- Selective Nitration of Phenol
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Activated nitro derivatives of pyridinium salts have been shown to mediate in the highly selective ortho nitration of phenol in high yield.
- Pervez, Humayun,Rees, Lilias,Suckling, Colin J.
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- The catalytic properties and stability of β-galactosidases from fungi
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The catalytic activity of β-galactosidases from fungi Penicillium canescens and Aspergillus oryzae is maximum in a weakly acidic medium and does not depend on the presence of magnesium cations in the reaction medium. The enzyme from Aspergillus oryzae fungi is more active, and that from Penicillium canescens is stabler. One of stability indications is the presence of an induction period in the kinetic curves of thermal inactivation. This period disappears at 54°C for the enzyme from Aspergillus oryzae and at 59°C for the enzyme from Penicillium canescens. The temperature dependences of the effective rate constants for the inactivation of the tetrameric enzyme from Penicillium canescens show that the main reason for enzyme inactivation is the dissociation of oligomeric forms below 66°C (E act = 85 kJ/mol) and enzyme denaturation at higher temperatures (E act = 480 kJ/mol). The dissociation stage is absent for monomeric β-galactosidase from Aspergillus oryzae fungi, and the activation energy of inactivation is 450 kJ/mol over the whole temperature range studied (53-60°C). Pleiades Publishing, Ltd., 2008.
- Pilipenko,Atyaksheva,Poltorak,Chukhrai
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- Enhanced catalytic and antibacterial activities of silver nanoparticles immobilized on poly(N-vinyl pyrrolidone)-grafted graphene oxide
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Poly(N-vinyl pyrrolidone) (PNVP)-grafted graphene oxide (GO) (GO-PNVP) has been synthesized using a GO-based macro-RAFT agent prepared via click reaction of alkyne-terminated RAFT agent (S)-2-(propynyl propionate)-(o-ethyl xanthate) and azide-functionalized GO (GO-N3). FTIR, XPS, Raman, TGA and DSC studies confirmed its formation. Silver nanoparticles are then immobilized on GO-PNVP and GO via in situ reduction of silver nitrate in the presence and absence of glucose at 40 and 95 °C, respectively. FT-IR, UV-Vis, XRD, SEM and TGA studies supported the incorporation of silver (Ag) nanoparticles. Ag nanoparticles immobilized on GO-PNVP are small, spherical and narrowly distributed (homogenous, monodisperse) compared to GO. These nanocomposites are explored as catalysts for the reduction of p-nitrophenol into p-aminophenol and also as antibacterial agents towards Gram(+) S. aureus and Gram(-) E. coli bacteria. Ag nanoparticle immobilized GO-PNVP showed efficient catalytic activity and excellent reusability along with an excellent antibacterial activity. Hence, grafting of PNVP enhances the catalytic and antibacterial properties of GO.
- Singh, Shikha,Gundampati, Ravi Kumar,Mitra, Kheyanath,Ramesh,Jagannadham, Medicherla V.,Misra, Nira,Ray, Biswajit
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- Improving the properties of β-galactosidase from Aspergillus oryzae via encapsulation in aggregated silica nanoparticles
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In this study, a new immobilization method was exploited to encapsulate β-galactosidase (β-gal) from Aspergillus oryzae using aggregated core-shell silica nanoparticles as a matrix. Transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the material encapsulated β-gal. Compared to the free β-gal, the encapsulated β-gal shows a broader pH tolerance and thermal stability. Furthermore, the encapsulated β-gal shows better storage stability over 30 days. After nine cycles of hydrolytic reaction, the encapsulated β-gal still maintains 94.2% of its initial activity, which indicates that the β-gal exhibits excellent reusability after encapsulation.
- Wu, Zhuofu,Wang, Zhi,Guan, Buyuan,Wang, Xue,Zhang, Ye,Xiao, Yu,Zhi, Bo,Liu, Yunling,Li, Zhengqiang,Huo, Qisheng
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- Role of lysine ε-amino groups of β-lactoglobulin on its activating effect of Kluyveromyces lactis β-galactosidase
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Native β-lactoglobulin binds and increases the activity of Kluyveromyces lactis β-galactosidase. Construction of a three-dimensional (3D) model of β-lactoglobulin showed that lysine residues 15, 47, 69, and 138 are the most exposed ones, thus the ones more likely to interact with β-galactosidase. Molecular docking estimated the interaction energies of amino acid residues with either lactose or succinic anhydride, showing that Lys138 is the most likely to react with both. Affinity chromatography demonstrated that succinylated β-lactoglobulin diminished its ability to bind to the enzyme. Furthermore, when activity was measured in the presence of succinylated β-lactoglobulin, its activating effect was lost. Since succinylation specifically blocks Lys ε-amino groups, their loss very likely causes the disappearance of the activating effect. Results show that the activating effect of β-lactoglobulin on β-galactosidase activity is due to the interaction between both proteins and that this interaction is very likely to occur through the Lys ε-amino groups of β-lactoglobulin.
- Del Moral-Ramirez, Elizabeth,Dominguez-Ramirez, Lenin,Cruz-Guerrero, Alma E.,Rodriguez-Serrano, Gabriela M.,Garcia-Garibay, Mariano,Gomez-Ruiz, Lorena,Jimenez-Guzman, Judith
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- A novel cold-active β-D-galactosidase with transglycosylation activity from the Antarctic Arthrobacter sp. 32cB - Gene cloning, purification and characterization
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A gene encoding a novel β-d-galactosidase from the psychrotolerant Antarctic bacterium Arthrobacter sp. 32cB was isolated, cloned and expressed in Escherichia coli. The active form of recombinant β-d-galactosidase consists of two subunits with a combined molecular weight of approximately 257 kDa. The enzyme's maximum activity towards o-nitrophenyl-β-d-galactopyranoside was determined as occurring at 28 °C and pH 8.0. However, it exhibited 42% of maximum activity at 10°C and was capable of hydrolyzing both lactose and o-nitrophenyl-β-d-galactopyranoside at that temperature, with Km values of 1.52 and 16.56 mM, and kcat values 30.55 and 31.84 s-1, respectively. Two units of the enzyme hydrolyzed 90% of the lactose in 1 mL of milk at 10°C in 24 h. The transglycosylation activity of Arthrobacter sp. 32cB β-d-galactosidase was also examined. It synthesized galactooligosaccharides in a temperature range from 10 to 30°C. Moreover, it catalyzed the synthesis of heterooligosaccharides such as lactulose, galactosyl-xylose and galactosyl-arabinose, alkyl glycosides, and glycosylated salicin from lactose and the appropriate acceptor at 30°C. The properties of Arthrobacter sp. 32cB β-d-galactosidase make it a candidate for use in the industrial removal of lactose from milk and a promising tool for the glycosylation of various acceptors, especially those which are thermosensitive.
- Pawlak-Szukalska, Anna,Wanarska, Marta,Popinigis, Arkadiusz Tomasz,Kur, Józef
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- β-galactosidase from Lactobacillus plantarum WCFS1: Biochemical characterization and formation of prebiotic galacto-oligosaccharides
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Recombinant β-galactosidase from Lactobacillus plantarum WCFS1, homologously over-expressed in L. plantarum, was purified to apparent homogeneity using p-aminobenzyl 1-thio-β-D-galactopyranoside affinity chromatography and subsequently characterized. The enzyme is a heterodimer of the LacLMfamily type, consisting of a small subunit of 35 kDa and a large subunit of 72 kDa. The optimum pH for hydrolysis of its preferred substrates o-nitrophenyl-β-D-galactopyranoside (oNPG) and lactose is 7.5 and 7.0, and optimum temperature for these reactions is 55 and 60 °C, respectively. The enzyme is most stable in the pH range of 6.5-8.0. The Km, k cat and kcat/Km values for oNPG and lactose are 0.9 mM, 92 s-1, 130 mM-1 s-1 and 29 mM, 98 s-1, 3.3 mM-1 s-1, respectively. The L. plantarum β-galactosidase possesses a high transgalactosylation activity and was used for the synthesis of prebiotic galacto-oligosaccharides (GOS). The resulting GOS mixture was analyzed in detail, and major components were identified by using high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) as well as capillary electrophoresis. The maximal GOS yield was 41% (w/w) of total sugars at 85% lactose conversion (600 mM initial lactose concentration). The enzyme showed a strong preference for the formation of β-(1→6) linkages in its transgalactosylation mode, while β-(1→3)-linked products were formed to a lesser extent, comprising ～80% and 9%, respectively, of the newly formed glycosidic linkages in the oligosaccharide mixture at maximum GOS formation. The main individual products formed were β-DGalp-( 1→6)-D-Lac, accounting for 34% of total GOS, and β-D-Galp-(1→6)-D-Glc, making up 29% of total GOS.
- Iqbal, Sanaullah,Nguyen, Thu-Ha,Nguyen, Tien Thanh,Maischberger, Thomas,Haltrich, Dietmar
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- Determination of the transgalactosylation activity of Aspergillus oryzae β-galactosidase: Effect of pH, temperature, and galactose and glucose concentrations
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The catalytic potential of β-galactosidase is usually determined by its hydrolytic activity over natural or synthetic substrates. However, this method poorly predicts enzyme behavior when transglycosylation instead of hydrolysis is being performed. A system for determining the transgalactosylation activity of β-galactosidase from Aspergillus oryzae was developed, and its activity was determined under conditions for the synthesis of galacto-oligosaccharides and lactulose. Transgalactosylation activity increased with temperature up to 55 °C while the effect of pH was mild in the range from pH 2.5 to 5.5, decreasing at higher values. The effect of glucose and galactose on transgalactosylation activity was also assessed both in the reactions for the synthesis of galacto-oligosaccharides and lactulose and also in the reaction of hydrolysis of o-nitrophenyl β-d-galactopiranoside. Galactose was a competitive inhibitor and its effect was stronger in the reactions of transgalactosylation than in the reaction of hydrolysis. Glucose was a mild activator of β-galactosidase in the reaction of hydrolysis, but its mechanism of action was more complex in the reactions of transgalactosylation, having this positive effect only at low concentrations while acting as an inhibitor at high concentrations. This information is relevant to properly assess the effect of monosaccharides during the reactions of the synthesis of lactose-derived oligosaccharides, such as galacto-oligosaccharides and lactulose.
- Vera, Carlos,Guerrero, Cecilia,Illanes, Andrés
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- Immobilization of β-Galactosidases on Magnetic Nanocellulose: Textural, Morphological, Magnetic, and Catalytic Properties
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We describe a process for obtaining nanocrystalline cellulose (NC) by either acidic (H-NC) or alkaline treatment (OH-NC) of microcrystalline cellulose, which was subsequently bonded to magnetic nanoparticles (H-NC-MNP and OH-NC-MNP) and used as support for the immobilization of Aspergillus oryzae (H-NC-MNP-Ao and OH-NC-MNP-Ao) and Kluyveromyces lactis (H-NC-MNP-Kl and OH-NC-MNP-Kl) β-galactosidases. The mean size of magnetic nanocellulose particles was approximately 75 nm. All derivatives reached saturation magnetizations of 7-18 emu/g, with a coercivity of approximately 4 kOe. Derivatives could be applied in batch hydrolysis of lactose either in permeate or in cheese whey for 30× and it reached hydrolysis higher than 50%. Furthermore, using a continuous process in a column packed-bed reactor, the derivative OH-NC-MNP-Ao had capacity to hydrolyze over 50% of the lactose present in milk or whey after 24 h of reaction. Fungal β-galactosidases immobilized on magnetic nanocellulose can be applied in lactose hydrolysis using batch or continuous processes.
- Gennari, Adriano,Mobayed, Francielle H.,Da Rolt Nervis, Brenda,Benvenutti, Edilson V.,Nicolodi, Sabrina,Da Silveira, Nádya Pesce,Volpato, Giandra,Volken De Souza, Claucia F.
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- Lactose hydrolysis by β galactosidase immobilized on concanavalin A-cellulose in batch and continuous mode
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β Galactosidase from Aspergillus oryzae was immobilized on an inexpensive bioaffinity support, (concanavalin A) Con A-cellulose. The mode of interaction between Con A-cellulose and β galactosidase is shown by Fourier transform infrared spectroscopy. Con A-cellulose adsorbed and crosslinked β galactosidase preparation retained 78% of the initial activity. Soluble and immobilized β galactosidase showed the same pH-optimum at pH 4.6. The temperature-optimum was increased from 50 to 60 °C for the immobilized β galactosidase. The immobilized enzyme had higher thermal stability at 60 °C. The crosslinked adsorbed enzyme retained 80 and 70% of the original enzyme activity in the presence of 3% calcium chloride and 3% galactose, respectively. Moreover, the adsorbed crosslinked and adsorbed β galactosidase exhibited 84 and 75% enzyme activity even after their sixth repeated use, respectively. The crosslinked adsorbed enzyme retained 93% activity after 1 month storage while the native enzyme showed only 63% activity under similar incubation conditions. Immobilized β galactosidase showed higher lactose hydrolysis from solution in batch process at 60 °C as compared to its hydrolysis at 50 °C. The continuous hydrolysis of lactose was appreciably different at various flow rates. Thus, the reactor filled with crosslinked Con A-cellulose adsorbed β galactosidase could be successfully employed for the continuous hydrolysis of lactose from milk and whey.
- Ansari, Shakeel Ahmed,Husain, Qayyum
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- Selective ortho hydroxylation of nitrobenzene with molecular oxygen catalyzed by the H5PV2Mo10O40 polyoxometalate
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Nitrobenzene was regioselectively oxidized to 2-nitrophenol with oxygen in a reaction catalyzed by the H5PV2Mo10O40 polyoxometalate. The reaction was first order in oxygen and catalyst. 15N NMR showed the interaction between nitrobenzene and the polyoxometalate. Use of labeled 18O2, H218O, a competitive kinetic isotope experiment, and use of phenyl-tert-butylnitrone as a spin-trap and identification by EPR provided evidence for formation of a radical intermediate involving a selective intramolecular interaction at the ortho position due to formation of a H5PV2Mo10O40-nitrobenzene complex. Copyright
- Khenkin, Alexander M.,Weiner, Lev,Neumann, Ronny
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- Novel grafted agar disks for the covalent immobilization of β-D-galactosidase
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Novel grafted agar disks were prepared for the covalent immobilization of β-D-galactosidase (β-gal). The agar disks were activated through reacting with ethylenediamine or different molecular weights of Polyethyleneimine (PEI), followed by glutaraldehyde (GA). The modification of the agar gel and the binding of the enzyme were verified by Fourier Transform Infrared (FTIR) and elemental analysis. Moreover, the agar's activation process was optimized, and the amount of immobilized enzyme increased 3.44 folds, from 38.1 to 131.2 U/g gel, during the course of the optimization process. The immobilization of β-gal onto the activated agar disks caused its optimum temperature to increase from 45°C to 45-55°C. The optimum pH of the enzyme was also shifted towards the acidic side (3.6-4.6) after its immobilization. Additionally, the Michaelis-Menten constant (Km) increased for the immobilized β-gal as compared to its free counterpart whereas the maximum reaction rate (Vmax) decreased. The immobilized enzyme was also shown to retain 92.99% of its initial activity after being used for 15 consecutive times.
- I. Wahba, Marwa,E. Hassan, Mohamed
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- Mechanism of the dimerization of enzymes upon adsorption on silicate adsorbents using the example of lysozyme and β-galactosidase
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It is shown by the kinetic analysis of lysozyme and β-galactosidase adsorption on silochrome, silica gel, and mesoporous silica that the adsorption follows a two-stage scheme, including reversible pre-adsorption and the irreversible binding of dimmers. The corresponding rate constants of adsorption, desorption, and dimerization were calculated. It was found that β-galoctosidase adsorbed on silica gel and mesoporous silica retained 20% of its activity, while β-galoctosidase adsorbed on silochrome retained more than 30% of its activity.
- Chukhrai,Pilipenko,Ovsyannikov,Atyaksheva,Knyazeva,Ivanova
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- Selective nitration of phenol to: O -nitrophenol in the presence of metal-free reduced graphene oxide at room temperature
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We report here a reduced graphene oxide (RGO)-catalyzed ultra-efficient, highly selective and low temperature synthesis of o-nitrophenol using phenol and nitric acid in an equimolar ratio. The effects of various parameters such as concentration of reactants, type of catalyst, weight of the catalyst, solvent, temperature and time of reaction on the catalytic reaction have been explored. The optimum conditions for the catalytic nitration reaction have been observed using a 1 : 1 molar ratio of nitric acid to phenol in the presence of 50 mg RGO in dichloroethane at room temperature for 3 h with a turn over frequency (TOF) of 10.96 × 1017 molecules g-1 s-1 and a reaction rate of 12.17 × 1014 molecules mL-1 s-1. In order to explore the decrease in efficiency of the catalyst during reuse, both the parent catalyst and used catalyst have been characterized by XRD, Raman, SEM, EDX, BET and FT-IR. The large surface area of RGO promotes the catalytic activity of aromatic compounds via smooth and high conversion of products with fine regioselectivity. So this protocol opens up a new avenue for the selective synthesis of o-nitrophenol using reduced graphene oxide at room temperature. This journal is
- Kumari, Archana,Mitra, Kheyanath,Mondal, Sourov,Ray, Biswajit,Sen Gupta, Susanta K.,Singh, Jaydeep,Singh, Rajshree,Singh, Shikha,Vishwakarma, Sambhav
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- Characterization of a heterodimeric GH2 β-galactosidase from lactobacillus sakei Lb790 and formation of prebiotic galacto-oligosaccharides
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The lacLM genes from Lactobacillus sakei Lb790, encoding a heterodimeric β-galactosidase that belongs to glycoside hydrolase family GH2, were cloned and heterologously expressed in Escherichia coli. Subsequently, the recombinant β-galactosidase LacLM was purified to apparent homogeneity and characterized. The enzyme is a β-galactosidase with narrow substrate specificity because o-nitrophenyl-β-d-galactopyranoside (oNPG) was efficiently hydrolyzed, whereas various structurally related oNP analogues were not. The Km and kcat values for oNPG and lactose were 0.6 mM and 180 s-1 and 20 mM and 43 s-1, respectively. The enzyme is inhibited competitively by its two end-products d-galactose and d-glucose (Ki values of 180 and 475 mM, respectively). As judged by the ratio of the inhibition constant to the Michaelis constant, K i/Km, this inhibition is only very moderate and much less pronounced than for other microbial β-galactosidases. β-Galactosidase from L. sakei possesses high transgalactosylation activity and was used for the synthesis of galacto-oligosaccharides (GalOS), employing lactose at a concentration of 215 g/L. The maximum GalOS yield was 41% (w/w) of total sugars at 77% lactose conversion and contained mainly non-lactose disaccharides, trisaccharides, and tetrasaccharides with approximately 38, 57, and 5% of total GalOS formed, respectively. The enzyme showed a strong preference for the formation of β-(1→6)-linked transgalactosylation products, whereas β-(1→3)-linked compounds were formed to a lesser extent and β-(1→4)-linked reaction products could not be detected.
- Iqbal, Sanaullah,Nguyen, Thu-Ha,Nguyen, Hoang Anh,Nguyen, Tien Thanh,Maischberger, Thomas,Kittl, Roman,Haltrich, Dietmar
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- Research on the decomposition kinetics and thermal hazards of aniline diazonium salt
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Diazotization reaction, strong exothermic characteristics and thermal instability of diazonium salts make the production process high risk. To research thermal hazards of aniline diazonium salt, dynamic experiments are carried out by the differential scanning calorimeter (DSC) to obtain thermodynamic parameters. Moreover, the kinetic parameters are analyzed by Advanced Kinetics and Technology Solutions (AKTS) software. Finally, the GC-MS and UV spectrum are used to further study the decomposition mechanism of the aniline diazonium salt. The results indicate that aniline diazonium salt is very easy to decompose. When the heating rate is 2 K/min, the onset decomposition temperature is only 27.21 ℃ (Tonset). The apparent activation energy of the decomposition process calculated by Friedman and Ozawa methods are respectively 98-85 kJ/mol and 110-100 kJ/mol. Under the ideal adiabatic conditions (φ = 1), the initial temperatures of TMRad for 24 h is only 6.2 ℃ (TD24), which is predicted by the AKTS software. The decomposition process of aniline diazonium salt is inconsistent with a single reaction mechanism.
- Du, Lei,Wang, Ben,Xie, Chuanxin,Yuan, Yucan
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- Structural insights in galectin-1-glycan recognition: Relevance of the glycosidic linkage and the N-acetylation pattern of sugar moieties
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Galectins, soluble lectins widely expressed intra- and extracellularly in different cell types, play major roles in deciphering the cellular glycocode. Galectin-1 (Gal-1), a prototype member of this family, presents a carbohydrate recognition domain (CRD) with specific affinity for β-galactosides such as N-acetyllactosamine (β-D-Galp-(1 → 4)-D-GlcpNAc), and mediate numerous physiological and pathological processes. In this work, Gal-1 binding affinity for β-(1 → 6) galactosides, including β-D-Galp-(1 → 6)-β-D-GlcpNAc-(1 → 4)-D-GlcpNAc was evaluated, and their performance was compared to that of β-(1 → 4) and β-(1 → 3) galactosides. To this end, the trisaccharide β-D-Galp-(1 → 6)-β-D-GlcpNAc-(1 → 4)-D-GlcpNAc was enzymatically synthesized, purified and structurally characterized. To evaluate the affinity of Gal-1 for the galactosides, competitive solid phase assays (SPA) and isothermal titration calorimetry (ITC) studies were carried out. The experimental dissociation constants and binding energies obtained were compared to those calculated by molecular docking. These analyses evidenced the critical role of the glycosidic linkage between the terminal galactopyranoside residue and the adjacent monosaccharide, as galactosides bearing β-(1 → 6) glycosidic linkages showed dissociation constants six- and seven-fold higher than those involving β-(1 → 4) and β-(1 → 3) linkages, respectively. Moreover, docking experiments revealed the presence of hydrogen bond interactions between the N-acetyl group of the glucosaminopyranose moiety of the evaluated galactosides and specific amino acid residues of Gal-1, relevant for galectin-glycan affinity. Noticeably, the binding free energies (ΔGbindcalc) derived from the molecular docking were in good agreement with experimental values determined by ITC measurements (ΔGbindexp), evidencing a good correlation between theoretical and experimental approaches, which validates the in silico simulations and constitutes an important tool for the rational design of future optimized ligands.
- Cagnoni, Alejandro J.,Fontana, Carolina,Giacomini, Cecilia,Irazoqui, Gabriela,Mari?o, Karina V.,Porciúncula-González, Cecilia,Saenz-Méndez, Patricia
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- Radical-anion coupling through reagent design: hydroxylation of aryl halides
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The design and development of an oxime-based hydroxylation reagent, which can chemoselectively convert aryl halides (X = F, Cl, Br, I) into phenols under operationally simple, transition-metal-free conditions is described. Key to the success of this approach was the identification of a reducing oxime anion which can interact and couple with open-shell aryl radicals. Experimental and computational studies support the proposed radical-nucleophilic substitution chain mechanism.
- Chechik, Victor,Greener, Andrew J.,James, Michael J.,Oca?a, Ivan,Owens-Ward, Will,Smith, George,Ubysz, Patrycja,Whitwood, Adrian C.
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p. 14641 - 14646
(2021/11/17)
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- Light-Controlled Tyrosine Nitration of Proteins
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Tyrosine nitration of proteins is one of the most important oxidative post-translational modifications in vivo. A major obstacle for its biochemical and physiological studies is the lack of efficient and chemoselective protein tyrosine nitration reagents. Herein, we report a generalizable strategy for light-controlled protein tyrosine nitration by employing biocompatible dinitroimidazole reagents. Upon 390 nm irradiation, dinitroimidazoles efficiently convert tyrosine residues into 3-nitrotyrosine residues in peptides and proteins with fast kinetics and high chemoselectivity under neutral aqueous buffer conditions. The incorporation of 3-nitrotyrosine residues enhances the thermostability of lasso peptide natural products and endows murine tumor necrosis factor-α with strong immunogenicity to break self-tolerance. The light-controlled time resolution of this method allows the investigation of the impact of tyrosine nitration on the self-assembly behavior of α-synuclein.
- Long, Tengfang,Liu, Lei,Tao, Youqi,Zhang, Wanli,Quan, Jiale,Zheng, Jie,Hegemann, Julian D.,Uesugi, Motonari,Yao, Wenbing,Tian, Hong,Wang, Huan
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supporting information
p. 13414 - 13422
(2021/05/12)
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- Photocatalytic synthesis of phenols mediated by visible light using KI as catalyst
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A transition-metal-free hydroxylation of iodoarenes to afford substituted phenols is described. The reaction is promoted by KI under white LED light irradiation and uses atmospheric oxygen as oxidant. By the use of triethylamine as base and solvent, the corresponding phenols are obtained in moderate to good yields. Mechanistic studies suggest that KI and catalysis synergistically promote the cleavage of C-I bond to form free aryl radicals.
- Huiqin, Wei,Wu, Mei
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supporting information
(2021/11/30)
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- Electrochemical-induced hydroxylation of aryl halides in the presence of Et3N in water
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A thorough study of mild and environmentally friendly electrochemical-induced hydroxylation of aryl halides without a catalyst is presented. The best protocol consists of hydroxylation of different aryl iodides and aryl bromides by water solution in the presence of Et3N under air, affording the target phenols in good isolated yields. Moreover, aryl chlorides were successfully employed as substrates. This methodology also provides a direct pathway for the formation of deoxyphomalone, which displayed a significant anti-proliferation effect.
- Ke, Fang,Lin, Chen,Lin, Mei,Long, Hua,Wu, Mei,Yang, Li,Zhuang, Qinglong
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supporting information
p. 6417 - 6421
(2021/08/03)
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- Highly recyclable Ti0.97Ni0.03O1.97catalyst coated on cordierite monolith for efficient transformation of arylboronic acids to phenols and reduction of 4-nitrophenol
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A stable Ni2+substituted TiO2catalyst (Ti0.97Ni0.03O1.97) has been synthesized by a solution combustion method with an average crystallite size of 7.5 nm. Ti1?xNixO2?x(x= 0.01-0.06) crystallizes in the TiO2anatase structure with Ni2+substituted in Ti4+ion sites and Ni taking a nearly square planar geometry. This catalyst is found to be highly active in the transformation of diverse arylboronic acids to the corresponding phenols. The catalyst coated cordierite monolith can even be recycled for up to 20 cycles with a cumulative TOF of 1.8 × 105h?1. In scale-up reactions, various phenols are synthesized by employing a single cordierite monolith. It also shows high performance in the reduction of 4-nitrophenol.
- Hegde, M. S.,Prasanna,Usha, K. M.
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supporting information
p. 14223 - 14234
(2021/10/25)
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- An efficient Ti0.95Cu0.05O1.95 catalyst for ipso – hydroxylation of arylboronic acid and reduction of 4-nitrophenol
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A stable, active and selective Ti0.95Cu0.05O1.95 catalyst, crystallized in anatase TiO2 structure with 5% Cu2+ ions substituted for Ti4+ ions with 5% oxide ion vacancy has been synthesized by solution combustion method. The catalyst was coated over a cordierite monolith (Mg2Al4Si5O18) by solution combustion method. By the first principle density functional theory (DFT) calculations, 48 atoms bulk structure has been optimized and density of states (DOS) has been calculated. Ti – O bond distribution in Ti0.95Cu0.05O1.95 has been compared with pure TiO2. Bond distribution analysis has shown longer Cu – O and Ti – O bonds compared to those in CuO and TiO2 creating Cu2+ and oxide ion vacancy as electrophilic and nucleophilic active sites, respectively. This catalyst was found to be very active for ipso – hydroxylation of arylboronic acid and 4-nitrophenol reduction reactions at room temperature. Catalyst coated cordierite monolith was used in the recycling process of the reaction for 20 cycles and cumulative turnover frequency was found to be 184,840 h?1. Ti0.95Cu0.05O1.95 catalyst coated on cordierite monolith enhanced the rate of the reaction compared to powder catalyst and made the handling and recycling of the catalyst very easy. Graphic abstract: [Figure not available: see fulltext.]
- Bhat, Shrikanth K,Dasappa, Jagadeesh Prasad,Hegde, M. S.,Prasanna
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- Photoinduced Iron-Catalyzed ipso-Nitration of Aryl Halides via Single-Electron Transfer
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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
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p. 9561 - 9568
(2021/08/06)
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- Method for synthesizing phenol or derivative thereof in aqueous phase by photocatalytic one-pot method
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The invention discloses a method for synthesizing phenol or a derivative thereof in an aqueous phase by a photocatalytic one-pot method. The method comprises the following steps: by taking a compoundaryl halide shown in formula (I) as a raw material and water as a solvent, adding a catalyst and an auxiliary agent, and carrying out reacting under the conditions of alkali and visible light to obtain the phenol or the derivative (II) thereof. Compared with the prior art, the method is applicable to a large number of functional groups, high in yield, few in byproducts, simple and safe to operate,low in cost and environmentally friendly, wherein R is selected from substituted or non-substituted phenyl, pyridyl, quinolyl or pyrimidinyl; X is selected from halogen; the substituted phenyl is substituted by C1-C4 alkyl, C1-C4 alkoxy, hydroxyl, halogen, cyano, aldehyde group, nitro, amino, acetyl or carboxyl; and the substituted pyridyl, quinolyl or pyrimidinyl is pyridyl, quinolyl or pyrimidinyl substituted by C1-C4 alkyl.
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Paragraph 0032-0033; 0062-0063; 0085-0106
(2020/12/08)
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- Copper and L-(?)-quebrachitol catalyzed hydroxylation and amination of aryl halides under air
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L-(?)-Quebrachitol, a natural product obtained from waste water of the rubber industry, was utilized as an efficient ligand for the copper-catalyzed hydroxylation and amination of aryl halides to selectively give phenols and aryl amines in water or 95percent ethanol. In addition, the hydroxylation of 2-chloro-4-hydroxybenzoic acid was validated on a 100-g scale under air.
- Bao, Xuefei,Chen, Guoliang,Dong, Jinhua,Du, Fangyu,Li, Hui,Liang, Xinjie,Wu, Ying,Zhang, Yongsheng
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supporting information
(2020/08/03)
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- Benzene Hydroxylation by Bioinspired Copper(II) Complexes: Coordination Geometry versus Reactivity
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A series of bioinspired copper(II) complexes of N4-tripodal and sterically crowded diazepane-based ligands have been investigated as catalysts for functionalization of the aromatic C-H bond. The tripodal-ligand-based complexes exhibited distorted trigonal-bipyramidal (TBP) geometry (τ, 0.70) around the copper(II) center; however, diazepane-ligand-based complexes adopted square-pyramidal (SP) geometry (τ, 0.037). The Cu-NPy bonds (2.003-2.096 ?) are almost identical and shorter than Cu-Namine bonds (2.01-2.148 ?). Also, their Cu-O (Cu-Owater, 1.988 ? Cu-Otriflate, 2.33 ?) bond distances are slightly varied. All of the complexes exhibited Cu2+ → Cu+ redox couples in acetonitrile, where the redox potentials of TBP-based complexes (-0.251 to -0.383 V) are higher than those of SP-based complexes (-0.450 to -0.527 V). The d-d bands around 582-757 nm and axial patterns of electron paramagnetic resonance spectra [g∥, 2.200-2.251; A∥, (146-166) × 10-4 cm-1] of the complexes suggest the existence of five-coordination geometry. The bonding parameters showed K∥ > K∥ for all complexes, corresponding to out-of-plane πbonding. The complexes catalyzed direct hydroxylation of benzene using 30% H2O2 and afforded phenol exclusively. The complexes with TBP geometry exhibited the highest amount of phenol formation (37%) with selectivity (98%) superior to that of diazepane-based complexes (29%), which preferred to adopt SP-based geometry. Hydroxylation of benzene likely proceeded via a CuII-OOH key intermediate, and its formation has been established by electrospray ionization mass spectrometry, vibrational, and electronic spectra. Their formation constants have been calculated as (2.54-11.85) × 10-2 s-1 from the appearance of an O (π?σ) → Cu ligand-to-metal charge-transfer transition around 370-390 nm. The kinetic isotope effect (KIE) experiments showed values of 0.97-1.12 for all complexes, which further supports the crucial role of Cu-OOH in catalysis. The 18O-labeling studies using H218O2 showed a 92% incorporation of 18O into phenol, which confirms H2O2 as the key oxygen supplier. Overall, the coordination geometry of the complexes strongly influenced the catalytic efficiencies. The geometry of one of the CuII-OOH intermediates has been optimized by the density functional theory method, and its calculated electronic and vibrational spectra are almost similar to the experimentally observed values.
- Anandababu, Karunanithi,Mayilmurugan, Ramasamy,Muthuramalingam, Sethuraman,Velusamy, Marappan
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p. 5918 - 5928
(2020/04/20)
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- OcUGT1-catalyzing glycodiversification of steroids through glucosylation and transglucosylation actions
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Steroidal glycosides are important sources of innovative drugs. The increased diversification of steroidal glycosides will expand the probability of discovering active molecules. It is an efficient approach to diversify steroidal glycosides by using steroidal glycosyltransferases. OcUGT1, a uridine diphosphate-d-glucose (UDP-Glc)-dependent glycosyltransferase from Ornithogalum caudatum, is a multifunctional enzyme, and its glycodiversification potential towards steroids has never been fully explored. Herein, the glycodiversification capability of OcUGT1 towards 25 steroids through glucosylation and transglucosylation reactions were explored. Firstly, each of 25 compounds was glucosylated with UDP-Glc. Under the action of OcUGT1, five steroids (testosterone, deoxycorticosterone, hydrocortisone, estradiol, and 4-androstenediol) were glucosylated to form corresponding mono-glucosides and biosides. Next, OcUGT1-mediated transglucosylation activity of these compounds with another sugar donor ortho-nitrophenyl-β-d-glucopyranoside (oNPGlc) was investigated. Results revealed that the same five steroids could be glucosylated to generate mono-glucosides and biosides by OcUGT1 through transglucosylation reactions. These data indicated that OcUGT1-assisted glycodiversification of steroids could be achieved through glucosylation and transglucosylation reactions. These results provide a way to diversify steroidal glycosides, which lays the foundation for the increase of the probability of obtaining active lead compounds.
- Xu, Yan-Li,Kong, Jian-Qiang
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- Nickel-catalyzed oxidative hydroxylation of arylboronic acid: Ni(HBTC)BPY MOF as an efficient and ligand-free catalyst to access phenolic motifs
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A straightforward and mild oxidative ipso-hydroxylation of arylboronic acids has been achieved using a simple and non-noble metal, nickel-based reusable heterogeneous catalyst Ni(HBTC)BPY MOF (HBTC = benzene-1,3,5-tricarboxylate, BPY = 4,4′-bipyridine) in the presence of benign hydrogen peroxide as an oxidant under ambient reaction condition. The Ni(HBTC)BPY MOF exhibits excellent catalytic activity towards the formation of phenols from diverse arylboronic acids within short time and can be reused up to five times without any notable loss in its activity as well as shown high functional group tolerance even in the presence of sensitive functionalities and useful to achieve hydroxyl group in heterocycles.
- Latha, Ganesapandian,Devarajan, Nainamalai,Karthik, Murugan,Suresh, Palaniswamy
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- Copper nanoparticles supported on highly nitrogen-rich covalent organic polymers as heterogeneous catalysts for the ipso -hydroxylation of phenyl boronic acid to phenol
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This work describes a simple procedure for the synthesis of highly nitrogen-rich covalent organic polymers using commercially available starting materials like melamine and cyanuric chloride as a solid heterogeneous catalyst Cu/TCOP under solvothermal conditions. The structural properties of the as-synthesized solid heterogeneous catalyst were determined by X-ray diffraction (XRD), diffuse reflectance spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), 13C-CP MAS nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy. The catalytic activity of Cu/TCOP was investigated by focusing on the oxidation of phenylboronic acid under atmospheric conditions in an aqueous medium, achieving a very good yield up to 99%. The reaction performance was evaluated considering the effect of various parameters, such as the amount of the catalyst, reaction time, temperature, and the amount of the base and solvent. The Cu/TCOP catalyst is completely recoverable in a facile manner from the reaction mixture and the efficiency of the copper nanocatalyst can be recovered after five cycles.
- Sadhasivam, Velu,Harikrishnan, Muniyasamy,Elamathi, Ganesan,Balasaravanan, Rajendran,Murugesan, Sepperumal,Siva, Ayyanar
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supporting information
p. 6222 - 6231
(2020/05/13)
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- N-Nitroheterocycles: Bench-Stable Organic Reagents for Catalytic Ipso-Nitration of Aryl- And Heteroarylboronic Acids
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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
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supporting information
(2020/03/30)
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- Synthesis of Medium-Ring-Sized Benzolactams by Using Strong Electrophiles and Quantitative Evaluation of Ring-Size Dependency of the Cyclization Reaction Rate
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Benzolactams with medium-sized rings were synthesized via the electrophilic aromatic substitution reaction of carbamoyl cations (R1R2N+═C═O) in good to high yields without dilution. These reactions were utilized to quantitatively examine the extent of retardation of medium-sized ring formation, compared to five- or six-membered ring formation. The order of reaction rates of formation of cyclic benzolactams is six- > five- > seven- > eight- > nine-membered ring at 25 °C. The present reaction provides a route to eight- A nd nine-membered benzolactams.
- Kurouchi, Hiroaki,Ohwada, Tomohiko
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supporting information
p. 876 - 901
(2019/12/30)
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- Activity and specificity studies of the new thermostable esterase EstDZ2
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In this paper, we study the activity and specificity of EstDZ2, a new thermostable carboxyl esterase of unknown function, which was isolated from a metagenome library from a Russian hot spring. The biocatalytic reaction employing EstDZ2 proved to be an efficient method for the hydrolysis of aryl p-, o- or m-substituted esters of butyric acid and esters of secondary alcohols. Docking studies revealed structural features of the enzyme that led to activity differences among the different substrates.
- Myrtollari, Kamela,Katsoulakis, Nikolaos,Zarafeta, Dimitra,Pavlidis, Ioannis V.,Skretas, Georgios,Smonou, Ioulia
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supporting information
(2020/09/16)
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- Immobilization of β-Galactosidases on Magnetic Nanocellulose: Textural, Morphological, Magnetic, and Catalytic Properties
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We describe a process for obtaining nanocrystalline cellulose (NC) by either acidic (H-NC) or alkaline treatment (OH-NC) of microcrystalline cellulose, which was subsequently bonded to magnetic nanoparticles (H-NC-MNP and OH-NC-MNP) and used as support for the immobilization of Aspergillus oryzae (H-NC-MNP-Ao and OH-NC-MNP-Ao) and Kluyveromyces lactis (H-NC-MNP-Kl and OH-NC-MNP-Kl) β-galactosidases. The mean size of magnetic nanocellulose particles was approximately 75 nm. All derivatives reached saturation magnetizations of 7-18 emu/g, with a coercivity of approximately 4 kOe. Derivatives could be applied in batch hydrolysis of lactose either in permeate or in cheese whey for 30× and it reached hydrolysis higher than 50%. Furthermore, using a continuous process in a column packed-bed reactor, the derivative OH-NC-MNP-Ao had capacity to hydrolyze over 50% of the lactose present in milk or whey after 24 h of reaction. Fungal β-galactosidases immobilized on magnetic nanocellulose can be applied in lactose hydrolysis using batch or continuous processes.
- Gennari, Adriano,Mobayed, Francielle H.,Da Rolt Nervis, Brenda,Benvenutti, Edilson V.,Nicolodi, Sabrina,Da Silveira, Nádya Pesce,Volpato, Giandra,Volken De Souza, Claucia F.
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p. 2315 - 2326
(2019/06/17)
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- 3-(Ethoxycarbonyl)-1-(5-methyl-5-(nitrosooxy)hexyl)pyridin-1-ium cation: A green alternative to tert-butyl nitrite for synthesis of nitro-group-containing arenes and drugs at room temperature
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Due to their remarkable properties, task-specific ionic liquids have turned out to be progressively popular over the last few years in the field of green organic synthesis. Herein, for the first time, we report that a new task-specific nitrite-based ionic liquid such as 3-(ethoxycarbonyl)-1-(5-methyl-5-(nitrosooxy)hexyl)pyridin-1-ium bis(trifluoromethanesulfonyl)imides (TS-N-IL) derived from biodegradable ethyl nicotinate indeed acted as an efficient and eco-friendly reagent for the synthesis of highly valuable nitroaromatic compounds and drugs including nitroxynil, tolcapone, niclofolan, flutamide, niclosamide and nitrazepam. The bridging of an ionic liquid with nitrite group not only increases the yield and rate of direct C[sbnd]N bond formation reaction but also allows easy product separation and recyclability of a byproduct. Nonvolatile nature, easy synthesis, merely stoichiometric need and mildness are a portion of the extra focal points of TS-N-IL while contrasted with tert-butyl nitrite an outstanding and highly-flammable reagent utilized largely in organic synthesis.
- Chaudhary, Renu,Natarajan, Palani,Rani, Neetu,Sakshi,Venugopalan, Paloth
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supporting information
(2019/12/30)
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- Iodine(III)-Catalyzed Electrophilic Nitration of Phenols via Non-Br?nsted Acidic NO2+ Generation
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The first catalytic procedure for the electrophilic nitration of phenols was developed using iodosylbenzene as an organocatalyst based on iodine(III) and aluminum nitrate as a nitro group source. This atom-economic protocol occurs under mild, non-Br?nsted acidic and open-flask reaction conditions with a broad functional-group tolerance including several heterocycles. Density functional theory (DFT) calculations at the (SMD:MeCN)Mo8-HX/(LANLo8+f,6-311+G) level indicated that the reaction proceeds through a cationic pathway that efficiently generates the NO2+ ion, which is the nitrating species under neutral conditions.
- Juárez-Ornelas, Kevin A.,Jiménez-Halla, J. Oscar C.,Kato, Terumasa,Solorio-Alvarado, César R.,Maruoka, Keiji
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supporting information
p. 1315 - 1319
(2019/03/07)
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- Preparation method of substituted nitrobenzene compound
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The invention discloses a preparation method of a substituted nitrobenzene compound. The method comprises the following steps: carrying out a decarboxylation reaction as shown below on a compound II under the action of alkali in a solvent at the temperature of 150 to 250 DEG C to obtain a compound I; the alkali is one or more of carbonates and bicarbonates of alkali metals. Compared with some metal-catalyzed decarboxylation methods, the preparation method of the substituted nitrobenzene compound has the advantages of simple operation, low production cost, convenient post-treatment and high yield, and more application values in industrial production.
- -
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Paragraph 0042-0045
(2019/03/29)
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- Benzimidazolium-based high temperature ionic liquid-in-oil microemulsion for regioselective nitration reaction
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Owing to the fascinating applications of ionic liquids (ILs) based non-aqueous microemulsions (MEs) in the field of chemical reactions due to their high thermal stability compared to that of aqueous MEs and requirement of water-free environment, we design
- Kar, Barnali,Ghosh, Prasanjit,Kundu, Kaushik,Bardhan, Soumik,Paul, Bidyut K.,Das, Sajal
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p. 122 - 130
(2018/07/25)
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- Silica-supported perchloric acid and potassium bisulfate as reusable green catalysts for nitration of aromatics under solvent-free microwave conditions
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Silica-supported perchloric acid and bisulfate (SiO2/HClO4 and SiO2/KHSO4) have been developed as reusable green catalysts for nitration of aromatic compounds using NaNO2 in acetonitrile medium under conventional and solvent-free microwave conditions. The reaction times under microwave irradiation are significantly shorter than conventional method even though the yields obtained in microwave-assisted reactions are comparable with those obtained under reflux conditions.
- Kumar, M. Satish,Sriram, Y. Hemanth,Venkateswarlu,Rajanna,Sudhakar, M. Sai,Venkanna, Purugula,Saiprakash
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supporting information
p. 59 - 67
(2017/12/26)
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- Visible-Light-Mediated Nitration of Protected Anilines
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The photocatalytic nitration of protected anilines proceeds with riboflavin tetraacetate as an organic photoredox catalyst. Sodium nitrite serves as the NO2 source in this visible-light-driven room temperature reaction. Various nitroanilines are obtained in moderate to good yields without the addition of acid or stoichiometric oxidation agents. The catalytic cycle is closed by aerial oxygen as the terminal oxidant.
- Düsel, Simon J. S.,K?nig, Burkhard
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supporting information
p. 2802 - 2807
(2018/03/09)
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- Sodium perborate/NaNO2/KHSO4-triggered synthesis and kinetics of nitration of aromatic compounds
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Sodium perborate (SPB) was used as efficient green catalyst for NaNO2/KHSO4-mediated nitration of aromatic compounds in aqueous acetonitrile medium. Synthesis of nitroaromatic compounds was achieved under both conventional and solvent-free microwave conditions. Reaction times were comparatively shorter in the microwave-assisted than conventional reaction. The reaction kinetics for nitration of phenols in aqueous bisulfate and acetonitrile medium indicated first-order dependence on [Phenol], [NaNO2], and [SPB]. Reaction rates accelerated with introduction of electron-donating groups but retarded with electron-withdrawing groups. Kinetic results did not fit well quantitatively with Hammett’s equation. Observed deviations from linearity were addressed in terms of exalted Hammett’s constants (σˉ or σeff), para resonance interaction energy (ΔΔGp) parameter, and Yukawa–Tsuno parameter (r). This term provides a measure of the extent of resonance stabilization for a reactive structure that builds up charge (positive) in its transition state. The observed negative entropy of activation (?ΔS#) suggests greater solvation and/or cyclic transition state before yielding products.
- Rajanna,Muppidi, Suresh,Pasnoori, Srinivas,Saiprakash
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p. 6023 - 6038
(2018/09/21)
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- Application of metallide/palladium compound catalytic reduction system in reaction of removing allyl groups and deuteration reaction
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The invention discloses application of a metallide/palladium compound catalytic reduction system in reaction of removing allyl groups of a compound containing the allyl groups and deuteration reaction. The reaction comprises the following steps: under protection of nitrogen gas, suspending a palladium compound and a metallide in a solvent, stirring for 5 minutes, adding the compound containing theallyl groups, reacting for 0.5-36 hours at the temperature of minus 50-120 DEG C, adding ice water to stop reaction, regulating a pH value to 3.5 by using diluted hydrochloric acid, and carrying outsolvent extraction, drying by steaming and column-chromatography purification on reaction liquid to finish the reaction.
- -
-
Paragraph 0038
(2018/07/30)
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- Pd-Catalyzed debenzylation and deallylation of ethers and esters with sodium hydride
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Herein we demonstrate simply that the addition of Pd(OAc)2 as a promotor switches the reactivity of a commonly used base NaH to a nucleophilic reductant. The reactivity is engineered into a palladium-catalyzed reductive debenzylation and deallylation of aryl ethers and esters. This operationally simple, mild protocol displays a broad substrate scope and a broad spectrum of functional group tolerance (>50 examples) and high chemoselectivity toward aryl ethers over aliphatic structures. Moreover, the dual reactivity of NaH as a base and a reductant is demonstrated in efficient synthetic elaboration.
- Mao, Yujian,Liu, Ye,Hu, Yanwei,Wang, Liang,Zhang, Shilei,Wang, Wei
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p. 3016 - 3020
(2018/04/14)
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- Sc3+ (or HClO4) Activation of a Nonheme FeIII-OOH Intermediate for the Rapid Hydroxylation of Cyclohexane and Benzene
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[Fe(β-BPMCN)(CH3CN)2]2+ (1, BPMCN = N,N′-bis(pyridyl-2-methyl)-N,N′-dimethyl-trans-1,2-diaminocyclo-hexane) is a relatively poor catalyst for cyclohexane oxidation by H2O2 and cannot perform benzene hydroxylation. However, addition of Sc3+ activates the 1/H2O2 reaction mixture to be able to hydroxylate cyclohexane and benzene within seconds at -40 °C. A metastable S = 1/2 FeIII-(η1-OOH) intermediate 2 is trapped at -40 °C, which undergoes rapid decay upon addition of Sc3+ at rates independent of [substrate] but linearly dependent on [Sc3+]. HClO4 elicits comparable reactivity as Sc3+ at the same concentration. We thus postulate that these additives both facilitate O-O bond heterolysis of 2 to form a common highly electrophilic FeVO oxidant that is comparably reactive to the fastest nonheme high-valent iron-oxo oxidants found to date.
- Kal, Subhasree,Draksharapu, Apparao,Que, Lawrence
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supporting information
p. 5798 - 5804
(2018/05/09)
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- Deprotection of durable benzenesulfonyl protection for phenols — efficient synthesis of polyphenols
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A robust protection method for phenol was demonstrated by the use of durable benzenesulfonyl group, which survives various harsh reaction conditions using Grignard reagent, organolithium reagent, metal alkoxide, phosgene, mineral, and Lewis acids. A facile deprotection condition utilizing pulverized KOH (5 equiv) and t-BuOH (10 equiv) in hot toluene makes this protocol as a practical method, which can be applied to the multistep synthesis of biologically and medicinally important polyphenol compounds.
- Alam, Mohammad Shariful,Koo, Sangho
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supporting information
p. 247 - 254
(2018/01/08)
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- Efficient dealkylation of aryl alkyl ethers catalyzed by Cu2O
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An efficient protocol for dealkylation of aryl alkyl ethers under the catalysis of inexpensive and easily reusable Cu2O has been described. The phenol products were obtained in high yields, and a range of functional groups were well tolerated. The choice of solvent is critical to the catalysis, and CH3OH proved to be the optimal choice. Mechanistic investigations showed that this reaction possibly proceeds via a single-electron transfer (SET) process.
- Liu, Lingxian,Li, Zengguang,Chen, Changjun,Li, Huanrong,Xu, Lijin,Yu, Zhiyong
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supporting information
p. 2447 - 2453
(2018/04/11)
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- Oxidation of Aniline to Nitrobenzene Catalysed by 1-Butyl-3-methyl imidazolium phosphotungstate Hybrid Material Using m-chloroperbenzoic Acid as an Oxidant
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Abstract: Keggin ion based hybrid materials, [BmIm]3[PW12O40], [TBA]3PW12O40 and [BuPy]3PW12O40, were prepared by proton exchange with organic cations, 1-butyl-3-methyl imidazolium ion, tetrabutylammonium ion and butylpyridinium ion, respectively. The formation of hybrid materials was confirmed by FTIR, PXRD, SEM, TG-DTA, DSC analysis. These hybrid compounds are active for oxidation of aniline using m-chloroperbenzoic acid as an oxidant. Among the three hybrid compounds, 1-butyl-3-methyl imidazolium phosphotungstate was found to be the best and efficient catalyst for selective aniline oxidation to nitrobenzene. It is a recoverable and reusable catalytic system. The redox property of the phosphotungstate cluster in the hybrid material is involved in the catalytic activity. Graphical Abstract: [Figure not available: see fulltext.].
- Meenakshi,Shakeela,Kutti Rani,Ranga Rao
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p. 246 - 257
(2017/10/23)
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- Method for preparing nitro compound by using graphene to catalyze nitric oxide
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The invention discloses a method for preparing a nitro compound by using graphene to catalyze nitric oxide. A graphene oxide carbon material is used for catalysis of a reaction of nitric oxide and a nitrification substrate such as an aromatic compound to prepare the nitro compound. The method is used for replacing a traditional nitric acid/sulfur acid method to prepare the nitro compound, so thatthe atom utilization rate of the reaction is increased, the energy is saved, and the emission is reduced; and the method has the characteristic of atom economy during industrial preparation of the nitro compound.
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Paragraph 0033; 0034
(2018/06/16)
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- Nitrogen Oxides and Nitric Acid Enable the Sustainable Hydroxylation and Nitrohydroxylation of Benzenes under Visible Light Irradiation
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A new type of waste recycling strategy is described in which nitrogen oxides or nitric acid are directly employed in photocatalyzed hydroxylations and nitrohydroxylations of benzenes. Through these transformations, otherwise costly denitrification can be combined with the synthesis of valuable compounds for various applications.
- Hofmann, Laura Elena,Mach, Leonard,Heinrich, Markus R.
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supporting information
p. 431 - 436
(2017/12/15)
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- Rapid photocatalytic degradation of nitrobenzene under the simultaneous illumination of UV and microwave radiation fields with a TiO2 ball catalyst
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To use the microwave/ML/TiO2 hybrid system as an advanced treatment of nitrobenzene (NB), a series of experiments were performed to examine the effects of microwave irradiation and auxiliary oxidants. The degradation of NB was carried out using different combinations of five-unit treatment techniques. The NB degradation rate increased with increasing microwave intensity. The circulation fluid velocity, concentration of H2O2, and the rate of O2 gas injection showed the highest rate of degradation under optimal conditions. A significant synergistic effect was observed when H2O2 addition was combined with the microwave/ML/TiO2 hybrid process.
- Jeong, Sangmin,Lee, Heon,Park, Hyunwoong,Jeon, Ki-Joon,Park, Young-Kwon,Jung, Sang-Chul
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- Visible-Light-Induced Radical Polynitration of Arylboronic Acids: Synthesis of Polynitrophenols
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We report a visible light-assisted one-pot method for the synthesis of polynitrophenols through radical tandem hydroxylation and nitration of arylboronic acids by utilizing copper(II) nitrate tri-nitydrate as the nitro source. This method features mild conditions, a simple procedure, and good functional group tolerance. Compared to conventional methods, this work provides a straightforward approach for the polynitration of aromatic compounds.
- Zhang, Qi,Raveendra Babu, Kaki,Huang, Zhouliang,Song, Jinna,Bi, Xihe
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p. 2891 - 2896
(2018/06/20)
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- Biotransformation of 5′-O-β-D-galactosyl-floxuridine by immobilized β-galactosidase from Kocuria rhizophila
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5-fluorouracil-2’-deoxyriboside (FUdR), an antimetabolite known as floxuridine, is a halogenated nucleoside extensively used in the clinical treatment of colon carcinoma and hepatic metastases. This drug presents low bioavailability, thus requiring large doses and frequent administration, which leads to long-lasting and severe side effects in clinical practice. In order to overcome this problem, galactosylated nucleoside analogues were obtained using immobilized β-galactosidase in Ca-alginate with yields of 80% at only 7 h. Additionally, the obtained biocatalyst was stable for 6 months in storage conditions (4 °C) and could be reused at least 16 times without loss of its activity at 30 °C. This work describes for the first time an efficient, eco-compatible and simple bioprocess for obtaining 5′-O-β-D-galactosyl-floxuridine using an immobilized biocatalyst.
- Sarquiz, Andrea,Rivero, Cintia W.,Britos, Claudia N.,Trelles, Jorge A.
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- Complexes of copper(I) with aromatic compounds facilitate selective electrophilic aromatic substitution
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We report on the selective formation of ortho-nitrophenol, ortho-nitrotoluene (1-Methyl-2-nitrobenzene) and ortho-phenolsulfonic acid (2-Hydroxybenzenesulfonic acid) through reaction of the Cu(I)-aromatic ring complex of phenol or toluene. In the case of nitration of phenol, the reaction could be formulated as: (Figure presented.) The copper(I)-aromatic ring complex is formed in situ from Cu(II) and metallic copper in deaerated aqueous solutions containing the aromatic compounds. Phenol or toluene shift the comproportionation reaction of copper(0) and copper(II) towards the formation of Cu(I): (Formula presented.) The stability constant of Cu(I)-phenol in aqueous solutions was reported previously as 900 ± 100 M?1. The surprisingly stable d?π* Cu(I)-phenol complex causes distortion of the ring structure which facilitates selective substitutions. Similar results are reported for sulfonation of phenol (in aqueous solutions) and for nitration and sulfonation of toluene in a two phase process.
- Saphier, Magal,Levitsky, Inna,Masarwa, Alexandra,Saphier, Oshra
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p. 1738 - 1748
(2018/10/24)
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- Online Monitoring of Enzymatic Reactions Using Time-Resolved Desorption Electrospray Ionization Mass Spectrometry
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Electrospray ionization mass spectrometry (ESI-MS) is powerful for determining enzymatic reaction kinetics because of its soft ionization nature. However, it is limited to use ESI-favored solvents containing volatile buffers (e.g., ammonium acetate). In addition, lack of a quenching step for online ESI-MS reaction monitoring might introduce inaccuracy, due to the possible acceleration of reaction in the sprayed microdroplets. To overcome these issues, this study presents a new approach for online measuring enzymatic reaction kinetics using desorption electrospray ionization mass spectrometry (DESI-MS). By using DESI-MS, enzymatic reaction products in a buffered aqueous media (e.g., a solution containing Tris buffer or high concentration of inorganic salts) could be directly detected. Furthermore, by adjusting the pH and solvent composition of the DESI spray, reaction can be online quenched to avoid the postionization reaction event, leading to fast and accurate measurement of kinetic constants. Reaction time control can be obtained simply by adjusting the injection flow rates of enzyme and substrate solutions. Enzymatic reactions examined in this study include hydrolysis of 2-nitrophenyl-β-D-galactopyranoside by β-galactosidase and hydrolysis of acetylcholine by acetylcholinesterase. Derived Michaelis-Menten constants Km for these two reactions were determined to be 214 μM and 172 μM, respectively, which are in good agreement with the values of 300 μM and 230 μM reported in literature, validating the DESI-MS approach. Furthermore, this time-resolved DESI-MS also allowed us to determine Km and turnover number kcat for trypsin digestion of angiotensin II (Km and kcat are determined to be 6.4 mM and 1.3 s-1, respectively).
- Cheng, Si,Wu, Qiuhua,Xiao, He,Chen, Hao
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p. 2338 - 2344
(2017/08/09)
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- Enhanced production of gypenoside LXXV using a novel ginsenoside-transforming β-glucosidase from ginseng-cultivating soil bacteria and its anti-cancer property
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Minor ginsenosides, such as compound K, Rg3(S), which can be produced by deglycosylation of ginsenosides Rb1, showed strong anti-cancer effects. However, the anticancer effects of gypenoside LXXV, which is one of the deglycosylated shapes of ginsenoside Rb1, is still unknown due to the rarity of its content in plants. Here, we cloned and characterized a novel ginsenoside-transforming β-glucosidase (BglG167b) derived from Microbacterium sp. Gsoil 167 which can efficiently hydrolyze gypenoside XVII into gypenoside LXXV, and applied it to the production of gypenoside LXXV at the gram-scale with high specificity. In addition, the anti-cancer activity of gypenoside LXXV was investigated against three cancer cell lines (HeLa, B16, and MDA-MB231) in vitro. Gypenoside LXXV significantly reduced cell viability, displaying an enhanced anti-cancer effect compared to gypenoside XVII and Rb1. Taken together, this enzymatic method would be useful in the preparation of gypenoside LXXV for the functional food and pharmaceutical industries.
- Cui, Chang-Hao,Kim, Da Jung,Jung, Suk-Chae,Kim, Sun-Chang,Im, Wan-Taek
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supporting information
(2017/06/08)
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- Potassium Periodate/NaNO2/KHSO4-Mediated Nitration of Aromatic Compounds and Kinetic Study of Nitration of Phenols in Aqueous Acetonitrile
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Synthesis and kinetics of potassium periodate(KIO4)/NaNO2/KHSO4)-initiated nitration of aromatic compounds have been studied in aqueous acetonitrile medium. Synthesis of nitroaromatic compounds is achieved under conventional and solvent-free microwave conditions. Reaction times in microwave-assisted reaction are comparatively less than in conventional reaction. The reaction kinetics for the nitration of phenols in aqueous bisulfate and acetonitrile medium indicated first-order dependence on [phenol], [NaNO2], and [KIO4]. An increase in [KHSO4] accelerated the rate of nitration under otherwise similar conditions. The rate of nitration increased in the solvent of high dielectric media (solvents with high dielectric constant (D)). Observed results were in accordance with Amis and Kirkwood plots [log k′ vs. (1/D) and [(D ? 1)/(2D + 1)]. These observations probably indicate the participation of anionic species and molecular or (dipolar) species in the rate-determining step. In addition, the plots of (log k′) versus volume% of organic solvent were also linear, which probably indicate the importance of both electrostatic and nonelectrostatic forces, solvent–solute interactions during nitration of phenols. Reaction rates accelerated with the introduction of electron-donating groups and retarded with electron-withdrawing groups, but results could not be quantitatively correlated with Hammett's equation and depicted deviations from linearity. These deviations could probably be attributed to cumulative effects arising inductive, resonance, and steric effects. Leffler's plot (ΔH# vs. ΔS#) was found linear indicating the compensation (cumulative) effect of both enthalpy and entropy parameters in controlling the mechanism of nitration.
- Sriram, Y. Hemanth,Fatima, Touheeth,Rajanna,Kumar, M. Satish,Raju, R. Madhusudan
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supporting information
p. 622 - 632
(2017/06/30)
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- Yttrium Nitrate mediated Nitration of Phenols at room temperature in Glacial Acetic acid
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Rapid nitration of electron rich phenols using Y(NO 3) 3.6H 2O in glacial acetic acid at room temperature was observed with good yield. The method allows nitration of phenols without oxidation, and isolation of nitration product in a rapid and simple way. The described method is selective for phenols. [Figure not available: see fulltext.]
- Mondal, Mohabul A,Mandal, Debashis,Mitra, Kanchan
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- A phenol compound green nitration method and application
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The invention discloses a green nitrification method and application for a phenolic compound, belonging to the technical field of organic synthesis. The method provided by the invention comprises the following steps: with the phenolic compound as a raw material, dissolving the phenolic compound into a solvent at room temperature, adding sodium nitrite, then dropwise adding hydrogen peroxide into the obtained reaction solution, adding water-soluble metalloporphyrin at room temperature and starting reaction, carrying out nitrification reaction under stirring, then carrying out extraction by using an organic solvent, and carrying out vacuum concentration and column chromatographic separation so as to obtain a target product. The nitrification method provided by the invention has the advantages of mild reaction conditions, no need of heating, convenient operation and easy treatment of products. The green nitrification reaction is suitable for the phenolic compound.
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Paragraph 0038; 0039; 0040; 0041; 0042; 0043; 0044-0047
(2017/08/24)
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- A ortho-nitro phenol and its derivative synthesis method (by machine translation)
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The invention relates to a method for the synthesis of organic compounds, in the existing technology of O-nitrophenol strong acid used in the synthesis process of the serious problem of environmental pollution and the synthesis step longer more complicated problem, the invention provides a ortho-nitro phenol and synthetic method of derivative thereof, proceeding by the phenol compound, synthesis of 2 - (phenoxy) pyridine, the obtained product, catalyst, tert-butyl nitrite, organic solvent and adding sealing in the pressure containers, in oil bath heating 50 - 100 °C, reaction 10 - 30 hours, to obtain 2 - (2 - nitrobenzene) ethoxy pyridine; re-processing by the ortho-nitro phenol and its derivatives; the method is simple, high-efficiency. (by machine translation)
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- Specific Enhancement of Catalytic Activity by a Dicopper Core: Selective Hydroxylation of Benzene to Phenol with Hydrogen Peroxide
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A dicopper(II) complex, stabilized by the bis(tpa) ligand 1,2-bis[2-[bis(2-pyridylmethyl)aminomethyl]-6-pyridyl]ethane (6-hpa), [Cu2(μ-OH)(6-hpa)]3+, was synthesized and structurally characterized. This complex catalyzed selective hydroxylation of benzene to phenol using H2O2, thus attaining large turnover numbers (TONs) and high H2O2 efficiency. The TON after 40 hours for the phenol production exceeded 12000 in MeCN at 50 °C under N2, the highest value reported for benzene hydroxylation with H2O2 catalyzed by homogeneous complexes. At 22 % benzene conversion, phenol (95.2 %) and p-benzoquinone (4.8 %) were produced. The mechanism of H2O2 activation and benzene hydroxylation is proposed.
- Tsuji, Tomokazu,Zaoputra, Antonius Andre,Hitomi, Yutaka,Mieda, Kaoru,Ogura, Takashi,Shiota, Yoshihito,Yoshizawa, Kazunari,Sato, Hiroyasu,Kodera, Masahito
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supporting information
p. 7779 - 7782
(2017/06/28)
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- A promising catalyst for exclusive: Para hydroxylation of substituted aromatic hydrocarbons under UV light
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Herein, we describe a waterborne polymer/carbon dot nanocomposite system as an efficient, resourceful and sustainable photocatalyst for para-selective hydroxylation of substituted aromatic compounds using H2O2 under UV light. The polymer matrix and carbon dot generate a synergistic catalytic system. A unique structural attribute of the functionalities in this catalytic system attracts the aromatic substrates into close proximity and activates them. Additionally, the flexible molecular box-like structure of the hyperbranched polymer provides the ability for favorable three-point interaction with several substrates having various sizes by means of their multiple force networks and the increased accessibility of the active sites. The catalyst can be stored on the bench top for months and is reusable without considerable loss in its activity. The reaction was exclusively selective toward para hydroxylation irrespective of the nature of the substituents (electron donating or electron withdrawing) in the aromatic hydrocarbons. Hence, it is one of the most promising catalysts for selective hydroxylation of substituted aromatic hydrocarbons.
- Das, Vijay Kumar,Gogoi, Satyabrat,Choudary, Boyapati Manoranjan,Karak, Niranjan
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p. 4278 - 4283
(2017/09/29)
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- Novel CuCl2-cryptand-[2.2.Benzo] complex: A base free and oxidant free catalyst for Ipso-Hydroxylation of aryl/heteroaryl-boronic acids in water at room temperature
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A novel cryptand and its copper complex was synthesised, which found to have enormous catalytic activity towards ipso-hydroxylation of aryl or heteroarylboronic acids and esters in water without using H2O2 or other oxidising agent and base at room temperature. This newly developed method efficiently converts aryl boronic acids and esters as well as heteroaryl boronic acids to their corresponding phenols with high yields within a very short reaction time. This protocol has found to be well-matched with a wide variety of functional groups. High yields, very short reaction time, easy separation, recyclability up to 6th time are the advantages of this method.
- Bora, Sankar Jyoti,Chetia, Bolin
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supporting information
p. 52 - 56
(2017/09/19)
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- Biogenic synthesis of Fe2O3@SiO2 nanoparticles for ipso-hydroxylation of boronic acid in water
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Here, biogenic synthesis of Fe2O3@SiO2 nanoparticles using fruit extract of Zanthoxylum rhetsa is reported. The SiO2 nanoparticles was synthesized using paddy straw which is a byproduct obtained in cultivation of rice. The composite was characterised by spectroscopic method like XRD, SEM, TEM and EDX analysis. The ipso-hydroxylation reactions were carried out with excellent yield within a moderate time period with mild reaction condition in all cases. Therefore, this approach may be considered as simple, easy, cheap and greener, environment friendly protocol for ipso-hydroxylation of arylboronic acids at 50 °C temperature.
- Saikia, Indranirekha,Hazarika, Moushumi,Hussian, Najrul,Das, Manash R.,Tamuly, Chandan
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p. 4255 - 4259
(2017/10/11)
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