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Copper nanoparticles (CuNPs) catalyzed chemoselective reduction of nitroarenes in aqueous medium
Abstract: A procedure for practical synthesis of CuNPs from CuSO4·5H2O is established, under appropriate reaction conditions, using rice (Oryza sativa) as an economic source of reducing as well as a stabilizing agent. Optical and microscopic techniques are employed for the characterization of the synthesized CuNPs and the sizes of the particles were found to be in the range of 8 ± 2 nm. The nanoparticles are used as a catalyst for chemoselective reduction of aromatic nitro compounds to corresponding amines under ambient conditions and water as a reaction medium. Graphic abstract: CuNPs are synthesized using hydrolysed rice and used as catalyst for chemoselective reduction of nitroarenes to their corresponding amines in water. [Figure not available: see fulltext.]
Chand, Dillip Kumar,Rai, Randhir
(2021/08/20)

Selective reduction of nitro-compounds to primary amines by tetrapyridinoporphyrazinato zinc (II) supported on DFNS
Here, we created and synthesized a heterogeneous catalyst from porphyrazinatozinc (tmtppa-Zn) supported on DFNS (tmtppa-Zn/DFNS). This is a simple method for hydrogenation of nitro-compounds and their conversion to primary amines without producing toxic by-products. These reactions take place under mild reaction situations. The catalyst system was comfortably retrieved and reutilized in at least ten runs without the reduction of catalytic activity.
Hosseiny, Malihesadat,Khosroyar, Susan,Kiani, Zahra,Motavalizadehkakhky, Alireza,Zhiani, Rahele
(2021/06/14)

Cobalt oxide NPs immobilized on environmentally benign biological macromolecule-derived N-doped mesoporous carbon as an efficient catalyst for hydrogenation of nitroarenes
Highly nitrogen-doped mesoporous carbon (N-mC) material incorporated cobalt oxide nanoparticles was synthesized through simple pyrolysis of environmentally friendly chitosan-polyaniline-Co(OAc)2 precursor in one-step. The as-prepared catalyst named CoO&at;N-mC with 14.65 ?wtpercent nitrogen content was characterized by different analysis techniques. The heterogeneous catalyst exhibits outstanding catalytic activity for the reduction of a variety of nitroaromatic compounds in the presence of NaBH4 as a reducing agent in water as a green solvent at 75 ?°C. Utilization of natural biological macromolecules such as chitosan as green and cheap starting material with harmless aniline and earth-abundant cobalt salt, facile synthesis, excellent product yield, short reaction time, high chemoselectivity, sustainable and mild reaction condition, and reusability of catalyst for at least five cycles without any significant decline in the catalytic efficiency are some prominent merits of this new nanocatalyst.
Elhampour, Ali,Nanadegani, Zahra Soleimani,Nemati, Firouzeh,Rangraz, Yalda
(2020/09/15)

Palladium Supported on Carbon Nanoglobules as a Promising Catalyst for Selective Hydrogenation of Nitroarenes
The catalysts 1?wt% palladium supported on carbon nanoglobules (CNGs) were shown to be highly active in the liquid-phase hydrogenation of various nitroarenes and provided nearly 100% selectivity to aromatic amines at complete conversion under mild conditions (323?K, 0.5?MPa, 1?h). The catalytic activity (in terms of turnover frequency and substrate conversion) and selectivity depend on the kind of CNGs support, catalyst preparation method and the reaction conditions (solvent nature). The Pd/CNGs catalyst can be repeatedly used while maintaining the same catalytic performance. The excellent performances of Pd/CNGs catalysts can be due to the globular morphology of the supports as well as the absence of micropores and pronounced surface defects. Graphic Abstract: [Figure not available: see fulltext.]
Mironenko,Belskaya,Stepanova,Gulyaeva,Trenikhin,Likholobov
p. 888 - 900
(2019/11/11)

Differences in the selective reduction mechanism of 4-nitroacetophenone catalysed by rutile- And anatase-supported ruthenium catalysts
Ru/TiO2 catalysts exhibit excellent catalytic performance for selective reduction of 4-nitroacetophenone to 4-aminoacetophenone at normal temperature and atmospheric hydrogen pressure. Moreover, 99.9% selectivity to 4-aminoacetophenone can be obtained over 2.7 wt% Ru/TiO2(anatase) catalyst even in a relatively wide temperature (55-115 °C) and time (1-12 h) range. Its excellent catalytic performance is derived from the activation of H2 on the Ru nanoparticles at atmospheric pressure and the strong interaction of nitro groups with the support surface. Additionally, Ru nanoparticles supported on different crystalline TiO2 phases (anatase and rutile) result in different reaction pathways for 4-nitroacetophenone. Since the Ti-Ti distance on the rutile surface is smaller than that on the anatase surface, the hydroxylamine species adsorbed on the Ti atoms of rutile are more susceptible to the coupling reaction. Therefore, Ru/TiO2(rutile) causes a series of intermediates to accumulate during the conversion process, while Ru/TiO2(anatase) allows the highly selective conversion of 4-nitroacetophenone to 4-aminophenone. In addition, Ru/TiO2(anatase) can achieve chemoselective reduction of nitroaromatics to the corresponding anilines in the presence of -CN, -CHO, and -COOH, especially nitroaromatics containing CC and CC, indicating the excellent applicability.
Gu, Xianmo,Pei, Linjuan,Wang, Jie,Zhang, Jin,Zheng, Zhanfeng,Zhu, Pengqi
p. 1518 - 1528
(2020/03/26)

Acceptorless dehydrogenative oxidation of primary alcohols to carboxylic acids and reduction of nitroarenes via hydrogen borrowing catalyzed by a novel nanomagnetic silver catalyst
A novel silver nano magnetic catalyst was devised for dehydrogenative oxidation of aromatic and aliphatic alcohols to the corresponding acid with water as the sole oxygen source and hydrogen gas as the only by-product. The designed catalytic system advantages from easy recovery of magnetic materials i.e. magnetic decantation, being economically viable and environmentally friendly. Furthermore, the catalytic reaction is able to reduce aryl nitro compounds in the absence of any reducing agent.
Yazdani, Elahe,Heydari, Akbar
supporting information

(2020/08/14)

A polyamine dendritic polymer-copper complex: A reusable catalyst for the additive-free amination of aryl bromides, and iodides
A porphyrin-initiated amine-functionalized polyepichlorohydrin dendritic polymer (PPECH-Amine) was effectively synthesized, and its water-soluble copper complex (PPECH-Amine-Cu) was developed by treating it with copper acetate. PPECH-Amine and PPECH-Amine-Cu were characterised by different spectroscopic and microscopic techniques. PPECH-Amine-Cu was identified as a reusable catalyst for the amination of bromo- and iodo-benzene derivatives in aqueous media. Due to the presence of residual amino groups in the PPECH-Amine-Cu catalyst, the protocol does not need any additional base additive, as ammonia itself acts as a base and a coupling partner. Due to the good water-soluble nature of this catalyst, it can be easily separated and reused up to six reaction cycles without any loss in its activity.
Avudaiappan,Palmurukan,Unnikrishnan,Sreekumar
p. 1477 - 1484
(2020/02/05)

Phase and shape dependent photoactivity of titania for nitroaromatics reduction under UV light irradiation
This work describes importance of TiO2 nanostructures of different shapes (nanospheres and nanorods) and crystal phases (anatase and rutile) for the photoreduction of nitroaromatics into corresponding aminoaromatics under UV light irradiation. Anatase nanoparticles were most active of all the catalysts due to the superior stability of this phase and comparatively the rutile nanorods (L×W = 28-30 nm×3.5-3.8 nm) showed superior photoactivity (～3 times) as compared to rutile nanospheres of size 122 nm for the photoreduction due to electron transport along longitudinal length, larger surface area (69 m2g-1), quenched PL emission, increased lifetime of charge carriers (1.8 ns) of rutile nanorods as compare to rutile nanospheres having lower surface area (18 m2g-1) and charge carrier lifetime (1.1 ns). The overall rate of reduction/hour for m-NBA and m-NT photoreduction with all of these catalysts has been found to vary in the following order ANP > P25-TiO2 > RNR > ANR > RNP.
Kaur, Jaspreet,Pal, Bonamali
p. 803 - 809
(2018/12/14)

Synergistic Effects of ppm Levels of Palladium on Natural Clinochlore for Reduction of Nitroarenes
Augmenting the modified naturally occurring clay clinochlore with ppm amounts of palladium leads to a new and very effective reagent for the reduction of numerous aromatic nitro species. When palladium nanoparticles are supported on pyridyltriazole-modified clinochlore, iron within clinochlore acts synergistically with palladium to catalyze the reduction of a wide variety of nitroarenes at room temperature in aqueous media. Based on E-factor calculations, the catalyst system is found to be in line with green chemistry standards and can be recycled up to five times.
Gholinejad, Mohammad,Oftadeh, Erfan,Shojafar, Mohammad,Sansano, José M.,Lipshutz, Bruce H.
p. 4240 - 4248
(2019/09/06)

Sodium Methyl Carbonate as an Effective C1 Synthon. Synthesis of Carboxylic Acids, Benzophenones, and Unsymmetrical Ketones
Reported is the synthesis of carboxylic acids, symmetrical ketones, and unsymmetrical ketones with selectivity achieved by exploiting the differential reactivity of sodium methyl carbonate with Grignard and organolithium reagents.
Hurst, Timothy E.,Deichert, Julie A.,Kapeniak, Lucas,Lee, Roland,Harris, Jesse,Jessop, Philip G.,Snieckus, Victor
supporting information
p. 3882 - 3885
(2019/06/07)

Palladium complex containing diphosphine m-carborane ligand as well as preparation and application of palladium complex
The invention relates to a palladium complex containing a diphosphine m-carborane ligand as well as a preparation and an application of the palladium complex. The preparation method of the palladium complex comprises the following steps of 1) adding an n-BuLi solution into a m-carborane solution, and then reacting for 30-60 minutes at a room temperature; 2) adding diphenyl phosphorus chloride, andreacting for 3-6 h at the room temperature; and 3) adding PdCl2, reacting at the room temperature for 3-5 hours, and carrying out post-treatment to obtain the palladium complex. The palladium complexis used for catalyzing the reaction of halohydrocarbon with carbon dioxide to synthesize carboxylic acid. Compared with the prior art, the synthesis process is simple and green, and has the excellentselectivity and high yield; the palladium complex has the stable physicochemical properties and is used as the catalyst, the halogenated hydrocarbon is used as a substrate, the palladium complex andthe halogenated hydrocarbon are jointly dissolved in toluene, and the carbon dioxide is introduced at the normal pressure for reaction, so that the corresponding carboxylic acid can be synthesized athigh yield.
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Paragraph 0063-0066

(2019/12/02)

Visible-Light-Driven Chemoselective Hydrogenation of Nitroarenes to Anilines in Water through Graphitic Carbon Nitride Metal-Free Photocatalysis
Green and efficient procedures are essential for the chemoselective hydrogenation of functionalized nitroarenes to form industrially important anilines. Herein, it is shown that visible-light-driven, chemoselective hydrogenation of functionalized nitroarenes with groups sensitive to forming anilines can be achieved in good to excellent yields (82–100 %) in water under relatively mild conditions and catalyzed by low-cost and recyclable graphitic carbon nitride. The process is also applicable to gram-scale reaction, with a yield of aniline of 86 %. A study of the mechanism reveals that visible-light-induced electrons are responsible for the hydrogenation reactions, and thermal energy can also promote the photocatalytic activity. A study of the kinetics shows that this reaction possibly occurs through one-step hydrogenation or stepwise condensation routes. A wide range of applications can be expected for this green, efficient, and highly selective photocatalysis system in reduction reactions for the synthesis of fine chemicals.
Xiao, Gang,Li, Peifeng,Zhao, Yilin,Xu, Shengnan,Su, Haijia
p. 1950 - 1955
(2018/07/31)

Mechanochemical catalytic transfer hydrogenation of aromatic nitro derivatives
Mechanochemical ball milling catalytic transfer hydrogenation (CTH) of aromatic nitro compounds using readily available and cheap ammonium formate as the hydrogen source is demonstrated as a simple, facile and clean approach for the synthesis of substituted anilines and selected pharmaceutically relevant compounds. The scope of mechanochemical CTH is broad, as the reduction conditions tolerate various functionalities, for example nitro, amino, hydroxy, carbonyl, amide, urea, amino acid and heterocyclic. The presented methodology was also successfully integrated with other types of chemical reactions previously carried out mechanochemically, such as amide bond formation by coupling amines with acyl chlorides or anhydrides and click-type coupling reactions between amines and iso(thio)cyanates. In this way, we showed that active pharmaceutical ingredients Procainamide and Paracetamol could be synthesized from the respective nitro-precursors on milligram and gram scale in excellent isolated yields.
Portada, Tomislav,Margeti?, Davor,?trukil, Vjekoslav
supporting information

(2018/12/11)

Synthesis method of pharmaceutical intermediate m-aminobenzoic acid
The invention relates to a synthesis method of a pharmaceutical intermediate m-aminobenzoic acid. The synthesis method mainly comprises: adding 3 mol cuprous chloride, 4-5 mol toluene solution and 5 mol m-nitrobenzoic acid solution to a reaction container, heating the solution to a temperature of 60-70 DEG C, controlling the stirring speed at 110-130 rpm, maintain for 90-110 min, adjusting the pHvalue of the solution to 9-10 with a sodium hydroxide solution, cooling the solution to a temperature of 5-10 DEG C, crystallizing, adding 6 L ethanol solution, washing, washing with a sodium chloridesolution, washing with a nitromethane solution, washing with an ethylenediamine solution, and dewatering with a dewatering agent to obtain the finished product m-aminobenzoic acid.
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Paragraph 0010; 0011; 0012; 0013; 0014; 0015

(2018/09/11)

A facile method for the synthesis of graphene-like 2D metal oxides and their excellent catalytic application in the hydrogenation of nitroarenes
Graphene-like two-dimensional (2D) metal oxides in the form of nanosheets (NSs) often exhibit superior performance in many applications in comparison with their bulk counterparts, owing to their unique electronic and physicochemical properties arising from their layered 2D structure; however, it is still a great challenge to produce 2D metal oxides in a facile way, especially for non-layered metal oxides. In the present work, a modified evaporation induced self-assembly (EISA) method was developed to synthesize graphene-like CeO2 nanosheets (NS-CeO2). Moreover, the EISA method is proved to be rather universal and a series of other single and mixed metal oxides, including TiO2, ZrO2, CoOx, NiO, Al2O3, CuO, CuO-ZrO2, MnOx-Al2O3, FeOx-CoOx, Cr2O3-ZnO, CeO2-ZrO2, CeO2-CuO, CeO2-CoOx, CeO2-La2O3, CeO2-FeOx, CeO2-MnOx, CeO2-ZnO, CeO2-Al2O3, CeO2-NiO, CeO2-Cr2O3, CeO2-TiO2, MnOx-CeO2-ZrO2, and CuO-CeO2-ZrO2, can be successfully prepared in the form of nanosheets with tunable pore structure and sheet thickness by using this method. The catalytic application of the graphene-like metal oxides was considered and the results illustrate that the CeO2 nanosheets decorated with Pd clusters (Pd/NS-CeO2) exhibit excellent catalytic performance in the hydrogenation of nitroarenes under mild conditions; over them, nitrobenzene can be completely converted to aniline even at room temperature in a short time. A series of characterization results combined with DFT calculations demonstrate that the CeO2 nanosheets are enriched with surface defects and Ce3+ species, which can promote the adsorption and activation of nitroarenes. The present work brings forward a facile and effective approach to synthesize graphene-like metal oxides with superior catalytic performance; besides, the results obtained in this work are also rather helpful to clarify the relationship between the 2D structure and performance of the Pd/NS-CeO2 catalyst in the hydrogenation of nitroarenes.
Lei, Lijun,Wu, Zhiwei,Liu, Huan,Qin, Zhangfeng,Chen, Chengmeng,Luo, Li,Wang, Guofu,Fan, Weibin,Wang, Jianguo
p. 9948 - 9961
(2018/06/06)

N-doped graphitic carbon-improved Co-MoO3 catalysts on ordered mesoporous SBA-15 for chemoselective reduction of nitroarenes
Metallic Co-MoO3 catalysts supported on ordered mesoporous SBA-15 were first prepared through in situ reaction of SBA-15-supported Co-Mo oxides with 1,10-phenanthroline. The resulting Co-MoO3/NC@SBA-15 catalysts with N-doped carbon (NC) exhibited high catalytic activity and chemoselectivity for selective reduction of various functionalized nitroarenes to the corresponding arylamines in ethanol with hydrazine hydrate at near room temperature (30 °C). For reduction of all tested substrates (28 examples), the catalyst could afford a conversion of >99% and arylamine selectivity of >99%. The excellent catalytic performance of the Co-MoO3/NC@SBA-15 was attributed to the Co-Nχ(C)-Mo active sites generated through the interaction between the surface Co-Nχ(C) and MoO3 species, promoting the dissociation of hydrazine molecule into the active H* species for the reduction of nitro groups. After the seventh cycle for reduction of 4-methoxylnitrobenzene, the 2%Co-MoO3/NC@SBA-15 showed little change in catalytic performance, textural properties, size and dispersion of metal species and valence states of elements, indicating high stability and recyclability.
Huang, Haigen,Liang, Xiangcheng,Wang, Xueguang,Sheng, Yao,Chen, Chenju,Zou, Xiujing,Lu, Xionggang
p. 127 - 137
(2018/05/04)

Method for preparing aminobenzoic acid or ester thereof
The invention discloses a method for preparing aminobenzoic acid or ester thereof. The method comprises the following steps: S1, sequentially adding nitrobenzoic acid or ester, a solvent and an active nickel catalyst in a reactor; S2, while stirring, introducing hydrogen gas to replace air in a system for 3-4 times, controlling the pressure of the hydrogen gas, and performing a stirring reaction at preset temperature for a scheduled time so as to realize catalytic hydrogenation; S3, performing filtration under reduced pressure, washing filter cakes with a solvent which is the same as the solvent in S1, and collecting the active nickel catalyst; S4, performing reduced-pressure concentration on filtrate obtained in the S3 to obtain a solid namely the product of the aminobenzoic acid or the ester thereof. The method disclosed by the invention can be performed in neutral condition, normal temperature, low pressure or normal pressure, is high in synthetizing yield and low in cost, and has commercial value and environmental protection efficacy; the yield of the obtained product can be 95% or above, and the purity of the product can be 98.5% or above.
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Paragraph 0019

(2017/07/21)

Highly chemoselective reduction of nitroarenes over non-noble metal nickel-molybdenum oxide catalysts
The chemoselective reduction of nitroarenes is an important transformation for the production of arylamines, which are the primary intermediates in the synthesis of pharmaceuticals, agrochemicals and dyes. Heterogeneous non-noble metal nickel-molybdenum oxide catalysts supported on ordered mesoporous silica SBA-15 (Ni-MoO3/CN@SBA-15) were prepared for the first time by treating SBA-15-supported nickel-molybdenum oxide materials with 1,10-phenanthroline, and exhibited unprecedented catalytic activity and chemoselectivity for the reduction of various substituted nitroarenes to the corresponding aromatic amines in ethanol with hydrazine hydrate as a hydrogen donor under mild conditions owing to the synergistic effect of metal Ni and MoO3 species, affording excellent yields of >99% within very short reaction periods (≤60 min). The Ni-MoO3/CN@SBA-15 catalysts were highly stable and could easily be recovered by simple filtration or by an external magnetic field for at least ten recycling reactions without any observable loss of catalytic performance or leaching of metal components.
Huang, Haigen,Wang, Xueguang,Li, Xu,Chen, Chenju,Zou, Xiujing,Ding, Weizhong,Lu, Xionggang
p. 809 - 815
(2017/08/15)

High Performance and Active Sites of a Ceria-Supported Palladium Catalyst for Solvent-Free Chemoselective Hydrogenation of Nitroarenes
Cerium oxide-supported palladium catalysts (Pd/CeO2) prepared by a simple impregnation method exhibit exciting catalytic activity and high chemoselectivity for the solvent-free hydrogenation of a variety of substituted nitroarenes including the reducible functional groups to the corresponding aromatic amines under mild reaction conditions. Taking nitrobenzene as an example, the Pd/CeO2 catalyst can afford aniline yields of >99 % with turnover frequencies as high as 11 411 h?1 and 69 824 h?1 at 40 °C and 100 °C, respectively. Pd2+ ion species exist as isolated single atoms with ?Pd2+?O2??Ce4+? linkages on the surface of PdxCe1?xO2?σ solid solution and are found to be active sites for the selective hydrogenation of nitroarenes in the absence of solvent. The superior catalytic performance can be attributed to the cooperative effect between Pd2+ ions and unique surface sites of CeO2. A possible mechanism is proposed for the hydrogenation of nitroarenes with H2 over the Pd/CeO2. The Pd/CeO2 catalyst can be recovered easily and reused for at least seven recycling reactions without loss of catalytic properties.
Shi, Xiuxiu,Wang, Xueguang,Shang, Xingfu,Zou, Xiujing,Ding, Weizhong,Lu, Xionggang
p. 3743 - 3751
(2017/10/16)

Bimetallic Platinum-Tin Nanoparticles on Hydrogenated Molybdenum Oxide for the Selective Hydrogenation of Functionalized Nitroarenes
The hydrogenation of functionalized nitroarenes to the corresponding anilines is of great importance in the fine chemical industry and requires high-performance catalysts with a good activity and selectivity. Herein, hydrogenated MoOx (H-MoOx) supported bimetallic Pt-Sn (Pt-Sn/H-MoOx) was developed to accomplish selective and efficient hydrogenation. In the case of 4-nitrostyrene, an outstanding selectivity to 4-vinylaniline (≈93 %) with a high turnover frequency (0.094 s?1) was achieved under mild conditions (T=30 °C, PH2 =1 atm). The metal–support interactions contributed to the efficient turnover on the ultrafine nanoparticles, and the atom-rearranged bimetallic Pt-Sn surface promoted the selectivity because of the preferred adsorption of the nitro group. The good efficiency for various functionalized nitroarenes further verified the promise of Pt-Sn/H-MoOx in chemoselective hydrogenation.
Shu, Yijin,Chan, Hang Cheong,Xie, Lifang,Shi, Zhangping,Tang, Yi,Gao, Qingsheng
p. 4199 - 4205
(2017/10/20)

Insight into the mechanism of gold-catalyzed reduction of nitroarenes based on the substituent effect and: In situ IR
A study is presented here on the mechanistic pathway of catalytic reduction of nitroarenes with diverse substituent groups in the presence of ultra-small gold nanoparticles and NaBH4. The kinetic data based on the substituent effect and the Hammett plot, together with analyses of intermediates, revealed that this reaction followed a direct route and that all of the reaction steps were rapid without accumulation of intermediates. In particular, in situ IR was found to be an effective method for the real-time monitoring of this model reduction in our catalytic system and confirmed the presence of a hydroxylamine intermediate. These results will provide a new insight into the mechanism of gold-catalyzed reduction of nitroarenes and offer a reference for future mechanism tests of heterogeneous nanocatalysis.
Wang, Cui,Zou, Wei,Wang, Jiasheng,Ge, Yuzhen,Lu, Rongwen,Zhang, Shufen
p. 3865 - 3871
(2017/07/12)

Generation of Cu nanoparticles on novel designed Fe3O4@SiO2/EP.EN.EG as reusable nanocatalyst for the reduction of nitro compounds
In this work, copper nanoparticles loaded on Fe3O4@SiO2, which we have named Fe3O4@SiO2/EP.EN.EG@Cu for short, have been designed, prepared and characterized by XRD, FTIR, TEM, SEM, EDS, TGA, ICP, successfully. The catalytic performance was investigated in the reduction of aromatic nitro compounds in the presence of NaBH4 aqueous solution as the source of hydrogen at 50°C. The Fe3O4@SiO2/EP.EN.EG@Cu catalyst was readily removed from the reaction mixture by applying an external magnet and reused for five times without significant loss of catalytic activity.
Rajabzadeh, Maryam,Eshghi, Hossein,Khalifeh, Reza,Bakavoli, Mehdi
p. 19331 - 19340
(2016/03/01)

Carbon nitride supported palladium nanoparticles: An active system for the reduction of aromatic nitro-compounds
Synthesis of carbon nitride supported highly dispersed ultrafine palladium nanoparticles has been reported for the reduction of aromatic nitro-compounds using hydrazine hydrate as a reducing agent. As a demonstration, the as-synthesized carbon nitride-palladium composite was shown to be a highly active and chemo-selective for the title reaction. Utilizing the optimized reaction conditions a set of aromatic nitro compounds have been converted to their corresponding amine derivatives with good to excellent yield ranging from 80% to 99%. The catalyst can be used for multiple times without affecting the catalytic performance and can also be stored for a long time at ambient condition maintaining the high catalytic efficiency.
Nandi, Debkumar,Siwal, Samarjeet,Choudhary, Meenakshi,Mallick, Kaushik
p. 31 - 38
(2016/06/09)

Solvent-Free Selective Hydrogenation of Nitroarenes Using Nanoclusters of Palladium Supported on Nitrogen-Doped Ordered Mesoporous Carbon
The selective hydrogenation of nitroarenes is a key transformation for the production of aromatic amines, which are primary intermediates in the synthesis of pharmaceuticals, agrochemicals, and dyes. However, most reaction processes require toxic organic solvents and suffer from poor selectivity in the presence of other reducible groups. Herein, we report a successful example of nanoclusters of ultrafine Pd supported on N-modified ordered mesoporous CMK-3 carbon (Pd/N-CMK-3) prepared by a facile two-step impregnation route with aqueous solutions of 1,10-phenanthroline and H2PdCl4 that hydrogenated various nitroarenes highly efficiently and selectively to the corresponding aromatic amines with hydrogen in the absence of solvent. The Pd/N-CMK-3 catalyst could be recovered easily for multiple recycling reactions without a loss of catalytic performance.
Huang, Haigen,Wang, Xueguang,Tan, Mingwu,Chen, Chenju,Zou, Xiujing,Ding, Weizhong,Lu, Xionggang
p. 1485 - 1489
(2016/05/02)

Effective Hydrogenation of Haloaromatic Nitro Compounds Catalysed by Iridium Nanoparticles Deposited on Multiwall Carbon Nanotubes
Iridium nanoparticles immobilized on multiwall carbon nanotubes composites were synthesized using anhydrous iridium trichloride as a precursor. The as-prepared composites were applied as catalysts for the hydrogenation of haloaromatic nitro compounds at room temperature and balloon hydrogen pressure in a methanol/water mixture, showing a selectivity of 99.9% to p-chloroaniline at complete conversion of p-chloronitrobenzene. Moreover, the catalysts also exhibited excellent catalytic properties for the reactants with electron-accepting, electron-donating, and heterocycle groups. The high activity and selectivity of the catalyst was probably attributed to the interaction such as competitive adsorption and hydrogen bonding between solvent water and reactants.
Li, Hua-Bin,Liu, Lu,Ma, Xiao-Yan
p. 1499 - 1505
(2016/06/09)

A normal pressure catalytic synthesis of aniline compounds and the use of catalyst (by machine translation)
A normal pressure catalytic synthesis of aniline compounds is the nitrobenzene compound and solvent after mixing, adding catalyst to form suspension, then transfer to the with a quartz window in the high-pressure reactor, reactor for sealing and hydrogen purge after washing, maintaining a hydrogen under normal pressure conditions, under stirring condition, heating the reaction system to10-50oC, in strength is0.01-5W/cm2under the illumination of the reaction, the reaction time is 5 - 180min. This invention has mild condition, environmental protection, low cost, simple operation, reaction period is short, high product yield, selectivity is good. (by machine translation)
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Paragraph 0059-0062

(2017/04/14)

Purification, characterization and in-silico analysis of nitrilase from Gordonia terrae
An inducible and aromatic nitrilase from Gordonia terrae was purified with a yield of 19%. The enzyme had turnover number of 63 s-1 × 10-3, Km1.4 mM and Vmax95 Umg-1 protein for benzonitrile. The nitrilase of G. terrae was active at basic pH (7-10), moderate temperature (20-45 °C) and has a half-life of 4 h at 35 °C. MALDI analysis and amino acid sequence deduced from cloned nucleotide fragment showed 97% homology with putative amidohydrolase of Gordonia sputi NBRC 100414 and G. namibiensis. The enzyme showed regioselectivity towards hydroxybenzonitriles, as different position of hydroxyl group i.e. meta-, para- and orthosubstitutions on benzonitrile effect enzyme activity. The in-silico interactions of these substrates with the predicted 3D model of this enzyme also showed differential interaction between hydroxyl group of substrates and the polar amino acids surrounding enzyme's active site. This leads to different proximity and orientation of substrates vis-a-vis their interaction with catalytic residues.
Kumar, Vijay,Seth, Amit,Kumari, Vijaya,Kumar, Virender,Bhalla, Tek C.
p. 52 - 62
(2015/04/14)

Selective reduction of nitro-compounds to primary amines by nickel-catalyzed hydrosilylative reduction
Ni(acac)2 and PMHS were found to be an excellent catalytic system for the chemoselective transfer hydrogenation of nitro-compounds to primary amines. Under mild conditions a series of nitro-compounds containing a variety of sensitive functional groups including aldehydes, esters, cyano, and nitrine were reduced to their corresponding amines in good to excellent yields with no byproduct.
Sun, Shuai,Quan, Zhengjun,Wang, Xicun
p. 84574 - 84577
(2015/10/28)

Metal-Free Reduction of Aromatic and Aliphatic Nitro Compounds to Amines: A HSiCl3-Mediated Reaction of Wide General Applicability
A new, mild, metal-free, HSiCl3-mediated reduction of both aromatic and aliphatic nitro groups to amines that is of wide general applicability, tolerant of many functional groups, and respectful of the stereochemical integrity of stereocenters is reported.
Orlandi,Tosi,Bonsignore,Benaglia
supporting information
p. 3941 - 3943
(2015/09/01)

Palladium modified magnetic mesoporous carbon derived from metal-organic frameworks as a highly efficient and recyclable catalyst for hydrogenation of nitroarenes
We present a facile route for the fabrication of palladium modified magnetic nanoparticles (Fe@Pd NPs) embedded in mesoporous carbon (MC), derived from metal-organic frameworks, to produce the Fe@Pd-MC nanocatalyst. The Fe@Pd-MC nanocatalyst exhibited excellent catalytic activity toward the hydrogenation of nitroarenes as well as easy recovery and reusability.
Dong, Zhengping,Liang, Kun,Dong, Chunxu,Li, Xinlin,Le, Xuanduong,Ma, Jiantai
p. 20987 - 20991
(2015/03/30)

Palladium supported on hollow magnetic mesoporous spheres: A recoverable catalyst for hydrogenation and Suzuki reaction
A high-performance palladium catalyst was developed by the covalent binding of a Schiff base ligand, N,N′-bis(3-salicylidenaminopropyl)amine (salpr), on the surface of hollow magnetic mesoporous spheres (HMMS) followed by immobilization with Pd(0). The catalyst was characterized by TEM, EDX, FT-IR, XRD, VSM, TGA and N2 adsorption-desorption. The novel catalyst exhibited high activity in hydrogenation and Suzuki coupling reaction. Furthermore, it could be recovered from the reaction mixture in a facile manner and recycled six times without any loss of activity.
Liu, Hengzhi,Wang, Peng,Yang, Honglei,Niu, Jianrui,Ma, Jiantai
p. 4343 - 4350
(2015/06/16)

Mechanism-Based Trapping of the Quinonoid Intermediate by Using the K276R Mutant of PLP-Dependent 3-Aminobenzoate Synthase PctV in the Biosynthesis of Pactamycin
Mutational analysis of the pyridoxal 5′-phosphate (PLP)-dependent enzyme PctV was carried out to elucidate the multi-step reaction mechanism for the formation of 3-aminobenzoate (3-ABA) from 3-dehydroshikimate (3-DSA). Introduction of mutation K276R led to the accumulation of a quinonoid intermediate with an absorption maximum at 580 nm after the reaction of pyridoxamine 5′-phosphate (PMP) with 3-DSA. The chemical structure of this intermediate was supported by X-ray crystallographic analysis of the complex formed between the K276R mutant and the quinonoid intermediate. These results clearly show that a quinonoid intermediate is involved in the formation of 3-ABA. They also indicate that Lys276 (in the active site of PctV) plays multiple roles, including acid/base catalysis during the dehydration reaction of the quinonoid intermediate.
Hirayama, Akane,Miyanaga, Akimasa,Kudo, Fumitaka,Eguchi, Tadashi
p. 2484 - 2490
(2016/01/26)

MgI2-Mediated Chemoselective Cleavage of Protecting Groups: An Alternative to Conventional Deprotection Methodologies
The scope of MgI2 as a valuable tool for quantitative and mild chemoselective cleavage of protecting groups is described here. This novel synthetic approach expands the use of protecting groups, widens the concept of orthogonality in synthetic processes, and offers a facile opportunity to release compounds from solid supports. Amazing MgI2: Protecting groups have had a tremendous positive impact on the art of biomolecule synthesis. In a context in which the use of attractive protecting groups is often limited by harsh deprotection conditions and low chemoselective flexibility, MgI2 offers, by the execution of a very simple protocol, a fresh vision with extensive perspectives.
Berthet, Mathéo,Davanier, Florian,Dujardin, Gilles,Martinez, Jean,Parrot, Isabelle
supporting information
p. 11014 - 11016
(2015/11/10)

Chemoselective reduction of nitrobenzenes having other reducible groups over titanium(IV) oxide photocatalyst under protection-, gas-, and metal-free conditions
m-Nitrostyrene was chemoselectively reduced to m-aminostyrene in an acetonitrile suspension containing a titanium(IV) oxide (TiO2) photocatalyst and a suitable hole scavenger at room temperature under atmospheric pressure without the use of a precious metal or reducing gas. Addition of a small amount of water to acetonitrile increased the reaction rate, and the highest rate was obtained. Moreover, applicability of the photocatalytic system was investigated using various nitro compounds having other reducible groups (chloro, bromo, carboxyl, and acetyl groups), and only the nitro group of these compounds was chemoselectively reduced, resulting in the formation of corresponding amino compounds with high yields.
Imamura, Kazuya,Nakanishi, Kousuke,Hashimoto, Keiji,Kominami, Hiroshi
p. 6134 - 6139
(2015/03/30)

Active Pd/Fe(OH)x catalyst preparation for nitrobenzene hydrogenation by tracing aqueous phase chlorine concentrations in the washing step of catalyst precursors
By tracing the chlorine concentrations in the aqueous solutions containing the catalyst precursors, Pd/Fe(OH)x catalysts with different activities can be controllably prepared. For the hydrogenation of nitrobenzene, the active Pd/Fe(OH)x catalysts were obtained from aqueous solutions with chlorine concentrations below 18 ppm and above 8 ppm.
Zhang, Chengming,Cui, Xinjiang,Deng, Youquan,Shi, Feng
p. 6050 - 6054
(2015/03/30)

Electrophilicity and nucleophilicity of commonly used aldehydes
The present approach for determining the electrophilicity (E) and nucleophilicity (N) of aldehydes includes a kinetic study of KMNO4 oxidation and NaBH4 reduction of aldehydes. A transition state analysis of the KMNO4 promoted aldehyde oxidation reaction has been performed, which shows a very good correlation with experimental results. The validity of the experimental method has been tested using the experimental activation parameters of the two reactions. The utility of the present approach is further demonstrated by the theoretical versus experimental relationship, which provides easy access to E and N values for various aldehydes and offers an at-a-glance assessment of the chemical reactivity of aldehydes in various reactions. the Partner Organisations 2014.
Pratihar, Sanjay
p. 5781 - 5788
(2014/07/22)

Reduction of organic azides to amines using reusable Fe3O 4 nanoparticles in aqueous medium
Aromatic, heteroaromatic and sulfonyl azides were conveniently reduced to the corresponding amines in excellent yields using hydrazine hydrate in the presence of iron oxide nanoparticles. The Fe3O4-MNPs could be easily separated by an external magnet, and recycled ten times without significant loss of the catalytic efficiency. The Royal Society of Chemistry 2013.
Pagoti, Sreenivasarao,Surana, Subham,Chauhan, Ajay,Parasar, Bibudha,Dash, Jyotirmayee
p. 584 - 588
(2013/03/28)

Chemoselective reduction of nitrobenzenes to aminobenzenes having reducible groups by a titanium(iv) oxide photocatalyst under gas- and metal-free conditions
m-Nitrovinylbenzene was chemoselectively reduced to m-aminovinylbenzene in a suspension of a TiO2 photocatalyst in the presence of a hole scavenger at room temperature under atmospheric pressure without the use of a precious metal or reducing gas, and nitrobenzenes having other reducible groups were also chemoselectively reduced to corresponding aminobenzenes. The Royal Society of Chemistry 2012.
Imamura, Kazuya,Hashimoto, Keiji,Kominami, Hiroshi
supporting information; experimental part
p. 4356 - 4358
(2012/06/04)

Rapid hydrogenation of aromatic nitro compounds in supercritical carbon dioxide: Mechanistic implications via experimental and theoretical investigations
An exceptionally rapid hydrogenation of nitrobenzene to aniline [TOF=252,000 h-1] over palladium containing MCM-41 (Pd/MCM-41) with excellent yield of >99% can be achieved in supercritical carbon dioxide at 50 °C and a hydrogen pressure of 2.5 MPa. It has been observed that this promising method preferred a single phase between liquid substrate and carbon dioxide-hydrogen system. The ascendancy of the supercritical carbon dioxide medium is established in comparison with the conventional organic solvent and solvent-less conditions. Changes in the reaction parameters such as carbon dioxide and hydrogen pressure, temperature and the reaction time do not affect the selectivity. A combined experimental and theoretical study has elucidated the mechanism under the studied reaction condition because experimental observations revealed a direct conversion of nitrobenzene to aniline. However, density functional theory (DFT) calculation shows that the direct conversion is energetically unfavourable; hence, a stepwise mechanism has been proposed. Theoretical predictions and experimental observations suggested that the rate-limiting step of nitrobenzene conversion is different from that of the liquid phase hydrogenation. This catalytic process can also be successfully extended to the hydrogenation of other aromatic nitro compounds with different substituents. Easy separation of the liquid product from catalyst and the use of an environmentally friendly solvent make this procedure a viable and an attractive green chemical process. Copyright
Chatterjee, Maya,Chatterjee, Abhijit,Kawanami, Hajime,Ishizaka, Takayuki,Suzuki, Toshishige,Suzuki, Akira
experimental part
p. 2009 - 2018
(2012/09/22)

Synthesis and characterisation of a polymer-bound rhodium-benzimidazole complex as catalyst for the hydrogenation of nitroarenes
A polymer-anchored rhodium complex was synthesised by sequential attachment of benzimidazole (BzlH) and RhCl3 to chloromethylated poly(styrene-divinylbenzene) co-polymer (PSDVB) with 6.5% cross-linking. The catalyst was characterised by X-ray photoelectron spectroscopy, far-IR, UV-Vis, FTIR, SEM and thermogravimetric analysis. Various physico-chemical properties such as bulk density, surface area and swelling behaviour in different solvents were also studied. The polymer-anchored complex was tested as a catalyst for reduction of nitroarenes, namely o,m,p-nitrobenzoic acid, nitroaniline, nitrophenol and nitrotoluene. Kinetic measurements were carried for o-nitroaniline and p-nitrophenol by varying temperature, catalyst concentration and concentration of substrates. The rate of the reaction was found to be first order with respect to catalyst concentration and also with substrate concentration at low concentrations, becoming independent of substrate at higher concentrations. A plausible mechanism for the reaction is proposed. The energy and entropy of activation calculated from Arrhenius plots indicate high activity of the catalystonthe support.Therecycling efficiencyof the catalyst has been studied and there was no leaching of metal from the catalyst surface. Springer Science+Business Media B.V. 2011.
Alexander,Udayakumar,Gayathri
experimental part
p. 1 - 6
(2012/10/07)

Remarkable effect of PEG-1000-based dicationic ionic liquid for N-Hydroxyphthalimide-catalyzed aerobic selective oxidation of alkylaromatics
PEG 1000-based functional dicationic acidic ionic liquid (PEG 1000-DAIL) was used for the first time as the reaction solvent for the N-Hydroxyphthalimide (NHPI)-cobalt acetate(Co(OAc)2) catalyzed aerobic oxidations of alkylaromatics to the corresponding acids. It enhanced the efficient catalytic ability of NHPI: 99.9 % conversion of toluene with 99.5 % selectivity for benzoic acid could be obtained at 80 °C in 10 h and ethylbenzene was selectively oxidized to benzoic acid. Several alkylaromatics were efficiently oxidized to their corresponding acids under mild conditions. For substituted toluene, the conversions of substrates and the selectivity of products was affected by the position and kind of substituted groups, respectively. Both the catalyst and PEG1000-DAIL could be reused at least eight times without significantly decreasing the catalytic activity.
Lu, Tingting,Lu, Ming,Yu, Wang,Liu, Zhongjie
p. 277 - 282
(2013/01/15)

Method for estimating SN1 rate constants: Solvolytic reactivity of benzoates
Nucleofugalities of pentafluorobenzoate (PFB) and 2,4,6-trifluorobenzoate (TFB) leaving groups have been derived from the solvolysis rate constants of X,Y-substituted benzhydryl PFBs and TFBs measured in a series of aqueous solvents, by applying the LFER equation: log k = sf(Ef + Nf). The heterolysis rate constants of dianisylmethyl PFB and TFB, and those determined for 10 more dianisylmethyl benzoates in aqueous ethanol, constitute a set of reference benzoates whose experimental ΔG ? have been correlated with the ΔH? (calculated by PCM quantum-chemical method) of the model epoxy ring formation. Because of the excellent correlation (r = 0.997), the method for calculating the nucleofugalities of substituted benzoate LGs have been established, ultimately providing a method for determination of the SN1 reactivity for any benzoate in a given solvent. Using the ΔG? vs ΔH? correlation, and taking sf based on similarity, the nucleofugality parameters for about 70 benzoates have been determined in 90%, 80%, and 70% aqueous ethanol. The calculated intrinsic barriers for substituted benzoate leaving groups show that substrates producing more stabilized LGs proceed over lower intrinsic barriers. Substituents on the phenyl ring affect the solvolysis rate of benzhydryl benzoates by both field and inductive effects.
Matic, Mirela,Denegri, Bernard,Kronja, Olga
supporting information
p. 8986 - 8998,13
(2012/12/12)

Copper(I)-catalyzed amination of aryl halides in liquid ammonia
The amination of aryl halides in liquid ammonia (LNH3) is catalyzed by a copper(I) salt/ascorbate system to yield primary aromatic amines in good to excellent yields. The low concentrations of catalyst required and the ease of product isolation suggest that this process has potential industrial applications. Commonly used ligands for analogous metal-catalyzed reactions are not effective. The rate of amination of iodobenzene in liquid ammonia is first order in copper(I) catalyst concentration. The small Hammett I? = 0.49 for the amination of 4-substituted iodobenzenes in liquid ammonia at 25 °C indicates that the C-I bond is not significantly broken in the transition state structure and that there is a small generation of negative charge in the aryl ring, which is compatible with the oxidative addition of the copper ion being rate limiting.
Ji, Pengju,Atherton, John H.,Page, Michael I.
p. 7471 - 7478
(2012/11/06)

Thermodynamics of phenylacetamides synthesis: Linear free energy relationship with the pK of amine
The effective equilibrium constants K′C expressed through the total concentrations of the reagents for the synthesis of N-phenylacetyl-derivatives in aqueous medium from phenylacetic acid and various primary amino compounds have been determined with penicillin acylase as a catalyst. Broad specificity of penicillin acylase (EC 3.5.1.11) to amino components made possible to investigate the acylation of primary amines with different structures and physicochemical properties. Analysis of different components of the effective standard Gibbs energy change ΔGC o′ has revealed favorable thermodynamics for the synthesis of phenylacetamides from unionized substrates forms, however the ionization of reactants carboxy and amino groups in aqueous solutions pushes the equilibrium position to the hydrolysis especially in case of highly basic amines. A linear correlation between the standard Gibbs energy change for amide bond formation from the unionized reagents species and the basicity of amino group was observed: ΔGTo=-3.56pKamine+7.71(kJ/mol). The established linear free energy relationship (LFER) allows to predict the thermodynamic parameters for direct condensation of phenylacetic acid with any amine of known pK. Condensation of phenylacetic acid and amines with pK value within 1.5-8.5 was shown to be thermodynamically favorable in homogeneous aqueous solution. .
Guranda, Dorel T.,Ushakov, Gennadij A.,Yolkin, Petr G.,Svedas, Vytas K.
experimental part
p. 48 - 53
(2012/05/19)

Exploring the effect of supramolecular structures of micelles and cyclodextrins on fluorescence emission of local anesthetics
Benzocaine (ethyl 4-aminobenzoate, 4) and its derivatives ethyl 2-aminobenzoate, 2, and ethyl 3-aminobenzoate, 3, were found to form association complexes with supramolecular structures of micelles and cyclodextrins (CDs). The fluorescence emission of 2, 3 or 4 dissolved in the pseudo-micellar phase or included into α-, β-, or γ-CD cavity increases dramatically with respect to that observed in only water. High percentages of organic solvents like dioxane, acetonitrile, DMSO in the aqueous solution lead to a similar effect. The stability constants of the complexes formed between these drugs and cyclodextrins have been determined. In neutral or acid medium, a 1:1 stoichiometry for drug: CD complexes have been found, whereas in alkaline medium 1:2 stoichiometry was also detected in some cases. Kinetic studies of both the nitrosation of the amine group and the alkaline hydrolysis of the ester function was employed to infer the conformation of the complexes as well as to evaluate their stability constants. Theoretical calculations to optimize the molecular structure of 2, 3 and 4 allow us to propose possible geometries of the complexes that are in agreement with the experimental data. The Royal Society of Chemistry and Owner Societies 2011.
Iglesias, Emilia
experimental part
p. 531 - 542
(2012/03/13)

Synthesis, characterisation of polymer-supported palladium-2- methylimidazole complex catalyst for the hydrogenation of aromatic nitro compounds
A polymer-supported palladium-2-methylimidazole complex was synthesised and characterised by various physicochemical methods. The complex was successfully used as a catalyst for the hydrogenation of nitrobenzene and a few of its derivatives under ambient conditions. Results reveal that the electronic as well as the steric effects of the substitutent control the rate of hydrogenation of the nitro group in the studied nitro compounds. The kinetics of hydrogenation and the reusability of the catalyst were also studied.
Velua, Udayakumar,Stanislaus, Alexander,Virupaiah, Gayathri,Shivakumaraiah,Patil, Kashinath Rangu,Balasubramanian, Viswanathan
experimental part
p. 112 - 115
(2011/06/27)

Synthesis and characterization of ruthenium(III) chloride complexes with some 1,2-disubstituted benzimidazoles and their catalytic activity
Reaction of ruthenium(III) chloride with 2-mono substituted and 1,2-disubstituted benzimidazoles yield the complexes of the formulae RuCl 3Ly.nH2O [L = 2-o-hydroxyphenylbenzimidazole (oHPB), y = 3, n = 0; L = 2-p-hydroxyphenylbenzimidazole (pHPB), y = 2, n = 3], and RuCl3L2.H2O [L = 1-o-hydroxybenzyl-2-o-hydroxyphenylbenzimidazole (oHBPB), 1-m-hydroxybenzyl-2-m-hydroxyphenylbenzimidazole (mHBPB), and 1-p-hydroxybenzyl-2-p-hydroxyphenylbenzimidazole (pHBPB)]. The complexes are characterized by elemental analysis, conductivity measurements, infrared, electronic, 1H- and 13C-NMR spectral studies, as well as by thermal analysis. The complexes exhibit octahedral geometry. Some of the complexes act as potential catalyst towards transferhydrogenation. Copyright Taylor & Francis Group, LLC.
Krishnamurthy
scheme or table
p. 590 - 597
(2011/10/03)

Synthesis and hydrolytic evaluation of acid-labile imine-linked cytotoxic isatin model systems
In this study a series of isatin-based, pH-sensitive aryl imine derivatives with differing aromatic substituents and substitution patterns were synthesised and their acid-catalysed hydrolysis evaluated. These derivatives were functionalised at the C3 carbonyl group of a potent N-substituted isatin cytotoxin and were stable at physiological pH but readily cleaved at pH 4.5. Observed rates of hydrolysis for the embedded imine-acid moiety were in the order para-phenylpropionic acid > phenylacetic acid (para > meta) > benzoic acid (meta > para). The ability to fine-tune hydrolysis rates in this way has potential implications for optimising imine linked, tumour targeting cytotoxin-protein conjugates.
Matesic, Lidia,Locke, Julie M.,Vine, Kara L.,Ranson, Marie,Bremner, John B.,Skropeta, Danielle
experimental part
p. 1771 - 1778
(2011/04/17)

Hydrogenation of substituted nitroarenes by a polymer-bound palladium(II) Schiff base catalyst
The catalytic activity of a polymer-bound palladium Schiff base catalyst was investigated toward the reduction of aryl nitro compounds under ambient temperature and pressure. The dependence of the rate of hydro- genation of o-nitroaniline and o-nitrotoluene on substrate concentration, catalyst concentration and temperature has been determined. Based on the results obtained a plausible mechanism for the hydrogenation reaction is proposed and a rate expression is deduced. The energy and entropy of activation have been evaluated from the kinetic data. The polymer-bound catalyst was found to be better than its homogeneous analog PdCl2(NSBA) [NSBA = N-salicy- lidene benzylamine] for both stability and reusability. Recycling studies revealed that the catalyst could be used six times without metal leaching or significant loss in activity. Springer Science+Business Media B.V. 2009.
Alexander,Udayakumar,Nagaraju,Gayathri
experimental part
p. 247 - 251
(2011/10/09)

Optimization of the azobenzene scaffold for reductive cleavage by dithionite; development of an azobenzene cleavable linker for proteomic applications
In this paper we conducted an extensive reactivity study to determine the key structural features that favour the dithionite-triggered reductive cleavage of the azo-arene group. Our stepwise investigation allowed identification of a highly reactive azo-arene structure 25 bearing a carboxylic acid, at the ortho position of the electron-poor arene and an ortho-Oalkyl-resorcinol as the electron-rich arene. Based on this 2(2′-alkoxy-4′-hydroxyphenylazo) benzoic acid (HAZA) scaffold, the orthogonally protected difunctional azo-arene cleavable linker 26 was designed and synthesized. Selective linker deprotection and derivatization was performed by introducing an alkyne reactive group and a biotin affinity tag. This optimized azo-arene cleavable linker led to a total cleavage in less than 10 s with only 1 mM dithionite. Similar results were obtained in biological media.
Leriche, Geoffray,Budin, Ghyslain,Brino, Laurent,Wagner, Alain
experimental part
p. 4360 - 4364
(2010/09/20)