 15655
(2017/12/02)
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- Gold-Ligand-Catalyzed Selective Hydrogenation of Alkynes into cis-Alkenes via H2 Heterolytic Activation by Frustrated Lewis Pairs
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The selective hydrogenation of alkynes to alkenes is an important synthetic process in the chemical industry. It is commonly accomplished using palladium catalysts that contain surface modifiers, such as lead and silver. Here we report that the adsorption of nitrogen-containing bases on gold nanoparticles results in a frustrated Lewis pair interface that activates H2 heterolytically, allowing an unexpectedly high hydrogenation activity. The so-formed tight-ion pair can be selectively transferred to an alkyne, leading to a cis isomer; this behavior is controlled by electrostatic interactions. Activity correlates with H2 dissociation energy, which depends on the basicity of the ligand and its reorganization on activation of hydrogen. High surface occupation and strong Au atom-ligand interactions might affect the accessibility and stability of the active site, making the activity prediction a multiparameter function. The promotional effect found for nitrogen-containing bases with two heteroatoms was mechanistically described as a strategy to boost gold activity. (Graph Presented).
- Fiorio, Jhonatan L.,López, Núria,Rossi, Liane M.
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p. 2973 - 2980
(2017/05/31)
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- Sustainable production of pyromellitic acid with pinacol and diethyl maleate
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Herein, we report an unprecedented and sustainable route to synthesize pyromellitic acid (PMA), a monomer of polyimide, with pinacol and diethyl maleate which can be derived from lignocellulose. Analogously, a sustainable route to trimellitic acid (TMA) was also developed using pinacol and acrylate as the feedstocks.
- Hu, Yancheng,Li, Ning,Li, Guangyi,Wang, Aiqin,Cong, Yu,Wang, Xiaodong,Zhang, Tao
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supporting information
p. 1663 - 1667
(2017/06/05)
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- Enantiopure Chiral Concave 1,10-Phenanthrolines
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Chiral information has been introduced into concave 1,10-phenanthrolines of different ring sizes by using a 2,7-disubstituted naphthalene bridgehead, which causes axial chirality. A tetraphenolic 2-(dihydroxynaphthyl)-9-(dihydroxyphenyl)-1,10-phenanthroline was synthesized as a key intermediate. Two strategies were followed to obtain the bimacrocyclic chiral concave 1,10-phenanthrolines: quadruple Williamson ether synthesis or alkenylation of the OH groups and subsequent ring-closing metathesis followed by hydrogenation. The overall yields of bimacrocyles 19 were 10 to 17 % starting from the respective Suzuki coupling of the substituted arenes 11 and 13 to 2,9-dichloro-1,10-phenanthroline (5). Racemic mixtures of the three concave 1,10-phenanthrolines 19 were separated by using chiral high-performance liquid chromatography (HPLC) techniques, and their absolute stereochemistry was assigned by comparison of simulated and experimental circular dichroism (CD) spectra. The enantiopure concave 1,10-phenanthrolines were used as ligands in a copper-catalysed cyclopropanation, and their selectivity was determined by chiral gas chromatography (GC).
- Reck, Lisa M.,Haberhauer, Gebhard,Lüning, Ulrich
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p. 1119 - 1131
(2016/03/05)
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- Synthesis and catalytic applications of 1,2,3-triazolylidene gold(i) complexes in silver-free oxazoline syntheses and C-H bond activation
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A series of novel 1,2,3-triazolylidene gold(i) chloride complexes have been synthesised and fully characterised. Silver-free methodologies for chloride ion abstraction of these complexes were evaluated for their potential as Au-based catalyst precursors. Using simple potassium salts or MeOTf as chloride scavengers produced metal complexes that catalyse both the regioselective synthesis of oxazolines and the C-H activation of benzene or styrene for carbene transfer from ethyl diazoacetate. These results indicate that Ag-free activation of 1,2,3-triazolylidene gold(i) chloride complexes is feasible for the generation of catalytically active Au triazolylidene species. However, silver-mediated activation imparts substantially higher catalytic activity in oxazoline synthesis.
- Pretorius, René,Fructos, Manuel R.,Müller-Bunz, Helge,Gossage, Robert A.,Pérez, Pedro J.,Albrecht, Martin
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p. 14591 - 14602
(2016/09/28)
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- Myoglobin-catalyzed olefination of aldehydes
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The olefination of aldehydes constitutes a most valuable and widely adopted strategy for constructing carbon-carbon double bonds in organic chemistry. While various synthetic methods have been made available for this purpose, no biocatalysts are known to mediate this transformation. Reported herein is that engineered myoglobin variants can catalyze the olefination of aldehydes in the presence of α-diazoesters with high catalytic efficiency (up to 4,900 turnovers) and excellent Ediastereoselectivity (92-99.9 % de). This transformation could be applied to the olefination of a variety of substituted benzaldehydes and heteroaromatic aldehydes, also in combination with different alkyl α-diazoacetate reagents. This work provides a first example of biocatalytic aldehyde olefination and extends the spectrum of synthetically valuable chemical transformations accessible using metalloprotein-based catalysts.
- Tyagi, Vikas,Fasan, Rudi
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supporting information
p. 2512 - 2516
(2016/02/18)
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- Carbon Monoxide (CO)- and Hydrogen-Driven, Vanadium-Catalyzed Deoxydehydration of Glycols
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Four oxo-vanadium complexes of the type Z+LVO2- (1-4) have been evaluated for activity as catalysts for the deoxydehydration (DODH) of glycols to olefins with various reductants. Among these, a new complex, [Bu4N](Salhyd)VO2 (4), is found to be uniquely effective for the DODH reaction using the practical reductants: hydrogen and carbon monoxide (CO).
- Gopaladasu, Tirupathi V.,Nicholas, Kenneth M.
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p. 1901 - 1904
(2016/03/15)
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- Design of Core-Pd/Shell-Ag Nanocomposite Catalyst for Selective Semihydrogenation of Alkynes
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We designed core-Pd/shell-Ag nanocomposite catalyst (Pd@Ag) for highly selective semihydrogenation of alkynes. The construction of the core-shell nanocomposite enables a significant improvement in the low activity of Ag NPs for the selective semihydrogenation of alkynes because hydrogen is supplied from the core-Pd NPs to the shell-Ag NPs in a synergistic manner. Simultaneously, coating the core-Pd NPs with shell-Ag NPs results in efficient suppression of overhydrogenation of alkenes by the Pd NPs. This complementary action of core-Pd and shell-Ag provides high chemoselectivity toward a wide range of alkenes with high Z-selectivity under mild reaction conditions (room temperature and 1 atm H2). Moreover, Pd@Ag can be easily separated from the reaction mixture and is reusable without loss of catalytic activity or selectivity.
- Mitsudome, Takato,Urayama, Teppei,Yamazaki, Kenji,Maehara, Yosuke,Yamasaki, Jun,Gohara, Kazutoshi,Maeno, Zen,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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supporting information
p. 666 - 670
(2016/02/18)
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- Stereoselective cyclopropanation under solvent free conditions: Catalyzed by a green and efficient recyclable Cu-exchanged bentonite
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Background: The cyclopropanation reaction was inspected by addition of carbene generated from ethyl diazoacetate in the presence of a greener Cu-exchanged bentonite catalyst to olefin under solvent free condition. The cyclopropanes were obtained with good yields. Our own contribution in this area was to introduce a modified Algerian bentonite as a catalyst and microwave activation as a mode of heating. Methods: A catalytic material developed from natural type montmorillonite clays, from deposits of Maghnia (Western Algeria), by cation exchange (Cu2+) was characterized by different spectral methods. The catalytic properties of the new material were explored in cyclopropanation reaction of olefins under microwave irradiation. A comparative study with Cu-exchanged bentonite as catalyst between microwave activation and classical heating was conducted. Results: Cu2+ exchanged clay is an efficient catalyst in the generation of carbenes from diazocompounds, under microwave irradiation. The formation of carboxylate cyclopropane was performed in solvent free condition with moderate diastereoselectivity. The yields were good, and the catalyst can be reused at least three times without noticeable loss of catalytic activity. Conclusion: This work shows that the coupling "modified clay/microwave activation" is a clean and simple access to functionalized cyclopropanes. This reusable Cu exchanged clay material is shown to be as a good substitute for many sophisticated and hardly accessible catalysts.
- Bendeddouche, Choukry K.,Adjdir, Mehdi,Benhaoua, Hadj
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p. 217 - 223
(2016/03/01)
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- Parent-amido (NH2) palladium(II) complexes: Synthesis, reactions, and catalytic hydroamination
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The treatment of [PdL3(NH3)](OTf)n (n = 1; L3 = (PEt3)2(Ph), (2,6-(Cy2PCH2)2C6H3), n = 2; L3 = (dppe)(NH3)) with NaNH2 in tetrahydrofuran at ambient temperature or -78 °C afforded the dimeric and monomeric parent-amido palladium(II) complexes anti-[Pd(PEt3)(Ph)(μ-NH2)]2 (1), [Pd(dppe)(μ-NH2)]2(OTf)2 (2), and Pd(2,6-(Cy2PCH2)2C6H3)(NH2) (3), respectively. The molecular structures of the amido-bridged (μ-NH2) dimeric complexes 1 and 2 were determined by single-crystal X-ray crystallography. The monomeric amido complex 3 reacted with trace amounts of water to give a hydroxo complex, Pd(2,6-(Cy2PCH2)2C6H3)(OH) (4). Exposing complex 3 to an excess of water resulted in the complete conversion of the complex into two species [Pd(2,6-(Cy2PCH2)2C6H3)(OH2)]+ and [Pd(2,6-(Cy2PCH2)2C6H3)(NH3)]+. Complex 3 reacted with diphenyliodonium triflate ([Ph2I]OTf) to give the aniline complex [Pd(2,6-(Cy2PCH2)2C6H3)(NH2Ph)]OTf. The reaction of 3 with phenylacetylene (HCCPh) yielded a palladium(II) acetylenide Pd(2,6-(Cy2PCH2)2C6H3)(CCPh) (5), quantitatively, along with the liberation of ammonia. The reaction of 3 with dialkyl acetylenedicarboxylate yielded diastereospecific palladium(II) vinyl derivatives (Z)-Pd(2,6-(Cy2PCH2)2C6H3)(CRCR(NH2)) (R = CO2Me (6a), CO2Et (6b)). The reaction of complexes 6a and 6b with p-nitrophenol produced Pd(2,6-(Cy2PCH2)2C6H3)(OC6H4-p-NO2) (7) and cis-CHRCR(NH2), exclusively. Reactions of 3 with either dialkyl maleate (cis-(CO2R)CHCH(CO2R)) (R = CH3, CH2CH3) or cis-stilbene (cis-CHPhCHPh) did not result in any addition product. Instead, isomerization of the cis-isomers to the trans-isomers occurred in the presence of catalytic amounts of 3. Complex 3 reacted with a stoichiometric amount of acrylonitrile (CH2CHCN) to generate a metastable insertion product, Pd(2,6-(Cy2PCH2)2C6H3)(CH(CN)CH2NH2). On the other hand, the reaction of 3 with an excess of acrylonitrile slowly produced polymeric species of acrylonitrile. The catalytic hydroamination of olefins with NH3 was examined in the presence of Pd(2,6-(Cy2PCH2)2C6H3)(OTf), producing a range of hydroaminated products of primary, secondary, and tertiary amines with different molar ratios of more than 99% overall yield. A mechanistic feature for the observed catalytic hydroamination is described with regard to the aminated derivatives of palladium(II).
- Kim, Youngwon,Park, Soonheum
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p. 614 - 629
(2016/06/01)
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- Acrylates via Metathesis of Crotonates
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Crotonic acid has the potential to be produced from renewable resources at low cost but currently has a limited market. We are investigating catalytic routes to exploit the functionalities of crotonic acid to produce a range of established industrial chemicals. Here we report our work on converting crotonates to acrylates, where a cost-competitive bio-based alternative can provide a market advantage. Our optimized reaction conditions for the cross-metathesis between crotonates and ethylene resulted in an increase in catalyst turnover numbers by 2 orders of magnitude compared with literature values. Control experiments showed the cross-metathesis with ethylene to be an equilibrium reaction. The turnover-number-limiting factor was found to be the stability of the metathesis catalyst.
- Schweitzer, Dirk,Snell, Kristi D.
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supporting information
p. 715 - 720
(2015/07/27)
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- Assessment of catalysis by arene-ruthenium complexes containing phosphane or NHC groups bearing pendant conjugated diene systems
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Two p-cymene-ruthenium complexes 1 and 2 were isolated in high yields by treating the [RuCl2(p-cymene)]2 dimer with new hybrid phosphane- or NHC-linked diene ligands. Both complexes were fully characterized by NMR spectroscopy, and the molecular structure of the ruthenium-p-cymene complex 1, containing the phosphane-diene ligand system, was determined by X-ray diffraction analysis. The catalytic activities of both compounds were probed in atom-transfer radical addition (ATRA) and polymerization (ATRP), in the cyclopropanation of olefins, in the ring-opening metathesis polymerization (ROMP) of norbornene, and in the synthesis of enol esters from hex-1-yne and 4-acetoxybenzoic acid.
- Baraut, Johann,Massard, Alexandre,Chotard, Florian,Bodio, Ewen,Picquet, Michel,Richard, Philippe,Borguet, Yannick,Nicks, Fran?ois,Demonceau, Albert,Le Gendre, Pierre
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supporting information
p. 2671 - 2682
(2015/06/22)
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- Copper-Carbene Intermediates in the Copper-Catalyzed Functionalization of O-H Bonds
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Copper-carbene [TpxCu=C(Ph)(CO2Et)] and copper-diazo adducts [TpxCu{η1-N2C(Ph)(CO2Et)}] have been detected and characterized in the context of the catalytic functionalization of O-H bonds through carbene insertion by using N2=C(Ph)(CO2Et) as the carbene source. These are the first examples of these type of complexes in which the copper center bears a tridentate ligand and displays a tetrahedral geometry. The relevance of these complexes in the catalytic cycle has been assessed by NMR spectroscopy, and kinetic studies have demonstrated that the N-bound diazo adduct is a dormant species and is not en route to the formation of the copper-carbene intermediate.
- Pereira, Ana,Champouret, Yohan,Martín, Carmen,álvarez, Eleuterio,Etienne, Michel,Belderraín, Tomás R.,Pérez, Pedro J.
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supporting information
p. 9769 - 9775
(2015/06/30)
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- Carbenoid transfer in competing reactions catalyzed by ruthenium complexes
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Aiming at improving catalyst activity, ten ruthenium promoters have been investigated in carbenoid transfer from ethyl diazoacetate to styrene as a model substrate. Optimal selectivity in cyclopropanation has been attained with the new NHC-Ru complex 10, as well as with the Fischer carbene 7. The surprising non-metathetical behavior of the Grubbs' first-generation catalyst in this multifaceted process is highlighted. Copyright
- Dragutan, Ileana,Dragutan, Valerian,Verpoort, Francis
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p. 211 - 215
(2014/03/21)
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- A monomer-dimer nanoswitch that mimics the working principle of the SARS-CoV 3CLpro enzyme controls copper-catalysed cyclopropanation
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A triangular framework with a terpyridine and shielded phenanthroline at its termini constitutes an open/close nanoswitch that is toggled by chemical inputs. In the presence of copper(i) ions, the open triangular framework (OPEN-I) firmly closes to a catalytically inactive heteroleptic [Cu(phen)(terpy)]+ complex (CLOSE). Reversible switching between CLOSE and OPEN-I states was demonstrated by successive addition and removal of Cu+. In contrast, after addition of iron(ii) ions to the CLOSE state a bishomoleptic dimeric [Fe(terpy)2]2+ complex is formed with the copper(i) ions placed in the phenanthroline cavities (OPEN-II). Due to its coordinatively unsaturated [Cu(Phen)]+ sites the dimeric iron complex is able to serve as a catalyst in the cyclopropanation of Z-cyclooctene using ethyl diazoacetate.
- De, Soumen,Pramanik, Susnata,Schmittel, Michael
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supporting information
p. 10977 - 10982
(2014/07/08)
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- Continuous flow asymmetric cyclopropanation reactions using Cu(i) complexes of Pc-L* ligands supported on silica as catalysts with carbon dioxide as a carrier
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Continuous flow heterogeneous asymmetric cyclopropanations catalysed by supported hydrogen-bonded (SHB) chiral copper(i) complexes of pyridine containing tetraazamacrocyclic ligands Pc-L* using CO2 as a transport vector are described. The catalytic system showed high stability and good recyclability without loss of activity for at least 24 h in CO2 and catalyst turnover numbers up to 440 were obtained with excellent conversion (up to 99%) and high selectivity (up to 88%). No leaching of copper was observed. Cyclopropane products from both aromatic and aliphatic olefins were obtained in good yields with enantiomeric excesses up to 72%. This journal is the Partner Organisations 2014.
- Castano, Brunilde,Gallo, Emma,Cole-Hamilton, David J.,Dal Santo, Vladimiro,Psaro, Rinaldo,Caselli, Alessandro
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supporting information
p. 3202 - 3209
(2014/06/10)
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- Catalytic activity and selectivity of a range of ruthenium complexes tested in the styrene/EDA reaction system
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The complex ensemble of competing chemical processes (cyclopropanation, metathesis, dimerisation) involved in the reaction of ethyl diazoacetate with styrene is examined in the presence of a panel of ten ruthenium complexes. Our results, focusing on the catalysts' activity and selectivity, showcased the new NHC-containing complex 10 and the Fischer carbene 7 as leading to best chemoselectivities for cyclopropanation while the bidentate Schiff-base complexes 3 and 4 provided highest stereoselectivity. The traditionally metathesis-active Grubbs I catalyst (5) could be manipulated, by working under high dilution, to display moderate activity in cyclopropanation whereas the Grubbs II catalyst (6) totally promoted metathesis. Data obtained with the above set of Ru complexes strongly support the premise that ligand structure and configuration in the Ru coordination sphere are essential factors in controlling the reaction pathways.
- Dragutan, Ileana,Ding, Fu,Sun, Ya-Guang,Verpoort, Francis,Dragutan, Valerian
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- Elemental reductants for the deoxydehydration of glycols
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The elements zinc, iron, manganese, and carbon are demonstrated to be practical reductants for the oxorhenium catalyzed deoxydehydration (DODH) of biomass model polyols. These reductants and their oxidization products remain heterogeneous throughout the reaction, which aids in their separation. Their effectiveness is shown with the catalysts ammonium perrhenate and trans-[(Py)4Re(O)2]+Z- (1). Stoichiometric experiments with the Re(V) complex indicate a likely rhenium 5?7 oxidation cycle for the deoxydehydration of polyols reported herein.
- Michael McClain,Nicholas, Kenneth M.
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p. 2109 - 2112
(2014/07/21)
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- Synthesis, structural characterization, reactivity, and catalytic properties of copper(I) complexes with a series of tetradentate tripodal tris(pyrazolylmethyl)amine ligands
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Novel tris(pyrazolylmethyl)amine ligands TpaMe3, Tpa*,Br, and TpaBr3 have been synthesized and structurally characterized. The coordination chemistries of these three new tetradentate tripodal ligands and the already known Tpa and Tpa* have been explored using different copper(I) salts as starting materials. Cationic copper(I) complexes [TpaxCu]PF6 (1-4) have been isolated from the reaction of [Cu(NCMe)4]PF6 and 1 equiv of the ligand. Complexes 2 (Tpax = Tpa*) and 3 (Tpax = TpaMe3) have been characterized by X-ray studies. The former is a 1D helical coordination polymer, and the latter is a tetranuclear helicate. In both structures, the Tpax ligand adopts a μ2: κ2:κ1-coordination mode. However, in solution, all of the four complexes form fluxional species. When CuI is used as the copper(I) source, neutral compounds 5-8 have been obtained. Complexes 6-8 exhibit a 1:1 metal-to-ligand ratio, whereas 5 presents 2:1 stoichiometry. Its solid-state structure has been determined by X-ray diffraction, revealing its 3D polymeric nature. The polymer is composed by the assembly of [Tpa 2Cu4I4] units, in which Cu4I 4 presents a step-stair structure. The Tpa ligands bridge the Cu 4I4 clusters, adopting also a μ2: κ2:κ1-coordination mode. As observed for the cationic derivatives, the NMR spectra of 5-8 show the equivalence of the three pyrazolyl arms of the ligands in these complexes. The reactivities of cationic copper(I) derivatives 1-4 with PPh3 and CO have been explored. In all cases, 1:1 adducts [TpaxCuL]PF6 [L = PPh3 (9-11), CO (12-15)] have been isolated. The crystal structure of [Tpa*Cu(PPh3)]PF6 (9) has been obtained, showing that the coordination geometry around copper(I) is trigonal-pyramidal with the apical position occupied by the tertiary amine N atom. The Tpa* ligand binds the Cu center to three of its four N atoms, with one pyrazolyl arm remaining uncoordinated. In solution, the carbonyl adducts 13-15 exist as a mixture of two isomers; the four- and five-coordinate species can be distinguished by means of their IR νCO stretching bands. Finally, the catalytic activities of complexes 1-4 have been demonstrated in carbene- and nitrene-transfer reactions.
- Haldon, Estela,Delgado-Rebollo, Manuela,Prieto, Auxiliadora,Alvarez, Eleuterio,Maya, Celia,Nicasio, M. Carmen,Perez, Pedro J.
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supporting information
p. 4192 - 4201
(2014/05/06)
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- METHOD FOR CONTINUOUSLY PREPARING CARBOXYLIC ACID ESTER
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A method for continuously preparing a carboxylic acid ester is disclosed. In the method of the present invention, a vertical reactor is filled with a solid catalyst, a carboxylic acid and an alcohol are introduced into a lower part of the vertical reactor, esterification is performed to form an esterized mixture, the esterized mixture is output from an upper part of the vertical reactor, and distillation is performed to isolate the carboxylic acid ester. The method of the present invention is simple, easily controlled and environmental friendly, and has significantly high conversion rate and selectivity.
- -
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Paragraph 0031; 0034
(2013/11/19)
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- Vanadium-catalyzed deoxydehydration of glycols
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A survey of several metavandate (VO3-) and chelated dioxovanadium derivatives shows that tetrabutylammonium dioxovanadium(v) dipicolinate most effectively catalyzes the deoxydehydration (DODH) of glycols to olefins in moderate to excellent yields with triphenylphosphine or sodium sulfite as reductants.
- Chapman Jr., Garry,Nicholas, Kenneth M.
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supporting information
p. 8199 - 8201
(2013/09/12)
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- Gold-catalyzed formal cycloaddition of 2-ethynylbenzyl ethers with organic oxides and α-diazoesters
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A world of possibilities: Gold-catalyzed reactions of 2-ethynylbenzyl ethers with organic oxides and α-diazoesters gave 1,3-dihydroisobenzofuran and naphthalene derivatives, respectively (see scheme; EWG=electron-withdrawing group). Mechanisms for the formation of the formal cycloadducts were elucidated by isotope labeling. Copyright
- Pawar, Samir Kundlik,Wang, Chiou-Dong,Bhunia, Sabyasachi,Jadhav, Appaso Mahadev,Liu, Rai-Shung
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supporting information
p. 7559 - 7563
(2013/07/26)
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- Iridium porphyrin catalyzed N-H insertion reactions: Scope and mechanism
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Ir(TTP)CH3 catalyzed N-H insertion reactions between ethyl diazoacetate (EDA) or methyl phenyldiazoacetate (MPDA) and a variety of aryl, aliphatic, primary, and secondary amines to generate substituted glycine esters with modest to high yields. Aniline substrates generally gave yields above 80%, with up to 105 catalyst turnovers, and without slow addition of the diazo reagent. Good yields were also achieved with aliphatic amines, though higher catalyst loadings and slow addition of the amine were necessary in some cases. Primary amines reacted with EDA to generate both single- and double-insertion products, either of which could be produced selectively in high yield with the proper choice of stoichiometric ratios and reaction temperature. Notably, mixed trisubstituted amines, RN(CH2CO2Et) (CHPhCO2Me), were generated from the insertion of 1 equiv of EDA and 1 equiv of MPDA into primary amines. The N-H insertion mechanism was examined using substrate competition studies, trapping experiments, and multiple spectroscopic techniques. Substrate competition studies using pairs of amines with EDA or MPDA revealed Hammett correlations with respective slopes of ρ = 0.15 and ρ+ = -0.56 as well as kinetic isotope ratios of k H/kD = 1.0 ± 0.2 and 2.7 ± 0.2. Competitive amine binding to the iridium center was demonstrated by kinetics and equilibrium binding studies. Equilibrium binding constants ranged from 102 to 105. Monitoring the reaction by absorption spectroscopy revealed a transient metalloporphyrin complex. The lifetime of this species was dependent on the nature of the amine substrate, which suggests that the catalytic cycle proceeds through a metal-ylide intermediate.
- Anding, Bernie J.,Woo, L. Keith
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p. 2599 - 2607
(2013/06/26)
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- The role of the support properties in the catalytic performance of an anchored copper(ii) aza-bis(oxazoline) in mesoporous silicas and their carbon replicas
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A copper(ii) chiral aza-bis(oxazoline) catalyst (CuazaBox) was anchored onto ordered mesoporous silicas and their carbon replicas. The materials were characterized by elemental analysis (C, N, H, S), ICP-AES, FTIR, XPS, thermogravimetry and isotherms of N2 adsorption at -196 °C. The materials were tested as heterogeneous catalysts in the reaction of cyclopropanation of styrene to check the effect of porous material type on the catalytic parameters, as well as on their reutilization. Generally, the composites were more active and enantioselective in the cyclopropanation of styrene than the corresponding homogeneous phase reaction run under similar experimental conditions. The materials pHpzc proved to be an important factor not only in the CuazaBox anchoring yields, but also in their catalytic performance. Less acidic surfaces (SPSi and CMK-3) yielded heterogeneous catalysts with higher styrene conversion and enantioselectivity. The materials could also be recycled with comparable enantioselectivities or generally a slight decrease in the enantioselectivity.
- Silva, Ana Rosa,Guimaraes, Vanessa,Carvalho, Ana Paula,Pires, Joao
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p. 659 - 672
(2013/04/23)
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- Catalytic deoxydehydration of glycols with alcohol reductants
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Top shelf dehydration: Ammonium perrhenate catalysts combined with benzylic alcohol reductants are used for the efficient deoxydehydration of glycols to olefins. The olefin and aldehyde products can be easily separated and isolated. It is also demonstrated that the catalyst can be recovered and reused because of its low solubility in aromatic solvents.
- Boucher-Jacobs, Camille,Nicholas, Kenneth M.
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p. 597 - 599
(2013/07/27)
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- Deoxydehydration of glycols catalyzed by carbon-supported perrhenate
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Support group: The first heterogeneous catalyst for the deoxydehydration (DODH) of glycols into olefins is reported. A carbon-supported perrhenate material was found to catalyze the reductive conversions of styrene diol, tetradecane diol, and diethyl tartrate into their respective olefins with high chemo-, regio-, and stereoselectivity. Effective reductants for this DODH reaction include H2, alcohols, and tetralin. Copyright
- Denning, Alana L.,Dang, Huong,Liu, Zhimin,Nicholas, Kenneth M.,Jentoft, Friederike C.
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p. 3567 - 3570
(2014/01/06)
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- Hydrotris(3-mesitylpyrazolyl)borato-copper(i) alkyne complexes: Synthesis, structural characterization and rationalization of their activities as alkyne cyclopropenation catalysts
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The use of the bulky hydrotris(3-mesitylpyrazolyl)borate anionic ligand has allowed the synthesis of stable TpMsCu(alkyne) complexes (alkyne = 1-hexyne, 1, phenylacetylene, 2, and ethyl propiolate, 3). The spectroscopic and structural features of these compounds and their relative reactivity have been examined, indicating the existence of a low π back-bonding from the copper(i) centre to the alkyne. Ligand exchange experiments have shown that terminal alkyne adducts are more stable than internal alkyne analogues. In good accordance with this, the previously reported alkyne cyclopropenation reaction catalysed by the TpxCu complexes can be rationalized and correlated with their relative stability.
- Martin, Carmen,Sierra, Marta,Alvarez, Eleuterio,Belderrain, Tomas R.,Perez, Pedro J.
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experimental part
p. 5319 - 5325
(2012/05/20)
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- Enantioselective cyclopropanation of indoles: Construction of all-carbon quaternary stereocenters
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The first enantioselective copper-catalyzed cyclopropanation of N-acyl indoles is described. Using carbohydrate-based bis(oxazoline) ligands (glucoBox), the products were obtained in up to 72% ee. Cyclopropanation of N-Boc 3-methyl indole yielded a product with an all-carbon quaternary stereocenter, which is a valuable building block for the synthesis of indole alkaloids: Deprotection and rearrangement gave a tricyclic hemiaminal ester in 96% ee, which was subsequently employed as a key intermediate for the synthesis of (-)-desoxyeseroline.
- ?züduru, Gülsüm,Schubach, Thea,Boysen, Mike M. K.
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supporting information
p. 4990 - 4993
(2013/01/15)
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- Ruthenium catalyzed synthesis of enaminones
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The Grubbs first-generation catalyst has been found to be an effective catalyst for the synthesis of enaminones by coupling thioamides with α-diazodicarbonyl compounds. The reaction is successful in converting primary, secondary, and tertiary thioamides into their corresponding enaminones. The reaction is also suitable for the synthesis of chiral enaminones.
- Koduri, Naga Durgarao,Scott, Halee,Hileman, Bethany,Cox, Justin D.,Coffin, Michael,Glicksberg, Lindsay,Hussaini, Syed R.
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supporting information; experimental part
p. 440 - 443
(2012/03/10)
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- Ruthenium(II) complexes bearing a ligand derived from P, N - Or P, N, O-diphenylphosphinobenzoxazine: Synthesis, X-ray characterization, and cis diastereoselectivity in styrene cyclopropanation
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A phosphino-oxazine based ligand (L; 2-(2-(diphenylphosphino)phenyl)-2,4- dihydro-1H-benzo[d][1,3]oxazine) showing a temperature-dependent equilibrium between a closed bidentate (LPN) and an opened tridentate (L PNO) form, has been synthesized and its coordination behavior toward ruthenium(II) centers studied. Under different experimental conditions, two different species bearing the ligand in either its bidentate or tridentate coordination mode were isolated by reaction with Ru(PPh3) 3Cl2. These species, respectively formulated as [Ru(PPh3)(LPNO)Cl2] (1) and [Ru(PPh 3)(LPN)Cl2] (2), were fully characterized via NMR in solution and by an X-ray structural determination. Notably, compound 2 reacts with an excess of ethyl diazoacetate (EDA) in CH2Cl 2 to give a stable η3-diethyl maleate complex, [Ru(LPN)(cis-EtO(O)CCH=CHC(O)OEt)Cl2] (3). The crystal structure of 3 has also been determined. Substitution reactions with 4-picoline (4-Me-py) performed on 1 led to two new complexes: the neutral complex [Ru(4-Me-py)(LPNO)Cl2] (5) and the salt [Ru(4-Me-py) 2(LPNO)Cl](Cl) (6a). The latter compound catalyzed the intermolecular cyclopropanation of styrene with EDA in high yields and with elevated cis diastereoselectivity (i.e., cis/trans = 80/20).
- Ardizzoia, G. Attilio,Brenna, Stefano,Durini, Sara,Therrien, Bruno
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p. 5427 - 5437
(2012/11/13)
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