- γ-irradiated [(CH3)4N]2SiF6 single crystal investigation by electron paramagnetic resonance technique
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In this study, γ-irradiation damage centers in [(CH3)4N]2SiF6 single crystal has been investigated by electron paramagnetic resonance spectroscopy (EPR) at room temperature. It has been found that γ-irradiation produces the (CH3)3 over(N, ?)+ radicals in this compound. The g factor and the hyperfine constant for H atoms, measured as 28.7 G, were found to be isotropic. The hyperfine coupling constant of the N nucleus, observed (CH3)3 over(N, ?)+ hole radical in [(CH3)4N]2SiF6 was found to be anisotropic with A// = 15 and A⊥ = 23 G, respectively. This means that each methyl groups rotate around the C3 ν-axis and they also rotate around the C3 ν-axis of (CH3)3 over(N, ?)+ radical. These results were compared with the earlier studies in (CH3)3 over(N, ?)+ radical and discussed.
- Bozkurt,Kartal, I.,Karabulut
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- Novel self assembling nanoparticles for the oral administration of fondaparinux: Synthesis, characterization and in vivo evaluation
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Fondaparinux (Fpx) is the anticoagulant of choice in the treatment of short- and medium-term thromboembolic disease. To overcome the low oral bioavailability of Fpx, a new nanoparticulate carrier has been developed. The nanoparticles (NPs) contain squalenyl derivatives, known for their excellent oral bioavailability. They spontaneously self-assemble upon both electrostatic and hydrophobic interactions between the polyanionic Fpx and cationic squalenyl (CSq) derivatives. The preparation conditions were optimized to obtain monodisperse, stable NPs with a mean diameter in the range of 150-200 nm. The encapsulation efficiencies were around 80%. Fpx loadings reached 39 wt.%. According to structural and morphological analysis, Fpx and CSq organized in spherical multilamellar ("onion-type") nanoparticles. Furthermore, in vivo studies in rats suggested that Fpx was well absorbed from the orally administered NPs, which totally dissociated when reaching the blood stream, leading to the release of free Fpx. The Fpx:CSq NPs improved the plasmatic concentration of Fpx in a dose-dependent manner. However, the oral bioavailability of these new NPs remained low (around 0.3%) but of note, the Cmax obtained after oral administration of 50 mg/kg NPs was close to the prophylactic plasma concentration needed to treat venous thromboembolism. Moreover, the oral bioavailability of Fpx could be dramatically increased up to 9% by including the nanoparticles into gastroresistant capsules. This study opens up new perspectives for the oral administration of Fpx and paves the way towards elaborating squalene-based NPs which self assemble without the need of covalently grafting the drug to Sq.
- Ralay-Ranaivo, Bettina,Desma?le, Didier,Bianchini, Elsa P.,Lepeltier, Elise,Bourgaux, Claudie,Borgel, Delphine,Pouget, Thierry,Tranchant, Jean Fran?ois,Couvreur, Patrick,Gref, Ruxandra
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- Replica of a fishy enzyme: Structure-function analogue of trimethylamine-n-oxide reductase
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Three new complexes, [MoIVO(mnt)(SS)]2- (SS = dimethylethylenedicarboxylate (DMED), toluenedithiolate (tdt), benzenedithiolate (bdt); mnt = maleonitriledithiolate), each possessing two different dithiolene ligands, are synthesized as model of trimethylamine-N-oxide reductase. The asymmetric dithiolene ligands present in these complexes simulate the two different (P and Q) pterin coordinations in the family of DMSO reductase. These complexes reduce trimethylamine-N-oxide ((CH3)3N +-O- or TMANO), the biological substrate of trimethylamine-N-oxide reductase, to trimethylamine ((CH3) 3N), responsible for the fishy smell of dead aquatic animals. The reaction kinetics of trimethylamine-N-oxide reduction by these complexes follow the Michaelis-Menten saturation kinetics. These experimental findings have been rationalized by DFT, TD-DFT level of calculations.
- Moula, Golam,Bose, Moumita,Sarkar, Sabyasachi
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- Electrochemical decomposition of choline chloride based ionic liquid analogues
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Ionic liquids are studied intensively for electrochemical applications and more specifically for the electrodeposition of metals. In this paper the electrochemical stability of a deep-eutectic solvent based on choline chloride and ethylene glycol is studied over longer periods of electrolysis. The formation of several decomposition products such as 2-methyl-1,3-dioxolane was observed. Possible mechanisms for the formation of these products are given: some products involve a reaction at either the anode or the cathode, while others can be explained by consecutive reactions of reaction products formed at both electrodes. A range of chlorinated products like chloromethane, dichloromethane and chloroform could be detected as well. This is remarkable as evolution of chlorine gas at the anode is not observed. The formation of the chlorinated products is ascribed to the existence of the Cl3 - ion in the solution. The presence of the Cl3- ion was observed photometrically. The presence of chlorinated products gives rise to a larger environmental impact and higher risks for health and safety, and it questions the "greenness" of these ionic liquid analogues. To reduce the decomposition of the solvent, water and easily oxidizable acids were added as 'sacrificial agents'. Their influence on the formation of 2-methyl-1,3-dioxolane was quantified. However, the addition of the sacrificial agents did not improve the stability of the solvent. Addition of formic acid reduced the formation of 2-methyl-1,3-dioxolane but chlorinated products could still be detected. Water reduced the formation of chlorinated products. The Royal Society of Chemistry 2009.
- Haerens, Kurt,Matthijs, Edward,Binnemans, Koen,Van Der Bruggen, Bart
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- Structural basis of carnitine monooxygenase CntA substrate specificity, inhibition, and intersubunit electron transfer
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Microbial metabolism of carnitine to trimethylamine (TMA) in the gut can accelerate atherosclerosis and heart disease, and these TMA-producing enzymes are therefore important drug targets. Here, we report the first structures of the carnitine oxygenase CntA, an enzyme of the Rieske oxygenase family. CntA exists in a head-to-tail α3 trimeric structure. The two functional domains (the Rieske and the catalytic mononuclear iron domains) are located >40 A apart in the same monomer but adjacent in two neighboring monomers. Structural determination of CntA and subsequent electron paramagnetic resonance measurements uncover the molecular basis of the so-called bridging glutamate (E205) residue in intersubunit electron transfer. The structures of the substrate-bound CntA help to define the substrate pocket. Importantly, a tyrosine residue (Y203) is essential for ligand recognition through a π- cation interaction with the quaternary ammonium group. This interaction between an aromatic residue and quaternary amine substrates allows us to delineate a subgroup of Rieske oxygenases (group V) from the prototype ring-hydroxylating Rieske oxygenases involved in bioremediation of aromatic pollutants in the environment. Furthermore, we report the discovery of the first known CntA inhibitors and solve the structure of CntA in complex with the inhibitor, demonstrating the pivotal role of Y203 through a π-π stacking interaction with the inhibitor. Our study provides the structural and molecular basis for future discovery of drugs targeting this TMA-producing enzyme in human gut.
- Bugg, Timothy D. H.,Cameron, Alexander D.,Chen, Yin,Jameson, Eleanor,Quareshy, Mussa,Shanmugam, Muralidharan,Townsend, Eleanor
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- Heterogeneous platinum catalysts for direct synthesis of trimethylamine by N-methylation of ammonia and its surrogates with CO2/H2
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Direct synthesis of trimethylamine through N-methylation of NH3 or its surrogate (NH4HCO3) with both CO2 and H2 has been achieved by employing Pt and MoOx coloaded TiO2 (Pt-MoOx/TiO2). Pt-MoOx/TiO2 was found to be superior to other supported Pt and transition-metal-loaded MoOx/TiO2 catalysts for the trimethylamine synthesis process.
- Toyao, Takashi,Siddiki, S. M. A. Hakim,Ishihara, Keisuke,Kon, Kenichi,Onodera, Wataru,Shimizu, Ken-Ichi
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- Deoxygenation of primary amides to amines with pinacolborane catalyzed by Ca[N(SiMe3)2]2(THF)2
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Deoxygenative reduction of amides is a challenging but favorable synthetic method of accessing amines. In the presence of a catalytic amount of Ca[N(SiMe3)2]2(THF)2, pinacolborane (HBpin) could efficiently reduce a broad scope of amides, primary amides in particular, into corresponding amines. Functional groups and heteroatoms showed good tolerance in this process of transformation, and a plausible reaction mechanism was proposed.
- Gong, Mingliang,Guo, Chenjun,Jiang, Linhong,Luo, Yunjie,Yu, Chong
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supporting information
p. 1201 - 1206
(2021/05/29)
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- Lithium compound catalyzed deoxygenative hydroboration of primary, secondary and tertiary amides
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A selective and efficient route for the deoxygenative reduction of primary to tertiary amides to corresponding amines has been achieved with pinacolborane (HBpin) using simple and readily accessible 2,6-di-tert-butyl phenolate lithium·THF (1a) as a catalyst. Both experimental and DFT studies provide mechanistic insight. This journal is
- Bisai, Milan Kumar,Gour, Kritika,Das, Tamal,Vanka, Kumar,Sen, Sakya S.
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supporting information
p. 2354 - 2358
(2021/03/03)
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- Reduction of Amides to Amines with Pinacolborane Catalyzed by Heterogeneous Lanthanum Catalyst La(CH2C6H4NMe2- o)3@SBA-15
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Hydroboration of amides is a useful synthetic strategy to access the corresponding amines. In this contribution, it was found that the supported lanthanum benzyl material La(CH2C6H4NMe2-o)3@SBA-15 was highly active for the hydroboration of primary, secondary, and tertiary amides to amines with pinacolborane. These reactions selectively produced target amines and showed good tolerance for functional groups such as -NO2, -halogen, and -CN, as well as heteroatoms such as S and O. This reduction procedure exhibited the recyclable and reusable property of heterogeneous catalysts and was applicable to gram-scale synthesis. The reaction mechanisms were proposed based on some control experiments and the previous literature. This is the first example of hydroborative reduction of amides to amines mediated by heterogeneous catalysts.
- Guo, Chenjun,Zhang, Fangcao,Yu, Chong,Luo, Yunjie
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supporting information
p. 13122 - 13135
(2021/08/31)
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- Electrochemical Reductive N-Methylation with CO2Enabled by a Molecular Catalyst
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The development of benign methylation reactions utilizing CO2 as a one-carbon building block would enable a more sustainable chemical industry. Electrochemical CO2 reduction has been extensively studied, but its application for reductive methylation reactions remains out of the scope of current electrocatalysis. Here, we report the first electrochemical reductive N-methylation reaction with CO2 and demonstrate its compatibility with amines, hydroxylamines, and hydrazine. Catalyzed by cobalt phthalocyanine molecules supported on carbon nanotubes, the N-methylation reaction proceeds in aqueous media via the chemical condensation of an electrophilic carbon intermediate, proposed to be adsorbed or near-electrode formaldehyde formed from the four-electron reduction of CO2, with nucleophilic nitrogenous reactants and subsequent reduction. By comparing various amines, we discover that the nucleophilicity of the amine reactant is a descriptor for the C-N coupling efficacy. We extend the scope of the reaction to be compatible with cheap and abundant nitro-compounds by developing a cascade reduction process in which CO2 and nitro-compounds are reduced concurrently to yield N-methylamines with high monomethylation selectivity via the overall transfer of 12 electrons and 12 protons.
- Rooney, Conor L.,Wu, Yueshen,Tao, Zixu,Wang, Hailiang
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supporting information
p. 19983 - 19991
(2021/12/01)
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- Light-Activated Electron Transfer and Catalytic Mechanism of Carnitine Oxidation by Rieske-Type Oxygenase from Human Microbiota
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Oxidation of quaternary ammonium substrate, carnitine by non-heme iron containing Acinetobacter baumannii (Ab) oxygenase CntA/reductase CntB is implicated in the onset of human cardiovascular disease. Herein, we develop a blue-light (365 nm) activation of NADH coupled to electron paramagnetic resonance (EPR) measurements to study electron transfer from the excited state of NADH to the oxidized, Rieske-type, [2Fe-2S]2+ cluster in the AbCntA oxygenase domain with and without the substrate, carnitine. Further electron transfer from one-electron reduced, Rieske-type [2Fe-2S]1+ center in AbCntA-WT to the mono-nuclear, non-heme iron center through the bridging glutamate E205 and subsequent catalysis occurs only in the presence of carnitine. The electron transfer process in the AbCntA-E205A mutant is severely affected, which likely accounts for the significant loss of catalytic activity in the AbCntA-E205A mutant. The NADH photo-activation coupled with EPR is broadly applicable to trap reactive intermediates at low temperature and creates a new method to characterize elusive intermediates in multiple redox-centre containing proteins.
- Shanmugam, Muralidharan,Quareshy, Mussa,Cameron, Alexander D.,Bugg, Timothy D. H.,Chen, Yin
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supporting information
p. 4529 - 4534
(2020/12/29)
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- In Vitro Reconstitution of a Five-Step Pathway for Bacterial Ergothioneine Catabolism
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Ergothioneine is a histidine-derived sulfur metabolite that is biosynthesized by bacteria and fungi. Plants and animals absorb ergothioneine as a micronutrient from their environment or nutrition. Several different mechanisms of microbial ergothioneine production have been described in the past ten years. Much less is known about the genetic and structural basis for ergothioneine catabolism. In this report, we describe the in vitro reconstitution of a five-step pathway that degrades ergothioneine to l-glutamate, trimethylamine, hydrogen sulfide, carbon dioxide, and ammonia. The first two steps are catalyzed by the two enzymes ergothionase and thiourocanate hydratase. These enzymes are closely related to the first two enzymes in histidine catabolism. However, the crystal structure of thiourocanate hydratase from the firmicute Paenibacillus sp. reveals specific structural features that strictly differentiate the activity of this enzyme from that of urocanate hydratases. The final two steps are catalyzed by metal-dependent hydrolases that share most homology with the last two enzymes in uracil catabolism. The early and late part of this pathway are connected by an entirely new enzyme type that catalyzes desulfurization of a thiohydantoin intermediate. Homologous enzymes are encoded in many soil-dwelling firmicutes and proteobacteria, suggesting that bacterial activity may have a significant impact on the environmental availability of ergothioneine.
- Beliaeva, Mariia A.,Leisinger, Florian,Seebeck, Florian P.
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p. 397 - 403
(2021/03/08)
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- Thermal Decomposition of Aluminium Hydride Complexes with Trimethylamine and N-Heterocyclic Carbene
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Abstract: The decomposition of aluminum hydride complexes with trimethylamine andN-heterocyclic carbene—1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene was studied by a statictensimetric method with a membrane null-manometer. TheAlH3·NMe3 complex passes intovapor in the form of monomeric molecules and in unsaturated vapor slowlydecomposes at 70?80°С into solid aluminum, gaseous trimethylamine, and hydrogen.The decomposition is accompanied by an induction period, the duration of whichdecreases as temperature increases. The AlH3 complex withcarbene slowly decomposes at 170?200°С with a rate practically independent oftemperature.
- Chernysheva, A. M.,Doinikov, D. A.,Kazakov, I. V.,Kravtcov, D. V.,Shcherbina, N. A.,Timoshkin, A. Yu.,Zavgorodnii, A. S.
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p. 1969 - 1976
(2021/11/13)
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- A Lewis Base Nucleofugality Parameter, NFB, and Its Application in an Analysis of MIDA-Boronate Hydrolysis Kinetics
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The kinetics of quinuclidine displacement of BH3 from a wide range of Lewis base borane adducts have been measured. Parameterization of these rates has enabled the development of a nucleofugality scale (NFB), shown to quantify and predict the leaving group ability of a range of other Lewis bases. Additivity observed across a number of series R′3-nRnX (X = P, N; R′ = aryl, alkyl) has allowed the formulation of related substituent parameters (nfPB, nfAB), providing a means of calculating NFB values for a range of Lewis bases that extends far beyond those experimentally derived. The utility of the nucleofugality parameter is explored by the correlation of the substituent parameter nfPB with the hydrolyses rates of a series of alkyl and aryl MIDA boronates under neutral conditions. This has allowed the identification of MIDA boronates with heteroatoms proximal to the reacting center, showing unusual kinetic lability or stability to hydrolysis.
- García-Domínguez, Andrés,Gonzalez, Jorge A.,Leach, Andrew G.,Lloyd-Jones, Guy C.,Nichol, Gary S.,Taylor, Nicholas P.
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supporting information
(2022/01/04)
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- CONSTANT SHEAR CONTINUOUS REACTOR DEVICE
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Disclosed herein is a constant shear continuous reactor device, comprising: an annular gas delivery tube comprising a gas inlet and a gas outlet; a first annular liquid delivery tube comprising a first liquid inlet and a first liquid outlet arranged concentrically around the annular gas delivery tube along a common axis, where the first liquid outlet is located at a downstream position relative to the gas outlet or is coterminous with the gas outlet; and an annular reactor wall tube comprising a final liquid inlet, a mixing zone section and a reactor outlet, where the annular reactor wall tube is arranged concentrically around the first annular liquid delivery tube along the common axis.
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- Catalytic Deoxygenation of Amine and Pyridine N-Oxides Using Rhodium PCcarbeneP Pincer Complexes
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Rhodium PCcarbeneP pincer complexes 1-L (L = PPh3, PPh2(C6F5), PCy3) readily facilitate deoxygenation of amine and pyridine N-oxides. The resulting complexes exhibit δ2-C= O coordination of the resulting keto POP pincer ligand. These δ2-Ca? O linkages in the metalloepoxide complexes are readily reduced by isopropyl alcohol and various benzylic alcohols. Thus, efficient catalytic deoxygenation of amine and pyridine N-oxides is possible using complexes 1-L and isopropyl alcohol. This represents a pioneering example of PCcarbeneP pincer complexes being used as catalysts for catalytic deoxygenation.
- Tinnermann, Hendrik,Sung, Simon,Cala, Beatrice A.,Gill, Hashir J.,Young, Rowan D.
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p. 797 - 803
(2020/03/13)
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- Towards environmentally benign capture and conversion: Heterogeneous metal catalyzed CO2 hydrogenation in CO2 capture solvents
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The transformation of captured CO2 into value-added chemicals to mitigate increasing CO2 concentration in the atmosphere has gained significant attention recently. Though carbon capture and storage (CCS) is already being practiced in a few places, it suffers from energy-intensive CO2 desorption and compression steps involved, which can be avoided in the carbon capture and utilization (CCU) approach. Herein, a selection of carbon capture solvents were screened to assess the reactivity of condensed-phase heterogeneous metal catalyzed hydrogenation of CO2. Among the catalysts screened, the Cu/ZnO/Al2O3 catalyst was active for the one-pot CO2 capture and conversion process to methanol using post and pre-combustion carbon capture solvents comprised of various amines and alcohols. Our findings indicate that formamides are less-reactive under our conditions in comparison with formate ester intermediates and a combination of 1° alcohols and amines gives the highest methanol yield. Screening volatile organic compound (VOC)-free alcohols and amines led us to an environmentally benign system of bio-derived and biodegradable chitosan and polyethylene glycol (PEG200), which provide a moderate concentration of methanol (139.5 mmol L-1) with the facile separation of volatile products (water and methanol). The chitosan/PEG200 system was recycled three times, ultimately providing a promising VOC-free, biodegradable, bio-derived and recyclable CO2 capture and conversion pathway.
- Kothandaraman, Jotheeswari,Heldebrant, David J.
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p. 828 - 834
(2020/02/27)
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- Mild catalytic deoxygenation of amides promoted by thorium metallocene
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The organoactinide-catalyzed (Cp*2ThMe2) hydroborated reduction of a wide range of tertiary, secondary, and primary amides to the corresponding amines/amine-borane adductsviadeoxygenation of the amides is reported herein. The catalytic reactions proceed under mild conditions with low catalyst loading and pinacolborane (HBpin) concentration in a selective fashion. Cp*2ThMe2is capable of efficiently catalysing the gram-scale reaction without a drop in efficiency. The amine-borane adducts are successfully converted into free amine products in high conversions, which increases the usefulness of this catalytic system. A plausible mechanism is proposed based on detailed kinetics, stoichiometric, and deuterium labeling studies.
- Eisen, Moris S.,Saha, Sayantani
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supporting information
p. 12835 - 12841
(2020/10/05)
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- UV Light Generation and Challenging Photoreactions Enabled by Upconversion in Water
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Sensitized triplet-triplet annihilation (sTTA) is the most promising mechanism for pooling the energy of two visible photons, but its applications in solution were so far limited to organic solvents, with a current maximum of the excited-singlet state energy of 3.6 eV. By combining tailor-made iridium complexes with naphthalenes, we demonstrate blue-light driven upconversion in water with unprecedented singlet-state energies approaching 4 eV. The annihilators have outstanding excited-state reactivities enabling challenging photoreductions driven by sTTA. Specifically, we found that an aryl-bromide bond activation can be achieved with blue photons, and we obtained full conversion for the very energy-demanding decomposition of a persistent ammonium compound as typical water pollutant, not only with a cw laser but also with an LED light source. These results provide the first proof-of-concept for the usage of low-power light sources for challenging reactions employing blue-to-UV upconversion in water and pave the way for the further development of sustainable light-harvesting applications.
- Pfund, Bj?rn,Steffen, Debora M.,Schreier, Mirjam R.,Bertrams, Maria-Sophie,Ye, Chen,B?rjesson, Karl,Wenger, Oliver S.,Kerzig, Christoph
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supporting information
p. 10468 - 10476
(2020/07/27)
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- Mononuclear iron complex and organic synthesis reaction using same
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A mononuclear iron bivalent complex having iron-silicon bonds, which is represented by formula (1), can exhibit an excellent catalytic activity in at least one reaction selected from three reactions, i.e., a hydrosilylation reaction, a hydrogenation reaction and a reaction for reducing a carbonyl compound. (In the formula, R1 to R6 independently represent a hydrogen atom, an alkyl group which may be substituted by X, or the like; X represents a halogen atom, or the like; L1 represents at least one two-electron ligand selected from an isonitrile ligand, an amine ligand, an imine ligand, a nitrogenated heterocyclic ring, a phosphine ligand, a phosphite ligand and a sulfide ligand, wherein, when multiple L1's are present, two L1's may be bonded to each other; L2 represents a two-electron ligand that is different from a CO ligand or the above-mentioned L1, wherein, when multiple L2's are present, two L2's may be bonded to each other; and m1 represents an integer of 1 to 4 and m2 represents an integer of 0 to 3, wherein the sum total of m1 and m2 (i.e., m1+m2) satisfies 3 or 4.)
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Page/Page column 22; 35
(2019/08/20)
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- Bench-Stable Cobalt Pre-Catalysts for Mild Hydrosilative Reduction of Tertiary Amides to Amines and Beyond
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The readily synthesized and bench-stable cobalt dichloride complex (dpephos)CoCl2 is employed as a pre-catalyst for a diversity of silane additions to unsaturated organic molecules, including the normally challenging reduction of amides to amines. With regard to hydrosilative reduction of amides even more effective and activator free catalytic systems can be generated from the bench-stable, commercially available Co(acac)2 and Co(OAc)2 with dpephos and PPh3 ligands. These systems operate under mild conditions (100 °C), with many examples of room temperature transformations, presenting a first example of mild cobalt-catalyzed hydrosilylation of amides.
- Nurseiit, Alibek,Janabel, Jaysan,Gudun, Kristina A.,Kassymbek, Aishabibi,Segizbayev, Medet,Seilkhanov, Tulegen M.,Khalimon, Andrey Y.
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p. 790 - 798
(2019/01/09)
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- POCN Ni(ii) pincer complexes: Synthesis, characterization and evaluation of catalytic hydrosilylation and hydroboration activities
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A series of iminophosphinite POCN pincer Ni(ii) complexes, (POCN)NiMe and (POCN)NiLn(BX4) (L = CH3CN, n = 0, 1; X = F, Ph, C6F5), have been developed and subjected to catalytic hydrosilylation of alkenes, aldehydes and ketones and hydroboration of carbonyl compounds. The stoichiometric reactivity of (POCN)NiMe and (POCN)Ni(BF4) with PhSiH3 and HBPin suggests that catalytic reactions proceed via the hydride intermediate (POCN)NiH. With regard to reactions with HBPin, efficient and mild hydroboration of a variety of carbonyl compounds, including highly chemoselective hydroboration of benzaldehyde in the presence of other common potent reductive functional groups, such as alkenes, alkynes, esters, amides, nitriles, nitro compounds and even ketones, and the first example of base metal catalyzed hydroboration of amides, including mild direct hydroborative reduction of primary and secondary amides to borylated amines were demonstrated for (POCN)NiMe.
- Gudun, Kristina A.,Segizbayev, Medet,Adamov, Assyl,Balanay, Mannix P.,Khalimon, Andrey Y.,Plessow, Philipp N.,Lyssenko, Konstantin A.
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supporting information
p. 1732 - 1746
(2019/03/07)
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- Selective reduction of formamides to O-silylated hemiaminals or methylamines with HSiMe2Ph catalyzed by iridium complexes
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The reaction of (4-methyl-pyridin-2-iloxy)ditertbutylsilane (NSitBu-H, 1) with [IrCl(coe)2]2 affords the iridium(iii) complex [Ir(H)(Cl)(κ2-NSitBu)(coe)] (2), which has been fully characterized including X-ray diffraction studies. The reaction of 2 with AgCF3SO3 leads to the formation of species [Ir(H)(CF3SO3)(κ2-NSitBu)(coe)] (3). The iridium complexes 2 and 3 are effective catalysts for the reduction of formamides with HSiMe2Ph. The selectivity of the reduction process depends on the catalyst. Thus, by using complex 2, with a chloride ancillary ligand, it has been possible to selectively obtain the corresponding O-silylated hemiaminal by reaction of formamides with one equivalent of HSiMe2Ph, while complex 3, with a triflate ligand instead of chloride, catalyzed the selective reduction of formamides to the corresponding methylamine.
- Guzmán, Jefferson,Bernal, Ana M.,García-Ordu?a, Pilar,Lahoz, Fernando J.,Oro, Luis A.,Fernández-Alvarez, Francisco J.
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p. 4255 - 4262
(2019/04/01)
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- Thermal behavior of ammonium dinitramide and amine nitrate mixtures
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This paper focuses on the thermal behavior of mixtures of ammonium dinitramide (ADN) and amine nitrates. Because some mixtures of ADN and amine nitrate exhibit low melting points and high-energy content, they represent potential liquid propellants for spacecraft. This study focused on the melting behavior and thermal-decomposition mechanisms in the condensed phase of ADN/amine nitrate mixtures during heating. We measured the melting point and exothermal behavior during constant-rate heating using differential scanning calorimetry and performed thermogravimetry–differential thermal analysis–mass spectrometry (TG–DTA–MS) to analyze the thermal behavior and evolved gases of ADN/amine nitrate mixtures during simultaneous heating to investigate their reaction mechanisms. Results showed that the melting point of ADN was significantly lowered upon the addition of amine nitrate with relatively low molecular volume and low melting point. TG–DTA–MS results showed that the onset temperature of the thermal decomposition of ADN/amine nitrates was similar to that of pure ADN. Furthermore, during thermal decomposition in the condensed phase, ADN produced highly acidic products that promoted exothermic reactions, and we observed the nitration and nitrosation of amines from the dissociation of amine nitrates.
- Matsunaga, Hiroki,Katoh, Katsumi,Habu, Hiroto,Noda, Masaru,Miyake, Atsumi
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p. 2677 - 2685
(2018/11/23)
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- Unexpected Hydrated Electron Source for Preparative Visible-Light Driven Photoredox Catalysis
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The hydrated electron is experiencing a renaissance as a superreductant in lab-scale reductions driven by light, both for the degradation of recalcitrant pollutants and for challenging chemical reactions. However, examples for its sustainable generation under mild conditions are scarce. By combining a water-soluble Ir catalyst with unique photochemical properties and an inexpensive diode laser as light source, we produce hydrated electrons through a two-photon mechanism previously thought to be unimportant for laboratory applications. Adding cheap sacrificial donors turns our new hydrated electron source into a catalytic cycle operating in pure water over a wide pH range. Not only is that catalytic system capable of detoxifying a chlorinated model compound with turnover numbers of up to 200, but it can also be employed for two novel hydrated electron reactions, namely, the decomposition of quaternary ammonium compounds and the conversion of trifluoromethyl to difluoromethyl groups.
- Kerzig, Christoph,Guo, Xingwei,Wenger, Oliver S.
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supporting information
p. 2122 - 2127
(2019/02/14)
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- Silicoaluminophosphate molecular sieve DNL-6: Synthesis with a novel template, N,N″-dimethylethylenediamine, and its catalytic application
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DNL-6, a silicoaluminophosphate (SAPO) molecular sieve with RHO topology, was hydrothermally synthesized using a new structure-directing agent (SDA), N,N′-dimethylethylenediamine. The obtained samples were characterized by X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy, scanning electron microscopy, and N2 adsorption, which indicated that the synthesized DNL-6s have high crystallinity and relatively high Si content ranging from 20% to 35%. Solid-state magic-angle-spinning (MAS) nuclear magnetic resonance (13C, 29Si, 27Al, 31P, and 27Al multiple-quantum (MQ)) was conducted to investigate the status of the SDA and local atomic environment in the as-synthesized DNL-6. Thermal analysis revealed the presence of a large amount of amines in the DNL-6 crystals (about 4.4 SDAs per α-cage), which was the reason for the formation of DNL-6 with an ultrahigh Si content (36.4% Si per mole). Interestingly, DNL-6 exhibited excellent catalytic performance for methanol amination. More than 88% methanol conversion and 85% methylamine plus dimethylamine selectivity could be achieved due to the combined contribution of strong acid sites, suitable acid distribution, and narrow pore dimensions of DNL-6.
- Wu, Pengfei,Yang, Miao,Zhang, Wenna,Zeng, Shu,Gao, Mingbin,Xu, Shutao,Tian, Peng,Liu, Zhongmin
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p. 1511 - 1519
(2018/07/29)
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- Hydrogenolysis of Amide Acetals and Iminium Esters
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Amide acetals and iminium esters were hydrogenated into amines under very mild reaction conditions over common hydrogenation catalysts. This finding provides a new strategy for the selective reduction of amides. The synthetic utility of this approach was demonstrated by the selective reduction of amides bearing ester and nitrile groups.
- Kadyrov, Renat
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p. 170 - 172
(2017/12/26)
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- Mononuclear ruthenium complex and organic synthesis reaction using same
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A neutral or cationic mononuclear ruthenium divalent complex represented by formula (1) can actualize exceptional catalytic activity in at least one reaction among a hydrosilylation reaction, hydrogenation reaction, and carbonyl compound reduction reaction. (In the formula, R1-R6 each independently represent a hydrogen atom or an alkyl group, aryl group, aralkyl group, organooxy group, monoorganoamino group, diorganoamino group, monoorganophosphino group, diorganophosphino group, monoorganosilyl group, diorganosilyl group, triorganosilyl group, or organothio group optionally substituted by X; at least one pair comprising any of R1-R3 and any of R4-R6 together represents a crosslinkable substituent; X represents a halogen atom, organooxy group, monoorganoamino group, diorganoamino group, or organothio group; L each independently represent a two-electron ligand other than CO and thiourea ligands; two L may bond to each other; and m represents an integer of 3 or 4.)
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Page/Page column 47; 48
(2018/03/26)
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- SAPO-34 synthesized with n-butylamine as a template and its catalytic application in the methanol amination reaction
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SAPO-34 was synthesized with n-butylamine (BA) as a template for the first time. Crystallization temperature and initial Si amount were important factors leading to successful syntheses. Lamellar AlPO-kanemite tends to form as the major phase or as an impurity of SAPO-34 at lower crystallization temperatures, though a higher initial Si amount may offer a positive effect on the crystallization of SAPO-34 that mitigates the low temperature. Higher temperature (240 °C) can effectively suppress the generation of lamellar materials and allow the synthesis of pure SAPO-34 with a wider range of Si incorporation. The crystallization processes at 200 and 240 °C were investigated and compared. We used the aminothermal method to synthesize SAPO-34-BA at 240 °C and also found n-propylamine is a suitable template for the synthesis of SAPO-34. The SAPO-34-BA products were characterized by many techniques. SAPO-34-BA has good thermal stability, crystallinity and porosity. BA remained intact in the crystals with ~1.8 BA molecule per chabazite cage. The catalytic performance of SAPO-34 was tested in the methanol amination reaction, which showed high methanol conversion and selectivity for methylamine plus dimethylamine under the conditions investigated, suggesting that this material is a good candidate for the synthesis of methylamines.
- Qiao, Yuyan,Wu, Pengfei,Xiang, Xiao,Yang, Miao,Wang, Quanyi,Tian, Peng,Liu, Zhongmin
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p. 574 - 582
(2017/04/04)
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- Halogenated closo-Dodecaborate Anions Stabilize Weakly Bound [(Me3NH)3X]2+ (X = Cl, Br) Dications in the Solid State
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Cocrystallization of [Me3NH]2[B12Y12] (Y = Cl, Br, I) with 1 equiv. of [Me3NH]X (X = Cl, Br) from acetonitrile/diethyl ether solution produced large colorless single crystals of [(Me3NH)3X][B12Y12]. Four different compounds of this type were prepared and structurally characterized. The compounds consist of weakly coordinating perhalogenated closo-dodecaborate [B12Y12]2– dianions and unprecedented weakly bound discrete [(Me3NH)3X]2+ dications. The [(Me3NH)3X]2+ dications are built up from a central halide anion and three [Me3NH]+ cations bound by N–H···X hydrogen bonds. The cations have a pyramidal structure, as determined by X-ray diffraction, which is in contrast to quantum-chemical calculations, which predict a trigonal-planar structure. While the [(Me3NH)3Cl]2+ and [(Me3NH)3Br]2+ cations were easily prepared, attempts to synthesize the corresponding [(Me3NH)3F]2+ and [(Me3NH)3I]2+ cations failed. Three further crystal structures containing the angulated [(Me3NH)2X]+ cation stabilized by [B12Cl12]2–, [B12Br12]2–, or [Me3NB12Cl11]– are reported as well.
- Bolli, Christoph,Derendorf, Janis,Jenne, Carsten,Ke?ler, Mathias
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supporting information
p. 4552 - 4558
(2017/10/25)
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- METHOD FOR THE SYNTHESIS OF TRIMETHYLAMINE
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A method for the synthesis of trimethylamine, involving the hydrogenation of a C1 precursor compound in the presence of ammonia and/or an ammonia salt and in the presence of a Ruthenium-Phosphine-complex
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Page/Page column 8-9
(2017/07/14)
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- DMF-activated chlorosilane chemistry: Molybdenum-catalyzed reactions of R3SiH, DMF and R′3SiCl to initially form R′3SiOSiR′3 and R3SiCl
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The room temperature reactions between R3SiH (R3?=?Et3, PhMe2, Ph2Me) and R′3SiCl (R′3?=?Me3, PhMe2, Ph2Me), with an excess of dimethylformamide (DMF) in the presence of (Me3N)Mo(CO)5 as a catalyst, result in the initial formation of R3SiCl, R′3SiOSiR′3 and Me3N as detected by 29Si, 13C, 1H NMR spectroscopy and GC/MS. As the reaction proceeds, the more so if the reaction temperature is raised, mixed disiloxanes R3SiOSiR′3 and ultimately lesser amounts of R3SiOSiR3 may be detected. A mechanism involving the activation of chlorosilanes by the nucleophilic DMF is proposed to produce transient imminium siloxy ion pairs, [Me2N[dbnd]CHCl]+[R′3SiO]? ? [Me2N[dbnd]CH(OSiR′3)]+Cl? which react with R3SiH to form Me2NCH2OSiR′3 and R3SiCl. A secondary reaction of Me2NCH2OSiR′3 with R′3SiCl produces the symmetrical disiloxane R′3SiOSiR′3 and ClCH2NMe2. The final stage of the reaction is the reduction of ClCH2NMe2 by R3SiH, a reaction which is reported for the first time. The newly created chlorosilane R3SiCl can become involved in the initial DMF activation chemistry thereby forming the other disiloxanes observed as the reaction proceeds.
- Gonzalez, Paulina E.,Sharma, Hemant K.,Pannell, Keith H.
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p. 376 - 381
(2017/06/30)
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- Selective Synthesis of Trimethylamine by Catalytic N-Methylation of Ammonia and Ammonium Chloride by utilizing Carbon Dioxide and Molecular Hydrogen
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The synthesis of trimethylamine (TMA) through a multicomponent combination of ammonia with carbon dioxide and molecular hydrogen by using a homogeneous ruthenium catalyst was explored. The use of [Ru(triphos)(tmm)] [triphos: 1,1,1-tris(diphenylphosphinomethyl)ethane, tmm: trimethylene methane] together with aluminum trifluoromethanesulfonate as a co-catalyst resulted in high ammonia conversion and excellent selectivity for TMA in organic solvents. Aqueous solutions of ammonium chloride were methylated almost quantitatively to the corresponding hydrochloride salt (i.e., TMA·HCl) in a biphasic solvent system by using the same Ru complex without the need for any co-catalyst.
- Beydoun, Kassem,Thenert, Katharina,Streng, Emilia S.,Brosinski, Sandra,Leitner, Walter,Klankermayer, Jürgen
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p. 135 - 138
(2016/01/26)
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- Chemoselective Reduction of Tertiary Amides to Amines Catalyzed by Triphenylborane
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Triphenylborane (BPh3) was found to catalyze the reduction of tertiary amides with hydrosilanes to give amines under mild condition with high chemoselectivity in the presence of ketones, esters, and imines. N,N-Dimethylacrylamide was reduced to provide the α-silyl amide. Preliminary studies indicate that the hydrosilylation catalyzed by BPh3may be mechanistically different from that catalyzed by the more electrophilic B(C6F5)3.
- Mukherjee, Debabrata,Shirase, Satoru,Mashima, Kazushi,Okuda, Jun
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supporting information
p. 13326 - 13329
(2016/10/30)
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- N-Alkyl Interstitial Spacers and Terminal Pendants Influence the Alkaline Stability of Tetraalkylammonium Cations for Anion Exchange Membrane Fuel Cells
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Current performance targets for anion exchange membrane (AEM) fuel cells call for greater than 95% alkaline stability for 5000 h at temperatures of up to 120 °C. Using this target temperature of 120 °C, we provide an incisive 1H nuclear magnetic resonance-based alkaline degradation method to identify the degradation products of n-alkyl spacer tetraalkylammonium cations in various AEM polymers and small molecule analogues. The operative alkaline degradation mechanisms and rates on benzyltrimethylammonium-, n-alkyl interstitial spacer-, and n-alkyl terminal chain-cations are compared in several architectures. Our findings indicate that benzyltrimethylammonium and n-alkyl terminal pendant cations are significantly more labile than an n-alkyl interstitial spacer cation. Additionally, we found that the alkaline stability of an n-alkyl interstitial spacer cation is enhanced when it is combined with an n-alkyl terminal pendant. At 120 °C, an inverse trend was observed in the overall stability of AEM poly(styrene) and AEM poly(phenylene oxide) samples compared to what has been shown at 80 °C. Follow-up small molecule studies suggest that at 120 °C, a 1,4-elimination degradation mechanism may be activated on styrenic AEM polymers capable of forming hyperconjugated resonance hybrids.
- Nu?ez, Sean A.,Capparelli, Clara,Hickner, Michael A.
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p. 2589 - 2598
(2016/06/01)
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- Proton-Coupled Reduction of an Iron Cyanide Complex to Methane and Ammonia
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Nitrogenase enzymes mediate the six-electron reductive cleavage of cyanide to CH4and NH3. Herein we demonstrate for the first time the liberation of CH4and NH3from a well-defined iron cyanide coordination complex, [SiPiPr3]Fe(CN) (where [SiPiPr3] represents a tris(phosphine)silyl ligand), on exposure to proton and electron equivalents. [SiPiPr3]Fe(CN) additionally serves as a useful entry point to rare examples of terminally-bound Fe(CNH) and Fe(CNH2) species that, in accord with preliminary mechanistic studies, are plausible intermediates of the cyanide reductive protonation to generate CH4and NH3. Comparative studies with a related [SiPiPr3]Fe(CNMe2) complex suggests the possibility of multiple, competing mechanisms for cyanide activation and reduction.
- Rittle, Jonathan,Peters, Jonas C.
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p. 12262 - 12265
(2016/10/13)
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- Mild partial deoxygenation of esters catalyzed by an oxazolinylborate-coordinated rhodium silylene
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An electrophilic, coordinatively unsaturated rhodium complex supported by borate-linked oxazoline, oxazoline-coordinated silylene, and N-heterocyclic carbene donors [{κ3-N,Si,C-PhB(OxMe2)(OxMe2SiHPh)ImMes}Rh(H)CO][HB(C6F5)3] (2, OxMe2 = 4,4-dimethyl-2-oxazoline; ImMes = 1-mesitylimidazole) is synthesized from the neutral rhodium silyl {PhB(OxMe2)2ImMes}RhH(SiH2Ph)CO (1) and B(C6F5)3. The unusual oxazoline-coordinated silylene structure in 2 is proposed to form by rearrangement of an unobserved isomeric cationic rhodium silylene species [{PhB(OxMe2)2ImMes}RhH(SiHPh)CO][HB(C6F5)3] generated by H abstraction. Complex 2 catalyzes reductions of organic carbonyl compounds with silanes to give hydrosilylation products or deoxygenation products. The pathway to these reactions is primarily influenced by the degree of substitution of the organosilane. Reactions with primary silanes give deoxygenation of esters to ethers, amides to amines, and ketones and aldehydes to hydrocarbons, whereas tertiary silanes react to give 1,2-hydrosilylation of the carbonyl functionality. In contrast, the strong Lewis acid B(C6F5)3 catalyzes the complete deoxygenation of carbonyl compounds to hydrocarbons with PhSiH3 as the reducing agent.
- Xu, Songchen,Boschen, Jeffery S.,Biswas, Abhranil,Kobayashi, Takeshi,Pruski, Marek,Windus, Theresa L.,Sadow, Aaron D.
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supporting information
p. 15897 - 15904
(2015/09/15)
-
- Tandem amine and ruthenium-catalyzed hydrogenation of CO2to methanol
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This Communication describes the hydrogenation of carbon dioxide to methanol via tandem catalysis with dimethylamine and a homogeneous ruthenium complex. Unlike previous examples with homogeneous catalysts, this CO2-to-CH3OH process proceeds under basic reaction conditions. The dimethylamine is proposed to play a dual role in this system. It reacts directly with CO2 to produce dimethylammonium dimethylcarbamate, and it also intercepts the intermediate formic acid to generate dimethylformamide. With the appropriate selection of catalyst and reaction conditions, >95% conversion of CO2 was achieved to form a mixture of CH3OH and dimethylformamide.
- Rezayee, Nomaan M.,Huff, Chelsea A.,Sanford, Melanie S.
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supporting information
p. 1028 - 1031
(2015/02/05)
-
- Supramolecular Ga4L612- cage photosensitizes 1,3-rearrangement of encapsulated guest via photoinduced electron transfer
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The K12Ga4L6 supramolecular cage is photoactive and enables an unprecedented photoreaction not observed in bulk solution. Ga4L612- cages photosensitize the 1,3-rearrangement of encapsulated cinnamylammonium cation guests from the linear isomer to the higher energy branched isomer when irradiated with UVA light. The rearrangement requires light and guest encapsulation to occur. The Ga4L612- cage-mediated reaction mechanism was investigated by UV/vis absorption, fluorescence, ultrafast transient absorption, and electrochemical experiments. The results support a photoinduced electron transfer mechanism for the 1,3-rearrangement, in which the Ga4L612- cage absorbs photons and transfers an electron to the encapsulated cinnamylammonium ion, which undergoes C-N bond cleavage, followed by back electron transfer to the cage and recombination of the guest fragments to form the higher energy isomer.
- Dalton, Derek M.,Ellis, Scott R.,Nichols, Eva M.,Mathies, Richard A.,Dean Toste,Bergman, Robert G.,Raymond, Kenneth N.
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supporting information
p. 10128 - 10131
(2015/09/01)
-
- Early main group metal catalysis: How important is the metal?
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Organocalcium compounds have been reported as efficient catalysts for various alkene transformations. In contrast to transition metal catalysis, the alkenes are not activated by metal-alkene orbital interactions. Instead it is proposed that alkene activation proceeds through an electrostatic interaction with a Lewis acidic Ca2+. The role of the metal was evaluated by a study using the metal-free catalysts: [Ph2N-Me4N+] and [Ph3C-][Me4N- ]. These "naked" amides and carbanions can act as catalysts in the conversion of activated double bonds (C=O and C=N) in the hydroamination of Ar-N=C=O and R-N=C=N=R (R=alkyl) by Ph2NH. For the intramolecular hydroamination of unactivated C=C bonds in H2C=CHCH2CPh2CH2NH2 the presence of a metal cation is crucial. A new type of hybrid catalyst consisting of a strong organic Schwesinger base and a simple metal salt can act as catalyst for the intramolecular alkene hydroamination. The influence of the cation in catalysis is further evaluated by a DFT study.
- Harder, Sjoerd,Penafiel, Johanne,Maron, Laurent
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supporting information
p. 201 - 206
(2015/09/08)
-
- Free-radical polymerization of itaconic acid in the presence of choline salts: Mechanism of persulfate decomposition
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Kinetics of decomposition of persulfate activated by choline in aqueous solution has been studied. Additionally, the products of choline degradation were analyzed by 1H NMR spectroscopy, and betaine aldehyde was identified as the main oxidation product. Thus, radical-chain redox mechanism is postulated to explain experimental results. The mechanism was successfully verified using kinetic modeling approach. Moreover, it was found that due to formation of complex of itaconic acid and choline chloride, the salt solubility of the acid in water was increased. Finally, free-radical polymerization of itaconic acid initiated by persulfate in aqueous solution of the choline salt yielded poly(itaconic acid) with higher molecular weight and increased polydispersity.
- Bednarz, Szczepan,B?aszczyk, Alicja,B?azejewska, Diana,Bogda?, Dariusz
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p. 297 - 304
(2015/02/19)
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- NANOPARTICLES BASED ON A GAG AND A SQUALENE
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The present invention relates to nanoparticles comprising at least one negatively charged glycosaminoglycan-type macromolecule or a derivative thereof, non-covalently coupled to at least one molecule of a cationic hydrocarbon-based radical of squalene nature represented by the formula (I) which follows: (I) wherein: A, B, C, D, E and F are a hydrogen atom or a methyl group; Z and Y represent a radical (formula (II)), an ethyltrialkylammonium radical, an ethylguanidium radical or a 1-[ethylideneamino]guanidinium radical with the proviso that at least one of Z and Y is different from (formula (II)), the symbol * showing the position of the attachment of the radical to the structure; and n is equal to 1 or 2. The present invention also relates to a method for preparing said nanoparticles, and to a lyophilisate, a solid dosage form and pharmaceutical or dermatological compositions comprising said nanoparticles. Said nanoparticles are useful as medicines and more particularly as anticoagulant agents.
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Page/Page column 23; 24
(2014/07/07)
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- Electrochemical degradation of butyltrimethylammonium bis(trifluoromethylsulfonyl)imide for lithium battery applications
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Ionic liquids (ILs) are being considered as electrolytes for lithium ion batteries due to their low volatility, high thermal stability, and wide electrochemical windows which are stable at the strongly reducing potentials present in Li/Li+ batteries. Lithium metal deposition occurs under strongly reducing conditions and the effect that Li metal and any overpotential has on the stability of ILs is important in furthering the application of ILs in lithium based batteries. Here, N-butyl-N-trimethylammonium bis(trifluoromethylsulfonyl)imide was exposed to various potential differences in order to collect and characterize the volatile products. The IL produced more volatile products when exposed to strong reducing potentials which included reactive products such as hydrogen, alkanes, and amines. Water is a known contributor to hydrogen production in reducing environments, but the IL is also a source of hydrogen. If Li+ was present, the preferred pathway of reduction was plating of the lithium onto the working electrode, thus decreasing the reaction rate of degraded ILs.
- Klug, Christopher L.,Bridges, Nicholas J.,Visser, Ann E.,Crump, Stephen L.,Villa-Aleman, Eliel
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p. 3879 - 3884
(2014/08/05)
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- Carbonylation of quaternary ammonium salts to tertiary amides using NaCo(CO)4 catalyst
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We reported here the catalytic carbonylation of quaternary ammonium salts under anhydrous condition. Quaternary ammonium salts, a kind of versatile reagents that were widely used in organometallic chemistry, can be carbonylated to tertiary amides by an in situ prepared NaCo(CO)4 catalyst. It was found that the counterions (Cl-, Br-, I-, OTf-) in the quaternary ammonium salts played a significant role in the reaction and tetramethylammonium iodide could give high yield (96%) of N,N-dimethylacetamide (DMAc) with only 0.5 mol% cobalt catalyst. Under optimum conditions, several other quaternary ammonium iodides were also carbonylated to corresponding tertiary amides in moderate to excellent yields. Obviously, these results also give us a special apprehension that Me4NI and other quaternary ammonium salts could be possibly carbonylated to tertiary amides in the carbonylation reaction where they are used as promoters or solvents in most cases. Considering the high activity and moderate to excellent selectivity, this process could be a potential method for the synthesis of certain tertiary amides. Moreover, the cleaving mechanism of CN bonds and the possible catalytic intermediates were discussed in detail.
- Lei, Yizhu,Zhang, Rui,Wu, Qing,Mei, Hui,Xiao, Bo,Li, Guangxing
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p. 120 - 125
(2013/12/04)
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- Tungsten nitrido complexes as precursors for low temperature chemical vapor deposition of WNxCy films as diffusion barriers for Cu metallization
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Tungsten nitrido complexes of the form WN(NR2)3 [R = combinations of Me, Et, iPr, nPr] have been synthesized as precursors for the chemical vapor deposition of WNxCy, a material of interest for diffusion barriers in Cu-metallized integrated circuits. These precursors bear a fully nitrogen coordinated ligand environment and a nitrido moiety (Wi - N) designed to minimize the temperature required for film deposition. Mass spectrometry and solid state thermolysis of the precursors generated common fragments by loss of free dialkylamines from monomeric and dimeric tungsten species. DFT calculations on WN(NMe 2)3 indicated the lowest gas phase energy pathway for loss of HNMe2 to be β-H transfer following formation of a nitrido bridged dimer. Amorphous films of WNxCy were grown from WN(NMe2)3 as a single source precursor at temperatures ranging from 125 to 650 C using aerosol-assisted chemical vapor deposition (AACVD) with pyridine as the solvent. Films with stoichiometry approaching W2NC were grown between 150 and 450 C, and films grown at 150 C were highly smooth, with a RMS roughness of 0.5 nm. In diffusion barrier tests, 30 nm of film withstood Cu penetration when annealed at 500 C for 30 min.
- McClain, K. Randall,O'Donohue, Christopher,Koley, Arijit,Bonsu, Richard O.,Abboud, Khalil A.,Revelli, Joseph C.,Anderson, Timothy J.,McElwee-White, Lisa
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supporting information
p. 1650 - 1662
(2014/02/14)
-
- Experimental and theoretical study of the kinetic of proton transfer reaction by ion mobility spectrometry
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Rate constants of the proton transfer reactions RH+ + DMP → R + DMP·H+, where R was acetone (Ac), trimethyl amine (TMA) or H2O and DMP was 2,4-dimethyl pyridine have been measured by ion mobility spectrometry (IMS). The Reactant R was injected into the ionization region of IMS to produce RH+ while DMP was continuously delivered to the drift region to react with the RH+ pulsed into the drift tube by a shutter grid. Since DMP.H+ was generated along the drift tube, a tail appeared in the IMS spectrum that contained kinetic information. To prevent proton-bound dimer formation, the reactions were carried out at elevated temperatures (170-230 °C). We measured rate constants of 1.17 × 10-9, 0.90 × 10-9 and 0.68 × 10-9 cm3 s-1 for proton transfer from H3O +, Ac·H+ and TMA·H+ to DMP, respectively. The experimental rate constants were almost temperature independent, indicating that no activation energy was involved in those proton transfer reactions. The rate constants were also calculated by using average dipole orientation (ADO) theory at B3LYP and MP2 levels. The calculated values revealed acceptable agreement between the experimental and theoretical trends. 2014 Elsevier B.V.
- Valadbeigi,Farrokhpour,Rouholahnejad,Tabrizchi
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p. 105 - 111
(2014/07/22)
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- CO2 as a C1-building block for the catalytic methylation of amines
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A novel catalytic reaction has been designed to utilize, for the first time, CO2 as a C1 feedstock in the synthesis of N-methylamines. Simple zinc catalysts, based on commercially available zinc salts and ligands, prove highly efficient in promoting both a 6 electron reduction of carbon dioxide and the formation of a C-N bond, using hydrosilanes and amines.
- Jacquet, Olivier,Frogneux, Xavier,Das Neves Gomes, Christophe,Cantat, Thibault
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p. 2127 - 2131
(2013/05/21)
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- (Me3N)Mo(CO)5-catalyzed reduction of DMF by disiloxane and disilane moieties: Fate of the silicon-containing fragments
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The use of HSiMe2OSiMe2H (1) and various hydrodisilanes, R3SiSiMe2H (2; R = alkyl, aryl), as reductants for N,N-dimethylformamide (DMF) in the presence of (Me 3N)Mo(CO)5 as a catalyst led to the formation of a series of novel and structurally interesting siloxanes as well as trimethylamine. In the case of 1 the cyclic poly(dimethylsiloxanes) D4 and D6 are obtained, and for 2 the products are bis(disilyl) ethers, (R 3SiSiMe2)2O. Siloxymethylamine intermediates resulting from an initial hydrosilylation of DMF, (Me2NCH 2OSiMe2)2O (3) and R3SiSiMe 2OCH2NMe2 (4; R = Me, Ph), from the reactions of 1 and 2, respectively, can be observed and, in the case of 3, isolated and purified. In the presence of the respective starting silanes and the catalyst the intermediates readily react to form the appropriate siloxane materials and trimethylamine. Compound 3 was functionalized by reaction with R3ECl (E = Si, Ge, R = Me, Ph) to provide group 14 containing products (R 3EOSiMe2)2O (R = Me, E = Si (5a), Ge (6a); R = Ph, E = Si (5b), Ge (6b)). Reactions of Me3SiSiMe2OCH 2NMe2 (4a) with R3ECl produced Me 3SiSiMe2OER3 (R = Me, E = Si (7), R = Ph, E = Ge, 8). The crystal structure of (Ph3SiSiMe2)2O (9c) is reported and exhibits an Si-O-Si angle of 165 and the longest Si-Si bond length (2.376(2) A) for such bis(disilyl) ethers. The new (Ph 3EOSiMe2)2O derivatives 5b and 6b have been structurally characterized and exhibit distinct conformations about the central SiOSi fragment. In the case of the Ph3Si compound 5b the dihedral angle between the two end groups is 180 with completely staggered SiMe groups on the central Si atoms, whereas for the Ge congener it is 55.7 and the structure exhibits eclipsed SiMe groups. The distinction seems to be due to both intra- and intermolecular phenyl group π stacking in 6b stabilizing this formally higher energy conformation.
- Sharma, Hemant K.,Arias-Ugarte, Renzo,Tomlinson, David,Gappa, Rie,Metta-Magana, Alejandro J.,Ito, Haruhiko,Pannell, Keith H.
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p. 3788 - 3794
(2013/08/23)
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- AN EFFICIENT CONTINUOUS PROCESS FOR MANUFACTURING OF 4-AMINODIPHENYLAMINE FROM ANILINE AND NITROBENZENE
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An efficient continuous manufacturing process for 4-aminodiphenylamine by coupling aniline with nitrobenzene in the presence of tetramethylammonium hydroxide (TMAH) as a base, using flow reactors wherein base decomposition is considerably reduced by optimizing base quantity, process conditions and process equipment. Accordingly, in brief summary, one embodiment of the present invention is a process which comprises one or more of the steps of reacting aniline and nitrobenzene in the presence of water and TMAH as a base, in a continuous manner by feeding the reactants to a series of continuous flow reactors, while continuously distilling off an aniline-water mixture under, reduced pressure such that the water to total base molar ratio is less than 0.6:1 at the flow reactors outlet, and the water to unbound TMAH molar ratio is about 4: 1 in the reaction product.
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Page/Page column 25-26
(2013/11/05)
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- Homobimetallic rhodium NHC complexes as versatile catalysts for hydrosilylation of a multitude of substrates in the presence of ambient air
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Two recently reported air- and water-stable di-Rh complexes based on 1,3-bis(3′-butylbenzimidazol-2′-ylidene)benzene were utilized as catalysts for hydrosilylation. Among the substrates investigated were aldehydes, ketones, α,β-unsaturated carbonyls, acyl chlorides, nitriles, alkenes, nitro groups, isocyanates, and tertiary amides. Additionally, carbon dioxide underwent hydrosilylation to produce dimethylphenylsilylformate. The catalysts compared well to other previously reported hydrosilylation catalysts, and the Rh-Cl catalyst was found to be faster and more selective than the Rh-I complex in each case.
- Huckaba, Aron J.,Hollis, T. Keith,Reilly, Sean W.
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p. 6248 - 6256
(2013/12/04)
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- Towards mesostructured zinc imidazolate frameworks
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The transfer of supramolecular templating to the realm of metal-organic frameworks opens up new avenues to the design of novel hierarchically structured materials. We demonstrate the first synthesis of mesostructured zinc imidazolates in the presence of the cationic surfactant cetyltrimethylammonium bromide (CTAB), which acts as a template giving rise to ordered lamellar hybrid materials. A high degree of order spanning the atomic and mesoscale was ascertained by powder X-ray diffraction, electron diffraction, as well as solid-state NMR and IR spectroscopy. The metrics of the unit cells obtained for the zinc methylimidazolate and imidazolate species are a=(11.43±0.45), b=(9.55±0.35), c=(27.19±0.34)A, and a=(10.98±0.90), b=(8.95±0.95), c=(26.33±0.34)A, respectively, assuming orthorhombic symmetry. The derived structure model is consistent with a mesolamellar structure composed of bromine-terminated zinc (methyl)imidazolate chains interleaved with motionally rigid cationic surfactant molecules in an all-trans conformation. The hybrid materials exhibit unusually high thermal stability up to 300°C, at which point CTAB is lost and evidence for a thermally induced transformation into poorly crystalline mesostructures with larger feature sizes is obtained. Treatment with ethanol effects the extraction of CTAB from the material, followed by facile transformation into pure microporous ZIF-8 nanoparticles within minutes, thus demonstrating a unique transition from a mesostructure into a microporous zinc imidazolate.
- Junggeburth, Sebastian C.,Schwinghammer, Katharina,Virdi, Kulpreet S.,Scheu, Christina,Lotsch, Bettina V.
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body text
p. 2143 - 2152
(2012/03/26)
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- Bulk gold-catalyzed oxidations of amines and benzyl alcohol using amine N-oxides as oxidants
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Bulk gold powder (~50 μm) catalyzes the oxidative dehydrogenation of amines to give imines using amine N-oxides (R3N-O) as the oxidant. The reaction of dibenzylamine (PhCH2-NH-CH2Ph) with N-methylmorpholine N-oxide (NMMO) in the presence of gold powder at 60 °C produced N-benzylidenebenzylamine (PhCH=N-CH2Ph) in 96% yield within 24 h. Benzyl alcohol was oxidized by NMMO to benzaldehyde in >60% yield in the presence of gold powder. Although O2 was previously shown to oxidize amines in the presence of bulk gold, it is surprising that gold is also capable of catalyzing the oxidation of amines using amine oxides, which are chemically so different from O2. Graphical Abstract: [Figure not available: see fulltext.]
- Klobukowski, Erik R.,Angelici, Robert J.,Woo, L. Keith
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experimental part
p. 161 - 167
(2012/04/10)
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