- Highly efficient and selective photocatalytic hydrogenation of functionalized nitrobenzenes
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We report a simple but efficient photocatalytic nitrobenzene reduction method employing eosin Y as the photocatalyst and TEOA as the reducing agent. With green LED light irradiation, the nitro group in the nitrobenzenes containing other reducible groups was chemoselectively reduced into an amino group, and the corresponding anilines were isolated in quantitative yields. The photoinduced electron transfer mechanism suggests that the high chemoselectivity originates from the better electron-withdrawing ability of the nitro group.
- Yang, Xiu-Jie,Chen, Bin,Zheng, Li-Qiang,Wu, Li-Zhu,Tung, Chen-Ho
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- Catalytic Hydrogenation of Azobenzene in the Presence of a Cuboidal Mo3S4Cluster via an Uncommon Sulfur-Based H2Activation Mechanism
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Azobenzene hydrogenation is catalyzed under moderate conditions by a cuboidal Mo3(μ3-S)(μ-S)3 diamino complex via a cluster catalysis mechanism. Dihydrogen activation by the molecular [Mo3(μ3-S)(μ-S)3Cl3(dmen)3]+ cluster cation takes place at the μ-S bridging atoms without direct participation of the metals in clear contrast with classical concepts. The reaction occurs with the formation of 1,2-diphenylhydrazine as an intermediate with similar appearance and disappearance rate constants. On the basis of DFT calculations, a mechanism is proposed in which formation of 1,2-diphenylhydrazine and aniline occurs through two interconnected catalytic cycles that share a common reaction step that involves H2 addition to two of the bridging sulfur atoms of the catalyst to form a dithiolate Mo3(μ3-S)(μ-SH)2)(μ-S) adduct. Both catalytic cycles have similar activation barriers, in agreement with the experimental observation of close rate constant values. Microkinetic modeling of the process leads to computed concentration-time profiles in excellent agreement with the experimental ones providing additional support to the calculated reaction mechanism. Slight modifications on the experimental conditions of the catalytic protocol in combination with theoretical calculations discard a direct participation of the metal on the reaction mechanism. The effect of the ancillary ligands on the catalytic activity of the cluster fully agrees with the present mechanistic proposal. The results herein demonstrate the capability of molybdenum sulfide materials to activate hydrogen through an uncommon sulfur based mechanism opening attractive possibilities toward their applications as catalysts in other hydrogenation processes.
- Guillamón, Eva,Oliva, Mónica,Andrés, Juan,Llusar, Rosa,Pedrajas, Elena,Safont, Vicent S.,Algarra, Andres G.,Basallote, Manuel G.
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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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- Dissociative cycloelimination, a new selenium based pericyclic reaction
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The stereospecific oxidation of hydrazine into cis-diimide and the catalytic disproportionation of hydrogen peroxide effected by selenoxides are suggested to involve a dissociative cycloelimination from an intermediary selenurane.
- Henriksen,Jakobsen
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- Aryldiazonium Salts Serve as a Dual Synthon: Construction of Fully Substituted Pyrazoles via Rongalite-Mediated Three-Component Radical Annulation Reaction
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A highly efficient rongalite-mediated three-component radical annulation reaction to furnish fully substituted pyrazoles from aryldiazonium salts and α,β-unsaturated aldehydes or ketones under metal- and oxidant-free conditions at room temperature has been developed. In this transformation, aryldiazonium salts served as the precursor of both the aryl and aryl hydrazine units. Mechanistic investigations indicated that rongalite could act as a radical initiator and reducing reagent simultaneously in the reaction.
- Wang, Miao,Tang, Bo-Cheng,Xiang, Jia-Chen,Chen, Xiang-Long,Ma, Jin-Tian,Wu, Yan-Dong,Wu, An-Xin
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- μ-imido, μ-(η2,η2-N,N-hydrazido) and μ-(η1-C:η2-C,N-isocyanido) dinuclear (fulvalene)zirconium derivatives
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Treatment of the chloro (fulvalene)zirconium(III) compound [Zr(η5-C5H5)(μ-Cl)]2 [μ-(η5,η5-C10H8)] with an equimolar amount of azobenzene in toluene, under extremely anhydrous conditions, gives the μ-[bis(imido)] derivative [Zr(η5- C5H5)(μ-NPh)]2[μ-(η5, η5-C10H8)] (1). However, when this reaction is carried out under insufficiently dry conditions a mixture of the previously reported μ-oxo complex [Zr(η5- C5H5)Cl]2(μ-O)[μ-(η5, η5-C10H8)] and 1,2-diphenylhydrazine is obtained. When the chloro(fulvalene)zirconium(III) compound reacts with benzo[c]cinnoline the μ-(η2,η2-N,N-hydrazido) complex [Zr(η5-C5H5)Cl]2[μ- (NC6H4C6H4N)][μ (η5,η5-C10H8)] (2a) is obtained, which rearranges to the thermodynamically more stable 2b. Addition of an equimolar amount of RNC (R = nBu, C6H11) to a toluene solution of [Zr(η5-C5H5)(μ-Cl)]2 [μ-(η5,η5-C10H8)] gives [Zr(η5- C5H5)Cl]2(μ-CNR)[μ- (η5,η5-C10H8)] [R = nBu (3), C6H11 (4)]. Reaction of [Zr(η5-C5H5)Cl]2(μ-CNtBu) [μ-(η5,η5-C10H8)] with 1 equiv, of PhCH2MgCl or (PhCH2)2Mg(THF)2 afforded the monobenzyl derivatives [Zr(η5-C5H5)]2 (CH2Ph)(Cl)(μ-CNtBu) [μ-(η5,η5-C10H8)] (5 and 6). When this reaction was carried out with 2 equiv. or an excess of PhCH2MgCl, a mixture of the monobenzyl and dibenzyl compounds [Zr(η5- C5H5)]2(CH2Ph)(Cl) (μ-CNtBu)[μ-(η5,η5- C10H8)] (5) and [Zr(η5-C5H5) (CH2Ph)]2(μ-CNtBu)[μ-(η5, η5-C10H8)] (7) is obtained. Similar reactions with 1 or 2 equiv. of (CH3)3SiCH2Li afford a mixture of the monoalkyl and dialkyl compounds [Zr(η5-C5H5)]2 [CH2Si(CH3)3](Cl)(μ-CNtBu) [μ-(η5,η5-C10H8)] (8) and {Zr(η5-C5H5)[CH2Si (CH3)3]}2(μ-CNtBu) [μ-(η5,η5- C10H8)] (9) compounds. Moreover, methylation of [Zr(η5- C5H5)Cl]2(μ-CNnBu) [μ-(η5,η5-C10H8)] gives the analytically pure tetramethyl derivative [Zr(η5-C5H5) (CH3)]2(μ-CNnBu) [μ-(η5,η5-C10H8)] (10), whereas [Zr(η5-C5H5)Cl]2(μ- CNC6H11)[μ-(η5, μ5-C10H8)] reacts with MeLi to give a mixture of the monomethyl derivatives [Zr(η5C5H5)]2 (CH3)(Cl)(μ-CNC6H11)[μ- (η5,η5-C10H8)] (11 and 12), as well as the dimethyl compound [Zr(η5-C5H5) (CH3)]2(μ- CNC6H11)[μ-(η5, η5-C10H8)] (13). Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Gonzalez-Maupoey, Marta,Rodriguez, Gema M.,Cuenca, Tomas
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- N=N bond cleavage of azobenzene through Pt/TiO2 photocatalytic reduction
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TiO2 photocatalytic 2e--reduction of azobenzene to hydrazobenzene is found to occur at λ(ex) > 300 nm while loading of nanometer-sized Pt particles on TiO2 induces N=N bond cleavage via 4e--reduction; only photoisomerization occurs in the absence of TiO2.
- Tada, Hiroaki,Kubo, Masanobu,Inubushi, Yoichi,Ito, Seishiro
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- Highly efficient and selective photocatalytic reduction of nitroarenes using the Ni2P/CdS catalyst under visible-light irradiation
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A highly efficient and selective heterogeneous photocatalytic system for nitro reduction to amino organics was established using CdS, Ni2P and Na2S/Na2SO3 as a photosensitizer, a cocatalyst and a sacrificial electron donor in aqueous solution, respectively. Two competing pathways for photocatalytic H2 production and nitro reduction were found. Also, the reduction of nitroarenes to aniline was confirmed to proceed through both the direct and condensation routes.
- Gao, Wen-Zheng,Xu, Yong,Chen, Yong,Fu, Wen-Fu
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- Using a Nitrophenol Cocktail Screen to Improve Catalyst Down-selection
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The catalytic reduction of 4-nitrophenol (4NP) with excess NaBH4 is the benchmark model for quantifying catalytic activity of nanoparticles. Although broadly useful, the reaction can be very selective. This can lead to false positives and negatives when utilized for catalyst down-selection from a broader materials candidate pool. We report a multi-nitrophenol cocktail screening methodology incorporating 4NP and other amino-nitrophenols, utilizing Ag, Au, Pt, and Pd nanoparticles on carbon support. The reduction of the cocktail proceeds with no deleterious side reactions on the time-scale tested. The resulting kinetic rates provide an improved correlation of relative catalyst activity when compared to performance with other reducible moieties (e. g. azo bonds), or when compared to solely 4NP screening.
- Shultz, Lorianne R.,Hu, Lin,Feng, Xiaofeng,Jurca, Titel
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- The benzidine and diphenyline rearrangements revisited. 1-14C and 1,1′-13C2 kinetic isotope effects, transition state differences, and coupled motion in a 10-atom sigmatropic rearrangement
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KIE were measured for 1-14C-and 1,1′-13C2-labeling in the acid-catalyzed rearrangement of hydrazobenzene (1) to benzidine (2) and diphenyline (3). Small KIE were found for forming 2, but none were found for the formation of 3. The results are consistent with concerted formation of 2 and nonconcerted formation of 3. KIE were remeasured for 4-14C-, 4,4′-13C2-, and 15N,15N′-labeling and were found to differ in magnitude from KIE reported earlier. The results are, nevertheless, consistent with the concerted formation of 2 and nonconcerted formation of 3. The differences in transition states for these two processes are discussed. Quantitative measurements of product distributions gave 85% 2 and 15% 3.
- Subotkowski, Witold,Kupczyk-Subotkowska, Lidia,Shine, Henry J.
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- Reduction of Azo-, Azoxy-, and Nitrobenzenes by Dihydrolipoamide-Iron(II)
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Dihydrolipoamide (DHLAm) was found to be an effective reagent for the reduction of nitrobenzene derivatives in the presence of a catalytic amount of ferrous ion.Azo- and azoxybenzenes were reduced to hydrazobenzene without the formation of aniline, and nitrobenzene, nitrosobenzene, and phenylhydroxylamine were also reduced to aniline in good yields under mild conditions.The reduction was presumed to proceed through the complex formation between DHLAm, ferrous ion, and substrates.
- Kijima, Masashi,Nambu, Yoko,Endo, Takeshi,Okawara, Makoto
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- Highly efficient synthesis of aromatic azos catalyzed by unsupported ultra-thin Pt nanowires
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Aromatic azos were synthesized using unsupported ultra-thin platinum nanowires as catalysts under mild reaction conditions and the reaction mechanism was proposed.
- Hu, Lei,Cao, Xueqin,Chen, Liang,Zheng, Junwei,Lu, Jianmei,Sun, Xuhui,Gu, Hongwei
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- Photocatalytic hydrogenation of azobenzene to hydrazobenzene on cadmium sulfide under visible light irradiation
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Visible-light irradiation (λ 600 nm) of commercially-available CdS in alcohol successfully promotes hydrogenation of azobenzene to hydrazobenzene with more than 95% selectivity. This is promoted by strong adsorption of azobenzene to the photoformed zerovalent Cd species adjacent to the surface S vacancies on CdS; this leads to efficient reduction to hydrazobenzene.
- Shiraishi, Yasuhiro,Katayama, Miyu,Hashimoto, Masaki,Hirai, Takayuki
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- Synthesis of Functionalized Hydrazines: Facile Homogeneous (N-Heterocyclic Carbene)-Palladium(0)-Catalyzed Diboration and Silaboration of Azobenzenes
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The bis(N-heterocyclic carbene)(diphenylacetylene)palladium complex [Pd(ITMe)2(PhC≡CPh)] (ITMe=1,3,4,5-tetramethylimidazol-2-ylidene) acts as a highly active pre-catalyst in the diboration and silaboration of azobenzenes to synthesize a series of novel functionalized hydrazines. The reactions proceed using commercially available diboranes and silaboranes under mild reaction conditions. (Figure presented.).
- Ansell, Melvyn B.,Kostakis, George E.,Braunschweig, Holger,Navarro, Oscar,Spencer, John
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- Chemoselective Hydrogenation of Nitroarenes Using an Air-Stable Base-Metal Catalyst
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The reduction of nitroarenes to anilines as well as azobenzenes to hydrazobenzenes using a single base-metal catalyst is reported. The hydrogenation reactions are performed with an air-and moisture-stable manganese catalyst and proceed under relatively mild reaction conditions. The transformation tolerates a broad range of functional groups, affording aniline derivatives and hydrazobenzenes in high yields. Mechanistic studies suggest that the reaction proceeds via a bifunctional activation involving metal-ligand cooperative catalysis.
- Zubar, Viktoriia,Dewanji, Abhishek,Rueping, Magnus
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p. 2742 - 2747
(2021/05/05)
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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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- Manganese Catalyzed Hydrogenation of Azo (N=N) Bonds to Amines
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We report the first example of homogeneously catalyzed hydrogenation of the N=N bond of azo compounds using a complex of an earth-abundant-metal. The hydrogenation reaction is catalyzed by a manganese pincer complex, proceeds under mild conditions, and yields amines, which makes this methodology a sustainable alternative route for the conversion of azo compounds. A plausible mechanism involving metal-ligand cooperation and hydrazine intermediacy is proposed based on mechanistic studies. (Figure presented.).
- Ben-David, Yehoshoa,Das, Uttam Kumar,Diskin-Posner, Yael,Kar, Sayan,Milstein, David
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supporting information
p. 3744 - 3749
(2021/07/09)
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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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supporting information
p. 4804 - 4811
(2021/04/06)
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- Visible-light-promoted decarboxylative addition cyclization of: N -aryl glycines and azobenzenes to access 1,2,4-triazolidines
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Methods for the synthesis of 1,2,4-triazolidines are scarce. Herein, we report a visible-light-promoted decarboxylative addition cyclization of N-aryl glycines and azobenzenes to access such important compounds. Using commercially available methylene blue (MB) as an organic photocatalyst, the reaction proceeded smoothly in the absence of transition-metal catalysts at ambient temperature, affording the corresponding products, 1,2,4-triaryl 1,2,4-triazolidines, in good to excellent yields. This work demonstrates a new synthetic application of readily available azobenenes and provides a novel strategy for constructing 1,2,4-triazolidines.
- Ma, Ben,Qi, Yanfang,Song, Menghui,Wang, Xi-Cun,Yang, Jingya,Zhou, Hongyan
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supporting information
p. 5806 - 5811
(2021/08/23)
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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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- Microwave-assisted reduction of aromatic nitro compounds with novel oxo-rhenium complexes
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The reduction of several aromatic nitro compounds to amines by means of the two novel catalytic systems ([IMes]2ReOBr3)/PhSiH3 and ([Py]3ReNOBr2)/PhSiH3 under microwave irradiation is here reported. These two systems were able to perform the reduction of nitro groups with higher TON and TOF when compared with previously reported systems based on oxo-rhenium core under standard heating, although they showed a lesser broad reaction scope compared with the known systems.
- Blacque, Olivier,Grieco, Gabriele
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- Direct Synthesis of Indoles from Azoarenes and Ketones with Bis(neopentylglycolato)diboron Using 4,4′-Bipyridyl as an Organocatalyst
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Multifunctionalized indole derivatives were prepared by reducing azoarenes in the presence of ketones and bis(neopentylglycolato)diboron (B2nep2) with a catalytic amount of 4,4′-bipyridyl under neutral reaction conditions, where 4,4′-bipyridyl acted as an organocatalyst to activate the B-B bond of B2nep2 and form N,N′-diboryl-1,2-diarylhydrazines as key intermediates. Further reaction of N,N′-diboryl-1,2-diarylhydrazines with ketones afforded N-vinyl-1,2-diarylhydrazines, which rearranged to the corresponding indoles via the Fischer indole mechanism. This organocatalytic system was applied to diverse alkyl cyclic ketones, dialkyl, and alkyl/aryl ketones, including heteroatoms. Methyl alkyl ketones gave the corresponding 2-methyl-3-substituted indoles in a regioselective manner. This protocol allowed us to expand the preparation of indoles having high compatibility with not only electron-donating and electron-withdrawing groups but also N- and O-protecting functional groups.
- Misal Castro, Luis C.,Sultan, Ibrahim,Nishi, Kohei,Tsurugi, Hayato,Mashima, Kazushi
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p. 3287 - 3299
(2021/03/01)
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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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- Clean production process of hydrogenated azobenzene
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The invention discloses a clean production process of hydrogenated azobenzene, which comprises the following steps: 1) reducing nitrobenzene with hydrazine hydrate in an alkaline solution in the presence of polyethylene glycol by using a quinone compound as a catalyst to obtain azoxybenzene; and 2) reducing the azoxybenzene obtained in the step 1) with hydrazine hydrate in an alkaline solution inthe presence of polyethylene glycol by using Raney nickel as a catalyst to obtain the hydrogenated azoxybenzene. The clean production process of the hydrogenated azobenzene disclosed by the inventionis free of solid waste pollution, the alkali liquor can be repeatedly used, the alkali consumption can be greatly saved, and potential risks such as high temperature, high pressure, flammability, explosiveness and the like are avoided.
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Paragraph 0031-0032; 0034-0037; 0039-0042; 0044-0045
(2020/11/22)
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- Generating Potent C-H PCET Donors: Ligand-Induced Fe-to-Ring Proton Migration from a Cp*FeIII-H Complex Demonstrates a Promising Strategy
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Highly reactive organometallic species that mediate reductive proton-coupled electron transfer (PCET) reactions are an exciting area for development in catalysis, where a key objective focuses on tuning the reactivity of such species. This work pursues ligand-induced activation of a stable organometallic complex toward PCET reactivity. This is studied via the conversion of a prototypical Cp*FeIII-H species, [FeIII(η5-Cp*)(dppe)H]+ (Cp? = C5Me5-, dppe = 1,2-bis(diphenylphosphino)ethane), to a highly reactive, S = 1/2 ring-protonated endo-Cp*H-Fe relative, triggered by the addition of CO. Our assignment of the latter ring-protonated species contrasts with its previous reported formulation, which instead assigned it as a hypervalent 19-electron hydride, [FeIII(η5-Cp*)(dppe)(CO)H]+. Herein, pulse EPR spectroscopy (1,2H HYSCORE, ENDOR) and X-ray crystallography, with corresponding DFT studies, cement its assignment as the ring-protonated isomer, [FeI(endo-η4-Cp*H)(dppe)(CO)]+. A less sterically shielded and hence more reactive exo-isomer can be generated through oxidation of a stable Fe0(exo-η4-Cp*H)(dppe)(CO) precursor. Both endo- and exo-ring-protonated isomers are calculated to have an exceptionally low bond dissociation free energy (BDFEC-H ≈ 29 kcal mol-1 and 25 kcal mol-1, respectively) cf. BDFEFe-H of 56 kcal mol-1 for [FeIII(η5-Cp*)(dppe)H]+. These weak C-H bonds are shown to undergo proton-coupled electron transfer (PCET) to azobenzene to generate diphenylhydrazine and the corresponding closed-shell [FeII(η5-Cp*)(dppe)CO]+ byproduct.
- Schild, Dirk J.,Drover, Marcus W.,Oyala, Paul H.,Peters, Jonas C.
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supporting information
p. 18963 - 18970
(2020/11/13)
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- Hydrogenation reaction method
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The invention relates to a hydrogenation reaction method, and belongs to the technical field of organic synthesis. The hydrogenation reaction method provided by the invention comprises the following steps: carrying out a hydrogen transfer reaction on a hydrogen acceptor compound, pinacol borane and a catalyst in a solvent in the presence of proton hydrogen, so that the hydrogen acceptor compound is subjected to a hydrogenation reaction; the catalyst is one or more than two of a palladium catalyst, an iridium catalyst and a rhodium catalyst; the hydrogen acceptor compound comprises one or morethan two functional groups of carbon-carbon double bonds, carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogentriple bonds and epoxy. The method is mild in reaction condition, easy to operate, high in yield, short in reaction time, wide in substrate application range, suitable for carbon-carbon double bonds,carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogen triple bonds and epoxy functional groups, good in selectivity and high in reaction specificity.
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Paragraph 0034; 0249-0252
(2020/05/14)
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- Generalized Chemoselective Transfer Hydrogenation/Hydrodeuteration
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A generalized, simple and efficient transfer hydrogenation of unsaturated bonds has been developed using HBPin and various proton reagents as hydrogen sources. The substrates, including alkenes, alkynes, aromatic heterocycles, aldehydes, ketones, imines, azo, nitro, epoxy and nitrile compounds, are all applied to this catalytic system. Various groups, which cannot survive under the Pd/C/H2 combination, are tolerated. The activity of the reactants was studied and the trends are as follows: styrene'diphenylmethanimine'benzaldehyde'azobenzene'nitrobenzene'quinoline'acetophenone'benzonitrile. Substrates bearing two or more different unsaturated bonds were also investigated and transfer hydrogenation occurred with excellent chemoselectivity. Nano-palladium catalyst in situ generated from Pd(OAc)2 and HBPin extremely improved the TH efficiency. Furthermore, chemoselective anti-Markovnikov hydrodeuteration of terminal aromatic olefins was achieved using D2O and HBPin via in situ HD generation and discrimination. (Figure presented.).
- Wang, Yong,Cao, Xinyi,Zhao, Leyao,Pi, Chao,Ji, Jingfei,Cui, Xiuling,Wu, Yangjie
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supporting information
p. 4119 - 4129
(2020/08/10)
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- EffectiveN-methylation of nitroarenes with methanol catalyzed by a functionalized NHC-based iridium catalyst: a green approach toN-methyl amines
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Compound [IrBr(CO)2(κC-tBuImCH2PyCH2OMe)] featuring a flexible pyridine/OMe functionalized NHC ligand κ1C coordinated efficiently catalyzes the selectiveN-monomethylation of nitroarenes using methanol as both the reducing agent and the C1 source. A range of functionalized nitroarenes including heterocyclic or sterically hindered derivatives have been efficiently converted to the correspondingN-monomethyl amines in good yields at low catalyst loadings using sub-stoichiometric amounts of Cs2CO3as a base. Mechanistic investigations support a borrowing-hydrogen mechanism in which methanol acts as the hydrogen source and methylating agent. Further, the hydrogen transfer reduction of nitrobenzene to aniline under optimized reaction conditions should proceed through a direct mechanism involving nitrosobenzene andN-phenylhydroxylamine intermediates.
- González-Lainez, Miguel,Jiménez, M. Victoria,Passarelli, Vincenzo,Pérez-Torrente, Jesús J.
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p. 3458 - 3467
(2020/06/17)
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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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- 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
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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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- Highly efficient nitrobenzene and alkyl/aryl azide reduction in stainless steel jars without catalyst addition
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The mechanochemical and selective reduction of aryl nitro and aryl/alkyl azide derivatives, with either formate salts or hydrazine, to the corresponding, synthetically useful amines occurs in excellent yields in a planetary ball mill without the addition of a catalyst. This newly developed and solvent-free protocol is efficient, fast and does not require the addition of a metal hydrogenation catalyst as the stainless steel jar itself fulfils that role. The method has been applied to a broad range of compounds and excellent yields have been obtained. The formylation of alkyl amines has been successfully performed, by means of mechanochemical activation, in the presence of ammonium formate alone.
- Martina, Katia,Baricco, Francesca,Tagliapietra, Silvia,Moran, Maria Jesus,Cravotto, Giancarlo,Cintas, Pedro
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supporting information
p. 18881 - 18888
(2018/11/26)
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- Reduction of nitroarenes, azoarenes and hydrazine derivatives by an organic super electron donor
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Reduction of nitrobenzene by excess organic electron donor, 12, affords diphenylhydrazine in a reaction where azobenzene oxide and azobenzene are likely intermediates. No cleavage of the N-N σ-bond is seen under photoactivation conditions, whereas traces are seen under thermal activation. Hydrazone derivatives were prepared to explore the cleavage of N-N σ-bonds; the results show that a low-lying LUMO assists the transition state for accepting an electron, and the stabilisation that the potential fragments from N-N bond cleavage afford to the fragments is important in determining whether cleavage is observed.
- Cumine, Florimond,Palumbo, Fabrizio,Murphy, John A.
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p. 5539 - 5545
(2018/05/07)
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- HYDROGENATION METHOD AND MANUFACTURING METHOD OF ORGANIC COMPOUND
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PROBLEM TO BE SOLVED: To provide a hydrogenation method having no need for separation of a catalyst after a hydrogenation reaction and capable of recycling the catalyst. SOLUTION: There is provided a hydrogenation method to an organic compound having a nitrogen with multiple bonds as a reaction point. The hydrogenation method has a process for adding a hydrogen atom to a nitrogen atom of an organic compound by a hydrogen supply module. The hydrogen supply module has a hydrogen separation layer containing a hydrogen separation metal selectively passing hydrogen from a hydrogen-containing gas. In the process for adding the hydrogen atom, hydrogen is supplied to the organic compound via a hydrogen separation layer. SELECTED DRAWING: Figure 1 COPYRIGHT: (C)2018,JPO&INPIT
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Paragraph 0072; 0073
(2018/10/19)
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- Strontium-mediated selective protonation of unsaturated linkage of aromatic hydrocarbons and these derivatives
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The selective protonation of aromatic hydrocarbons with at least two or more aromatic rings and aromatic compounds bearing unsaturated linkages can be achieved by metallic strontium metal with ammonium chloride and iodine, or ammonium iodide in tetrahydrofuran. The reaction system is ammonia-free in room temperature and the reaction proceeds high selectivity in moderate to good yields.
- Ohmura, Satoshi D.,Ueno, Masaharu,Miyoshi, Norikazu
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supporting information
p. 2268 - 2271
(2018/05/16)
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- Super electron donor-mediated reductive transformation of nitrobenzenes: A novel strategy to synthesize azobenzenes and phenazines
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The transformation of nitrobenzenes into azobenzenes by pyridine-derived super electron donor 2 is described. This method provides an efficient synthesis of azobenzenes because of not requiring the use of expensive transition-metals, toxic or flammable reagents, or harsh conditions. Moreover, when using 2-fluoronitrobenzenes as substrates, phenazines were found to be obtained. The process affords a novel synthesis of phenazines.
- Nozawa-Kumada, Kanako,Abe, Erina,Ito, Shungo,Shigeno, Masanori,Kondo, Yoshinori
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supporting information
p. 3095 - 3098
(2018/05/22)
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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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- B(C6F5)3-Promoted hydrogenations of N-heterocycles with ammonia borane
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A transition-metal-free method for the B(C6F5)3-promoted hydrogenations of N-heterocycles using ammonia borane under mild reaction conditions has been developed. The reaction affords a broad range of hydrogenated products in moderate to good yields. The enantioselective versions for the corresponding products were also investigated via our approach, showing good feasibility.
- Ding, Fangwei,Zhang, Yiliang,Zhao, Rong,Jiang, Yanqiu,Bao, Robert Li-Yuan,Lin, Kaifeng,Shi, Lei
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supporting information
p. 9262 - 9264
(2017/08/21)
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- Nickel oxide nanoparticles grafted on reduced graphene oxide (rGO/NiO) as efficient photocatalyst for reduction of nitroaromatics under visible light irradiation
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Nickel oxide nanoparticles were grafted on reduced graphene oxide via simultaneous reduction of graphene oxide and nickel salt in a single step reaction. The synthesized material (rGO/NiO) was found to be efficient visible light active photocatalyst for the reduction of nitroaromatic derivatives to their corresponding amino compounds. Hydrazine monohydrate provided necessary protons and electrons for the targeted reaction. After completion of the reaction, the photocatalyst could readily be recovered by simple external magnet and could be reused for six runs without any significant loss of its activity. More importantly, the photocatalyst did not show any leaching during the reaction as confirmed by ICP-AES analysis of the recovered catalyst.
- Al-Nafiey, Amer,Kumar, Anurag,Kumar, Malika,Addad, Ahmed,Sieber, Brigitte,Szunerits, Sabine,Boukherroub, Rabah,Jain, Suman L.
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p. 198 - 207
(2017/01/16)
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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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- Use of Catalytic Static Mixers for Continuous Flow Gas-Liquid and Transfer Hydrogenations in Organic Synthesis
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Catalytic static mixers were used for the continuous flow hydrogenation of alkenes, alkynes, carbonyls, nitro- and diazo-compounds, nitriles, imines, and halides. This technique relies on tubular reactors fitted with 3D printed static mixers which are coated with a catalytic metal layer, either Pd or Ni. Additive manufacturing of the metal mixer scaffold results in maximum design flexibility and is compatible with deposition methods such as metal cold spraying which allow for mass production and linear process scale up. High to full conversion was achieved for the majority of substrates, demonstrating the flexibility and versatility of the catalytic static mixer technology. In the example of an alkyne reduction, the selectivity of the flow reactor could be directed to either yield an alkene or alkane product by simply changing the reactor pressure.
- Hornung, Christian H.,Nguyen, Xuan,Carafa, Antony,Gardiner, James,Urban, Andrew,Fraser, Darren,Horne, Mike D.,Gunasegaram, Dayalan R.,Tsanaktsidis, John
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p. 1311 - 1319
(2017/09/23)
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- Highly selective reduction of nitroarenes to anilines catalyzed using MOF-derived hollow Co3S4 in water under ambient conditions
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We developed a new strategy for the efficient reduction of nitroarenes using sodium sulfide as reducing agent with MOF-derived Co3S4 as catalyst in water and at room temperature. The introduction of sodium sulfite enhanced the reactant conversion and product selectivity, and the as-synthesized catalyst was used repeatedly five times and retained its activity and selectivity. A wide spectrum of reducible functional moieties kept unaffected under the reaction conditions, and isotope labeling experiment showed the hydrogen atom was derived from water.
- Xu, Yong,Lv, Xiao-Jun,Chen, Yong,Fu, Wen-Fu
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- Multicomponent Coupling Cyclization Access to Cinnolines via in Situ Generated Diazene with Arynes, and α-Bromo Ketones
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A transition-metal-free multicomponent coupling cyclization reaction was explored involving arynes, tosylhydrazine, and α-bromo ketones. The reaction proceeds via a formal [2 + 2 + 2] cycloaddition, giving access to cinnoline derivatives in moderate yields under mild conditions. Three chemical bonds were formed-two C-N bonds and one C-C bond-in a single step.
- Shu, Wen-Ming,Ma, Jun-Rui,Zheng, Kai-Lu,Wu, An-Xin
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p. 196 - 199
(2016/02/03)
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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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- 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 0022; 0023; 0024; 0038; 0039; 0040
(2016/10/31)
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- Indium(III)-Catalyzed Reduction of Nitrobenzenes to Anilines: Scope and Limitations
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We have demonstrated that a combination of indium(III) iodide and 1,1,3,3-tetramethyldisiloxane (TMDS) effectively catalyzes the chemoselective reduction of nitrobenzenes with a variety of functional groups (halogens, alkyl, alkoxy, hydroxy, ester, amino, amide, cyanide, thiol, and an alkene moiety), producing the corresponding aniline derivatives.
- Sakai, Norio,Asama, Shun,Konakahara, Takeo,Ogiwara, Yohei
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p. 3179 - 3185
(2015/10/19)
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- Iridium-catalyzed transfer hydrogenation of nitroarenes to anilines
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A simple and general homogeneous catalyst system composed of commercially available [Ir(cod)Cl]2 and 1,10-phenanthroline has been developed for the selective transfer hydrogenation of nitroarenes to anilines. It utilized the readily accessible 2-propanol as a hydrogen donor and had wide substrate scope. A careful mechanistic investigation through real-time detection and a series of controlled experiments with possible intermediates was also carried out, which showed that the transformation proceeds via both phenylhydroxylamine and azobenzene intermediates and the reduction of hydrazobenzene leading to aniline might be the rate-determining step.
- Chen, Shujie,Lu, Guoping,Cai, Chun
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p. 5360 - 5365
(2015/07/07)
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- Photocatalytic secondary amine synthesis from azobenzenes and alcohols on TiO2 loaded with Pd nanoparticles
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Photoirradiation (λ > 300 nm) of TiO2 loaded with Pd nanoparticles (ca. 2 wt%, 5 nm diameter) in water containing alcohols and azobenzene derivatives at room temperature successfully produces the corresponding secondary amines with high yields.
- Selvam, Kaliyamoorthy,Sakamoto, Hirokatsu,Shiraishi, Yasuhiro,Hirai, Takayuki
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p. 2856 - 2860
(2015/04/22)
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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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p. 3342 - 3346
(2014/04/03)
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- One-pot preparation of azobenzenes from nitrobenzenes by the combination of an indium-catalyzed reductive coupling and a subsequent oxidation
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We demonstrated how a reduction step with a reducing system comprised of In(OTf)3 and Et3SiH and a subsequent oxidation that occurred under an ambient (oxygen) atmosphere allowed the highly selective and catalytic conversion of aromatic nitro compounds into symmetrical or unsymmetrical azobenzene derivatives. This catalytic system displayed a tolerance for the functional groups on a benzene ring: an alkyl group, a halogen, an acetyl group, an ester, a nitrile group, an acetyl group, an ester moiety, and a sulfonamide group.
- Sakai, Norio,Asama, Shun,Anai, Satsuki,Konakahara, Takeo
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p. 2027 - 2033
(2014/03/21)
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- Chemoselective deprotonative lithiation of azobenzenes: Reactions and mechanisms
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Whereas standard strong bases (n-BuLi, s-BuLi/TMEDA, n-BuLi/t-BuOK, TMPMgCl·LiCl, and LDA) reduce the N=N bond of the parent azobenzene (Y = H), aromatic H→Li permutation occurs with LTMP when a suitable director of lithiation (Y = OMe, CONEt2, F) is present in the benzene residue of the azo compound. The method allows direct access to new substituted azobenzenes.
- Nguyen, Thi Thanh Thuy,Boussonniere, Anne,Banaszak, Estelle,Castanet, Anne-Sophie,Nguyen, Kim Phi Phung,Mortier, Jacques
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p. 2775 - 2780
(2014/04/17)
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- Catalytic activation of hydrazine hydrate by gold nanoparticles: Chemoselective reduction of nitro compounds into amines
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Supported gold nanoparticles (2NH2 as a transfer hydrogenation agent. Aryl and alkyl nitro compounds are cleanly and selectively reduced into the corresponding amines in the presence of 4 equivalents of hydrazine. The reaction tolerates other potentially reducible functionalities such as carboxylate, carbonyl, cyano or halides which remain intact.
- Gkizis, Petros L.,Stratakis, Manolis,Lykakis, Ioannis N.
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