cas 554-00-7, 2,4-Dichloroaniline | Articles data

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Efficient and recyclable bimetallic Co–Cu catalysts for selective hydrogenation of halogenated nitroarenes
Silica supported N-doped carbon layers encapsulating Co–Cu nanoparticles (Co1Cux@CN/SiO2) were prepared by a one-step impregnation of Co(NO3)2·6H2O, Cu(NO3)2·3H2O, urea and glucose, following in situ carbothermal reduction. Effects of Cu contents on the catalytic performance of the Co1Cux@CN/SiO2 catalysts were investigated for selective hydrogenation of p-chloronitrobenzene to p-chloroaniline. The Co1Cu0.30@CN/SiO2 with Cu/Co molar ratio of 0.30:1 presented much higher activity and stability than the monometallic Co@CN/SiO2 catalyst. The addition of Cu into Co1Cux@CN/SiO2 catalysts had favorable effects on the formation of highly active Co–N sites and N-doped carbon layer. The role of the N-doped carbon layer was to protect the Co from oxidation by air, and the Co1Cu0.30@CN/SiO2 could be reused for at least 12 cycles without decrease in catalytic efficiency. Mechanistic and in situ infrared studies revealed that the interaction effect between the Co and Cu atoms made the surface of Co highly electron rich, which decreased adsorption of halogen groups and resulting in the enhanced selectivity during chemoselective hydrogenation of halogenated nitroarenes for a wide scope of substrates.
Lu, Xionggang,Ren, Jiaan,Sheng, Yao,Wang, Xueguang,Wu, Baoqin,Zou, Xiujing
(2021/12/20)

A convenient Hofmann reaction of carboxamides and cyclic imides mediated by trihaloisocyanuric acids
A simple, efficient and pot-economic approach in a single vessel has been developed for conversion of aromatic and aliphatic carboxamides into primary amines with one fewer carbom atom (Hofmann reaction) in 38–89 % yield by reacting with trichloro- or tribromoisocyanuric acid and sodium hydroxide in aqueous acetonitrile. Under the same reaction conditions, cyclic imides gave amino acids (69–83 %). The role of the trihaloisocyanuric acids is the in situ generation of N-haloamides, key-intermediates for the Hofmann reaction. The scalability of the methodology was demonstrated by a multigram-scale transformation of phthalimide into anthranilic acid in 77 % yield.
Bastos, Gustavo A.,de Mattos, Marcio C.S.
(2021/09/29)

Method for preparing dichloroaniline through chlorination
The invention relates to a method for preparing dichloroaniline by chlorination. The method comprises the following steps: adding o-chloroaniline into a solvent, and carrying out chlorination reactionat 0-80 DEG C for 2-12 hours; neutralizing the reaction solution with alkali until the pH value is 9-10, and separating the organic phase from the water phase to obtain an organic phase; and carryingout rectification separation on the organic phase to respectively obtain pure products 2,4-dichloroaniline and 2,6-dichloroaniline. According to the invention, the main raw material o-chloroaniline is easy to obtain and low in price, so that the method has relatively high economical efficiency; the method has the advantages of no need of special reagents or solvents, one-step chlorination reaction, mild reaction conditions, simple operation, less wastewater, simple treatment and environmental friendliness, and only generates a small amount of salt-containing wastewater in the neutralization step; and the total yield is greater than 90%, and the purity can reach 99.5% or above, which is higher than the purity of 99% of the product in the prior art.
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Paragraph 0027-0040

(2021/02/13)

A Pd confined hierarchically conjugated covalent organic polymer for hydrogenation of nitroaromatics: Catalysis, kinetics, thermodynamics and mechanism
Herein, we propose a fast and scalable synthesis of a triazine based hierarchically conjugated covalent organic polymer under solvent and additive free conditions through a single step process. The synthesized material CCTP (Cyanuric Chloride-Thiourea-Polymer) was thoroughly characterized by various physicochemical techniques. The CCTP exhibited regular sponginess and excellent chemical as well as thermal stability. The solvent and additive free approach for CCTP synthesis provides a sustainable alternative for classical solvothermal methods. The CCTP was immobilized with Pd (0) and subsequently a heterogeneous material Pd&at;CCTP was obtained, which was used as an efficient catalyst for the hydrogenation of nitroarenes. The rate constant and Ea were measured to be 2.08 × 10-2 s-1 and 15.67 kJ mol-1 respectively and thereafter other thermodynamic parameters like ΔH, ΔS and ΔG for the hydrogenation of p-nitrophenol were also calculated. The obtained results indicate that the catalytic hydrogenation of p-nitrophenol is a non-spontaneous and endothermic process. We have also investigated the effect of surfactants (NH4OH, FA, and N2) on the reaction performance, and consequently NH4OH and FA both slow down the reaction while N2 doesn't affect the reaction medium. Further, we calculated the rate constant for the hydrogenation of 2,4-dinitrophenol and 2,4,6-trinitrophenol. An array of nitroarenes were further reduced to extend the substrate scope at RT; high TOFs were observed. Besides, Pd&at;CCTP showed excellent reusability in hydrogenation reactions without evident performance falloff.
Awasthi, Satish Kumar,Yadav, Deepika
p. 4295 - 4303
(2020/07/30)

In Situ Synthesized Silica-Supported Co@N-Doped Carbon as Highly Efficient and Reusable Catalysts for Selective Reduction of Halogenated Nitroaromatics
Silica-supported Co@N-doped carbon (Co@CN/SiO2) catalysts were first prepared by a one-step impregnation with a mixed solution of cobalt nitrate, glucose and urea, followed by in situ carbonization and reduction. The Co@CN/SiO2 catalysts were investigated for the selective reduction of nitro aromatics to the corresponding anilines using hydrazine hydrate. The Co@CN/SiO2-500 carbonized at 500 °C exhibited the highest catalytic activity and excellent stability without any decay of activity after 6 cycles for the reduction of nitrobenzene. Both metallic Co atoms and Co?N species formed in the Co@CN/SiO2 catalysts were active, but the Co?N species were dominant active sites. The high activities of the Co@CN/SiO2 catalysts were attributed to the synergistic effect between the Co and N atoms, promoting heterolytic cleavage of hydrazine to form H+/H? pairs. Representative examples demonstrated that the Co@CN/SiO2-500 could completely transform various halogen-substituted nitro aromatics to the corresponding halogenated anilines with high TOFs and selectivity of '99.5 percent.
Sheng, Yao,Wang, Xueguang,Yue, Shengnan,Cheng, Gonglin,Zou, Xiujing,Lu, Xionggang
p. 4632 - 4641
(2020/07/30)

Highly selective hydrogenation of halogenated nitroarenes over Ru/CN nanocomposites by: In situ pyrolysis
A highly chemoselective and recyclable ruthenium catalyst for the hydrogenation of halogenated nitroarenes has been prepared via the simple in situ calcination of a mixture of melamine, glucose and ruthenium trichloride. Superfine Ru particles (2.3 ± 0.3 nm) were obtained and highly dispersed in the nitrogen-doped carbon matrix. The Ru/CN catalyst smoothly transforms a variety of halogenated nitroarenes to the corresponding haloanilines with high intrinsic activity (e.g. TOF = 1333 h-1 for p-chloronitrobenzene) and selectivity of more than 99.6percent. Furthermore, through an analysis of the products in the reaction process, it was concluded that there are two parallel reaction pathways (a direct pathway and an indirect pathway) for the hydrogenation of aromatic nitro compounds over the Ru/CN catalyst, and the direct pathway was proved to be dominant in catalyzing the intermediates. This journal is
Yue, Shengnan,Wang, Xueguang,Li, Shaoting,Sheng, Yao,Zou, Xiujing,Lu, Xionggang,Zhang, Chunlei
p. 11861 - 11869
(2020/07/28)

Iron oxide modified N-doped porous carbon derived from porous organic polymers as a highly-efficient catalyst for reduction of nitroarenes
Fabrication of cost-effective non-noble metal-based catalysts is significant for heterogeneous catalysis. Here, we prepared a porous organic polymer (POP) through the facile condensation of p-phenylenediamine with ferrocene carboxaldehyde, and then the ferrocene-functionalized POP material was carbonized under inert atmosphere, obtaining the γ-Fe2O3 nanoparticles (NPs) modified N-doped porous carbon catalyst (γ-Fe2O3/NPC). Various characterizations (such as XRD, BET, TEM and XPS etc.) indicated that the obtained γ-Fe2O3/NPC catalyst exhibits unique structural properties with uniformly dispersed γ-Fe2O3 species, porous morphology, and N-doped defective amorphous carbon. The γ-Fe2O3/NPC catalyst shows excellent activity in the catalytic reduction of nitroarenes with hydrazine hydrate as reductant. The synergistic effect between γ-Fe2O3 NPs and N-doped porous carbon improve the hydrazine hydrate adsorption and activation for active hydrogen atoms production, which is beneficial for nitroarenes reduction. Moreover, the γ-Fe2O3/NPC catalyst could be easily recycled by using a magnet and reused without obviously loss of catalytic activity. Therefore, this work should provide a useful platform for designing and fabricating stable non-noble metal NPs based catalysts derived from POP materials that have potential for various catalytic applications.
Dong, Zhengping,Liu, Zhengtang,Lv, Jing
(2020/10/27)

Sustainable visible light assisted in situ hydrogenation via a magnesium-water system catalyzed by a Pd-g-C3N4 photocatalyst
A non-hazardous and relatively mild protocol was formulated for an effectual hydrogen generation process via a "magnesium-activated water" system with a Pd-g-C3N4 photocatalyst under visible light at room temperature. Water functions photochemically as a hydrogen donor without any external source with the Pd-g-C3N4 photocatalyst. The synthesized Pd-g-C3N4 photocatalyst is highly efficient under visible light for the selective reduction of a wide range of unsaturated derivatives and nitro compounds to afford excellent yields (>99%). The photocatalyst Pd-g-C3N4 could be easily recovered and reused for several runs without any deactivation during the photochemical hydrogen transfer reaction process.
Sharma, Priti,Sasson, Yoel
supporting information
p. 261 - 268
(2019/01/28)

Bi-functional catalyst of porous N-doped carbon with bimetallic FeCu for solvent-free resultant imines and hydrogenation of nitroarenes
The efficient and stable catalyst applied to the transformation of amines into the corresponding imines and hydrogenation of nitroarenes under mild reaction conditions is reported. The catalytic performance of porous N-doped carbon with FeCu (FeCu@NPC) catalyst are tested by aromatic alcohol-based N-alkylated of amines with solvent-free and hydrogenation of nitroarenes via N2H4·H2O. The results proved that the yield of these two reactions are all over 99.9% under optimum condition. Moreover, the synergistic effect of the catalyst for N-alkylated reaction was investigated through the kinetic study. The catalyst can be easily separated from reaction system by an external magnetism, and can be recycled and reutilized for at least 4 runs with conversions are all over 75%. The study of the catalyst indicated that it was suitable for the reactions in industry. Hence, the catalysis process by the inexpensive metals-based catalyst is green and sustainable.
Wang, Kaizhi,Gao, Wenbing,Jiang, Pengbo,Lan, Kai,Yang, Ming,Huang, Xiaokang,Ma, Lei,Niu, Fang,Li, Rong
p. 43 - 53
(2019/01/08)

Co-MOF-Derived Hierarchical Mesoporous Yolk-shell-structured Nanoreactor for the Catalytic Reduction of Nitroarenes with Hydrazine Hydrate
Porous nanoreactors demonstrate immense potential for applications in heterogeneous catalysis due to their excellent mass-transfer performance and stability. The design of a simple, universal strategy for fabricating nanoreactor catalysts is of significance for organic transformation. In this study, a nanoreactor with a hierarchical mesoporous yolk-shell structure was successfully prepared by the high-temperature carbonization of a ZIF-67@polymer composite. The core of the resultant Co@ZDC@mC material comprised Co NPs anchored in the ZIF-67-derived carbon framework, while the shell comprised resin-polymer-derived mesoporous carbon. The as-obtained Co@ZDC@mC-700 catalyst enriched reactants, efficiently catalyzed the reaction in the core, and permitted the desorption of the product from the nanoreactor. In the catalytic reduction of nitrobenzene with N2H4?H2O, Co@ZDC@mC-700 exhibited superior catalytic efficiency (TOF=1136.3 h?1). In addition, Co@ZDC@mC-700 exhibited excellent performance for the catalytic reduction of various functionalized nitroarenes, as well as good reusability and recyclability. Hence, a simple, useful approach for fabricating a metal-organic-framework-derived non-noble metal-based yolk-shell nanoreactor for effective catalytic transformation is proposed.
Yuan, Man,Zhang, Hongbo,Yang, Chen,Wang, Fanhao,Dong, Zhengping
p. 3327 - 3338
(2019/07/04)

Na2S-promoted reduction of azides in water: Synthesis of pyrazolopyridines in one pot and evaluation of antimicrobial activity
Reduction of various azides using Na2S has been accomplished in water, and, in situ, the resulting amines on reaction with various ketones lead to pyrazolo[3,4-b]pyridines in one pot. Thus, a number of new trifluoromethyl-substituted pyrazolo[3,4-b]pyridine compounds have been prepared and screened for antimicrobial activity against different Gram-positive and Gram-negative strains. A good number of compounds, 4a, 4b, 4d, 4f, 4i, 4k, 4l, 4m, 4r and 4s, were found to possess promising activity. Notably, Na2S on hydrolysis in water generates H2S and NaOH, which facilitate the reduction of azides followed by intramolecular cyclization leading to the title compounds. To the best of our knowledge, this is the first report of the synthesis of the title compounds in aqueous medium in a one-pot reaction.
Kale, Ashok,Medishetti, Nagaraju,Kanugala, Sirisha,Ganesh Kumar,Atmakur, Krishnaiah
p. 3186 - 3194
(2019/03/26)

Method for synthesizing 2, 4-dichloroaniline by continuous chlorination process
The invention relates to a continuous chlorination method for synthesizing 2, 4-dichlorophenol. The method comprises following steps: mixing acetanilide generated by acetylation of aniline with a certain amount of acetic acid; carrying out continuous chlorination, flash concentration and centrifugal filtration to obtain 2, 4-dichloroacetanilide, taking 2, 4-dichloroacetanilide as a raw material, and carrying out hydrolyzing under an acidic condition, cooling, crystallizing and filtering to obtain a hydrochloride of 2, 4-dichloroacetanilide, adding water into an obtained filter cake to dilute,adjusting the pH value, filtering, washing with water, and drying to obtain high-purity 2, 4-dichloroacetanilide. Compared with other patent literatures, the method has the advantages that continuouschlorination is realized, the operation is safe, the reaction speed is high, the chlorine loss is low, and the chlorine and the solvent are recycled, so that the conversion rate and purity of the target product are improved, the purification steps are reduced, the generation of three wastes is reduced, and the method has relatively great economic benefits and environmental protection benefits.
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(2020/01/03)

AN IMPROVED ONE POT, ONE STEP PROCESS FOR THE HALOGENATION OF AROMATICS USING SOLID ACID CATALYSTS
The present invention disclosed an improved one pot, one step process for halogenation of compound of formula (II) to afford corresponding halogenated compound of formula (I) having improved yield and increased selectivity under very mild conditions.
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Page/Page column 0065

(2019/04/18)

Preparation of Well-Ordered Mesoporous-Silica-Supported Ruthenium Nanoparticles for Highly Selective Reduction of Functionalized Nitroarenes through Transfer Hydrogenation
MCM-41-type mesoporous silica (OMS-IL) was prepared by using an ionic liquid (1-hexadecyl-3-methylimidazolium bromide) as a template. The XRD and TEM results demonstrated that OMS-IL was more stable than the MCM-41 material. Ru nanoparticles were supported on OMS-IL (Ru/OMS-IL) by impregnating OMS-IL with a RuCl3 aqueous solution, and the resulting material was used for the selective reduction of nitroarenes. The effects of the components of the catalysts and the reaction conditions on the catalytic behavior of the prepared catalysts were investigated in detail. Ru/OMS-IL exhibited high 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. The Ru/OMS-IL catalysts were highly stable and could easily be recovered by simple filtration over at least six recycling reactions without any observable loss in catalytic performance.
Wei, Ning,Zou, Xiujing,Huang, Haigen,Wang, Xueguang,Ding, Weizhong,Lu, Xionggang
supporting information
p. 209 - 214
(2018/01/26)

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)

Aminal-based Hypercrosslinked Polymer Modified with Small Palladium Nanoparticles for Efficiently Catalytic Reduction of Nitroarenes
Fabrication of heterogeneous catalysts with excellent activity, selectivity and stability is significant for various catalytic applications. Here, we prepared a hypercrosslinked polymer (HCP) via a facile and cost-effective strategy using ferrocenecarboxaldehyde and melamine as building blocks. Then, the HCP was modified with highly dispersed ultrafine Pd nanoparticles (Pd/HCP). The obtained Pd/HCP shows excellent catalytic activity in the catalytic reduction of nitroarenes under mild reaction conditions. It′s worth mentioning that the N atoms in the HCP can efficiently coordinate Pd ions to form small Pd nanoparticles (NPs) and subsequently prevent the aggregation and leaching of Pd NPs during the reaction, so the Pd/HCP catalyst is highly stable and can be reused at least eight cycles without loss of catalytic activity. Therefore, this work may provide possibilities for using HCPs as ideal supporting materials for fabricating highly stable and efficient heterogeneous catalysts.
Xu, Dan,Wang, Fushan,Yu, Guiqin,Zhao, Hong,Yang, Jing,Yuan, Man,Zhang, Xiaoyun,Dong, Zhengping
p. 4569 - 4577
(2018/09/11)

Catalytic hydrogenation process of chlorine-containing nitro aromatic compound
The invention discloses a catalytic hydrogenation process of a chlorine-containing nitro aromatic compound. The specific process comprises the following steps: adding a chlorine-containing nitrobenzene, water and an anti-dechlorination agent into a reactor, carrying out mixing by stirring, then adding a catalyst and a self-prepared cocatalyst, introducing nitrogen into the reactor for 5-10 min toreplace air in the reactor, then introducing hydrogen until the pressure is 18-26 kg, carrying out a reaction at 55-75 DEG C for 1-3 hours, carrying out cooling to room temperature after the reactionis finished, and detecting the content of the target product in the obtained product. The process conditions are mild, the effect of the reaction substrate on the catalyst is small, the catalytic activity is high, and the yield of the product is high.
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Paragraph 0028; 0029; 0030; 0031

(2018/11/27)

Biomass Sucrose-Derived Cobalt@Nitrogen-Doped Carbon for Catalytic Transfer Hydrogenation of Nitroarenes with Formic Acid
Fabrication of non-noble metal-based heterogeneous catalysts by a facile and cost-effective strategy for ecofriendly catalytic transfer hydrogenation (CTH) is of great significance for organic transformations. A cobalt@nitrogen-doped carbon (Co@NC) catalyst was prepared from renewable biomass-derived sucrose, harmless melamine, and earth-abundant Co(AcO)2 as the precursor materials by hydrothermal treatment and carbonization. Co nanoparticles (NPs) were coated with NC shells and uniformly embedded in the NC framework. The as-obtained Co@NC-600 (carbonized at 600 °C) catalyst exhibited excellent catalytic efficiency for CTH of various functionalized nitroarenes with formic acid (FA) as hydrogen donor in aqueous solution. The uniformly incorporated N atoms in the C matrix and the encapsulated Co NPs showed synergistic effects in the CTH reactions. A mechanistic analysis indicated that the protons from FA were activated by Co sites after being captured by N atoms, and then reacted with nitroarenes adsorbed on the surface of the catalysts to generate the corresponding aromatic amines. Moreover, the catalyst showed excellent durability and reusability without obvious decrease in activity even after five reaction cycles. Thus, the study reported herein provides a cost-effective, sustainable strategy for fabrication of biomass-derived non-noble metal-based catalysts for green and efficient catalytic transformations.
Yuan, Man,Long, Yu,Yang, Jin,Hu, Xiwei,Xu, Dan,Zhu, Yangyang,Dong, Zhengping
p. 4156 - 4165
(2018/11/01)

A chloro nitrobenzene selective catalytic hydrogenation synthesis chloro aniline method and catalyst
The invention relates to a method for synthesizing chloroaniline and particularly relates to a method and a catalyst for synthesizing chloroaniline from chloronitrobenzene by virtue of selective catalytic hydrogenation. According to the method, a supported noble metal catalyst is utilized, hydrogen serves as a hydrogen source, chloronitrobenzene is subjected to selective hydrogenation in a liquid phase system to generate chloroaniline, and the selective hydrogenation process is presented by the following formula in the specification by virtue of liquid chromatography-mass spectrometric detection. The method is high in efficiency and reaction selectivity, mild in reaction condition and low in cost, and the operation is easily controlled.
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Paragraph 0032; 0033; 0034; 0035

(2017/08/25)

Copper-Based Intermetallic Electride Catalyst for Chemoselective Hydrogenation Reactions
The development of transition metal intermetallic compounds, in which active sites are incorporated in lattice frameworks, has great potential for modulating the local structure and the electronic properties of active sites, and enhancing the catalytic activity and stability. Here we report that a new copper-based intermetallic electride catalyst, LaCu0.67Si1.33, in which Cu sites activated by anionic electrons with low work function are atomically dispersed in the lattice framework and affords selective hydrogenation of nitroarenes with above 40-times higher turnover frequencies (TOFs up to 5084 h-1) than well-studied metal-loaded catalysts. Kinetic analysis utilizing isotope effect reveals that the cleavage of the H-H bond is the rate-determining step. Surprisingly, the high carrier density and low work function (LWF) properties of LaCu0.67Si1.33 enable the activation of hydrogen molecules with extreme low activation energy (Ea = 14.8 kJ·mol-1). Furthermore, preferential adsorption of nitroarenes via a nitro group is achieved by high oxygen affinity of LaCu0.67Si1.33 surface, resulting in high chemoselectivity. The present efficient catalyst can further trigger the hydrogenation of other oxygen-containing functional groups such as aldehydes and ketones with high activities. These findings demonstrate that the transition metals incorporated in the specific lattice site function as catalytically active centers and surpass the conventional metal-loaded catalysts in activity and stability.
Ye, Tian-Nan,Lu, Yangfan,Li, Jiang,Nakao, Takuya,Yang, Hongsheng,Tada, Tomofumi,Kitano, Masaaki,Hosono, Hideo
p. 17089 - 17097
(2017/12/06)

Efficient chemoselective hydrogenation of halogenated nitrobenzenes over an easily prepared γ-Fe2O3-modified mesoporous carbon catalyst
Efficient chemoselective hydrogenation of halogenated nitrobenzenes using low-cost catalysts is an important research area of applied catalysis. In this work, a Fe metal organic gel (Fe-MOG) was prepared via metal coordination interaction between Fe(NO3)3·9H2O and 1,4-naphthalenedicarboxylic acid. Fe-MOG was used as the precursor for the fabrication of a low-cost γ-Fe2O3-modified mesoporous carbon catalyst (γ-Fe2O3/MC) through carbonization under an N2 atmosphere at high temperature. The obtained γ-Fe2O3/MC catalyst had high catalytic activity and selectivity for the hydrogenation of Cl-, Br- and I- functionalized nitrobenzenes without any obvious dehalogenation. The hydrogenation reactions had a product yield and selectivity for the corresponding halogenated aniline of 100% when using hydrazine hydrate as the reducing agent. The whole hydrogenation reaction process was environmentally friendly because of its harmless byproducts (H2O and N2). In addition, the γ-Fe2O3/MC catalyst was recyclable because of the magnetism of the γ-Fe2O3 active sites. The catalytic activity of the γ-Fe2O3/MC catalyst was not obviously decreased after being recycled five times. Therefore, the γ-Fe2O3/MC catalyst has great potential for future applications in the chemoselective hydrogenation of halogenated nitrobenzenes.
Tian, Meng,Cui, Xueliang,Yuan, Man,Yang, Jin,Ma, Jiantai,Dong, Zhengping
p. 1548 - 1554
(2017/05/10)

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)

Highly active Ru-g-C3N4 photocatalyst for visible light assisted selective hydrogen transfer reaction using hydrazine at room temperature
The present study describes the highly efficient heterogeneous photoactive catalyst Ru-g-C3N4 screened for selective transfer hydrogenation of nitroarenes and olefins. Photoactive catalyst Ru-g-C3N4 exhibits excellent reactivity in visible light under very mild reaction conditions via using hydrazine hydrate as a source of hydrogen with high turnover number. The easily separable heterogeneous photoactive Ru-g-C3N4 catalyst is straightforward to handle in visible light (LED lamp), non-toxic, environmentally friendly and at the same time eliminates the use of high pressure hydrogenation reactors without the need for external sources of energy.
Sharma, Priti,Sasson, Yoel
p. 48 - 52
(2017/08/30)

Method for preparing halogenated aniline from halogenated nitrobenzene through catalytic hydrogenation
The invention discloses a method for preparing halogenated aniline from halogenated nitrobenzene through catalytic hydrogenation. The method comprises the following steps: in a reaction kettle, performing liquid phase catalytic hydrogenation reaction to halogenated nitrobenzene under the action of a sulfur-doped carbon material loaded noble metal catalyst, to obtain halogenated aniline shown in the formula (II), wherein the loading quantity of noble metal in the sulfur-doped carbon material loaded noble metal catalyst is 0.1-5wt%. In the method, the catalyst has good stability, the hydrogenation halogen removal side effect can be effectively inhibited under the condition of having no added halogen removal inhibitor, and the product selectivity is high.
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Paragraph 0051-0053; 0060-0063

(2017/07/22)

Cation Radical Accelerated Nucleophilic Aromatic Substitution via Organic Photoredox Catalysis
Nucleophilic aromatic substitution (SNAr) is a direct method for arene functionalization; however, it can be hampered by low reactivity of arene substrates and their availability. Herein we describe a cation radical-accelerated nucleophilic aromatic substitution using methoxy- and benzyloxy-groups as nucleofuges. In particular, lignin-derived aromatics containing guaiacol and veratrole motifs were competent substrates for functionalization. We also demonstrate an example of site-selective substitutive oxygenation with trifluoroethanol to afford the desired trifluoromethylaryl ether.
Tay, Nicholas E. S.,Nicewicz, David A.
supporting information
p. 16100 - 16104
(2017/11/22)

Recyclable and Selective Nitroarene Hydrogenation Catalysts Based on Carbon-Coated Cobalt Oxide Nanoparticles
Co/CoO nanoparticles coated with graphene layers (Co/CoO@Carbon) have been developed through direct heating treatment of cobalt oxide precursors incipiently deposited over nanographite materials. Cobalt oxides are partially reduced to active zero-valent metal species and the simultaneous formation of carbon layers over the nanoparticles protects them from oxidation and deactivation. This nanocatalyst performs excellently in chemoselective hydrogenation of some challenging nitroarenes with reducible functionalities to the corresponding anilines. The catalyst is kept in active and selective performance in a ten-run recycling test.
Chen, Bingfeng,Li, Fengbo,Huang, Zhijun,Yuan, Guoqing
p. 1132 - 1138
(2016/04/05)

Continuous-flow synthesis of primary amines: Metal-free reduction of aliphatic and aromatic nitro derivatives with trichlorosilane
The metal-free reduction of nitro compounds to amines mediated by trichlorosilane was successfully performed for the first time under continuous-flow conditions. Aromatic as well as aliphatic nitro derivatives were converted to the corresponding primary amines in high yields and very short reaction times with no need for purification. The methodology was also extended to the synthesis of two synthetically relevant intermediates (precursors of baclofen and boscalid).
Porta, Riccardo,Puglisi, Alessandra,Colombo, Giacomo,Rossi, Sergio,Benaglia, Maurizio
supporting information
p. 2614 - 2619
(2017/01/10)

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)

A metal-organic framework-templated synthesis of γ-Fe2O3 nanoparticles encapsulated in porous carbon for efficient and chemoselective hydrogenation of nitro compounds
The γ-Fe2O3 nanoparticles well dispersed in porous carbon were fabricated via a Fe-based metal-organic framework-templated pyrolysis. The resultant product exhibits excellent catalytic activity, chemoselectivity and magnetic recyclability for the hydrogenation of diverse nitro compounds under mild conditions.
Li, Yang,Zhou, Yu-Xiao,Ma, Xiao,Jiang, Hai-Long
supporting information
p. 4199 - 4202
(2016/03/19)

Nitrogen-doped graphene-activated iron-oxide-based nanocatalysts for selective transfer hydrogenation of nitroarenes
Nanoscaled iron oxides on carbon were modified with nitrogen-doped graphene (NGr) and found to be excellent catalysts for the chemoselective transfer hydrogenation of nitroarenes to anilines. Under standard reaction conditions, a variety of functionalized and structurally diverse anilines, which serve as key building blocks and central intermediates for fine and bulk chemicals, were synthesized in good to excellent yields.
Jagadeesh, Rajenahally V.,Natte, Kishore,Junge, Henrik,Beller, Matthias
p. 1526 - 1529
(2015/03/14)

Preparation and characterization of Ni/mZSM-5 zeolite with a hierarchical pore structure by using KIT-6 as silica template: An efficient bi-functional catalyst for the reduction of nitro aromatic compounds
Ni/mZSM-5 and Ni/H-mZSM-5 were synthesized as hierarchical (micro/meso porous) ZSM-5 zeolites by an indirect template method for the first time. The resulting zeolite materials exhibited significantly enhanced diffusional properties in comparison to purely microporous zeolite materials. The structural and morphological characterization of the prepared catalysts was investigated using XRD, BET, atomic absorption spectroscopy, FT-IR, 27Al-MAS NMR, SEM, TEM, XPS and DRS-UV techniques. These hierarchical zeolites were used as acid-metal bi-functional heterogeneous catalysts for hydride transfer in the reduction of nitro aromatic compounds. In these reactions, NaBH4 was used as a reducing agent. Excellent yields at room temperature and very short reaction times in aqueous media conditions were obtained. Reusability experiments showed the excellent stability of Ni/mZSM-5 and Ni/H-mMZSM-5 and the catalysts could be reused 7 times without much loss of activity in reduction of nitro aromatic compounds. Surprisingly, the acid form of Ni/H-mZSM-5 showed much higher activity than that of Ni/mZSM-5. High yield, short reaction time, green solvent (water), room temperature, no by-product, the easy reusability of catalysts and the low amounts of catalyst required are some of the advantages of these catalysts.
Mazaheri, Omid,Kalbasi, Roozbeh Javad
p. 34398 - 34414
(2015/04/27)

Facile protocol for reduction of nitroarenes using magnetically recoverable CoM0.2Fe1.8O4 (M = Co, Ni, Cu and Zn) ferrite nanocatalysts
Transition metal doped cobalt ferrite (CoM0.2Fe1.8O4 (M = Co, Ni, Cu, Zn)) nanoparticles were fabricated using the sol-gel methodology. The obtained ferrite nanoparticles were annealed at 400 °C and characterized using Fourier transform infra-red spectroscopy (FT-IR), X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), vibrating sample magnetometry (VSM) and energy dispersive X-ray (EDX) and scanning transmission electron microscopy (STEM). In the FT-IR spectra two bands in the range 1000-400 cm-1 were observed corresponding to the M-O bond in the tetrahedral and octahedral sites. XRD patterns confirmed the formation of a cubic spinel structure with a Fd3m space-group. HR-TEM analysis revealed a quasi-spherical shape with particle sizes in the range 20-30 nm for all the synthesized ferrite nanoparticles. The lattice inter-planar distances of 0.29, 0.25, 0.21 and 0.16 nm obtained from HR-TEM corresponding to the (2 2 0), (3 1 1), (4 0 0) and (5 1 1) lattice planes respectively were in complete agreement with the XRD data. The EDX-STEM confirmed the elemental composition as per the desired stoichiometric ratio. The catalytic efficiency of the synthesized ferrite samples was explored for the reduction of nitrophenols. Cu substituted cobalt ferrite nanoparticles (CoCu0.2Fe1.8O4) possessed excellent catalytic activity while CoM0.2Fe1.8O4 (M = Co, Ni and Zn) were inactive for the same. The substrate scope of the developed protocol was also evaluated for the reduction of various CH3-, NH2-, Br-, Cl- etc. substituted nitroaromatic compounds.
Goyal, Ankita,Kapoor, Surbhi,Samuel, Pankaj,Kumar, Vinod,Singhal, Sonal
p. 51347 - 51363
(2015/06/25)

Preparation of aniline derivatives
In the present invention, provided is a novel manufacturing method of aniline derivative, which is more simple and eco-friendly and takes less cost compared with an existing synthesizing aniline method, comprising a step of manufacturing chemical formula 1 by making chemical formula 2 react with chemical formula 3 under catalyst, bases and solvents wherein the manufacturing method aniline derivative is manufactured through one pot in a simple manner and accordingly easily removes the solvent with use of distillation under reduced pressure after reaction.
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Paragraph 0087-0092

(2016/10/08)

Recyclable ionic liquid iodinating reagent for solvent free, regioselective iodination of activated aromatic and heteroaromatic amines
This article describes a simple, efficient method for iodination of activated aromatic and heteroaromatic amines using recyclable 1-butyl-3-methylpyridinium dichloroiodate (BMPDCI) as an ionic liquid iodinating reagent, in the absence of any solvent. The main advantages are a simple efficient procedure, good yields and no need for any base/toxic heavy metals, or oxidizing agents. The ionic liquid was recovered and recycled in five subsequent reactions, without much loss of activity. This method was applied for the synthesis of the antiprotozoal drug iodoquinol and the antifungal drug clioquinol.
Deshmukh, Amarsinh,Gore, Babasaheb,Thulasiram, Hirekodathakallu V.,Swamy, Vincent P.
p. 88311 - 88315
(2015/11/09)

Selective reduction of halogenated nitroarenes with hydrazine hydrate in the presence of Pd/C
A large variety of halogenated nitroarenes have been selectively reduced with hydrazine hydrate in the presence of Pd/C to give the corresponding (halogenated) anilines in good yield.
Li, Fang,Frett, Brendan,Li, Hong-Yu
p. 1403 - 1408
(2014/06/23)

Copper-catalyzed ortho-halogenation of protected anilines
A practical Cu-catalyzed direct ortho-halogenation of anilines under aerobic conditions has been developed. The reaction shows typically excellent mono-substitution selectivity, high ortho-regiocontrol and large functional group tolerance.
Urones, Beatriz,Martinez, Angel Manu,Rodriguez, Nuria,Arrayas, Ramon Gomez,Carretero, Juan C.
p. 11044 - 11046
(2013/11/19)

One-pot photo-reductive N-alkylation of aniline and nitroarene derivatives with primary alcohols over Au-TiO2
We report the photo-catalytic N-alkylation of aniline by Au-TiO 2. We successfully alkylate aniline with several primary alcohols. The combined selectivities of mono- and di-alkylated products were always in excess of 70% and dependent on the alkylating alcohol used. A one-pot reaction from nitrobenzene was found to be possible with several substrates. Preliminary experiments showed that this approach could be adopted for the production of lactams using terminal amino-alcohols. The Royal Society of Chemistry 2013.
Stibal, David,Sa, Jacinto,Bokhoven, Jeroen A. Van
p. 94 - 98
(2013/04/10)

One-pot conversion of phenols to anilines via Smiles rearrangement
A convenient one-pot synthesis of phenols to anilines using 2-chloroacetamide/K2CO3/DMF system catalyzed by KI via Smiles rearrangement has been described. The synthesis of extensive amino aromatic products from phenols containing electron withdrawing group, has been performed in moderate to excellent yields to demonstrate the potentiality of this method in bio-medicinal and pharmaceutical applications.
Xie, Yong-Sheng,Vijaykumar,Jang, Kiwan,Shin, Hong-Hyun,Zuo, Hua,Shin, Dong-Soo
p. 5151 - 5154
(2013/09/02)

Metal-free C-N bond-forming reaction: Straightforward synthesis of anilines, through cleavage of aryl C-O bond and amide C-N bond
An efficient metal-free C-N bond forming reaction through cleavage of aryl C-O bond and amide C-N bond has been developed. This process represents a practical method for the facile construction of anilines with a broad substrate scope and wide functional group tolerance in moderate to excellent yields.
Yu, Jianzhong,Zhang, Peizhi,Wu, Jun,Shang, Zhicai
supporting information
p. 3167 - 3170
(2013/06/27)

Direct amination of phenols under metal-free conditions
Herein, we disclose the metal-free synthesis of arylamines via the direct amination of phenols using aminating reagents. This reaction procedure uses easy accessible aminating reagents and provides a versatile synthetic route to a broad range of arylamines with various functionalities in good to excellent yield. By using a two-step route of amination and oxidative coupling reaction, we synthesized three naturally occurring carbazole alkaloids: murrayafoline A, mukonine, and clausenine from two commercially available phenols. Georg Thieme Verlag Stuttgart · New York.
Yu, Jianzhong,Wang, Yongtao,Zhang, Peizhi,Wu, Jun
supporting information
p. 1448 - 1454
(2013/07/26)

The use of sodium chlorate/hydrochloric acid mixtures as a novel and selective chlorination agent
Sodium chlorate/hydrochloric acid mixtures were used to chlorinate activated arenes and the α-position of ketones. This chlorination method was used to produce selectively mono-, di-, and trichlorinated compounds by controlling the molarity of sodium chlorate. This reagent proved to be much more efficient and easier to handle than chlorine gas.
Moon, Byung Seok,Choi, Han Young,Koh, Hun Yeong,Chi, Dae Yoon
experimental part
p. 472 - 476
(2011/12/04)

Hydrous zirconia supported iridium nanoparticles: An excellent catalyst for the hydrogenation of haloaromatic nitro compounds
Ir/ZrO2·xH2O was prepared by co-precipitation and characterized by TEM, XRD, and XPS. It showed an excellent catalytic performance for the hydrogenation of haloaromatic nitro compounds to the corresponding amines in the mixture solvent of ethanol and water. The catalyst gave both conversion and selectivity to be over 99.9% for the hydrogenation of p-chloronitrobenzene to p-chloroaniline. Besides the intrinsic characterization of iridium in the hydrogenation of haloaromatic nitro compounds, the high activity and selectivity of Ir/ZrO2·xH2O is probably attributed to the formation of hydrogen bond between substrate and the hydroxyl groups on the surface of the hydrous catalyst or solvent water to activate the N{double bond, long}O bond in nitro group. The activated N{double bond, long}O bond is easy to be attacked by the activated hydrogen, so the hydrogenation is promoted.
Fan, Guang-Yin,Zhang, Lei,Fu, Hai-Yan,Yuan, Mao-Lin,Li, Rui-Xiang,Chen, Hua,Li, Xian-Jun
scheme or table
p. 451 - 455
(2010/11/21)

Iron-catalyzed selective reduction of nitroarenes to anilines using organosilanes
The iron-catalyzed reduction of aromatic nitro compounds to the corresponding anilines applying organosilanes is reported. In the presence of FeX2-R3P catalysts a series of nitroarenes is selectively reduced tolerating a wide range of functional groups.
Junge, Kathrin,Wendt, Bianca,Shaikh, Nadim,Beller, Matthias
experimental part
p. 1769 - 1771
(2010/07/06)

Na4W10O32/ZrO2 nanocomposite prepared via a sol-gel route: A novel, green and recoverable photocatalyst for reductive cleavage of azobenzenes to amines with 2-propanol
Sodium decatungstate-zirconia (Na4W10O32/ZrO2) nanocomposite was prepared through entrapment of Na4W10O32 into zirconia matrix by a sol-gel route. This new nanocomposite was characterized by means of X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), UV-vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and surface area measurement. The nanocomposite was used as a green and recyclable heterogeneous photocatalyst for rapid and efficient reductive cleavage of azobenzenes into their corresponding amines with 2-propanol as a hydrogen donor at room temperature under N2 atmosphere. The reductive cleavage occurs without hydrogenolysis or hydrogenation of reducible moieties, such as -NO2, -OH, -CH3, -OCH3, -COOH, -COCH3, halogen and -CN. The photocatalyst has been reused several times, without observable loss of activity and selectivity. According to the azobenzene reduction, the Na4W10O32/ZrO2 nanocomposite is more effective as a photocatalyst than pure Na4W10O32, showing that the nanocomposite approach could be an excellent choice to improve the photoactivity of POMs.
Farhadi, Saeid,Sepahvand, Shahnaz
experimental part
p. 75 - 84
(2010/06/15)

Chlorination of aniline and methyl carbanilate by N-chlorosuccinimide and synthesis of 1,3,5-trichlorobenzene
Aniline undergoes regioselective trichlorination by N-chlorosuccinimide (NCS) in acetonitrile in good yield. The product 2,4,6-trichoroaniline was converted into 1,3,5-trichlorobenzene by reduction of its diazonium salt. Reaction of the methyl carbamate of aniline with NCS gave only the 2,4-dichlorophenyl carbamate. Copyright Taylor & Francis Group, LLC.
Davis, Matthew C.
experimental part
p. 1100 - 1108
(2009/09/08)

Synthesis of 2,4-dihalogenofluorobenzenes and their antimicrobial and antifungal activity studies
The aim of this study was to synthesize and identify 2,4- dihalogenofluorobenzene (or trihalogenobenzene) derivatives by spectroscopic means, 1H-NMR and 19F-NMR. The 2,4-dihalofluorobenzene derivatives considered were 2,4-dichlorofluorobenzene (1), 2-bromo-4- chlorofluorobenzene (2), 2-iodo-4-chlorofluorobenzene(3), 2,5- dichlorofluorobenzene (4), 2-bromo-5-chlorofluorobenzene (5), 2-iodo-5-chlorofluorobenzene (6). The in vitro antibacterial and antifungal activities of trihalogenobenzene derivatives were studied against the bacteria Staphylococcus aureus ATCC 25923 Gram(+), Bacillus cereus ATCC 6633 Gram(+), Micrococcus flavus (clinical isolate) Gram(+), Morgenella morganii (clinical isolate) Gram(-), Escherichia coli ATCC 27853 Gram(-) and fungus Candida albicans (clinical isolate), obtained from the biology departments of the Pamukkale and Gazi Universities. The antibacterial and antifungal activities were measured by minimum inhibition concentration (MIC) method and the disc-diffusion method used to measure zone diameter against Gram-positive and Gram-negative bacteria and fungi. All these bacteria and fungi were studied against antibiotics to compare the zone diameters with the results from our treatments. Birkhaeuser 2007.
Katircioglu, Hikmet,Logoglu, Elif,Tilki, Tahir,Oektemer, Atilla
p. 205 - 212
(2008/12/21)

A new protocol for selective deprotection of N-tert-butoxycarbonyl protective group (t-Boc) with Sn(OTf)2
A simple and efficient method for the selective removal of N-Boc group by employing tin(II) trifluoromethanesulfonate [Sn(OTf)2] in CH2Cl2 or solvent-free conditions was developed. The scope of this procedure is explored for the deprotection of a variety of amines, including amino acid derivatives.
Bose, D. Subhas,Kumar, K. Kiran,Reddy, A.V. Narsimha
p. 445 - 450
(2007/10/03)

A facile reduction of azides to the corresponding amines with Sm/NiCl2·6H2O system
Azides can be easily reduced to the corresponding amines with Sm/NiCl2·6H2O in excellent yields under mild and neutral conditions.
Wu, Huayue,Chen, Rener,Zhang, Yongmin
p. 189 - 193
(2007/10/03)

Reductions using ZrCl4/NaBH4: A novel and efficient conversion of aromatic, aliphatic nitro compounds to primary amines
A highly novel and efficient reagent system ZrCl4/NaBH4 is used for the production of primary amines from aromatic, aliphatic nitro compounds is described.
Chary, K. Purushothama,Ram, S. Raja,Iyengar
p. 683 - 685
(2007/10/03)

Mechanism of the benzidine disproportionation of (arylhydrazo)pyridines. The reactions of 4-(4-chlorophenylazo)pyridine and -hydrazo)pyridine in acid media
A kinetic and product analysis study of the reactions of 4-(4- chlorophenylhydrazo)pyridine (1) and 4-(4-chlorophenylazo)pyridine (2) in acid media is reported. The disproportionation of two moles of 1 in aqueous sulfuric acid gives one mole of the oxidized product 2, and one mole each of the reduced products 4-chloroaniline and 4-aminopyridine. The azo compound 2, a product of the reaction of 1, undergoes a slower hydroxylation reaction in acid media, and this process was also investigated. The first-formed product in the reaction of 2 is probably 4-(4-hydroxyphenylazo)pyridine, the 4- chlorine being displaced. At the low substrate concentrations used for the kinetic measurements both reactions are straightforward, but at the much higher concentrations used for product isolation studies a complex product mixture results, one of the products being a dimer. The complexity is increased because 1 had to be used as its hydrochloride salt for reasons of stability, and the chloride ion can also react with the diprotonated substrates; chloride ion also accumulates in the system as it is displaced from 2 during the hydroxylation. Thus chloride ion competes with bisulfate ion (present in large excess) for the diprotonated substrates. Nevertheless, complete mechanistic schemes accounting for all of the observed products, including the dimer, could be derived and are presented. Values of pK(BH22+) for 2 and two of the azo products, needed for the kinetic analysis, were measured using the excess acidity equilibrium method. The nucleophile reacting with protonated 2 in the rate-determining step of the hydroxylation was positively identified as being bisulfate ion by an excess acidity analysis. A comparison of the reaction of 1 with the equivalent reactions of two previously studied 4-(arylhydrazo)pyridines, 9 and 10, reveals that the benzidine disproportionation of these molecules is an A1 process with the second protonation being a pre-equilibrium; pK(BH22+) values for the hydrazo compounds could not be measured as they react too quickly, but they could be determined from the kinetic data, using the excess acidity method. The rate-determining step is a thermally allowed 10-electron electrocyclic process of the diprotonated substrate, giving rise to an intermediate that undergoes fast reaction with a molecule of protonated substrate in a thermally allowed 14-electron electrocyclic process to give the observed products.
Cox, Robin A.,Cheon, Kap-Soo,Keum, Sam-Rok,Buncel, Erwin
p. 896 - 906
(2007/10/03)