- Organocatalyticvs.Ru-based electrochemical hydrogenation of nitrobenzene in competition with the hydrogen evolution reaction
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The electrochemical reduction of organic contaminants allows their removal from water. In this contribution, the electrocatalytic hydrogenation of nitrobenzene is studied using both oxidized carbon fibres and ruthenium nanoparticles supported on unmodified carbon fibres as catalysts. The two systems produce azoxynitrobenzene as the main product, while aniline is only observed in minor quantities. Although PhNO2hydrogenation is the favoured reaction, the hydrogen evolution reaction (HER) competes in both systems under catalytic conditions. H2formation occurs in larger amounts when using the Ru nanoparticle based catalyst. While similar reaction outputs were observed for both catalytic systems, DFT calculations revealed some significant differences related to distinct interactions between the catalytic material and the organic substrates or products, which could pave the way for the design of new catalytic materials.
- Alemán, José,Creus, Jordi,García-Antón, Jordi,Mas-Ballesté, Rubén,Moya, Alicia,Philippot, Karine,Romero, Nuria,Sala, Xavier,Solans-Monfort, Xavier
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- Mixture of fuels approach for the synthesis of SrFeO3-δ nanocatalyst and its impact on the catalytic reduction of nitrobenzene
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A modified solution combustion approach was applied in the synthesis of nanosize SrFeO3-δ; (SFO) using single as well as mixture of citric acid, oxalic acid, and glycine as fuels with corresponding metal nitrates as precursors. The synthesized and calcined powders were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis and derivative thermogravimetric analysis (TG-DTG), scanning electron microscopy, transmission electron microscopy, N2 physisorption methods, and acidic strength by n-butyl amine titration methods. The FT-IR spectra show the lower-frequency band at 599 cm-1 corresponds to metal-oxygen bond (possible Fe-O stretching frequencies) vibrations for the perovskite-structure compound. TG-DTG confirms the formation temperature of SFO ranging between 850-900 °C. XRD results reveal that the use of mixture of fuels in the preparation has effect on the crystallite size of the resultant compound. The average particle size of the samples prepared from single fuels as determined from XRD was ～50-35 nm, whereas for samples obtained from mixture of fuels, particles with a size of 30-25 nm were obtained. Specifically, the combination of mixture of fuels for the synthesis of SFO catalysts prevents agglomeration of the particles, which in turn leads to decrease in crystallite size and increase in the surface area of the catalysts. It was also observed that the present approach also impacted the catalytic activity of the SFO in the catalytic reduction of nitrobenzene to azoxybenzene.
- Naveenkumar, Akula,Kuruva, Praveena,Shivakumara, Chikkadasappa,Srilakshmi, Chilukoti
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- Domino reaction between nitrosoarenes and ynenones for catalyst-free preparation of indanone-fused tetrahydroisoxazoles
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A catalyst-free domino reaction to synthesize highly functionalized indanone-fused tetrahydroisoxazole from easily accessed nitrosoarene and 1,6-ynenone with good chemo- A nd regioselectivity was disclosed. This unprecedented domino reaction represents a new strategy for multifunctionalization of an internal alkyne with nitrosoarene by formation of two rings and four bonds in a single operation.
- Qiu, Shaotong,Liang, Renxiao,Wang, Yongdong,Zhu, Shifa
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- THE CATALYTIC TRANSFORMATION OF NITROSOBENZENE INTO AZOXY AND AZOBENZENE
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Nitrosobenzene is converted into azoxybenzene in alcoholic media in the presence of Ru(CO)3(PPh3)2 as catalyst and under an inert atmosphere; Fe(CO)3(PPh3)2 and palladium complexes such as PdL2Cl2 (L = PhNO, p-MeC6H4NH2, PPh3) and Pd3(CO)3(PPh3)4, are less active as catalysts.Under CO pressure and with Ru(CO)3(PPh3)2 as catalyst, nitrosobenzene is converted into azobenzene and aniline, while azoxybenzene gives azobenzene.
- Rorta, F.,Pizzotti, M.,Cenini, S.
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- Painting anatase (TiO2) nanocrystals on long nanofibers to prepare photocatalysts with large active surface for dye degradation and organic synthesis
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Anatase TiO2 nanocrystals were painted on H-titanate nanofibers by using an aqueous solution of titanyl sulfate. The anatase nanocrystals were bonded solidly onto the titanate fibers through formation of coherent interfaces at which the oxygen atoms were shared by the nanocrystals and the fiber. This approach allowed us to create large anatase surfaces on the nanofibers, which are active in photocatalytic reactions. This method was also applied successfully to coat anatase nanocrystals on surfaces of fly ash and layered clay. The painted nanofibers exhibited a much higher catalytic activity for the photocatalytic degradation of sulforhodamineB and the selective oxidation of benzylamine to the corresponding imine (with a product selectivity >99%) under UV irradiation than both the parent H-titanate nanofibers and a commercial TiO2 powder, P25. We found that gold nanoparticles supported on H-titanate nanofibers showed no catalytic activity for the reduction of nitrobenzene to azoxybenzene, whereas the gold nanoparticles supported on the painted nanofibers and P25 could efficiently reduce nitrobenzene to azoxybenzene as the sole product under visible light irradiation. These results were different from those from the reduction on the gold nanoparticles photocatalyst on ZrO2, in which the azoxybenzene was the intermediate and converted to azobenzene quickly. Evidently, the support materials significantly affect the product selectivity of the nitrobenzene reduction. Finally, the new photocatalysts could be easily dispersed into and separated from a liquid because of their fibril morphology, which is an important advantage for practical applications.
- Zheng, Zhanfeng,Zhao, Jian,Liu, Hongwei,Liu, Jiangwen,Bo, Arixin,Zhu, Huaiyong
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- Modified cellulose with tunable surface hydrophilicity/hydrophobicity as a novel catalyst support for selective reduction of nitrobenzene
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Cellulose with tailorable hydrophilicity/hydrophobicity were synthesized by grafting F-containing groups and utilized as supports for palladium nanoparticles. The obtained catalysts were applied in the synthesis of N-phenylhydroxylamine from controllable reduction of nitrobenzene. Unexpectedly high conversion and selectivity could be achieved with 25 ppm Pd catalyst at room temperature in water. The precise modification of the catalyst surface is crucial to realize this targeted transformation. Further investigation indicated that modified cellulose with a more hydrophobic surface would favour the adsorption of nitrobenzene over N-phenylhydroxylamine thus prevent full hydrogenation to aniline.
- Li, Dan-dan,Lu, Guo-ping,Cai, Chun
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- Skeletal Rearrangement in the ZnII-Catalyzed [4+2]-Annulation of Disubstituted N-Hydroxy Allenylamines with Nitrosoarenes to Yield Substituted 1,2-Oxazinan-3-one Derivatives
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This work reports zinc-catalyzed [4+2]-annulation reactions of disubstituted N-hydroxy allenylamines with nitrosoarenes to afford substituted 1,2-oxazinan-3-ones with a skeletal rearrangement. This annulation is applicable to a reasonable scope of allenylamines and nitrosoarenes. Our control experiments indicate that nitrosobenzene can also implement this annulation through a radical annulation path, but with poor efficiency. Zn(OTf)2or AgOTf greatly improves the efficiency of this [4+2]-annulation; the effect of these metal species is discussed in detail.
- Sharma, Pankaj,Liu, Rai-Shung
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- STRUCTURE AND CATALYTIC ACTIVITY OF METAL COMPLEXES ON CARRIERS. 3. RHODIUM COMPLEXES ON MODIFIED POLYMERS AND THEIR CATALYTIC PROPERTIES IN THE REDUCTION OF NITROBENZENE BY CHEMICALLY BOUND HYDROGEN
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Heterogenized catalysts based on rhodium complexes attached to polymers modified by the groups 3(5)-methylpyrazole, imidazole and benzimidazole have been synthesized.The process of their formation has been investigated by IR, UV, and EPR spectroscopy.Results have been obtained for the catalytic activity of the complexes in the hydrogenation of nitrobenzene by hydrogen transfer from propan-2-ol and NaBH4.
- Dovganyuk, V. F.,Sharf, V. Z.,Belyaeva, V. K.,Marov, I. N.,Dykh, Zh. L.,et al.
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- Effect of the nature of a transition metal dopant in BaTiO3 perovskite on the catalytic reduction of nitrobenzene
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In the present study, we have synthesized Fe, Co and Ni doped BaTiO3 catalyst by a wet chemical synthesis method using oxalic acid as a chelating agent. The concentration of the metal dopant varies from 0 to 5 mol% in the catalysts. The physical and chemical properties of doped BaTiO3 catalysts were studied using various analytical methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), BET surface area and Transmission electron microscopy (TEM). The acidic strength of the catalysts was measured using a n-butylamine potentiometric titration method. The bulk BaTiO3 catalyst exhibits a tetragonal phase with the P4mm space group. A structural transition from tetrahedral to cubic phase was observed for Fe, Co and Ni doped BaTiO3 catalysts with an increase in doped metal concentration from 1 to 5 mol%. The particle sizes of the catalysts were calculated from TEM images and are in the range of 30-80 nm. All the catalysts were tested for the catalytic reduction of nitrobenzene to azoxybenzene. The BaTiO3 catalyst was found to be highly active and less selective compared to the doped catalysts which are active and highly selective towards azoxybenzene. The increase in selectivity towards azoxybenzene is due to an increase in acidic strength and reduction ability of the doped metal. It was also observed that the nature of the metal dopant and their content at the B-site has an impact on the catalytic reduction of nitrobenzene. The Co doped BaTiO3 catalyst showed better activity with only 0.5 mol% doping than Fe and Ni doped BaTiO3 catalysts with maximum nitrobenzene conversion of 91% with 78% selectivity to azoxybenzene. An optimum Fe loading of 2.5 mol% in BaTiO3 is required to achieve 100% conversion with 93% selectivity whereas Ni with 5 mol% showed a conversion of 93% and a azoxybenzene selectivity of 84%. This journal is
- Srilakshmi, Chilukoti,Rao, G. Mohan,Saraf, Rohit
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- Zr(OH)4-Catalyzed Controllable Selective Oxidation of Anilines to Azoxybenzenes, Azobenzenes and Nitrosobenzenes
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The selective oxidation of aniline to metastable and valuable azoxybenzene, azobenzene or nitrosobenzene has important practical significance in organic synthesis. However, uncontrollable selectivity and laborious synthesis of the expensive required catalysts severely hinders the uptake of these reactions in industrial settings. Herein, we have pioneered the discovery of Zr(OH)4 as an efficient heterogeneous catalyst capable of the selective oxidation of aniline, using either peroxide or O2 as oxidant, to selectively obtain various azoxybenzenes, symmetric/unsymmetric azobenzenes, as well as nitrosobenzenes, by simply regulating the reaction solvent, without the need for additives. Mechanistic experiments and DFT calculations demonstrate that the activation of H2O2 and O2 is primarily achieved by the bridging hydroxyl and terminal hydroxyl groups of Zr(OH)4, respectively. The present work provides an economical and environmentally friendly strategy for the selective oxidation of aniline in industrial applications.
- Long, Yu,Luo, Nan,Ma, Jiantai,Qin, Jiaheng,Sun, Fangkun,Wang, Wei David,Zhou, Pan-Pan
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supporting information
(2021/12/09)
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- Chemoselective electrochemical reduction of nitroarenes with gaseous ammonia
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Valuable aromatic nitrogen compounds can be synthesized by reduction of nitroarenes. Herein, we report electrochemical reduction of nitroarenes by a protocol that uses inert graphite felt as electrodes and ammonia as a reductant. Depending on the cell voltage and the solvent, the protocol can be used to obtain aromatic azoxy, azo, and hydrazo compounds, as well as aniline derivatives with high chemoselectivities. The protocol can be readily scaled up to >10 g with no decrease in yield, demonstrating its potential synthetic utility. A stepwise cathodic reduction pathway was proposed to account for the generations of products in turn.
- Chang, Liu,Li, Jin,Wu, Na,Cheng, Xu
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supporting information
p. 2468 - 2472
(2021/04/02)
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- The relationship of morphology and catalytic performance of CeO2 catalysts for reducing nitrobenzene to azoxybenzene under the base-free condition
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CeO2 morphology was proposed to be a crucial factor for reducing nitrobenzene to azoxybenzene under the base-free condition. Herein, the structure-activity relationship of CeO2 catalysts was explored to improve the azoxybenzene yield. A series of CeO2 catalysts were synthesized with seven morphologies to obtain different Ce3+ proportion and various surface areas. Notably, the catalytic performance of these samples for reducing nitrobenzene to azoxybenzene enhanced with the increasing Ce3+ proportion. With the highest surface Ce3+ proportion, the Rod-CeO2 catalyst exhibited 100% conversion of nitrobenzene and 89.8% azoxybenzene selectivity in 7 h at 150 °C under 1 MPa CO. Moreover, the preliminary mechanistic analysis indicated that the inhabitation of azoxybenzene to by-product azobenzene resulted in the high selectivity of azoxybenzene.
- Zhou, Xueke,Zhao, Haitao,Liu, Shaojun,Yang, Yang,Qu, Ruiyang,Zhen, Chenghang,Gao, Xiang
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supporting information
p. 761 - 764
(2020/07/17)
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- A mild and selective Cu(II) salts-catalyzed reduction of nitro, azo, azoxy, N-aryl hydroxylamine, nitroso, acid halide, ester, and azide compounds using hydrogen surrogacy of sodium borohydride
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The first mild, in situ, single-pot, high-yielding well-screened copper (II) salt-based catalyst system utilizing the hydrogen surrogacy of sodium borohydride for selective hydrogenation of a broad range of nitro substrates into the corresponding amine under habitancy of water or methanol like green solvents have been described. Moreover, this catalytic system can also activate various functional groups for hydride reduction within prompted time, with low catalyst-loading, without any requirement of high pressure or molecular hydrogen supply. Notably, this system explores a great potential to substitute expensive traditional hydrogenation methodologies and thus offers a greener and simple hydrogenative strategy in the field of organic synthesis.
- Kalola, Anirudhdha G.,Prasad, Pratibha,Mokariya, Jaydeep A.,Patel, Manish P.
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supporting information
p. 3565 - 3589
(2021/10/12)
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- Biogenic Synthesis of Gold Nanoparticles on a Green Support as a Reusable Catalyst for the Hydrogenation of Nitroarene and Quinoline
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Direct attachment of gold nanoparticles to a green support without the use of an external reducing agent and using it for removing toxic pollutants from wastewater, i. e., reduction of nitroarene to amine, are described. A novel approach involving the reduction of gold by the jute plant (Corchorus genus) stem-based (JPS) support itself to form nanoparticles (AuNPs) to be used as a catalytic system (‘dip-catalyst’) and its catalytic activity for the hydrogenation of series of nitroarenes in aqueous media are presented. AuNPs/JPS catalyst was characterized using SEM, UV-Vis, FTIR, TEM, XPS, and ICP-OES. Confined area elemental mapping exhibits uniform and homogeneous distribution of AuNPs on the support surface. TEM shows multi-faceted AuNPs in the range of 20–30 nm. The reactivity of AuNPs/JPS for the transfer hydrogenation of nitroarene as well as hydrogenation of quinoline under molecular H2 pressure was evaluated. Sodium borohydride, when used as the hydrogen source, demonstrates a high catalytic efficiency in the transfer hydrogenation reduction of 4-nitrophenol (4-NP). Quinoline is quantitatively and chemoselectively hydrogenated to 1,2,3,4-tetrahydroquinoline (py-THQ) using molecular hydrogen. Reusability studies show that AuNPs are stable on the support surface and their selectivity is not affected.
- Adeyeye Nafiu, Sodiq,Aziz, Abdul,Shaheen Shah, Syed,Shaikh, M. Nasiruzzaman
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p. 1956 - 1966
(2021/06/18)
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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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- Calculated oxidation potentials predict reactivity in Baeyer-Mills reactions
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Azobenzenes are widely used as dyes and photochromic compounds, with the Baeyer-Mills reaction serving as the most common method for their preparation. This transformation is often plagued by low yields due to the formation of undesired azoxybenzene. Here, we explore electronic effects dictating the formation of the azoxybenzene side-product. Using calculated oxidation potentials, we were able to predict reaction outcomes and improve reaction efficiency simply by modulating the oxidation potential of the arylamine component.
- Gingrich, Phillip W.,Olson, David E.,Tantillo, Dean J.,Tombari, Robert J.,Tuck, Jeremy R.,Yardeny, Noah
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supporting information
p. 7575 - 7580
(2021/09/22)
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- Preparation of niobium or tantalum complex and application of niobium or tantalum complex in catalyzing aromatic amine to generate oxidized azobenzene compound
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The invention provides a preparation method of niobium or tantalum complex and an application of the niobium or tantalum complex in catalyzing aromatic amine to generate an oxidized azobenzene compound. The preparation method of the complex comprises A hydration oxide preparation, @timetime@ niobium oxide or tantalum oxide and strong base in 300 - 800 °C melting calcination 2 - 8h, adding water to dissolve and filter, and then adjusting pH through 4-6, suction filtration and drying. The B complex is prepared by mixing a hydrated oxide with a molar ratio 10-25: 1 with hydrogen peroxide, adding an organic acid and a cationic precursor after clarifying the solution, and evaporating and drying to obtain a niobium complex or a tantalum complex. The molar ratio @timetime@: 1-3. In the method for synthesizing the oxidized azobenzene compound by using niobium or tantalum complex as a catalyst, ethanol is used as a solvent, hydrogen peroxide is used as an oxidant, niobium complex or tantalum complex is used as a catalyst, and the addition amount is ppm.
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Paragraph 0052-0055
(2021/11/03)
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- Selective Oxidation of Anilines to Azobenzenes and Azoxybenzenes by a Molecular Mo Oxide Catalyst
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Aromatic azo compounds, which play an important role in pharmaceutical and industrial applications, still face great challenges in synthesis. Herein, we report a molybdenum oxide compound, [N(C4H9)4]2[Mo6O19] (1), catalyzed selective oxidation of anilines with hydrogen peroxide as green oxidant. The oxidation of anilines can be realized in a fully selectively fashion to afford various symmetric/asymmetric azobenzene and azoxybenzene compounds, respectively, by changing additive and solvent, avoiding the use of stoichiometric metal oxidants. Preliminary mechanistic investigations suggest the intermediacy of highly active reactive and elusive Mo imido complexes.
- Han, Sheng,Cheng, Ying,Liu, Shanshan,Tao, Chaofu,Wang, Aiping,Wei, Wanguo,Yu, Han,Wei, Yongge
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supporting information
p. 6382 - 6385
(2021/02/09)
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- The polyhedral nature of selenium-catalysed reactions: Se(iv) species instead of Se(vi) species make the difference in the on water selenium-mediated oxidation of arylamines
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Selenium-catalysed oxidations are highly sought after in organic synthesis and biology. Herein, we report our studies on the on water selenium mediated oxidation of anilines. In the presence of diphenyl diselenide or benzeneseleninic acid, anilines react with hydrogen peroxide, providing direct and selective access to nitroarenes. On the other hand, the use of selenium dioxide or sodium selenite leads to azoxyarenes. Careful mechanistic analysis and 77Se NMR studies revealed that only Se(iv) species, such as benzeneperoxyseleninic acid, are the active oxidants involved in the catalytic cycle operating in water and leading to nitroarenes. While other selenium-catalysed oxidations occurring in organic solvents have been recently demonstrated to proceed through Se(vi) key intermediates, the on water oxidation of anilines to nitroarenes does not. These findings shed new light on the multifaceted nature of organoselenium-catalysed transformations and open new directions to exploit selenium-based catalysis.
- Capperucci, Antonella,Dalia, Camilla,Tanini, Damiano
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supporting information
p. 5680 - 5686
(2021/08/16)
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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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- Ru single atoms for efficient chemoselective hydrogenation of nitrobenzene to azoxybenzene
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Selectivity control of nitrobenzene hydrogenation remains a great challenge, and it is desirable to develop a green and highly efficient catalytic route toward value-added metastable intermediate products. Herein, we reported that isolated Ru single atoms coordinated with oxygen atoms in CeO2(Ru-SAs/CeO2) can achieve chemoselective hydrogenation of nitrobenzene to azoxybenzene with a selectivity of 88.2% in a continuous flow reactor using H2without using any bases or expensive organic reducing agents, while 82.7% aniline selectivity was obtained by Ru nanoparticles. We demonstrated that the unique coordinated structure between Ru single atoms and O atoms preferentially controls the reaction route toward the coupling of nitrosobenzene and phenylhydroxylamine intermediates to form azoxybenzene while greatly suppressing over-hydrogenation. The present work provides an efficient strategy to regulate the reaction pathway of nitrobenzene hydrogenation with a green and industry-friendly process by designing highly dispersed Ru single atoms.
- Huang, Min,Jiang, Zheng,Li, Ji,Lin, Tiejun,Song, Fei,Sun, Fanfei,Sun, Yuhan,Wu, Bo,Yang, Ruoou,Zhang, Huan,Zhong, Liangshu
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supporting information
p. 4753 - 4761
(2021/07/12)
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- Yeast supported gold nanoparticles: an efficient catalyst for the synthesis of commercially important aryl amines
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Candida parapsilosisATCC 7330 supported gold nanoparticles (CpGNP), prepared by a simple and green method can selectively reduce nitroarenes and substituted nitroarenes with different functional groups like halides (-F, -Cl, -Br), olefins, esters and nitriles using sodium borohydride. The product aryl amines which are useful for the preparation of pharmaceuticals, polymers and agrochemicals were obtained in good yields (up to >95%) using CpGNP catalyst under mild conditions. The catalyst showed high recyclability (≥10 cycles) and is a robust free flowing powder, stored and used after eight months without any loss in catalytic activity.
- Krishnan, Saravanan,Patel, Paresh N.,Balasubramanian, Kalpattu K.,Chadha, Anju
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supporting information
p. 1915 - 1923
(2021/02/06)
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- NaI/PPh3-Mediated Photochemical Reduction and Amination of Nitroarenes
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A mild transition-metal- and photosensitizer-free photoredox system based on the combination of NaI and PPh3 was found to enable highly selective reduction of nitroarenes. This protocol tolerates a broad range of reducible functional groups such as halogen (Cl, Br, and even I), aldehyde, ketone, carboxyl, and cyano. Moreover, the photoredox catalysis with NaI and stoichiometric PPh3 provides also an alternative entry to Cadogan-type reductive amination when o-nitrobiarenes were used.
- Qu, Zhonghua,Chen, Xing,Zhong, Shuai,Deng, Guo-Jun,Huang, Huawen
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supporting information
p. 5349 - 5353
(2021/07/21)
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- Rhodium-terpyridine Catalyzed Transfer Hydrogenation of Aromatic Nitro Compounds in Water
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A rhodium terpyridine complex catalyzed transfer hydrogenation of nitroarenes to anilines with i-PrOH as hydrogen source and water as solvent has been developed. The catalytic system can work at a substrate/catalyst (S/C) ratio of 2000, with a turnover frequency (TOF) up to 3360 h?1, which represents one of the most active catalytic transfer hydrogenation systems for nitroarene reduction. The catalytic system is operationally simple and the protocol could be scaled up to 20 gram scale. The water-soluble catalyst bearing a carboxyl group could be recycled 15 times without significant loss of activity.
- Liu, Yuxuan,Miao, Wang,Tang, Weijun,Xue, Dong,Xiao, Jianliang,Wang, Chao,Li, Changzhi
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supporting information
p. 1725 - 1729
(2021/06/01)
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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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- 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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- Supported CuII Single-Ion Catalyst for Total Carbon Utilization of C2 and C3 Biomass-Based Platform Molecules in the N-Formylation of Amines
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The shift from fossil carbon sources to renewable ones is vital for developing sustainable chemical processes to produce valuable chemicals. In this work, value-added formamides were synthesized in good yields by the reaction of amines with C2 and C3 biomass-based platform molecules such as glycolic acid, 1,3-dihydroxyacetone and glyceraldehyde. These feedstocks were selectively converted by catalysts based on Cu-containing zeolite 5A through the in situ formation of carbonyl-containing intermediates. To the best of our knowledge, this is the first example in which all the carbon atoms in biomass-based feedstocks could be amidated to produce formamide. Combined catalyst characterization results revealed preferably single CuII sites on the surface of Cu/5A, some of which form small clusters, but without direct linking via oxygen bridges. By combining the results of electron paramagnetic resonance (EPR) spin-trapping, operando attenuated total reflection (ATR) IR spectroscopy and control experiments, it was found that the formation of formamides might involve a HCOOH-like intermediate and .NHPh radicals, in which the selective formation of .OOH radicals might play a key role.
- Brückner, Angelika,Dai, Xingchao,Kreyenschulte, Carsten,Rabeah, Jabor,Shi, Feng,Wang, Xinzhi
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p. 16889 - 16895
(2021/09/25)
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- Gold(I)-Catalyzed Oxidative 1,4-Additions of 3-En-1-ynamide with Nitrones via Carbon- versus Nitrogen-Addition Chemoselectivity
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This work reports gold-catalyzed 1,4-oxofunctionalizations of 3-en-1-ynamides with nitrones, yielding two distinct E-configured products. We obtained 1,4-oxoarylation products from 3-en-1-ynamides bearing C(4)-electron-donating substituents and 1,4-oxoamination products from those analogues bearing C(4)-aryl substituents. We propose that if vinylgold carbenes are stable, imines undergo a para-arylation on these gold carbenes. If vinylgold carbenes are highly electron-deficient, this N-attack is irreversible to enable 1,4-oxoaminations.
- Tanpure, Sudhakar Dattatray,Kale, Balaji S.,Liu, Rai-Shung
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supporting information
p. 1394 - 1399
(2021/02/20)
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- Selective Reduction of Nitroarenes to Arylamines by the Cooperative Action of Methylhydrazine and a Tris(N-heterocyclic thioamidate) Cobalt(III) Complex
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We report an efficient catalytic protocol that chemoselectively reduces nitroarenes to arylamines, by using methylhydrazine as a reducing agent in combination with the easily synthesized and robust catalyst tris(N-heterocyclic thioamidate) Co(III) complex [Co(κS,N-tfmp2S)3], tfmp2S = 4-(trifluoromethyl)-pyrimidine-2-thiolate. A series of arylamines and heterocyclic amines were formed in excellent yields and chemoselectivity. High conversion yields of nitroarenes into the corresponding amines were observed by using polar protic solvents, such as MeOH and iPrOH. Among several hydrogen donors that were examined, methylhydrazine demonstrated the best performance. Preliminary mechanistic investigations, supported by UV-vis and NMR spectroscopy, cyclic voltammetry, and high-resolution mass spectrometry, suggest a cooperative action of methylhydrazine and [Co(κS,N-tfmp2S)3] via a coordination activation pathway that leads to the formation of a reduced cobalt species, responsible for the catalytic transformation. In general, the corresponding N-arylhydroxylamines were identified as the sole intermediates. Nevertheless, the corresponding nitrosoarenes can also be formed as intermediates, which, however, are rapidly transformed into the desired arylamines in the presence of methylhydrazine through a noncatalytic path. On the basis of the observed high chemoselectivity and yields, and the fast and clean reaction processes, the present catalytic system [Co(κS,N-tfmp2S)3]/MeNHNH2 shows promise for the efficient synthesis of aromatic amines that could find various industrial applications.
- Ioannou, Dimitris I.,Gioftsidou, Dimitra K.,Tsina, Vasiliki E.,Kallitsakis, Michael G.,Hatzidimitriou, Antonios G.,Terzidis, Michael A.,Angaridis, Panagiotis A.,Lykakis, Ioannis N.
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p. 2895 - 2906
(2021/02/27)
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- Photocatalytic oxidative coupling of arylamines for the synthesis of azoaromatics and the role of O2 in the mechanism
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The photocatalytic oxidative coupling of aryl amines to selectively synthesize azoaromatic compounds has been realized. Multiple different photocatalysts can be used to perform the general reaction; however, Ir(dF-CF3-ppy)2(dtbpy)+, where dF-CF3-ppy is 2-(2,4-difluorophenyl)-5-(trifluoromethyl)-pyridine and dtpby is 4,4′-tert-butyl-2,2′-bipyridine, showed the greatest range of reactivity with various amine substrates. Both electron-rich and -deficient amines can be coupled with yields up to 95% under an ambient air atmosphere. Oxygen was deemed to be essential for the reaction and is utilized in the regeneration of the photocatalyst. Fluorescence quenching and radical trap experiments indicate an amine radical coupling mechanism that proceeds through a hydrazoaromatic intermediate before further oxidation occurs to form the desired azoaromatic products.
- Sitter, James D.,Vannucci, Aaron K.
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supporting information
p. 2938 - 2943
(2021/03/01)
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- Organic Electrochemistry: Expanding the Scope of Paired Reactions
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Paired electrochemical reactions allow the optimization of both atom and energy economy of oxidation and reduction reactions. While many paired electrochemical reactions take advantage of perfectly matched reactions at the anode and cathode, this matching of substrates is not necessary. In constant current electrolysis, the potential at both electrodes adjusts to the substrates in solution. In principle, any oxidation reaction can be paired with any reduction reaction. Various oxidation reactions conducted on the anodic side of the electrolysis were paired with the generation and use of hydrogen gas at the cathode, showing the generality of the anodic process in a paired electrolysis and how the auxiliary reaction required for the oxidation could be used to generate a substrate for a non-electrolysis reaction. This is combined with variations on the cathodic side of the electrolysis to complete the picture and illustrate how oxidation and reduction reactions can be combined.
- Moeller, Kevin D.,Wu, Tiandi
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supporting information
p. 12883 - 12890
(2021/05/07)
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- Development of a [2 + 2]-Nitroso/Alkene Cycloaddition Using Sodium Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate Catalyst: Controlled Chemoselectivity of Two Equilibrating Isomeric Intermediates
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Sodium tetrakis[3,5-bis(trifluoromethyl)-phenyl]borate (NaBArF) catalyzes the [2 + 2] cycloaddition of 1,4-disubstituted cyclopenta-1,3-dien-2-yl esters with nitrsobenzene in toluene, affording two isolable regioisomers of 6-oxa-7-azabicyclo[3.2.0] heptanes, which thermally rearrange into the same 4-aminocyclopent-1-en-3-ones. In the case of 4-substituted cyclopenta-1,3-dien-2-yl esters, their initial [2 + 2] cycloaddition intermediates undergo a rapid ring expansion to afford six-membered piperidone derivatives efficiently.
- Chen, Jia-Xuan,Jadhav, Prakash D.,Chen, Ching-Nung,Liu, Rai-Shung
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p. 6246 - 6251
(2021/08/30)
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- Modified mesoporous y zeolite catalyzed nitration of azobenzene using NO2as the nitro source combined with density functional theory studies
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A modified mesoporous Y zeolite is developed to catalyze high ortho regioselective nitration of azobenzene with NO2 as the nitro source. The mesoporous Y zeolite is modified by the ion exchange method and characterized by various analyses involving FT-IR spectroscopy, and XPS and BET analyses. The ortho/para ratio of mononitration products is improved from 0.70 to 2.39 in the presence of the catalyst. Based on density functional theory (DFT), the active sites of nitration reaction are calculated by combining the electrostatic potential with the average local ionization energy, which are further support the electrophilic substitution mechanism of azobenzene in the catalytic nitration reaction. This journal is
- Chen, Lei,Guo, Chuanzhou,Guo, Jiaming,Peng, Xinhua
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p. 21389 - 21394
(2021/12/04)
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- Efficient chemoselective hydrogenation of nitrobenzene to aniline, azoxybenzene and azobenzene over CQDs/ZnIn2S4 nanocomposites under visible light
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Efficient production of amino-, azo- and azoxy- aromatics is important in chemical industries. In this manuscript, we reported that controllable chemoselective hydrogenation of nitrobenzene to produce aniline, azoxybenzene and azobenzene was realized over CQDs/ZnIn2S4 nanocomposite under visible light via simply regulating the reaction medium including the alkalinity and the hydrogen source. An optimized production of aniline was obtained over 3.0 wt% CQDs/ZnIn2S4 nanocomposite in a reaction medium of TEOA: MeOH (1:1), while a strong alkaline reaction medium promote N-N coupling to produce azoxybenzene and azobenzene. In addition, azoxybenzne is the intermediate to form azobenzene during the hydrogenation of nitrobenzene, in which a strong hydrogen source like TEOA is indispensable for the transformation. This study not only demonstrated a noble metal-free photocatalytic system for visible light induced efficient and controllable chemoselective hydrogenation of nitrobenzene to produce aniline, azobenzene and azoxybenzene, but also highlights the great potential of photocatalysis in organic syntheses.
- Deng, Zirong,Li, Zhaohui,Wang, Bingqing
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p. 241 - 246
(2020/06/27)
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- Clean production process of hydrogenated azobenzene
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The invention discloses a clean production process of hydrogenated azobenzene, which comprises the following steps: 1) reducing nitrobenzene with hydrazine hydrate in an alkaline solution in the presence of polyethylene glycol by using a quinone compound as a catalyst to obtain azoxybenzene; and 2) reducing the azoxybenzene obtained in the step 1) with hydrazine hydrate in an alkaline solution inthe presence of polyethylene glycol by using Raney nickel as a catalyst to obtain the hydrogenated azoxybenzene. The clean production process of the hydrogenated azobenzene disclosed by the inventionis free of solid waste pollution, the alkali liquor can be repeatedly used, the alkali consumption can be greatly saved, and potential risks such as high temperature, high pressure, flammability, explosiveness and the like are avoided.
- -
-
Paragraph 0031-0033; 0035-0038; 0040-0043; 0045
(2020/11/22)
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- Green and highly efficient approach for the reductive coupling of nitroarenes to azoxyarenes using the new mesoporous Fe3O4@SiO2@Co–Zr–Sb catalyst
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Efficient, green, simple and environmentally friendly approach for the straightforward reductive coupling of nitroarenes to the corresponding azoxyarenes has been developed in the presence of Fe3O4@SiO2@Co–Zr–Sb as a novel recyclable nanocatalyst. The Co–Zr–Sb trimetallic nanoparticles immobilized on silica-layered magnetite have been prepared by the co-precipitation method. The mesoporous catalyst has been characterized by FT-IR, SEM, EDX, VSM, TEM and XRD analyses. The chemoselective hydrogenation of nitrobenzenes was carried out successfully in refluxing water to afford the corresponding azoxybenzenes within 2–10?min in good to high yields. The reusability of the heterogeneous nanocatalyst has also been studied using the FT-IR and SEM analyses. The catalyst was utilized four times in sequential runs without significant loss of activity. The current research includes remarkable advantages of short reaction times, absence of hazardous organic solvents, mild reaction conditions, high yields, using water as a green solvent and the ability to utilize the recyclable nanomagnetic catalyst.
- Zeynizadeh, Behzad,Gilanizadeh, Masumeh
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p. 2969 - 2984
(2020/04/10)
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- Palladium Nanoparticles on Silica Nanospheres for Switchable Reductive Coupling of Nitroarenes
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Abstract: In this study, we synthesized a robust and sustainable Pd/SiO2 nanospheres catalyst. Further, its catalytic activity was demonstrated for the direct reductive coupling of nitroarenes under mild conditions. While the reaction with Pd nanoparticles on other supporting materials such as modified carbon materials and TiO2, under similar conditions, resulted formation of amines exclusively. Therefore, it was confirmed that the SiO2 was found to be the best supporting material towards the selective reductive coupling of nitroarenes. Also, the catalyst could be recycled up to five cycles with a marginal loss of product yield ( 2% yield). Graphic Abstract: [Figure not available: see fulltext.].
- Lakshminarayana, Bhairi,Manna, Arun Kumar,Satyanarayana,Subrahmanyam, Ch.
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p. 2309 - 2321
(2020/02/18)
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- Room temperature selective reduction of nitroarenes to azoxy compounds over Ni-TiO2 catalyst
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Surface tuned Ni-TiO2 catalyst was prepared by hydro-solvothermal method using poly(diallyldimethylammonium chloride) (or PDADMAC) as a surfactant and hydrazine hydrate as a capping agent. Activity of catalyst was investigated for selective reduction of nitrobenzene to azoxybenzene in aqueous medium at room temperature, using hydrazine hydrate as the reducing agent for catalysis. It was observed that the catalyst prepared by hydro-solvothermal method (2.6 % Ni-TiO2EG?W?H) showed 92 % selectivity of azoxybenzene with 89 % conversion of nitrobenzene, under mild reaction conditions, which is quite higher as compared to reported non-noble metal catalysts. Prepared catalysts were thoroughly characterized by various analytical techniques to find out the physicochemical characteristic features of the materials. 2.6 % Ni-TiO2EG-W catalyst exhibited highly dispersed nickel nanoparticles (～6.8 nm) over TiO2 surface and strong metal-support interaction due to smaller size of Ni-particles, which significantly enhanced the catalytic efficiency towards selective reduction of nitroarenes to azoxy compounds. Effect of solvents on catalyst synthesis process was also investigated and reported for establishing the superiority of 2.6 % Ni-TiO2EG-W catalyst. The heterogeneous nature of highly dispersed catalyst (2.6 % Ni-TiO2EG-W) was confirmed by the recyclability tests and found that the catalyst particles can be easily recovered and recycled up to four successive runs without any significant loss in its catalytic performance.
- Adak, Shubhadeep,Bal, Rajaram,Bhandari, Sonu,Bordoloi, Ankur,Prasad, V. V. D. N.,Sasaki, Takehiko,Shukla, Astha,Singha, Rajib Kumar
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- Shape-dependent reactivity and chemoselectivity of nanogold towards nitrophenol reduction in water
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Although the catalytic activity of nano-gold surfaces for the reduction of nitro compounds has been known, the effect of their shape has been rarely evaluated. Here, the synthesis, characterization, and application of both gold nanoworms (GNW) and gold nanospheres (GNS) are described. Both GNW and GNS were characterized using SEM, TEM, UV–Vis, FTIR, and XPS spectroscopy. The catalytic efficiency of GNW with an average dimensions of 2 × 250 nm (D × L) towards the hydrogenation of nitrophenol, a pollutant present in industrial wastewater, is higher (TOF 3675 h?1) than that of spherical GNS (10 ± 1 nm), for which TOF is 1838 h?1 in water using NaBH4 as the reductant. The selectivity of 4-aminophenol is 100% for both GNS and GNW.
- Aziz, Md Abdul,Nafiu, Sodiq Adeyeye,Shaikh, M. Nasiruzzaman
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- Preparation of azoxy benzene (by machine translation)
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[A] good workability and safety, cost, and, efficient production of the azoxy benzene azoxy benzene can be produced. [Solution] nitrobenzene ones, having the photocatalytic function with a dye, a reducing agent such as a fluorine resin or a transparent resin material is a mixed solution of 1 mm in diameter are inserted into the tube 4 does not inhibit the reaction, 4 LED lamp 5 emits visible from the outside of the tube moves within the tube 4 is provided with visible light within the tube 4 by a photocatalyst reaction mixed solution so as to obtain azoxy benzene compounds. Figure 2 [drawing] (by machine translation)
- -
-
Paragraph 0029; 0043; 0045
(2020/05/21)
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- Tuneable Copper Catalysed Transfer Hydrogenation of Nitrobenzenes to Aniline or Azo Derivatives
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A highly versatile and flexible copper nanoparticle (Cu(0) NPs) catalytic system has been developed for the controlled and selective transfer hydrogenation of nitroarene. Interestingly, the final catalytic product is strongly dependent on the nature of the hydrogen donor source. The yield of nitrobenzene reduction to aniline increased from 20% to an almost quantitative yield over a range of alcohols, diols and aminoalcohols. In glycerol at 130 °C aniline was isolated in 93% yield. In ethanolamine, the reaction was conveniently performed at a lower temperature (55 °C) and gave selectively substituted azobenzene (92% yield). Experimental studies provide support for a reaction pathway in which the Cu(0) NPs catalysed transfer hydrogenation of nitrobenzene to aniline proceeds via the condensation route. The high chemoselectivity of both protocols has been proved in experiments on a panel of variously substituted nitroarenes. Enabling technologies, microwaves and ultrasound, used both separately and in combination, have successfully increased the reaction rate and reaction yield. (Figure presented.).
- Moran, Maria Jesus,Martina, Katia,Baricco, Francesca,Tagliapietra, Silvia,Manzoli, Maela,Cravotto, Giancarlo
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p. 2689 - 2700
(2020/05/18)
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- Selective Photoinduced Reduction of Nitroarenes to N-Arylhydroxylamines
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We report the selective photoinduced reduction of nitroarenes to N-arylhydroxylamines. The present methodology facilitates this transformation in the absence of catalyst or additives and uses only light and methylhydrazine. This noncatalytic photoinduced transformation proceeds with a broad scope, excellent functional-group tolerance, and high yields. The potential of this protocol reflects on the selective and straightforward conversion of two general antibiotics, azomycin and chloramphenicol, to the bioactive hydroxylamine species.
- Kallitsakis, Michael G.,Ioannou, Dimitris I.,Terzidis, Michael A.,Kostakis, George E.,Lykakis, Ioannis N.
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supporting information
p. 4339 - 4343
(2020/06/08)
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- Efficient and Selective Oxidation of Aromatic Amines to Azoxy Derivatives over Aluminium and Gallium Oxide Catalysts with Nanorod Morphology
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Aluminium oxide and gallium oxide nanorods were identified as highly efficient heterogeneous catalysts for the selective oxidation of aromatic amines to azoxy compounds using hydrogen peroxide as environmentally friendly oxidant. This is the first report of the selective oxidation of aromatic amines to their azoxy derivatives without using transition metal catalysts. Among the tested transition-metal-free oxides, gallium oxide nanorods with small dimensions (9–52 nm length and 3–5 nm width) and fully accessible, high surface area (225 m2 g?1) displayed the best catalytic performance in terms of substrate versatility, activity and azoxybenzene selectivity. Furthermore, the catalyst loading, hydrogen peroxide type (aqueous or anhydrous), and the amount of solvent were tuned to optimise the catalytic performance, which allowed reaching almost full selectivity (98 %) towards azoxybenzene at high aniline conversion (94 %). Reusability tests showed that the gallium oxide nanorod catalyst can be recycled in consecutive runs with complete retention of the original activity and selectivity.
- Singh, Bhawan,Mandelli, Dalmo,Pescarmona, Paolo P.
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p. 593 - 601
(2019/11/13)
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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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- MOF-Derived Cu-Nanoparticle Embedded in Porous Carbon for the Efficient Hydrogenation of Nitroaromatic Compounds
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Abstract: Novel Cu-nanoparticles (NPs) embedded in porous carbon materials (Cu@C-x) were prepared by one-pot pyrolysis of metal–organic frameworks (MOF) HKUST-1 at different temperatures. The obtained material Cu@C-x was used as a cost-effective catalyst for the hydrogenation of nitrobenzene using NaBH4 as the reducing agent under mild reaction conditions. By considering the catalyst preparation and the catalytic activity, a pyrolysis temperature of 400?°C was finally chosen to synthesize the optimal catalyst. When the aromatic nitro compounds with reducible groups, such as cyano, halogen, and alkyl groups, were tested in this catalytic hydrogenation, an excellent selectivity approaching 100% was achieved. In the recycling experiment, a significant decrease in nitrobenzene conversion was observed in the third cycle, mainly due to the very small amount of catalyst employed in the reaction. Hence, the easily prepared and cost-effective Cu@C-400 catalyst fabricated in this study demonstrates potential for the applications in selective reduction of aromatic nitro compounds. Graphic Abstract: The catalyst Cu@C-400 exhibited 100?% conversion and high selectivity for the hydrogenation of industrially relevant nitroarenes.[Figure not available: see fulltext.].
- Qiao, Chenxia,Jia, Wenlan,Zhong, Qiming,Liu, Bingyu,Zhang, Yifu,Meng, Changgong,Tian, Fuping
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p. 3394 - 3401
(2020/05/19)
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- Intermetallic Nanocatalysts from Heterobimetallic Group 10-14 Pyridine-2-thiolate Precursors
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Intermetallic compounds are atomically ordered inorganic materials containing two or more transition metals and main-group elements in unique crystal structures. Intermetallics based on group 10 and group 14 metals have shown enhanced activity, selectivity, and durability in comparison to simple metals and alloys in many catalytic reactions. While high-temperature solid-state methods to prepare intermetallic compounds exist, softer synthetic methods can provide key advantages, such as enabling the preparation of metastable phases or of smaller particles with increased surface areas for catalysis. Here, we study a generalized family of heterobimetallic precursors to binary intermetallics, each containing a group 10 metal and a group 14 tetrel bonded together and supported by pincer-like pyridine-2-thiolate ligands. Upon thermal decomposition, these heterobimetallic complexes form 10-14 binary intermetallic nanocrystals. Experiments and density functional theory (DFT) computations help in better understanding the reactivity of these precursors toward the synthesis of specific intermetallic binary phases. Using Pd2Sn as an example, we demonstrate that nanoparticles made in this way can act as uniquely selective catalysts for the reduction of nitroarenes to azoxyarenes, which highlights the utility of the intermetallics made by our method. Employing heterobimetallic pincer complexes as precursors toward binary nanocrystals and other metal-rich intermetallics provides opportunities to explore the fundamental chemistry and applications of these materials.
- Adamson, Marquix A. S.,Chen, Yunhua,Daniels, Carena L.,Dorn, Rick W.,Fan, Huajun,Knobeloch, Megan,Rossini, Aaron J.,Vela, Javier,Wu, Hao,Yox, Philip,Zhou, Guoquan
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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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- 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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- EffectiveN-methylation of nitroarenes with methanol catalyzed by a functionalized NHC-based iridium catalyst: a green approach toN-methyl amines
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Compound [IrBr(CO)2(κC-tBuImCH2PyCH2OMe)] featuring a flexible pyridine/OMe functionalized NHC ligand κ1C coordinated efficiently catalyzes the selectiveN-monomethylation of nitroarenes using methanol as both the reducing agent and the C1 source. A range of functionalized nitroarenes including heterocyclic or sterically hindered derivatives have been efficiently converted to the correspondingN-monomethyl amines in good yields at low catalyst loadings using sub-stoichiometric amounts of Cs2CO3as a base. Mechanistic investigations support a borrowing-hydrogen mechanism in which methanol acts as the hydrogen source and methylating agent. Further, the hydrogen transfer reduction of nitrobenzene to aniline under optimized reaction conditions should proceed through a direct mechanism involving nitrosobenzene andN-phenylhydroxylamine intermediates.
- González-Lainez, Miguel,Jiménez, M. Victoria,Passarelli, Vincenzo,Pérez-Torrente, Jesús J.
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p. 3458 - 3467
(2020/06/17)
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- One-pot imine synthesis from methylarenes and anilines under air over heterogeneous Cu oxide-modified CeO2catalyst
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Cu oxide-modified CeO2 (CuOx-CeO2) with 2 wtpercent Cu loading amount was the most effective and reusable heterogeneous catalyst for selective one-pot imine synthesis from methylarenes and anilines via direct oxidation of the sp3 C-H bond in the methylare
- Tamura, Masazumi,Li, Yingai,Tomishige, Keiichi
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supporting information
p. 7337 - 7340
(2020/07/23)
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- Nanocomposite-based inorganic-organocatalyst Cu(II) complex and SiO2- and Fe3O4 nanoparticles as low-cost and efficient catalysts for aniline and 2-aminopyridine oxidation
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Bis-imino Cu(II) complex (CuLAn2), in which the imine ligand (HLAn) acts as a bidentate chelating ligand, was synthesized. The catalytic potential of the inorganic-organocatalyst was studied homogeneously and heterogeneously in the oxidation of aniline and 2-aminopyridine by H2O2 or tBuOOH. Two heterogeneous inorganic-organocatalysts, CuLAn2@Fe3O4 and CuLAn2@SiO2@Fe3O4, were synthesized by the successful immobilization of CuLAn2 on the Fe3O4 surface and the composited Fe3O4 with SiO2, respectively. The heterogeneous structure of those inorganic-organocatalysts was confirmed using Fourier-transform infrared, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, and magnetic properties. The adsorption–desorption isotherms revealed respectable adsorption parameters (SBET, Vp, and rp). All catalysts exhibited high potential in the oxidation of aniline (with phenylhydroxylamine as the main product) and good potential in the oxidation of 2-aminopyridine, in the first attempt (with 2-nitropyridine-N-oxide and 2-nitrosopyridine-N-oxide as main products), at room temperature. Acetonitrile was found to be the best solvent compared to ethanol, dimethyl sulfoxide, chloroform, and water. The homogeneous catalyst exhibited reusability for three times. The heterogeneous catalysts, CuLAn2@Fe3O4 and CuLAn2@SiO2@Fe3O4, were active for five and seven times, respectively. A mechanism was proposed within electron and oxygen transfer processes.
- Adam, Mohamed Shaker S.,Al-Omair, Mohammed A.
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- Nitrone/Imine Selectivity Switch in Base-Catalysed Reaction of Aryl Acetic Acid Esters with Nitrosoarenes: Joint Experimental and Computational Study
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Herein we report a mild and diastereoselective access to ketonitrones by reacting easily available aryl acetic acid esters and other active methylene compounds, with nitrosoarenes under catalytic loading of 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP) at room temperature. Depending on the substitution pattern and nature of the aryl moiety, a switch toward the formation of imines can be observed. The mechanistic framework is put to scrutiny by experimental and theoretical studies, pointing to the formation of a nitroso aldol intermediate, whose fate toward one of the competing pathways, namely hydride transfer or elimination, would depend upon the NOH/CHα relative acidities. (Figure presented.).
- Volpe, Chiara,Meninno, Sara,Roselli, Angelo,Mancinelli, Michele,Mazzanti, Andrea,Lattanzi, Alessandra
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supporting information
p. 5457 - 5466
(2020/10/12)
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- Modulating the catalytic behavior of non-noble metal nanoparticles by inter-particle interaction for chemoselective hydrogenation of nitroarenes into corresponding azoxy or azo compounds
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Aromatic azoxy compounds have wide applications and they can be prepared by stoichiometric or catalytic reactions with H2O2 or N2H4 starting from anilines or nitroarenes. In this work, we will present the direct chemoselective hydrogenation of nitroarenes with H2 to give aromatic azoxy compounds under base-free mild conditions, with a bifunctional catalytic system formed by Ni nanoparticles covered by a few layers of carbon (Ni@C NPs) and CeO2 nanoparticles. The catalytic performance of Ni@C-CeO2 catalyst surpasses the state-of-art Au/CeO2 catalyst for the direct production of azoxybenzene from nitrobenzene. By means of kinetic and spectroscopic results, a bifunctional mechanism is proposed in which, the hydrogenation of nitrobenzene can be stopped at the formation of azoxybenzene with >95% conversion and >93% selectivity, or can be further driven to the formation of azobenzene with >85% selectivity. By making a bifunctional catalyst with a non-noble metal, one can achieve chemoselective hydrogenation of nitroarenes not only to anilines, but also to corresponding azoxy and azo compounds.
- Liu, Lichen,Concepción, Patricia,Corma, Avelino
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p. 312 - 323
(2018/12/11)
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- Room temperature catalytic reduction of nitrobenzene to azoxybenzene over one pot synthesised reduced graphene oxide decorated with Ag/ZnO nanocomposite
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We report herein, a one-pot synthetic route for the synthesis of reduced graphene oxide decorated Ag/ZnO nanocomposite and studied its catalytic activity as simple, recyclable and efficient catalyst for one-pot conversion of nitrobenzene to azoxybenzene. It was observed that 5–10 nm Ag-nanoparticles supported on 40–60 nm ZnO nanorod decorated on reduced graphene oxide was formed with a silver loading of 1.6 wt%. The effect of different reaction parameters were investigated and studied in detail. A nitrobenzene conversion of 96% with 98% selectivity of azoxybenzene was achieved without the use of any external additives.
- Paul, Bappi,Vadivel,Yadav, Nishant,Dhar, Siddhartha Sankar
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- Au@zirconium-phosphonate nanoparticles as an effective catalytic system for the chemoselective and switchable reduction of nitroarenes
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In the present paper, a novel inorganic-organic layered material, a zirconium phosphate aminoethyl phosphonate, ZP(AEP), bearing aminoethyl groups on the layer surface, was used to immobilize AuNPs by a two-step procedure. The gold-based catalyst, Au1@ZP(AEP), containing 1 wt% Au, was characterized in terms of physico-chemical properties and TEM analysis revealed that the AuNPs have a spherical shape and an average size of 7.8 (±2.4) nm. Au1@ZP(AEP) proved its high efficiency for the chemoselective reduction of nitroarenes under mild conditions. Both batch and flow condition protocols have been defined. The catalytic system has been proven to be able to easily switch chemoselectivity allowing the control of the reduction of a series of nitroaromatics towards their corresponding azoxyarenes (2a-k) or anilines (2a-l) in 96% EtOH or abs EtOH, respectively, by using NaBH4 as a reducing agent, in good to excellent yields. Recovery and reuse of the catalytic system has been investigated proving the benefits of the flow approach.
- Ferlin, Francesco,Cappelletti, Matteo,Vivani, Riccardo,Pica, Monica,Piermatti, Oriana,Vaccaro, Luigi
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supporting information
p. 614 - 626
(2019/02/13)
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- Environment-friendly method used for preparing azoxy compound taking MOFs derivative magnetic nanometer particles as recoverable catalyst
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The invention discloses an environment-friendly method used for preparing an azoxy compound taking MOFs derivative magnetic nanometer particles as a recoverable catalyst. The characteristics of the method are that: an aromatic nitro compound and a reducing agent are subjected to oxidation reduction reaction under the effect of a Co-containing magnetic nanometer catalyst so as to obtain an azoxybenzene compound; Co@C-N is taken as a catalyst, an aromatic hydrocarbon nitro compound is taken as a raw material, hydrazine hydrate is taking a reducing agent, and the azoxybenzene compound is obtainedthrough synthesis in an alcohol solution. The magnetic catalyst adopted in the reaction can be recycled, production cost is reduced, the method is friendly to the environment, reaction conditions aresimple, and yield is high.
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Paragraph 0020; 0022; 0023
(2019/07/04)
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- Highly Selective and Solvent-Dependent Reduction of Nitrobenzene to N-Phenylhydroxylamine, Azoxybenzene, and Aniline Catalyzed by Phosphino-Modified Polymer Immobilized Ionic Liquid-Stabilized AuNPs
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Gold nanoparticles stabilized by phosphine-decorated polymer immobilized ionic liquids (AuNP@PPh2-PIILP) is an extremely efficient multiproduct selective catalyst for the sodium borohydride-mediated reduction of nitrobenzene giving N-phenylhydroxylamine, azoxybenzene, or aniline as the sole product under mild conditions and a very low catalyst loading. The use of a single nanoparticle-based catalyst for the partial and complete reduction of nitroarenes to afford three different products with exceptionally high selectivities is unprecedented. Under optimum conditions, thermodynamically unfavorable N-phenylhydroxylamine can be obtained as the sole product in near quantitative yield in water, whereas a change in reaction solvent to ethanol results in a dramatic switch in selectivity to afford azoxybenzene. The key to obtaining such a high selectivity for N-phenylhydroxylamine is the use of a nitrogen atmosphere at room temperature as reactions conducted under an inert atmosphere occur via the direct pathway and are essentially irreversible, while reactions in air afford significant amounts of azoxy-based products by virtue of competing condensation due to reversible formation of N-phenylhydroxylamine. Ultimately, aniline can also be obtained quantitatively and selectively by adjusting the reaction temperature and time accordingly. Introduction of PEG onto the polyionic liquid resulted in a dramatic improvement in catalyst efficiency such that N-phenylhydroxylamine could be obtained with a turnover number (TON) of 100000 (turnover frequency (TOF) of 73000 h-1, with >99% selectivity), azoxybenzene with a TON of 55000 (TOF of 37000 h-1 with 100% selectivity), and aniline with a TON of 500000 (TOF of 62500 h-1, with 100% selectivity). As the combination of ionic liquid and phosphine is required to achieve high activity and selectivity, further studies are currently underway to explore whether interfacial electronic effects influence adsorption and thereby selectivity and whether channeling of the substrate by the electrostatic potential around the AuNPs is responsible for the high activity. This is the first report of a AuNP-based system that can selectively reduce nitroarenes to either of two synthetically important intermediates as well as aniline and, in this regard, is an exciting discovery that will form the basis to develop a continuous flow process enabling facile scale-up.
- Doherty, Simon,Knight, Julian G.,Backhouse, Tom,Summers, Ryan J.,Abood, Einas,Simpson, William,Paget, William,Bourne, Richard A.,Chamberlain, Thomas W.,Stones, Rebecca,Lovelock, Kevin R. J.,Seymour, Jake M.,Isaacs, Mark A.,Hardacre, Christopher,Daly, Helen,Rees, Nicholas H.
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p. 4777 - 4791
(2019/05/17)
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