- Titanium Substitution in Silicon-free Molecular Sieves: Anatase-free TAPO4-5 and TAPO4-11 Synthesis and Characterisation for Hydroxylation of Phenol
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Titanium-substituted ALPO4-5 and ALPO4-11 are synthesised using a modified procedure; they catalyse the hydroxylation of phenol to the extent of ca. 32percent, with good selectivity to catechol.
- Ulagappan, N.,Krishnasamy, V.
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- Synthesis of methyl 1-hydroxy-6-oxo-2-cyclohexenecarboxylate, a component of salicortin and tremulacin, and the monomer of idesolide
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(Chemical Equation Presented) We have developed a short and practical first synthesis of methyl 1-hydroxy-6-oxo-2-cyclohexenecarboxylate (2), which has been known as a component of salicortin and tremulacin since 1970. Birch reduction of the SEM ether of methyl salicylate followed by oxidation of the intermediate enolate with (-)-camphorsulfonyloxaziridine afforded the SEM enol ether of 2. Hydrolysis of the SEM enol ether afforded 2. We did not observe the dimerization of either racemic or optically enriched 2 to give idesolide (1).
- Richardson, Amie M.,Chen, Chun-Hsing,Snider, Barry B.
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- New hydrotalcite-like anionic clays containing Zr4+ in the layers
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New hydrotalcite-like anionic clays containing Zr4+ in the brucite-like layers are synthesised by a simple coprecipitation technique; these materials show very interesting properties as catalysts for liquid-phase hydroxylation of phenol with H2O2.
- Velu,Ramaswamy, Veda,Ramani,Chanda, Bhanu M.,Sivasanker
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- An iron-based micropore-enriched silica catalyst:: In situ confining of Fe2O3 in the mesopores and its improved catalytic properties
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Surface exposed catalytic active species are thought to be responsible for overall catalytic activity and selectivity. In this paper, controllable contents of iron oxides were in situ introduced into the inner surface of anionic surfactant-templated mesop
- Long, Saifu,Zhou, Shijian,Yang, Fu,Lu, Kangchao,Xi, Tao,Kong, Yan
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- Flavoenzyme-mediated Regioselective Aromatic Hydroxylation with Coenzyme Biomimetics
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Regioselective aromatic hydroxylation is desirable for the production of valuable compounds. External flavin-containing monooxygenases activate and selectively incorporate an oxygen atom in phenolic compounds through flavin reduction by the nicotinamide adenine dinucleotide coenzyme, and subsequent reaction with molecular oxygen. This study provides the proof of principle of flavoenzyme-catalyzed selective aromatic hydroxylation with coenzyme biomimetics. The carbamoylmethyl-substituted biomimetic in particular affords full conversion in less than two hours for the selective hydroxylation of 5 mM 3- and 4-hydroxybenzoates, displaying similar rates as with NADH, achieving a 10 mM/h enzymatic conversion of the medicinal product gentisate. This biomimetic appears to generate less uncoupling of hydroxylation that typically leads to undesired hydrogen peroxide. Therefore, we show these flavoenzymes have the potential to be applied in combination with biomimetics.
- Guarneri, Alice,Westphal, Adrie H.,Leertouwer, Jos,Lunsonga, Joy,Franssen, Maurice C. R.,Opperman, Diederik J.,Hollmann, Frank,van Berkel, Willem J. H.,Paul, Caroline E.
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- Heterogeneous Nitrogen-doped Graphene Catalysed HOO? Generation via a Non-radical Mechanism for Base-free Dakin Reaction
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A heterogeneous nitrogen-doped graphene catalytic pathway for H2O2 activation to generate alkaline hydrogen peroxide (HOO?) through a non-radical mechanism was reported. Remarkably, the heterogeneous catalytic procedure has been used for the evergreen and environmentally Dakin reaction without using any transition metals, homogeneous bases, ligands, additives or promoters, completely. The study of catalyst structure and catalytic activities indicate that the most active sites are created by the graphitic N atoms at zig-zag edges of the sheets. In addition, N as dopant element changes the reactivity of the neighbour C atoms, and leads to the formation of carbon-hydroperoxide (C?(HOOH)) and C?O* (C?O?) transition state species on the graphene surface in catalytic the reaction. (Figure presented.).
- Sun, Wei,Gao, Lingfeng,Sun, Xu,Yang, Hua,Zheng, Gengxiu
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- Electrochemical oxidation of catechol in the presence of cyclopentadiene. Investigation of electrochemically induced Diels-Alder reactions
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We describe the synthesis and kinetic evaluation of compounds from [4 + 2] alone and [4 + 2] followed by [2 + 2] cycloaddition reactions of electrochemically generated o-benzoquinone with 1,3-cyclopentadiene. The Royal Society of Chemistry 2006.
- Nematollahi, Davood,Workentin, Mark S.,Tammari, Esmail
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- Application of advanced oxidation processes for removing salicylic acid from synthetic wastewaters
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In this study, advanced oxidation processes (AOPs) such as anodic oxidation (AO), UV/H2O2 and Fenton processes (FP) were investigated for the degradation of salicylic acid (SA) in lab-scale experiments. Boron-doped diamond (BDD) film electrodes using Ta as substrates were employed for AO of SA. In the case of FP and UV/H2O2, most favorable experimental conditions were determined for each process and these were used for comparing with AO process. The study showed that the FP was the most effective process under acidic conditions, leading to the highest rate of SA degradation in a very short time interval. However, the results showed that Ta/BDD films had high electrocatalytic activity for complete degradation of SA; even if it employs more time for complete elimination of the SA respect to FP. Additionally, AO led to a sixfold acceleration of the oxidation rate compared with the UV/H2O2 process. Finally a rough comparison of the specific energy consumption shows that AO process reduced the energy consumption by at least 90% compared with the UV/H2O2 process.
- Chen, Xue Ming,da Silva, Djalma Ribeiro,Martínez-Huitle, Carlos A.
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- Synthesis and catalytic properties of multilayered MEL-type titanosilicate nanosheets
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Multilayered MEL-type titanosilicate nanosheets (MTS-2) were hydrothermally synthesized through a dual-template method, using cetyltrimethylammonium tosylate (CTATos) and tetrabutylammonium hydroxide (TBAOH) as templates for mesopores and micropores, resp
- Chen, Hong Li,Li, Shang Wei,Wang, Yi Meng
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- Mechanistic investigations in ultrasound-assisted biodegradation of phenanthrene
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This study has addressed the biodegradation of polycyclic aromatic hydrocarbon, phenanthrene using Candida tropicalis. Optimization using central composite statistical design yielded optimum experimental parameters as: pH = 6.2, temperature = 33.4 °C, mechanical shaking = 190 rpm and % inoculum = 9.26% v/v. Sonication of biodegradation mixture at 33 kHz and 10% duty cycle in log phase (12 h per day for 4 days) resulted in a 25% enhancement in phenanthrene removal. Profiles of specific growth rate (μ) and specific degradation rate (q) versus initial substrate concentration were fitted to Haldane substrate inhibition model. Both μ and q showed maxima for initial concentration of 100 mg L?1. Kinetic analysis of degradation profiles showed higher biomass yield coefficient and smaller decay coefficient in presence of sonication. Expression of total intracellular proteins in control and test experiments were analyzed using SDS–PAGE. This analysis revealed overexpression of enzyme catechol 2,3-dioxygenase (in meta route metabolism) during sonication which is involved in ring cleavage of phenanthrene. Evaluation of cell viability after sonication by flow cytometry analysis revealed > 80% live cells. These effects are attributed to enhanced cellular transport induced by intense microturbulence generated by sonication.
- Kashyap, Niharika,Roy, Kuldeep,Moholkar, Vijayanand S.
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- Hydroxylation of phenol with hydrogen peroxide in protic and aprotic solvents on TS-1 catalyst
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Hydroxylation of phenol with a 25% aqueous solution of hydrogen peroxide in polar protic and aprotic solvents on TS-1 heterogeneous catalyst under various conditions was studied. The major reaction products (hydroquinone, pyrocatechol) and their ratio wer
- Potekhin,Kulikova,Vasil'Ev,Kohina,Potekhin
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- Enabling microbial syringol conversion through structure-guided protein engineering
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Microbial conversion of aromatic compounds is an emerging and promising strategy for valorization of the plant biopolymer lignin. A critical and often rate-limiting reaction in aromatic catabolism is O-aryl-demethylation of the abundant aromatic methoxy groups in lignin to form diols, which enables subsequent oxidative aromatic ring-opening. Recently, a cytochrome P450 system, GcoAB, was discovered to demethylate guaiacol (2-methoxyphenol), which can be produced from coniferyl alcohol-derived lignin, to form catechol. However, native GcoAB has minimal ability to demethylate syringol (2,6-dimethoxyphenol), the analogous compound that can be produced from sinapyl alcohol-derived lignin. Despite the abundance of sinapyl alcohol-based lignin in plants, no pathway for syringol catabolism has been reported to date. Here we used structure-guided protein engineering to enable microbial syringol utilization with GcoAB. Specifically, a phenylalanine residue (GcoA-F169) interferes with the binding of syringol in the active site, and on mutation to smaller amino acids, efficient syringol O-demethylation is achieved. Crystallography indicates that syringol adopts a productive binding pose in the variant, which molecular dynamics simulations trace to the elimination of steric clash between the highly flexible side chain of GcoA-F169 and the additional methoxy group of syringol. Finally, we demonstrate in vivo syringol turnover in Pseudomonas putida KT2440 with the GcoA-F169A variant. Taken together, our findings highlight the significant potential and plasticity of cytochrome P450 aromatic O-demethylases in the biological conversion of lignin-derived aromatic compounds.
- Machovina, Melodie M.,Mallinson, Sam J.B.,Knott, Brandon C.,Meyers, Alexander W.,Garcia-Borràs, Marc,Bu, Lintao,Gado, Japheth E.,Oliver, April,Schmidt, Graham P.,Hinchen, Daniel J.,Crowley, Michael F.,Johnson, Christopher W.,Neidle, Ellen L.,Payne, Christina M.,Houk, Kendall N.,Beckham, Gregg T.,McGeehan, John E.,DuBois, Jennifer L.
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- Biocatalytic Methyl Ether Cleavage: Characterization of the Corrinoid-Dependent Methyl Transfer System from Desulfitobacterium hafniense
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The ether functionality represents a very common motif in organic chemistry and especially the methyl ether is commonly found in natural products. Its formation and cleavage can be achieved via countless chemical procedures. Nevertheless, since in particular the cleavage often involves harsh reaction conditions, milder alternatives are highly demanded. Very recently, we have reported on a biocatalytic shuttle catalysis concept for reversible cleavage and formation of phenolic O-methyl ethers employing a corrinoid-dependent methyl transferase system from the anaerobic organism Desulfitobacterium hafniense. Here we report the technical study of this system, focusing on the demethylation of guaiacol as model reaction. The optimal buffer-, pH-, temperature- and cofactor-preferences were determined as well as the influence of organic co-solvents. Beside methyl cobalamin also hydroxocobalamin turned out to be a suitable cofactor species, although the latter required activation. Various O-methyl phenyl ethers were successfully demethylated with conversions up to 82% at 10 mM substrate concentration. (Figure presented.).
- Richter, Nina,Farnberger, Judith E.,Pompei, Simona,Grimm, Christopher,Skibar, Wolfgang,Zepeck, Ferdinand,Kroutil, Wolfgang
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- Novel polystyrene-anchored zinc complex: Efficient catalyst for phenol oxidation
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The novel recyclable free -ONNO- tetradentate Schiff base ligand N,N'-bis(2-hydroxy-3-methoxybenzaldehyde)4-methylbenzene-1,2-diamine (3-MOBdMBn) was synthesized. Complexation of this ligand with zinc (3-MOBdMBn-Zn) was performed, and the catalytic activity of the complex was evaluated. The polymer-supported analog of this complex (P-3-MOBdMBn-Zn) was synthesized, and its catalytic activity was studied. These free and polymer-anchored zinc complexes were prepared by the reactions of metal solutions with one molar equivalent of unsupported 3-MOBdMBn or P-3-MOBdMBn in methanol under nitrogen. The catalytic activity of 3-MOBdMBn-Zn and P-3-MOBdMBn-Zn was evaluated in phenol oxidation. The activity of P-3-MOBdMBn-Zn was significantly affected by the polymer support, and the rate of phenol conversion was around 50% for polystyrene-supported 3-MOBdMBn. The experimental results indicated that the reaction rate was affected by the polymer support, and the rate of phenol conversion was 1.64 μmol/(L·s) in the presence of polystyrene-supported 3-MOBdMBn.
- Sutar, Alekha Kumar,Das, Yasobanta,Pattnaik, Sasmita,Routaray, Anita,Nath, Nibedita,Rath, Prasanta,Maharana, Tungabidya
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- Sodium Percarbonate: A Convenient Reagent for the Dakin Reaction
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Sodium percarbonate, a readily available, inexpensive and easy to handle reagent efficiently oxidizes hydroxylated benzaldehydes and hydroxylated acetophenones to hydroxyphenols.
- Kabalka, G. W.,Reddy, N. K.,Narayana, C.
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- A Family of Routes to Substituted Phenols, Including Meta-Substituted Phenols
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A new family of routes to substituted phenols has been developed. 2-Bromo-3-methoxycyclohex-2-en-1-ones are readily deprotonated at C-6, and the resulting anions react smoothly with a variety of electrophiles; treatment with DBU in PhMe at room temperature then results in efficient aromatization to benzene derivatives of a regiochemically defined substitution pattern. This sequence affords phenolic azides (ArN3), sulfides (ArSR, ArSAr′), selenides (ArSePh), alcohols [ArCH(OH)R], amino derivatives [ArCH(NHSO2Ar′)R), and 1,2-benzenediols. A complementary set of substitution patterns is obtained by DIBAL-H reduction or reaction with a Grignard reagent before aromatization; the latter process gives compounds in which the newly introduced substituent is meta to the phenolic hydroxyl.
- Shao, Wenjie,Clive, Derrick L.J.
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- Binuclear furanyl-azine metal complexes encapsulated in NaY zeolite as efficiently heterogeneous catalysts for phenol hydroxylation
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Two different methods A and B were used for preparing binuclear furanyl-azine metal complexes encapsulated in NaY zeolite. These new heterogeneous catalysts based on Fe(II) or Cu(II) complexes with a metal/ligand molar ratio of 2:1, were characterized by different spectroscopic techniques and chemical analysis which confirm the presence of the metal complexes inside the supercages of the zeolite. M?ssbauer spectroscopy technique analysis confirms the presence of the Fe3+- complexes in octahedral coordination. The new heterogeneous catalysts were catalytic evaluated by phenol hydroxylation and compared with the encapsulated metal furanyl-azine complexes in NaY zeolite. The zeolite themselves do not present any activity and the presence of the metal complexes improve their activity. All heterogeneous catalysts enhance higher conversion of phenol to catechol.
- Ku?niarska-Biernacka,Raposo,Batista,Soares,Pereira,Parpot,Oliveira,Skiba,Jartych,Fonseca,Neves
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- Biodegradation of phenol by Chlamydomonas reinhardtii
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The data presented in this particular study demonstrate that the biodegradation of phenol by Chlamydomonas reinhardtii is a dynamic bioenergetic process mainly affected by the production of catechol and the presence of a growth-promoting substrate in the culture medium. The study focused on the regulation of the bioenergetic equilibrium resulting from production of catechol after phenol oxidation. Catechol was identified by HPLC-UV and HPLC-ESI-MS/MS. Growth measurements revealed that phenol is a growth-limiting substrate for microalgal cultures. The Chlamydomonas cells proceed to phenol biodegradation because they require carbon reserves for maintenance of homeostasis. In the presence of acetic acid (a growth-promoting carbon source), the amount of catechol detected in the culture medium was negligible; apparently, acetic acid provides microalgae with sufficient energy reserves to further biodegrade catechol. It has been shown that when microalgae do not have sufficient energy reserves, a significant amount of catechol is released into the culture medium. Chlamydomonas reinhardtii acts as a versatile bioenergetic machine by regulating its metabolism under each particular set of growth conditions, in order to achieve an optimal balance between growth, homeostasis maintenance and biodegradation of phenol. The novel findings of this study reveal a paradigm showing how microalgal metabolic versatility can be used in the bioremediation of the environment and in potential large-scale applications.
- Ghanotakis, Demetrios F.,Mavroudakis, Leonidas,Nazos, Theocharis T.,Pergantis, Spiros A.
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- Preparation of Fe/activated carbon directly from rice husk pyrolytic carbon and its application in catalytic hydroxylation of phenol
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Rice husk pyrolytic carbon (PC) was pretreated by NaOH solution at 100°C for 5 h to remove SiO2 and then used to prepare Fe/activated carbon catalyst. The treated sample was impregnated with ferric nitrate solution, and then activated under N2 atmosphere, obtaining Fe/activated carbon catalysts. The samples were characterized by temperature programed decomposition-mass spectra (TPD-MS), Brauner-Emmett-Teller (BET), inductively coupled plasma atomic emission spectrometry (ICP-AES), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The specific surface area increased with activation temperature until 750°C. With the increase of iron content, the specific surface area of carbon increased first up to 0.39 mmol g-1 iron loaded and then decreased. Reactive decomposition of ferric nitrate happened at 120-350°C releasing NO and CO2. Part of ferric (Fe(III)) species was reduced to ferrous (Fe(II)) species forming Fe3O4 at 400-550°C, and metal Fe at 650-750°C. The Fe/activated carbon exhibited high activity and selectivity for phenol hydroxylation.
- Zhang, Xian,Li, Yaxin,Li, Guiying,Huh, Changwei
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- Structural and electrochemical properties of lutetium bis-octachloro-phthalocyaninate nanostructured films. Application as voltammetric sensors
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Thin films of the bis[2,3,9,10,16,17,23,24-octachlorophthalocyaninate] lutetium(III) complex (LuPc2Cl32) have been prepared by the Langmuir-Blodgett and the Langmuir-Schaefer (LS) techniques. The influence of the chlorine substituents in the structure of the films and in their spectroscopic, electrochemical and sensing properties has been evaluated. The -A isotherms exhibit a monolayer stability greater than the observed in the unsubstituted analogue (LuPc2), being easily transferred to solid substrates, also in contrast to LuPc2. The LB and LS films present a linear growth forming stratified layers, monitored by UV-VIS absorption spectroscopy. The latter also revealed the presence of L LuPc2Cl32in the form of monomers and aggregates in both films. The FTIR data showed that the L LuPc2Cl32molecules present a non-preferential arrangement in both films. Monolayers of LB and LS were deposited onto 6 nm Ag island films to record surface-enhanced resonance Raman scattering (SERRS), leading to enhancement factors close to 2×103Finally, LB and LS films deposited onto ITO glass have been successfully used as voltammetric sensors for the detection of catechol. The improved electroactivity of the LB and LS films has been confirmed by the reduction of the overpotential of the oxidation of catechol. The enhancement of the electrocatalytic effect observed in LB and LS films is the result of the nanostructured arrangement of the surface which increases the number of active sites. The sensors show a limit of detection in the range of 10?5 mol/L.
- Alessio,Apetrei,Rubira,Constantino,Medina-Plaza,De Saja,Rodrguez-Mndez
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- Biocatalytic carboxylation of phenol derivatives: Kinetics and thermodynamics of the biological Kolbe-Schmitt synthesis
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Microbial decarboxylases, which catalyse the reversible regioselective ortho-carboxylation of phenolic derivatives in anaerobic detoxification pathways, have been studied for their reverse carboxylation activities on electron-rich aromatic substrates. Ortho-hydroxybenzoic acids are important building blocks in the chemical and pharmaceutical industries and are currently produced via the Kolbe-Schmitt process, which requires elevated pressures and temperatures (≥ 5 bar, ≥ 100 °C) and often shows incomplete regioselectivities. In order to resolve bottlenecks in view of preparative-scale applications, we studied the kinetic parameters for 2,6-dihydroxybenzoic acid decarboxylase from Rhizobium sp. in the carboxylation- and decarboxylation-direction using 1,2-dihydroxybenzene (catechol) as starting material. The catalytic properties (Km, Vmax) are correlated with the overall thermodynamic equilibrium via the Haldane equation, according to a reversible random bi-uni mechanism. The model was subsequently verified by comparing experimental results with simulations. This study provides insights into the catalytic behaviour of a nonoxidative aromatic decarboxylase and reveals key limitations (e.g. substrate oxidation, CO2 pressure, enzyme deactivation, low turnover frequency) in view of the employment of this system as a 'green' alternative to the Kolbe-Schmitt processes. Microbial decarboxylases are known to catalyze the reversible regioselective ortho-carboxylation of phenolic derivatives in anaerobic detoxification pathways. In order to get new insights into the catalytic action and to resolve bottlenecks in view applications, we studied the kinetics of 2,6-dihydroxybenzoic acid decarboxylase from Rhizobium sp. in the carboxylation- and decarboxylation-direction, correlating the data according to a reversible random bi-uni mechanism.
- Pesci, Lorenzo,Glueck, Silvia M.,Gurikov, Pavel,Smirnova, Irina,Faber, Kurt,Liese, Andreas
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- Polymer supported nickel complex: Synthesis, structure and catalytic application
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In the present investigation, a new synthetic route for a novel recyclable free [3-MOBdMBn-Ni] and polystyrene-anchored [P-3-MOBdMBn-Ni] nickel complexes is presented. The free and polymer-anchored metal complexes were synthesized by the reaction of nickel (II) with one molar equivalent of unsupported N N'-bis (2-Hydroxy-3-methoxybenzaldehyde) 4-Methylbenzene-1,2-diamine (3-MOBdMBn) or polymer-supported (P-3-MOBdMBn) Schiff-base ligand in methanol under nitrogen atmosphere. The advantages of these polymer-supported catalysts are the low cost of catalyst and recyclability up to six times, due to easy availability of materials and simple synthetic route. The higher efficiency of complexation of nickel on the polymer-anchored 3-MOBdMBn Schiff base than the unsupported analogue is another advantage of this catalyst system. The structural study reveals that nickel(II) complex of 3-MOBdMBn is square planar in geometry. The catalytic activity of nickel complex towards the oxidation of phenol was investigated in the presence of hydrogen peroxide. Experimental results indicate that the reactivity of P-3-MOBdMBn-Ni was dramatically affected by the polymer support compared to free 3-MOBdMBn-Ni. The rates of oxidation (Rp) for unsupported and supported catalysts are 1.37 × 10-6 mole dm-3 s-1 and 2.33 × 10-6 mole dm-3 s-1 respectively. [Figure not available: see fulltext.]
- Sutar, Alekha Kumar,Maharana, Tungabidya,Das, Yasobanta,Rath, Prasanta
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- Effect of structure of the redox molecular sieve TS-1 on the oxidation of phenol, crotyl alcohol and norbornylene
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A range of crystalline TS-1 samples with different morphologies as well as the corresponding TS-1 precursor structures have been synthesised using hydrothermal crystallisation. The materials have been characterised using powder X-ray diffraction, IR and Raman spectroscopy and electron microscopy. The materials were used as catalysts for the oxidation of crotyl alcohol, phenol and norbornylene and, in particular, the reactivity of the precursor structures was contrasted with crystalline TS-1. The oxidation of crotyl alcohol, selected as a relatively non-reactive substituted alkene, did not require the TS-1 structure for reactivity and TS-1 precursor structures are active, although crystalline TS-1 was found to be more reactive than the precursor structures. In contrast, phenol hydroxylation is only catalysed by crystalline TS-1. The reaction of phenol is observed to occur only on the exterior surface of large TS-1 crystallites. With smaller crystallites of TS-1, i.e. the size range of interest for catalysis, the rapid subsequent reaction of hydroquinone makes it difficult to determine whether reaction occurs solely on the exterior of the crystallites or at sites within the porous structure. Hence it is suggested that this reaction has limited scope as a probe reaction for the reactivity of sites within the crystallites. It is, however, feasible that phenol hydroxylation is a viable probe reaction for TS-1 type structural units. Norbornylene was studied as an example of a reactant too large to enter the internal pore structure of TS-1 and hence only reaction at pore mouths and external surface sites was possible. Larger TS-1 crystallites were more active for this substrate than suggested by surface area considerations. The results are discussed in terms of the selection of model reactions for the study of TS-1 catalysts. The Owner Societies 2005.
- Kerton, Owain J.,McMorn, Paul,Bethell, Donald,King, Frank,Hancock, Frederick,Burrows, Andrew,Kiely, Christopher J.,Ellwood, Simon,Hutchings, Graham
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- Hydroxylation of phenol over MeAPO molecular sieves synthesized by vapor phase transport
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In this study, MeAPO-25 (Me = Fe, Cu, Mn) molecular sieves were first synthesized by a vapor phase transport method using tetramethyl guanidine as the template and applied to hydroxylation of phenol. The zeolites were characterized by XRD, SEM, FT-IR, and
- Shao, Hui,Chen, Jingjing,Chen, Xia,Leng, Yixin,Zhong, Jing
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- ACYLATED FLAVANOLS AND PROCYANIDINS FROM SALIX SIEBOLDIANA
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An homologous series of acylated flavan-3-ols and procyanidins have been isolated, together with the known procyanidins B-1, B-3 and trimer, from the bark of Salix sieboldiana.Chemical and spectroscopic evidence led to the assignments of their structures as the 3-O-(1,6-dihydroxy-2-cyclohexene-1-carboxylic acid ester) of (+)-catechin and the 1-hydroxy-6-oxo-2-cyclohexene carboxylic acid esters of (+)-catechin and procyanidins B-1, B-3 and trimer.Key Word Index - Salix sieboldiana; Salicaceae; bark; acylated flavan-3-ols; acylated procyanidins; 1-hydroxy-6-oxo-2-cyclohexene-1-carboxylic acid; 1,6-dihydroxy-2-cyclohexene-1-carboxylic acid .
- Hsu, Feng-Lin,Nonaka, Gen-Ichiro,Nishioka, Itsuo
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- Hydroxyl radical generation via photoreduction of a simple pyridine N-oxide by an NADH analogue
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Photoreduction of pyridine N-oxide, which has a key structure of antitumor agents for hypoxic solid tumors, by 1-benzyl-1,4-dihydronicotinamide in deaerated aprotic media resulted in generation of hydroxyl radical, leading to the oxidation of salicylic acid to 2,3- and 2,5-dihydroxybenzoic acids, and catechol. The Royal Society of Chemistry 2005.
- Nakanishi, Ikuo,Nishizawa, Chiho,Ohkubo, Kei,Takeshita, Keizo,Suzuki, Kazuo T.,Ozawa, Toshihiko,Hecht, Sidney M.,Tanno, Masayuki,Sueyoshi, Shoko,Miyata, Naoki,Okuda, Haruhiro,Fukuzumi, Shunichi,Ikota, Nobuo,Fukuhara, Kiyoshi
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- Effects of tetrahydropterines on the generation of quinones catalyzed by tyrosinase
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Tetrahydrobiopterine (6BH4) can diminish the oxidative stress undergone by keratinocytes and melanocytes by reducing the o-quinones generated by the oxidation of the corresponding o-diphenols. We found that 6BH4 and their analogs reduced all the o-quinones studied. The formal potentials of different quinone/diphenol pairs indicate that the o-quinones with withdrawing groups are more potent oxidants than those with donating groups.
- Garcia-Molina, Francis,Munoz-Munoz, Joseph Louis,Martinez-Ortiz, Francis,Tudela, Joseph,Garcia-Canovas, Francis,Rodriguez-Lopez, Joseph Neptune
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- Copper(II)-imida-salen complexes encapsulated into NaY zeolite for oxidations reactions
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The oxidation of phenol, cychohexanol and hydroquinone has been screened in the presence of copper(II) complexes with the Schiff-base salen ligand, 1,5-bis[(E)-5-chloro-2-hydroxybenzylideneamino]-1H-imidazole-4-carbonitrile, and encapsulated into NaY zeolite by using two different methods. The new heterogeneous catalysts were characterized by SEM, XRD, FTIR, EPR and Raman spectroscopy as well as by chemical analysis. The structures of the copper(II) complexes were proposed on the basis of theoretical studies (DFT). The catalytic activities of the encapsulated copper(II) complexes in NaY were compared with their homogeneous counterparts. The results show higher or similar substrate conversion when compared with the free complex in all the reactions tested. After their use in catalytic reaction, these catalysts were found to be reusable without loss of activity. Novel catalysts based on imidazole Schiff bases and incorporated into NaY zeolite have been prepared and characterised. A DFT study confirmed the stability of the copper complexes formed. The heterogeneous catalysts are active and selective in the oxidation of alcohols. The catalysts could be reused without loss of activity. Copyright
- Kuzniarska-Biernacka, Iwona,Carvalho, M. Alice,Rasmussen, Soren B.,Banares, Miguel A.,Biernacki, Krzysztof,Magalhaes, Alexandre L.,Rolo, Anabela G.,Fonseca, Antonio M.,Neves, Isabel C.
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- Transition metal coordination polymers: Synthesis and catalytic study for hydroxylation of phenol and benzene
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New coordination polymers of Ni(II) and Cu(II) of the polymeric salen-type Schiff base ligand derived from the condensation of 5,5′-methylene bis-(salicyaldehyde) with 1,2-diaminopropane yielded N,N′-1,2- propylenebis(5-methylenesalicylidenamine) abbrevia
- Abbo, Hanna S.,Titinchi, Salam J.J.
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- Development of a new methodology for the synthesis of chloro(glycinato)1,10-phenanthroline copper(II) monohydrate and analogous complexes and study of their catalytic utility towards selective hydroxylation of phenol
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A new simple and convenient method has been developed for the synthesis of copper(II)complexes using Proline and Glycine as ligand. The complexes were characterized by using conventional spectroscopic techniques and by determining structure. Methodology developed gives substantial yield of the products. Chloro(Glycinato) 1,10-Phenanthroline Copper(II) monohydrate and other complexes effectively catalyze the selective orthohydroxylation of phenol, in presence of Hydrogen peroxide, in water. Catechol formation was confirmed by IR and NMR spectroscopy. Hydroxylation reaction produces moderate to good yield of the product catechol. Longer time duration results in decrease of yield.
- Baruah,Puzari
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- Single-Crystal-to-Single-Crystal [2 + 2] Photodimerization Involving B←N Coordination with Generation of a Thiophene Host
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We report on B←N coordination to support a single-crystal-to-single-crystal reaction in the solid state. A [2 + 2] photodimerization is achieved with face-to-face π-stacks of monotopic B←N adducts composed of a phenylboronic acid catechol ester and an alkene with a terminal thiophene group. The photoreaction generates a ditopic B-adduct involving a head-to-tail cyclobutane regio- and stereoselectively. The photodimerization is accompanied by an increase in the tetrahedral character of the B atom. The resulting boron enables channel confinement of chloroform upon recrystallization.
- Campillo-Alvarado, Gonzalo,Li, Changan,Feng, Zhiting,Hutchins, Kristin M.,Swenson, Dale C.,H?pfl, Herbert,Morales-Rojas, Hugo,Macgillivray, Leonard R.
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- Copper(II)-Catalyzed Reactions of Activated Aromatics
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The catalytic reaction of cis-bisglycinato copper(II) monohydrate in the presence of hydrogen peroxide leads to hydroxylation of phenol to give catechol and hydroquinone (1:1.2 ratio) in good yield. 2,6-Dimethylphenol can be hydroxylated by hydrogen peroxide and a catalytic amount of cis-bisglycinato copper(II) monohydrate to give an aggregate of 1,4-dihydroxy-2,6-dimethylbenzene and 2,6-dimethylphenol. A similar reaction of o-cresol gives 2,5-dihydroxytoluene. The reactivity of cis-bisglycinato copper(II) monohydrate in hydrogen peroxide with o-cresol is 4.5 times faster than that of a similar reaction by trans-bisglycinato copper(II) monohydrate. A catalytic reaction of cis-bisglycinato copper(II) monohydrate with aniline in aqueous hydrogen peroxide gives polyanilines in the form of pernigraniline with different amounts of Cu(OH)2 attached to them. The two major components of polyanilines obtained have Mn values of 1040 and 1500, respectively. Resistance of films of these polyanilines increases with temperatures from 40°C to a maximum value at 103°C and then decreases in the region of 103-150°C, showing the property of a thermoelectric switch. The aggregate prepared from hydroxylation of 2,6-dimethylphenol shows a similar property in the region of 30-180°C.
- Puzari,Baruah, Jubaraj B.
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- SELECTIVE ORTHO-HYDROXYLATION OF PHENOLS IN COPPER (I) COMPLEXES
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Several catechols are obtained by reacting excess of the corresponding phenols with the tetrahydroborato copper(I) complex (4) and subsequent dioxygen oxidation of the intermediate copper(I) phenoxo complex (1).
- Chioccara, Francesco,Gennaro, Patricia Di,Monica, Girolamo La,Sebastiano, Roberto,Rindone, Bruno
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- Imidazolium-Based Ionic Liquids as Efficient Reagents for the C?O Bond Cleavage of Lignin
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The demethylation of lignin in ionic liquids (ILs) was investigated by using pure lignin model monomers and dimers together with dioxane-isolated lignins from poplar, miscanthus, and maize. Different methylimidazolium ILs were compared and the samples were treated with two different heating processes: microwave irradiation and conventional heating in a sealed tube. The conversion yield and influence of the treatment on the lignin structure were assessed by 31P NMR spectroscopy, size-exclusion chromatography, and thioacidolysis. The acidic methylimidazolium IL [HMIM]Br was shown to be an effective combination of solvent and reagent for the demethylation and depolymerization of lignin. The relatively mild reaction conditions, the clean work-up, and the ability to reuse the IL makes the described procedure an attractive and new green method for the conversion of lignin to produce phenol-rich lignin oligomers.
- Thierry, Marina,Majira, Amel,Pégot, Bruce,Cezard, Laurent,Bourdreux, Flavien,Clément, Gilles,Perreau, Fran?ois,Boutet-Mercey, Stéphanie,Diter, Patrick,Vo-Thanh, Giang,Lapierre, Catherine,Ducrot, Paul-Henri,Magnier, Emmanuel,Baumberger, Stéphanie,Cottyn, Betty
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- VS-12: A Novel Large-pore Vanadium Silicate with ZSM-12 Structure
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A new large-pore vanadium silicate with ZSM-12 structure has been synthesized; ESR and NMR data indicate that the vanadium is located in the zeolite framework.
- Reddy, Kondam Madhusudan,Moudrakovski, Igor,Sayari, Abdelhamid
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- Selective oxidation of phenol and benzoic acid in water via home-prepared TiO2 photocatalysts: Distribution of hydroxylation products
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The hydroxylation of phenol (a substrate containing an electron donor group) and of benzoic acid (a substrate containing an electron withdrawing group) has been carried out by the photocatalytic method in aqueous suspensions containing commercial or home prepared TiO2 samples. The aim of the work was to study the distribution of hydroxylation products when different photocatalysts were used and to correlate the selectivity to some physico-chemical features of the powders. The samples were characterized by X-ray diffraction, thermogravimetry, determination of crystalline phase percentage, specific surface area and zero charge point. The photoreactivity results indicate that the products of the primary oxidation of phenol are the ortho- and para-mono-hydroxy derivatives while those of benzoic acid are all the mono-hydroxy derivatives independently of the catalyst. The selectivity toward mono-hydroxy derivatives shows a strong dependence on catalyst hydroxylation and crystallinity degrees: the highest selectivity values were obtained by using the commercial samples that resulted the least hydroxylated and the most crystalline ones. A kinetic model, taking into account the mineralization and the partial oxidation reaction routes, is proposed by using the Langmuir-Hinshelwood model.
- Bellardita, Marianna,Augugliaro, Vincenzo,Loddo, Vittorio,Megna, Bartolomeo,Palmisano, Giovanni,Palmisano, Leonardo,Puma, Maria Angela
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- The trifluoromethoxy group: A long-range electron-withdrawing substituent
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Judged by its capacity to promote a hydrogen/metal permutation at an ortho position, the trifluoromethoxy group is superior to both the methoxy and trifluoromethyl groups. Moreover, like CF3 and unlike OCH3, OCF3 exerts a long-range effect that still considerably lowers the basicity of arylmetal compounds when located in a more remote meta or even para position. As a consequence, 4-(trifluoromethoxy)-anisole is deprotonated by sec-butyllithium mainly, and by tert-butyllithium exclusively, at a position adjacent to the OCH3 group rather than next to the strongly electron-withdrawing CF3O group. 1,3-Benzodioxole undergoes ortho lithiation only six times faster than anisole, whereas 2,2-difluoro-1,3-benzodioxole reacts about 5000 times faster, as evidenced by competition experiments. The structure and distance dependence of substituent effects can be rationalized by assuming superposing σ- and π-polarizing interactions.
- Castagnetti, Eva,Schlosser, Manfred
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- Oxidation of Simple Phenols by a Homobimetallic Cerium(IV)-Calix(8)arene Complex in Conjunction with Hydrogen Peroxide
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Phenolic substrates are regioselectively hydroxylated under mild conditions with a cerium(IV)-calix(8)arene complex.
- Chawla, H. Mohindra,Hooda, Usha,Singh, Veena
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- Role of catechol in the radical reduction of B-alkylcatecholboranes in presence of methanol
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Mechanistic investigations on the previously reported reduction of B-alkylcatecholboranes in the presence of methanol led to the disclosure of a new mechanism involving catechol as a reducing agent. More than just revising the mechanism of this reaction, we disclose here the surprising role of catechol, a chain breaking antioxidant, which becomes a source of hydrogen atoms in an efficient radical chain process.
- Povie, Guillaume,Villa, Giorgio,Ford, Leigh,Pozzi, Davide,Schiesser, Carl H.,Renaud, Philippe
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- Photochemistry of Dimethoxybenzenes in Aqueous Sulfuric Acid
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The photochemistry of the three isomeric dimethoxybenzenes (1-3) has been studied in aqueous sulfuric acid.Two processes were found to take place: (i) photoprotonation of the ring resulting in exchange of the ring protons, which was observed for all three compounds and (ii) ipso substitution of the methoxy group by water, which was observed only for 1,2-dimethoxybenzene (3).Both of these photochemical reactions were catalyzed by acid, requiring acidities stronger than pH(D)2 for observable reaction.Quantum yields for proton exchange and ipso substitution are reported as a function of medium acidity.The fluorescence emissions of all three compounds were quenched by acid, to give sigmoid type quenching curves, that have a complementary relationship with the corresponding plots of quantum yield of exchange vs acidity, consistent with protonation of the benzene ring in S1 as the primary photochemical step, to give cyclohexadienyl cation intermediates.Stern-Volmer analysis of fluorescence quenching by proton gave photoprotonation rates in the range 0.09-2.2*109 M-1 s-1.The results of this work demonstrate unambiguously that methoxy-substituted benzenes are much stronger bases in S1 (pKBH+ ca. 1 to -2) than in the ground state.This enhanced basicity is manifested in regioselectivity of exchange of 1 and 3 and ipso substitution chemistry of 3, processes not observed in the ground states of these compounds.
- Pollard, Renee,Wu, Susan,Zhang, Guangzhong,Wan, Peter
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- Determination of catalytic oxidation products of phenol by RP-HPLC
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A reversed-phase high-performance liquid chromatography (RP-HPLC) with ultraviolet detection was established for the determination of phenol, catechol, hydroquinone, and p-benzoquinone in the reaction solution of catalytic oxidation of phenol using hydrogen peroxide as the oxidant and copper-doped FeSBA-15 zeolite as the catalyst. Separation was accomplished on a reversed-phase C18 column, and the elution condition was optimized by changing the composition of the mobile phase. A good resolution of all of the relative components in the reaction solution was achieved when the mobile phase was methanol-water-1% acetic acid aqueous solution = 10:50:40 (v/v/v). The concentrations of phenol, catechol, hydroquinone, and p-benzoquinone were determined in 11 different reaction solutions by the external standard method. The proposed HPLC method was simple, accurate, reliable, and suitable for tracing the amount of target products during the catalytic oxidation reaction of phenol. The results can provide data support for evaluating the properties of catalysts, and, thus, guide the selection of catalysts for the industrial production of dihydric phenol. Springer Science+Business Media B.V. 2011.
- Qiao, Jun-Qin,Yuan, Na,Tang, Chang-Jin,Yang, Jing,Zhou, Jian,Lian, Hong-Zhen,Dong, Lin
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- Multi-Enzymatic Cascade Reactions for the Synthesis of cis,cis-Muconic Acid
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Lignin valorization allows the generation of a number of value-added products such as cis,cis-muconic acid (ccMA), which is widely used for the synthesis of chemicals for the production of biodegradable plastic materials. In the present work, we reported the first multi-enzymatic, one-pot bioconversion process of vanillin into ccMA. In details, we used four sequential reactions catalyzed by xanthine oxidase, O-demethylase LigM (and the tetrahydrofolate-regeneration enzyme methyl transferase MetE), decarboxylase AroY (based on the use of E. coli transformed cells) and catechol 1,2-dioxygenase CatA. The optimized lab-scale procedure allowed to reach, for the first time, the conversion of 5 mM vanillin into ccMA in ～30 h with a 90% yield: this achievement represents an improvement in terms of yields and time when compared to the use of a whole-cell system. This multi-enzymatic system represents a sustainable alternative for the production of a high value added product from a renewable resource. (Figure presented.).
- Di Nardo, Giovanna,Gazzola, Silvia,Gilardi, Gianfranco,Pollegioni, Loredano,Rosini, Elena,Valetti, Francesca,Vignali, Elisa
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p. 114 - 123
(2021/10/07)
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- Imidazolium-urea low transition temperature mixtures for the UHP-promoted oxidation of boron compounds
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Different carboxy-functionalized imidazolium salts have been considered as components of low transition temperature mixtures (LTTMs) in combination with urea. Among them, a novel LTTM based on 1-(methoxycarbonyl)methyl-3-methylimidazolium chloride and urea has been prepared and characterized by differential scanning calorimetry throughout its entire composition range. This LTTM has been employed for the oxidation of boron reagents using urea-hydrogen peroxide adduct (UHP) as the oxidizer, thus avoiding the use of aqueous H2O2, which is dangerous to handle. This metal-free protocol affords the corresponding alcohols in good to quantitative yields in up to 5 mmol scale without the need of further purification. The broad composition range of the LTTM allows for the reaction to be carried out up to three consecutive times with a single imidazolium salt loading offering remarkable sustainability with an E-factor of 7.9, which can be reduced to 3.2 by the threefold reuse of the system.
- Martos, Mario,Pastor, Isidro M.
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- High-throughput assay of tyrosine phenol-lyase activity using a cascade of enzymatic reactions
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Tyrosine phenol-lyase (TPL) exhibits great potential in industrial biosynthesis of L-tyrosine and its derivates. To uncover and screen TPLs with excellent catalytic properties, there is unmet demand for development of facile and reliable screening system for TPL. Here we presented a novel assay format for the detection of TPL activity based on catechol 2,3-dioxygenase (C23O)-catalyzed reaction. Catechol released from TPL-catalyzed cleavage of 3,4-dihydroxy-L-phenylalanine (L-DOPA) was further oxidized by C23O to form 2-hydroxymuconate semialdehyde, which could be readily detected by spectrophotometric measurements at 375 nm. The assay achieved a unique balance between the ease of operation and superiority of analytical performances including linearity, sensitivity and accuracy. In addition, this assay enabled real-time monitoring of TPL activity with high efficiency and reliability. As C23O is highly specific towards catechol, a non-natural product of microorganism, the assay was therefore accessible to both crude cell extracts and the whole-cell system without elaborate purification steps of enzymes, which could greatly expedite discovery and engineering of TPLs. This study provided fundamental principle for high-throughput screening of other enzymes consuming or producing catechol derivatives.
- Hu, Wen-Ye,Tang, Xiao-Ling,Zheng, Ren-Chao,Zheng, Yu-Guo,Zhu, Hang-Qin
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- One-pot production of phenazine from lignin-derived catechol
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Upgrading lignin-derived monomeric products is crucial in bio-refineries to effectively utilize lignin. Herein, we report a simple strategy to convert catechol to phenazine, a useful N-heterocycle three-aromatic-ring compound, whose current synthetic procedure is complex via a petroleum-derived feedstock. The reaction uses catechol as the sole carbon source and aqueous ammonia as reaction media and a nitrogen source. Without additional solvents, phenazine was obtained in 67% yield in the form of high purity crystals (>97%) over a Pd/C catalyst after a one-pot-two-stage reaction. When cyclohexane was used as a co-solvent in the first step, a higher yield (81%) and purity (>99%) were achieved. Mechanistic investigations involving control experiments and an isotope labeling study reveal that hydrogenation, amination, coupling and dehydrogenation reactions are the key steps leading to phenazine formation. The conversion of other lignin-derived catechols highlights that the protocol is extendable to produce substituted phenazines.
- He, Zhimin,Qi, Wei,Ren, Tianyu,Yan, Ning
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supporting information
p. 1224 - 1230
(2022/02/17)
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- The role of remote flavin adenine dinucleotide pieces in the oxidative decarboxylation catalyzed by salicylate hydroxylase
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Salicylate hydroxylase (NahG) has a single redox site in which FAD is reduced by NADH, the O2 is activated by the reduced flavin, and salicylate undergoes an oxidative decarboxylation by a C(4a)-hydroperoxyflavin intermediate to give catechol. We report experimental results that show the contribution of individual pieces of the FAD cofactor to the observed enzymatic activity for turnover of the whole cofactor. A comparison of the kinetic parameters and products for the NahG-catalyzed reactions of FMN and riboflavin cofactor fragments reveal that the adenosine monophosphate (AMP) and ribitol phosphate pieces of FAD act to anchor the flavin to the enzyme and to direct the partitioning of the C(4a)-hydroperoxyflavin reaction intermediate towards hydroxylation of salicylate. The addition of AMP or ribitol phosphate pieces to solutions of the truncated flavins results in a partial restoration of the enzymatic activity lost upon truncation of FAD, and the pieces direct the reaction of the C(4a)-hydroperoxyflavin intermediate towards hydroxylation of salicylate.
- Brand?o, Tiago A. S.,Nagem, Ronaldo A. P.,Pereira, Mozart S.,Richard, John P.,de Araújo, Simara S.
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- Efficient demethylation of aromatic methyl ethers with HCl in water
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A green, efficient and cheap demethylation reaction of aromatic methyl ethers with mineral acid (HCl or H2SO4) as a catalyst in high temperature pressurized water provided the corresponding aromatic alcohols (phenols, catechols, pyrogallols) in high yield. 4-Propylguaiacol was chosen as a model, given the various applications of the 4-propylcatechol reaction product. This demethylation reaction could be easily scaled and biorenewable 4-propylguaiacol from wood and clove oil could also be applied as a feedstock. Greenness of the developed methodversusstate-of-the-art demethylation reactions was assessed by performing a quantitative and qualitative Green Metrics analysis. Versatility of the method was shown on a variety of aromatic methyl ethers containing (biorenewable) substrates, yielding up to 99% of the corresponding aromatic alcohols, in most cases just requiring simple extraction as work-up.
- Bomon, Jeroen,Bal, Mathias,Achar, Tapas Kumar,Sergeyev, Sergey,Wu, Xian,Wambacq, Ben,Lemière, Filip,Sels, Bert F.,Maes, Bert U. W.
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supporting information
p. 1995 - 2009
(2021/03/26)
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- Highly efficient titanosilicate catalyst Ti-MCM-68 prepared using a liquid-phase titanium source for the phenol oxidation
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A highly efficient Ti-MCM-68 catalyst for phenol oxidation with H2O2 was prepared by a mild liquid-phase treatment for the first time. The key preparation procedures to excellent catalytic activity and high para-selectivity were the use of aqueous solutions of the Ti source and calcination at 650 °C prior to catalytic use.
- Inagaki, Satoshi,Ishizuka, Ryo,Ikehara, Yuya,Odagawa, Shota,Asanuma, Kai,Morimoto, Shunsuke,Kubota, Yoshihiro
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p. 3681 - 3684
(2021/02/03)
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- Iron-catalyzed arene C-H hydroxylation
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The sustainable, undirected, and selective catalytic hydroxylation of arenes remains an ongoing research challenge because of the relative inertness of aryl carbon-hydrogen bonds, the higher reactivity of the phenolic products leading to over-oxidized by-products, and the frequently insufficient regioselectivity. We report that iron coordinated by a bioinspired L-cystine-derived ligand can catalyze undirected arene carbon-hydrogen hydroxylation with hydrogen peroxide as the terminal oxidant. The reaction is distinguished by its broad substrate scope, excellent selectivity, and good yields, and it showcases compatibility with oxidation-sensitive functional groups, such as alcohols, polyphenols, aldehydes, and even a boronic acid. This method is well suited for the synthesis of polyphenols through multiple carbon-hydrogen hydroxylations, as well as the late-stage functionalization of natural products and drug molecules.
- Cheng, Lu,Wang, Huihui,Cai, Hengrui,Zhang, Jie,Gong, Xu,Han, Wei
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- A Type of MOF-Derived Porous Carbon with Low Cost as an Efficient Catalyst for Phenol Hydroxylation
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Using MOF-5 as a template, the porous carbon (MDPC-600) possessing high specific surface area was obtained after carbonization and acid washing. After MDPC-600 was loaded with Cu ions, the catalyst Cu/MDPC-600 was acquired by heat treatment under nitrogen atmosphere. The catalyst was characterized by X-ray powder diffraction (XRD), N2 physical adsorption (BET), field emission electron microscope (SEM), energy spectrum, and transmission electron microscope (TEM). The results show that the Cu/MDPC-600 catalyst prepared by using MOF-5 as the template has a very high specific surface area, and Cu is uniformly supported on the carrier. The catalytic hydrogen peroxide oxidation reaction of phenol hydroxylation was investigated and exhibits better catalytic activity and stability in the phenol hydroxylation reaction. The catalytic effect was best when the reaction temperature was 80°C, the reaction time was 2 h, and the amount of catalyst was 0.05 g. The conversion rate of phenol was 47.6%; the yield and selectivity of catechol were 37.8% and 79.4%, respectively. The activity of the catalyst changes little after three cycles of use.
- Chen, Gui,Ni, Hairui,Ouyang, Yuejun,Xiang, Bailin,Zhou, Nonglin,Zhou, Renjie
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- Thiols Act as Methyl Traps in the Biocatalytic Demethylation of Guaiacol Derivatives
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Demethylating methyl phenyl ethers is challenging, especially when the products are catechol derivatives prone to follow-up reactions. For biocatalytic demethylation, monooxygenases have previously been described requiring molecular oxygen which may cause oxidative side reactions. Here we show that such compounds can be demethylated anaerobically by using cobalamin-dependent methyltransferases exploiting thiols like ethyl 3-mercaptopropionate as a methyl trap. Using just two equivalents of this reagent, a broad spectrum of substituted guaiacol derivatives were demethylated, with conversions mostly above 90 %. This strategy was used to prepare the highly valuable antioxidant hydroxytyrosol on a one-gram scale in 97 % isolated yield.
- Grimm, Christopher,Kroutil, Wolfgang,Pompei, Simona,Schiller, Christine,Schober, Lukas
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supporting information
p. 16906 - 16910
(2021/07/02)
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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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- A copper nitride catalyst for the efficient hydroxylation of aryl halides under ligand-free conditions
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Copper nitride (Cu3N) was used as a heterogeneous catalyst for the hydroxylation of aryl halides under ligand-free conditions. The cubic Cu3N nanoparticles showed high catalytic activity, comparable to those of conventional Cu catalysts with nitrogen ligands, demonstrating that the nitrogen atoms in Cu3N act as functional ligands that promote hydroxylation.
- Mitsudome, Takato,Mizugaki, Tomoo,Xu, Hang,Yamaguchi, Sho
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supporting information
p. 6593 - 6597
(2021/08/10)
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- Me3SI-promoted chemoselective deacetylation: a general and mild protocol
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A Me3SI-mediated simple and efficient protocol for the chemoselective deprotection of acetyl groups has been developedviaemploying KMnO4as an additive. This chemoselective deacetylation is amenable to a wide range of substrates, tolerating diverse and sensitive functional groups in carbohydrates, amino acids, natural products, heterocycles, and general scaffolds. The protocol is attractive because it uses an environmentally benign reagent system to perform quantitative and clean transformations under ambient conditions.
- Gurawa, Aakanksha,Kashyap, Sudhir,Kumar, Manoj
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p. 19310 - 19315
(2021/06/03)
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- Heterogeneous recyclable copper oxide supported on activated red mud as an efficient and stable catalyst for the one pot hydroxylation of benzene to phenol
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Phenol is a key intermediate in chemical industry. The present research work reports facile synthesis of a new copper supported activated red mud as a heterogeneous catalyst for oxidative conversion of benzene to phenol. The process is simple and efficient for one pot hydroxylation reaction using H2O2 as an oxidant. The catalyst was characterized using FTIR, XRD, TEM, XPS and BET surface area analyzer. Catalyst reducible properties were studied using H2-TPR technique. The one-pot hydroxylation reaction, carried out at 75 °C under optimum reaction conditions in presence of catalytic material, shows conversion of benzene to phenol with 84.5 % and 87.1 % selectivity and conversion efficiency, respectively. The proposed mechanism emphasizes upon cooperative effect of residual and embedded metal ions in solid catalyst matrix as the contributing factor for efficient conversion and selectivity. The reusable properties of the material, tested up to 5th consecutive cycles of batch operation, indicate retention of selectivity (83.9 %) as well as conversion efficiency (86.7 %), suitable for future commercial development adhering to the principle of green chemistry.
- Mishra, Subhashree,Bal, Rajaram,Dey
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- Preparation and photocatalytic performance of silver-modified and nitrogen-doped TiO2nanomaterials with oxygen vacancies
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The photocatalysis of titanium dioxide (TiO2) exerts excellent degradation performance against contaminants in the environment. However, it prefers to absorb ultraviolet light rather than visible light, which significantly constrains its widespread use under visible light. Here, we prepared oxygen vacancy-containing TiO2viaAg-modification and N-doping. The utilization of visible light for phenol degradation was significantly enhanced by Ag/N co-doping. The characterization results showed a shuttle-like material coupled with multiple oxygen vacancies, and a well-designed experiment demonstrated that the Ti?:?N?:?Ag ratio of 1?:?0.45?:?0.32 presented optimal performance for phenol degradation. The batch experiment results also proved the modified TiO2as a potent photocatalyst against phenol degradation with an 80.8% degradation efficiency within 5 hours under visible light and with a 99.3% degradation efficiency within 2 hours under ultraviolet light. What is more, we also demonstrated that hydroxyl radical was the mainly effective radical in the mineralization of phenol and put forward a possible degradation pathway based on the observed intermediates. Lastly, the cycling tests indicated that the proposed photocatalyst is durable with a fair phenol degradation ability after recycling 5 times.
- Zhang, Hong,Jiang, Yingyu,Zhou, Baiqin,Wei, Zhuo,Zhu, Zhenya,Han, Lijuan,Zhang, Ping,Hu, Yingying
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p. 4694 - 4704
(2021/03/22)
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- A high-nuclearity CuI/CuIInanocluster catalyst for phenol degradation
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Herein, we report a 54-nuclei copper nanocluster, [Cu54S13O6(tBuS)20(tBuSO3)12] (Cu54), which is the largest atom-precise CuI/CuIImix-valent cluster reported. The Cu54nanoclusters supported by TiO2exhibit decent photocatalytic activity for phenol degradation under visible light. This work provides a platform to explore the catalytic behaviors of CuI/CuIInanosystems.
- Liu, Li-Juan,Zhang, Jiang-Wei,Asad, Muhammad,Wang, Zhao-Yang,Zang, Shuang-Quan,Mak, Thomas C. W.
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supporting information
p. 5586 - 5589
(2021/06/12)
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- AEROBIC ELECTROCATALYTIC OXIDATION OF HYDROCARBONS
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This invention is directed to a method of oxygenating hydrocarbons with molecular oxygen, O2, as oxidant under electrochemical reducing conditions, using polyoxometalate compounds containing copper such as Q10 [Gu4(H2O)2(B-α-PW9O)2] or Q12{ [Cu(H2O)]3[(A-α- PW9O34)2(NO3)-] } or solvates thereof as catalysts, wherein Q are each independently selected from alkali metal cations, alkaline earth metal cations, transition metal cations, NH4+,H+ or any combination thereof.
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Paragraph 0074
(2022/01/04)
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- Isotruxene-based porous polymers as efficient and recyclable photocatalysts for visible-light induced metal-free oxidative organic transformations
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Two new isotruxene-based porous polymers were prepared and demonstrated to be highly efficient, metal-free heterogeneous photocatalysts for oxidative transformations using air as the mild oxidant under visible-light irradiation. Both catalysts show excellent recyclability. In addition, the reactions can be performed in water, further indicating the greenness of this method. This journal is
- Zhang, Haowen,Zhang, Xiao,Zheng, Ying,Zhou, Cen
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supporting information
p. 8878 - 8885
(2021/11/27)
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- Highly selective reductive catalytic fractionation at atmospheric pressure without hydrogen
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Reductive catalytic fractionation (RCF) is an efficient and selective way to produce phenolic monomers from lignin. However, this strategy is difficult to scale up due to its high operating pressure. In this work, we investigated RCF reaction at or near atmospheric pressure and without the use of hydrogen. The atmospheric RCF (ARCF) was conducted in acidified ethylene glycol in glass vessels at 185-195 °C catalyzed by 5% Ru/C. The products mainly include propylguaiacol and propylsyringyl (up to 95.6% among the lignin monomers) and do not contain propanolguaiacol, propanolsyringyl, or H monomers. Although the total yield of lignin monomers in ARCF is about one-quarter less than that of RCF, the operation of ARCF is much easier, milder, safer, and cheaper due to the atmospheric condition and the feasibility of the semi-continuous operation.
- Ren, Tianyu,You, Shengping,Zhang, Zhaofeng,Wang, Yuefei,Qi, Wei,Su, Rongxin,He, Zhimin
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supporting information
p. 1648 - 1657
(2021/03/09)
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- Eco-friendly preparation of ultrathin biomass-derived Ni3S2-doped carbon nanosheets for selective hydrogenolysis of lignin model compounds in the absence of hydrogen
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Lignin is an abundant source of aromatics, and the depolymerization of lignin provides significant potential for producing high-value chemicals. Selective hydrogenolysis of the C-O ether bond in lignin is an important strategy for the production of fuels and chemical feedstocks. In our study, catalytic hydrogenolysis of lignin model compounds (β-O-4, α-O-4 and 4-O-5 model compounds) over Ni3S2-CS catalysts was investigated. Hence, an array of 2D carbon nanostructure Ni3S2-CSs-X-Yderived catalysts were produced using different compositions at different temperatures (X= 0 mg, 0.2 mg, 0.4 mg, 0.6 mg, and 0.8 mg; Y = 600 °C, 700 °C, 800 °C, and 900 °C) were prepared and applied for hydrogenolysis of lignin model compounds and depolymerization of alkaline lignin. The highest conversion of lignin model compounds (β-O-4 model compound) was up to 100% and the yield of the obtained corresponding ethylbenzene and phenol could achieve 92% and 86%, respectively, over the optimal Ni3S2-CSs-0.4-700 catalyst in iPrOH at 260 °C without external H2. The 2D carbon nanostructure catalysts performed a good dispersion on the surface of the carbon nanosheets, which facilitated the cleavage of the lignin ether bonds. The physicochemical characterization studies were carried out by means of XRD, SEM, TEM, H2-TPR, NH3-TPD, Raman and XPS analyses. Based on the optimal reaction conditions (260 °C, 4 h, 2.0 MPa N2), various model compounds (β-O-4, α-O-4 and 4-O-5 model compounds) could also be effectively hydrotreated to produce the corresponding aromatic products. Furthermore, the optimal Ni3S2-CSs-0.4-700 catalyst could be carried out in the next five consecutive cycle experiments with a slight decrease in the transformation of lignin model compounds.
- Chen, Changzhou,Jiang, Jianchun,Li, Jing,Liu, Peng,Wu, Dichao,Xia, Haihong,Zhou, Minghao
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p. 3090 - 3103
(2021/05/07)
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- Synergistic effect of Ni-Co alloying on hydrodeoxygenation of guaiacol over Ni-Co/Al2O3 catalysts
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The hydrodeoxygenation (HDO) of guaiacol was investigated in a batch reactor using Ni-Co/γ-Al2O3 catalysts prepared by co-impregnation method. The structural and physicochemical properties of the catalysts were investigated using BET, XRD, H2-TPR, FT-IR, and NH3-TPD. The characterization results revealed that the formation of various Ni-Co composite species strongly depend on the Ni/Co mole ratio, total metal loadings, and the calcination/reduction temperature. The 6.1Ni3.05CoAl (Ni/Co = 1:2) catalyst seeds the formation of NiCo2O4 spinel structure and subsequent formation of Ni-Co alloy, which represents as specific active site for direct demethoxylation/deoxygenation reaction. The synergistic interaction of Ni-Co enhances the selectivity of benzene. The benzene selectivity of 35.2 % and cyclohexane selectivity of 59.1 % with complete conversion of guaiacol (98.9 %) were achieved with the 3.05Ni6.1CoAl catalyst at 575 K. A tentative reaction pathway is proposed based on the product distribution accomplished during HDO reaction. The structural property was correlated with activity to explore the mechanistic insights.
- Raikwar, Deepak,Majumdar, Saptarshi,Shee, Debaprasad
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- Role of Catalyst Support's Physicochemical Properties on Catalytic Transfer Hydrogenation over Palladium Catalysts
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Catalytic transfer hydrogenation (CTH) is a promising reaction for valorisation of bio-based feedstocks via hydrogenation without needing to use H2. Unlike standard hydrogenation, CTH occurs via dehydrogenation (DHD) of a hydrogen donor (H-donor) and hydrogenation (HYD) of a substrate. Therefore, the “ideal” CTH catalyst must balance the catalysis of both reactions to maximize the hydrogen transfer between H-donor and substrate with minimal H2 loss to gas (high atom efficiency). Additionally, the H-donor must be highly stable to prevent secondary reactions with the substrate. Herein we study the impact of the catalyst's properties on CTH of guaiacol using bicyclohexyl, a liquid organic hydrogen carrier, as a H-donor. The reaction was promoted by palladium dispersed on three typical support materials (γ-Al2O3, MgO, and SiO2). The performance of these catalysts in the conversion of bicyclohexyl and guaiacol was evaluated, allowing to estimate the H-transfer efficiency, as well as the potential for recycling the spent H-donor (bicyclohexyl). The apparent activation energies for DHD of bicyclohexyl and HYD of guaiacol revealed that slow DHD combined with fast HYD, as is the case with Pd/MgO, favours hydrogen transfer efficiency and selectivity towards hydrogenated products. In addition, an investigation of the DHD of bicyclohexyl and HYD of guaiacol independently showed that the affinity between the organic molecules and the support significantly impacts CTH. Indeed, Pd/SiO2 was highly active for both reactions individually and almost inactive for CTH. Consequently, these findings highlight the importance of the interaction between solvent-substrate-support in designing catalysts for transfer hydrogenation.
- Batalha, Nuno,Fraga, Gabriel,Hasan, M. D.,Konarova, Muxina,Laycock, Bronwyn,Pratt, Steven,Santos, Mirella S.
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p. 5191 - 5202
(2021/10/29)
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- Vapor-phase hydrodeoxygenation of lignin-derived bio-oil over Al-MCM-41 supported Pd-Co and Pd-Fe catalysts
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Fast pyrolysis of lignocellulosic biomass is an attractive process to produce bio-oil as an alternative liquid fuel source. Upgrading of bio-oil via hydrodeoxygenation (HDO) is an important route to accomplish this renewable energy production process. Al-MCM-41 supported Pd, Co and Fe catalysts were evaluated for HDO of guaiacol and lignin-derived bio-oil at atmospheric pressure in a fixed-bed reactor. Bimetallic Pd-Co and Pd-Fe catalysts showed higher HDO yield and stability than the monometallic Co and Fe catalysts. The addition of Pd significantly enhanced the stability of Co and Fe catalysts since it helped reduce the coke formation. The lignin-derived bio-oil mainly contained phenolic compounds which had one to three oxygen atoms. The catalytic upgrading could not only eliminate significantly the oxygen of these phenolic compounds but also reduce the amount of tar and heavy components. Pd-Fe catalyst was recognized as a suitable catalyst for upgrading of lignin-derived bio-oil since it produced more deoxygenated products and less gas-phase yield than Pd-Co catalyst.
- Tran, Nga T.T.,Uemura, Yoshimitsu,Ramli, Anita,Trinh, Thanh H.
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- Method for hydrolyzing diarylether compound to generate aryl phenol compound
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The invention discloses a method for hydrolyzing a diarylether compound to generate an arylphenol compound. According to the method, visible light is utilized to excite a photosensitizer for catalysis. In a reaction solvent, the raw material in the formula (1) breaks a C (sp2)-O bond under the auxiliary action of acid, and hydrolysis is performed to obtain the bimolecular aryl phenol compounds in the formula (3) and the formula (4). The method can catalyze the reaction at room temperature, is green and environment-friendly, and is easy to operate; the universality is wide, the reaction yield is relatively high, and the tolerance of functional groups is strong; the synthesis method not only can realize small-scale hydrolysis conversion of various diarylether compounds, but also can realize hydrolysis of herbicidal ether, triclosan and a lignin template substrate, and even can realize large-scale hydrolysis of triclosan and the lignin template substrate to realize gram-level degradation. A new strategy is provided for recovering phenol derivatives through lignin hydrolysis, degrading pesticides and purifying wastewater containing a degerming agent or herbicide. The method has wide application prospect and use value.
- -
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Paragraph 0107-0110
(2021/09/29)
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- Optimizing the carburization conditions of supported rhenium carbide for guaiacol conversion
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The present work evaluates the effect of ethylene content of a carburization mixture on the formation of carburized rhenium supported on activated carbon. The resulting catalysts were characterized by N2 physisorption, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and temperature-programmed reduction, and the results show a strong effect on the final phase obtained. A high amount of ethylene inhibited the carburization process, resulting in carbon formation, while a lower amount (≤ 35 %) of ethylene was favorable to the formation of the carbide phase. The catalysts were evaluated for the hydrodeoxygenation (HDO) of guaiacol, a bio-oil model compound, and a high yield of benzene (50 %), a desirable aromatic compound, was obtained at complete conversion over the catalysts containing the carbide phase.
- Blanco, Elodie,Dongil, Ana Belén,Escalona, Néstor,García-Fierro, Jose Luis,Ghampson, I. Tyrone
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- Heterogeneous Fenton-like oxidative degradation of sulfanilamide catalyzed by RuO2-rectorite composite
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RuO2-rectorite (RuO2-Rec) was prepared by intercalation, deposition and calcination. Its structure was characterized by XRD, XPS, SEM and EDS. It was used as a catalyst for the sulfanilamide (SA) degradation in the presence of H2O2. Unlike sodium-rectorite and RuO2 which couldn’t catalyze the degradation of SA, RuO2-Rec could effectively catalyze the decomposition of H2O2 into hydroxyl radicals to degrade SA. The degradation rate could reach ~ 100% under the optimal conditions of 58?μmol/L of SA, 1.16?mmol/L of H2O2, 0.133?g/L of RuO2-Rec, pH 3.5 and 25?°C in 5?h. The degradation process conformed to pseudo-first-order kinetic correlation. This degradation was affected by pH, the amount of RuO2-Rec and the concentrations of H2O2 and SA. However, under the optimal pH value of 3.5, a high degradation rate could be achieved with the increase in SA concentration from 58?μmol/L to 290?μmol/L as long as the optimal ratio of RuO2-Rec, H2O2 and SA kept unchanged. In addition, RuO2-Rec was stable and possessed low ruthenium leaching rate and excellent reusability. Therefore, RuO2-Rec is expected to be an active catalyst for the pollutant removal in the heterogeneous Fenton-like system.
- Pan, Feifei,Yang, Jianhong,Cai, Jun,Liu, Lianye
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p. 4595 - 4611
(2021/07/26)
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- RETRACTED ARTICLE: Selective photocatalytic conversion of guaiacol using g-C3N4 metal free nanosheets photocatalyst to add-value products
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Valorization of lignin into high valuable chemical is a critical challenge. Its availability is a key factor for the development of viable lignocellulosic processes to replace fossil derived compounds. In this work, new insights on the high photocatalytic conversion of guaiacol (82%) as a lignin model compound was achieved, also, high selectivity to p-benzoquinone (59%), catechol (27%), and pyrogallol (6%) was obtained using metal-free pyrolyzed g-C3N4 under visible light irradiation. To highlight the new insights, experimental parameters were modified to control the reaction mechanism to increase selectivity and photo-conversion. g-C3N4 photocatalyst was synthesized through urea calcination at 550 °C and the photocatalytic performance was assessed in terms of pyrolysis time, where higher time resulted in better photocatalytic activity. This effect was attributed to smaller structures and therefore better quantum confinement of the charges. The oxidation was promoted by [rad]OH radicals, which were detected through EPR operando mode and the addition of radical scavengers. A reaction pathway was proposed, in which the ·OH attacks guaiacol through a methoxy group. The photocatalytic reaction can be tuned using external oxidant agents such as O2 and/or H2O2 to promote certain radical formation, enhancing conversion rates and promoting selectivity for a specific product, where yield shifting from p-benzoquinone to pyrogallol was experimentally observed.
- Rojas,Espinoza-Villalobos,Salazar,Escalona,Contreras,Melin,Laguna-Bercero,Sánchez-Arenillas,Vergara,Caceres-Jensen,Rodriguez-Becerra,Barrientos
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- Protodeboronation of (Hetero)Arylboronic Esters: Direct versus Prehydrolytic Pathways and Self-/Auto-Catalysis
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The kinetics and mechanism of the base-catalyzed hydrolysis (ArB(OR)2→ ArB(OH)2) and protodeboronation (ArB(OR)2→ ArH) of a series of boronic esters, encompassing eight different polyols and 10 polyfluoroaryl and heteroaryl moieties, have been investigated by in situ and stopped-flow NMR spectroscopy (19F,1H, and11B), pH-rate dependence, isotope entrainment,2H KIEs, and KS-DFT computations. The study reveals the phenomenological stability of boronic esters under basic aqueous-organic conditions to be highly nuanced. In contrast to common assumption, esterification does not necessarily impart greater stability compared to the corresponding boronic acid. Moreover, hydrolysis of the ester to the boronic acid can be a dominant component of the overall protodeboronation process, augmented by self-, auto-, and oxidative (phenolic) catalysis when the pH is close to the pKaof the boronic acid/ester.
- Hayes, Hannah L. D.,Wei, Ran,Assante, Michele,Geogheghan, Katherine J.,Jin, Na,Tomasi, Simone,Noonan, Gary,Leach, Andrew G.,Lloyd-Jones, Guy C.
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supporting information
p. 14814 - 14826
(2021/09/13)
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- Organic amine mediated cleavage of Caromatic-Cαbonds in lignin and its platform molecules
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The activation and cleavage of C-C bonds remains a critical scientific issue in many organic reactions and is an unmet challenge due to their intrinsic inertness and ubiquity. Meanwhile, it is crucial for the valorization of lignin into high-value chemicals. Here, we proposed a novel strategy to enhance the Caromatic-Cα bond cleavage by pre-functionalization with amine sources, in which an active amine intermediate is first formed through Markovnikov hydroamination to reduce the dissociation energy of the Caromatic-Cα bond which is then cleaved to form target chemicals. More importantly, this strategy provides a method to achieve the maximum utilization of the aromatic nucleus and side chains in lignin or its platform molecules. Phenols and N,N-dimethylethylamine compounds with high yields were produced from herbaceous lignin or the p-coumaric acid monomer in the presence of industrially available dimethylamine (DMA). This journal is
- Cheng, Xiaomeng,Dong, Minghua,Han, Buxing,Liu, Huizhen,Liu, Shulin,Shen, Xiaojun,Wang, Zhenpeng,Xin, Yu,Yang, Junjuan
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p. 15110 - 15115
(2021/12/04)
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- Surface engineering of carbon supported CoMoS– an effective nanocatalyst for selective deoxygenation of lignin derived phenolics to arenes
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We report a viable synthesis route to prepare Co promoted MoS2 nanocatalyst supported on an activated carbon for the selective hydrodeoxygenation of lignin derived phenolics in a liquid phase. The key aspect of this strategy is to use activated carbon as support with weak metal-support interaction that promotes the formation of Co-Mo-S phase, which is inhibited in alumina supported CoMoS2 due to the strong metal-support interaction. The as-synthesized catalyst contained Co9S8 and MoS2 phases dispersed on the support, which during reduction at 450 °C formed Co-Mo-S phase that is active for deoxygenation. To validate the claim, the activity of the reduced catalyst was compared with the unreduced catalyst for guaiacol conversion. As such 92 % softwood lignin was converted after 5 h reaction time, producing 76 % liquids with 75 % deoxygenation. The loss of catalytic activity after five catalytic cycles was attributed to the reduction in catalyst surface area, sulphur leaching and metal sintering.
- Beltramini, Jorge,Kumar, Krishnapillai Girish,Mukundan, Swathi,Ravindran, Devika Sudha
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- METHOD OF ENHANCED AROMATIC SELECTIVITY FOR GAS PHASE DEOXYGENATION OF BIO-OILS
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Methods for gas-phase deoxygenation of a bio-oil are provided. In embodiments, such a method comprises exposing a bio-oil vapor comprising hydrocarbon compounds having oxygenated aromatic groups, to hydrogen gas in the presence of catalyst under conditions to induce deoxygenation of the oxygenated aromatic groups to provide a deoxygenated aromatic species, wherein the catalyst is a transition metal-incorporated mesoporous silicate having platinum deposited thereon and the transition metal is selected from Nb, W, Zr, and combinations thereof. The transition metal-incorporated mesoporous silicate catalysts are also provided.
- -
-
Paragraph 0009; 0040; 0041
(2021/01/23)
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- Anchimerically Assisted Selective Cleavage of Acid-Labile Aryl Alkyl Ethers by Aluminum Triiodide and N, N-Dimethylformamide Dimethyl Acetal
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Aluminum triiodide is harnessed by N,N-dimethylformamide dimethyl acetal (DMF-DMA) for the selective cleavage of ethers via neighboring group participation. Various acid-labile functional groups, including carboxylate, allyl, tert-butyldimethylsilyl (TBS), and tert-butoxycarbonyl (Boc), suffer the conditions intact. The method offers an efficient approach to cleaving catechol monoalkyl ethers and to uncovering phenols from acetal-type protecting groups such as methoxymethyl (MOM), methoxyethoxymethyl (MEM), and tetrahydropyranyl (THP) chemoselectively.
- Sang, Dayong,Yue, Huaxin,Zhao, Zhengdong,Yang, Pengtao,Tian, Juan
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p. 6429 - 6440
(2020/07/14)
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- Selective ether bond breaking method of aryl alkyl ether
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The invention discloses a selective aryl alkyl ether cracking method, which comprises that aryl alkyl ether, aluminum iodide and an additive are subjected to a selective ether bond cleavage reaction in an organic solvent at a temperature of -20 DEG C to a reflux temperature to generate phenol and derivatives thereof. The method is mild in condition and simple and convenient to operate, is suitablefor cracking aryl alkyl ether containing o-hydroxyl and o-carbonyl and acetal ether, and can also be used for removing tertiary carbon hydroxyl protecting groups with higher steric hindrance, such astriphenylmethyl, tertiary butyl and the like.
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-
Paragraph 0097-0099
(2020/09/16)
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- Zeolite encapsulated Ni(ii) Schiff-base complexes: improved catalysis and site isolation
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Two series of zeolite encapsulated Ni(ii) Schiff-base complexes,i.e., the Ni(ii) sal-1,2-phen and Ni(ii) sal-1,3-phen series, have been synthesized in neat and encapsulated states and characterized by using different characterization techniques such as XRD, SEM-EDS, BET, thermal analysis, XPS, IR spectroscopy, UV-vis spectroscopy and magnetic studies. UV-vis spectroscopy, XPS and magnetic studies all together reveal the structural modification of the guest complex and, thereby, the adaptation of electron density around the metal center upon encapsulation. However, encapsulation causes structural alterations for these two series differently and, hence, introduces a certain level of proficiency to these Ni(ii) complexes as catalysts for phenol oxidation reaction. However, analysis of catalytic data emphasizes site isolation as a major governing factor for the improved reactivity over the modified electron density around the metal center for phenol oxidation reaction where the heterogeneous mode of catalysis is concerned.
- Kumari, Susheela,Ray, Saumi
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supporting information
p. 14953 - 14963
(2020/09/23)
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- The role of acid and metal sites in hydrodeoxygenation of guaiacol over Ni/Beta catalysts
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Hydrodeoxygenation (HDO) of guaiacol over Ni metal supported on zeolites (H-Beta and H-ZSM-5) with different Si/Al ratios (12.5, 25, 175) and different metal loadings (2.3-23.4 wt%) was investigated in order to elucidate the role of catalyst acidity and the structure of Ni in the HDO reaction. Results show that the deoxygenation activity and product selectivity depend on the choice of support (acidity, pore size), level of metal loading, and reaction conditions. Guaiacol was deoxygenated in the presence of hydrogen with a maximum cyclohexane yield of 76% at a guaiacol conversion level of 100% over 15.7 wt% Ni/Beta-12.5 catalyst. Compared to Ni/ZSM-5 catalysts, Ni/Beta catalysts with mesopores facilitated the formation of coupling products (1,1′-bicyclohexyl). Under differential reaction conditions, we observed a linear relationship between deoxygenation activity and concentration of acid sites. Over catalysts containing small Ni particles, cyclohexane was formed as a result of a consecutive reduction of guaiacol to catechol and cyclohexane. At higher Ni-loading and consequently larger Ni particles, the selectivity towards cyclohexane increases with increased Ni loading. A higher concentration of nickel hydrides compared to smaller Ni sites was observed by H2-TPD and H2-FTIR over larger Ni species, and the nickel hydrides are believed to be crucial intermediates in the hydrogenation reaction. The 15.7 wt% Ni/Beta (Si/Al = 12.5) exhibits a promising HDO activity due to its good synergistic effect of hydrogenation and deoxygenation functions (high concentration nickel hydrides of and acid sites). In addition, based on the product distribution over catalysts containing mainly small Ni species and the Ni nanoparticles, two different reaction pathways were proposed, and the role of the acid sites and metal sites for each reaction route was discussed.
- Adesina, Adesoji,Kennedy, Eric,Li, Molly Meng-Jung,Setiawan, Adi,Stockenhuber, Michael,Yan, Penghui,Zhao, Guangyu
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p. 810 - 825
(2020/02/27)
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- Br?nsted Acid Catalyzed Tandem Defunctionalization of Biorenewable Ferulic acid and Derivates into Bio-Catechol
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An efficient conversion of biorenewable ferulic acid into bio-catechol has been developed. The transformation comprises two consecutive defunctionalizations of the substrate, that is, C?O (demethylation) and C?C (de-2-carboxyvinylation) bond cleavage, occurring in one step. The process only requires heating of ferulic acid with HCl (or H2SO4) as catalyst in pressurized hot water (250 °C, 50 bar N2). The versatility is shown on a variety of other (biorenewable) substrates yielding up to 84 % di- (catechol, resorcinol, hydroquinone) and trihydroxybenzenes (pyrogallol, hydroxyquinol), in most cases just requiring simple extraction as work-up.
- Bal, Mathias,Bomon, Jeroen,Liao, Yuhe,Maes, Bert U. W.,Sels, Bert F.,Sergeyev, Sergey,Van Den Broeck, Elias,Van Speybroeck, Veronique
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p. 3063 - 3068
(2020/02/05)
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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; 0068-0069; 0085-0106
(2020/12/08)
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- The development of a Cu(I)/pyrazolylpyridineamine catalyst system for the hydroxylation of aryl halides
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A catalyst system comprising of pyrazolylpyridineamine/Cu(I)/CsOH is reported. for the hydroxylation of aryl iodides and bromides with moderate to outstanding yields, without the use of an inert atmosphere. A comprehensive parameter optimisation study established optimum component concentrations: [Cu(MeCN)4]BF4 and 2-(1H-pyrazol-1-yl)-N-(pyridine-2-ylmethyl)ethan-1-amine (L01) (2 mol %), substrate (1 mmol), CsOH (4 mmol) and DMSO:H2O (1:1, 3 mL). Monitoring substrate conversion as a function of time revealed an induction period of 90 min, which could be eliminated through the initial in situ formation of the proposed [(L01)Cu-OH] intermediate. Eliminating the induction period resulted in complete conversion within one hour, with turnover numbers exceeding that of the benchmark catalyst system operating at an optimal catalyst loading of 0.05 mol %.
- Marais, Lindie,Vosloo, Hermanus C.M.,Swarts, Andrew J.
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- Carbon nanotubes as catalysts for wet peroxide oxidation: The effect of surface chemistry
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Three magnetic carbon nanotube (CNT) samples, named A30 (N-doped), E30 (undoped) and E10A20 (selectively N-doped), synthesized by catalytic chemical vapor deposition, were modified by introducing oxygenated surface groups (oxidation with HNO3, samples CNT-N), and by heat treatment at 800 °C for the removal of surface functionalities (samples CNT-HT). Both treatments lead to higher specific surface areas. The acid treatment results in more acidic surfaces, with higher amounts of oxygenated species being introduced on N-doped surfaces. Heat-treated samples are less hydrophilic than those treated with nitric acid, heat treatment leading to neutral or basic surfaces, only N-quaternary and N-pyridinic species being found by XPS on N-doped surfaces. These materials were tested in the catalytic wet peroxide oxidation (CWPO) of highly concentrated 4-nitrophenol solutions (4-NP, 5 g L?1) at atmospheric pressure, T = 50 °C and pH = 3, using a catalyst load of 2.5 g L?1 and the stoichiometric amount of H2O2 needed for the complete mineralization of 4-NP. The high temperature treatment enhanced significantly the activity of the CNTs towards CWPO, evaluated in terms of 4-NP and total organic carbon conversion, due to the increased hydrophobicity of their surface. In particular, E30HT and E10A20HT were able to remove ca. 100% of 4-NP after 8 h of operation. On the other hand, by treating the CNTs with HNO3, the activity of the less hydrophilic samples decreased upon increasing the concentration of surface oxygen-containing functionalities, whilst the reactivity generated inside the opened nanotubes improved the activity of the highly hydrophilic A30 N.
- Martin-Martinez, Maria,Machado, Bruno F.,Serp, Philippe,Morales-Torres, Sergio,Silva, Adrián M.T.,Figueiredo, José L.,Faria, Joaquim L.,Gomes, Helder T.
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p. 332 - 340
(2019/03/17)
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- In-situ fabrication of 0D/2D NiO/Bi12O17Cl2 heterojunction towards high-efficiency degrading 2, 4-dichlorophenol and mechanism insight
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2, 4-dichlorophenol (2, 4-DCP) as a persistent pollutant is frequently detected in water environments, complete eradication of trace which in water is an important task. Hence, a 0D/2D NiO/Bi12O17Cl2 heterojunction was achieved by in-situ fabrication of NiO nanodots on Bi12O17Cl2 nanosheets, which obviously improved the physical, optical and photoelectrochemical properties. The photocatalytic degradation activity of 0D/2D NiO/Bi12O17Cl2 heterojunction was boosted dramatically, which originated from the improved transfer and separation efficiency of charge carriers owing to the formation of Z-scheme heterostructure between NiO and Bi12O17Cl2. The possible photocatalytic reaction mechanism including migration behaviors of charge carriers, generation of reactive species and degradation intermediate products were revealed in depth. This work provides the valuable experiences for designing and fabricating otherwise 0D/2D heterojunction photocatalysts in the application of environmental treating fields.
- Song, Ning,Li, Jiaming,Li, Chunmei,Zhou, Pengjie,Jiang, Enhui,Zhang, Xiaoxu,Liu, Chunbo,Wu, Zhichen,Zheng, Hang,Che, Guangbo,Dong, Hongjun
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- Low-Temperature Catalytic Hydrogenolysis of Guaiacol to Phenol over Al-Doped SBA-15 Supported Ni Catalysts
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Selective hydrogenolysis of aromatic carbon-oxygen (Caryl?O) bonds is a key strategy for the generation of aromatic chemicals from lignin. However, this process is usually operated at high temperatures and pressures over hydrogenation catalysts, resulting in a low selectivity for aromatics and an extra consumption of hydrogen. Here, a series of Al-doped SBA-15 mesoporous materials with different Si/Al molar ratios (Al-SBA-15) were prepared via a post-synthesis method using NaAlO2 as the Al source, and then Al-SBA-15 supported Ni catalysts (Ni/Al-SBA-15) were prepared by a deposition-precipitation method using urea as the hydrolysis reagent. The prepared supports and catalysts were extensively characterized using various techniques such as XRD, N2 adsorption/desorption, TEM, 27Al NMR, NH3-TPD, XPS, H2-TPR, and pyridine-FT-IR, and the catalysts were evaluated in the hydrogenolysis of the Caryl?O bond in guaiacol and lignin derived compounds under mild conditions. The effects of the Si/Al ratio in catalyst and reaction parameters on guaiacol conversion and product distribution were investigated in detail, associated with solvent effect. The incorporation of Al into the framework of SBA-15 can improve the Lewis acidity and the dispersion of the supported Ni particles and yet modulate the metal-support interactions, which are propitious to the hydrogenolysis of the Caryl?O bond in guaiacol. The catalyst Ni/Al-SBA-15 with a Si/Al molar ratio of 10 shows the best performance with a guaiacol conversion of 87.4 % and a phenol selectivity of 76.9 % under the mild conditions conducted, because of its proper acidity, suitable metal-support interactions, and high dispersion of the active species. The present study would stimulate research and development in multi-functional catalysts for the generation of valuable chemicals from biomass.
- Wang, Qiuyue,Chen, Yufang,Yang, Guanheng,Deng, Ping,Lu, Xinqing,Ma, Rui,Fu, Yanghe,Zhu, Weidong
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p. 4930 - 4938
(2020/08/26)
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- Borylative Heterocyclization without Air-Free Techniques
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In contrast to previously reported borylative heterocyclization methods, a reaction here proceeds without air-free techniques to access synthetically useful borylated thiophenes, benzothiophenes, and isocoumarins. A comparison of stability/decomposition rates in air of several catecholboronic ester (Bcat) compounds derived from different heterocycle cores showed a strong dependence on the heterocycle structure. Lessons learned from this comparison were then harnessed for the development of borylative heterocyclization reactions under ambient-atmosphere conditions and with wet solvent. In contrast to literature reports suggesting general moisture sensitivity, a subset of Bcat products resulting from this technique were chromatography-stable and directly isolable, obviating the requirement for an extra synthetic transformation into more stable boron species, such as pinacolboronic esters (Bpin), for isolation. The isolated Bcat products were amenable to various downstream functionalization reactions, including reactions that were not accessible with their better-known Bpin counterparts, showing the complementarity of Bcat reaction partners and expanding their known chemistry. These results suggest the value of conceptual revisitation of substitution and solvent influence on stability and isolability of organo-Bcat compound classes and lay the groundwork for development of additional practical borylative methods in air.
- Blum, Suzanne A.,Gao, Chao,Nakao, Shuichi
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p. 10350 - 10368
(2020/09/23)
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- Selective Vicinal Diiodination of Polycyclic Aromatic Hydrocarbons
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Vicinally diiodinated polycyclic aromatic hydrocarbons (I2-PAHs) are accessible from the corresponding diborylated B2-PAHs through boron/iodine exchange. The B2-PAHs have been prepared via twofold electrophilic borylation reactions templated by a vicinally disilylated benzene. Our protocol is applicable to fluorenes, acenes, annulated acenes, oligoaryls, and even [5]helicene. Using B2-naphthalene as the example, we have shown that the reaction scope can, in principle, be expanded to include the synthesis of vicinally dibrominated and dihydroxylated PAHs. The usefulness of the building blocks provided by our method in the field of optoelectronic materials was demonstrated by the successful conversion of I2-fluoranthene to the analogous doubly alkynylated fluoranthene emitter.
- Bolte, Michael,Jin, Tao,John, Alexandra,Kaehler, Tanja,Lerner, Hans-Wolfram,Wagner, Matthias
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supporting information
p. 5847 - 5851
(2020/09/09)
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- Structural features and antioxidant activities of Chinese quince (Chaenomeles sinensis) fruits lignin during auto-catalyzed ethanol organosolv pretreatment
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Chinese quince fruits (Chaenomeles sinensis) have an abundance of lignins with antioxidant activities. To facilitate the utilization of Chinese quince fruits, lignin was isolated from it by auto-catalyzed ethanol organosolv pretreatment. The effects of three processing conditions (temperature, time, and ethanol concentration) on yield, structural features and antioxidant activities of the auto-catalyzed ethanol organosolv lignin samples were assessed individually. Results showed the pretreatment temperature was the most significant factor; it affected the molecular weight, S/G ratio, number of β-O-4′ linkages, thermal stability, and antioxidant activities of lignin samples. According to the GPC analyses, the molecular weight of lignin samples had a negative correlation with pretreatment temperature. 2D-HSQC NMR and Py-GC/MS results revealed that the S/G ratios of lignin samples increased with temperature, while total phenolic hydroxyl content of lignin samples decreased. The structural characterization clearly indicated that the various pretreatment conditions affected the structures of organosolv lignin, which further resulted in differences in the antioxidant activities of the lignin samples. These results can be helpful for controlling and optimizing delignification during auto-catalyzed ethanol organosolv pretreatment, and they provide theoretical support for the potential applications of Chinese quince fruits lignin as a natural antioxidant in the food industry.
- Cheng, Xi-Chuang,Guo, Xin-Ran,Liu, Hua-Min,Liu, Yu-Lan,Qin, Zhao,Wang, Xue-De
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p. 4348 - 4358
(2020/09/22)
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- Metal-Free Direct Deoxygenative Borylation of Aldehydes and Ketones
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Direct conversion of aldehydes and ketones into alkylboronic esters via deoxygenative borylation represents an unknown yet highly desirable transformation. Herein, we present a one-step and metal-free method for carbonyl deoxy-borylation under mild conditions. A wide range of aromatic aldehydes and ketones are tolerated and successfully converted into the corresponding benzylboronates. By the same deoxygenation manifold with aliphatic aldehydes and ketones, we also enable a concise synthesis of 1,1,2-tris(boronates), a family of compounds that currently lack efficient synthetic methods. Given its simplicity and versatility, we expect that this novel borylation approach could show great promise in organoboron synthesis and inspire more carbonyl deoxygenative transformations in both academic and industrial settings.
- Huang, Chia-Yu,Li, Chao-Jun,Li, Jianbin,Qiu, Zihang,Wang, Haining
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supporting information
p. 13011 - 13020
(2020/09/01)
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- Efficiently self-healing boronic ester crystals
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The perception of organic crystals being rigid static entities is quickly eroding, and molecular crystals are now matching a number of properties previously thought to be unique to soft materials. Here, we present crystals of a boronate ester that encompass many of the elastic and plastic mechanical properties of polymers such as bending, twisting, coiling and highly efficient self-healing of up to 67%, while they maintain their long-range structural order. The approach utilizes the concept of dynamic covalent chemistry and proves it can be applied towards ordered materials. This work expands our current understanding of the properties of crystalline molecular materials, and it could have implications towards the development of mechanically robust organic crystals that are capable of self-repair for durable all-organic electronics and soft robotics.
- Al-Handawi, Marieh B.,Commins, Patrick,Karothu, Durga Prasad,Naumov, Pan?e,Raj, Gijo
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p. 2606 - 2613
(2020/03/23)
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