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Mechanistic Study of Photoelectrochemical Reactions: Phototransient Experiments
A novel channel electrode phototransient expriment for the mechanistic study of photoelectrochemical reactions is described in which the evolution of the photocurrent in time is monitored after the stepwise application of light to the system once steady-state transport-limited currents have been established in the dark.It is shown that the phototransient data in combination with steady-state photocurrent/flow rate data can accomplish mechanistic discriminations which may be impossible using the latter data alone.The theory of the experiment is given and a working surface presented which allows the analysis of experimental transients regardless of the cell geometry or solution flow rate used in their measurement.The approach is applied to the photoelectrochemical reduction of p-bromonitrobenzene in acetonitrile solution at a platinum electrode.The process, in the presence of light of wavelengths near 330 nm, is shown to be of the photo-ECE type.
Compton, Richard G.,Dryfe, Robert A. W.,Hirst, Judy
p. 10497 - 10503
(1994)
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Kinetic Electron Spin Resonance Investigation of the Monohydronitro Free Radical of 2,3,5,6-Tetrachloronitrobenzene
The e.s.r. spectrum of the short-lived monohydronitro radical from 2,3,5,6-tetrachloronitrobenzene has been obtained by ultraviolet photolysis.The kinetics and energetics of radical recombination have been measured with the aid of two techniques: (i) switching off the radiation from a 1 kW ultraviolet lamp and (ii) pulses from an ultraviolet laser.The two sets of data are in good agreement.
Sutcliffe, Leslie H.
p. 1467 - 1470
(1985)
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Homogeneous and Electrochemical Electron-Transfer Reaction of Nitrobenzene Anion Radical Dissolved in Nitrobenzene
Nitrobenzene anion radical was stably prepared by the electrolytic reduction of nitrobenzene solution containing various kinds and amounts of tetraalkylammonium perchlorates.The rate constants of homogeneous electron-transfer reactions of these nitrobenzene anion radicals with nitrobenzene molecules as a solvent were determined by ESR method at various temperatures.These rate constants at 25 deg C were about 107 dm3 mol-1 s-1 and comparable with the rate constant of electron-transfer reaction between nitrobenzene and its anion radical in N,N-dimethylformamide.The quasi-first order rate constants evaluated from these rate constants were about 108 s-1 and were larger than the rate constants of the intramolecular electron-transfer reactions of the anion radical of bis(p-nitrophenyl) compounds except for bis(p-nitrophenyl)methane.The absorption spectrum of the solution of nitrobenzene anion radical in nitrobenzene containing 0.1 M tetrabutylammonium perchlorate or 0.1 M tetraethylammonium perchlorate showed an additional weak peak at about 800 or 900 nm as well as the ordinary peak.The light energies of these additional peaks were in good agreement with the energy values of the optical electron-transfer reactions evaluated according to the theory of Hush from the activation energies of corresponding thermal electron-transfer reactions.The rate constants of electrochemical electron-transfer reactions and the diffusion coefficients of nitrobenzene anion radical in nitrobenzene were also measured.
Suga, Kosaku,Aoyagui, Shigeru
p. 2713 - 2718
(1987)
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Self-powered continuous nitration method and device
The invention belongs to the technical field of organic synthesis application, and particularly relates to a self-powered continuous nitration method and device. According to the method, a raw material (or a raw material solution) and mixed acid (or nitric acid) are added into a self-powered continuous reactor at the same time, reaction feed liquid continuously and circularly flows, is mixed and reacts in a tube pass through self-propelling force generated by stirring of an impeller, the mass and heat transfer process is completed, and the target requirement is met. According to the invention, the mass transfer and heat transfer efficiency can be improved, the heat exchange and heat transfer capabilities are improved, the reaction time is shortened, the risk degree of art is reduced, the thermal runaway risk is avoided, the reaction safety is improved, and the realization of chemical industry intrinsic safety large scale production is facilitated.
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Paragraph 0069-0072

(2021/07/17)

Liquid phase nitration of benzene catalyzed by a novel salt of molybdovanadophosphoric heteropolyacid
A highly efficient and reusable catalyst QA-HPMV was successfully prepared by the reaction of quinoline-2-formic acid (QA) with molybdovanadophosphoric heteropolyacid (H4PMo11VO40, HPMV) for the nitration of benzene. The physical and chemical properties o
Liu, Jianan,Wang, Yanan,Gong, Shuwen,Duan, Wenzeng,Huang, Xianqiang
p. 1270 - 1276
(2021/05/19)

New insight into the electrochemical reduction of different aryldiazonium salts in aqueous solutions
Electrochemical reduction of different aryldiazonium salts in aqueous solution was studied in this work and it is shown that the aryldiazonium salts are converted to the corresponding aryl radical and aryl anion. The results of this research indicate that the reduction of aryldiazonium salts takes place in two single-electron steps. Our data show that when the substituted group on the phenyl ring is H, Cl, OH, NO2, OCH3or SO3?, the corresponding diazonium salt shows poor adsorption characteristics, but when the substituted group is methyl, the corresponding diazonium salt shows strong adsorption characteristics. In the latter case, the voltammogram exhibits three cathodic peaks. In addition, the effect of various substitutions on the aryldiazonium reduction was studied by Hammett's method. The data are show that with increasing electron withdrawing capacity of the substituent, the reduction of corresponding diazonium salt becomes easier.
Goljani, Hamed,Nematollahi, Davood,Sepehrmansourie, Hassan,Tavakkoli, Zahra,Zolfigol, Mohammad Ali
p. 25811 - 25815
(2021/08/09)

Alternative method for the synthesis of triazenes from aryl diazonium salts
An alternative mild method for access to 1-aryl-3,3-dimethyl alkyl triazenes is described. This protocol employs the dropwise addition of a methanolic solution of a carboxylate (RCO2M) or carbonate (CO32?) to a gently heated DMF solution containing an aryl diazonium salt (ArN2+), that had been previously isolated. Presumably homolysis of the weak N–O bond of diazo ether adducts formed in this operation initiates radical pathways that lead to the generation of triazene product. DMF serves as not only a one-electron donor to the diazonium salts employed in this process, but also as a source of dimethylamine radicals that act as a nucleophilic coupling partner. The reaction provides modest yields (ca. 20–40%) across an array of aryl diazonium salts that contain various substitution. Furthermore this unique approach to triazenes contrasts with traditional methods that employ dimethyl amine in reagent form which directly couples with diazonium salts. Seemingly, only one other example employing somewhat similar reaction conditions to this current investigation en route to triazenes has been reported, albeit with lower yields and for one representative example furnished as a side-product. The current work here improves upon the efficiency of this reported result, and further expands the reaction scope.
Abrams
(2021/05/10)

Exploiting a silver-bismuth hybrid material as heterogeneous noble metal catalyst for decarboxylations and decarboxylative deuterations of carboxylic acids under batch and continuous flow conditions
Herein, we report novel catalytic methodologies for protodecarboxylations and decarboxylative deuterations of carboxylic acids utilizing a silver-containing hybrid material as a heterogeneous noble metal catalyst. After an initial batch method development, a chemically intensified continuous flow process was established in a simple packed-bed system which enabled gram-scale protodecarboxlyations without detectable structural degradation of the catalyst. The scope and applicability of the batch and flow processes were demonstrated through decarboxylations of a diverse set of aromatic carboxylic acids. Catalytic decarboxylative deuterations were achieved on the basis of the reaction conditions developed for the protodecarboxylations using D2O as a readily available deuterium source.
?tv?s, Sándor B.,Fül?p, Ferenc,Kónya, Zoltán,Kukovecz, ákos,Márton, András,Mészáros, Rebeka,Pálinkó, István,Szabados, Márton,Varga, Gábor
p. 4685 - 4696
(2021/07/12)

A photoresponsive palladium complex of an azopyridyl-triazole ligand: light-controlled solubility drives catalytic activity in the Suzuki coupling reaction
Herein, the design and synthesis of a click-derived Pd-complex merged with a photoswitchable azobenzene unit is presented. While in thetrans-form of the switch the complex showed limited solubility, the photogeneratedcis-form rendered the molecule soluble in polar solvents. This light-controllable solubility was exploited to affect the catalytic activity in the Suzuki coupling reaction. The effect of the substrate and catalyst concentration and light intensity on the proceeding and outcome of the reaction was studied. Dehalogenation of the aryl iodide starting material was found to be a major side reaction; however, its occurrence was dependent on the applied light intensity.
Gazdag, Tamás,Holczbauer, Tamás,Jablonkai, István,Kalapos, Péter Pál,Kunfi, Attila,London, Gábor,Mayer, Péter J.,Németh, Krisztina
p. 23419 - 23429
(2021/07/13)

The polyhedral nature of selenium-catalysed reactions: Se(iv) species instead of Se(vi) species make the difference in the on water selenium-mediated oxidation of arylamines
Selenium-catalysed oxidations are highly sought after in organic synthesis and biology. Herein, we report our studies on the on water selenium mediated oxidation of anilines. In the presence of diphenyl diselenide or benzeneseleninic acid, anilines react with hydrogen peroxide, providing direct and selective access to nitroarenes. On the other hand, the use of selenium dioxide or sodium selenite leads to azoxyarenes. Careful mechanistic analysis and 77Se NMR studies revealed that only Se(iv) species, such as benzeneperoxyseleninic acid, are the active oxidants involved in the catalytic cycle operating in water and leading to nitroarenes. While other selenium-catalysed oxidations occurring in organic solvents have been recently demonstrated to proceed through Se(vi) key intermediates, the on water oxidation of anilines to nitroarenes does not. These findings shed new light on the multifaceted nature of organoselenium-catalysed transformations and open new directions to exploit selenium-based catalysis.
Capperucci, Antonella,Dalia, Camilla,Tanini, Damiano
supporting information
p. 5680 - 5686
(2021/08/16)

Integration of Pd nanoparticles with engineered pore walls in MOFs for enhanced catalysis
Achieving free-access metal sites with the ability to regulate interactions with substrates is highly desired yet remains a grand challenge in catalysis. Herein, naked Pd nanoparticles were encapsulated inside a metal-organic framework (MOF), giving Pd@MIL-101-NH2. Its activity and selectivity toward de/hydrogenation reactions can be greatly promoted via the MOF pore wall engineering to regulate Pd surrounding microenvironment and substrate adsorption behavior. Creating free-access active sites and regulating their interaction with substrates are crucial for efficient catalysis, yet remain a grand challenge. Herein, naked Pd nanoparticles (NPs) have been encapsulated in a metal-organic framework (MOF), MIL-101-NH2, to afford Pd@MIL-101-NH2. The hydrophobic perfluoroalkyls were post-synthetically modified onto -NH2 group to yield Pd@MIL-101-Fx (x = 3, 5, 7, 11, 15), which engineer the MOF pore walls to regulate Pd surrounding microenvironment and interaction with substrates. As a result, both the dehydrogenation coupling of organosilane and hydrogenation of halogenated nitrobenzenes show that their activity and selectivity can be greatly promoted upon hydrophobic modification due to the favorable substrate enrichment and regulated interactions between Pd and the modified MOF hosts, far surpassing the traditional supported or surfactant-protected Pd NPs. We envision metal NPs@MOF composites would be an ideal platform integrating the inherent activity of well-accessible metal sites with engineered microenvironment via readily tunable MOFs. Regulating the interaction between active sites and substrates is of great importance in catalysis. The common strategy is to modify the surface of active sites (mostly, metal nanoparticles/NPs in heterogeneous catalysts) with diverse molecules, which, unfortunately, is unfavorable to substrate accessibility and, thus, detrimental to activity. Therefore, it is highly desired to develop heterogeneous catalysts featuring naked metal NPs, which are simultaneously able to regulate interaction with substrates. This puts forward long-standing contradictory challenges on metal NP-based catalysts: (1) exposed active sites, requiring naked metal surface, for their good accessibility; (2) functional molecules around active sites, affording tunable interaction with substrates, for enhanced activity and selectivity. To meet the above challenges, we judiciously encapsulate surface-naked metal NPs into MOFs, achieving tunable interaction with substrates by engineering the MOF pore wall microenvironment.
Li, Luyan,Li, Zhixin,Yang, Weijie,Huang, Yamin,Huang, Gang,Guan, Qiaoqiao,Dong, Yemin,Lu, Junling,Yu, Shu-Hong,Jiang, Hai-Long
p. 686 - 698
(2021/02/27)

Ultrathin ZnTi-LDH nanosheets for photocatalytic aerobic oxidation of aniline based on coordination activation
In this work, ZnTi-LDH nanosheets with several monolayer thickness were prepared as photocatalysts for the aerobic oxidation of aniline to yield nitrosobenzene under visible light irradiation. UV-vis DRS, in situ FTIR and XPS results jointly revealed that aniline molecules were efficiently chemisorbed and activated on ZnTi-LDH to form surface coordination active species, improving visible light absorption and inducing the photocatalytic reaction. The surface OH groups on ZnTi-LDH as the Br?nsted base sites facilitated the reductive deprotonation of aniline to form the anilino anion, which was a key step in promoting aniline oxidation. ESR and XPS data suggested that oxygen vacancies (OVs) were formed due to the interaction between exposed OH groups and aniline molecules. The OVs, as the centers to capture photoelectrons, achieve the reduction of oxygen molecules to O2- radicals, which further oxidize anilino species to produce nitrosobenzene. Finally, a possible mechanism was proposed to reveal the photocatalytic process based on the surface coordination activation theory. This journal is
Liu, Cheng,Guo, Wei,Chen, Jinsong,Zou, Junhua,Wang, Zhiwen,Wu, Ling
p. 162 - 170
(2021/01/28)

Ipso Nitration of Aryl Boronic Acids Using Fuming Nitric Acid
The ipso nitration of aryl boronic acid derivatives has been developed using fuming nitric acid as the nitrating agent. This facile procedure provides efficient and chemoselective access to a variety of aromatic nitro compounds. While several activating agents and nitro sources have been reported in the literature for this synthetically useful transformation, this report demonstrates that these processes likely generate a common active reagent, anhydrous HNO3. Kinetic and mechanistic studies have revealed that the reaction order in HNO3 is >2 and indicate that the ?NO2 radical is the active species.
Baucom, Kyle D.,Brown, Derek B.,Caille, Seb,Murray, James I.,Quasdorf, Kyle,Silva Elipe, Maria V.
supporting information

(2021/06/30)

The graphite-catalyzed: ipso -functionalization of arylboronic acids in an aqueous medium: metal-free access to phenols, anilines, nitroarenes, and haloarenes
An efficient, metal-free, and sustainable strategy has been described for the ipso-functionalization of phenylboronic acids using air as an oxidant in an aqueous medium. A range of carbon materials has been tested as carbocatalysts. To our surprise, graphite was found to be the best catalyst in terms of the turnover frequency. A broad range of valuable substituted aromatic compounds, i.e., phenols, anilines, nitroarenes, and haloarenes, has been prepared via the functionalization of the C-B bond into C-N, C-O, and many other C-X bonds. The vital role of the aromatic π-conjugation system of graphite in this protocol has been established and was observed via numerous analytic techniques. The heterogeneous nature of graphite facilitates the high recyclability of the carbocatalyst. This effective and easy system provides a multipurpose approach for the production of valuable substituted aromatic compounds without using any metals, ligands, bases, or harsh oxidants.
Badgoti, Ranveer Singh,Dandia, Anshu,Parewa, Vijay,Rathore, Kuldeep S.,Saini, Pratibha,Sharma, Ruchi
p. 18040 - 18049
(2021/05/29)

Photoinduced Iron-Catalyzed ipso-Nitration of Aryl Halides via Single-Electron Transfer
A photoinduced iron-catalyzed ipso-nitration of aryl halides with KNO2 has been developed, in which aryl iodides, bromides, and some of aryl chlorides are feasible. The mechanism investigations show that the in situ formed iron complex by FeSO4, KNO2, and 1,10-phenanthroline acts as the light-harvesting photocatalyst with a longer lifetime of the excited state, and the reaction undergoes a photoinduced single-electron transfer (SET) process. This work represents an example for the photoinduced iron-catalyzed Ullmann-type couplings.
Wu, Cunluo,Bian, Qilong,Ding, Tao,Tang, Mingming,Zhang, Wenkai,Xu, Yuanqing,Liu, Baoying,Xu, Hao,Li, Hai-Bei,Fu, Hua
p. 9561 - 9568
(2021/08/06)

Photocatalytic oxidative coupling of arylamines for the synthesis of azoaromatics and the role of O2 in the mechanism
The photocatalytic oxidative coupling of aryl amines to selectively synthesize azoaromatic compounds has been realized. Multiple different photocatalysts can be used to perform the general reaction; however, Ir(dF-CF3-ppy)2(dtbpy)+, where dF-CF3-ppy is 2-(2,4-difluorophenyl)-5-(trifluoromethyl)-pyridine and dtpby is 4,4′-tert-butyl-2,2′-bipyridine, showed the greatest range of reactivity with various amine substrates. Both electron-rich and -deficient amines can be coupled with yields up to 95% under an ambient air atmosphere. Oxygen was deemed to be essential for the reaction and is utilized in the regeneration of the photocatalyst. Fluorescence quenching and radical trap experiments indicate an amine radical coupling mechanism that proceeds through a hydrazoaromatic intermediate before further oxidation occurs to form the desired azoaromatic products.
Sitter, James D.,Vannucci, Aaron K.
supporting information
p. 2938 - 2943
(2021/03/01)

Catalyst-free generation of acyl radicals induced by visible light in water to construct C-N bonds
We describe herein a catalyst-free and redox-neutral photochemical strategy for the direct generation of acyl radicals from α-diketones, and its selective conversion of nitrosoarenes to hydroxyamides or amides with AcOH or NaCl as an additive. The reaction was carried out under mild conditions in water with purple LEDs as the light source. A broad scope of substrates was demonstrated. Mechanistic experiments indicate that α-diketones cleave to give acyl radicals, with hydroxyamides being further reduced to amides.
Ran, Maogang,He, Jiaxin,Yan, Boyu,Liu, Wenbo,Li, Yi,Fu, Yunfen,Li, Chao-Jun,Yao, Qiuli
supporting information
p. 1970 - 1975
(2021/03/16)

Boronic Acid Pairs for Sequential Bioconjugation
Boronic acids can play diverse roles when applied in biological environments, and employing boronic acid structures in tandem could provide new tools for multifunctional probes. This Letter describes a pair of boronic acid functional groups, 2-nitro-arylboronic acid (NAB) and (E)-alkenylboronic acid (EAB), that enable sequential cross-coupling through stepwise nickel- and copper-catalyzed processes. The selective coupling of NAB groups enables the preparation of stapled peptides, protein-protein conjugates, and other bioconjugates.
Ball, Zachary T.,Ding, Yuxuan,Miller, Mary K.,Swierczynski, Michael J.
supporting information
p. 5334 - 5338
(2021/07/26)

Valorisation of urban waste to access low-cost heterogeneous palladium catalysts for cross-coupling reactions in biomass-derived γ-valerolactone
Herein we report a simple protocol for the valorisation of a common urban biowaste. The lignocellulosic biomass obtained after the pre-treatment of pine needle urban waste is efficiently transformed into a low-cost support (PiNe) for the immobilization of Pd nanoparticles. The final Pd/PiNe heterogeneous catalyst features a small particle size (4.5 nm) and a metal loading (9.9 wt%) comparable with most commercially available and generally used counterparts. In this contribution, we tested the catalytic efficiency of the Pd/PiNe system in two representative cross-couplings, Heck and Hiyama reactions, and compared the results obtained with commercial Pd/C catalyst. The good reactivity in the biomass-derived solvent (GVL) confirms that the Pd/PiNe heterogeneous catalyst is a valid system that can be integrated into a waste valorization chain within a circular economy approach. In addition, the efficiency of the catalyst has also been extended to perform the challenging consecutive Hiyama-Heck reaction to afford differently substituted (E)-1,2-diarylethenes.
Valentini, Federica,Ferlin, Francesco,Lilli, Simone,Marrocchi, Assunta,Ping, Liu,Gu, Yanlong,Vaccaro, Luigi
p. 5887 - 5895
(2021/08/23)

NITRATION
The present invention relates to a process for preparing a nitrated compound, comprising the step of reacting a compound (A) comprising at least one substituted or unsubstituted aromatic or heteroaromatic ring, wherein said heteroaromatic ring comprises at least one heteroatom selected from the group consisting of oxygen, sulfur, phosphor, selenium and nitrogen, with a compound of formula (I) wherein Y is selected from the group consisting of hydrogen and nitro.
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(2020/05/28)

Selective oxidation of aniline into azoxybenzene catalyzed by Nb-peroxo@iron oxides at room temperature
Oxidation of aniline into valuable products such as azoxybenzene, azobenzene, and nitrobenzene has been a great challenge due to the difficulty of controlling the selectivity of heterogeneous catalysts to form the desired products. In this work, an active and selective heterogeneous catalyst for the oxidation of aniline into azoxybenzene was designed by doping iron oxide supports with niobium and immobilizing Nb-peroxo groups on their surfaces through H2O2treatment. The Nb-peroxo groups on the iron oxide support were essential to catalyze the conversion of aniline into products while the niobium favored the formation of azoxybenzene. Among the alcoholic solvents studied, 1-propanol was the most suitable to get high conversion rates of aniline and high selectivity to azoxybenzene. At 3 h reaction time, the Nb-peroxo@iron oxides led to oxidation of aniline with a conversion rate of 99.6% and 83.7% selectivity to azoxybenzene at room temperature. Since the selective and catalytic oxidation of aniline is very important for the synthesis of intermediates and precursors to various industrially valuable products, the results shown herein may contribute to the development of most stable, selective, and active catalysts under mild reaction conditions.
Lima, André L. D.,Fajardo, Humberto V.,Nogueira, André E.,Pereira, Márcio C.,Oliveira, Luiz C. A.,de Mesquita, Jo?o Paulo,Silva, Adilson C.
p. 8710 - 8717
(2020/06/08)

Efficient and Selective Oxidation of Aromatic Amines to Azoxy Derivatives over Aluminium and Gallium Oxide Catalysts with Nanorod Morphology
Aluminium oxide and gallium oxide nanorods were identified as highly efficient heterogeneous catalysts for the selective oxidation of aromatic amines to azoxy compounds using hydrogen peroxide as environmentally friendly oxidant. This is the first report of the selective oxidation of aromatic amines to their azoxy derivatives without using transition metal catalysts. Among the tested transition-metal-free oxides, gallium oxide nanorods with small dimensions (9–52 nm length and 3–5 nm width) and fully accessible, high surface area (225 m2 g?1) displayed the best catalytic performance in terms of substrate versatility, activity and azoxybenzene selectivity. Furthermore, the catalyst loading, hydrogen peroxide type (aqueous or anhydrous), and the amount of solvent were tuned to optimise the catalytic performance, which allowed reaching almost full selectivity (98 %) towards azoxybenzene at high aniline conversion (94 %). Reusability tests showed that the gallium oxide nanorod catalyst can be recycled in consecutive runs with complete retention of the original activity and selectivity.
Singh, Bhawan,Mandelli, Dalmo,Pescarmona, Paolo P.
p. 593 - 601
(2019/11/13)

Site-specific catalytic activities to facilitate solvent-free aerobic oxidation of cyclohexylamine to cyclohexanone oxime over highly efficient Nb-modified SBA-15 catalysts
The development of highly active and selective heterogeneous catalysts for efficient oxidation of cyclohexylamine to cyclohexanone oxime is a challenge associated with the highly sensitive nitrogen center of cyclohexylamine. In this work, dispersed Nb oxide supported on SBA-15 catalysts are disclosed to efficiently catalyze the selective oxidation of cyclohexylamine with high conversion (>75%) and selectivity (>84%) to cyclohexanone oxime by O2without any addition of solvent (TOF = 469.8 h?1, based on the molar amount of Nb sites). The role of the active-site structure identity in dictating the site-specific catalytic activities is probed with the help of different reaction and control conditions and multiple spectroscopy methods. Complementary to the experimental results, further poisoning tests (with KSCN or dehydroxylation reagents) and DFT computational studies clearly unveil that the surface exposed active centers toward activation of the reactants are quite different: the surface -OH groups can catch the NH2group from cyclohexylamine by forming a hydrogen bond and lead to a more facile cyclohexylamine oxidation to desired products, while the monomeric or oligomeric Nb sites with a highly distorted structure play a key role in the dissociation of O2molecules beneficial for insertion of active oxygen species into cyclohexylamine. These catalysts exhibit not only satisfactory recyclability for cyclohexylamine oxidation but also efficiently catalyze the aerobic oxidation of a wide range of amines under solvent-free conditions.
Ding, Wei,Mao, Liqiu,Peng, Haoyu,Yin, Dulin,Zhong, Wenzhou
p. 3409 - 3422
(2020/06/09)

N-Nitroheterocycles: Bench-Stable Organic Reagents for Catalytic Ipso-Nitration of Aryl- And Heteroarylboronic Acids
Photocatalytic and metal-free protocols to access various aromatic and heteroaromatic nitro compounds through ipso-nitration of readily available boronic acid derivatives were developed using non-metal-based, bench-stable, and recyclable nitrating reagents. These methods are operationally simple, mild, regioselective, and possess excellent functional group compatibility, delivering desired products in up to 99% yield.
Budinská, Alena,Katayev, Dmitry,Passera, Alessandro,Zhang, Kun
supporting information

(2020/03/30)

Synthesis of thioethers, arenes and arylated benzoxazoles by transformation of the C(aryl)-C bond of aryl alcohols
Transformation of aryl alcohols into high-value functionalized aromatic compounds by selective cleavage and functionalization of the C(aryl)-C(OH) bond is of crucial importance, but very challenging by far. Herein, for the first time, we report a novel and versatile strategy for activation and functionalization of C(aryl)-C(OH) bonds by the cooperation of oxygenation and decarboxylative functionalization. A diverse range of aryl alcohol substrates were employed as arylation reagents via the cleavage of C(aryl)-C(OH) bonds and effectively converted into corresponding thioether, arene, and arylated benzoxazole products in excellent yields, in a Cu based catalytic system using O2 as the oxidant. This study offers a new way for aryl alcohol conversion and potentially offers a new opportunity to produce high-value functionalized aromatics from renewable feedstocks such as lignin which features abundant C(aryl)-C(OH) bonds in its linkages.
Chen, Bingfeng,Han, Buxing,Liu, Mingyang,Meng, Qinglei,Song, Jinliang,Zhang, Pei,Zhang, Zhanrong
p. 7634 - 7640
(2020/08/14)

Application of Al2O3/AlNbO4 in the oxidation of aniline to azoxybenzene
Al2O3/AlNbO4 powder was fabricated by a facile high-energy milling process. The precursor materials, Al2O3 and Nb2O5, are readily available and have very attractive properties. Moreover, the catalytic activity of the sample in the liquid phase oxidation of aniline (OA) in the presence of hydrogen peroxide as oxidant was evaluated. The catalyst was found to be highly efficient and selective in the oxidation of aniline to azoxybenzene under mild conditions. When mixed with 28% AlNbO4 the alumina-based catalyst achieved high conversion and selectivity and very similar to the pure Nb2O5.
Batalha, Daniel C.,Luz, Sulusmon C.,Taylor, Jason G.,Fajardo, Humberto V.,Noremberg, Bruno S.,Cherubin, Igor J. S.,Silva, Ricardo M.,Gon?alves, Margarete R. F.,Bergmann, Carlos P.,Valentini, Antoninho,Carre?o, Neftalí L. V.
p. 543 - 553
(2019/09/06)

Practical Transition-Metal-Free Protodeboronation of Arylboronic Acids in Aqueous Sodium Hypochlorite
A concise and practical method was developed for the protodeboronation of arylboronic acids under mild conditions in aqueous NaClO at 100 °C. The strategy is low-cost, transition-metal-free, and base-free.
Li, Minxin,Tang, Yanling,Gao, Jinchun,Rao, Gaoxiong,Mao, Zewei
p. 2039 - 2042
(2020/10/21)

Nanocomposite-based inorganic-organocatalyst Cu(II) complex and SiO2- and Fe3O4 nanoparticles as low-cost and efficient catalysts for aniline and 2-aminopyridine oxidation
Bis-imino Cu(II) complex (CuLAn2), in which the imine ligand (HLAn) acts as a bidentate chelating ligand, was synthesized. The catalytic potential of the inorganic-organocatalyst was studied homogeneously and heterogeneously in the oxidation of aniline and 2-aminopyridine by H2O2 or tBuOOH. Two heterogeneous inorganic-organocatalysts, CuLAn2@Fe3O4 and CuLAn2@SiO2@Fe3O4, were synthesized by the successful immobilization of CuLAn2 on the Fe3O4 surface and the composited Fe3O4 with SiO2, respectively. The heterogeneous structure of those inorganic-organocatalysts was confirmed using Fourier-transform infrared, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, and magnetic properties. The adsorption–desorption isotherms revealed respectable adsorption parameters (SBET, Vp, and rp). All catalysts exhibited high potential in the oxidation of aniline (with phenylhydroxylamine as the main product) and good potential in the oxidation of 2-aminopyridine, in the first attempt (with 2-nitropyridine-N-oxide and 2-nitrosopyridine-N-oxide as main products), at room temperature. Acetonitrile was found to be the best solvent compared to ethanol, dimethyl sulfoxide, chloroform, and water. The homogeneous catalyst exhibited reusability for three times. The heterogeneous catalysts, CuLAn2@Fe3O4 and CuLAn2@SiO2@Fe3O4, were active for five and seven times, respectively. A mechanism was proposed within electron and oxygen transfer processes.
Adam, Mohamed Shaker S.,Al-Omair, Mohammed A.
(2020/09/09)

Microwave-Assisted Decarbonylation of Biomass-Derived Aldehydes using Pd-Doped Hydrotalcites
Catalytic decarbonylation is an underexplored strategy for deoxygenation of biomass-derived aldehydes owing to a lack of low-cost and robust heterogeneous catalysts that can operate in benign solvents. A family of Pd-functionalized hydrotalcites (Pd-HTs) were synthesized, characterized, and applied to the decarbonylation of furfural, 5-hydroxymethylfurfural (HMF), and aromatic and aliphatic aldehydes under microwave conditions. This catalytic system delivered enhanced decarbonylation yields and turnover frequencies, even at a low Pd loading (0.5 mol %). Furfural decarbonylation was optimized in a benign solvent (ethanol) compatible with biomass processing; HMF selectively afforded an excellent yield (93 %) of furfuryl alcohol without humin formation; however, a longer reaction favored the formation of furan through tandem alcohol dehydrogenation and decarbonylation. Yields of the substituted benzaldehydes (37–99 %) were proportional to the calculated Mulliken charge of the carbonyl carbon. Activity and selectivity reflected loading-dependent Pd speciation. Continuous-flow testing of the best Pd-HT catalyst delivered good stability over 16 h on stream, with near-quantitative conversion of HMF.
An, Nan,Ainembabazi, Diana,Reid, Christopher,Samudrala, Kavya,Wilson, Karen,Lee, Adam F.,Voutchkova-Kostal, Adelina
p. 312 - 320
(2019/11/13)

Oxidative bromination of non-activated aromatic compounds with AlBr3/KNO3 mixture
Bromination of non-activated aromatic compounds with reaction mixture containing KNO3 and AlBr3 was studied in liquid substrates and in solvent. Aluminium bromide has three different roles in this reaction mixture. First, it is a source of bromide ions, which are essential in oxidative bromination application. Second, it acts as a catalyst, and lastly, it forms acidic environment via its hydrolysis, which is necessary for enhancement of the oxidising properties of nitrate ions. It was shown that when changing the reaction conditions, different side reactions (like nitration or Friedel–Crafts type arylation) can occur. However, it is possible to guide the reaction path and receive the desired outcome by choosing the suitable reaction conditions. In addition, it was shown that there has to be water content in this reaction mixture as the bromine formation rate depends on it, while there exists an optimal volume of water, where bromine formation is the fastest.
Rahu, Ida,J?rv, Jaak
p. 1219 - 1227
(2019/11/13)

Copper-free Sandmeyer-type Reaction for the Synthesis of Sulfonyl Fluorides
A copper-free Sandmeyer-type fluorosulfonylation reaction is reported. Utilizing Na2S2O5 and Selectfluor as the sulfur dioxide and fluorine sources, respectively, aryldiazonium salts were transformed into sulfonyl fluorides. The one-pot direct synthesis of sulfonyl fluorides from aromatic amines was also realized via in situ diazotization. The practicality of this method was demonstrated by the broad functional group tolerance, gram-scale synthesis, and late-stage fluorosulfonylation of natural products and pharmaceuticals.
Zhong, Tao,Pang, Meng-Ke,Chen, Zhi-Da,Zhang, Bin,Weng, Jiang,Lu, Gui
supporting information
p. 3072 - 3078
(2020/04/10)

Preparation method for compound-type nitrating agent and application thereof in passivation aromatic ring nitration
The invention discloses a preparation method for a compound-type nitrating agent. The preparation method specifically comprises the following steps: firstly using sodium nitrate and bismuth nitrate asactive components, using 1-butyl-3-methylimidazolium hexafluorophosphate as a modifier, and using silica sol as a carrier, preparing a component A; using tetrabutyl titanate as a titanium source, using sodium dodecyl benzene sulfonate as a modifier, and using yttrium chloride as an active component, preparing a component B, enabling the component A and the component B to be mixed, and preparing the compound-type nitrating agent. The nitrating agent prepared by the method is good in stability, excellent in mechanical property, and good in nitration effect while used for nitration of a passivation aromatic ring, and capable of effectively improving a yield of a nitration product.
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Paragraph 0026-0068

(2019/03/08)

Low-temperature catalytic oxidation of aniline to azoxybenzene over an Ag/Fe2O3 nanoparticle catalyst using H2O2 as an oxidant
An in situ modified hydrothermal synthesis of Ag/Fe2O3 nanoparticles (NPs) and studies of their catalytic activity as a simple, eco-friendly and recyclable catalyst for one-pot conversion of aniline to azoxybenzene were performed. The as-synthesized nanostructured material was characterised by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), SEM-mapping, temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption isotherms (BET), Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), ultraviolet-visible spectroscopy (UV-vis) and vibrating sample magnetometer spectroscopy (VSM). The most active and recyclable catalyst with 2-5 nm diameters of the metallic Ag particles supported on 10-50 nm Fe2O3 nanoparticles was formed with a silver loading of 1.8 wt%. A high turnover number of ～592 was achieved with 92% conversion of aniline and 94% selectivity towards the target product azoxybenzene under atmospheric conditions. The effects of various reaction parameters including the reaction time, temperature and substrate to H2O2 molar ratio were screened and studied in detail. The results reveal the role of a synergistic effect between the surface Ag nanoparticles and Fe2O3 nanospheres for high catalytic activity.
Paul, Bappi,Sharma, Sachin K.,Adak, Shubhadeep,Khatun, Rubina,Singh, Gurmeet,Das, Dipak,Joshi, Vedant,Bhandari, Sahil,Dhar, Siddhartha Sankar,Bal, Rajaram
p. 8911 - 8918
(2019/06/18)

Palladium–Borane Cooperation: Evidence for an Anionic Pathway and Its Application to Catalytic Hydro-/Deutero-dechlorination
Metal–Lewis acid cooperation provides new opportunities in catalysis. In this work, we report a new type of palladium–borane cooperation involving anionic Pd0 species. The air-stable DPB palladium complex 1 (DPB=diphosphine-borane) was prepared and reacted with KH to give the Pd0 borohydride 2, the first monomeric anionic Pd0 species to be structurally characterized. The boron moiety acts as an acceptor towards Pd in 1 via Pd→B interaction, but as a donor in 2 thanks to B-H-Pd bridging. This enables the activation of C?Cl bonds and the system is amenable to catalysis, as demonstrated by the hydro-/deutero-dehalogenation of a variety of (hetero)aryl chlorides (20 examples, average yield 85 %).
Kameo, Hajime,Yamamoto, Jun,Asada, Ayaka,Nakazawa, Hiroshi,Matsuzaka, Hiroyuki,Bourissou, Didier
supporting information
p. 18783 - 18787
(2019/11/19)

Continuous-flow Synthesis of Aryl Aldehydes by Pd-catalyzed Formylation of Aryl Bromides Using Carbon Monoxide and Hydrogen
A continuous-flow protocol utilizing syngas (CO and H2) was developed for the palladium-catalyzed reductive carbonylation of (hetero)aryl bromides to their corresponding (hetero)aryl aldehydes. The optimization of temperature, pressure, catalyst and ligand loading, and residence time resulted in process-intensified flow conditions for the transformation. In addition, a key benefit of investigating the reaction in flow is the ability to precisely control the CO-to-H2 stoichiometric ratio, which was identified as having a critical influence on yield. The protocol proceeds with low catalyst and ligand loadings: palladium acetate (1 mol % or below) and cataCXium A (3 mol % or below). A variety of (hetero)aryl bromides at a 3 mmol scale were converted to their corresponding (hetero)aryl aldehydes at 12 bar pressure (CO/H2=1:3) and 120 °C reaction temperature within 45 min residence time to afford products mostly in good-to-excellent yields (17 examples). In particular, a successful scale-up was achieved over 415 min operation time for the reductive carbonylation of 2-bromo-6-methoxynaphthalene to synthesize 3.8 g of 6-methoxy-2-naphthaldehyde in 85 % isolated yield. Studies were conducted to understand catalyst decomposition within the reactor by using inductively coupled plasma–mass spectrometry (ICP–MS) analysis. The palladium could easily be recovered using an aqueous nitric acid wash post reaction. Mechanistic aspects and the scope of the transformation are discussed.
Hone, Christopher A.,Lopatka, Pavol,Munday, Rachel,O'Kearney-McMullan, Anne,Kappe, C. Oliver
p. 326 - 337
(2018/11/23)

Base promoted peroxide systems for the efficient synthesis of nitroarenes and benzamides
A useful and efficient approach for the synthesis of nitroarenes from several aromatic amines (including heterocycles) using peroxide and base has been developed. This oxidative reaction is very easy to handle and afforded the products in good yields. Formation of benzamides from benzylamine was also successfully carried out with this metal-free catalytic system in good to excellent yields.
Gupta, Sampa,Ansari, Alisha,Sashidhara, Koneni V.
supporting information

(2019/09/07)

Novel Mn(III) Porphyrins and Prospects of Their Application in Catalysis
Four novel Mn(III) porphyrins have been synthesized and characterized by UV-Vis, IR, ESI-mass spectroscopy, elemental analysis, magnetic susceptibility studies, TLC, and conductivity measurements. The tentative structure has been proposed. Depolymerization of coal using the synthesized Mn(III) porphyrins have been demonstrated by the optical density method using humic acid as a model of coal. The synthesized complexes have shown excellent depolymerization activity based on comparative studies. Complexes have been successfully applied for the catalytic oxidation of benzyl alcohol, aniline, benzoin, and benzaldehyde into benzaldehyde, nitrobenzene, benzil, and benzoic acid, respectively, at room temperature and pressure.
Bharati,Sarma,Hazarika,Chaurasia,Anand,Yadava
p. 335 - 341
(2019/05/14)

Synthesis, structure, and synthetic potential of arenediazonium trifluoromethanesulfonates as stable and safe diazonium salts
Aromatic diazonium salts are valuable building blocks for organic synthesis; however, in most cases, they are unstable, unsafe, poorly soluble, and/or expensive. In this paper, we have shown that a variety of stable and safe arenediazonium triflates ArN2+ TfO– can be obtained easily and in high yields by diazotization of anilines with tert-butyl nitrite in the presence of trifluoromethanesulfonic acid. Arenediazonium triflates are relatively shelf-stable in the dry state. They dissolve well in water, as well as polar and even nonpolar organic solvents. Less than 800 J/g of energy is released during the thermal decomposition of these salts, which indicates their explosion safety. Arenediazonium triflates have a high reactivity in the known reactions of diazonium chemistry, and undergo an unusual metal-free chlorodediazonization reaction with chloroform and CCl4.
Filimonov, Victor D.,Krasnokutskaya, Elena A.,Kassanova, Assia Zh.,Fedorova, Valentina A.,Stankevich, Ksenia S.,Naumov, Nikolay G.,Bondarev, Alexander A.,Kataeva, Veronika A.
p. 665 - 674
(2018/09/14)

The promoted catalytic hydrogenation performance of bimetallic Ni-Co-B noncrystalline alloy nanotubes
A noncrystalline Ni-B alloy in the shape of nanotubes has demonstrated its superior catalytic performance for some hydrogenation reactions. Remarkable synergistic effects have been observed in many reactions when bimetallic catalysts were used; however, bimetallic noncrystalline alloy nanotubes are far less investigated. Here, we report a simple acetone-assisted lamellar liquid crystal approach for synthesizing a series of bimetallic Ni-Co-B nanotubes and investigate their catalytic performances. The dilution effect of acetone on liquid crystals was characterized by small-angle X-ray diffraction (SAXRD) and scanning electron microscopy (SEM). The Ni/Co molar ratio of the catalyst was varied to study the composition, porous structure, electronic interaction, and catalytic efficiency. In the liquid-phase hydrogenation of p-chloronitrobenzene, the as-prepared noncrystalline alloy Ni-Co-B nanotubes exhibited higher catalytic activity and increased stability as compared to Ni-B and Co-B alloy nanotubes due to electronic interactions between the nickel and cobalt. The excellent hydrogenation performance of the Ni-Co-B nanotubes was attributed to their high specific surface area and the characteristic confinement effects, compared with Ni-Co-B nanoparticles.
Mo, Min,Xie, Mingjiang,Guo, Xiaojuan,Ding, Weiping,Guo, Xuefeng
p. 26456 - 26463
(2019/09/13)

Photocatalytic oxidation of aniline over MO/TiO2 (M = Mg, Ca, Sr, Ba) under visible light irradiation
MO/TiO2 (M = Mg, Ca, Sr & Ba; TiO2: Evonik Aroxide P25) composites were prepared for photocatalytic aniline oxidation under visible light irradiation. The conversion efficiencies of aniline over the samples are revealed as follow ord
Chen, Jinsong,Shen, Chuan,Guo, Binbin,Yu, Yan,Wu, Ling
p. 312 - 318
(2018/12/13)

1D coordination polymer based on copper(II)-containing tetrameric 1,2,3-triazole ligand from click chemistry: Magnetic and catalytic properties
A novel tetrameric tetra[O-((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)]-pentaerythritol (TBTP) has been synthesized using click chemistry strategy. TBTP was characterized and used as ligand to form new Cu(II) complexes, forming 1-D coordination polymers. Two square planar complexes were characterized by single-crystal X-ray diffraction, presenting formula [Cu(TBTP)][Cu(NO3)4] (1) and [Cu(TBTP)](NO3)2 (2). In both structures, a cationic 1-D coordination polymer (CP) has been formed. The CP contain a 1:1 Cu(II)/TBTP ratio with four neutral triazole groups coordinating the Cu(II) center, forming a Cu[sbnd]N bonds ranging 1.988(2)–2.001(2) ?. The study of the magnetic properties of compounds 1 and 2 pointed to an antiferromagnetic behavior for both compounds, defined by inter- and intra-chain dipolar interactions among their metallic centers. In addition, the complex 1 was found to be an efficient catalyst for selective oxidation of aniline to azobenzene under mild reaction conditions.
Moraes, Leonardo C.,de Souza, Gilmar P.,Fajardo, Humberto V.,Luz, Sulusmon C.,álvarez, Eleuterio,Lloret, Francesc,Ribeiro-Viana, Renato M.,Rojo, Javier,Stumpf, Humberto O.,Figueiredo, Rute C.,Corrêa, Rodrigo S.
p. 93 - 99
(2019/02/20)

A convenient room temperature ipso-nitration of arylboronic acid catalysed by molecular iodine using zirconium oxynitrate as nitrating species: An experimental and theoretical investigation
A simple and convenient protocol has been developed for ipso-nitration of arylboronic acid catalysed by molecular iodine at room temperature, using zirconium oxynitrate as the nitrating species. The protocol is applicable to electronically diverse aryl- and heteroarylboronic acid moieties under mild reaction conditions with good to excellent isolated yields. Furthermore, a theoretical investigation has been performed for the same reaction, and reaction profiles are modelled using modern density functional theory (DFT). DFT-based results support the experimentally observed results.
Mahanta, Abhijit,Gour, Nanda Kishor,Sarma, Plaban Jyoti,Borah, Raju Kumar,Raul, Prasanta Kumar,Deka, Ramesh Chandra,Thakur, Ashim Jyoti,Bora, Utpal
(2019/05/15)

Niobium oxide prepared through a novel supercritical-CO2-assisted method as a highly active heterogeneous catalyst for the synthesis of azoxybenzene from aniline
High-surface area Nb2O5 nanoparticles were synthesised by a novel supercritical-CO2-assisted method (Nb2O5-scCO2) and were applied for the first time as a heterogeneous catalyst in the oxidative coupling of aniline to azoxybenzene using the environmentally friendly H2O2 as the oxidant. The application of scCO2 in the synthesis of Nb2O5-scCO2 catalyst resulted in a significantly enhanced catalytic activity compared to a reference catalyst prepared without scCO2 (Nb2O5-Ref) or to commercial Nb2O5. Importantly, the Nb2O5-scCO2 catalyst achieved an aniline conversion of 86% (stoichiometric maximum of 93% with the employed aniline-to-H2O2 ratio of 1?:?1.4) with an azoxybenzene selectivity of 92% and with 95% efficiency in H2O2 utilisation in 45 min without requiring external heating (the reaction is exothermic) and with an extremely low catalyst loading (weight ratio between the catalyst and substrate, Rc/s = 0.005). This performance largely surpasses that of any other heterogeneous catalyst previously reported for this reaction. Additionally, the Nb2O5 catalyst displayed high activity also for substituted anilines (e.g. methyl or ethyl-anilines and para-anisidine) and was reused in consecutive runs without any loss of activity. Characterisation by means of N2-physisorption, XRD, FTIR and TEM allowed the correlation of the remarkable catalytic performance of Nb2O5-scCO2 to its higher surface area and discrete nanoparticle morphology compared to the aggregated larger particles constituting the material prepared without scCO2. A catalytic test in the presence of a radical scavenger proved that the reaction follows a radical pathway.
Tao, Yehan,Singh, Bhawan,Jindal, Vanshika,Tang, Zhenchen,Pescarmona, Paolo P.
supporting information
p. 5852 - 5864
(2019/11/11)

Decarboxylative ipso Amination of Activated Benzoic Acids
In the presence of a bimetallic Pd/Cu system with 1,10-phenanthroline as the ligand and either air or N-methylmorpholine N-oxide as the oxidant, electron-deficient benzoic acids undergo oxidative decarboxylative coupling with unprotected amines. This operationally simple aniline synthesis is widely applicable with respect to the amine and gives good yields, even on multigram scale. The orthogonality of this reaction to other Pd-catalyzed cross-couplings allows the concise synthesis of multisubstituted arenes by sequential C?C, C?Cl, and C?N functionalizations. Mechanistic investigations suggest the intermediacy of a hypervalent Pd species.
Pichette Drapeau, Martin,Bahri, Janet,Lichte, Dominik,Goo?en, Lukas J.
supporting information
p. 892 - 896
(2019/01/04)

Nickel-catalysed C–O bond reduction of 2,4,6-triaryloxy-1,3,5-triazines in 2-methyltetrahydrofuran
A nickel-catalysed reduction of phenol derivatives activated by 2,4,6-trichloro-1,3,5-triazine (TCT) in ecofriendly 2-methyltetrahydrofuran (2-MeTHF) is described. The phenol-TCT derivatives were readily prepared using grinding method in short time without further purification. This catalytic system allowed the facile C–O cleavage of phenol-TCT derivatives under mild reaction conditions with high efficiency and good functional group tolerance. Gram-scale reaction was also achieved. Particularly, sequential functionalization of phenol-TCT derivatives followed by C–O bond reduction could also be realized, affording the high value-added products in moderate to good yields.
Wang, Yaoyao,Shen, Jun,Chen, Qun,Wang, Liang,He, Mingyang
p. 409 - 412
(2018/10/02)

Bismuth nitrate as a source of nitro radical in ipso-nitration of carboxylic acids
Aromatic nitro compounds are extensively used in synthetic chemistry. We disclose a new approach to obtain nitroarenes regioselectively starting from carboxylic acids under acid-free reaction conditions.
Agasti, Soumitra,Maiti, Siddhartha,Maity, Soham,Anniyappan,Talawar,Maiti, Debabrata
supporting information
p. 120 - 124
(2019/05/22)

Cucurbit[7]uril/CuCl promoting decomposition of 4-nitrobenzenediazonium in aqueous solution
4-Nitro-benzendiazonium (4-NBD) was found to form a 1:1 host-guest complex (NBD@CB) with cucurbit[7]uril (CB[7]) in aqueous solution and 4-NBD enters into the cavity of CB[7] with a binding constant of 1.28 × 105 L/mol. NBD@CB can be decomposed into a nitrobenzene/4-nitrophenol mixture in a high total yield (61% + 33%) in the presence of CuCl, unlike the decomposition of 4-NBD in the presence of either CB[7] or CuCl, or both absence, where would result in significant amounts of unknown byproducts. This work might provide an economic and effective way to obtain arenes or phenols through the substitution of diazonium salts.
Xu, Hongxing,Wang, Qiaochun
p. 337 - 339
(2018/04/06)

Transition-State Interactions in a Promiscuous Enzyme: Sulfate and Phosphate Monoester Hydrolysis by Pseudomonas aeruginosa Arylsulfatase
Pseudomonas aeruginosa arylsulfatase (PAS) hydrolyzes sulfate and, promiscuously, phosphate monoesters. Enzyme-catalyzed sulfate transfer is crucial to a wide variety of biological processes, but detailed studies of the mechanistic contributions to its catalysis are lacking. We present linear free energy relationships (LFERs) and kinetic isotope effects (KIEs) of PAS and analyses of active site mutants that suggest a key role for leaving group (LG) stabilization. In LFERs PASWT has a much less negative Br?nsted coefficient (βleaving groupobs-Enz = 0.33) than the uncatalyzed reaction (βleaving groupobs = 1.81). This situation is diminished when cationic active site groups are exchanged for alanine. The considerable degree of bond breaking during the transition state (TS) is evidenced by an 18Obridge KIE of 1.0088. LFER and KIE data for several active site mutants point to leaving group stabilization by active site K375, in cooperation with H211. 15N KIEs and the increased sensitivity to leaving group ability of the sulfatase activity in neat D2O (βleaving groupH-D = +0.06) suggest that the mechanism for S-Obridge bond fission shifts, with decreasing leaving group ability, from charge compensation via Lewis acid interactions toward direct proton donation. 18Ononbridge KIEs indicate that the TS for PAS-catalyzed sulfate monoester hydrolysis has a significantly more associative character compared to the uncatalyzed reaction, while PAS-catalyzed phosphate monoester hydrolysis does not show this shift. This difference in enzyme-catalyzed TSs appears to be the major factor favoring specificity toward sulfate over phosphate esters by this promiscuous hydrolase, since other features are either too similar (uncatalyzed TS) or inherently favor phosphate (charge).
Van Loo, Bert,Berry, Ryan,Boonyuen, Usa,Mohamed, Mark F.,Golicnik, Marko,Hengge, AlVan C.,Hollfelder, Florian
p. 1363 - 1378
(2019/03/11)

Palladium-Catalyzed Methylation of Nitroarenes with Methanol
A procedure for the synthesis of N-methyl-arylamines directly from nitroarenes using methanol as green methylating agent was developed. The key to success is the use of a specific catalyst system consisting of palladium acetate and the ligand 1-[2,6-bis(isopropyl)phenyl]-2-[tert-butyl(2-pyridinyl)phosphino]-1H-Imidazole (L1). The generality of this protocol is demonstrated in the synthesis of more than 20 N-methyl-arylamines under comparably mild conditions. Combining this novel methodology with subsequent coupling processes using the same catalyst allows for efficient diversification of aromatic nitro compounds to a broad variety of amines including drug molecules.
Wang, Lin,Neumann, Helfried,Beller, Matthias
supporting information
p. 5417 - 5421
(2019/04/04)

Method for preparing nitrobenzene from nitrogen pentoxide nitrobenzene
The invention discloses a method for preparing nitrobenzene from nitrogen pentoxide nitrobenzene, including the steps of preparing a nitromethane/nitric acid/N2O5 mixture, feeding the mixture into a reaction kettle, adding in a catalyst while controlling the temperature to be 0-10 DEG C, introducing N2 for 10-15 minutes while stirring, dropwisely adding in benzene, after that, rising the temperature to be 30-40 DEG C for reaction, and after reaction, filtering, washing, performing reduced pressure distillation to obtain nitrobenzene. Generation of a great quantity of waste acid is avoided during preparation by the method, and accordingly the method is green and environmentally friendly; besides, the method needs mild reaction conditions and has high safety in preparation.
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Paragraph 0024-0047

(2019/04/17)

Hydro/deutero deamination of arylazo sulfones under metal and (photo)catalyst-free conditions
Hydrodeaminated and monodeuterated aromatics were obtained via a visible-light driven reaction of arylazo sulfones. Deuteration occurs efficiently in deuterated media such as isopropanol-d8 or in THF-d8/water mixtures and exhibits a high tolerance to the nature and the position of the aromatic substituents.
Amin, Hawraz I.M.,Raviola, Carlotta,Amin, Ahmed A.,Mannucci, Barbara,Protti, Stefano,Fagnoni, Maurizio
(2019/06/19)

HNO3/HFIP: A Nitrating System for Arenes with Direct Observation of π-Complex Intermediates
This report describes an efficient nitrating system for the nitration of arenes at room temperature by using an equivalent of nitric acid in HFIP (1,1,1,3,3,3-hexafluoroisopropanol). The π-complex intermediate of an arene with a nitronium ion stabilized by HFIP can be directly observed by UV-vis spectra and is supported by theoretical calculations.
Lu, Le,Liu, Huixin,Hua, Ruimao
supporting information
p. 3197 - 3201
(2018/06/11)

A Predictive Model for the Decarboxylation of Silver Benzoate Complexes Relevant to Decarboxylative Coupling Reactions
Decarboxylative coupling reactions offer an attractive route to generate functionalized arenes from simple and readily available carboxylic acid coupling partners, yet they are underutilized due to limitations in the scope of carboxylic acid coupling partner. Here we report that the field effect parameter (F) has a substantial influence on the rate of decarboxylation of well-defined silver benzoate complexes. This finding provides the opportunity to surpass current substrate limitations associated with decarboxylation and to enable widespread utilization of decarboxylative coupling reactions.
Crovak, Robert A.,Hoover, Jessica M.
p. 2434 - 2437
(2018/02/28)