- Convenient semihydrogenation of azoarenes to hydrazoarenes using H2
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The high atom-economical and eco-benign nature of hydrogenation reactions make them much more superior to conventional reduction and transfer hydrogenation. Herein, a convenient and highly selective hydrogenation reaction of azoarenes using molecular hydrogen to access diverse hydrazoarenes is reported. The present catalytic method is general and operationally simple, and it operates under exceedingly mild conditions (room temperature and 1 atm of hydrogen pressure). The reusability of catalysts used in this method is also successfully demonstrated.
- Sahoo, Manoj K.,Sivakumar, Ganesan,Jadhav, Sanjay,Shaikh, Samrin,Balaraman, Ekambaram
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supporting information
p. 5289 - 5293
(2021/06/30)
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- Hydrogen peroxide based oxidation of hydrazines using HBr catalyst
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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
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- Visible-Light-Promoted Diboron-Mediated Transfer Hydrogenation of Azobenzenes to Hydrazobenzenes
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A visible-light-promoted transfer hydrogenation of azobenzenes has been developed. In the presence of B2pin2 and upon visible-light irradiation, the reactions proceeded smoothly in methanol at ambient temperature. The azobenzenes with diverse functional groups have been reduced to the corresponding hydrazobenzenes with a yield of up to 96%. Preliminary mechanistic studies indicated that the hydrogen atom comes from the solvent and the transformation is achieved through a radical pathway.
- Song, Menghui,Zhou, Hongyan,Wang, Ganggang,Ma, Ben,Jiang, Yajing,Yang, Jingya,Huo, Congde,Wang, Xi-Cun
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p. 4804 - 4811
(2021/04/06)
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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
-
supporting information
p. 2468 - 2472
(2021/04/02)
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- Tandem selective reduction of nitroarenes catalyzed by palladium nanoclusters
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We report a catalytic tandem reduction of nitroarenes by sodium borohydride (NaBH4) in aqueous solution under ambient conditions, which can selectively produce five categories of nitrogen-containing compounds: anilines, N-aryl hydroxylamines, azoxy-, azo- and hydrazo-compounds. The catalyst is in situ-generated ultrasmall palladium nanoclusters (Pd NCs, diameter of 1.3 ± 0.3 nm) from the reduction of Pd(OAc)2 by NaBH4. These highly active Pd NCs are stabilized by surface-coordinated nitroarenes, which inhibit the further growth and aggregation of Pd NCs. By controlling the concentration of Pd(OAc)2 (0.1-0.5 mol% of nitroarene) and NaBH4, the water/ethanol solvent ratio and the tandem reaction sequence, each of the five categories of N-containing compounds can be obtained with excellent yields (up to 98%) in less than 30 min at room temperature. This tunable catalytic tandem reaction works efficiently with a broad range of nitroarene substrates and offers a green and sustainable method for the rapid and large-scale production of valuable N-containing chemicals.
- Yan, Ziqiang,Xie, Xiaoyu,Song, Qun,Ma, Fulei,Sui, Xinyu,Huo, Ziyu,Ma, Mingming
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supporting information
p. 1301 - 1307
(2020/03/11)
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- Visible-light-promoted oxidative dehydrogenation of hydrazobenzenes and transfer hydrogenation of azobenzenes
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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)
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- Electrochemical dehydrogenation of hydrazines to azo compounds
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A strategy for the electrochemical dehydrogenation of hydrazine compounds is disclosed under ambient conditions. This protocol proceeded smoothly in ethanol by employing electrons as clean oxidants. Its synthetic value is well demonstrated by the highly efficient synthesis of symmetric and unsymmetric azo compounds. It is an environmentally friendly transformation and the present protocol was effective on a large scale.
- Du, Ke-Si,Huang, Jing-Mei
-
supporting information
p. 1680 - 1685
(2019/04/08)
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- Transfer Hydrogenation of Azo Compounds with Ammonia Borane Using a Simple Acyclic Phosphite Precatalyst
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Tris(quinolin-8-yl)phosphite, P(Oquin)3, promotes the dehydrogenation of H3N·BH3 (AB) and the transfer hydrogenation of azoarenes using ammonia borane (AB) as H2 source. The metal-free reduction of azoarenes proceeds under mild reaction conditions upon which several diphenylhydrazine derivatives are obtained in high yields. The reactivity of P(Oquin)3 toward AB was evaluated through NMR in situ tests. The rate of the reaction, activation parameters, deuterium kinetic isotope effect (DKIE) and linear-free energy relationship were investigated. Such mechanistic and kinetic studies suggest that P(Oquin)3 is a precatalyst and that AB is likely involved in more than one stage of the reaction pathway. Furthermore, the kinetic data indicate that the reaction proceeds through an ordered transition state, possibly associative.
- Chacón-Terán, Miguel A.,Rodríguez-Lugo, Rafael E.,Wolf, Robert,Landaeta, Vanessa R.
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supporting information
p. 4336 - 4344
(2019/08/20)
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- Chemoselective hydrogenation of nitrobenzenes activated with tuned Au/h-BN
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The azo- and hydrazo compounds are of great importance in pharmaceuticals, agrochemicals, and chemistry. The controlled reduction of nitroarenes to their coupled products such as aromatic azo and hydrazo compounds has been an interesting area of research synthetically and mechanistically. Herein, we report that the chemoselective catalytic hydrogenation of nitrobenzenes to hydrazobenzenes via azobenzenes can be achieved over gold nanoparticles supported by hexagonal boron nitride nanoplates. It is found that the catalytic process can be successfully conducted not only in N2 but also in air with isopropanol alcohol/KOH. Complete conversion of nitrobenzenes and high selectivity of azobenzenes and hydrazobenzenes have been achieved in one pot under N2 or air atmosphere. Furthermore, as usual unstable intermediates in the reduction process of nitrobenzenes, azobenzenes and hydrazobenzenes can be alternatively harvested as the main product by controlling reaction time or atmosphere. This work shows promise for direct and chemoselective synthesis of azo- and hydrazo compounds under mild conditions in a controllable manner.
- Liu, Qiuwen,Xu, Yan,Qiu, Xiaoqing,Huang, Caijin,Liu, Min
-
-
- A switchable-selectivity multiple-interface Ni-WC hybrid catalyst for efficient nitroarene reduction
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Selective reduction of nitroarenes is extremely valuable in industrial chemical production. The main reduced products are usually aniline derivatives obtained using single-component noble- or transition-metal catalysts; however, other important products such as hydrazobenzene derivatives always involve in harsh conditions and multiple reaction steps. Here, we realize an unexpected switchable reduction of nitroarenes into aniline or hydrazobenzene derivatives with high yield and selectivity just by controlling the molar ratio of nitroarenes to N2H4·H2O with a nickel–tungsten carbide composite nanocatalyst loaded on carbon (Ni-WC/C). A series of control experiments and density functional theory (DFT) calculations indicate that the multiple interfaces between Ni and WC can induce a synergistic effect, significantly modulating the electronic structure of the Ni-WC/C catalyst, and endowing the catalyst with switchable selectivity and high activity for the reduction of nitroarenes by hydrogenation. This synergistic multi-interfacial catalyst may offer a new way to design and explore highly efficient and selective catalysts for the controllable reduction of nitroarenes and similar hydrogenation reactions.
- Ma, Yuanyuan,Lang, Zhongling,Du, Jing,Yan,Wang, Yonghui,Tan, Huaqiao,Khan, Shifa Ullah,Liu, Yang,Kang, Zhenhui,Li, Yangguang
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p. 174 - 182
(2019/08/06)
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- Photocatalysis Enabling Acceptorless Dehydrogenation of Diaryl Hydrazines at Room Temperature
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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
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p. 7727 - 7733
(2018/07/25)
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- Atomic Layer Deposition of Iron Sulfide and Its Application as a Catalyst in the Hydrogenation of Azobenzenes
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The atomic layer deposition (ALD) of iron sulfide (FeSx) is reported for the first time. The deposition process employs bis(N,N′-di-tert-butylacetamidinato)iron(II) and H2S as the reactants and produces fairly pure, smooth, and well-crystallized FeSx thin films following an ideal self-limiting ALD growth behavior. The FeSx films can be uniformly and conformally deposited into deep narrow trenches with aspect ratios as high as 10:1, which highlights the broad applicability of this ALD process for engineering the surface of complex 3D nanostructures in general. Highly uniform nanoscale FeSx coatings on porous γ-Al2O3 powder were also prepared. This compound shows excellent catalytic activity and selectivity in the hydrogenation of azo compounds under mild reaction conditions, demonstrating the promise of ALD FeSx as a catalyst for organic reactions.
- Shao, Youdong,Guo, Zheng,Li, Hao,Su, Yantao,Wang, Xinwei
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supporting information
p. 3226 - 3231
(2017/03/17)
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- Dehydrogenation of the NH?NH Bond Triggered by Potassium tert-Butoxide in Liquid Ammonia
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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
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supporting information
p. 870 - 873
(2017/01/14)
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- Homolytic Cleavage of a B-B Bond by the Cooperative Catalysis of Two Lewis Bases: Computational Design and Experimental Verification
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Density functional theory (DFT) investigations revealed that 4-cyanopyridine was capable of homolytically cleaving the B-B σ bond of diborane via the cooperative coordination to the two boron atoms of the diborane to generate pyridine boryl radicals. Our experimental verification provides supportive evidence for this new B-B activation mode. With this novel activation strategy, we have experimentally realized the catalytic reduction of azo-compounds to hydrazine derivatives, deoxygenation of sulfoxides to sulfides, and reduction of quinones with B2(pin)2 at mild conditions. Breaking good: The diborane B-B bond can be homolytically cleaved via the cooperative catalysis of two 4-cyanopyridine molecules. Using this combination of a diborane (B2(pin)2) and 4-cyanopyridine also allows the catalytic reduction of the N=N double bond of azo-compounds to hydrazine derivatives, deoxygenation of sulfoxides to sulfides, and reduction of quinones under mild conditions.
- Wang, Guoqiang,Zhang, Honglin,Zhao, Jiyang,Li, Wei,Cao, Jia,Zhu, Chengjian,Li, Shuhua
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p. 5985 - 5989
(2016/05/19)
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- Activation method of bis(pinacolato)diborane and application thereof
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The invention discloses an activation method of bis(pinacolato)diborane. R substituted pyridine induces the homolysis of bis(pinacolato)diborane to obtain boron free radicals, and the process is shown by a formula I, wherein R refers to independent cyano and nitro. The invention also provides an application of the activation method of bis(pinacolato)diborane. Specifically, the activation method is applied to the synthesis of hydro-azobenzene derivatives.
- -
-
Paragraph 0050; 0051; 0052
(2016/10/31)
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- Titania-Supported Gold Nanoparticles Catalyze the Selective Oxidation of Amines into Nitroso Compounds in the Presence of Hydrogen Peroxide
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In this article, the catalytic activity of titania-supported gold nanoparticles (Au/TiO2) was studied for the selective oxidation of amines into nitroso compounds using hydrogen peroxide (H2O2). Gold nanoparticles deposited on Degussa P25 polymorphs of titania (TiO2) have been found to promote the selective formation of a variety of nitroso arenes in high yields and selectivities, even in a large-scale synthesis. In contrast, alkyl amines are oxidized to the corresponding oximes under the examined conditions. Kinetic studies indicated that aryl amines substituted with electron-donating groups are oxidized faster than the corresponding amines bearing an electron-withdrawing functionality. A Hammett-type kinetic analysis of a range of para-X-substituted aryl amines implicates an electron transfer (ET) mechanism (ρ=-1.15) for oxidation reactions with concomitant formation of the corresponding N-aryl hydroxylamine as possible intermediate. We also show that the oxidation protocol of aryl amines in the presence of 1,3-cyclohexadiene leads in excellent yields to the corresponding hetero Diels-Alder adducts between the diene and the in situ formed nitrosoarenes.
- Fountoulaki, Stella,Gkizis, Petros L.,Symeonidis, Theodoros S.,Kaminioti, Eleni,Karina, Athanasia,Tamiolakis, Ioannis,Armatas, Gerasimos S.,Lykakis, Ioannis N.
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supporting information
p. 1500 - 1508
(2016/05/19)
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- Synthesis, in vitro and in vivo anticancer activities of novel 4-substituted 1,2-bis(4-chlorophenyl)-pyrazolidine-3,5-dione derivatives
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To develop potent and selective anticancer agents, a series of novel 4-substituted 1,2-bis(4-chlorophenyl)-pyrazolidine-3,5-dione derivatives were designed and synthesized. All the compounds were evaluated for their antiproliferative activities against a panel of four human cancer cell lines. Among them, compound 4u is the most potent, exhibiting IC50 values ranging from 5.1 to 10.1 μM. Flow cytometry and western blot analyses revealed that treatment of MGC-803 cells with compound 4u induces early cellular apoptosis via activation of caspases-9/3. Furthermore, compound 4u effectively reduced the tumor growth exhibited by human gastric cancer cells in vivo without obvious adverse side effects. Our findings indicate that compound 4u may serve as a lead compound to target solid tumors.
- Zhang, Xu-Yao,Gu, Yi-Fei,Chen, Ting,Yang, Dong-Xiao,Wang, Xi-Xin,Jiang, Bai-Ling,Shao, Kun-Peng,Zhao, Wen,Wang, Cong,Wang, Jun-Wei,Zhang, Qiu-Rong,Liu, Hong-Min
-
supporting information
p. 1781 - 1786
(2015/10/20)
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- Hydrogenation of nitroarenes with palladium nanoparticles stabilized by alkyne derivatives in homogeneous phase
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Palladium nanoparticles stabilized by alkyne derivatives catalyzed the hydrogenation of nitroarenes to the aryl amines in homogeneous phase. The reaction of nitrobenzene proceeded smoothly with a substrate-to-palladium molar ratio (S/Pd) of 51,000 under 8 atm of H2. The reaction under 1 atm of H2 with an S/Pd of 1030 was completed in 4 h. A series of substituted nitroarenes, including 4-acetyl- and 4-formylnitrobenzenes, were converted to the aryl amines with high chemoselectivity.
- Arai, Noriyoshi,Onodera, Nozomi,Dekita, Atsushi,Hori, Junichi,Ohkuma, Takeshi
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supporting information
p. 3913 - 3915
(2015/06/08)
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- Mechanistic studies of the reduction of nitroarenes by NaBH4 or hydrosilanes catalyzed by supported gold nanoparticles
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Herein, we show that mesoporous titania-supported gold nanoparticle assemblies (Au/MTA) catalyze the activation of NaBH4 and 1,1,3,3-tetramethyl disiloxane (TMDS) compounds, which act as transfer hydrogenation agents for the reduction of nitroarenes to the corresponding anilines in moderate to high yields. On the other hand, nitroalkanes are reduced to the corresponding diazo and hydrazo compounds under the studied conditions. The substantial measured primary kinetic isotope effects found here suggested that B-H bond cleavage occurs in a rate-determining step and [Au]-H active hybrids are formed, which are responsible for the reduction of nitroarenes to the corresponding amines. Formal Hammett-type kinetic analysis of a range of para-X-substituted nitroarenes lends support to this hypothesis. Nitro compounds substituted with electron-withdrawing groups were reduced faster than the corresponding compounds with electron-donating groups. The presence of water enhanced the catalytic activity of Au/MTA in aprotic solvents. Nuclear magnetic resonance studies support the formation of the corresponding hydroxylamines as the only intermediate products. On the basis of the high observed chemoselectivities and the fast and clean reaction processes, these catalytic systems, i.e., Au/MTA-NaBH4 and Au/MTA-TMDS, show promise for the efficient synthesis of aromatic amines at industrial levels.
- Fountoulaki, Stella,Daikopoulou, Vassiliki,Gkizis, Petros L.,Tamiolakis, Ioannis,Armatas, Gerasimos S.,Lykakis, Ioannis N.
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p. 3504 - 3511
(2015/02/19)
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- A concerted transfer hydrogenolysis: 1,3,2-diazaphospholene-catalyzed hydrogenation of Ni-34;N bond with ammonia-borane
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1,3,2-diazaphospholenes catalyze metal-free transfer hydrogenation of a Ni-34;N double bond using ammonia-borane under mild reaction conditions, thus allowing access to various hydrazine derivatives. Kinetic and computational studies revealed that the rate-determining step involves simultaneous breakage of the B-H and N-H bonds of ammonia-borane. The reaction is therefore viewed as a concerted type of hydrogenolysis. On the double: Diazaphospholenes catalyze the transfer hydrogenation of a Ni-34;N bond under mild reaction conditions, allowing access to various hydrazine derivatives. The catalytic cycle involves two key steps, and the catalyst maintains the PIII oxidation state throughout the catalytic cycle. The reaction mechanism involves a hydrogenolysis of the exocyclic P-N bond of the intermediate by ammonia-borane, and it proceeds in a concerted double-hydrogen-transfer fashion.
- Chong, Che Chang,Hirao, Hajime,Kinjo, Rei
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supporting information
p. 3342 - 3346
(2014/04/03)
-
- Mg/Triethylammonium formate: A useful system for reductive dimerization of araldehydes into pinacols; Nitroarenes into azoarenes and azoarenes into hydrazoarenes
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Studies are reported which describes the effectiveness of triethylammonium formate in the presence of magnesium for the efficient intermolecular pinacol coupling using MeOH as solvent, Various aromatic carbonyls underwent smooth reductive coupling to give the corresponding I ,2-diols. A series of azo compounds were obtained by the reductive coupling of nitroaromatics while azo compounds were reduced to the corresponding hydrazoarenes by this system. There was no adverse effect on the other reducible and hydrogenolysable groups such as ether linkage, hydroxy and halogens. The reactions are clean, high yielding and inexpensive. All the reactions proceeded smoothly at ambient temperature.
- Pamar, M. Geeta,Govender,Muthusamy,Krause, Ruiw M.,Nanjundaswamy
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p. 969 - 974
(2014/03/21)
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- Highly selective conversion of nitrobenzenes using a simple reducing system combined with a trivalent indium salt and a hydrosilane
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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
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scheme or table
p. 3173 - 3175
(2010/08/19)
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- Conversion of azobenzenes into N,N′-diarylhydrazines by sodium dithionite
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A number of chloro-, methyl- and methoxy-substituted azobenzenes have been reduced to the corresponding hydrazines by using an aqueous solution of Na 2S2O4. The yield is generally excellent, but two compounds, viz. 4,4-dimethoxyazobenzene and 2,2,4,4,6,6- hexamethylazobenzene, gave no hydrazine at all. Georg Thieme Verlag Stuttgart.
- Sydnes, Leiv K.,Elmi, Shire,Heggen, Per,Holmelid, Bjarte,Malthe-S?rensen, Didrik
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p. 1695 - 1698
(2007/12/28)
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- An efficient and product selective reduction of azoxyarenes into azoarenes or hydrazoarenes by tin/hydrazine hydrate
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A general and rapid method is described for the reduction of azoxyarenes to give the corresponding hydrazoarenes under microwave irradiation and azoarenes at reflux conditions on treatment with hydrazine hydrate in the presence of tin metal in methanol. The reactions are found to be fast and clean, give excellent yield and high purity of the products. Ether linkage and Cl are unaffected.
- Nanjundaswamy,Pasha
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p. 1086 - 1089
(2007/10/03)
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- Pyrazolidine-3,5-diones and 5-hydroxy-1H-pyrazol-3(2H)-ones, inhibitors of UDP-N-acetylenolpyruvyl glucosamine reductases
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A series of pyrazolidine-3,5-dione and 5-hydroxy-1H-pyrazol-3(2H)-one inhibitors of Escherichia coli UDP-N-acetylenolpyruvyl glucosamine reductase (MurB) has been prepared. The 5-hydroxy-1H-pyrazol-3(2H)-ones show low micromolar IC50 values versus E. coli MurB and submicromolar minimal inhibitory concentrations (MIC) against Staphylococcus aureus GC 1131, Enterococcus faecalis GC 2242, Streptococcus pneumoniae GC 1894, and E. coli GC 4560 imp, a strain with increased outer membrane permeability. None of these compounds show antimicrobial activity against Candida albicans, a marker of eukaryotic toxicity. Moreover, these compounds inhibit peptidoglycan biosynthesis, as assessed by measuring the amount of soluble peptidoglycan produced by Streptococcus epidermidis upon incubation with compounds. A partial least squares projection to latent structures analysis shows that improving MurB potency and MIC values correlate with increasing lipophilicity of the C-4 substituent of the 5-hydroxy-1H-pyrazol-3(2H)-one core. Docking studies using FLO and PharmDock produced several binding orientations for these molecules in the MurB active site.
- Gilbert, Adam M.,Failli, Amedeo,Shumsky, Jay,Yang, Youjun,Severin, Anatoly,Singh, Guy,Hu, William,Keeney, David,Petersen, Peter J.,Katz, Alan H.
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p. 6027 - 6036
(2007/10/03)
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- Facile, product-selective reduction of azoxyarenes into azoarenes or hydrazoarenes by aluminium/hydrazine hydrate
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Azoxyarenes, on treatment with hydrazine hydrate in presence of aluminium powder in methanol, undergo reduction. The reactions have been carried under microwave irradiation as well at reflux to get the corresponding hydrazoarenes and azoarenes as reduced products. The reaction is very fast, which gives excellent yield of the product. Substituents such as OCH3, OC 2H5, and Cl are unaffected. Copyright Taylor & Francis, Inc.
- Nanjundaswamy,Pasha
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p. 2163 - 2168
(2007/10/03)
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- A facile reduction of azoxyarenes with hydrazine hydrate/magnesium: Formation of different products under different reaction conditions
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Azoxyarenes on treatment with hydrazine hydrate in presence of magnesium turnings in methanol undergo reduction. The reactions have been carried under microwave irradiation as well as at reflux to give the corresponding hydrazoarenes and azoarenes as reduced products. The reactions are very fast and give excellent yields of the products. Substituents like OCH3, OC2H5 and Cl are unaffected.
- Nanjundaswamy, Hemmaragala M.,Pasha, Mohamed A.
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p. 772 - 774
(2007/10/03)
-
- 4-Alkyl and 4,4′-dialkyl 1,2-bis(4-chlorophenyl)pyrazolidine-3,5- dione derivatives as new inhibitors of bacterial cell wall biosynthesis
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Over 195 4-alkyl and 4,4-dialkyl 1,2-bis(4-chlorophenyl)pyrazolidine-3,5- dione derivatives were synthesized, utilizing microwave accelerated synthesis, for evaluation as new inhibitors of bacterial cell wall biosynthesis. Many of them demonstrated good a
- Kutterer, Kristina M.K.,Davis, Jamie M.,Singh, Guy,Yang, Youjun,Hu, William,Severin, Anatoly,Rasmussen, Beth A.,Krishnamurthy, Girija,Failli, Amedeo,Katz, Alan H.
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p. 2527 - 2531
(2007/10/03)
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- Chemoselective reduction of aromatic nitro and azo compounds in ionic liquids using zinc and ammonium salts
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Nitroarenes were chemoselectively reduced to the corresponding amines using zinc and aqueous ammonium salts in ionic liquids as a safe and recyclable reaction medium. Our results specify the effect of ammonium salts in the process; the combination of Zn/NH4Cl in [bmim][PF6] or Zn/HCO2NH4 in [bmim][BF4] were the suitable conditions for the reduction of nitroarenes. Azobenzenes were also smoothly reduced to hydrazobenzenes with Zn/HCO2NH4 (aq.) in recyclable [bmim][BF4] without any over reduction to the corresponding anilines.
- Khan, Faiz Ahmed,Dash, Jyotirmayee,Sudheer,Gupta, Rakesh Kumar
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p. 7783 - 7787
(2007/10/03)
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- A Simple and Efficient Method for the Reduction of Azo Compounds
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Reduction of azo compounds using hydrazine hydrate as reducant without catalyst is described, which proceeded smoothly in mild condition and did not pollute the environment.
- Zhang, Chang-Rui,Wang, Yu-Lu
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p. 4205 - 4208
(2007/10/03)
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- Reduction of aromatic azo-,azoxy- and nitro-compounds by ultrasonically activated nickel
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Substituted hydrazobenzenes were obtained in excellent yields from reduction of the corresponding azo- or azoxy- compounds by hydrazine hydrate under the catalysis of ultrasonically activated nickel (UAN). Reduction of nitroarenes by UAN produced azoxyarenes as the major products.
- Wang, Xiaolun,Xu, Minghua,Lian, Hongzhen,Pan, Yi,Shi, Yaozeng
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p. 3031 - 3037
(2007/10/03)
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- Reductive coupling of nitroarenes to hydrazoarenes with aluminium and potassium hydroxide in methanol
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A simple and inexpensive procedure for the reductive coupling of nitroarenes to hydrazoarenes with aluminium and potassium hydroxide in methanol at ambient temperature is reported. The coupling is proposed to proceed by single electron transfer from aluminium.
- Khurana, Jitender M.,Singh, Sarika
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p. 1893 - 1895
(2007/10/03)
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- Regiospecific acylations of aromatics and selective reductions of azobenzenes over hydrated zirconia
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Hydrated zirconia has been found to be an efficient and reusable catalyst for the regiospecific acylations of arenes and selective reductions of azobenzenes to produce benzophenones and hydrazabenzenes respectively.
- Patil,Jnaneshwara,Sabde,Dongare,Sudalai,Deshpande
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p. 2137 - 2140
(2007/10/03)
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- Pyridazinedione derivatives useful in treatment of neurological disorders
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The present invention relates to pyridazino[4,5-b]indoles, and pharmaceutically useful salts thereof, which are excitatory amino acid antagonists and which are useful when such antagonism is desired such as in the treatment of neurological disorders. The invention further provides pharmaceutical compositions containing pyridazino[4,5-b]indoles as active ingredient, and methods for the treatment of neurological disorders.
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- Convenient reduction of azobenzenes and azoxybenzenes to hydrazobenzenes by sodium dithionite using dioctylviologen as an electron transfer catalyst
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Various ezobenzenes and azoxybenzenes were reduced almost quantitatively to the corresponding hydrazobenzenes as sodium dithionite under mild conditions without the formation of aniline derivatives, using dioctyl viologen as an electron-transfer catalyst in acetonitrile-water.
- Park, Kwanghee Koh,Han, Sun Young
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p. 6721 - 6724
(2007/10/03)
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- Chemoselective reductive coupling of nitroarenes with magnesium in methanol via single electron transfer
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A chemoselective reductive coupling of nitroarenes using magnesium in methanol has been reported at ambient temperature. While the cyano, formyl, methoxycarbonyl, methyl, methoxy, phenyl, amino, and chloro groups are unaffected, iodo and bromo groups undergo dehalogenation but in a slower reaction than the coupling of nitro group. The coupling is believed to be proceeding via SET from Mg to nitroarenes.
- Khurana, Jitender M.,Ray, Abhijit
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p. 407 - 410
(2007/10/03)
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- Sodium Arenetellurolate Catalyzed Selective Conversion of Nitroaromatics to Aromatic Azoxy or Azo Compounds and Its Application for Facile Preparation of 3,3'- and 4,4'-Bisazobenzenes from (3- and 4-Nitrophenyl)acetylenes
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Treatment of aromatic nitro compounds with sodium borohydride in alkaline ethanol in the presence of a catalytic amount of diaryl ditelluride at room temperature affords the corresponding azoxy compounds selectively in fair to excellent yields.Under reflux aromatic azo compounds are obtained as major products.In situ generated sodium arenetellurolate (ArTeNa) is the active species to reduce nitroaromatics into aromatic nitroso compounds, the latter being easily converted into azoxy compounds in alkaline ethanol.Higher temperature enables ArTeNa to reduce the initially produced azoxy compounds into azo compounds.A new vinylic telluride having an azo group in the molecule, 3,3'-bisazobenzene, was prepared in one pot in 66-91percent isolated yield by treating (3-nitrophenyl)acetylene with a stoichiometric amount of ArTeNa in alkaline ethanol at reflux temperature, the structure of which was determined unambiguously by X-ray crystallography.The corresponding 4, 4'-isomer was similarly prepared, but in lower yield.
- Ohe, Kouichi,Uemura, Sakae,Sugita, Nobuyuki,Masuda, Hideki,Taga, Toru
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p. 4169 - 4174
(2007/10/02)
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- Studies of Reduction with the Sodium Borohydride-Transition Metal Boride System. I. Reduction of Nitro and Other Functional Groups with the Sodium Borohydride-Nickel Boride System
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Aromatic nitro, azoxy, azo and hydrazo compounds were reduced with the sodium borohydride-nickel boride system to the corresponding reduction products under mild conditions.Keywords- reduction; sodium borohydride; nickel boride; nitrobenzene; azoxy compound; azo compound; hydrazo compound; primary amine; sodium borohydride-nickel boride system
- Nose, Atsuko,Kudo, Tadahiro
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p. 1529 - 1533
(2007/10/02)
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- Heavy-Atom Kinetic Isotope Effects and Mechanism of the Acid-Catalyzed o-Semidine and p-Semidine Rearrangements and Disproportionation of 4,4'-Dichlorohydrazobenzene
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In acidic 60percent aqueous dioxane solution at 0 deg C, 4,4'-dichlorohydrazobenzene (18) undergoes concurrent disproportionation, to p-chloroaniline (19) and 4,4'-dichloroazobenzene (20), and o- (21) and p-semidine (22) rearrangement.In the p-semidine rearrangement one of the chlorine atoms of 18 is displaced, in essence, as Cl+.This requires participation of a second molecule of 18 in a redox reaction.The overall fate of 18, therefore, is to give 11percent o- and 12percent p-semidine rearrangement (along with 12percent of 20) and 60percent disproportionation, accounting for 95percent of the 18.Nitrogen and carbon kinetic isotope effects (KIE) have been determined for each of these reactions, using 18, 18, 18, and 18.Isotope ratios were obtained, measured on the trifluoroacetyl derivatives of 19, 21, and 22, with a combination of scintillation counting, whole-molecule-ion mass spectrometry (WMIMS), and isotope-ratio mass spectrometry (IRMS).Nitrogen KIE were obtained by WMIMS for two 15N atoms in disproportionation (1.0260) and p-semidine rearrangement (1.0282) and by IRMS for one (naturally abundant) 15N atom in disproportionation (1.0141) and o-(1.0155) and p-semide (1.0162) rearrangement. 13C (IRMS) and 14C KIE were measured for all reactions, but in no case was a KIE other than, effectively, unity obtained.These results show that o-semidine formation from 18 complies with exceptations of sigmatropic shifts; that is, that this 1,3-sigmatropic shift is not a concerted process.The results suggest that, although a concerted 1,5-sigmatropic shift is possible, the p-semidine rearrangement of 18 is not characterized by one.It this case, however, a firm decision is not possible.Finally, the results indicate that disproportionation involves one (or both) of the two semidine rearrangement intermediates.The most likely one is that of the p-semidine.Rapid redox reaction of this intermediate (26), formed in the rate-determining step, with a second molecule of 18 can then lead to the p-semidine by removal of Cl+ and to disproportionation by scission of the central C-C bond of the intermediate.These paths account for the distribution of the products formed and the KIE of their formation.
- Rhee, Eun Sook,Shine, Henry J.
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p. 1000 - 1006
(2007/10/02)
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