- Selective Reduction of Nitroarenes to Arylamines by the Cooperative Action of Methylhydrazine and a Tris(N-heterocyclic thioamidate) Cobalt(III) Complex
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We report an efficient catalytic protocol that chemoselectively reduces nitroarenes to arylamines, by using methylhydrazine as a reducing agent in combination with the easily synthesized and robust catalyst tris(N-heterocyclic thioamidate) Co(III) complex [Co(κS,N-tfmp2S)3], tfmp2S = 4-(trifluoromethyl)-pyrimidine-2-thiolate. A series of arylamines and heterocyclic amines were formed in excellent yields and chemoselectivity. High conversion yields of nitroarenes into the corresponding amines were observed by using polar protic solvents, such as MeOH and iPrOH. Among several hydrogen donors that were examined, methylhydrazine demonstrated the best performance. Preliminary mechanistic investigations, supported by UV-vis and NMR spectroscopy, cyclic voltammetry, and high-resolution mass spectrometry, suggest a cooperative action of methylhydrazine and [Co(κS,N-tfmp2S)3] via a coordination activation pathway that leads to the formation of a reduced cobalt species, responsible for the catalytic transformation. In general, the corresponding N-arylhydroxylamines were identified as the sole intermediates. Nevertheless, the corresponding nitrosoarenes can also be formed as intermediates, which, however, are rapidly transformed into the desired arylamines in the presence of methylhydrazine through a noncatalytic path. On the basis of the observed high chemoselectivity and yields, and the fast and clean reaction processes, the present catalytic system [Co(κS,N-tfmp2S)3]/MeNHNH2 shows promise for the efficient synthesis of aromatic amines that could find various industrial applications.
- Ioannou, Dimitris I.,Gioftsidou, Dimitra K.,Tsina, Vasiliki E.,Kallitsakis, Michael G.,Hatzidimitriou, Antonios G.,Terzidis, Michael A.,Angaridis, Panagiotis A.,Lykakis, Ioannis N.
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supporting information
p. 2895 - 2906
(2021/02/27)
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- Selective Photoinduced Reduction of Nitroarenes to N-Arylhydroxylamines
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We report the selective photoinduced reduction of nitroarenes to N-arylhydroxylamines. The present methodology facilitates this transformation in the absence of catalyst or additives and uses only light and methylhydrazine. This noncatalytic photoinduced transformation proceeds with a broad scope, excellent functional-group tolerance, and high yields. The potential of this protocol reflects on the selective and straightforward conversion of two general antibiotics, azomycin and chloramphenicol, to the bioactive hydroxylamine species.
- Kallitsakis, Michael G.,Ioannou, Dimitris I.,Terzidis, Michael A.,Kostakis, George E.,Lykakis, Ioannis N.
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supporting information
p. 4339 - 4343
(2020/06/08)
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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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- Catalyst-Free N-Deoxygenation by Photoexcitation of Hantzsch Ester
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A mild and operationally simple protocol for the deoxygenation of a variety of heteroaryl N-oxides and nitroarenes has been developed. A mixture of substrate and Hantzsch ester is proposed to result in an electron donor-acceptor complex, which upon blue-light irradiation undergoes photoinduced electron transfer between the two reactants to afford the products. N-oxide deoxygenation is demonstrated with 22 examples of functionally diverse substrates, and the chemoselective reduction of nitroarenes to the corresponding hydroxylamines is also shown.
- Cardinale, Luana,Jacobi Von Wangelin, Axel,Konev, Mikhail O.
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supporting information
(2020/02/15)
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- Selective hydrogenation of nitroaromatics to: N -arylhydroxylamines in a micropacked bed reactor with passivated catalyst
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In this contribution, a protocol was established for the selective catalytic hydrogenation of nitroarenes to the corresponding N-arylhydroxylamines. The reduction of 1-(4-chlorophenyl)-3-((2-nitrobenzyl)oxy)-1H-pyrazole, an intermediate in the synthesis of the antifungal reagent pyraclostrobin that includes carbon-chlorine bonds, benzyl groups, carbon-carbon double bonds and other structures that are easily reduced, was chosen as the model reaction for catalyst evaluation and condition optimization. Extensive passivant evaluation showed that RANEY-nickel treated with ammonia/DMSO (1 : 10, v/v) afforded the optimal result, especially with a particle size of 400-500 mesh. To combine the modified catalyst with continuous-flow reaction technology, the reaction was conducted at room temperature, rendering the desired product with a conversion rate of 99.4% and a selectivity of 99.8%. The regeneration of catalytic activity was also studied, and an in-column strategy was developed by pumping the passivate liquid overnight. Finally, the generality of the method was explored, and 7 substrates were developed, most of which showed a good conversion rate and selectivity, indicating that the method has a certain degree of generality.
- Chen, Jian-Li,Cheng, Peng-Fei,Jiang, Zhi-Jiang,Su, Wei-Ke,Xu, Feng,Yu, Zhi-Qun
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p. 28585 - 28594
(2020/08/25)
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- Synthesis of N-aryl and N-heteroaryl hydroxylamines via partial reduction of nitroarenes with soluble nanoparticle catalysts
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Polystyrene-supported ruthenium nanoparticles enable the selective hydrazine-mediated reduction of nitroarenes to hydroxylamine products in high yield and selectivity. Key to obtaining the hydroxylamine product in good yield was the use of organic solvents capable of solubilizing the polystyrene-supported nanoparticle catalyst. N-aryl and N-heteroaryl hydroxylamines are generated under exceptionally mild conditions and in the presence of a various easily reduced functional groups.
- Tyler, Jefferson H.,Nazari, S. Hadi,Patterson, Robert H.,Udumula, Venkatareddy,Smith, Stacey J.,Michaelis, David J.
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supporting information
p. 82 - 86
(2016/12/23)
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- Controllable Synthesis of Mesoporous Iron Oxide Nanoparticle Assemblies for Chemoselective Catalytic Reduction of Nitroarenes
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Iron(III) oxide is a low-cost material with applications ranging from electronics to magnetism, and catalysis. Recent efforts have targeted new nanostructured forms of Fe2O3 with high surface area-to-volume ratio and large pore volume. Herein, the synthesis of 3D mesoporous networks consisting of 4-5 nm γ-Fe2O3 nanoparticles by a polymer-assisted aggregating self-assembly method is reported. Iron oxide assemblies obtained from the hybrid networks after heat treatment have an open-pore structure with high surface area (up to 167 m2 g-1) and uniform pores (ca. 6.3 nm). The constituent iron oxide nanocrystals can undergo controllable phase transition from γ-Fe2O3 to α-Fe2O3 and to Fe3O4 under different annealing conditions while maintaining the 3D structure and open porosity. These new ensemble structures exhibit high catalytic activity and stability for the selective reduction of aryl and alkyl nitro compounds to the corresponding aryl amines and oximes, even in large-scale synthesis.
- Papadas, Ioannis T.,Fountoulaki, Stella,Lykakis, Ioannis N.,Armatas, Gerasimos S.
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supporting information
p. 4600 - 4607
(2016/03/22)
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- TRIFLUOROMETHOXYLATION OF ARENES VIA INTRAMOLECULAR TRIFLUOROMETHOXY GROUP MIGRATION
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The present invention provides a process of producing a trifluoromethoxylated aryl or trifluoromethoxylated heteroaryl having the structure: (I), wherein A is an aryl or heteroaryl, each with or without subsutitution; and R1 is -H, -(alkyl), -(alkenyl), -(alkynyl), -(aryl), -(heteroaryl), - (alkylaryl), - (alkylheteroaryl), -NH-(alkyl), -N(alkyl)2, -NH-(alkenyl), -NH-(alkynyl) -NH-(aryl), -NH-(heteroaryl), -O-(alkyl), -O-(alkenyl), -O-(alkynyl), -O-(aryl), -O-(heteroaryl), -S-(alkyl), -S- (alkenyl), -S-(alkynyl), -S-(aryl), or -S-(heteroaryl), comprising: (a) reacting a compound having the structure: (II), with a trifluoromethylating agent in the presence of a base in a first suitable solvent under conditions to produce a compound having the structure: (III); and (b) maintaining the compound produced in step (a) in a second suitable solvent under conditions sufficient to produce the trifluoromethoxylated aryl or trifluormethoxylated heteroaryl having the structure: (I).
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Page/Page column 65
(2016/05/02)
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- Mechanistic studies on intramolecular C-H trifluoromethoxylation of (hetero)arenes via OCF3-migration
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The one-pot two-step intramolecular aryl and heteroaryl C-H trifluoromethoxylation recently reported by our group has provided a general, scalable, and operationally simple approach to access a wide range of unprecedented and valuable OCF3-containing building blocks. Herein we describe our investigations to elucidate its reaction mechanism. Experimental data indicate that the O-trifluoromethylation of N-(hetero)aryl-N-hydroxylamine derivatives is a radical process, whereas the OCF3-migration step proceeds via a heterolytic cleavage of the N-OCF3 bond followed by rapid recombination of a short-lived ion pair. Computational studies further support the proposed ion pair reaction pathway for the OCF3-migration process. We hope that the current study would provide useful insights for the development of new transformations using versatile N-(hetero)aryl-N-hydroxylamine synthons.
- Lee, Katarzyna N.,Lei, Zhen,Morales-Rivera, Cristian A.,Liu, Peng,Ngai, Ming-Yu
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supporting information
p. 5599 - 5605
(2016/07/06)
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- Trifluoromethoxylation of arenes: Synthesis of ortho- Trifluoromethoxylated aniline derivatives by OCF3 migration
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Aryl trifluoromethoxylation by a two-step sequence of O-trifluoromethylation of N-aryl-N-hydroxylamine derivatives and intramolecular OCF3 migration is presented. This protocol allows easy access to a wide range of synthetically useful ortho-OCF3 aniline derivatives. In addition, it utilizes bench-stable reagents, is operationally simple, shows high functional-group tolerance, and is amenable to gram-scale as well as one-pot synthesis.Areaction mechanism of a heterolytic cleavage of the N-OCF3 bond followed by recombination of the resulting nitrenium ion and trifluoromethoxide is proposed for the OCF3-migration reaction.
- Hojczyk, Katarzyna N.,Feng, Pengju,Zhan, Chengbo,Ngai, Ming-Yu
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supporting information
p. 14559 - 14563
(2015/01/09)
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- The powerful effect of N-aryl substitution in promoting the thermal rearrangement of 5-spirocyclopropaneisoxazolidines
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N-Alkyl 5-spirocyclopropaneisoxazolidines rearrange to tetrahydropyridone derivatives by heating. The presence of a phenyl ring on the nitrogen atom significantly reduces the rearrangement temperature. This effect is enhanced by electron-donating substituents and reduced by electron- withdrawing substituents on the phenyl ring.
- Cordero, Franca M.,Barile, Ingrid,De Sarlo, Francesco,Brandi, Alberto
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p. 6657 - 6660
(2007/10/03)
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- Reduction of nitroarenes to N-arylhydroxylamines with KBH4/BiCl3 system
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Aromatic nitro compounds could be selectively and rapidly reduced to the corresponding N-arylhydroxylamines in good yields with KBH4/BiCl3 system under mild conditions.
- Ren, Ping-Da,Pan, Xin-Wei,Jin, Qi-Hui,Yao, Zi-Peng
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p. 3497 - 3503
(2007/10/03)
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- Synthesis of N-arylhydroxylamines by antimony-catalyzed reduction of nitroarenes
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Metallic antimony catalyzes the reduction of aromatic nitro compounds to the corresponding N-arylhydroxylamines in good yields with NaBH4 under mild conditions. The azoxybenzenes from autoxidation of N-arylhydroxylamines were also obtained in basic conditions.
- Ren, Pingda,Dong, Tingwei,Wu, Shihui
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p. 1547 - 1552
(2007/10/03)
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- A Fast Procedure for the Reduction of Azides and Nitro Compounds Based on the Reducing Ability of Sn(SR)3-Species
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Tin(II) complexes prepared by treatment of SnCl2 or Sn(SR)2 with appropriate amounts of RSH and Et3N appear to be the best reducing agents for azides (to amines) reported so far.Thes tin(II) complexes also reduce primary and secondary aliphatic nitro compounds to oximes, usually within minutes at r.t. or hours in cold, and tertiary aliphaic as well as aromatic nitro compounds to afford the corresponding hydroxylamines.In general, azides react more rapidly than nitro substituents, whereas carbonyl groups, sulphoxides, sulphones, nitriles, and esters are practically unreactive under the same conditions.Some mechanistic details of the reaction of Sn(SPh)3- with azides and nitro compounds have also been elucidated.
- Bartra, Marti,Romea, Pedro,Urpi, Felix,Vilarrasa, Jaume
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p. 587 - 594
(2007/10/02)
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- RUBREDOXIN MODEL COMPLEX (Et4N) AS A CATALYST IN THE REDUCTION OF AROMATIC NITRO COMPOUNDS TO HYDROXYLAMINES
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(Et4N), the analogue of oxidized rubredoxin active sites, can catalyze the reduction of aromatic nitro compounds to N-aryl hydroxylamines by o-xylene-α,α'-dithiol.
- Yanada, Kazuo,Nagano, Tetsuo,Hirobe, Masaaki
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p. 5113 - 5116
(2007/10/02)
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- 13C NMR studies of p-substituted nitrosobenzenes
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The 13C NMR spectra of a wide range of monomeric para-substituted nitrosobenzenes have been determined end the results related to a wide range of published data for other para-disubstituted benzenes.It is shown that the nitroso substituent exercises a different pattern of effect for the 13C chemical shifts at the ipso C atom from at least twenty eight other substituents.It is noted that when the para substituent is a ?-donor, the nitroso group functions in a different manner from that operative when the para substituent is a ?-acceptor, a general possibility that has already been suggested in the recent literature.
- Al-Tahou, Baheeja M.,Gowenlock, Brian G.
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p. 353 - 355
(2007/10/02)
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