- Chemoselective electrochemical reduction of nitroarenes with gaseous ammonia
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Valuable aromatic nitrogen compounds can be synthesized by reduction of nitroarenes. Herein, we report electrochemical reduction of nitroarenes by a protocol that uses inert graphite felt as electrodes and ammonia as a reductant. Depending on the cell voltage and the solvent, the protocol can be used to obtain aromatic azoxy, azo, and hydrazo compounds, as well as aniline derivatives with high chemoselectivities. The protocol can be readily scaled up to >10 g with no decrease in yield, demonstrating its potential synthetic utility. A stepwise cathodic reduction pathway was proposed to account for the generations of products in turn.
- Chang, Liu,Li, Jin,Wu, Na,Cheng, Xu
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supporting information
p. 2468 - 2472
(2021/04/02)
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- 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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- 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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- Method for preparing 4, 4'-disubstituted-2, 2'-diaminodiphenyl and hydrochloride thereof through reductive coupling
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The invention discloses a method for preparing 4, 4'-disubstituted-2, 2'-diaminodiphenyl and hydrochloride thereof based on 4-substituted nitrobenzene and through reductive coupling. The method comprises the following steps: in the presence of an organic
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Paragraph 0055-0057; 0062-0064; 0069-0071; 0076-0078
(2020/09/09)
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- Synthesis of novel 1,2-diarylpyrazolidin-3-one–based compounds and their evaluation as broad spectrum antibacterial agents
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There is a continuous need to develop new antibacterial agents with non-traditional mechanisms to combat the nonstop emerging resistance to most of the antibiotics used in clinical settings. We identified novel pyrazolidinone derivatives as antibacterial hits in an in-house library screening and synthesized several derivatives in order to improve the potency and increase the polarity of the discovered hit compounds. The oxime derivative 24 exhibited promising antibacterial activity against E. coli TolC, B. subtilis and S. aureus with MIC values of 4, 10 and 20 μg/mL, respectively. The new lead compound 24 was found to exhibit a weak dual inhibitory activity against both the E. coli MurA and MurB enzymes with IC50 values of 88.1 and 79.5 μM, respectively, which could partially explain its antibacterial effect. A comparison with the previously reported, structurally related pyrazolidinediones suggested that the oxime functionality at position 4 enhanced the activity against MurA and recovered the activity against the MurB enzyme. Compound 24 can serve as a lead for further development of novel and safe antibiotics with potential broad spectrum activity.
- Abadi, Ashraf H.,Abdel-Halim, Mohammad,El-Sharkawy, Lina Y.,Engel, Matthias,Fathalla, Reem K.,Mokbel, Salma A.
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- 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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- 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
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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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- Bi(I)-Catalyzed Transfer-Hydrogenation with Ammonia-Borane
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A catalytic transfer-hydrogenation utilizing a well-defined Bi(I) complex as catalyst and ammonia-borane as transfer agent has been developed. This transformation represents a unique example of low-valent pnictogen catalysis cycling between oxidation states I and III, and proved useful for the hydrogenation of azoarenes and the partial reduction of nitroarenes. Interestingly, the bismuthinidene catalyst performs well in the presence of low-valent transition-metal sensitive functional groups and presents orthogonal reactivity compared to analogous phosphorus-based catalysis. Mechanistic investigations suggest the intermediacy of an elusive bismuthine species, which is proposed to be responsible for the hydrogenation and the formation of hydrogen.
- Wang, Feng,Planas, Oriol,Cornella, Josep
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supporting information
p. 4235 - 4240
(2019/04/17)
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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
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supporting information
p. 4189 - 4193
(2019/08/07)
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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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- 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.
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Paragraph 0053; 0054; 0055
(2016/10/31)
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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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- 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)
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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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