- 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
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supporting information
p. 2468 - 2472
(2021/04/02)
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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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- 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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- 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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- 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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- When Do Strongly Coupled Diradicals Show Strongly Coupled Reactivity? Thermodynamics and Kinetics of Hydrogen Atom Transfer Reactions of Palladium and Platinum Bis(iminosemiquinone) Complexes
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The 2,2′-biphenylene-bridged bis(iminosemiquinone) complexes (tBuClip)M [tBuClipH4 = 4,4′-di-tert-butyl-N,N′-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-2,2′-diaminobiphenyl; M = Pd, Pt] can be reduced to the bis(aminophenoxide) complexes (tBuClipH2)M by reaction with hydrazobenzene (M = Pd) or by catalytic hydrogenation (M = Pt). The palladium complex with one aminophenoxide ligand and one iminosemiquinone ligand, (tBuClipH)Pd, is generated by comproportionation of (tBuClip)Pd with (tBuClipH2)Pd in a process that is both slow (0.06 M-1 s-1 in toluene at 23 °C) and only modestly favorable (Kcom = 1.9 in CDCl3), indicating that both N-H bonds have essentially the same bond strength. The mono(iminoquinone) complex (tBuClipH)Pt has not been observed, indicating that the platinum analogue shows no tendency to comproportionate (Kcom tBuClipH2)Pt to (tBuClip)Pd occurring with ?G° = ?8.9 kcal mol-1. The palladium complex (tBuClipH2)Pd reacts with nitroxyl radicals in two observable steps, with the first hydrogen transfer taking place slightly faster than the second. In the platinum analogue, the first hydrogen transfer is much slower than the second, presumably because the N-H bond in the monoradical complex (tBuClipH)Pt is unusually weak. Using driving force-rate correlations, it is estimated that this bond has a BDFE of 55.1 kcal mol-1, which is 7.1 kcal mol-1 weaker than that of the first N-H bond in (tBuClipH2)Pt. The two radical centers in the platinum, but not the palladium, complex thus act in concert with each other and display a strong thermodynamic bias toward two-electron reactivity. The greater thermodynamic and kinetic coupling in the platinum complex is attributed to the stronger metal-ligand ? interactions in this compound.
- Conner, Kyle M.,Arostegui, AnnaMaria C.,Swanson, Daniel D.,Brown, Seth N.
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p. 9696 - 9707
(2018/08/28)
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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.
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Paragraph 0059; 0060; 0061
(2016/10/31)
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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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- 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 nitro compounds using samarium metal in the presence of a catalytic amount of iodine under aqueous media
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In the presence of a catalytic amount of iodine, aromatic nitro compounds can be reduced to the corresponding primary amines and hydrazines in good yields with Sm/THF-NH4Cl (aq.) system at room temperature. The primary amine is in the majority and the halogen, amido substituents on aromatic ring are unaffected during the reaction.
- Wang, Lei,Zhou, Longhu,Zhang, Yongmin
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p. 1065 - 1066
(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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- 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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- 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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- Photobenzidine Rearrangements. 6. Mechanism of the Photodecomposition of 1,4-Diaryl-1,4-dialkyl-2-tetrazenes
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The photodecomposition of the tetrazene p-XC6H4N(Me)N=N(Me)NC6H4Y-p (1e,X=Y=Me) in dimethoxyethane (DME) gave 47.4percent of p-XC6H4(Me)NN(Me)C6H4Y-p (2e,X=Y=Me) and 39.6 percent of N-methyl-p-toluidine. When irradiation was carried out in the presence of increasing initial concentrations of n-BuSH, the yield of 2e fell and levelled off at 6percent.Similar experiments in cyclohexane showed that the yield of 2e fell from 45.1percent and leveled off at 10percent.The data indicate that 1e decomposes by a radical pathway and that the 2e is formed partly within and partly outside of a solvent cage. Similar studies with 1d(X=Me, Y=CO2Et) in DME gave three hydrazines: 2d(X=Me,Y=CO2Et) in 13percent and 14.7percent yield, 2e in 7.3percent and 8.0percent yield,and 2f(X=Y=CO2Et) in 14.9percent and 21.2percent yield. The formation of three hydrazines again indicates the formation and intermolecular recombination of methylarylamino radicals. Irradiation of 1d in DME solutions containing n-BuSH caused a fall in the yield of 2e to zero and a leveling off in the yield of 2d to 6percent. The yield of 2f also fell but could not be monitored at high concentrations of n-BuSH because of overlapping high-pressure LC peaks. The results with 1d are also consistent with a cage-recombination process (for 2d) and an intermolecular recombination of radicals (for 2d-f). The methylarylamines p-XC6H4NHMe and p-YC6H4NHMe (X=Me; Y=CO2Et) were also formed from 1d. A sixth product was the bis(arylamino)methane p-YC6H4NHCH2NHC6H4Y-p(4f, Y=CO2Et) in 14-32percent yield (three runs). The origin of 4f is believed to be the disproportionation of radicals p-YC6H4NMe, giving p-YC6H4NHMe and p-YC6H4N=CH2(7f). Hydrolysis of 7f (by small amounts of water in the solvent) to p-YC6H4NH2 (6f) and HCHO followed by addition of 6f to 7f would give 4f. HCHO was found as a volatile product after irradiation. The formation of 4f is further evidence for the formation and intermolecular reaction of arylamino radicals in the photodecomposition of 1,4-dialkyl-1,4-diaryl-2-tetrazenes.
- Bae, Dong-Hak,Shine, Henry J.
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p. 4448 - 4455
(2007/10/02)
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