- An effective medium of H2O and low-pressure CO2 for the selective hydrogenation of aromatic nitro compounds to anilines
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Chemoselective hydrogenation of water-insoluble aromatic nitro compounds can be achieved over Ni catalysts in a H2O-compressed CO2 system at 35-50 °C without using any environmentally harmful solvent. The effective CO2 pressure is much lower than the critical pressure of CO2. The hydrogenation of nitro group should be the rate-determining step. The Royal Society of Chemistry.
- Meng, Xiangchun,Cheng, Haiyang,Fujita, Shin-Ichiro,Yu, Yancun,Zhao, Fengyu,Arai, Masahiko
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- Ethylenediamine-assisted solvothermal synthesis of one-dimensional Cd xZn(1-x)S solid solutions and their photocatalytic activity for nitrobenzene reduction
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A series of one-dimensional CdxZn(1-x)S semiconductor alloys were prepared via a hydrothermal method with the assistance of ethylenediamine at 180 °C for 12 h. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption/desorption and Fourier transform infrared techniques. With the value of x increased, the band gap of CdxZn(1-x)S semiconductor alloys gradually decreased indicating that catalysts were exchanged to visible-light response. Photocatalytic reduction results showed that Cd0.73Zn0.27S exhibited the highest photocatalytic activity toward photo production of aniline via nitrobenzene reduction under visible irradiation respectively. The reaction mechanism was also discussed.
- Wei, Hongwei,Jiang, Hechun,Zheng, Zhen,Zhao, Quanqin,Wu, Qingyin,Zhan, Jinhua
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- Dimeric assemblies of lanthanide-stabilised dilacunary Keggin tungstogermanates: A new class of catalysts for the selective oxidation of aniline
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In this work we demonstrate the efficiency of some dimeric [Ln4(H2O)6(β-GeW10O38)2]12- anions composed of lanthanide-stabilised dilacunary Keggin tungstogermanate fragments (ββ-Ln4, Ln = Dy, Ho, Er, Tm) as heterogeneous catalysts for the organic phase oxidation of aniline with hydrogen peroxide. The results obtained evidence total conversion of aniline at room temperature, as well as full selectivity towards nitrosobenzene, and the catalysts are able to retain both their activity and selectivity after several runs. Peroxopolyoxometalate intermediaries have been identified as the catalytically active species during the aniline-to-nitrosobenzene oxidation process.
- Trautwein, Guido,El Bakkali, Bouchra,Alca?iz-Monge, Juan,Artetxe, Be?at,Reinoso, Santiago,Gutiérrez-Zorrilla, Juan M.
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- One-pot synthesis of aluminum oxyhydroxide matrix-entrapped Pt nanoparticles as an excellent catalyst for the hydrogenation of nitrobenzene
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Aluminum oxyhydroxide matrix-entrapped Pt nanoparticles (Pt/AlO(OH)) were synthesized via a one-pot procedure, by the reduction of Pt4+ followed by the hydrolysis of Al(O-sec-Bu)3. Small and well-dispersed Pt nanoparticles were entrapped into an aluminum oxyhydroxide matrix and confirmed by TEM characterization. FTIR analysis indicated that the Pt/AlO(OH) catalyst had a large amount of surface hydroxyl groups, which potentially improves its dispersibilty in aqueous solution. The as-prepared catalyst was used for the hydrogenation of nitrobenzene to aniline at 30 °C and atmospheric hydrogen pressure. Compared with other alcohol-water media, the hydrogenation reaction in a methanol-water medium exhibited a maximum turnover frequency (TOF) of 3620 h-1. A complete conversion of nitrobenzene with a selectivity of 99.0% was obtained with an increase of time to 150 min.
- Fan, Guangyin,Wang, Yinhu,Wang, Chenyu
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- Fabrication of hybrid mesoporous TiO2-SiO2(Et) supported Ni nanoparticles: An efficient and air/water stable catalyst
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We prepared a series of mesostructured Ni/TiO2-SiO2(Et) hybrid catalysts with highly dispersed Ni nanoparticles and incorporated ethane-bridged organosilica moieties. Ni/TiO2-SiO2(Et) showed high activity in the hydrogenation of nitrobenzene in water, and it could be recycled for several times with a constant activity and selectivity. It was confirmed that Ni/TiO2-SiO2(Et) catalyst is of hydrophobicity as the ethane-bridged organosilica fragments were incorporated into the mesoporous framework, and so the Ni active species was protected without contacting with water to form the inactive Ni species. In particularly, the Ni/TiO2-SiO2(Et) catalyst was air-stable, it could remain good activity after being exposed to air for a week. Accordingly, this work developed a kind of hydrophobic Ni catalyst with high stability to water and air, which is expected to have a wide application in the hydrogenation reactions.
- Li, Wei,Cheng, Haiyang,Lin, Weiwei,Liang, Guanfeng,Zhang, Chao,Zhao, Fengyu
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- Radical Cations of Nitroso Derivatives. A Radiation-chemical and Electron Spin Resonance Study
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Exposure of dilute solutions containing nitrosobenzene in trichlorofluoromethane to 60Co γ-rays at 77 K gave the corresponding radical cation, characterised by e.s.r. spectroscopy.The results confirm the interpretation of liquid-phase data assigned to this cation, which showed that loss is from an in-plane ?-orbital localised on nitrogen and oxygen, rather than from the aromatic ?-system.However, solutions containing the t-butyl derivative in equilibrium with its dimer, (Me3CNO)2, gave primarily the dimer cation, (Me3CNO)2+, with possible traces of the monomer cation.The e.s.r. data for the latter resemble those for the nitrosobenzene cation, whereas results for the dimer cation suggest that loss is from a ?-type orbital with very low spin density on the two equivalent nitrogen atoms.
- Chandra, Harish,Keeble, David J.,Symons, Martyn C. R.
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- Kinetics and mechanism of the enhanced reductive degradation of nitrobenzene by elemental iron in the presence of ultrasound
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The degradation of nitrobenzene (NB) and aniline (AN) were facilitated by using sonolysis, reduction by Fe0 and a combination of the two processes. The rates of NB reduction by Fe0 increased in the presence of ultrasound. The first-order rate constant for NB degradation by ultrasound was 1.8 x 10-3/min. The rate was considerably faster in the presence of Fe0. The similar degradation rates for AN in each system indicated that the sonication process was unaffected by the presence of Fe0. The rate enhancements for the NB degradation can be explained chiefly by the continuous cleaning and chemical activation of the Fe0 surfaces by acoustic cavitation and to accelerated mass transport rates of reactants, intermediates and products between the solution phase and the Fe0 surface. The relative concentrations of nitrosobenzene and AN, the main reaction intermediates produced by Fe0 reduction, were significantly changed in the presence of ultrasound.
- Hoffmann,Hung,Ling
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- Continuous proline catalysis via leaching of solid proline
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Herein, we demonstrate that a homogeneous catalyst can be prepared continuously via reaction with a packed-bed of a catalyst precursor. Specifically, we perform continuous proline catalyzed α-aminoxylations using a packed-bed of L-proline. The system relies on a multistep sequence in which an aldehyde and thiourea additive are passed through a column of solid proline, presumably forming a soluble oxazolidinone intermediate. This transports a catalytic amount of proline from the packed-bed into the reactor coil for subsequent combination with a solution of nitrosobenzene, affording the desired optically active α-aminooxy alcohol after reduction. To our knowledge, this is the first example in which a homogeneous catalyst is produced continuously using a packedbed. We predict that the method will not only be useful for other L-proline catalyzed reactions, but we also foresee that it could be used to produce other catalytic species in flow.
- Opalka, Suzanne M.,Longstreet, Ashley R.,Tyler McQuade
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- Catalytic Teflon AF-2400 membrane reactor with adsorbed ex situ synthesized Pd-based nanoparticles for nitrobenzene hydrogenation
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Among the unconventional approaches of supporting catalyst nanoparticles, the layer-by-layer assembly of polyelectrolyte multilayers for nanoparticle adsorption represents an easy and convenient method. It enables the deposition of singularly adsorbed nanoparticles and prevents them from aggregating. In this work, polydopamine was grafted onto the internal surface of a Teflon AF-2400 tubular membrane, known for its excellent permeability to light gases and inertness to chemicals. Poly(acrylic acid) and poly(allylamine hydrochloride) were sequentially adsorbed onto the modified surface of the membrane. Ex situ synthesized spherical, cubical, truncated octahedral palladium or dendritic platinum-palladium nanoparticles were then incorporated. The catalytic membranes were assembled in a tube-in-tube configuration and tested over 6 h of continuous nitrobenzene hydrogenation with molecular hydrogen. Stable conversion was observed for the truncated octahedral and dendritic nanoparticles, while a progressive deactivation occurred for the other nanoparticles. Due to their small size, the 3.7 nm spherical nanoparticles exhibited the highest reaction rate, 629molreactant/(molcatalyst?h), while the cubical nanoparticles showed the highest turnover frequency, ～3000 h?1. The reactor concept developed in this work demonstrates how such a design can serve as a platform for conducting continuous multiphase catalytic reactions in flow using singularly adsorbed and finely tuned nanoparticles. The small volume of pressurized gas present in the tube-in-tube reactor offers improved process safety compared to a batch process, while the Teflon AF-2400 membrane provides control over the gas permeation during reaction.
- Venezia, Baldassarre,Panariello, Luca,Biri, Daniel,Shin, Juhun,Damilos, Spyridon,Radhakrishnan, Anand N.P.,Blackman, Chris,Gavriilidis, Asterios
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- The Active Sites of Manganese- and Cobalt-Containing Catalysts in the Selective Gas Phase Reduction of Nitrobenzene
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The active sites of the spinels Mn3O4 and Co3O4 in the selective reduction of nitrobenzene to nitrosobenzene have been investigated, by total and partial substitution of Mnn+ (Con+) ions in tetrahedral position and/or Mnn+ (Con+) ions in octahedral position by redox-inactive ions.Investigation of the catalytic activities of the totally substituted manganese spinel ZnMn2O4 and that of the totally substituted cobalt spinels CoAl2O4 and ZnCo2O4 showed that the manganese and cobalt ions in octahedral position were responsible for the activity of the reaction.MnAl2O4, however, also showed some activity for the selective reduction of nitrobenzene, which should be due to surface enrichment and/or oxidative transfer of manganese from tetrahedral sites to octahedral sites.XRD results of the partially substituted spinels MnxZn1-xAl2O4 showed that was a linear correlation between the manganese concentration expressed by x and the lattice constant.Morever, each sample showed segregation of Al2O3; again there was a linear correlation between x in certain series of MnxZn1-xAl2O4 and the amount of free Al2O3.This points to an oxidative transfer of manganese from tetrahedral sites to octahedral sites.XPS showed that the concentration of manganese in the surface layers corresponded roughly to the value x, but the concentration of zinc in the surface layers was much smaller than expected.The catalytic activities of the MnxZn1-xAl2O4 series of catalysts are larger than would be expected from the result on ZnMnO4 and ZnCo2O4.
- Maltha, A.,Kist, H. F.,Brunet, B.,Ziolkowski, J.,Onishi, H.,et al.
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- Preparation of aniline from photocatalytic reduction of nitrobenzene using Pt/Nd2O3 nanocomposite
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In this manuscript, a template method was used to synthesis Pt-doped Nd2O3 nanostructures with controlled Pt doping contents. The characterizations illustrated that the obtained samples have ultra high surface area (190 m2/g), high crystallinity, small grain size (20 nm) and hollow spherical like morphology. Also, the band gap of the Pt-doped Nd2O3 nanostructures can be controlled by controlling the Pt contents. The photocatalytic activity of the Pt-doped Nd2O3 nanostructures samples was studied by studying the reduction of nitrobenzene into aniline using visible light irradiation. The photocatalytic performance of Nd2O3 was enhanced by Pt doping. This can be attributed to the fact that the trapping effect of the Pt-doped Nd2O3 nanostructures and the red shift of absorption edge. The study result provides an effective method to create different photocatalysts with enhanced visible-light-driven photocatalytic performance.
- Mohamed
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- Continuous Flow Synthesis of Azoxybenzenes by Reductive Dimerization of Nitrosobenzenes with Gel-Bound Catalysts
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In the search for a new synthetic pathway for azoxybenzenes with different substitution patterns, an approach using a microfluidic reactor with gel-bound proline organocatalysts under continuous flow is presented. Herein the formation of differently substituted azoxybezenes by reductive dimerization of nitrosobenzenes within minutes at mild conditions in good to almost quantitative yields is described. The conversion within the microfluidic reactor is analyzed and used for optimizing and validating different parameters. The effects of the different functionalities on conversion, yield, and reaction times are analyzed in detail by NMR. The applicability of this reductive dimerization is demonstrated for a wide range of differently substituted nitrosobenzenes. The effects of these different functionalities on the structure of the obtained azoxyarenes are analyzed in detail by NMR and single-crystal X-ray diffraction. Based on these results, the turnover number and the turnover frequency were determined.
- Schmiegel, Carsten J.,Berg, Patrik,Obst, Franziska,Schoch, Roland,Appelhans, Dietmar,Kuckling, Dirk
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p. 1628 - 1636
(2021/03/15)
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- Azobioisosteres of Curcumin with Pronounced Activity against Amyloid Aggregation, Intracellular Oxidative Stress, and Neuroinflammation
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Many (poly-)phenolic natural products, for example, curcumin and taxifolin, have been studied for their activity against specific hallmarks of neurodegeneration, such as amyloid-β 42 (Aβ42) aggregation and neuroinflammation. Due to their drawbacks, arising from poor pharmacokinetics, rapid metabolism, and even instability in aqueous medium, the biological activity of azobenzene compounds carrying a pharmacophoric catechol group, which have been designed as bioisoteres of curcumin has been examined. Molecular simulations reveal the ability of these compounds to form a hydrophobic cluster with Aβ42, which adopts different folds, affecting the propensity to populate fibril-like conformations. Furthermore, the curcumin bioisosteres exceeded the parent compound in activity against Aβ42 aggregation inhibition, glutamate-induced intracellular oxidative stress in HT22 cells, and neuroinflammation in microglial BV-2 cells. The most active compound prevented apoptosis of HT22 cells at a concentration of 2.5 μm (83 % cell survival), whereas curcumin only showed very low protection at 10 μm (21 % cell survival).
- Hofmann, Julian,Ginex, Tiziana,Espargaró, Alba,Scheiner, Matthias,Gunesch, Sandra,Aragó, Marc,Stigloher, Christian,Sabaté, Raimon,Luque, F. Javier,Decker, Michael
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p. 6015 - 6027
(2021/03/16)
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- "Photo-Rimonabant": Synthesis and Biological Evaluation of Novel Photoswitchable Molecules Derived from Rimonabant Lead to a Highly Selective and Nanomolar " Cis-On" CB1R Antagonist
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Human cannabinoid receptor type 1 (hCB1R) plays important roles in the regulation of appetite and development of addictive behaviors. Herein, we describe the design, synthesis, photocharacterization, molecular docking, and in vitro characterization of "photo-rimonabant", i.e., azo-derivatives of the selective hCB1R antagonist SR1411716A (rimonabant). By applying azo-extension strategies, we yielded compound 16a, which shows marked affinity for CB1R (Ki (cis form) = 29 nM), whose potency increases by illumination with ultraviolet light (CB1R Kitrans/cis ratio = 15.3). Through radioligand binding, calcium mobilization, and cell luminescence assays, we established that 16a is highly selective for hCB1R over hCB2R. These selective antagonists can be valuable molecular tools for optical modulation of CBRs and better understanding of disorders associated with the endocannabinoid system.
- Rodríguez-Soacha, Diego A.,Fender, Julia,Ramírez, Yesid A.,Collado, Juan Antonio,Mu?oz, Eduardo,Maitra, Rangan,Sotriffer, Christoph,Lorenz, Kristina,Decker, Michael
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p. 1632 - 1647
(2021/05/10)
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- Rhodium(III)-catalyzed regioselective C–H nitrosation/annulation of unsymmetrical azobenzenes to synthesize benzotriazole N-oxides via a RhIII/RhIII redox-neutral pathway
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A Rh(III)-catalyzed regioselective C–H nitrosation/annulation reaction of unsymmetrical azobenzenes with [NO][BF4] has been developed to achieve high-yielding syntheses of benzotriazole N-oxides with excellent functional group tolerance. Computational studies have revealed that this oxidative C–H functionalization reaction involves an interesting redox-neutral Rh(III)/Rh(III) pathway without the change of Rh oxidation state.
- Zhang, Yuanfei,Chen, Zhe-Ning,Su, Weiping
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supporting information
(2021/05/19)
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- Understanding Mechanistic Differences between 3-Diazoindolin-2-Imines and N-Sulfonyl-1,2,3-Triazoles in the Rh2(II)-Catalyzed Reactions with Nitrosoarenes
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The employment of α-iminometallocarbenes to construct valuable N-containing compounds has attracted significant research interest. Herein, the nucleophilic addition of nitrosoarenes with the α-imino rhodium carbene species (I), which is derived from Rh2(II)-catalyzed denitrogenation of 3-diazoindolin-2-imines, to produce synthetically useful 2-iminoindolin-nitrones is described. Mechanistically, the N-attack of nitrosoarenes with the carbene site of I is proposed. For the analogous Rh2(II)-catalyzed reaction of nitrosoarenes with N-sulfonyl-1,2,3-triazoles reported by Li and co-workers (Org. Lett. 2014, 16, 6394), however, the O-attack of nitrosoarenes with the carbene site of α-imino rhodium carbene species (II) is more favorable to occur than the N-attack. The subsequent transformation to yield the product of N-acylamidines is rationalized based on computational studies. The mechanistic differences for the reactions of nitrosoarenes with α-imino rhodium carbene species I and II are discussed.
- Bao, Xiaoguang,Fu, Rui,Gao, Ke,Kou, Luyao,Zhou, Shaofang
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supporting information
p. 1565 - 1572
(2021/05/28)
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- Reversible Photoswitchable Inhibitors Generate Ultrasensitivity in Out-of-Equilibrium Enzymatic Reactions
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Ultrasensitivity is a ubiquitous emergent property of biochemical reaction networks. The design and construction of synthetic reaction networks exhibiting ultrasensitivity has been challenging, but would greatly expand the potential properties of life-like materials. Herein, we exploit a general and modular strategy to reversibly regulate the activity of enzymes using light and show how ultrasensitivity arises in simple out-of-equilibrium enzymatic systems upon incorporation of reversible photoswitchable inhibitors (PIs). Utilizing a chromophore/warhead strategy, PIs of the protease α-chymotrypsin were synthesized, which led to the discovery of inhibitors with large differences in inhibition constants (Ki) for the different photoisomers. A microfluidic flow setup was used to study enzymatic reactions under out-of-equilibrium conditions by continuous addition and removal of reagents. Upon irradiation of the continuously stirred tank reactor with different light pulse sequences, i.e., varying the pulse duration or frequency of UV and blue light irradiation, reversible switching between photoisomers resulted in ultrasensitive responses in enzymatic activity as well as frequency filtering of input signals. This general and modular strategy enables reversible and tunable control over the kinetic rates of individual enzyme-catalyzed reactions and makes a programmable linkage of enzymes to a wide range of network topologies feasible.
- Teders, Michael,Pogodaev, Aleksandr A.,Bojanov, Glenn,Huck, Wilhelm T. S.
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supporting information
p. 5709 - 5716
(2021/05/07)
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- Pyrazole amide compound containing azo structure as well as preparation and application of pyrazole amide compound
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The invention relates to a pyrazole amide compound containing an azo structure as well as preparation and application of the pyrazole amide compound. Specifically, the compound disclosed by the invention has a structure as shown in a formula I, and the definitions of all groups and substituent groups are described in the specification. The invention also discloses a preparation method of the compound and application of the compound in insecticidal, bactericidal and acaricidal aspects.
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Paragraph 0119; 0128-0130
(2021/10/20)
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- Ultrathin ZnTi-LDH nanosheets for photocatalytic aerobic oxidation of aniline based on coordination activation
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In this work, ZnTi-LDH nanosheets with several monolayer thickness were prepared as photocatalysts for the aerobic oxidation of aniline to yield nitrosobenzene under visible light irradiation. UV-vis DRS, in situ FTIR and XPS results jointly revealed that aniline molecules were efficiently chemisorbed and activated on ZnTi-LDH to form surface coordination active species, improving visible light absorption and inducing the photocatalytic reaction. The surface OH groups on ZnTi-LDH as the Br?nsted base sites facilitated the reductive deprotonation of aniline to form the anilino anion, which was a key step in promoting aniline oxidation. ESR and XPS data suggested that oxygen vacancies (OVs) were formed due to the interaction between exposed OH groups and aniline molecules. The OVs, as the centers to capture photoelectrons, achieve the reduction of oxygen molecules to O2- radicals, which further oxidize anilino species to produce nitrosobenzene. Finally, a possible mechanism was proposed to reveal the photocatalytic process based on the surface coordination activation theory. This journal is
- Liu, Cheng,Guo, Wei,Chen, Jinsong,Zou, Junhua,Wang, Zhiwen,Wu, Ling
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p. 162 - 170
(2021/01/28)
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- Structural and photophysical properties of lanthanide complexes with N'- (2- methoxybenzylidene) - 2-pyridinecarbohydrazide Schiff base ligand: Catalyzed oxidation of anilines with hydrogen peroxide
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Several lanthanide (III) complexes {Ln: La, 1; Sm, 2; Eu, 3; Gd, 4; Tb, 5; Dy, 6} with the Schiff base ligand, N'-?(2-?methoxybenzylidene)?-?2-pyridinecarbohydrazide, L, have been synthesized. These complexes having general formula LaL(NO3)3.xH2O and LnL2(NO3)3.xH2O, and the ligand L have been characterized by elemental analysis, spectral analysis (IR, 1H and 13C NMR), molar conductivity and thermogravimetric analysis. In the proposed structure of complex 1, La(III) ion is ten coordinate. Six coordination sites are satisfied by three bi-dentate nitrate ions, one site is occupied by H2O and the remaining three positions are occupied by ONO belonging to one neutral L. In contrast the lanthanide ion in the proposed structures of complexes 2 - 6, is twelve coordinated by two three bi-dentate ONO L and three bi-dentate nitrate anions. The photophysical properties of L and 1 – 6 in DMF solution have been investigated and reported. Complexes 1 - 6 catalyze the oxidation of aniline 1a and its derivatives 1b - 1 g using H2O2 as an oxygen source at an ambient conditions. Aniline is selectively converted to nitroso-benzene in the presence of complexes 2 and 3. Complexes 4 – 6 gave mixtures of nitrozo- and azoxybenzenes. With complex 1 a mixture of nitroso-, azoxy- and azobenzenes were obtained. Among the substrates tested, the best result was obtained in the case of 1e with 78.6% conversion and 100% selectivity for the nitroso-benzene in the presence of 4 as a catalyst.
- Taha, Ziyad A.,Hijazi, Ahmed K.
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- SO2F2-mediated oxidation of primary and tertiary amines with 30% aqueous H2O2 solution
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A highly efficient and selective oxidation of primary and tertiary amines employing SO2F2/H2O2/base system was described. Anilines were converted to the corresponding azoxybenzenes, while primary benzylamines were transformed into nitriles and secondary benzylamines were rearranged to amides. For tertiary amine substrates quinolines, isoquinolines and pyridines, their oxidation products were the corresponding N-oxides. The reaction conditions are very mild and just involve SO2F2, amines, 30% aqueous H2O2 solution, and inorganic base at room temperature. One unique advantage is that this oxidation system is just composed of inexpensive inorganic compounds without the use of any metal and organic compounds.
- Liao, Xudong,Zhou, Yi,Ai, Chengmei,Ye, Cuijiao,Chen, Guanghui,Yan, Zhaohua,Lin, Sen
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supporting information
(2021/11/01)
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- Sterically Stabilized End-On Superoxocopper(II) Complexes and Mechanistic Insights into Their Reactivity with O-H, N-H, and C-H Substrates
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Instability of end-on superoxocopper(II) complexes, with respect to conversion to peroxo-bridged dicopper(II) complexes, has largely constrained their study to very low temperatures. This limits their kinetic capacity to oxidize substrates. In response, we have developed a series of bulky ligands, Ar3-TMPA (Ar = tpb, dpb, dtbpb), and used them to support copper(I) complexes that react with O2 to yield [CuII(?1-O2?-)(Ar3-TMPA)]+ species, which are stable against dimerization at all temperatures. Binding of O2 saturates at subambient temperatures and can be reversed by warming. The onset of oxygenation for the Ar = tpb and dpb systems is observed at 25 °C, and all three [CuII(?1-O2?-)(Ar3-TMPA)]+ complexes are stable against self-decay at temperatures of ≤-20 °C. This provides a wide temperature window for study of these complexes, which was exploited by performing extensive reaction kinetics measurements for [CuII(?1-O2?-)(tpb3-TMPA)]+ using a broad range of O-H, N-H, and C-H bond substrates. This includes correlation of second order rate constants (k2) versus oxidation potentials (Eox) for a range of phenols, construction of Eyring plots, and temperature-dependent kinetic isotope effect (KIE) measurements. The data obtained indicate that reaction with all substrates proceeds via H atom transfer (HAT), reaction with the phenols proceeds with significant charge transfer, and full tunneling of both H and D atoms occurs in the case of 1,2-diphenylhydrazine and 4-methoxy-2,6-di-tert-butylphenol. Oxidation of C-H bonds proved to be kinetically challenging, and whereas [CuII(?1-O2?-)(tpb3-TMPA)]+ can oxidize moderately strong O-H and N-H bonds, it is only able to oxidize very weak C-H bonds.
- Debnath, Suman,England, Jason,Kr?mer, Tobias,Laxmi, Shoba,Quek, Sebastian Y.,Van Gastel, Maurice
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supporting information
p. 19731 - 19747
(2021/11/30)
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- Electrosynthesis of Azobenzenes Directly from Nitrobenzenes
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The electrochemical reduction strategy of nitrobenzenes is developed. The chemistry occurs under ambient conditions. The protocol uses inert electrodes and the solvent, DMSO, plays a dual role as a reducing agent. Its synthetic value has been demonstrated by the highly efficient synthesis of symmetric, unsymmetric and cyclic azo compounds.
- Ma, Yanfeng,Wu, Shanghui,Jiang, Shuxin,Xiao, Fuhong,Deng, Guo-Jun
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p. 3334 - 3338
(2021/10/29)
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- Application of Al2O3/AlNbO4 in the oxidation of aniline to azoxybenzene
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Al2O3/AlNbO4 powder was fabricated by a facile high-energy milling process. The precursor materials, Al2O3 and Nb2O5, are readily available and have very attractive properties. Moreover, the catalytic activity of the sample in the liquid phase oxidation of aniline (OA) in the presence of hydrogen peroxide as oxidant was evaluated. The catalyst was found to be highly efficient and selective in the oxidation of aniline to azoxybenzene under mild conditions. When mixed with 28% AlNbO4 the alumina-based catalyst achieved high conversion and selectivity and very similar to the pure Nb2O5.
- Batalha, Daniel C.,Luz, Sulusmon C.,Taylor, Jason G.,Fajardo, Humberto V.,Noremberg, Bruno S.,Cherubin, Igor J. S.,Silva, Ricardo M.,Gon?alves, Margarete R. F.,Bergmann, Carlos P.,Valentini, Antoninho,Carre?o, Neftalí L. V.
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p. 543 - 553
(2019/09/06)
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- Identification of the subtype-selective Sirt5 inhibitor balsalazide through systematic SAR analysis and rationalization via theoretical investigations
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We report here an extensive structure-activity relationship study of balsalazide, which was previously identified in a high-throughput screening as an inhibitor of Sirt5. To get a closer understanding why this compound is able to inhibit Sirt5, we initially performed docking experiments comparing the binding mode of a succinylated peptide as the natural substrate and balsalazide with Sirt5 in the presence of NAD+. Based on the evidence gathered here, we designed and synthesized 13 analogues of balsalazide, in which single functional groups were either deleted or slightly altered to investigate which of them are mandatory for high inhibitory activity. Our study confirms that balsalazide with all its given functional groups is an inhibitor of Sirt5 in the low micromolar concentration range and structural modifications presented in this study did not increase potency. While changes on the N-aroyl-β-alanine side chain eliminated potency, the introduction of a truncated salicylic acid part minimally altered potency. Calculations of the associated reaction paths showed that the inhibition potency is very likely dominated by the stability of the inhibitor-enzyme complex and not the type of inhibition (covalent vs. non-covalent). Further in-vitro characterization in a trypsin coupled assay determined that the tested inhibitors showed no competition towards NAD+ or the synthetic substrate analogue ZKsA. In addition, investigations for subtype selectivity revealed that balsalazide is a subtype-selective Sirt5 inhibitor, and our initial SAR and docking studies pave the way for further optimization.
- Bracher, Franz,Dietschreit, Johannes C. B.,Ghazy, Ehab,Glas, Carina,Jung, Manfred,Ochsenfeld, Christian,Sippl, Wolfgang,Urban, Lars,W?ssner, Nathalie
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supporting information
(2020/08/28)
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- Azo aryl urea derivative, and preparation method and application thereof
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The invention relates to an azo aryl urea derivative, and a preparation and an application thereof, and concretely discloses a compound represented by formula (I), or an optical isomer, a cis-trans-isomer or a pharmaceutically acceptable salt thereof, and a preparation method thereof. Definitions of substituent groups in the general formula are described in the specification and claims. The invention further discloses a composition containing the above compound, and an application thereof. The compound has excellent anticancer activity on HepG2 liver cancer cells, MGC803 gastric cancer cells,HCT116 colon cancer and the like.
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Paragraph 0067-0068; 0069-0070; 0129-0132; 0184-0187
(2020/06/17)
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- Photochromic Evaluation of 3(5)-Arylazo-1 H-pyrazoles
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The desire to photocontrol molecular properties ranging from materials to pharmacology using light as an external trigger with high spatiotemporal resolution led to the development of a broad range of photochromic scaffolds. Among them, azobenzenes are synthetically well accessible and show excellent fatigue resistance. Their photochromic properties vary with the substitution pattern and for different heteroarenes. However, the photochromism of 3(5)-substituted-1H-pryazoles has not yet been investigated, although this compound class offers interesting possibilities of metal ion coordination and hydrogen bond formation via its NH moiety. Herein, we present the results of an experimental and computational investigation of arylazo-3(5)-arylazo-1H-pyrazoles. To elucidate their properties, solvent and substitution effects on their light absorption, thermal half-lives, photostationary states, fatigue, and quantum yields were determined.
- Rustler, Karin,Nitschke, Philipp,Zahnbrecher, Sophie,Zach, Julia,Crespi, Stefano,K?nig, Burkhard
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p. 4079 - 4088
(2020/04/09)
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- Azobenzene heterocyclic amide derivative and preparation method and application thereof
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The invention relates to an azobenzene heterocyclic amide derivative and a preparation method and application thereof. The azobenzene heterocyclic amide derivative has the following general formula: based on the structure of the existing succinate dehydrogenase inhibitor bactericide, azobenzene is introduced to synthesize the azobenzene heterocyclic amide derivative with a novel structure, and theazobenzene heterocyclic amide derivative has significant phytopathogen inhibition activity.
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Paragraph 0161-0164; 0174-0176
(2020/05/11)
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- Phenyl pyrazole compound containing azo structure and preparation method and application thereof (by machine translation)
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The invention discloses a phenyl pyrazole compound containing an azo structure, a preparation method thereof and application, of the phenyl pyrazole compound with the azo structure shown in the formula I in the structure, shown by the invention. The phenyl pyrazole compound containing the azo structure according to the invention has good insecticidal activity, and can be used as a pesticide for pest control. (by machine translation)
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Paragraph 0104-0107
(2020/05/08)
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- Optical Control of CRAC Channels Using Photoswitchable Azopyrazoles
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The Ca2+ release-activated Ca2+ (CRAC) channels control many Ca2+-modulated physiological processes in mammals. Hyperactivating CRAC channels are known to cause several human diseases, including Stormorken syndrome. Here, we show the design of azopyrazole-derived photoswitchable CRAC channel inhibitors (designated piCRACs), which enable optical inhibition of store-operated Ca2+ influx and downstream signaling. Moreover, piCRAC-1 has been applied in vivo to alleviate thrombocytopenia and hemorrhage in a zebrafish model of Stormorken syndrome in a light-dependent manner.
- Yang, Xingye,Ma, Guolin,Zheng, Sisi,Qin, Xiaojun,Li, Xiang,Du, Lupei,Wang, Youjun,Zhou, Yubin,Li, Minyong
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p. 9460 - 9470
(2020/06/27)
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- Photoswitchable azo‐ and diazocine‐functionalized derivatives of the vegfr‐2 inhibitor axitinib
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In this study, we aimed at the application of the concept of photopharmacology to the approved vascular endothelial growth factor receptor (VEGFR)‐2 kinase inhibitor axitinib. In a previous study, we found out that the photoisomerization of axitinib’s stilbene‐like double bond is unidirectional in aqueous solution due to a competing irreversible [2+2]‐cycloaddition. Therefore, we next set out to azologize axitinib by means of incorporating azobenzenes as well as diazocine moieties as photoresponsive elements. Conceptually, diazocines (bridged azobenzenes) show favorable photoswitching properties compared to standard azobenzenes because the thermodynamically stable Z‐isomer usually is bioinactive, and back isomerization from the bioactive E‐isomer occurs thermally. Here, we report on the development of different sulfur– diazocines and carbon–diazocines attached to the axitinib pharmacophore that allow switching the VEGFR‐2 activity reversibly. For the best sulfur–diazocine, we could verify in a VEGFR‐2 kinase assay that the Z‐isomer is biologically inactive (IC50 >> 10,000 nM), while significant VEGFR‐2 inhibition can be observed after irradiation with blue light (405 nm), resulting in an IC50 value of 214 nM. In summary, we could successfully develop reversibly photoswitchable kinase inhibitors that exhibit more than 40‐fold differences in biological activities upon irradiation. Moreover, we demonstrate the potential advantage of diazocine photoswitches over standard azobenzenes.
- Heintze, Linda,Schmidt, Dorian,Rodat, Theo,Witt, Lydia,Ewert, Julia,Kriegs, Malte,Herges, Rainer,Peifer, Christian
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- Selective oxidation of aniline into azoxybenzene catalyzed by Nb-peroxo@iron oxides at room temperature
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Oxidation of aniline into valuable products such as azoxybenzene, azobenzene, and nitrobenzene has been a great challenge due to the difficulty of controlling the selectivity of heterogeneous catalysts to form the desired products. In this work, an active and selective heterogeneous catalyst for the oxidation of aniline into azoxybenzene was designed by doping iron oxide supports with niobium and immobilizing Nb-peroxo groups on their surfaces through H2O2treatment. The Nb-peroxo groups on the iron oxide support were essential to catalyze the conversion of aniline into products while the niobium favored the formation of azoxybenzene. Among the alcoholic solvents studied, 1-propanol was the most suitable to get high conversion rates of aniline and high selectivity to azoxybenzene. At 3 h reaction time, the Nb-peroxo@iron oxides led to oxidation of aniline with a conversion rate of 99.6% and 83.7% selectivity to azoxybenzene at room temperature. Since the selective and catalytic oxidation of aniline is very important for the synthesis of intermediates and precursors to various industrially valuable products, the results shown herein may contribute to the development of most stable, selective, and active catalysts under mild reaction conditions.
- Lima, André L. D.,Fajardo, Humberto V.,Nogueira, André E.,Pereira, Márcio C.,Oliveira, Luiz C. A.,de Mesquita, Jo?o Paulo,Silva, Adilson C.
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p. 8710 - 8717
(2020/06/08)
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- Exploring Opportunities for Platinum Nanoparticles Encapsulated in Porous Liquids as Hydrogenation Catalysts
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The unusual combination of characteristics observed for porous liquids, which are typically associated with either porous solids or liquids, has led to considerable interest in this new class of materials. However, these porous liquids have so far only been investigated for their ability to separate and store gases. Herein, the catalytic capability of Pt nanoparticles encapsulated within a Type I porous liquid (Pt@HS-SiO2 PL) is explored for the hydrogenation of several alkenes and nitroarenes under mild conditions (T=40 °C, PH2=1 atm). The different intermediates in the porous liquid synthesis (i.e., the initial Pt@HS-SiO2, the organosilane-functionalized intermediate, and the final porous liquid) are employed as catalysts in order to understand the effect of each component of the porous liquid on the catalysis. For the hydrogenation of 1-decene, the Pt@HS-SiO2 PL catalyst in ethanol has the fastest reaction rate if normalized with respect to the concentration of Pt. The reaction rate slows if the reaction is completed in a “neat” porous liquid system, probably because of the high viscosity of the system. These systems may find application in cascade reactions, in particular, for those with mutually incompatible catalysts.
- Hemming, Ellen B.,Masters, Anthony F.,Maschmeyer, Thomas
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p. 7059 - 7064
(2020/03/24)
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- Niobium oxide prepared through a novel supercritical-CO2-assisted method as a highly active heterogeneous catalyst for the synthesis of azoxybenzene from aniline
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High-surface area Nb2O5 nanoparticles were synthesised by a novel supercritical-CO2-assisted method (Nb2O5-scCO2) and were applied for the first time as a heterogeneous catalyst in the oxidative coupling of aniline to azoxybenzene using the environmentally friendly H2O2 as the oxidant. The application of scCO2 in the synthesis of Nb2O5-scCO2 catalyst resulted in a significantly enhanced catalytic activity compared to a reference catalyst prepared without scCO2 (Nb2O5-Ref) or to commercial Nb2O5. Importantly, the Nb2O5-scCO2 catalyst achieved an aniline conversion of 86% (stoichiometric maximum of 93% with the employed aniline-to-H2O2 ratio of 1?:?1.4) with an azoxybenzene selectivity of 92% and with 95% efficiency in H2O2 utilisation in 45 min without requiring external heating (the reaction is exothermic) and with an extremely low catalyst loading (weight ratio between the catalyst and substrate, Rc/s = 0.005). This performance largely surpasses that of any other heterogeneous catalyst previously reported for this reaction. Additionally, the Nb2O5 catalyst displayed high activity also for substituted anilines (e.g. methyl or ethyl-anilines and para-anisidine) and was reused in consecutive runs without any loss of activity. Characterisation by means of N2-physisorption, XRD, FTIR and TEM allowed the correlation of the remarkable catalytic performance of Nb2O5-scCO2 to its higher surface area and discrete nanoparticle morphology compared to the aggregated larger particles constituting the material prepared without scCO2. A catalytic test in the presence of a radical scavenger proved that the reaction follows a radical pathway.
- Tao, Yehan,Singh, Bhawan,Jindal, Vanshika,Tang, Zhenchen,Pescarmona, Paolo P.
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supporting information
p. 5852 - 5864
(2019/11/11)
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- Determination of band edges and their influences on photocatalytic reduction of nitrobenzene by bulk and exfoliated g-C3N4
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Thermally and chemically exfoliated metal-free semiconducting g-C3N4 are synthesized from bulk g-C3N4. Thorough characterization of the synthesized materials is performed with the help of XRD, FTIR, FE-SEM, PL, surface area analysis and DRS to probe differences in structural, morphological and optical properties between thermally and chemically exfoliated g-C3N4. The synthesized materials are exposed to light for photocatalytic reduction of nitrobenzene. The complete reduction reaction mechanism and product selectivity over the synthesized catalysts are studied in this report. The rate of reduction of nitrobenzene is found to be higher with thermally exfoliated g-C3N4, and the selectivity of aniline is found to be higher in the case of chemical exfoliated g-C3N4. The differences in the reactivity are explained in terms of structure, surface morphologies and band edge positions.
- Challagulla, Swapna,Payra, Soumitra,Chakraborty, Chanchal,Roy, Sounak
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p. 3174 - 3183
(2019/02/15)
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- Tungstate-supported silica-coated magnetite nanoparticles: a novel magnetically recoverable nanocatalyst for green synthesis of nitroso arenes
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Tungstate ion was heterogenized on the silica-coated magnetite nanoparticles and applied for the selective oxidation of anilines to nitroso arenes—with hydrogen peroxide/urea as oxidant in dimethyl carbonate as solvent—in moderate–good yields (40–96%). The catalyst was characterized using different techniques including Fourier-transform infrared spectroscopy, X-ray powder diffraction, vibrating sample magnetometry, scanning electron microscopy, energy dispersive X-ray and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The catalyst was easily recovered using an external magnet and reused for six times.
- Jadidi Nejad, Masoume,Yazdani, Elahe,Kazemi Miraki, Maryam,Heydari, Akbar
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p. 1575 - 1583
(2019/09/09)
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- Synthesis of Functionalized Azobiphenyl- and Azoterphenyl- Ditopic Linkers: Modular Building Blocks for Photoresponsive Smart Materials
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Modular synthesis of structurally diverse functionalized azobiphenyls and azoterphenyls for the realization of optically switchable materials has been described. The corresponding synthesis of azobiphenyls and azoterphenyls by stepwise Mills/Suzuki-Miyaura cross-coupling reaction, proceeds with high yields and provides facile access to a library of functionalized building blocks. The synthetic methods described herein allow combining several distinct functional groups within a single unit, each intended for a specific task, such as 1) the ?N=N? azobenzene core as a photoswitchable moiety, 2) aryls and heteroaryls, functionalized with carboxylic acids or pyridine at its peripheries, as coordinating moieties and 3) varying substitution, size and length of the backbone for adaptability to specific applications. These specifically designed azobiphenyls and azoterphenyls provide modular bricks, potentially useful for the assembly of a variety of polymers, molecular containers and coordination networks, offering a high degree of molecular functionality. Once integrated into materials, the azobenzene system, as a side group on the organic linker backbone, can be exploited for remotely controlling the structural, mechanical or physical properties, thus being applicable for a broad variety of ‘smart’ applications.
- Grosjean, Sylvain,Hodapp, Patrick,Hassan, Zahid,W?ll, Christof,Nieger, Martin,Br?se, Stefan
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p. 743 - 759
(2019/07/03)
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- Photocatalytic oxidation of aniline over MO/TiO2 (M = Mg, Ca, Sr, Ba) under visible light irradiation
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MO/TiO2 (M = Mg, Ca, Sr & Ba; TiO2: Evonik Aroxide P25) composites were prepared for photocatalytic aniline oxidation under visible light irradiation. The conversion efficiencies of aniline over the samples are revealed as follow ord
- Chen, Jinsong,Shen, Chuan,Guo, Binbin,Yu, Yan,Wu, Ling
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p. 312 - 318
(2018/12/13)
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- Novel Phenyldiazenyl Fibrate Analogues as PPAR α/γ/δ Pan-Agonists for the Amelioration of Metabolic Syndrome
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The development of PPARα/γ dual or PPARα/γ/δ pan-agonists could represent an efficacious approach for a simultaneous pharmacological intervention on carbohydrate and lipid metabolism. Two series of new phenyldiazenyl fibrate derivatives of GL479, a previously reported PPARα/γ dual agonist, were synthesized and tested. Compound 12a was identified as a PPAR pan-agonist with moderate and balanced activity on the three PPAR isoforms (α, γ, δ). Moreover, docking experiments showed that 12a adopts a different binding mode in PPARγ compared to PPARα or PPARδ, providing a structural basis for further structure-guided design of PPAR pan-agonists. The beneficial effects of 12a were evaluated both in vitro, on the expression of PPAR target key metabolic genes, and ex vivo in two rat tissue inflammatory models. The obtained results allow considering this compound as an interesting lead for the development of a new class of PPAR pan-agonists endowed with an activation profile exploitable for therapy of metabolic syndrome.
- Giampietro, Letizia,Laghezza, Antonio,Cerchia, Carmen,Florio, Rosalba,Recinella, Lucia,Capone, Fabio,Ammazzalorso, Alessandra,Bruno, Isabella,De Filippis, Barbara,Fantacuzzi, Marialuigia,Ferrante, Claudio,MacCallini, Cristina,Tortorella, Paolo,Verginelli, Fabio,Brunetti, Luigi,Cama, Alessandro,Amoroso, Rosa,Loiodice, Fulvio,Lavecchia, Antonio
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supporting information
p. 545 - 551
(2019/03/19)
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- Rhodium-Catalyzed Reaction of Azobenzenes and Nitrosoarenes toward Phenazines
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A rhodium-catalyzed annulative reaction between azobenzenes and nitrosoarenes has been developed, leading to a series of phenazines in moderate to good yields. This procedure proceeds with sequential chelation-assisted addition of aryl C-H to nitrosoarenes and ring closure by electrophilic attack of azo group to aryl. During this transformation, the azo group served as not only a traceless directing group but also a building block in the final products.
- Xiao, Yan,Wu, Xiaopeng,Wang, Hepan,Sun, Song,Yu, Jin-Tao,Cheng, Jiang
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supporting information
p. 2565 - 2568
(2019/04/30)
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- Enantioselective Oxidative Coupling of β-Ketocarbonyls and Anilines by Joint Chiral Primary Amine and Selenium Catalysis
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An enantioselective primary amine-catalyzed total N-selective nitroso aldol reaction (N-NA) was achieved through the oxidation of primary aromatic amines to the corresponding nitrosoarenes catalyzed by selenium reagents and 30% H2O2. This protocol provides a facile and highly efficient access to α-hydroxyamino carbonyls bearing chiral quaternary centers under exceedingly mild and green reaction conditions with high chemo-and enantiocontrol.
- Chen, Wanting,Wang, Yanni,Mi, Xueling,Luo, Sanzhong
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supporting information
p. 8178 - 8182
(2019/10/16)
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- 1D coordination polymer based on copper(II)-containing tetrameric 1,2,3-triazole ligand from click chemistry: Magnetic and catalytic properties
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A novel tetrameric tetra[O-((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)]-pentaerythritol (TBTP) has been synthesized using click chemistry strategy. TBTP was characterized and used as ligand to form new Cu(II) complexes, forming 1-D coordination polymers. Two square planar complexes were characterized by single-crystal X-ray diffraction, presenting formula [Cu(TBTP)][Cu(NO3)4] (1) and [Cu(TBTP)](NO3)2 (2). In both structures, a cationic 1-D coordination polymer (CP) has been formed. The CP contain a 1:1 Cu(II)/TBTP ratio with four neutral triazole groups coordinating the Cu(II) center, forming a Cu[sbnd]N bonds ranging 1.988(2)–2.001(2) ?. The study of the magnetic properties of compounds 1 and 2 pointed to an antiferromagnetic behavior for both compounds, defined by inter- and intra-chain dipolar interactions among their metallic centers. In addition, the complex 1 was found to be an efficient catalyst for selective oxidation of aniline to azobenzene under mild reaction conditions.
- Moraes, Leonardo C.,de Souza, Gilmar P.,Fajardo, Humberto V.,Luz, Sulusmon C.,álvarez, Eleuterio,Lloret, Francesc,Ribeiro-Viana, Renato M.,Rojo, Javier,Stumpf, Humberto O.,Figueiredo, Rute C.,Corrêa, Rodrigo S.
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- Tandem Chiral Cu(II) Phosphate-Catalyzed Deoxygenation of Nitrones/Enantioselective Povarov Reaction with Enecarbamates
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A new catalytic enantioselective tandem deoxygenation/aza-Diels-Alder reaction of nitrones with enecarbamates was serendipitously discovered in the presence of chiral copper(II) diphosphate complexes. This process affords a wide range of 4-aminotetrahydroquinolines in respectable yields under mild conditions with good to excellent ee values.
- Gelis, Coralie,Levitre, Guillaume,Guérineau, Vincent,Touboul, David,Neuville, Luc,Masson, Géraldine
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p. 5151 - 5155
(2019/06/27)
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- A convenient room temperature ipso-nitration of arylboronic acid catalysed by molecular iodine using zirconium oxynitrate as nitrating species: An experimental and theoretical investigation
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A simple and convenient protocol has been developed for ipso-nitration of arylboronic acid catalysed by molecular iodine at room temperature, using zirconium oxynitrate as the nitrating species. The protocol is applicable to electronically diverse aryl- and heteroarylboronic acid moieties under mild reaction conditions with good to excellent isolated yields. Furthermore, a theoretical investigation has been performed for the same reaction, and reaction profiles are modelled using modern density functional theory (DFT). DFT-based results support the experimentally observed results.
- Mahanta, Abhijit,Gour, Nanda Kishor,Sarma, Plaban Jyoti,Borah, Raju Kumar,Raul, Prasanta Kumar,Deka, Ramesh Chandra,Thakur, Ashim Jyoti,Bora, Utpal
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- Sub-15 nm CeO2 nanowires as an efficient non-noble metal catalyst in the room-temperature oxidation of aniline
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We described herein the facile synthesis of sub-15 nm CeO2 nanowires based on a hydrothermal method without the use of any capping/stabilizing agent, in which an oriented attachment mechanism took place during the CeO2 nanowire formation. The synthesis of sub-15 nm CeO2 nanowires could be achieved on relatively large scales (～2.6 grams of nanowires per batch), in high yields (>94%), and at low cost. To date, there are only a limited number of successful attempts towards the synthesis of CeO2 nanowires with such small diameters, and the reported protocols are typically limited to low amounts. The nanowires displayed uniform shapes and sizes, high surface areas, an increased number of oxygen defects sites, and a high proportion of Ce3+/Ce4+ surface species. These features make them promising candidates for oxidation reactions. To this end, we employed the selective oxidation of aniline as a model transformation. The sub-15 nm CeO2 nanowires catalyzed the selective synthesis of nitrosobenzene (up to 98% selectivity) from aniline at room temperature using H2O2 as the oxidant. The effect of solvent and temperature during the catalytic reaction was investigated. We found that such parameters played an important role in the control of the selectivity. The improved catalytic activities observed for the sub-15 nm nanowires could be explained by: i) the uniform morphology with a typical dimension of 11 ± 2 nm in width, which provides higher specific surface areas relative to those of conventional catalysts; ii) the significant concentration of oxygen vacancies and high proportion of Ce3+/Ce4+ species at the surface that represent highly active sites towards oxidation reactions; iii) the crystal growth along the (110) highly catalytically active crystallographic directions, and iv) the mesoporous surface which is easily accessible by liquid substrates. The results reported herein demonstrated high activities under ambient conditions, provided novel insights into selectivities, and may inspire novel metal oxide-based catalysts with desired performances.
- Da Silva, Anderson G. M.,Batalha, Daniel C.,Rodrigues, Thenner S.,Candido, Eduardo G.,Luz, Sulusmon C.,De Freitas, Isabel C.,Fonseca, Fabio C.,De Oliveira, Daniela C.,Taylor, Jason G.,Córdoba De Torresi, Susana I.,Camargo, Pedro H. C.,Fajardo, Humberto V.
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p. 1828 - 1839
(2018/04/12)
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- Reversible Laser-Induced Bending of Pseudorotaxane Crystals
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This study investigated the dynamic photoresponse of pseudorotaxane crystals with azobenzene and ferrocenyl groups in the axle component. X-ray crystallography showed pseudorotaxanes with a methylazobenzene group and a dibromophenylene ring in the cyclic component to exhibit twisting of the trans-azobenzene groups at torsion angles of 17° and 38°, respectively. Repeated alternating laser irradiation of the crystals at 360 and 445 nm produced bending of 20-30° in opposite directions, with no evidence of decay. Under 445 nm irradiation, bending took place within 0.3 s. A crystal of nonsubstituted pseudorotaxane showed bending of only 2° under 360 nm irradiation due to multiple π-π interactions between the planar trans-azobenzene groups. The pseudorotaxane crystals have two chromophores, bent rapidly and reversibly on irradiation at rates depending on the molecular structure.
- Cheng, Shao-Chi,Chen, Kai-Jen,Suzaki, Yuji,Tsuchido, Yoshitaka,Kuo, Ting-Shen,Osakada, Kohtaro,Horie, Masaki
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supporting information
p. 90 - 93
(2018/01/17)
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- Designed Precursor for the Controlled Synthesis of Highly Active Atomic and Sub-nanometric Platinum Catalysts on Mesoporous Silica
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The development of new methods to synthesize nanometric metal catalysts has always been an important and prerequisite step in advanced catalysis. Herein, we design a stable nitrogen ligated Pt complex for the straightforward synthesis by carbonization of uniformly sized atomic and sub-nanometric Pt catalysts supported on mesoporous silica. During the carbonization of the Pt precursor into active Pt species, the nitrogen-containing ligand directed the decomposition in a controlled fashion to maintain uniform sizes of the Pt species. The nitrogen ligand had a key role to stabilize the single Pt atoms on a weak anchoring support like silica. The Pt catalysts exhibited remarkable activities in the hydrogenation of common organic functional groups with turnover frequencies higher than in previous studies. By a simple post-synthetic treatment, we could selectively remove the Pt nanoparticles to obtain a mixture of single atoms and nanoclusters, extending the applicability of the present method.
- De, Sudipta,Babak, Maria V.,Hülsey, Max J.,Ang, Wee Han,Yan, Ning
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supporting information
p. 1053 - 1059
(2018/03/28)
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- Doped ordered mesoporous carbons as novel, selective electrocatalysts for the reduction of nitrobenzene to aniline
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Ordered mesoporous carbons (OMCs) doped with nitrogen, phosphorus or boron were synthesised through a two-step nanocasting method and studied as electrocatalysts for the reduction of nitrobenzene to aniline in a half-cell setup. The nature of the dopant played a crucial role in the electrocatalytic performance of the doped OMCs, which was monitored by LSV with a rotating disk electrode setup. The incorporation of boron generated the electrocatalysts with the highest kinetic current density, whereas the incorporation of phosphorus led to the lowest overpotential. Doping with nitrogen led to intermediate behaviour in terms of onset potential and kinetic current density, but provided the highest selectivity towards aniline, thus resulting in the most promising electrocatalyst developed in this study. Density functional theory calculations allowed explaining the observed difference in the onset potentials between the various doped OMCs, and indicated that both graphitic N and pyrdinic N can generate active sites in the N-doped electrocatalyst. A chronoamperometric experiment over N-doped OMC performed at -0.75 V vs. Fc/Fc+ in an acidic environment, resulted in a conversion of 61% with an overall selectivity of 87% to aniline. These are the highest activity and selectivity ever reported for an electrocatalyst for the reduction of nitrobenzene to aniline, making N-doped OMC a promising candidate for the electrochemical cogeneration of this industrially relevant product and electricity in a fuel cell setup.
- Daems, Nick,Risplendi, Francesca,Baert, Kitty,Hubin, Annick,Vankelecom, Ivo F. J.,Cicero, Giancarlo,Pescarmona, Paolo P.
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supporting information
p. 13397 - 13411
(2018/07/25)
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- Low temperature liquid phase catalytic oxidation of aniline promoted by niobium pentoxide micro and nanoparticles
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A microwave-assisted hydrothermal method was employed to synthesis Nb2O5 (niobium pentoxide) nanoparticles and the effects of synthesis conditions on the physical-chemical properties were evaluated. The catalytic activity of the prepared samples in the liquid phase oxidation of aniline with aqueous hydrogen peroxide as oxidizing agent was also studied. The nanoparticles showed hexagonal structure and rounded shape covered by nanoneedles. The results evidenced high catalytic activity with total conversion of aniline at ambient condition. Aniline conversion and product selectivities depended on the experimental parameters, particularly the oxidizing agent concentration, the nature of the solvent, type of the catalyst and reaction time.
- Ventura, Wellington M.,Batalha, Daniel C.,Fajardo, Humberto V.,Taylor, Jason G.,Marins, Natália H.,Noremberg, Bruno S.,Tański, Tomasz,Carre?o, Neftalí L.V.
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p. 135 - 140
(2017/06/23)
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- Azobenzene-benzoylphenylureas as photoswitchable chitin synthesis inhibitors
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Benzoylphenylureas (BPUs) are used as synthetic insect growth regulators for inhibiting chitin synthesis. Merging insecticidal BPUs with photoswitchable azobenzene generated photoresponsive chitin synthesis inhibitors. A prepared azobenzene-benzoylphenylurea can be activated upon irradiation with UV light, and shows 6-fold and 2-fold activity difference to armyworm (Mythimna separata) and German cockroach (Blattella germanica) sulfonylurea receptors, respectively. This is the first example of a photoswitchable BPU insecticide. The generation of such a photoresponsive BPU insecticide allows for modulation of the insecticidal activity by light, and may facilitate the spatiotemporal control over the sulfonylurea receptor and the mechanistic study of this kind of insecticide.
- Tian, Xue,Zhang, Chao,Xu, Qi,Li, Zhong,Shao, Xusheng
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supporting information
p. 3320 - 3323
(2017/04/21)
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- Orthogonal switching in four-state azobenzene mixed-dimers
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Azobenzene multi-state switches whose isomerization can be orthogonally induced with photons and electrons are presented. Exposure to green, blue, or ultraviolet light allows toggling between three isomers, while the fourth one is formed selectively via electrocatalytic isomerization.
- Zhao, Fangli,Grubert, Lutz,Hecht, Stefan,Bléger, David
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supporting information
p. 3323 - 3326
(2017/03/22)
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- Rh(III)-Catalyzed bilateral cyclization of aldehydes with nitrosos toward unsymmetrical acridines proceeding with C-H functionalization enabled by a transient directing group
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A Rh(iii)-catalyzed bilateral cyclization was developed for the efficient construction of acridines proceeding with C-H functionalization whereby in situ formation and removal of an imino transient directing group in the presence of catalytic amount of BnNH2 are achieved. In this transformation, a sequential Rh(iii)-catalyzed C-H amination, cyclization, and aromatization process was involved.
- Hu, Weiming,Zheng, Qingheng,Sun, Song,Cheng, Jiang
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supporting information
p. 6263 - 6266
(2017/07/07)
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- Palladium-catalyzed annulation of 2-(aryldiazenyl) aniline with dimethyl sulfoxide to access N-aryl-1H-benzo[d]imidazol-1-amine
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A palladium-catalyzed annulation of 2-(aryldiazenyl) aniline and dimethyl sulfoxide was developed to access N-aryl-1H-benzo[d]imidazol-1-amine in moderate to good yields. Activated by 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide) adduct (DABSO), DMSO served as a “[dbnd]CH[sbnd]” fragment during this procedure. It represents a facile pathway leading to benzimidazoles.
- Wang, Hepan,Sun, Song,Cheng, Jiang
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supporting information
p. 3875 - 3878
(2017/09/15)
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- Access to Fully Substituted Thiazoles and 2,3-Dihydrothiazoles via Copper-Catalyzed [4 + 1] Heterocyclization of α-(N-Hydroxy/aryl)imino-β-oxodithioesters with α-Diazocarbonyls
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An efficient chemoselective practical route to fully substituted thiazoles and 2,3-dihydrothiazoles has been devised by [4 + 1] heterocyclization of α-(N-hydroxy/aryl)imino-β-oxodithioesters with in situ generated Cu-carbenoids of diazocarbonyls. The α-(N-hydroxy/aryl)imino-β-oxodithioesters are readily accessible by the reaction of β-oxodithioesters with nitrous acid/nitrosoarenes. The overall transformation involves sequential N-O/C-N bonds cleavage followed by cascade C-N/C-S bonds formation in one-pot. This new strategy allows full control over the introduction of various sensitive functional groups at different positions of the thiazole ring, broadening the arsenal of synthetic methods to obtain such scaffolds.
- Srivastava, Abhijeet,Shukla, Gaurav,Yadav, Dhananjay,Singh, Maya Shankar
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supporting information
p. 10846 - 10854
(2017/10/27)
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- Titania-Supported Gold Nanoparticles Catalyze the Selective Oxidation of Amines into Nitroso Compounds in the Presence of Hydrogen Peroxide
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In this article, the catalytic activity of titania-supported gold nanoparticles (Au/TiO2) was studied for the selective oxidation of amines into nitroso compounds using hydrogen peroxide (H2O2). Gold nanoparticles deposited on Degussa P25 polymorphs of titania (TiO2) have been found to promote the selective formation of a variety of nitroso arenes in high yields and selectivities, even in a large-scale synthesis. In contrast, alkyl amines are oxidized to the corresponding oximes under the examined conditions. Kinetic studies indicated that aryl amines substituted with electron-donating groups are oxidized faster than the corresponding amines bearing an electron-withdrawing functionality. A Hammett-type kinetic analysis of a range of para-X-substituted aryl amines implicates an electron transfer (ET) mechanism (ρ=-1.15) for oxidation reactions with concomitant formation of the corresponding N-aryl hydroxylamine as possible intermediate. We also show that the oxidation protocol of aryl amines in the presence of 1,3-cyclohexadiene leads in excellent yields to the corresponding hetero Diels-Alder adducts between the diene and the in situ formed nitrosoarenes.
- Fountoulaki, Stella,Gkizis, Petros L.,Symeonidis, Theodoros S.,Kaminioti, Eleni,Karina, Athanasia,Tamiolakis, Ioannis,Armatas, Gerasimos S.,Lykakis, Ioannis N.
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supporting information
p. 1500 - 1508
(2016/05/19)
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- Azopyridine-imidacloprid derivatives as photoresponsive neonicotinoids
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A series of imidacloprid derivatives containing an azopyridine motif as a photoswitchable functional group were designed and synthesized. The new version of photoresponsive imidacloprid analogues showed improved solubility in comparison with their azobenzene analogues. 1.2 to 2-fold activity difference was observed for these azopyridine-imidacloprids against house fly (Musca domestica) and cowpea aphid (Aphis craccivora) upon irradiation.
- Li, Shen,Song, Run-Jiang,Wang, Dong-Hui,Tian, Xue,Shao, Xu-Sheng,Li, Zhong
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p. 635 - 639
(2016/05/19)
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- Synthesis of 1H-Indazoles from Imidates and Nitrosobenzenes via Synergistic Rhodium/Copper Catalysis
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Nitrosobenzenes have been used as a convenient aminating reagent for the efficient synthesis of 1H-indazoles via rhodium and copper catalyzed C-H activation and C-N/N-N coupling. The reaction occurred under redox-neutral conditions with high efficiency and functional group tolerance. Moreover, a rhodacyclic imidate complex has been identified as a key intermediate.
- Wang, Qiang,Li, Xingwei
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supporting information
p. 2102 - 2105
(2016/06/01)
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- Transfer hydrogenation of nitroarenes with hydrazine at near-room temperature catalysed by a MoO2 catalyst
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We present an experimental and computational study of the elementary steps of hydrazine hydrogen transfer on crystalline MoO2, and demonstrate its unique bifunctional metallic-basic properties in a catalytic hydrogenation reaction. Density functional theory (DFT) calculations suggest that the stepwise hydrogen transfer via the prior cleavage of the N-H bond rather than the N-N bond, is the key step to create the dissociated hydride and proton species on the dual Mo and O sites, marking its difference with common oxides. Crystalline MoO2 shows exceptionally high chemoselectivity toward the nitro reduction over C=C, C≡C, and C≡N groups at room temperature and lower, down to 0 °C, rendering it as a promising catalytic material for hydrogenation reactions.
- Zhang, Chaofeng,Lu, Jianmin,Li, Mingrun,Wang, Yehong,Zhang, Zhe,Chen, Haijun,Wang, Feng
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supporting information
p. 2435 - 2442
(2016/05/19)
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- Transfer hydrogenation of nitroarenes to arylamines catalysed by an oxygen-implanted MoS2 catalyst
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We present an efficient approach for chemoselective synthesis of various functionalized arylamines from nitroarenes over an oxygen-implanted MoS2 catalyst (O-MoS2). The HRTEM, XRD, XPS, Raman, EXAFS and NH3-TPD characterizations show the existence of MoIVOx structure and abundant coordinative unsaturated (CUS) Mo sites in the 2D-layer structure of O-MoS2. In the transfer hydrogenation of nitroarenes with hydrazine hydrate, the MoIVOx structure works as the catalytic active center. The N2H4 selectively decomposes to the active hydrogen species in polar electronic states (Hδ? and Hδ+), which show high chemoselectivity toward the nitro reduction over [Formula presented], [Formula presented], and [Formula presented] groups. The O-MoS2 catalyst can be recovered in a facile manner from the reaction mixture and recycled four times without any significant loss of activity.
- Zhang, Chaofeng,Zhang, Zhixin,Wang, Xu,Li, Mingrun,Lu, Jianmin,Si, Rui,Wang, Feng
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