- Heteroleptic 1,4-Diazabutadiene Complexes of Ruthenium: Synthesis, Characterization and Utilization in Catalytic Transfer Hydrogenation
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Reaction of [Ru(trpy)Cl3] with 1,4-diazabutadienes (p-RC6H4N=C(H)-(H)C=NC6H4R-p; R = OCH3, CH3, H and Cl; abbreviated as L-R) in refluxing ethanol in the presence of triethylamine has afforded a family of complexes, isolated as perchlorate salts, of type [Ru(trpy)(L-R)Cl]ClO4 [depicted as complexes 1 (R = OCH3), 2 (R = CH3), 3 (R = H) and 4 (R = Cl)]. Crystal structures of complexes 1, 2 and 4 have been determined, and structure of complex 3 has been optimized by DFT method. The 1,4-diazabutadiene ligand in each complex is bound to ruthenium as a N,N-donor forming five-membered chelate. Complexes 1–4 catalyze transfer hydrogenation of aryl aldehydes to the corresponding alcohols with high (ca. 106) TON. They are also found to catalyze transfer hydrogenation of aryl ketones to corresponding secondary alcohols, but with much less efficiency. Catalytic transfer hydrogenation of nitroarenes to the corresponding amines has also been achieved.
- Saha, Rumpa,Mukherjee, Aparajita,Bhattacharya, Samaresh
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p. 4539 - 4548
(2020/11/30)
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- Biomass Sucrose-Derived Cobalt@Nitrogen-Doped Carbon for Catalytic Transfer Hydrogenation of Nitroarenes with Formic Acid
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Fabrication of non-noble metal-based heterogeneous catalysts by a facile and cost-effective strategy for ecofriendly catalytic transfer hydrogenation (CTH) is of great significance for organic transformations. A cobalt@nitrogen-doped carbon (Co@NC) catalyst was prepared from renewable biomass-derived sucrose, harmless melamine, and earth-abundant Co(AcO)2 as the precursor materials by hydrothermal treatment and carbonization. Co nanoparticles (NPs) were coated with NC shells and uniformly embedded in the NC framework. The as-obtained Co@NC-600 (carbonized at 600 °C) catalyst exhibited excellent catalytic efficiency for CTH of various functionalized nitroarenes with formic acid (FA) as hydrogen donor in aqueous solution. The uniformly incorporated N atoms in the C matrix and the encapsulated Co NPs showed synergistic effects in the CTH reactions. A mechanistic analysis indicated that the protons from FA were activated by Co sites after being captured by N atoms, and then reacted with nitroarenes adsorbed on the surface of the catalysts to generate the corresponding aromatic amines. Moreover, the catalyst showed excellent durability and reusability without obvious decrease in activity even after five reaction cycles. Thus, the study reported herein provides a cost-effective, sustainable strategy for fabrication of biomass-derived non-noble metal-based catalysts for green and efficient catalytic transformations.
- Yuan, Man,Long, Yu,Yang, Jin,Hu, Xiwei,Xu, Dan,Zhu, Yangyang,Dong, Zhengping
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p. 4156 - 4165
(2018/11/01)
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- Platinum nanoparticles onto pegylated poly(lactic acid) stereocomplex for highly selective hydrogenation of aromatic nitrocompounds to anilines
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A stereocomplexed poly(lactic acid)-polyethyleneglycol copolymer was synthesized and successfully used as recyclable support for Pt nanoparticles, generated by the metal vapor synthesis technique. The confinement of the Pt nanoparticles were determined by thermal analysis. Hydrogenation reactions of chlorinated aromatic nitro compounds, containing other reducible functional groups, to the corresponding anilines occurred with the latter supported Pt nanoparticles in MeOH under very mild reaction conditions (i.e. 30?°C, p(H2)?=?5.0?bar). The covalently attached polyethyleneglycol polymer significantly increased the catalytic activity of the supported Pt nanoparticles compared to an analogous catalytic system which did not contain polyethyleneglycol but the same sized Pt nanoparticles.
- Oberhauser, Werner,Evangelisti, Claudio,Tiozzo, Cristina,Bartoli, Mattia,Frediani, Marco,Passaglia, Elisa,Rosi, Luca
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- Gold supported on titania for specific monohydrogenation of dinitroaromatics in the liquid phase
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Liquid-phase selective monohydrogenation of various substituted dinitroaromatics to the corresponding valuable nitroanilines was investigated on gold-based catalysts. Special attention was paid to the effect of Au particle size on this monoreduction reaction. Interestingly, TiO2 supported gold catalysts containing a relatively larger mean Au particle size (>5 nm) showed far superior chemoselectivity for specific mono-hydrogenation of dinitroaromatics, with the highest performance attainable for the catalyst bearing Au particles of ca. 7.5 nm. Results in the intermolecular competitive hydrogenation showed that the intrinsic higher accumulation rates of the desired nitroanilines associated with the catalyst possessing larger Au particles were responsible for the high chemoselectivity observed. the Partner Organisations 2014.
- Liu, Shuang-Shuang,Liu, Xiang,Yu, Lei,Liu, Yong-Mei,He, He-Yong,Cao, Yong
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p. 4162 - 4169
(2014/09/29)
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- Glycinatocopper(II) complex as an efficient heterogeneous catalyst for aromatic Finkelstein reaction of aryl and heteroaryl bromides to chlorides
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Glycinatocopper(II) complex 1, readily synthesized from copper chloride and glycine was characterized by various techniques including FTIR, XRD, TGA and SEM analysis. The as-synthesized copper complex was found to be a simple and efficient catalyst for the synthesis of aryl and heteroaryl chlorides via aromatic Finkelstein reaction of aryl and heteroaryl bromides in high to excellent yields. The developed glycinatocopper(II) catalyst could easily be recovered from the reaction mixture and reused successfully for several runs without any loss in catalytic efficiency. The developed methodology represents the first example of the use of heterogeneous catalyst for the synthesis of aryl and heteroaryl chlorides via aromatic Finkelstein reaction.
- Verma, Sanny,Saran, Sandeep,Jain, Suman L.
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p. 178 - 183
(2014/02/14)
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- Excellent catalytic properties over nanocomposite catalysts for selective hydrogenation of halonitrobenzenes
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A partially reduced Pt/γ-Fe2O3 magnetic nanocomposite catalyst (Pt/γ-Fe2O3-PR) exhibited excellent catalytic properties in the selective hydrogenation of 2, 4-dinitrochlorobenzene and iodonitrobenzenes. The selectivity to 4-chloro-m-phenylenediamine (4-CPDA), meta-iodoaniline (m-IAN), and para-iodoaniline (p-IAN) reached 99.9%, 99.8%, and 99.4%, respectively, at complete conversion of the substrates. The hydrodehalogenation of 4-CPDA and IANs was fully suppressed for the first time over Pt/γ-Fe2O3-PR. It was found that CO chemisorption on the Pt nanoparticles deposited on the partially reduced γ-Fe2O3 and Fe3O4 nanoparticles was very weak, implying a weak tendency of the electronic back-donation from the Pt nanoparticles to the π* antibonding orbitals of the adsorbed molecules. We believe that this is a cause of the superior selectivity to the haloanilines in the hydrogenation reactions of interest over the Pt/γ-Fe2O3-PR catalyst.
- Liang, Minghui,Wang, Xiaodong,Liu, Hongquan,Liu, Haichao,Wang, Yuan
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p. 335 - 342
(2008/12/20)
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- Effect of the electronic structure of the radical anions of 4-substituted 1,2-and 1,3-dinitrobenzenes on the regioselectivity of reduction of the nitro groups
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Theoretical and experimental regularities of the regioselectivity of the reduction of one of the two nitro groups in unsymmetrical dinitrobenzenes were studied. It was found that the regioselectivity of the formation of isomeric nitroanilines depends on the structure of the substrate and the nature of the reducing agent. The reduction regioselectivity model was verified, according to which radical anion protonation is the major reaction direction. Pleiades Publishing, Inc. 2006.
- Orlov,Begunov,Demidova,Rusakov
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- Guanidinium nitrate: A novel reagent for aryl nitrations
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Nitration of various aromatic compounds utilising guanidinium nitrate in 85% sulfuric acid as a nitrating agent has been studied.
- Ramana,Malik,Parihar
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p. 8681 - 8683
(2007/10/03)
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- Factors controlling regioselectivity in the reduction of polynitroaromatics in aqueous solution
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Regioselectivities in the bisulfide reduction of 10 polynitroaromatics (PNAs) to monoamine products have been determined; four of these compounds have also been reduced by anoxic sediments in heterogeneous aqueous solution, and the same regioselectivities are observed. Analyses of Austin Model 1- Solvation Model 2 electrostatic potential surfaces for the radical anions of these polynitroaromatic compounds provides a reliable method of predicting the regioselectivity of their reduction. In particular, at their minimum- energy geometries in aqueous solution, it is the more negative nitro group that is selectively reduced. This is consistent with a mechanism where regioselection occurs upon kinetic protonation at the site of maximum negative charge in the radical anion formed after the first electron transfer to the neutral PNA. Inclusion of solvation effects is critical in order to confidently predict the electrostatic preference for the reduction of one nitro group over the others. Sterically uncongested nitroaromatic radical anions have gas-phase geometries in which the nitro group is coplanar with the aromatic ring. However, ortho substituents and solvation effects both oppose this tendency and can lead to nitro groups that are rotated out of the ring plane and pyramidalized.
- Barrows, Susan E.,Cramer, Christopher J.,Truhlar, Donald G.,Elovitz, Michael S.,Weber, Eric J.
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p. 3028 - 3038
(2007/10/03)
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- RADICAL-ANIONS OF AROMATIC COMPOUNDS. XVI. ELECTRONIC STRUCTURE OF RADICAL-ANIONS AND THE DIRECTION OF PARTIAL REDUCTION OF DISUBSTITUTED DERIVATIVES OF m-DINITROBENZENE: THE RELATIVE EFFECTS OF THE SUBSTITUENTS
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It was shown by means of compounds labeled with the 15N isotope that the radical-anions of a wide range of 1,5-disubstituted 2,4-dinitrobenzenes are in most cases characterized by localization of the density of the unpaired electron at one of the nitro groups.It was concluded that the substituents can be arranged in the following order according to their ability to stabilize the form with the negatively charged nitro group at the para position: CO2- > CH3 Br > Cl N(C2H5)2 > CN > OCH3; CO2- > I.The relative effectiveness of the substituents which stabilize the form of the radical-anions with the negatively charged nitro group at the ortho position was determined theoretically as follows: OCH3 +C5H5 +H(C2H5)2.The position of the substituents in the series given above are determined by the combined effect of such factors as the effective volume, the electronic effect transmitted through the skeleton, the field effect, and the ability to form intramolecular hydrogen bonds.It was shown that the direction of partial reduction of the derivatives of m-dinitrobenzene can be predicted on the basis of data on the electronic structure of their radical-anions, which are probable key intermediates of the processes.
- Uskov, S. I.,Bilkis, I. I.,Shteingarts, V. D.
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- Selective hydrogenation of polynitroaromatic derivatives with noble metal catalysts in the presence of catalytic amounts of iron
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Hydrogen over PtO2, 5%Pd(c), PdCl2, or 5%Rh(al2O3), in the presence of catalytic amounts of iron and under mild reaction conditions, resulted in the selective reduction of a variety of polynitroaromatic compounds in high yields.
- Theodoridis,Manfredi,Krebs
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p. 6141 - 6144
(2007/10/02)
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- THE NUCLEOPHILIC AROMATIC PHOTOSUBSTITUTIONS OF 4,5-DINITROVERATROLE WITH AMINES. PHOTOREDUCTIONS OF AROMATIC DINITROCOMPOUNDS
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4,5-Dinitroveratrole is effectively photosubstituted by amines with relatively high ionization potential such as methylamine, n-butylamine and ethyl glycinate, but is mainly photoreduced when amines with relatively low ionization potential, such as dimethyl or trimethylamine are used.The photoreduction of several aromatic dinitrocompounds by triethylamine gives nitroanilines.A mechanistic scheme is proposed embracing our photosubstitutions and photoreductions, based on our experimental results and on MINDO/3 calculations of the ground states and the more likely intermediates.
- Marquet, Jorge,Moreno-Manas, Marcial,Vallribera, Adelina,Virgili, Albert,Bertran, Joan,et al.
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p. 351 - 360
(2007/10/02)
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- Azo pigments derived from 2-hydroxy-3-carboxynaphthalene containing a substituted or unsubstituted phthalimide
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Azo pigments derived from 2-hydroxy-3-carboxy-naphthalene and containing a substituted or unsubstituted phthalimide radical. The majority give red colorations and due to their excellent fastness properties are particularly valuable for use in surface coatings and resins.
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