21650-55-5Relevant academic research and scientific papers
Bifunctional Cs?Au/Co3O4 (Basic and Redox)-Catalyzed Oxidative Synthesis of Aromatic Azo Compounds from Anilines
Akinnawo, Christianah Aarinola,Alimi, Oyekunle Azeez,Fapojuwo, Dele Peter,Meijboom, Reinout,Mogudi, Batsile M.,Onisuru, Oluwatayo Racheal,Oseghale, Charles O.
supporting information, p. 5063 - 5073 (2021/09/30)
An eco-friendly alkali-promoted (Cs?Au/Co3O4) catalyst, with redox and basic properties for the oxidative dehydrogenative coupling of anilines to symmetrical and unsymmetrical aromatic azo compounds, was developed. We realized a base additive- and molecular O2 oxidant-free process (using air), with reasonable reusability of the catalyst achieved under milder reaction conditions. Notably, the enhanced catalytic activity was also linked to the increased basic site concentration, low reduction temperatures, and the effect of lattice oxygen on the nanomaterials. The increased basic strength of the cation-promoted catalyst improved the electron density of the active Au species, resulting in higher yields of the desired aromatic azo compounds.
Selective Oxidation of Anilines to Azobenzenes and Azoxybenzenes by a Molecular Mo Oxide Catalyst
Han, Sheng,Cheng, Ying,Liu, Shanshan,Tao, Chaofu,Wang, Aiping,Wei, Wanguo,Yu, Han,Wei, Yongge
supporting information, p. 6382 - 6385 (2021/02/09)
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.
Electrosynthesis of Azobenzenes Directly from Nitrobenzenes
Ma, Yanfeng,Wu, Shanghui,Jiang, Shuxin,Xiao, Fuhong,Deng, Guo-Jun
, p. 3334 - 3338 (2021/10/29)
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.
A Cu-BTC metal-organic framework (MOF) as an efficient heterogeneous catalyst for the aerobic oxidative synthesis of imines from primary amines under solvent free conditions
Venu, Boosa,Shirisha, Varimalla,Vishali, Bilakanti,Naresh, Gutta,Kishore, Ramineni,Sreedhar, Inkollu,Venugopal, Akula
supporting information, p. 5972 - 5979 (2020/04/27)
A Cu-BTC (MOF-199) [copper(ii)-benzene-1,3,5-tricarboxylate] catalyst has been synthesized and evaluated for imine synthesis from amine compounds under neat conditions. The performance of the Cu-BTC MOF was significantly higher than that of the CuO supported on Al2O3, TiO2 and SiO2 catalysts. The role of surface Lewis acid sites on the catalyst in the formation of imine products was illustrated by the pyridine-IR studies. The recovered Cu-BTC catalyst demonstrated consistent activity for five cycles under similar experimental conditions. The physicochemical properties of the catalysts were analyzed by XRD, BET-SA, FT-IR, UV-DRS, SEM, TEM, XPS and pyridine adsorbed DRIFT spectroscopy.
Tuneable Copper Catalysed Transfer Hydrogenation of Nitrobenzenes to Aniline or Azo Derivatives
Moran, Maria Jesus,Martina, Katia,Baricco, Francesca,Tagliapietra, Silvia,Manzoli, Maela,Cravotto, Giancarlo
supporting information, p. 2689 - 2700 (2020/05/18)
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.).
Iron and Nitrogen Co-Doped Mesoporous Carbon-Based Heterogeneous Catalysts for Selective Reduction of Nitroarenes
Wang, Jitao,Yu, Xiaochun,Shi, Chongyang,Lin, Dajie,Li, Jun,Jin, Huile,Chen, Xian,Wang, Shun
supporting information, p. 3525 - 3531 (2019/06/24)
A facile fabrication of Fe and N co-doped mesoporous carbon (MC), as an efficient heterogeneous catalyst for the highly selective reduction of nitroarenes, is described. The Fe and N co-doped MC nanosheets are easily synthesized via a hydrothermal reaction between citrate acid and magnesium citrate, followed by calcination in the presence of melamine and potassium ferrocyanide. The Fe?N complex provides a unique active site for the selective reduction of 1-chloro-4-nitrobenzene, leading to the production of (E)-1,2-bis(4-chlorophenyl)diazene with a selectivity of >96%, in 40 mins. Control experiments based on non-doped, N-doped, and Fe-doped MC nanosheets demonstrate that selectivity greatly depends on the catalyst active component type, and that non-doped MC significantly contributes to the high efficiencies observed in the selective synthesis of azoxy compound intermediates. A broad range of substrates, including extra-functional groups on the nitroarenes rings, were successfully converted to the corresponding azo compounds at mild conditions with high selectivity. (Figure presented.).
Metal-free synthesis of pyridin-2-yl ureas from 2-aminopyridinium salts
Saroj,Patel, Om P.S.,Rangan, Krishnan,Kumar, Anil
supporting information, (2019/07/23)
An unprecedented base promoted domino approach has been developed for the synthesis of pyridin-2-yl urea derivatives via the reaction of 2-aminopyridinium salts and arylamines. The developed strategy tolerated a wide range of functional groups and afforded pyridin-2-yl ureas in moderate to good yields. The reaction was postulated to involve tandem cyclization, intermolecular nucleophilic addition, ring opening, and demethylation.
Hole Catalysis as a General Mechanism for Efficient and Wavelength-Independent Z → E Azobenzene Isomerization
Goulet-Hanssens, Alexis,Rietze, Clemens,Titov, Evgenii,Abdullahu, Leonora,Grubert, Lutz,Saalfrank, Peter,Hecht, Stefan
supporting information, p. 1740 - 1755 (2018/06/29)
Whereas the reversible reduction of azobenzenes has been known for decades, their oxidation is destructive and as a result has been notoriously overlooked. Here, we show that a chain reaction leading to quantitative Z → E isomerization can be initiated before reaching the destructive anodic peak potential. This hole-catalyzed pathway is accessible to all azobenzenes, without exception, and offers tremendous advantages over the recently reported reductive, radical-anionic pathway because it allows for convenient chemical initiation without the need for electrochemical setups and in the presence of air. In addition, catalytic amounts of metal-free sensitizers, such as methylene blue, can be used as excited-state electron acceptors, enabling a shift of the excitation wavelength to the far red of the azobenzene absorption (up to 660 nm) and providing quantum yields exceeding unity (up to 200%). Our approach will boost the efficiency and sensitivity of optically dense liquid-crystalline and solid photoswitchable materials. Video Abstract: [Figure presented] Molecular switches are a key ingredient in stimulus-responsive and adaptive materials and devices. Light is among the most attractive stimuli, yet photoswitches often require intense irradiation with high-energy UV light and suffer from inefficient switching as well as fatigue. Thus, the design of robust and efficient photoswitches constitutes an important challenge to boost the sensitivity and energy efficiency of the respective materials and devices. Here, we describe that the isomerization of azobenzene switches from their less stable Z isomer back to the more stable E isomer can be triggered by tiny, i.e., catalytic, amounts of holes caused by chemical, electrochemical, or photochemical oxidation. Our method is generally applicable to the entire family of azobenzene switches, does not require expensive equipment, and allows the reliable and efficient operation of these photoswitches by using red light with quantum efficiencies up to 200%. An efficient and generally applicable method is developed for operating azobenzene molecular switches by using catalytic amounts of holes (via an oxidant) or photons (via a photosensitizer). The pathway allows for indirect Z → E photoisomerization using lower-energy light than required for direct azobenzene excitation and with high quantum yields exceeding unity. The method should help to enhance the sensitivity of photoresponsive materials and devices with high optical density.
Preparation of carbon-based AuAg alloy nanoparticles by using the heterometallic [Au4Ag4] cluster for efficient oxidative coupling of anilines
Gao, Bin-Bin,Zhang, Min,Chen, Xu-Ran,Zhu, Da-Liang,Yu, Hong,Zhang, Wen-Hua,Lang, Jian-Ping
supporting information, p. 5780 - 5788 (2018/04/30)
We herein report the preparation of unique heteroatom-doped and carbon-based AuAg alloy nanoparticles (NPs) via the pyrolysis of a structurally defined octanuclear heterometallic Au(i)-Ag(i) cluster [Au4Ag4(Dppy)4(Tab)sub
A metal-catalyst-free oxidative coupling of anilines to aromatic azo compounds in water using bleach
de Souza, Gabriela F.P.,von Zuben, Theodora W.,Salles, Airton G.
supporting information, p. 3753 - 3755 (2018/09/21)
A simple route toward the synthesis of symmetrical and unsymmetrical aromatic azo compounds through oxidative coupling of anilines using widely available NaOCl is presented. This metal catalyst-free protocol is performed in water and affords the desired products in high yields.
