- Hydrogen peroxide based oxidation of hydrazines using HBr catalyst
-
Azo compounds (RN = NR′) are an important class of organic molecules that find wide application in organic synthesis. Herein, we report an efficient, practical and metal-free oxidation of hydrazines (RNH-NHR’) to azo compounds using 5 mol% HBr and hydrogen peroxide as terminal oxidant. This new method has been demonstrated by 40 examples with excellent yields. In addition, we showcased two examples of the one-pot sequential reactions involving our hydrazine oxidation/hydrolysis/Heck reaction or Cu-catalyzed N-arylation with aryl boronic acid. The distinct advantages of this protocol include metal-free catalysis, waste prevention, and easy operation.
- Du, Wanting,Ma, Zichao,Shao, Liming,Wang, Jian
-
-
- Manganese Catalyzed Hydrogenation of Azo (N=N) Bonds to Amines
-
We report the first example of homogeneously catalyzed hydrogenation of the N=N bond of azo compounds using a complex of an earth-abundant-metal. The hydrogenation reaction is catalyzed by a manganese pincer complex, proceeds under mild conditions, and yields amines, which makes this methodology a sustainable alternative route for the conversion of azo compounds. A plausible mechanism involving metal-ligand cooperation and hydrazine intermediacy is proposed based on mechanistic studies. (Figure presented.).
- Ben-David, Yehoshoa,Das, Uttam Kumar,Diskin-Posner, Yael,Kar, Sayan,Milstein, David
-
supporting information
p. 3744 - 3749
(2021/07/09)
-
- Photosensitive and Photoswitchable TRPA1 Agonists Optically Control Pain through Channel Desensitization
-
Transient receptor potential ankyrin 1 (TRPA1) channel, as a nonselective ligand-gated cation channel robustly in dorsal root ganglion sensory neurons, is implicated in sensing noxious stimuli and nociceptive signaling. However, small-molecule tools targeting TRPA1 lack temporal and spatial resolution, limiting their use for validation of TRPA1 as a therapeutic target for pain. In our previous work, we found that 4,4′-(diazene-1,2-diyl)dianiline (AB1) is a photoswitchable TRPA1 agonist, but the poor water solubility and activity hinder its further development. Here, we report a series of specific and potent azobenzene-derived photoswitchable TRPA1 agonists (series 1 and 2) that enable optical control of the TRPA1 channel. Two representative compounds 1g and 2c can alleviate capsaicin-induced pain in the cheek model of mice through channel desensitization but not in TRPA1 knockout mice. Taken together, our findings demonstrate that photoswitchable TRPA1 agonists can be used as pharmacological tools for study of pain signaling.
- Luo, Jiajie,Qi, Hang,Qiao, Zhen,Tang, Xiaowen,Tang, Yi-Quan,Wang, KeWei,Wei, Ningning,Yin, Zhengji,Zhang, Yanru,Zhou, Qiqi,Zhu, Wei
-
supporting information
p. 16282 - 16292
(2021/11/12)
-
- Synthesis of Unsymmetrical Azoxyarenes via Copper-Catalyzed Aerobic Oxidative Dehydrogenative Coupling of Anilines with Nitrosoarenes
-
A copper-catalyzed oxidative dehydrogenative coupling of nitrosobenzenes with anilines for the synthesis of unsymmetrical azoxybenzenes was developed. This approach uses O2 as the oxidant. The reaction products are diverse unsymmetrical azoxybe
- Shi, Chongyang,Xu, Boxia,Fang, Xiaolan,Yu, Xiaochun,Jin, Huile,Wang, Shun
-
supporting information
p. 1963 - 1967
(2021/03/04)
-
- Bifunctional Cs?Au/Co3O4 (Basic and Redox)-Catalyzed Oxidative Synthesis of Aromatic Azo Compounds from Anilines
-
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.
- 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)
-
- TEMPO catalyzed oxidative dehydrogenation of hydrazobenzenes to azobenzenes
-
A metal-free direct oxidative dehydrogenation approach for the synthesis of azobenzenes from hydrazobenzenes has been developed by using TEMPO as an organocatalyst for the first time. The reaction proceeded in open air under mild reaction conditions. A wide range of hydrazobenzenes readily undergo dehydrogenation to give the corresponding azobenzenes in excellent yields.
- Fan, Baomin,Laishram, Ronibala Devi,Li, Jiayan,Luo, Yang,Lv, Haiping,More, Sagar,Su, Zhimin,Xu, Dandan,Yang, Yong,Zhan, Yong
-
supporting information
p. 3471 - 3474
(2020/05/25)
-
- Method for preparing asymmetric azobenzene and azobenzene oxide compounds through photocatalysis
-
The invention relates to a method for preparing asymmetric azobenzene and azobenzene oxide compounds through photocatalysis. Through a photocatalyst, an aromatic nitro compound reacts with an aromaticamino compound under the conditions of illumination and inert gas to obtain an asymmetric azobenzene compound represented by a formula I and an asymmetric azoxybenzene compound represented by a formula II; the method can be used for replacing a conventional mature organic synthesis process, has the advantages of mild conditions, high selectivity and universality, and is suitable for industrial production.
- -
-
Paragraph 0026-0050
(2020/02/27)
-
- Nitrate promoted mild and versatile Pd-catalysed C(sp2)-H oxidation with carboxylic acids
-
A nitrate-promoted Pd-catalysed mild cross-dehydrogenative C(sp2)-H bond oxidation of oximes or azobenzenes with diverse carboxylic acids has been developed. In contrast to the previous catalytic systems, this protocol features mild conditions (close to room temperature for most cases) and a broad substrate scope (up to 64 examples), thus constituting a versatile method to directly prepare diverse O-aryl esters. Moreover, the superiority of the nitrate additive in this mild transformation was further determined by experimental and computational evidence.
- Hao, Hong-Yan,He, Yu-Ting,Lou, Shao-Jie,Luo, Gen,Mao, Yang-Jie,Xiong, Xue,Xu, Dan-Qian,Xu, Zhen-Yuan
-
supporting information
p. 6732 - 6737
(2020/09/21)
-
- Transition Metal-Free Oxidative Coupling of Primary Amines in Polyethylene Glycol at Room Temperature: Synthesis of Imines, Azobenzenes, Benzothiazoles, and Disulfides
-
A transition metal-free protocol has been developed for the oxidative coupling of primary amines to imines and azobenzenes, thiols to disulfides, and 2-aminothiophenols to benzothiazoles, offering excellent yields. The advantageous features of the present environmentally benign methodology include the usage of biocompatible and green reaction conditions such as, solvent, room temperature reactions and transition metal-free approach. Moreover, it offers a broader substrate scope.
- Hudwekar, Abhinandan D.,Verma, Praveen K.,Kour, Jaspreet,Balgotra, Shilpi,Sawant, Sanghapal D.
-
p. 1242 - 1250
(2019/01/09)
-
- Photocatalyzed oxidative dehydrogenation of hydrazobenzenes to azobenzenes
-
Visible light mediated oxidative dehydrogenation of hydrazobenzenes under an ambient atmosphere using an organic dye as a photocatalyst was reported for the first time. The reaction provides an environmentally benign method for the preparation of azobenzenes in excellent yields with good functional group tolerance.
- Lv, Haiping,Laishram, Ronibala Devi,Li, Jiayan,Zhou, Yongyun,Xu, Dandan,More, Sagar,Dai, Yuze,Fan, Baomin
-
supporting information
p. 4055 - 4061
(2019/08/07)
-
- T BuOK-triggered bond formation reactions
-
Recently, inexpensive and readily available tBuOK has seen widespread use in transition-metal-free reactions. Herein, we report the use of tBuOK for S-S, S-Se, NN and CN bond formations, which significantly extends the scope of tBuOK in chemical synthesis. Compared with traditional methods, we have realized mild and general methods for disulfide, azobenzenes imine etc. synthesis.
- Xu, Yulong,Shi, Xiaonan,Wu, Lipeng
-
p. 24025 - 24029
(2019/08/13)
-
- Visible-light-promoted oxidative dehydrogenation of hydrazobenzenes and transfer hydrogenation of azobenzenes
-
Azo compounds are widely used in the pharmaceutical and chemical industries. Here, we report the use of a non-metal photo-redox catalyst, Eosin Y, to synthesize azo compounds from hydrazine derivatives. The use of visible-light with air as the oxidant makes this process sustainable and practical. Moreover, the visible-light-driven, photo-redox-catalyzed transfer hydrogenation of azobenzenes is compatible with a series of hydrogen donors such as phenyl hydrazine and cyclic amines. Compared with traditional (thermal/transition-metal) methods, our process avoids the issue of over-reduction to aniline, which extends the applicability of photo-redox catalysis and confirms it as a useful tool for synthetic organic chemistry.
- Wang, Xianya,Wang, Xianjin,Xia, Chungu,Wu, Lipeng
-
supporting information
p. 4189 - 4193
(2019/08/07)
-
- Synthesis of Unsymmetrical Aromatic Azoxy Compounds by Silver-Mediated Oxidative Coupling of Aromatic Amines with Nitrosoarenes
-
A silver(I) oxide-mediated synthesis of unsymmetrical aromatic azoxy compounds has been successfully achieved, wherein oxidative coupling reactions between aromatic amines and nitrosoarenes take place in ethanol under air. This reaction has very high economic value because silver(I) oxide is the only oxidant required and no other additive is needed. The resulted silver particles can be easily recovered, while the only other byproduct is water. This new procedure is compatible with various functional groups and proceeds under mild reaction conditions.
- Ding, Weijie,Xu, Shengshi,Yu, Xiaochun,Wang, Shun
-
supporting information
(2019/02/07)
-
- Synthetic method for aromatic azo compound based on cyclohexanone aromatization
-
The invention provides a synthetic method for an aromatic azo compound based on cyclohexanone aromatization, and belongs to the technical field of organic chemistry. The method provided by the invention comprises the step of using iodine and DMSO to promote a cyclohexanone compound and arylhydrazine to condensation and dehydrogenation aromatization, and generating the aromatic azo compound. The synthetic method provided by the invention is capable of conveniently synthesizing the asymmetrical aromatic azo compound, and moderate in condition, wide in substrate applicability, simple and convenient in operation, lower in cost, high in product purity, convenient for separation and purification, and is suitable for large-scale preparation without using acid and transition metal.
- -
-
Paragraph 0063-0067
(2019/03/28)
-
- Photocatalysis Enabling Acceptorless Dehydrogenation of Diaryl Hydrazines at Room Temperature
-
Aromatic azo compounds are privileged structural motifs, and they exhibit a myriad of pharmaceutical as well as industrial applications. Here, we report a catalytic acceptorless dehydrogenation of diarylhydrazine derivatives to access a wide variety of aryl-azo compounds with the removal of molecular hydrogen as the sole byproduct. This distinctive reactivity has been achieved under dual catalytic conditions by merging the visible-light active [Ru(bpy)3]2+ as the photoredox catalyst and Co(dmgH)2(py)Cl as the proton-reduction catalyst. The reaction proceeds smoothly under very mild and benign conditions and operates at ambient temperature. This dual catalytic approach is highly compatible with many different functional groups and has a broad substrate scope. We have also demonstrated the reversible hydrogen storage and release phenomenon on hydrazobenzene/azobenzene couple to show the utility of these compounds as hydrogen storage materials. Further diversification of azobenzene was shown by a transition-metal-catalyzed azo-group-directed ortho-C-H bond functionalization.
- Sahoo, Manoj K.,Saravanakumar, Krishnasamy,Jaiswal, Garima,Balaraman, Ekambaram
-
p. 7727 - 7733
(2018/07/25)
-
- Oxidative Coupling of Aromatic Amines and Nitrosoarenes: Iodine-Mediated Formation of Unsymmetrical Aromatic Azoxy Compounds
-
I2/DABCO (iodine/1,4-diazabicyclo[2.2.2]octane)-mediated oxidative coupling of nitrosobenzenes with aromatic amines was revealed to lead to the production of unsymmetrical aromatic azoxy compounds, instead of azo compounds reported previously in Mills reaction. Our study illustrates that various aromatic amines can be efficiently coupled with nitrosobenzenes to produce unsymmetrical azoxy product, in which more than thirty unsymmetrical azoxybenzenes have been successfully prepared. The applicability to a broad range of substrates, scalability to large scales and mild reaction conditions make this new synthetic protocol very practical, providing a convenient and direct access to unsymmetrical azoxybenzenes. (Figure presented.).
- Yu, Xiaochun,Ding, Weijie,Ge, Panyu,Wang, Shun,Wang, Jichang
-
supporting information
p. 3150 - 3156
(2018/08/24)
-
- A metal-catalyst-free oxidative coupling of anilines to aromatic azo compounds in water using bleach
-
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.
- de Souza, Gabriela F.P.,von Zuben, Theodora W.,Salles, Airton G.
-
supporting information
p. 3753 - 3755
(2018/09/21)
-
- Convenient Electrocatalytic Synthesis of Azobenzenes from Nitroaromatic Derivatives Using SmI2
-
The synthesis of azobenzenes has been a long-standing challenge. Their current preparation at a preparative or industrial scale requires stoichiometric amounts of environmentally unfriendly reactants. Herein, we demonstrate that the catalytic use of electrogenerated samarium diiodide (SmI2) could promote, in one-step synthesis, the reduction of nitrobenzenes into azobenzenes in high yields under mild reaction conditions. This catalytic procedure contains many elements satisfying a sustainable chemical process for the preparation of one of the most widely wanted family of chemical compounds. The easy synthetic procedure, and the absence of precious metals, bases, and nonhazardous substances, already makes our catalytic procedure a serious alternative to currently available methods. This is a promising method for the efficient synthesis of both symmetrical and asymmetrical azo compounds with a high functional group tolerance.
- Zhang, Yu-Feng,Mellah, Mohamed
-
p. 8480 - 8486
(2017/12/08)
-
- Aromatic amine oxidation process for preparing aromatic azobenzene method
-
The invention relates to a method for preparing an aromatic azo compound by utilizing aromatic amine oxidation. In the method, air or oxygen serves as an oxygen source, and under the effect of a catalyst, aromatic amine is oxidized into the aromatic azo compound. The method is high in oxidization efficiency and product yield; the air or the oxygen serves as the oxygen source, and the method is economical and environmentally friendly. The product and the catalyst can be separated easily, and the aftertreatment is simple. The catalyst is easy to reuse, and the method has very good application prospect.
- -
-
Paragraph 0024; 0026-0027
(2017/10/11)
-
- Dehydrogenation of the NH?NH Bond Triggered by Potassium tert-Butoxide in Liquid Ammonia
-
A novel strategy for the dehydrogenation of the NH?NH bond is disclosed using potassium tert-butoxide (tBuOK) in liquid ammonia (NH3) under air at room temperature. Its synthetic value is well demonstrated by the highly efficient synthesis of aromatic azo compounds (up to 100 % yield, 3 min), heterocyclic azo compounds, and dehydrazination of phenylhydrazine. The broad application of this strategy and its benefit to chemical biology is proved by a novel, convenient, one-pot synthesis of aliphatic diazirines, which are important photoreactive agents for photoaffinity labeling.
- Wang, Lei,Ishida, Akiko,Hashidoko, Yasuyuki,Hashimoto, Makoto
-
supporting information
p. 870 - 873
(2017/01/14)
-
- Oxidative coupling of anilines to azobenzenes using heterogeneous manganese oxide catalysts
-
We herein report the transition metal oxide-catalyzed synthesis of azobenzenes through the oxidative coupling of anilines. An octahedral molecular sieve of manganese oxide, OMS-2, exhibited the best activity and selectivity. Nine examples of symmetric azobenzenes and twenty unsymmetric ones were synthesized with 62-99% conversion and 64-99% selectivity. In the aniline cross-coupling reactions, the difference of the Hammett constants of two substituted groups (Δσ) determines the selectivity to unsymmetric azobenzenes, which are the major products at Δσ 0.32. In-depth studies reveal that the surface defect sites of the mixed-valence manganese oxide play a key role in facilitating electron transfer and activating molecular oxygen. The single-electron transfer (SET) reaction mechanism is proposed based on electron paramagnetic resonance and X-ray powder diffraction characterization.
- Wang, Min,Ma, Jiping,Yu, Miao,Zhang, Zhe,Wang, Feng
-
p. 1940 - 1945
(2016/04/05)
-
- Formal [4+2] cycloaddition of 3-ethoxycyclobutanones with azo compounds
-
Azobenzenes reacted with 3-ethoxycyclobutanoes to give 2,3-dihydro-pyridazin-4(1H)-ones by using EtAlCl2as a Lewis acid. Thus, ring cleavage of 3-ethoxycyclobutanones took place to form a zwitterionic intermediate by activation with EtAlCl2, and intermolecular formal [4+2] cycloaddition of the zwitterionic intermediate proceeded with azobenzenes to give 2,3-dihydro-pyridazin-4(1H)-ones after elimination of ethanol. Regioselectivity for cycloaddition of unsymmetrical azobenzenes, ring contraction and chemoselective reduction of 2,3-dihydro-pyridazin-4(1H)-ones, and [4+2] cycloaddition to 4-phenyl-1,2,4-triazolin-3,5-dione are also described.
- Shima, Yusuke,Matsuo, Jun-ichi
-
supporting information
p. 4066 - 4069
(2016/08/18)
-
- Mesoporous manganese oxide catalyzed aerobic oxidative coupling of anilines to aromatic azo compounds
-
Herein we introduce an environmentally friendly approach to the synthesis of symmetrical and asymmetrical aromatic azo compounds by using air as the sole oxidant under mild reaction conditions in the presence of cost-effective and reusable mesoporous manganese oxide materials.
- Dutta, Biswanath,Biswas, Sourav,Sharma, Vinit,Savage, Nancy Ortins,Alpay, S. Pamir,Suib, Steven L.
-
supporting information
p. 2171 - 2175
(2016/02/18)
-
- Metal-free aerobic oxidative coupling of amines in dimethyl sulfoxide via a radical pathway
-
Metal-free oxidative coupling of amines is achieved simply by heating their dimethyl sulfoxide (DMSO) solution under oxygen as oxidant without any other catalysts or additives, accompanied by the formation of an equimolar amount of dimethyl sulfone (DMSO2). EPR experiments indicate that the reaction proceeds via a radical pathway. DMSO may play a triple role as solvent, radical initiator and co-reductant.
- Lin, Mu,Wang, Zikuan,Fang, Huayi,Liu, Lianghui,Yin, Haolin,Yan, Chun-Hua,Fu, Xuefeng
-
p. 10861 - 10864
(2016/02/05)
-
- A mild CuBr-NMO oxidative system for the coupling of anilines leading to aromatic azo compounds
-
An efficient, mild and cost-effective method has been developed utilizing CuBr with N-methylmorpholine N-oxide (NMO/NMMO) for the oxidative coupling of anilines to access symmetrical and unsymmetrical azo compounds in high yield. The reactivity was found to be governed by electronic and steric factors of anilines.
- Singh, Shikha,Chauhan, Parul,Ravi, Makthala,Taneja, Isha,Wahajuddin,Yadav, Prem. P.
-
p. 61876 - 61880
(2015/08/03)
-
- Deoxygenative coupling of nitroarenes for the synthesis of aromatic azo compounds with CO using supported gold catalysts
-
A facile and efficient catalytic system based on a mesostructured ceria-supported gold (Au/meso-CeO2) catalyst was developed for the synthesis of various aromatic azo compounds by the reductive coupling of the corresponding nitroaromatics, using CO as the sole deoxygenative reagent, under additive-free and mild reaction conditions.
- Li, Hai-Qian,Liu, Xiang,Zhang, Qi,Li, Shu-Shuang,Liu, Yong-Mei,He, He-Yong,Cao, Yong
-
supporting information
p. 11217 - 11220
(2015/07/07)
-
- Gold-catalyzed direct hydrogenative coupling of nitroarenes to synthesize aromatic azo compounds
-
The azo linkage is a prominent chemical motif which has found numerous applications in materials science, pharmaceuticals, and agrochemicals. Described herein is a sustainable heterogeneous-gold-catalyzed synthesis of azo arenes. Available nitroarenes are deoxygenated and linked selectively by the formation of N-N bonds using molecular H2 without any external additives. As a result of a unique and remarkable synergy between the metal and support, a facile surface-mediated condensation of nitroso and hydroxylamine intermediates is enabled, and the desired transformation proceeds in a highly selective manner under mild reaction conditions. The protocol tolerates a large variety of functional groups and offers a general and versatile method for the environmentally friendly synthesis of symmetric or asymmetric aromatic azo compounds.
- Liu, Xiang,Li, Hai-Qian,Ye, Sen,Liu, Yong-Mei,He, He-Yong,Cao, Yong
-
supporting information
p. 7624 - 7628
(2014/08/05)
-
- One-pot preparation of azobenzenes from nitrobenzenes by the combination of an indium-catalyzed reductive coupling and a subsequent oxidation
-
We demonstrated how a reduction step with a reducing system comprised of In(OTf)3 and Et3SiH and a subsequent oxidation that occurred under an ambient (oxygen) atmosphere allowed the highly selective and catalytic conversion of aromatic nitro compounds into symmetrical or unsymmetrical azobenzene derivatives. This catalytic system displayed a tolerance for the functional groups on a benzene ring: an alkyl group, a halogen, an acetyl group, an ester, a nitrile group, an acetyl group, an ester moiety, and a sulfonamide group.
- Sakai, Norio,Asama, Shun,Anai, Satsuki,Konakahara, Takeo
-
p. 2027 - 2033
(2014/03/21)
-
- Highly efficient synthesis of azos catalyzed by the common metal copper (0) through oxidative coupling reactions
-
A facile and efficient approach to synthesize symmetric, asymmetric and bridged aromatic azo compounds (AAzos) from aromatic amines was developed by using red copper as catalyst. Despite numerous efforts towards the catalytic synthesis of symmetric and asymmetric AAzos derivatives, most reactions present certain drawbacks inhibiting their industrial applications, such as laborious multi-step processes, harsh reaction conditions and expensive reagents. And the synthesis of bridged azos had low yields before. With the presence of ammonium bromide as co-catalyst, pyridine as a ligand and molecular dioxygen as a sole oxidative reagent, red copper, a common and abundant metal in nature, exhibited unexpected catalytic activity towards the preparation of AAzos in high yields via one-step reaction, making this catalyst an attractive candidate for industrial and synthetic applications.
- Wang, Jiaqing,He, Jing,Zhi, Cong,Luo, Bin,Li, Xinming,Pan, Yue,Cao, Xueqin,Gu, Hongwei
-
p. 16607 - 16611
(2014/05/06)
-
- Mild, selective and switchable transfer reduction of nitroarenes catalyzed by supported gold nanoparticles
-
A highly versatile and flexible gold-based catalytic system has been developed for the controlled and selective transfer reduction of nitroarene using 2-propanol as a convenient hydrogen source under mild conditions. Depending on the specific reaction conditions, multiple products including azoxyarenes, symmetric or asymmetric azoarenes and anilines can be obtained respectively via a controlled reduction of the nitro aromatics with good to excellent yields in the presence of a reusable mesostructured ceria-supported gold (Au/meso-CeO2) catalyst. The overall operational simplicity, high chemoselectivity, functional-group tolerance and reusability of the catalyst make this approach an attractive and reliable tool for organic and process chemists. The Royal Society of Chemistry.
- Liu, Xiang,Ye, Sen,Li, Hai-Qian,Liu, Yong-Mei,Cao, Yong,Fan, Kang-Nian
-
p. 3200 - 3206
(2013/12/04)
-
- Room temperature activation of oxygen by monodispersed metal nanoparticles: Oxidative dehydrogenative coupling of anilines for azobenzene syntheses
-
It is highly challenging but desirable to develop efficient catalysts for the activation of oxygen under mild conditions. Here, we report that various monodispersed metal nanoparticles (Ag, Pt, Co, Cu, Ni, Pd, and Au) efficiently activated molecular oxygen under mild conditions, illustrated by the aerobic oxidation of anilines to form either symmetric or asymmetric aromatic azo compounds. This discovery indicates that exploiting the catalytic power of nanoparticles could enable sustainable chemistry suitable for important oxidation reactions.
- Cai, Shuangfei,Rong, Hongpan,Yu, Xiaofei,Liu, Xiangwen,Wang, Dingsheng,He, Wei,Li, Yadong
-
p. 478 - 486
(2013/05/22)
-
- Highly selective conversion of nitrobenzenes using a simple reducing system combined with a trivalent indium salt and a hydrosilane
-
Controlling the type of indium salt and hydrosilane enables a highly selective reduction of aromatic nitro compounds into three coupling compounds, azoxybenzenes, azobenzenes and diphenylhydrazines, and one reductive compound, anilines. The Royal Society of Chemistry 2010.
- Sakai, Norio,Fujii, Kohji,Nabeshima, Shinya,Ikeda, Reiko,Konakahara, Takeo
-
scheme or table
p. 3173 - 3175
(2010/08/19)
-
- Reaction of dimethyldioxirane with aniline hydrohalides
-
Oxidation of aromatic amine hydrohalides (aniline hydrochloride, hydrobromide, and hydrofluoride; 4-methylaniline hydrochloride and hydrobromide; 3-methylaniline and N,N-diethylaniline hydrochlorides) with dimethyldioxirane was studied. The product composition was analyzed in relation to the reactant ratio.
- Ivanova,Grabovskii,Kabal'nova,Shereshovets
-
p. 2101 - 2105
(2007/10/03)
-
- A novel synthesis of unsymmetrical azo aromatics inaccessible by diazo-coupling reaction
-
A novel synthesis of unsymmetrical azo aromatics inaccessible by diazo-coupling reaction is reported. The synthesis involved the reaction of acetanilides with nitroarenes under moderate reaction conditions. A reaction pathway via a nitrosoarene intermediate involving elimination of the elements of the acetate anion, is proposed.
- Ayyangar,Naik,Srinivasan
-
p. 7253 - 7256
(2007/10/02)
-
- A Simple Route for the Synthesis of Chlorosubstituted Arylazobenzenes, Arylazonaphtalenes, and Arylazopyrazoles
-
The reaction of arylazophenoles and arylazohydroxypyrazoles (or their tautomer hydrazones) 10, 11, and 15 with POCl3 in dimethylformamide yields chlorosubstituted arylazobenzenes or arylazopyrazoles 12, 13 and 16, resp., in moderate to high yields.The substitution of the OH-group by the Cl-moiety is favoured by acceptor substituents in the aryl fragments ortho- and/or para-linked to the azo group.In case that arylazocompounds derived from resorcinol are used the substitution reaction runs in a stepwise manner giving raise to the formation of o-hydroxy-p-chlorosubstit uted azo compounds 18 primarily and then of dichlorosubstituted azo compounds 19.
- Guenther, R.,Jaehne, E.,Hartmann, H.,Schulze, M.
-
p. 945 - 954
(2007/10/02)
-
- Lead Tetra-acetate Oxidation of Tris(arylhydrazones) of Cyclohexane-1,2,3-triones
-
Oxidation of the title compounds with lead tetra-acetate gives 2-aryl-4-arylhydrazono-4,5,6,7-tetrahydro-2H-benzo-1,2,3-triazoles, the corresponding 4-oxo-derivatives, and as minor products 2-aryl-4-acetoxy-4-arylazo-4,5,6,7-tetrahydro-2H-benzo-1,2,3-triazoles, and substituted azobenzenes.The oxidation mechanism is discussed.
- Lefkopoulou, S.,Stephanidou-Stephanatou, J.,Alexandrou, N. E.
-
p. 1076 - 1100
(2007/10/02)
-
- Kinetics of the Chlorination of Azobenzene and Comparison with Azoxybenzene
-
The activating effect of the phenylazo substituent in electrophilic substitution has been examined.The rates and partial rate factors for chlorination of azobenzene with molecular chlorine and protonated chlorine acetate have been determined relative to benzene.Whereas the chlorine acetate reaction proceeds readily (relative rate 4900) there is virtually no activation to chlorination by molecular chlorine.Complexes between azobenzene and bromine were, however, isolated and characterized.Their formation implies that during molecular halogenation reactions the electrop hile is essentially unavailable.The relative chlorination rates for azobenzene and azoxybenzene have also been established: the phenylazo group is more activating towards protonated chlorine acetate whereas azoxybenzene (which does not complex with halogens) is the more reactive with molecular chlorine.The chlorination results confirm the versatility of the phenylazo group which is the first substituent for which kinetic data have been obtained quantifying activation of aromatic electrophilic, radical and nucleophilic substitution.
- Ahmed, Karamalla A.,Hanhela, Peter J.,Hassan, Mustapha,Miller, Joseph,Paul, D. Brenton
-
p. 2249 - 2259
(2007/10/02)
-
- SYNTHESIS OF AZOXYBENZENE-SbCl5 COMPLEXES AND THEIR SELECTIVE ORTHO-WALLACH REARRANGEMENT
-
When an equimolar solution of various azoxybenzenes and SbCl5 in carbon tetrachloride were mixed, a 1:1 complex immediately deposited as orange crystals in high yield.The thermal reaction of these complexes in inert solvents gives o-hydroxy-azobenzene selectively.On the contrary, other Lewis acids, such as TiCl4, AlCl3, FeCl3 and ZnBr2 failed to give an isolatable complex with azoxybenzene, and their direct thermal reaction with azoxybenzene resulted in deoxygenation to yield azobenzene as a main product.
- Yamamoto, Jiro,Nishigaki, Yukihiro,Umezu, Masahiro,Matsuura, Teruo
-
p. 3177 - 3180
(2007/10/02)
-