- Photochemical catalytic synthesis method of aromatic azo compound
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The invention belongs to the field of photochemical organic synthesis, and particularly relates to a photochemical catalytic synthesis method of an aromatic azo compound, which comprises the followingstep: in the presence of light, a photocatalyst, a cocatalyst, a ligand, an alkali and a hydrogen donor, carrying out a deoxidation coupling reaction on a nitro-substituted aromatic compound to obtain the aromatic azo compound. According to the reaction system, the nitro-substituted aromatic compound can be selectively deoxidized and coupled to obtain the aromatic azo compound, and the highest yield of the product can reach 85% or above.
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Paragraph 0059-0060
(2020/05/02)
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- Conversion of anilines into azobenzenes in acetic acid with perborate and Mo(VI): correlation of reactivities
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Azobenzenes are extensively used to dye textiles and leather and by tuning the substituent in the ring, vivid colours are obtained. Here, we report preparation of a large number of azobenzenes in good yield from commercially available anilines using sodium perborate (SPB) and catalytic amount of Na2MoO4 under mild conditions. Glacial acetic acid is the solvent of choice and the aniline to azobenzene conversion is zero, first and first orders with respect to SPB, Na2MoO4 and aniline, respectively. Based on the kinetic orders, UV–visible spectra and cyclic voltammograms, the conversion mechanism has been suggested. The reaction rates of about 50 anilines at 20–50?°C and their energy and entropy of activation conform to the isokinetic or Exner relationship and compensation effect, respectively. However, the reaction rates, deduced by the so far adopted method, fail to comply with the Hammett correlation. The specific reaction rates of molecular anilines, obtained through a modified calculation, conform to the Hammett relationship. Thus, this work presents a convenient inexpensive non-hazardous method of preparation of a larger number of azobenzenes, and shows the requirement of modification in obtaining the true reaction rates of anilines in acetic acid and the validity of Hammett relationship in the conversion process, indicating operation of a common mechanism.
- Karunakaran,Venkataramanan
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p. 375 - 385
(2019/02/14)
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- A Highly Efficient Near-Infrared-Emissive Copolymer with a N=N Double-Bond π-Conjugated System Based on a Fused Azobenzene–Boron Complex
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Fused azobenzene–boron complexes (BAzs) show highly efficient near-infrared (NIR) emission from the nitrogen–nitrogen double bond (N=N) containing π-conjugated copolymer. Optical measurements showed that BAz worked as a strong electron acceptor because of the intrinsic electron deficiency of the N=N double bond and the boron–nitrogen (B?N) coordination which dramatically lowered the energy of the lowest unoccupied molecular orbital (LUMO) of the azobenzene ligand. The simple donor–acceptor (D–A) type copolymer of bithiophene (BT) and BAz exhibited intense photoluminescence (PL) in the NIR region both in the dilute solution (λPL=751 nm, ΦPL=0.25) and in the film (λPL=821 nm, ΦPL=0.038). The BAz monomer showed slight PL in the dilute solution, and aggregation-induced emission (AIE) was detected. We proposed that N=N double bonds should be attractive and functional building blocks for designing π-conjugated materials.
- Gon, Masayuki,Tanaka, Kazuo,Chujo, Yoshiki
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supporting information
p. 6546 - 6551
(2018/04/30)
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- Photocatalytic reduction of nitroarenes to azo compounds over N-doped TiO2: Relationship between catalysts and chemical reactivity
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This work deals with selective reduction of aromatic nitro compounds to corresponding symmetrical substituted azo compounds using nitrogen-doped TiO2 nanoparticles as photocatalyst in the presence of a catalytic amount of formic acid. Various azo compounds containing additional reducible substituents including halogens, and carboxyl and phenol functions have been synthesized in a single step by use of this catalyst. The conversion was reasonably fast, clean, and high yielding at room temperature. A mechanism of formation for the azo compounds is proposed. The behavior of the N/TiO2 catalyst is of particular interest because this is the first time, as far as we know, that formation of azo compounds has been catalyzed by an N-doped TiO2 photocatalyst. Nitrogen-doped TiO2 was prepared by a simple modified sol-gel process with urea as nitrogen source. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy, and transmission electron microscopy. The chemical nature of N was identified by XPS as N-Ti-O in the anatase TiO2 lattice.
- Wang, Huqun,Yang, Xiaofeng,Xiong, Weifeng,Zhang, Zhimin
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p. 3981 - 3997
(2015/06/08)
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- Synthesis of azo compounds by nanosized iron-promoted reductive coupling of aromatic nitro compounds
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Treatment of a variety of aromatic nitro compounds with the active-iron based reducing system composed of FeCl2·4H2O, an excess of lithium powder and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5 mol %) in THF at room temperature, led to the formation of the corresponding symmetrically substituted azo compounds in good yield, resulting from a reductive coupling process. Some other functionalities including carbonyl, halogen, amino and hydroxyl groups, demonstrated to be compatible with the reaction conditions, giving none reduced or coupled by-products. In all cases, the azo compounds formed have not experienced over-reduction to the corresponding hydrazo or amino derivatives even upon prolonged heating or using an excess of the reducing system.
- Moglie, Yanina,Vitale, Cristian,Radivoy, Gabriel
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p. 1828 - 1831
(2008/09/18)
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- Cetyltrimethylammonium dichromate: A mild oxidant for coupling amines and thiols
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A novel lipopathic oxidizing agent, cetyltrimethylammonium dichromate, was used for coupling aromatic amines and thiols to yield the corresponding diazo compounds and disulfides, respectively.
- Patel, Sabita,Mishra
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p. 1371 - 1372
(2007/10/03)
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- Facile synthesis of azo compounds from aromatic nitro compounds using magnesium and triethylammonium formate
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Magnesium/triethylammonium formate is a convenient reagent for the reduction of aromatic nitro compounds to corresponding symmetrically substituted azo compounds. Various azo compounds containing additional reducible substituents, including halogen, nitrile, acid, phenol, ester, and methoxy functions, have been synthesized in a single step by the use of this reagent. The conversion is reasonably fast, clean, high yielding, and occurs at room temperature in methanol.
- Srinivasa,Abiraj,Gowda, D. Channe
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p. 609 - 610
(2007/10/03)
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- Lack of linear free energy relationship: Tungsten(VI) catalyzed perborate oxidation of anilines
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Operation of linear free energy relationships in tungsten(VI) catalyzed perborate oxidation was studied with 29 para-, meta- and ortho-substituted anilines. The activation parameters were calculated from k*( = rate/[substrate]2) at 35, 40, 45, 50 and 55 °C using the Erying relationship by the method of least squares. The oxidation is not isoentropic; in an isoentropic series only enthalpy of activation determines the reactivity and the isokinetic temperature is at infinity. At the isokinetic temperature all the compounds of the reaction series react at equal rate, the variation of substituent at this temperature has no influence on the free energy of activation.
- Karunakaran,Palanisamy
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p. 571 - 575
(2007/10/03)
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- Bis(salicylaldehyde)ethylenedi-iminecobalt(II)-catalysed Oxidation of Aromatic Amins with Oxygen
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N-n-Butylanilines undergo N-dealkylation to give a primary amine and butyrylaldehyde by oxidation with oxygen in the presence of bis(salicylaldehyde)ethylenedi-iminecobalt(II) (CoIIsalen) as a catalyst.High conversions are obtained with high catalyst concentrations and low / ratios (r).Inspection of the effect of catalyst and substrate concentrations on initial reaction rates (Vin) shows poor sensitivity to the electronic effect of the nuclear substituent.Some anilines give azo derivatives at a lower rate in the same conditions.
- Benedini, Francesca,Galliani, Guido,Nali, Micaela,Rindone, Bruno,Tollari, Stefano
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p. 1963 - 1968
(2007/10/02)
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- Oxidations of Aromatic Amines by Superoxide Ion
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Superoxide ion acts as a mild and highly selective oxidizing agent for aromatic amines.Aniline and α-naphthylamine were not oxidized, but β-naphthylamine formed dibenzophenazine, dibenzophenazine and 2,2'-azonaphthalen-1-ol. o- and p-Diamines are oxidized to diaminoazobenzenes but m-diamines are unreactive.Similarly o- and p-aminophenols are oxidized to dihydroxyazobenzenes but m-aminophenols are unaffected, and o-mercaptoaniline forms the disulfide.The oxidations are considered to be free-radical processes, initiated by hydrogen abstraction by superoxide from the substrates.The biological significance of the results is discussed.
- Crank, George,Makin, Mohammad I. H.
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p. 845 - 855
(2007/10/02)
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- Organic chemistry of superoxide. I. Oxidations of aromatic compounds.
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Potassium superoxide is a selective oxidant for aromatic compounds with the order of susceptibility of substituent groups being -SH>-NH2-OH. Only o- and p- disubstituted amines and phenols are oxidized but monosubstituted thiols react.
- Crank,Makin
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p. 2169 - 2170
(2007/10/05)
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