- Chlorine-nickel interactions in gas phase catalytic hydrodechlorination: Catalyst deactivation and the nature of reactive hydrogen
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The gas phase hydrodechlorination of chlorobenzene and 3-chlorophenol (where 473 K ≤ T ≤ 573 K) has been studied using a 1.5% w/w Ni/SiO2 catalyst which was also employed to promote the hydrogenation of benzene, cyclohexene and phenol. In the former two instances the catalyst was 100% selective in removing the chlorine substituent, leaving the aromatic ring intact. While the dechlorination of chlorobenzene readily attained steady state with no appreciable deactivation, the turnover of 3-chlorophenol to phenol was characterised by both a short and a long term loss of activity. Chlorine coverage of the catalyst surface under reaction conditions was probed indirectly by monitoring, via pH changes in an aqueous NaOH trap, HCI desorption after completion of the catalytic step. Contacting the catalyst with the chlorinated reactants was found to severely limit and, depending on the degree of contact, completely inhibit aromatic ring reduction although a high level of hydrodechlorination activity was maintained. Hydrogen temperature programmed desorption (TPD) reveals the existence of three forms of surface hydrogen which are tentatively assigned as: (i) hydrogen bound to the surface nickel; (ii) hydrogen at the nickel/silica interface; (iii) spillover hydrogen on the silica support. The effect of chlorine-nickel interactions on the resultant TPD profiles is presented and discussed. The (assigned) spillover hydrogen appears to be hydrogenolytic in nature and is responsible for promoting hydrodechlorination while the hydrogen that is taken to be chemisorbed on, and remains associated with, the surface nickel metal participates in aromatic hydrogenation. Hydrodechlorination proceeds via an electrophilic mechanism, possibly involving spillover hydronium ions. The experimental catalytic data are adequately represented by a kinetic model involving non-competitive adsorption between hydrogen and the chloroaromatic, where incoming chloroaromatic must displace the HCI that remains on the surface after the dechlorination step. Kinetic parameters extracted from the model reveal that chlorophenol has a higher affinity than chlorobenzene for the catalyst surface but the stronger interaction leads to a greater displacement of electron density at the metal site and this ultimately leads to catalyst deactivation.
- Shin, Eun-Jae,Spiller, Andreas,Tavoularis, George,Keane, Mark A.
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- Facile synthesis of CuCr2O4 spinel nanoparticles: A recyclable heterogeneous catalyst for the one pot hydroxylation of benzene
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A facile hydrothermal synthesis method is developed to prepare CuCr2O4 spinel nanoparticle catalysts with sizes between 25-50 nm. A detailed characterization of the material was carried out by XRD, ICP-AES, XPS, EXAFS, SEM, TEM, and TGA. XRD revealed the formation of a CuCr2O4 spinel phase and TEM showed the that particles size was 20-50 nm. The catalyst was highly active for the selective oxidation of benzene to phenol with H2O2. The influence of reaction parameters such as temperature, solvent, substrate to oxidant molar ratio, reaction time, etc. were investigated in detail. The reusability of the catalyst was tested by conducting the same experiments with the spent catalyst and it was found that the catalyst did not show any significant activity loss, even after 5 reuses. A benzene conversion of 72.5% with 94% phenol selectivity was achieved over this catalyst at 80 °C. However, significant H2O2 decomposition occurs on the catalyst, necessitating its usage in five-fold excess.
- Acharyya, Shankha S.,Ghosh, Shilpi,Adak, Shubhadeep,Sasaki, Takehiko,Bal, Rajaram
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- Debromination of 2,4,6-tribromophenol coupled with biodegradation
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The application effect of aluminium and their alloys and mixtures with nickel was studied for the complete hydrodebromination of 2,4,6-tribromophenol (TBP) to phenol in aqueous NaOH solution at room temperature. It was found that the Raney Al-Ni alloy can
- Weidlich, Tomas,Prokes, Lubomir,Pospisilova, Dagmar
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- Mixed-donor N,N,O-tridentate ligands for palladium-catalyzed Suzuki reactions
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Efficient Suzuki-Miyaura cross-coupling reactions of arylboronic acids with aryl halides catalyzed by Pd/N,N,O-tridentate ligands, using methanol as solvent and K3PO4 as base, afforded the corresponding cross-coupled biaryls in good to excellent yields. Springer Science+Business Media B.V. 2012.
- Zhou, Zhonggao,Du, Ziyi,Hu, Qiaosheng,Shi, Jicheng,Xie, Yongrong,Liu, Yulan
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- Photocatalytic degradation of 2,4-dichlorophenol with V2O5-TiO2 catalysts: Effect of catalyst support and surfactant additives
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Binary oxide catalysts with various weight percentage V2O5 loadings were prepared by solid-state dispersion and the nanocomposites were modified with surfactants. The catalysts were analyzed using X-ray diffraction, diffuse-reflectance spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, and N2 adsorption-desorption. The photocatalytic activities of the catalysts were evaluated in the degradation of 2,4-dichlorophenol under ultraviolet irradiation. The photocatalytic activity of 50 wt% V2O5-TiO2 (50V2O5-TiO2) was higher than those of pure V2O5, TiO2, and P25. Interactions between V2O5 and TiO2 affected the photocatalytic efficiencies of the binary oxide catalysts. Cetyltrimethylammonium bromide (CTAB) and hexadecyltrimethylammonium bromide (HTAB) significantly enhanced the efficiency of the 50V2O5-TiO2 catalyst. The highest percentage of 2,4-dichlorophenol degradation (100%) and highest reaction rate (2.22 mg/(L·min)) were obtained in 30 min with the (50V2O5-TiO2)-CTAB catalyst. It is concluded that the addition of a surfactant to the binary oxide significantly enhanced the photocatalytic activity by modifying the optical and electronic properties of V2O5 and TiO2.
- Sinirtas, Eda,Isleyen, Meltem,Soylu, Gulin Selda Pozan
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- Synthesis, structural characterization, and catalytic activity of IPrNi(styrene)2 in the amination of aryl tosylates
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A novel bis-styrene IPrNi0 derivative has been synthesized from the reaction of Ni(COD)2 and free 1,3-bis(2,6-diisopropylphenyl) imidazolidene (IPr) ligand in the presence of styrene. The complex has been characterized by spectroscopic data as well as by X-ray crystallography. Its catalytic performance in the amination reaction of aryl tosylates is also reported. The catalytic reactions proceed in a very selective manner, affording moderate to high yields of cross-coupling products in short reaction times at 110 °C.
- Iglesias, Maria Jose,Blandez, Juan F.,Fructos, Manuel R.,Prieto, Auxiliadora,Alvarez, Eleuterio,Belderrain, Tomas R.,Nicasio, M. Carmen
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- Spectroscopic and QM/MM investigations of Chloroperoxidase catalyzed degradation of orange G
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Chloroperoxidase (CPO), a heme-thiolate protein, from Caldariomyces fumago catalyzes a plethora of reactions including halogenation, dismutation, epoxidation, and oxidation. Although all CPO-catalyzed reactions go through a common intermediate, compound I, different mechanisms are followed in subsequent transformations. To understand the mechanism of CPO-catalyzed halide-dependent degradation of orange G, the role of halide and pH was systematically investigated. It is revealed that formation and protonation of compound X, a long-sought after hypochlorite heme adduct intermediate existed during CPO-catalyzed halide-dependent reactions, significantly lowers the reaction barrier and increases the efficiency of CPO-catalyzed orange G degradation. The extremely acidic optimal reaction pH suggests the protonation of a residue, presumably, Glu 183 in CPO catalysis. Halide dependent studies showed that Kcat is higher in the presence of Br- than in the presence of Cl-. The degradation products of orange G indicate the cleavage at a single position of orange G, demonstrating a high regioselectivity of CPO-catalyzed degradation. Based on our kinetic, NMR and QM/MM studies, the mechanism of CPO-catalyzed orange G degradation was proposed.
- Zhang, Rui,He, Qinghao,Huang, Yi,Wang, Xiaotang
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- Evidence for HOOO radicals in the formation of alkyl hydrotrioxides (ROOOH) and hydrogen trioxide (HOOOH) in the ozonation of C - H bonds in hydrocarbons
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Low-temperature ozonation of cumene (1a) in acetone, methyl acetate, and tert-butyl methyl ether at -70° C produced the corresponding hydrotrioxide, C6H5C(CH3)2OOOH (2a), along with hydrogen trioxide, HOOOH. Ozonation of triphenylmethane (1b), however, produced only triphenylmethyl hydrotrioxide, (C6H5)3COOOH (2b). These observations, together with the previously reported experimental evidence, seem to support the "radical" mechanism for the first step of the ozonation of the C - H bonds in hydrocarbons, i.e., the formation of the caged radical pair (R??OOOH), which allows both (a) collapse of the radical pair to ROOOH and (b) the abstraction of the hydrogen atom from alkyl radical R? by HOOO? to form HOOOH. The B3LYP/6-311++G(d,p) (ZPE) calculations revealed that HOOO radicals are considerably stabilized by forming intermolecularly hydrogen-bonded complexes with acetone (BE = 8.55 kcal/mol) and dimethyl ether (7.04 kcal/mol). This type of interaction appears to be crucial for the relatively fast reactions (and the formation of the polyoxides in relatively high yields) in these solvents, as compared to the ozonations run in nonbasic solvents. However, HOOO radicals appear to be not stable enough to abstract hydrogen atoms outside the solvent cage, as indicated by the absence of HOOOH among the products in the ozonolysis of triphenylmethane. The decomposition of alkyl hydrotrioxides 2a and 2b involves a homolytic cleavage of the RO-OOH bond with subsequent "in cage" reactions of the corresponding radicals, while the decomposition of HOOOH is most likely predominantly a "pericyclic" process involving one or more molecules of water acting as a bifunctional catalyst to produce water and singlet oxygen (Δ1O2).
- Cerkovnik, Janez,Erzen, Evgen,Koller, Joze,Plesnicar, Bozo
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- Solvent-Induced Single Crystal-Single Crystal Transformation of an Interpenetrated Three-Dimensional Copper Triazole Catalytic Framework
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The 2-fold interpenetrated 3D framework 1 can be solvent-induced to noninterpenetrated framework 1′ in a reversible single crystal-single crystal transformation fashion. In addition, 1′ represents the first catalyst based on triazole to catalyze the aerobic homocoupling of various substituted arylboronic acids.
- Wang, Ying,Meng, Shan-Shan,Lin, Peng-Xiang,Xiao, Yi-Wei,Ma, Qing-Qing,Xie, Qiong,Chen, Yuan-Yuan,Zhao, Xiao-Jun,Chen, Jun
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- 2,2,6,6-Tetramethylpiperidine-1-Oxyl-promoted hydroxylation of benzene to phenol over a vanadium-based catalyst using molecular oxygen
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Rapid benzene hydroxylation was achieved using a reaction system that consisted of a vanadium-based catalyst, ascorbic acid, and 2,2,6,6- tetramethylpiperidine-1-oxyl (TEMPO) with molecular oxygen as the oxidant. The hydroxyl radicals that form by a Fento
- Chen, Jiaqi,Gao, Shuang,Li, Jun,Lue, Ying
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- Photo-Fries rearrangement of 1-pyrenyl esters
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Photo-Fries rearrangement reactions of 1-pyrenyl esters were investigated. Photoreaction of 1-pyrenyl benzoate in benzene generates 1-hydroxy-2-pyrenyl phenyl ketone along with 1-pyrenol. The exceptionally down field 1H NMR chemical shift of OH proton in the photoproduct indicates the existence of intramolecular hydrogen bonding. Photorearrangements of analogs that have electron-withdrawing or electron-releasing group on the phenyl ring, and related heteroaromatic carboxylates also take place to form the corresponding ketones. However, photoreactions of 1-pyrenyl aliphatic carboxylate esters do not occur. The results of spectroscopic and theoretical studies suggest the mechanistic pathway for this process is initiated by homolytic C–O bond cleavage in an aroyl group localized 1(π → π?) excited state of the 1-pyrenyl esters. The radical pair generated in this fashion then undergoes in-solvent-cage coupling to yield the 1-hydroxy-2-pyrenyl aryl ketone selectively.
- Maeda, Hajime,Akai, Tomomi,Segi, Masahito
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- Electrochemical dechlorination of 4-chlorophenol to phenol
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We have hypothesized that hydrogen gas intercalated in a palladium lattice is the powerful reducing agent that reductively dechlorinates chlorinated organic compounds that are adsorbed on the surface of palladized electrodes. We have shown that dechlorination of 4-chlorophenol to phenol occurs rapidly on palladized carbon cloth or palladized graphite electrodes. The reactions on the palladized carbon cloth and graphite depend on the adsorption of the chlorinated organic compound on the carbon surface and the reaction with hydrogen at the palladium/carbon interface. Palladium was much more effective in promoting the dechlorination reaction than platinum, probably because of its ability to intercalate hydrogen in its lattice.
- Cheng, I. Francis,Fernando, Quintus,Korte, Nic
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- Selective enzymatic hydrolysis of phenolic acetates
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Phenolic acetates are selectively hydrolyzed in the presence of alkyl acetates, methyl esters and cinnamates with pig liver acetone powder (PLAP).
- Basavaiah,Raju
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- Direct hydroxylation of benzene to phenol over pyridine-modified vanadium-substituted heteropoly acid under microwave condition
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Direct oxidation of benzene to phenol over Py3PMo11V and hydrogen peroxide as the oxidant under microwave irradiation. Pyridine(Py)- modified vanadium substituted heteropoly acid (Py3PMo11V) with Keggin structur
- Liu,Hou
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- Vanadium oxyacetylacetonate grafted on UiO-66-NH2 for hydroxylation of benzene to phenol with molecular oxygen
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V/UiO-66-NH2 was prepared by the vanadium oxyacetylacetonate grafted on UiO-66-NH2. The catalytic performance of V/UiO-66-NH2 was investigated for the hydroxylation of benzene to phenol using O2. It can give the
- Wang, Weitao,Li, Na,Tang, Hao,Ma, Yangmin,Yang, Xiufang
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- Novel one-pot synthesis of 1-alkyl-2-(aryloxy)methyl-1H-pyrrolo[2,3-b]quinoxalines via copper-free Sonogashira coupling reaction
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Abstract: A novel, simple, and efficient protocol is described for the synthesis of 1-alkyl-2-(aryloxy)methyl-1H-pyrrolo[2,3-b]quinoxalines via the one-pot reaction of phenol or 2-naphthol derivatives, propargyl bromide, and N-alkyl-3-chloroquinoxaline-2-amines in the presence of palladium catalyst. This one-pot reaction is carried out in the absence of any copper salt at room temperature. The reaction product is dependent on the nature of the base used. The use of morpholine, as the base, affords the final cyclized product, and triethylamine only gives the coupling product. Graphical abstract: [Figure not available: see fulltext.].
- Keivanloo, Ali,Fakharian, Mahsa,Nabid, Mohammad Reza,Amin, Amir Hossein
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- Bronsted acid-functionalized choline chloride-butane sultone for the catalytic decomposition of cumene hydroperoxide to phenol
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Abstract: Choline chloride and 1,4-butane sultone were combined to obtain a sulphonic acid-functionalized ionic liquid. The structural properties of the ionic liquid were evaluated with AT-IR, NMR, mass and elemental analysis. The Bronsted acidity of the
- Padma priya,Rajarajeswari
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- Dramatic Effects Caused by Alkali Metal Salts on Hydrolytic Reaction Rates of Diaryl Ethers in Aqueous Solutions at High Temperatures (250 and 315 deg C)
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Variations in hydrolysis rates indicate that alkali metal halides and sodium sulfate behave as salts of strong bases and weak acids at high temperatures.
- Katritzky, Alan R.,Balasubramanian, Marudai,Siskin, Michael
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- Long-Lived Photoexcited State of a Mn(IV)-Oxo Complex Binding Scandium Ions That is Capable of Hydroxylating Benzene
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Photoexcitation of a MnIV-oxo complex binding scandium ions ([(Bn-TPEN)MnIV(O)]2+-(Sc(OTf)3)2) in a solvent mixture of trifluoroethanol and acetonitrile (v/v = 1:1) resulted in formation of the long-l
- Sharma, Namita,Jung, Jieun,Ohkubo, Kei,Lee, Yong-Min,El-Khouly, Mohamed E.,Nam, Wonwoo,Fukuzumi, Shunichi
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- Iron oxide mediated direct C-H arylation/alkylation at α-position of cyclic aliphatic ethers
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We report a new and efficient iron oxide catalyzed cross-coupling reaction between organometallic species such as alkyl/arylmagnesium halides or organolithium species and α-hydrogen bearing cyclic aliphatic ethers via activation of C(sp3)-H. This is the first example of iron oxide mediated direct C-C bond formation without expensive or toxic ligands.
- Singh, Parvinder Pal,Gudup, Satish,Ambala, Srinivas,Singh, Umed,Dadhwal, Sumit,Singh, Baldev,Sawant, Sanghapal D.,Vishwakarma, Ram A.
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- Trapping hydrogen sulfide (H2S) with diselenides: The application in the design of fluorescent probes
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Here we report a unique reaction between phenyl diselenide-ester substrates and H2S to form 1,2-benzothiaselenol-3-one. This reaction proceeded rapidly under mild conditions. Thiols could also react with the diselenide substrates. However, the resulted S-Se intermediate retained high reactivity toward H2S and eventually led to the same cyclized product 1,2-benzothiaselenol-3-one. Based on this reaction two fluorescent probes were developed and showed high selectivity and sensitivity for H2S. The presence of thiols was found not to interfere with the detection process.
- Peng, Bo,Zhang, Caihong,Marutani, Eizo,Pacheco, Armando,Chen, Wei,Ichinose, Fumito,Xian, Ming
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- Pathways and kinetics of anisole pyrolysis studied by NMR and selective 13C labeling. Heterolytic carbon monoxide generation
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By applying 13C and 1HNMR spectroscopy the pyrolysis of site-selectively 13C-enriched (H313CO 12C6H5) and normal anisole compounds was studied in the dark at 0.001-1.0M (M, mol dm-3) and at 400-600°C (supercritical conditions). Conversion of the 13C-labeled methyl group was confined to the methoxy-originated fragments, 13CO and 13CH4, and the reactive intermediate, H13CHO. The normal phenyl group, 12C6H5-was converted to benzene, 12C6H6 and phenol, 12C6H 5OH without ring disintegration. The pyrolysis consists of two elementary steps: (1) the ratedetermining unimolecular ether-bond fission (k1) to generate the fragmented product C6H6 and energized intermediate H 13CHO* through the intramolecular proton transfer from the methoxy group to the phenyl, and (2) the fast bimolecular disproportionation (k2) through the intermolecular proton/hydride transfer from H 13CHO* to H313COC6H 5 to produce 13CO, 13CH4, and C 6H5OH. CO is generation by the heterolytic (ionic) mechanism in contrast to the homolytic (radical) one via the phenoxy radical intermediate (C6H5O?) in the literature despite the agreement of the rate constant (k1) and the activation energy.
- Tsujino, Yasuo,Yasaka, Yoshiro,Matubayasi, Nobuyuki,Nakahara, Masaru
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- Reductive dechlorination of 2,4-dichlorophenol by Pd/Fe nanoparticles prepared in the presence of ultrasonic irradiation
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Palladium/Iron (Pd/Fe) nanoparticles were prepared by using ultrasound strengthened liquid phase reductive method to enhance dispersion and avoid agglomeration. The dechlorination of 2,4-dichlorophenol (2,4-DCP) by Pd/Fe nanoparticles was investigated to understand its feasibility for an in situ remediation of contaminated groundwater. Results showed that 2,4-DCP was first adsorbed by Pd/Fe nanoparticles, then quickly reduced to o-chlorophenol (o-CP), p-chlorophenol (p-CP), and finally to phenol (P). The induction of ultrasound during the preparation of Pd/Fe nanoparticles further enhanced the removal efficiency of 2,4-DCP, as a result, the phenol production rates increased from 65% (in the absence of ultrasonic irradiation) to 91% (in the presence of ultrasonic irradiation) within 2 h. Our data suggested that the dechlorination rate was dependent on various factors including Pd loading percentage over Fe0, Pd/Fe nanoparticles availability, temperature, mechanical stirring speed, and initial pH values. Up to 99.2% of 2,4-DCP was removed after 300 min reaction with these conditions: Pd loading percentage over Fe 0 0.3 wt.%, initial 2,4-DCP concentration 20 mg L-1, Pd/Fe dosage 3 g L-1, initial pH value 3.0, and reaction temperature 25 °C. The degradation of 2,4-DCP followed pseudo-first-order kinetics reaction and the apparent pseudo-first-order kinetics constant was 0.0468 min -1.
- Zhao, Deming,Li, Min,Zhang, Dexing,Baig, Shams Ali,Xu, Xinhua
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- Factors affecting sonolytic degradation of sulfamethazine in water
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In this study, the major factors affecting sonolytic degradation of sulfamethazine (SMT), a typical pharmaceutically active compound, in water were evaluated. The factors tested included two operational parameters (i.e. initial SMT concentration and ultrasonic power), three dissolved gases (i.e. Ar, O 2 and N2), five most frequently found anions in water (NO3-,Cl-,SO42-,HCO3-andBr-), ferrous ion (Fe 2+), and four alcohols (methanol, ethanol, isopropyl alcohol, tert-butyl alcohol). Typically, the degradation rate was increased with the increasing initial SMT concentration and power. The degradation rate was accelerated in the presence of argon or oxygen, but inhibited by nitrogen. Effects of anions on the ultrasonic treatment were species-dependent. The SMT degradation rate was slightly inhibited by NO3-,Cl-,and,SO42- but significantly improved by HCO3-andBr-. The negative effects of alcohols acted as hydroxyl radicals scavengers with the following order: tert-butyl alcohol > isopropyl alcohol > ethanol > methanol. The synergetic effect of ferrous ion was mainly due to production of additional hydroxyl radicals (·OH) through Fenton chemistry. LC/MS/MS analysis indicated that the degradation of SMT by ultrasonic irradiation is mainly ascribed to ·OH oxidation. Of interest, although the SMT could be rapidly degraded by ultrasonic irradiation, the degradation products were rarely mineralized. For example, ～100% of 180 μM SMT was decomposed, but only 8.31% TOC was reduced, within 2 h at an irradiation frequency of 800 kHz and a power of 100 W. However, the products became much biodegradable (BOD 5/COD was increased from 0.04 to 0.45). Therefore, an aerobic biological treatment may be an appropriate post-treatment to further decompose the SMT degradation products.
- Gao, Yu-Qiong,Gao, Nai-Yun,Deng, Yang,Gu, Jin-Shan,Gu, Yu-Liang,Zhang, Dong
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- Efficient visible-light-induced photocatalytic activity on gold-nanoparticle-supported layered titanate
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The visible-light-induced photocatalytic conversion of aqueous benzene to phenol on Au-nanoparticle-supported layered titanate was accelerated when the reaction was conducted in the presence of aqueous phenol.
- Ide, Yusuke,Matsuoka, Mizuki,Ogawa, Makoto
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- Ether Cleavage Re-Investigated: Elucidating the Mechanism of BBr3-Facilitated Demethylation of Aryl Methyl Ethers
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One of the most well-known, highly utilized reagents for ether cleavage is boron tribromide (BBr3), and this reagent is frequently employed in a 1:1 stoichiometric ratio with ethers. Density functional theory calculations predict a new mechanistic pathway involving charged intermediates for ether cleavage in aryl methyl ethers. Moreover, these calculations predict that one equivalent of BBr3 can cleave up to three equivalents of anisole, producing triphenoxyborane [B(OPh)3] prior to hydrolysis. These predictions were validated by gas chromatography analysis of reactions where the BBr3:anisole ratio was varied. Not only do we confirm that sub-stoichiometric equivalents may be used for ether demethylation, but the findings also support our newly proposed three cycle mechanism for cleavage of aryl methyl ethers.
- Kosak, Talon M.,Conrad, Heidi A.,Korich, Andrew L.,Lord, Richard L.
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- Preparation of salicylic nitrile through direct catalytic dehydration of salicylamide with immobilized phosphoric acid as catalyst
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Salicylic nitrile was prepared through direct catalytic dehydration of salicylamide under high temperature using immobilized phosphoric acid as catalyst. The catalytic performances of different catalysts were evaluated according to the analytic results of
- Yao, Shu-Feng,Cai, Zhao-Sheng,Huang, Xu-Juan,Song, Lan-Xuan
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- Temperature dependence of binding and catalysis for human serum arylesterase/paraoxonase
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The influence of temperature upon the hydrolysis of phenyl acetate, catalysed by purified human serum arylesterase/paraoxonase (E. C. 3.1.8.1), was studied in the temperature range 10 C-40 C by spectrophotometry in TRIS buffer, pH 8.0, using both initial rate analysis and progress curve analysis. The kinetic parameters (catalytic constant kcat; Michaelis constant Km; product inhibition constant Kp) were determined by nonlinear regression. All parameters increased with temperature, but the ratios kcat/Km and Kp/Km remained practically constant. Binding of both substrate and reaction product (phenol) was exothermic. A negative entropic term accounted for about 50% of the enthalpy change for both the binding and catalytic steps. Thermodynamic analysis suggested that: (1) the rate-limiting step is the nucleophilic attack of the carbonyl group of the substrate by a water molecule, (2) the active site is preorganized with no induced fit, (3) the enzyme-bound calcium plays an important role in stabilizing both the substrate and the transition state. The practical implications of these results are discussed.
- Debord, Jean,Bollinger, Jean-Claude,Harel, Michel,Dantoine, Thierry
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- Cu(II) catalyzed reaction between phenyl hydrazine and toluidine blue - dual role of acid
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The detailed kinetics of Cu(II) catalyzed reduction of toluidine blue (TB+) by phenyl hydrazine (Pz) in aqueous solution is studied. Toluidine white (TBH) and the diazonium ions are the main products of the reaction. The diazonium ion further decomposes to phenol (PhOH) and nitrogen. At low concentrations of acid, H+ ion autocatalyzes the uncatalyzed reaction and hampers the Cu(II) catalyzed reaction. At high concentrations, H+ hinders both the uncatalyzed and Cu(II) catalyzed reactions. Cu(II) catalyzed had stoichiometry similar to the uncatalyzed reaction, Pz+2 TB++H2O = PhOH+2 TBH+2 H++N2. Cu(II) catalyzed reaction occurs possibly through ternary complex formation between the unprotonated toluidine blue and phenyl hydrazine and catalyst. The rate coefficient for the Cu(II) catalyzed reaction is 2.1×104 M-2 s-1. A detailed 13-step mechanistic scheme for the Cu(II) catalyzed reaction is proposed, which is supported by simulations.
- Jonnalagadda,Nattar
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- BASE AND ACID CATALYZED REACTIONS OF PHENYLAZO 1-NAPHTHYL ETHER, A NEW REACTIVE DIAZOETHER. REPLY TO THE KEKULE'S MECHANISM FOR THE DIAZO COUPLING REACTION
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The base and acid catalyzed reactions of phenylazo 1-naphthyl ether (5) yielded biphenyl (8) and 1-naphthol (9) as major products accompanied with 4-phenylazo- (6) and 2-phenylazo-1-naphthols (7).All of our observations do not support the Kekule's diazo coupling mechanism.
- Tezuka, Takahiro,Sasaki, Katsunori,Ando, Setsuo
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- UV-controlled shape memory hydrogels triggered by photoacid generator
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Light-induced shape memory polymers represent a class of stimuli-responsive materials that can recover their permanent shapes from temporarily trapped ones upon exposure to light illumination. Although much effort has been devoted to developing various light-responsive shape memory polymers, fabrication of such a light-responsive shape memory hydrogel still remains a challenge compared to neat polymers in their dry state. Herein, we developed a facile and general strategy to endow conventional hydrogel systems with ultraviolet (UV)-controlled shape memory performance simply using a photoacid generator (PAG) as a trigger. The process involves shape fixity through coordination interaction between imidazole groups and metal ions, and shape recovery by switching off the complexation via PAG photolysis reaction which leads to the protonation of imidazole groups. Furthermore, this convenient strategy is proved to be applicable to other pre-existing hydrogels such as a boronate ester cross-linked melamine-poly(vinyl alcohol) (PVA) hydrogel. We believe this method could provide a new opportunity with regard to the design and practical application of light-controlled shape memory hydrogels.
- Feng, Wei,Zhou, Wanfu,Zhang, Shidong,Fan, Yujiao,Yasin, Akram,Yang, Haiyang
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- Catalytic dechlorination of chlorophenols in water by palladium/iron
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Three isomer chlorophenols, o-, m-, p-chlorophenol, were dechlorinated by palladium/iron powder in water through catalytic reduction. The dechlorinated reaction is believed to take place on the surface site of the catalyst in a pseudo-first-order reaction. The reduction product for all the three isomers is phenol. The dechlorination rate increases with increase of bulk loading of palladium due to the increase of both the surface loading of palladium and the total surface area. The molecular structure also has an effect on the dechlorination rate. For conditions with 0.048% Pd/Fe, the rate constants are 0.0215, 0.0155 and 0.0112min-1 for o-, m-, p-chlorophenol, respectively. Almost complete dechlorination is achieved within 5h. Copyright
- Liu, Yihui,Yang, Fenglin,Yue, Po Lock,Chen, Guohua
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- Polarographic behavior and determination of 1,1-dimethyl-3-phenyltriazene
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Polarographic behavior of the genotoxic substance 1,1-dimethyl-3- phenyltriazene was investigated and optimum conditions were found for its determination by sampled direct current polarography and differential pulse polarography at a static mercury drop electrode in the concentration range from 1 × 10-4 to 1 × 10-7 mol l-1. It was established that for reduction of the triazene group four electrons are required resulting in the formation of amino and hydrazo compound. The resulting products were identified, and the reduction pathway was proposed.
- Ignjatovic, Ljubisa M.,Barek, Jiri,Zima, Jiri,Markovic, Dragan A.
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- Preparation of phenolic compounds by decarboxylation of hydroxybenzoic acids or desulfonation of hydroxybenzenesulfonic acid, catalysed by electron rich palladium complexes
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Phenolic compounds can be prepared by catalytic decarboxylation of 4-hydroxybenzoic acid or desulfonation of 4-hydorxybenzene sulfonic acid. Palladium complexes are shown to be highly active in the decarboxylation reaction, but complexes of platinum or ru
- Nunez Magro, Angel A.,Eastham, Graham R.,Cole-Hamilton, David J.
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- Stable N-functionalised 'pincer' bis carbene ligands and their ruthenium complexes; synthesis and catalytic studies
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Deprotonation of 2,6-bis(arylimidazolium)pyridine dibromide with KN(SiMe3)2 gave thermally stable 2,6-bis(arylimidazol-2-ylidene)pyridine, which was further used to prepare ruthenium 'pincer' complexes; the latter show catalytic activity in transfer hydrogenation of carbonyl compounds.
- Danopoulos, Andreas A.,Winston, Scott,Motherwell, William B.
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- Ionic-liquid-functionalized polyoxometalates for heterogeneously catalyzing the aerobic oxidation of benzene to phenol: Raising efficacy through specific design
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By combining nitrile-tethered pyridinium-based ionic liquid dication with the polyoxometalate anion of Keggin H5PMo10V2O40 (PMoV2) through precipitation in aqueous solution, an organic-inorganic hybri
- Long, Zhouyang,Zhou, Yu,Ge, Weilin,Chen, Guojian,Xie, Jingyan,Wang, Qian,Wang, Jun
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- Pyrolysis and oxidation of anisole near 1000 K
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Experiments near 1000 K have revealed the thermal decomposition of anisole to proceed exclusively via homolysis of the O-CH3 bond. The anisole decay was observed to be first order even in the presence of oxygen. The distribution of reaction intermediates was virtually independent of equivalence ratio, φ ≡ ([anisole]/[O2])/([anisole]/[O2]) stoichiometric. Phenol, cresols, methylcyclopentadiene, and CO were major products. Minor species included benzene, cyclopentadiene, ethane, and methane. Trace yields of ethene, toluene, and naphthalenes were observed under all conditions; trace C2-C4 species including acetylene, allene, and 1,3-butadiene were observed only in the oxidation experiments. Oxidation occurs preferentially through methylcyclopentadiene. A multichannel reaction scheme is proposed involving the formation of a chemically activated adduct from phenoxy and methyl. The complex reacts to form primarily cresols and methylcyclopentadiene + CO either directly or subsequent to stabilization. A kinetic model for anisole pyrolysis has been developed to predict the disappearance of anisole and the production of reaction intermediates. Excellent agreement is obtained between experimental data and model predictions of anisole, CO, methylcyclopentadiene, and total phenolics.
- Pecullan,Brezinsky,Glassman
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- Hydroxylation of benzene to phenol by molecular oxygen over an organic-inorganic hybrid catalyst: Schiff base manganese complex attached to molybdovanadophosphoric heteropolyacid
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The organic-inorganic hybrid catalyst L-Mn-PMoV was prepared simply by combining a schiff base Mn complex (L-Mn, L: N,N-disalicylidene-1, 6-hexanediamine) with the Keggin-structured molybdovanadophosphoric heteropolyacid (PMoV). The proposed composition and structure of the catalyst were evidenced by TG, elemental analysis, FT-IR, and UV-Vis characterizations. Its catalytic performance was evaluated in the direct hydroxylation of benzene to phenol by molecular oxygen with ascorbic acid as the reducing agent. Various reaction parameters were changed to attain the optimal conditions. The hybrid catalyst has a formula [{Mn(C20H22N2O 2)(Cl)}2(H4PMo11VO40)], with the two terminal oxygen atoms in the PMoV Keggin structure coordinately linked to the two Mn(III) ions in two L-Mn units, respectively. It exhibits a remarkably enhanced yield to phenol compared to the pure PMoV due to the synergy effect between the Schiff-base manganese complex and PMoV. Graphical Abstract: [Figure not available: see fulltext.]
- Zhou, Changjiang,Wang, Jun,Leng, Yan,Ge, Hanqing
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- Synthetic and kinetic aspects of nickel-catalysed amination of allylic alcohol derivatives
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The design of efficient nickel-based catalytic systems for coupling of diethylamine (1) with esters and ether derivatives of allyl alcohol (2a-c) and related allyl-substituted compounds (4a-e) is reported. Special attention is paid to solvent and salt effects on catalytic activities and kinetic profiles for the formation of allyllamines. The results are discussed in terms of the influence of some reaction parameters (polarity, ion exchange processes, substrate) on the rate determining step of the catalytic cycle.
- Bricout, Herve,Carpentier, Jean-Francois,Mortreux, Andre
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- Active species formed in a Fenton-like system in the medium of triethylammonium acetate ionic liquid for hydroxylation of benzene to phenol
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High-valent iron(IV)-oxo species was proved to be the main oxidizing species for hydroxylation of benzene to phenol by a Fenton-like reagent in triethylammonium acetate ionic liquid via UV-vis and ESI-MS characterization, while hydroxyl radical was excluded by detailed investigations. It was found that the formation of hydroxyl radical was prohibited by the reduction of redox potential of Fe(III)/Fe(II) couple in triethylammonium acetate medium, leading to a decreased over-oxidation of benzene than that in aqueous solution. The reaction mechanisms for hydroxylation of benzene, as well as for over-oxidation of phenol by iron(IV)-oxo species were proposed. The latter is partly prohibited by the hydrogen-bond interaction between as-produced phenol and acetate anion of the ionic liquid.
- Hu, Xiaoke,Zhu, Liangfang,Wang, Xueqin,Guo, Bin,Xu, Jiaquan,Li, Guiying,Hu, Changwei
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- Steady-state kinetic analysis of human cholinesterases over wide concentration ranges of competing substrates
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Substrate competition for human acetylcholinesterase (AChE) and human butyrylcholinesterase (BChE) was studies under steady-state conditions using wide range of substrate concentrations. Competing couples of substates were acetyl-(thio)esters. Phenyl acetate (PhA) was the reporter substrate and competitor were either acetylcholine (ACh) or acetylthiocholine (ATC). The common point between investigated substrates is that the acyl moiety is acetate, i.e. same deacylation rate constant for reporter and competitor substrate. Steady-state kinetics of cholinesterase-catalyzed hydrolysis of PhA in the presence of ACh or ATC revealed 3 phases of inhibition as concentration of competitor increased: a) competitive inhibition, b) partially mixed inhibition, c) partially uncompetitive inhibition for AChE and partially uncompetitive activation for BChE. This sequence reflects binding of competitor in the active centrer at low concentration and on the peripheral anionic site (PAS) at high concentration. In particular, it showed that binding of a competing ligand on PAS may affect the catalytic behavior of AChE and BChE in an opposite way, i.e. inhibition of AChE and activation of BChE, regardless the nature of the reporter substrate. For both enzymes, progress curves for hydrolysis of PhA at very low concentration (?Km) in the presence of increasing concentration of ATC showed that: a) the competing substrate and the reporter substrate are hydrolyzed at the same time, b) complete hydrolysis of PhA cannot be reached above 1 mM competing substrate. This likely results from accumulation of hydrolysis products (P) of competing substrate and/or accumulation of acetylated enzyme·P complex that inhibit hydrolysis of the reporter substrate.
- Mukhametgalieva, Aliya R.,Lushchekina, Sofya V.,Aglyamova, Aliya R.,Masson, Patrick
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- Aerobic C?C Bond Cleavage Catalyzed by Whole-Cell Cultures of the White-Rot Fungus Dichomitus albidofuscus
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Whole-cell cultures of the basidiomycetous white-rot fungus Dichomitus albidofuscus exhibit varying catalytic activity towards aromatic compounds depending on the growth stage. This study reveals the catalytic behavior of mature whole-cell cultures that effectively catalyze a C?C bond cleavage oxidizing toluene, benzaldehyde and acetophenone to phenol. The reaction products were analyzed by GC-MS and NMR techniques. To exclude the de novo formation of phenol by the fungus, its origin has been proven by bioconversion of benzaldehyde-d5. The key step involves an aerobic Baeyer-Villiger type rearrangement where the incorporation of oxygen into the product was confirmed based on isotope labelling experiments with 18O2. Intermediate esters were not found in reaction mixture presumably due to the detected esterase activity in the mycelium as well as in supernatant of the whole-cell cultures. As a result, the sequence of biocatalytic reactions catalyzed by D. albidofuscus for the degradation of toluene via C?C bond cleavage has been disclosed.
- Zhuk, Tatyana S.,Babkina, Valeriia V.,Zorn, Holger
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- A highly efficient transformation from cumene to cumyl hydroperoxide via catalytic aerobic oxidation at room temperature and investigations into solvent effects, reaction networks and mechanisms
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Cumyl hydroperoxide (CHP) is an important intermediate for the production of phenol/acetone, but suffers from severe reaction conditions and a low yield industrially. Here, an efficient transformation from cumene to CHP was developed. Different solvents were modulated for cumene oxidation catalyzed by NHPI/Co, and reaction network and mechanisms were investigated methodically. Hexafluoroisopropanol (HFIP) markedly promoted the transformation from cumene to CHP compared to other solvents at room temperature. A cumene conversion high up to 64.3% were observed with a selectivity to CHP of 71.7%. The solvent HFIP exhibited a significant promotion on cumene oxidation due to its contribution to the enhancement of the concentration of PINO radicals. Moreover, cumyl, cumyl oxyl and methyl radicals were captured by TEMPO and analyzed by HRMS, and the reaction paths and mechanisms from cumene to products were inferred. The preparation method discovered in this work may open an access to the production of CHP.
- Chen, Chong,Ji, Lijun,Lu, Qiuting,Shi, Guojun,Yuan, Enxian,Zhou, Hongyu
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- An alternative route for the preparation of phenol: Decomposition of cyclohexylbenzene-1-hydroperoxide
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In this work, a HPW/ZSM-5 catalyst was prepared by impregnating phosphotungstic acid (HPW) with carrier ZSM-5 zeolite and characterized by XRD, SEM, N2 adsorption/desorption isotherm, NH3-TPD, and FT-IR techniques. The catalytic performance of HPW/ZSM-5 was investigated by using the decomposition reaction of cyclohexylbenzene-1-hydroperoxide (CHBHP) to phenol and cyclohexanone. The conversion rate of CHBHP was up to 97.28%. In addition, the reusability test exhibited that the high durability HPW/ZSM-5 as the conversion rate of CHBHP only decreased by 3.11% after five runs. The kinetic study of the decomposition reaction indicated it was a primary reaction. The apparent activation energy of the decomposition reaction was 102.39?kJ·mol–1 in the temperature range of 45–60℃. All results indicate that the HPW/ZSM-5 catalyst has good performance and promising applications in acid catalyzed organic chemistry.
- Yang, Yufei,Zhang, Yadong
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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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- Coordination Polymers as a Functional Material for the Selective Molecular Recognition of Nitroaromatics and ipso-Hydroxylation of Arylboronic Acids
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We report the synthesis and structural characterization of two coordination polymers (CPs), namely; [{Zn(L)(DMF)4} ? 2BF4]α (1) and [{Cd(L)2(Cl)2} ? 2H2O]α (2) (where L=N2,N6-di(pyridin-4-yl)naphthalene-2,6-dicarboxamide). Crystal packing of 1 reveals the existence of channels running along the b- and c-axis filled by the ligated DMF and lattice anions, respectively. Whereas, crystal packing of 2 reveals that the metallacycles of each 1D chain are intercalating into the groove of adjacent metallacycles resulting in the stacking of 1D loop-chains to form a sheet-like architecture. In addition, both 1 and 2 were exploited as multifunctional materials for the detection of nitroaromatic compounds (NACs) as well as a catalyst in the ipso-hydroxylation of aryl/heteroarylboronic acids. Remarkably, 1 and 2 showed high fluorescence stability in an aqueous medium and displayed a maximum 88% and 97% quenching efficiency for 4-NPH, respectively among all the investigated NACs. The mechanistic investigation of NACs recognition suggested that the fluorescence quenching occurred via electron as well as energy transfer process. Furthermore, the ipso-hydroxylation of aryl/heteroarylboronic acids in presence of 1 and 2 gave up to 99% desired product yield within 15 min in our established protocol. In both cases, 1 and 2 are recyclable upto five cycles without any significant loss in their efficiency.
- Rani, Pooja,Husain, Ahmad,Bhasin,Kumar, Girijesh
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- Droplet Flow Assisted Electrocatalytic Oxidation of Selected Alcohols under Ambient Condition
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This study reports using a droplet flow assisted mechanism to enhance the electrocatalytic oxidation of benzyl alcohol, 2-phenoxyethanol, and hydroxymethylfurfural at room temperature. Cobalt phosphide (CoP) was employed as an active electrocatalyst to promote the oxidation of each of the individual substrates. Surface analysis of the CoP electrocatalyst using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), as well as electrochemical characterization, revealed that it had excellent catalytic activity for each of the substrates studied. The combined droplet flow with the continuous flow electrochemical oxidation approach significantly enhanced the conversion and selectivity of the transformation reactions. The results of this investigation show that at an electrolysis potential of 1.3 V and ambient conditions, both the selectivity and yield of aldehyde from substrate conversion can reach 97.0%.
- Al Aqad, Khaled M.,Basheer, Chanbasha,Suliman, Mohammed A.
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- One-Pot Transformation of Lignin and Lignin Model Compounds into Benzimidazoles
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It is a challenging task to simultaneously achieve selective depolymerization and valorization of lignin due to their complex structure and relatively stable bonds. We herein report an efficient depolymerization strategy that employs 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as oxidant/catalyst to selectively convert different oxidized lignin models to a wide variety of 2-phenylbenzimidazole-based compounds in up to 94 % yields, by reacting with o-phenylenediamines with varied substituents. This method could take full advantage of both Cβ and/or Cγ atom in lignin structure to furnish the desirable products instead of forming byproducts, thus exhibiting high atom economy. Furthermore, this strategy can effectively transform both the oxidized hardwood (birch) and softwood (pine) lignin into the corresponding degradation products in up to 45 wt% and 30 wt%, respectively. Through a “one-pot” process, we have successfully realized the oxidation/depolymerization/valorization of natural birch lignin at the same time and produced the benzimidazole derivatives in up to 67 wt% total yields.
- Guo, Tao,He, Jianghua,Liu, Tianwei,Zhang, Yuetao
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supporting information
(2022/02/07)
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- Photocatalytic removal of benzene over Ti3C2T: XMXene and TiO2-MXene composite materials under solar and NIR irradiation
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MXenes, a family of two-dimensional (2D) transition metal carbides, nitrides and carbonitrides based on earth-abundant constituents, are prospective candidates for energy conversion applications, including photocatalysis. While the activity of individual MXenes towards various photocatalytic processes is still debatable, these materials were proved to be excellent co-catalysts, accelerating the charge separation and suppressing the exciton recombination. Titanium-containing MXenes are well compatible with the classical TiO2 photocatalyst. The TiO2 component can be directly grown on MXene sheets by in situ oxidation, representing a mainstream processing approach for such composites. In this study, an essentially different approach has been implemented: a series of TiO2-MXene composite materials with controlled composition and both reference end members were prepared, involving two different strategies for mixing sol-gel-derived TiO2 nanopowder with the Ti3C2Tx component, which was obtained by HF etching of self-propagating high-temperature synthesis products containing modified MAX phase Ti3C2Alz (z > 1) with nominal aluminium excess. The prospects of such composites for the degradation of organic pollutants under simulated solar light, using benzene as a model system, were demonstrated and analysed in combination with their structural, microstructural and optical properties. A notable photocatalytic activity of bare MXene under near infrared light was discovered, suggesting further prospects for light-to-energy harvesting spanning from UV-A to NIR and applications in biomedical imaging and sensors.
- Calvino, José J.,Constantinescu, Gabriel,Frade, Jorge R.,Kovalevsky, Andrei V.,Labrincha, Jo?o A.,Lajaunie, Luc,Lopes, Daniela V.,Sergiienko, Sergii A.,Shaula, Aliaksandr L.,Shcherban, Nataliya D.,Shkepu, Viacheslav I.,Tobaldi, David M.
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p. 626 - 639
(2022/01/22)
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- The influence of different carbonate ligands on the hydrolytic stability and reduction of platinum(
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Pt(iv) complexes bearing axial carbonate linkages have drawn much attention recently. A synthetic method behind this allows the hydroxyl group of bioactive ligands to be attached to the available hydroxyl group of Pt(iv) complexes, and the rapid release of free drugs is achieved after the reduction of carbonate-linked Pt(iv) complexes. Further understanding on the properties of Pt(iv) carbonates such as hydrolytic stability and reduction profiles, however, is hindered by limited research. Herein, six mono-carbonated Pt(iv) complexes in which the carbonate axial ligands possess various electron-withdrawing powers were synthesized, and the corresponding mono-carboxylated analogues were also prepared as references to highlight the different properties. The influence of the coordination environment towards the hydrolysis and reduction rate of Pt(iv) carbonates and carboxylates was explored. The mono-carbonated Pt(iv) complexes are both less stable and reduced faster than the corresponding mono-carboxylated ones. Moreover, the hydrolysis and reduction profiles are dependent not only on the electron-withdrawing ability of the carbonates but also on the nature of the opposite axial ligands. Besides, the exploration of the hydrolytic pathway for Pt(iv) carbonates suggests that the process proceeds by an attack of OH? on the carbonyl carbon, followed by elimination, which is different from that of Pt(iv) carboxylates. This study provides some information on the influence of axial carbonate ligands with different electron-withdrawing abilities on the properties of the Pt(iv) center, which may inspire new thoughts on the design of “multi-action” Pt(iv) prodrugs.
- Chen, Shu,Deng, Zhiqin,Ng, Ka-Yan,Tse, Man-Kit,Yao, Houzong,Zhou, Qiyuan,Zhu, Guangyu
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supporting information
p. 885 - 897
(2022/02/01)
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- Research on the decomposition kinetics and thermal hazards of aniline diazonium salt
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Diazotization reaction, strong exothermic characteristics and thermal instability of diazonium salts make the production process high risk. To research thermal hazards of aniline diazonium salt, dynamic experiments are carried out by the differential scanning calorimeter (DSC) to obtain thermodynamic parameters. Moreover, the kinetic parameters are analyzed by Advanced Kinetics and Technology Solutions (AKTS) software. Finally, the GC-MS and UV spectrum are used to further study the decomposition mechanism of the aniline diazonium salt. The results indicate that aniline diazonium salt is very easy to decompose. When the heating rate is 2 K/min, the onset decomposition temperature is only 27.21 ℃ (Tonset). The apparent activation energy of the decomposition process calculated by Friedman and Ozawa methods are respectively 98-85 kJ/mol and 110-100 kJ/mol. Under the ideal adiabatic conditions (φ = 1), the initial temperatures of TMRad for 24 h is only 6.2 ℃ (TD24), which is predicted by the AKTS software. The decomposition process of aniline diazonium salt is inconsistent with a single reaction mechanism.
- Du, Lei,Wang, Ben,Xie, Chuanxin,Yuan, Yucan
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- New Palladium – ZrO2 Nano-Architectures from Thermal Transformation of UiO-66-NH2 for Carbonylative Suzuki and Hydrogenation Reactions
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The new nanocomposites, Pd/C/ZrO2, PdO/ZrO2, and Pd/PdO/ZrO2, were prepared by thermal conversion of Pd@UiO-66-Zr?NH2 (MOF) in nitrogen or air atmosphere. The presence of Pd nanoparticles, uniformly distributed on the ZrO2 or C/ZrO2 matrix, was evidenced by transmission electron microscopy, scanning electron microscopy (SEM), Raman and X-ray Photoelectron Spectroscopy (XPS) methods. All pyrolysed composites retained the shape of the MOF template. They catalyze carbonylative Suzuki coupling under 1 atm CO with an efficiency significantly higher than the original Pd@UiO-66-Zr?NH2. The most active PdO/ZrO2 composite, formed benzophenone with TOF up to 1600 h?1, while by using Pd@UiO-66-Zr?NH2, much lower TOF values, 51–95 h?1, were achieved. After the reaction, PdO/ZrO2 was recovered with the same composition and catalytic activity. Very good results were also obtained in the transfer hydrogenation of benzophenones to alcohols with Pd/C/ZrO2 and PdO/ZrO2 catalysts under microwave irradiation.
- Alsalahi, Waleed,Augustyniak, Adam W.,Tylus, W?odzimierz,Trzeciak, Anna M.
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supporting information
(2021/12/22)
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- MOF-derived Ru@ZIF-8 catalyst with the extremely low metal Ru loading for selective hydrogenolysis of C–O bonds in lignin model compounds under mild conditions
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Lignin hydrogenolysis to produce chemicals and biofuels is a challenge due to the stable C–O ether bond structure. Metal–organic framework (MOF) materials with excellent structural and chemical versatility have received widespread attention. Herein, a highly dispersed Ru metal anchored in functionalised ZIF-8 was fabricated by a general host–guest and reduction strategy. The Ru@ZIF-8 catalyst with a high specific surface area could efficiently promote the C–O bond cleavage of a variety of lignin model compounds under mild conditions. Compared with previous studies, the extremely low metal Ru loading in the Ru@ZIF-8 catalyst achieved a relatively higher activity. The introduction of Ru metal not only improved the dispersion of Zn metal, but also enhanced the electron density on the Zn surface, suggesting a high catalytic performance. It was more conducive for the Ru@ZIF-8 catalyst to exhibit the C–O bond cleavage activity when in the presence of both H2 and isopropanol. An investigation of the mechanism revealed that the direct hydrogenolysis of benzyl phenyl ether was the main reaction pathway.
- Cao, Jing-Pei,Jiang, Wei,Xie, Jin-Xuan,Zhang, Chuang,Zhang, Jian-Li,Zhao, Liang,Zhao, Xiao-Yan,Zhao, Yun-Peng,Zhu, Chen
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p. 488 - 496
(2022/02/07)
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- Direct catalytic benzene hydroxylation under mild reaction conditions by using a monocationic μ-nitrido-bridged iron phthalocyanine dimer with 16 peripheral methyl groups
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Direct catalytic hydroxylation of benzene under mild reaction conditions proceeded efficiently in the presence of a monocationic μ-nitrido-bridged iron phthalocyanine dimer with 16 peripheral methyl groups in an acetonitrile solution with excess H2O2. Mechanistic studies suggested that the reaction was catalyzed by a high-valent iron-oxo species generated in situ. Moreover, the peripheral methyl groups of the catalyst were presumed to have enhanced the production rate of the iron-oxo species.
- Tanaka, Kentaro,Teoh, Chee-Ming,Toyoda, Yuka,Yamada, Yasuyuki
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supporting information
p. 955 - 958
(2022/02/07)
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- Synthesis of phenol from degraded lignin using synergistic effect of iron-oxide based catalysts: Oxidative cracking ability and acid-base properties
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The effects of ZrO2 and TiO2 incorporated into Fe2O3 matrix on oxidative cracking of degraded lignin and on the acid-base properties were investigated. After lignin degradation, cracking into lower-molecular-weight products was greatest using ZrO2-FeOX. Reactivity of the lattice oxygen was evaluated using H2-TPR, which revealed that the reactivity was improved. Thus, ZrO2-FeOX promoted oxidative decomposition of lignin to oligomers. In the cracking of 2-methoxyphenol, TiO2-FeOX and ZrO2-FeOX resulted in a 5- to 6-fold greater yield of phenol than the yield over Fe2O3. According to Mulliken population analysis, the charge density difference between Fe-O increased by ca. 12% in TiO2-FeOX and ZrO2-FeOX as compared with Fe2O3. This result suggests that addition of TiO2 and ZrO2 improved the acid-base properties of the catalyst, which promoted demethoxylation of 2-methoxyphenol. Thus, ZrO2-FeOX enhanced oxidative decomposition using its lattice oxygen that converted degraded lignin into lower molecule oligomers, followed by demethoxylation to produce phenol.
- Fumoto, Eri,Ishimaru, Hiroya,Masuda, Takao,Nakasaka, Yuta,Sato, Shinya,Yoshikawa, Takuya
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- 2-(4-Nitrophenyl)-1H-indolyl-3-methyl Chromophore: A Versatile Photocage that Responds to Visible-light One-photon and Near-infrared-light Two-photon Excitations
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Due to cell damage caused by UV light, photoremovable protecting groups (PPGs) that are removed using visible or near-infrared light are attracting attention. A 2-(4-nitrophenyl)- 1H-indolyl-3-methyl chromophore (NPIM) was synthesized as a novel PPG. Various compounds were caged using this PPG and uncaged using visible or near-infrared light. Low cytotoxicity of NPIM indicates that it may be applied in physiological studies.
- Abe, Manabu,Guo, Runzhao,Hamao, Kozue,Lin, Qianghua,Takagi, Ryukichi
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supporting information
p. 153 - 156
(2022/02/14)
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- Highly Selective Hydrodeoxygenation of Lignin to Naphthenes over Three-Dimensional Flower-like Ni2P Derived from Hydrotalcite
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A strategy for low-temperature synthesis of hydrotalcite-based nickel phosphide catalysts (Ni2P-Al2O3) with flower-like porous structures was proposed. The in situ reduction of red phosphorus at 500 °C enables Ni2P catalysts with small particle size and abundant active and acidic sites, which facilitate the activation of substrates and H2. In the hydrodeoxygenation of guaiacol, a 100% conversion and 94.5% yield of cyclohexane were obtained over the Ni2P-Al2O3 catalyst under 5 MPa H2 at 250 °C for 3 h. Other lignin-derived phenolic compounds could also afford the corresponding alkanes with yields higher than 85%. Moreover, Ni2P-Al2O3 exhibited high hydrodeoxygenation activity in the deconstruction of more complex wood structures, including lignin oil and real lignin. Among the two different types of Ni sites of Ni(1) and Ni(2) in Ni2P, density functional theory (DFT) calculations showed that the Ni(2) site, highly exposed on the Ni2P-Al2O3 surface, possesses a stronger ability to break C-OH bonds during the hydrodeoxygenation of guaiacol in comparison with the Ni(1) site.
- Chen, Guanyi,Diao, Xinyong,Ji, Na,Jia, Zhichao,Li, Changzhi,Li, Xinxin,Liu, Caixia,Liu, Qingling,Lu, Xuebin,Ma, Longlong,Song, Chunfeng,Wang, Shurong,Zhao, Yujun
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p. 1338 - 1356
(2022/02/07)
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- Impact of oxygen vacancies in Ni supported mixed oxide catalysts on anisole hydrodeoxygenation
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The hydrodeoxygenation (HDO) activity of anisole has been investigated over Ni catalysts on mixed metal oxide supports containing Nb–Zr and Ti–Zr in 1:1 and 1:4 ratios. XRD patterns indicate the incorporation of Ti (or Nb) into the ZrO2 framewo
- Ali, Hadi,Kansal, Sushil Kumar,Lauwaert, Jeroen,Saravanamurugan, Shunmugavel,Thybaut, Joris W.,Vandevyvere, Tom
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- A highly photosensitive covalent organic framework with pyrene skeleton as metal-free catalyst for arylboronic acid hydroxylation
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Covalent organic frameworks (COFs) have been widely utilized in metal-free photocatalytic synthesis base on their excellent properties such as super conjugation, porosity and stability. In this work, we synthesized a new COF material using 1,3,6,8-Tetrakis (p-formylphenyl)pyrene (TFPPy) and 2,2′-Dimethylbenzidine (DMBZ) as basic units through Schiff base condensation reaction. The new COF (TF-DM COF) was applied as metal-free catalyst for hydroxylation of arylboronic acids. The results indicated that the extended π conjugation of COFs enhanced the absorption of visible light, and the large porosity (BET surface area: 113.782 m2g?1) accelerated the reaction rate. Good recyclability enables it with multiple applications, which result in a great reducing of the cost. This study reports that TF-DM COF has a broad application prospect as a new generation of metal-free photocatalysts for organic conversions.
- Chen, Ying,Huo, Jianqiang,Zhang, Yubao
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- Pyridazine N-Oxides as Photoactivatable Surrogates for Reactive Oxygen Species
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A method for the photoinduced evolution of atomic oxygen from pyridazine N-oxides was developed. This underexplored oxygen allotrope mediates arene C-H oxidation within complex, polyfunctional molecules. A water-soluble pyridazine N-oxide was also developed and shown to promote photoinduced DNA cleavage in aqueous solution. Taken together, these studies highlight the utility of pyridazine N-oxides as photoactivatable O(3P) precursors for applications in organic synthesis and chemical biology.
- Basistyi, Vitalii S.,Frederich, James H.
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supporting information
p. 1907 - 1912
(2022/03/27)
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- Photocatalytic Degradation of 4,4′-Isopropylidenebis(2,6-dibromophenol) on Magnetite Catalysts vs. Ozonolysis Method: Process Efficiency and Toxicity Assessment of Disinfection By-Products
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Flame retardants have attracted growing environmental concern. Recently, an increasing number of studies have been conducted worldwide to investigate flame-retardant sources, environmental distribution, living organisms’ exposure, and toxicity. The presented studies include the degradation of 4,4′-isopropylidenebis(2,6-dibromophenol) (TBBPA) by ozonolysis and photocatalysis. In the photocatalytic process, nano-and micro-magnetite (n-Fe3 O4 and μ-Fe3 O4) are used as a catalyst. Monitoring of TBBPA decay in the photocatalysis and ozonolysis showed photocatalysis to be more effective. Significant removal of TBBPA was achieved within 10 min in photocatalysis (ca. 90%), while for ozonation, a comparable effect was observed within 70 min. To determine the best method of TBBPA degradation concentration on COD and TOC, the removals were examined. The highest oxidation state was obtained for photocatalysis on μ-Fe3 O4, whereas for n-Fe3 O4 and ozonolysis, the COD/TOC ratio was lower. Acute toxicity results show noticeable differences in the toxicity of TBBPA and its degradation products to Artemia franciscana and Thamnocephalus platyurus. The EC50 values indicate that TBBPA degradation products were toxic to harmful, whereas the TBPPA and post-reaction mixtures were toxic to the invertebrate species tested. The best efficiency in the removal and degradation of TBBPA was in the photocatalysis process on μ-Fe3 O4 (reaction system 1). The examined crustaceans can be used as a sensitive test for acute toxicity evaluation.
- Balawejder, Maciej,Barylyak, Adriana,Bobitski, Yaroslav,Kisa?a, Joanna,Tomaszewska, Anna
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- Photochemical transformations of 2, 6-dichlorophenol and 2-chlorophenol with superoxide ions in the atmospheric aqueous phase
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The possible photochemical transformation pathways of chlorophenols (2, 6-dichlorophenol and 2-chlorophenol) with superoxide anion radical (O2·?) were studied by steady-state irradiation and 355 nm laser flash photolysis technique. O
- Dong, Linchang,Hu, Shuheng,Lu, Jun,Peng, Shuchuan,Zhu, Chengzhu,Zhu, Mengyu
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- Diradicals Photogeneration from Chloroaryl-Substituted Carboxylic Acids
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With the aim of generating new, thermally inaccessible diradicals, potentially able to induce a double-strand DNA cleavage, the photochemistry of a set of chloroaryl-substituted carboxylic acids in polar media was investigated. The photoheterolytic cleavage of the Ar?Cl bond occurred in each case to form the corresponding triplet phenyl cations. Under basic conditions, the photorelease of the chloride anion was accompanied by an intramolecular electron-transfer from the carboxylate group to the aromatic radical cationic site to give a diradical species. This latter intermediate could then undergo CO2 loss in a structure-dependent fashion, according to the stability of the resulting diradical, or abstract a hydrogen atom from the medium. In aqueous environment at physiological pH (pH=7.3), both a phenyl cation and a diradical chemistry was observed. The mechanistic scenario and the role of the various intermediates (aryl cations and diradicals) involved in the process was supported by computational analysis.
- Di Terlizzi, Lorenzo,Protti, Stefano,Ravelli, Davide,Fagnoni, Maurizio
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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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- Ligand compound for copper catalyzed aryl halide coupling reaction, catalytic system and coupling reaction
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The invention provides a ligand compound capable of being used for copper catalyzed aryl halide coupling reaction, the ligand compound is a three-class compound containing a 2-(substituted or non-substituted) aminopyridine nitrogen-oxygen group, and the invention also provides a catalytic system for the aryl halide coupling reaction. Thecatalytic system comprises a copper catalyst, a compound containing a 2-(substituted or non-substituted) aminopyridine nitrogen-oxygen group adopted as a ligand, alkali and a solvent, and meanwhile, the invention also provides a system for the aryl halide coupling reaction adopting the catalyst system. The compound containing the 2-(substituted or non-substituted) aminopyridine nitrogen oxygen group can be used as the ligand for the copper catalyzed aryl chloride coupling reaction, and the ligand is stable under a strong alkaline condition and can well maintain catalytic activity when being used for the copper-catalyzed aryl chloride coupling reaction. In addition, the copper catalyst adopting the compound as the ligand can particularly effectively promote coupling of copper catalyzed aryl chloride and various nucleophilic reagents which are difficult to generate under conventional conditions, C-N, C-O and C-S bonds are generated, and numerous useful small molecule compounds are synthesized. Therefore, the aryl halide coupling reaction has a very good large-scale application prospect by adopting the copper catalysis system of the ligand.
- -
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Paragraph 0152-0158
(2021/05/29)
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- Photocatalytic synthesis of phenols mediated by visible light using KI as catalyst
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A transition-metal-free hydroxylation of iodoarenes to afford substituted phenols is described. The reaction is promoted by KI under white LED light irradiation and uses atmospheric oxygen as oxidant. By the use of triethylamine as base and solvent, the corresponding phenols are obtained in moderate to good yields. Mechanistic studies suggest that KI and catalysis synergistically promote the cleavage of C-I bond to form free aryl radicals.
- Huiqin, Wei,Wu, Mei
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supporting information
(2021/11/30)
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- 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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- Design and preparation of metal-based carbon nanosheets for C–O bond cleavage in the absence of external H2
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A facile yet sustainable approach for the production of Ni3S2-doped ultrathin carbon nanosheets in one-pot with very thin thickness of 30 nm was reported. Reaction of nickel nitrate hexahydrate, sodium lignosulfonate with boric acid could produce ultrathin carbon nanosheets. In comparison with the conventional method for the synthesis of Ni3S2-doped ultrathin carbon nanosheets, this reaction did not require second vulcanization step. Sodium lignosulfonate was used as carbon and sulfur source. Boric acid was used as 2D template and it could also be readily recycled for repeated use by simply evaporative crystallization. Ni3S2-doped ultrathin carbon nanosheets was expected to be an excellent catalyst for C–O bond cleavage under 260°C through catalytic transfer hydrogenation process. In addition, the optimal catalyst could also be recovered in the end.
- Chen, Changzhou,Zhou, Minghao,Jiang, Jianchun
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p. 1181 - 1185
(2021/06/23)
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- Environmentally-friendly and sustainable synthesis of bimetallic NiCo-based carbon nanosheets for catalytic cleavage of lignin dimers
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This paper reports on a study of 2D metal-based (Ni-, NiCo-) carbon nanosheet (CNs) material that were synthesized via a template method and the synthetic materials showed an ultra-thin lamellar structure. The structures were characterized using different analytical methods including XRD, SEM, EDX, TEM, XPS, NH3-TPD. The synthesized NiCo-based CNs are ultrathin sheet shape with good crystallinity and uniform particle distributions. In the synthetic route of NiCo-based CNs, sodium lignosulfonate was employed as carbon and sulfur source and boric acid was used as 2D template to form a perfect lamellar structure. It manifested an environmentally-friendly and sustainable concept for preparation of the 2D NiCo-CNs. Although simple CNs was a poor catalyst, after Ni and NiCo doping, it became highly active in cleavage of β-O-4 ether bond in lignin through a catalytic transfer hydrogenation process and led to very high product yields.
- Chen, Changzhou,Jiang, Jianchun,Liu, Peng,Ren, Jurong,Wu, Dichao,Xia, Haihong,Zhou, Minghao
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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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- Rational design of oligomeric MoO3 in SnO2 lattices for selective hydrodeoxygenation of lignin derivatives into monophenols
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Novel Mo-Sn bimetallic oxide catalysts with highly dispersed oligomeric MoO3 in SnO2 lattices, which were synthesized by the co-precipitation method and pretreated by anhydrous ethanol, were first employed in the hydrodeoxygenation of various lignin derivatives to produce monophenols with high activity and selectivity. In comparison with the pure α-MoO3 and the previous reported catalysts, the α-2Mo1Sn exhibited superior activity in the hydrodeoxygenation of guaiacol, with full conversion and 92.5% phenol yield at 300 °C under 4 MPa initial H2 pressure in n-hexane for 4 h. According to comprehensive characterizations and catalytic measurements, the excellent performance of α-2Mo1Sn was ascribed to the formation of abundant Sn-O-Mo-OV interfacial sites, which possessed strong Mo-Sn interaction with enhanced surface area, electron-donating group binding ability, Lewis acidity, and redox ability. It was demonstrated that over the present α-2Mo1Sn catalyst system, the Sn-O-Mo-OV interfacial sites could greatly facilitate the adsorption and activation of Caromatic-OCH3 and Caromatic-CH3 bonds, and thus significantly promote the demethoxylation and demethylation reaction to produce phenol. This work figures out the rational design of MoO3-based catalyst and displays a clear potential for the selective hydrodeoxygenation of lignin derivatives into monophenols.
- Diao, Xinyong,Ji, Na,Jia, Zhichao,Jiang, Sinan,Li, Tingting,Liu, Caixia,Liu, Qingling,Lu, Xuebin,Song, Chunfeng,Wang, Zhenjiao
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p. 234 - 251
(2021/08/19)
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- Ceria-promoted Co@NC catalyst for biofuel upgrade: synergy between ceria and cobalt species
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Ceria-promoted Co@NC (NC, N doped carbon) catalysts are prepared by pyrolysis of biomass materials. Characterization results indicate that ceria and Co species facilitate the distribution of each other due to the formation of a Ce-O-Co solid solution. The specific surface area of the catalyst increased from 378.77 to 537.7 m2g?1viathe introduction of ceria. The electron transfer from Co to Ce further enhanced their interaction, and Co species facilitate the formation of more defective oxygen vacancies on ceria, which are beneficial to the activities of catalytic hydrogenation and catalytic transfer hydrogenation (CTH), respectively. Thus, Co/Ce@NC (0.99% Co loading) pyrolyzed at 850 °C exhibits excellent performance in the hydrodeoxygenation (HDO) of vanillin with high metal utilization. Catalytic hydrogenation and CTH coexisted in the presence of H2and ethanol, and >99% yield of creosol can be obtained in each of them. The reaction processes are monitored. No intermediate is found in aqueous media, while ethoxymethyl-4-methoxy-2-phenol is detected in ethanol. Moreover, Co/Ce@NC presents outstanding stability and general applicability. This work provides new insights into the construction of M@NC (M, metal) catalysts and the HDO process of biofuel upgrade.
- Wang, Bowei,Gao, Ruixiao,Zhang, Dan,Zeng, Yuyao,Zhang, Fangying,Yan, Xilong,Li, Yang,Chen, Ligong
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supporting information
p. 8541 - 8553
(2021/04/12)
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- Exploiting a silver-bismuth hybrid material as heterogeneous noble metal catalyst for decarboxylations and decarboxylative deuterations of carboxylic acids under batch and continuous flow conditions
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Herein, we report novel catalytic methodologies for protodecarboxylations and decarboxylative deuterations of carboxylic acids utilizing a silver-containing hybrid material as a heterogeneous noble metal catalyst. After an initial batch method development, a chemically intensified continuous flow process was established in a simple packed-bed system which enabled gram-scale protodecarboxlyations without detectable structural degradation of the catalyst. The scope and applicability of the batch and flow processes were demonstrated through decarboxylations of a diverse set of aromatic carboxylic acids. Catalytic decarboxylative deuterations were achieved on the basis of the reaction conditions developed for the protodecarboxylations using D2O as a readily available deuterium source.
- ?tv?s, Sándor B.,Fül?p, Ferenc,Kónya, Zoltán,Kukovecz, ákos,Márton, András,Mészáros, Rebeka,Pálinkó, István,Szabados, Márton,Varga, Gábor
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p. 4685 - 4696
(2021/07/12)
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- Trans(Cl)-2,2′-bipyridinedicarbonyldichlororuthenium(II) complex catalyzed oxidation of olefins, aryl hydrocarbons and alcohols in homogeneous phase
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Catalytic oxidation of organic substrates has wide applications in chemical industries due to which huge extensive research work is continuously going on throughout the world. Present study reports efficacious use of Trans (Cl)-2,2′-bipyridinedicarbonyldichlororuthenium(II) complex catalyzed oxidation of internal and terminal olefins, aryl hydrocarbons and alcohols. CH2Cl2–C2H5OH (6:4) was suitable solvent system for these oxidation reactions. The normal pressure oxidation reaction has been carried out at 1 ?atm. Pressure of oxygen and at 300C. The high pressure oxidation reaction was done at 4.48 ?× ?103 KNm3 pressure of oxygen and at 600C. No diminished catalytic activity was observed while checking the recyclability of catalyst up to 6–8 catalytic runs. Catalytic activity was also investigated using tert-butyl hydroperoxide as oxidant inspite of di-oxygen. Effect of different parameters on the rate of oxidation was also studied i.e. extra ligand, temperature, solvents, acids and bases. Kinetic studies have been done and on the basis of kinetics, the mechanism is proposed.
- Sharma, Varsha,Pant, Bhawana,Prakash, Deep,Sagar, Priyanka
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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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- Method for promoting iron-catalyzed oxidation of aromatic compound carbon - hydrogen bond to synthesize phenol by ligand
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The method comprises the following steps: iron is used as - a catalyst metal; a sulfur-containing amino acid or cystine-derived dipeptide is a ligand; and under the common action of hydrogen peroxide as an oxidizing agent, an aromatic compound is synthesized to prepare a phenol. Under the action of an acid as an accelerant and hydrogen peroxide as an oxidizing agent, the aryl carbon - hydrogen bond is directly hydroxylated to form a phenolic compound, and the method for preparing the phenol by the catalytic oxidation reaction has a plurality of advantages. The reaction raw materials, the oxidant and the promoter are wide in source, low in price, environment-friendly and good in stability. The aromatic compound carbon - hydrogen bonds directly participate in the reaction to react in one step to form phenol. The reaction condition is mild, the functional group compatibility and the application range are wide. The reaction selectivity is good; under the optimized reaction conditions, the target product separation yield can reach 85%.
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-
Paragraph 0052-0053; 0126
(2021/09/21)
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- Electrophotocatalytic C?H Heterofunctionalization of Arenes
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The electrophotocatalytic heterofunctionalization of arenes is described. Using 2,3-dichloro-5,6-dicyanoquinone (DDQ) under a mild electrochemical potential with visible-light irradiation, arenes undergo oxidant-free hydroxylation, alkoxylation, and amination with high chemoselectivity. In addition to batch reactions, an electrophotocatalytic recirculating flow process is demonstrated, enabling the conversion of benzene to phenol on a gram scale.
- Huang, He,Lambert, Tristan H.
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supporting information
p. 11163 - 11167
(2021/04/19)
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- Light-Induced Efficient Hydroxylation of Benzene to Phenol by Quinolinium and Polyoxovanadate-Based Supramolecular Catalysts
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Direct Hydroxylation of benzene to phenol with high yield and selectivity has been the goal of phenol industrial production. Photocatalysis can serve as a competitive method to realize the hydroxylation of benzene to phenol owing to its cost-effective and environmental friendliness, however it is still a forbidding challenge to obtain good yield, high selectivity and high atom availability meanwhile. Here we show a series of supramolecular catalysts based on alkoxohexavanadate anions and quinolinium ions for the photocatalytic hydroxylation of benzene to phenol under UV irradiation. We demonstrate that polyoxoalkoxovanadates can serve as efficient catalysts which can not only stabilize quinolinium radicals but also reuse H2O2 produced by quinolinium ions under light irradiation to obtain excellent synergistic effect, including competitive good yield (50.1 %), high selectivity (>99 %) and high atom availability.
- Gu, Yaqi,Huang, Yichao,Li, Qi,Wei, Yongge,Yu, Han,Zang, Dejin
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p. 13310 - 13316
(2020/10/19)
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- Photocatalytic hydroxylation of benzene to phenol with dioxygen using sodium decatungstate
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A one-pot hydroxylation reaction, in which benzene is converted to phenol using oxygen under mild conditions has attracted attention as an environmentally benign alternative to the cumene method. Herein, we report on the photocatalytic hydroxylation of be
- Einaga, Hisahiro,Hojo, Hajime,Wang, Ziru
-
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- DIRECT HYDROXYLATION OF BENZENE TO PHENOL
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The invention provides a method for preparing phenols from aromatic compounds, particularly a method of preparing phenol by direct hydroxylation of benzene. The method comprises contacting benzene with nitrous oxide in the presence of a bimetallic zeolite
- -
-
Paragraph 0010; 0016-0024
(2021/01/25)
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- Photocatalytic hydroxylation of benzene to phenol over organosilane-functionalized FeVO4nanorods
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Photocatalytic benzene hydroxylation reaction using a clean oxidant such as H2O2 is a green synthetic approach for phenol synthesis. Here, our study shows that silylated iron vanadate (FeVO4) nanorods can function as promising photocatalysts to direct hyd
- Chen, Wenwen,Hou, Yidong,Huang, Lianqi,Liang, Hanying,Wei, Danlei,Yang, Can,Zhang, Jinshui,Zheng, Dandan,Zou, Junhua
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p. 5931 - 5937
(2021/09/10)
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- Rational Designed Polymer as a Metal-Free Catalyst for Hydroxylation of Benzene to Phenol with Dioxygen
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Abstract: Direct hydroxylation of benzene to phenol with dioxygen is a green route for synthesis of phenol. The higher bonding energies of C–H in benzene and O–O in dioxygen make metal-free catalysis a challenge. A novel metal-free catalyst of quinone-cyl
- Wang, Weitao,Wei, Yaoyao,Jiang, Xulu,He, Zhen-Hong,Zhang, Cunshe,Liu, Zhao-Tie
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p. 1330 - 1335
(2020/09/21)
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- Well-defined Cp*Co(III)-catalyzed Hydrogenation of Carbonates and Polycarbonates
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We herein report the catalytic hydrogenation of carbonates and polycarbonates into their corresponding diols/alcohols using well-defined, air-stable, high-valent cobalt complexes. Several novel Cp*Co(III) complexes bearing N,O-chelation were isolated for the first time and structurally characterized by various spectroscopic techniques including single crystal X-ray crystallography. These novel Co(III) complexes have shown excellent catalytic activity to produce value added diols/alcohols from carbonate and polycarbonates through hydrogenation using molecular hydrogen as sole reductant or iPrOH as transfer hydrogenation source. To demonstrate the developed methodology's practical applicability, we have recycled the bisphenol A monomer from compact disc (CD) through hydrogenation under the established reaction conditions using phosphine-free, earth-abundant, air- and moisture-stable high-valent cobalt catalysts.
- Dahiya, Pardeep,Gangwar, Manoj Kumar,Sundararaju, Basker
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p. 934 - 939
(2020/12/15)
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- Direct synthesis of a jet fuel range dicycloalkane by the aqueous phase hydrodeoxygenation of polycarbonate
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For the first time, propane-2,2-diyldicyclohexane, a jet fuel range C15dicycloalkane was directly produced by the aqueous phase hydrodeoxygenation (APHDO) of polycarbonate (PC). Among the investigated catalyst systems, the mixture of Rh/C and H-USY (denoted as Rh/C + H-USY) exhibited the best performance. Over it, a high yield of propane-2,2-diyldicyclohexane (94.9%) was achieved from the APHDO of pure PC pellets after a reaction was carried out at 473 K and 3.5 MPa H2for 12 h. The Rh/C + H-USY catalyst was stable under the investigated conditions. No evident deactivation was observed during three repeated cycles. When we used a chopped DVD disk (a representative of real PC wastes) as the substrate, a high yield (86.9%) of propane-2,2-diyldicyclohexane was obtained under the same reaction conditions. The propane-2,2-diyldicyclohexane as obtained had a high density (0.92 g mL?1) and a high volumetric net heat of combustion (39.6 MJ L?1). As a potential application, it can be blended into jet fuels to improve the range and payload of airplanes.
- Cong, Yu,Li, Guangyi,Li, Ning,Wang, Aiqin,Wang, Lulin,Wang, Xiaodong,Zhang, Tao
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p. 3693 - 3699
(2021/06/06)
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- Oxidative degradation of toxic organic pollutants by water soluble nonheme iron(iv)-oxo complexes of polydentate nitrogen donor ligands
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The ability of four mononuclear nonheme iron(iv)-oxo complexes supported by polydentate nitrogen donor ligands to degrade organic pollutants has been investigated. The water soluble iron(ii) complexes upon treatment with ceric ammonium nitrate (CAN) in aqueous solution are converted into the corresponding iron(iv)-oxo complexes. The hydrogen atom transfer (HAT) ability of iron(iv)-oxo species has been exploited for the oxidation of halogenated phenols and other toxic pollutants with weak X-H (X = C, O, S,etc.) bonds. The iron-oxo oxidants can oxidize chloro- and fluorophenols with moderate to high yields under stoichiometric as well as catalytic conditions. Furthermore, these oxidants perform selective oxidative degradation of several persistent organic pollutants (POPs) such as bisphenol A, nonylphenol, 2,4-D (2,4-dichlorophenoxyacetic acid) and gammaxene. This work demonstrates the utility of water soluble iron(iv)-oxo complexes as potential catalysts for the oxidative degradation of a wide range of toxic pollutants, and these oxidants could be considered as an alternative to conventional oxidation methods.
- Jana, Rahul Dev,Munshi, Sandip,Paine, Tapan Kanti
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p. 5590 - 5597
(2021/05/04)
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- Aryl phenol compound as well as synthesis method and application thereof
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The invention discloses a synthesis method of an aryl phenol compound shown as a formula (3). All systems are carried out in an air or nitrogen atmosphere, and visible light is utilized to excite a photosensitizer for catalyzation. In a reaction solvent, ArNR1R2 as shown in a formula (1) and water as shown in a formula (2) are used as reaction raw materials and react under the auxiliary action of acid to obtain the aryl phenol compound as shown in a formula (3). The ArNR1R2 in the formula (1) can be primary amine and tertiary amine, can also be steroid and amino acid derivatives, and can also be drugs or derivatives of propofol, paracetamol, ibuprofen, oxaprozin, indomethacin and the like. The synthesis method has the advantages of cheap and easily available raw materials, simple reaction operation, mild reaction conditions, high reaction yield and good compatibility of substrate functional groups. The fluid reaction not only can realize amplification of basic chemicals, but also can realize amplification of fine chemicals, such as synthesis of drugs propofol and paracetamol. The invention has wide application prospect and use value.
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-
Paragraph 0058-0062
(2021/05/12)
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- Substituent and Surfactant Effects on the Photochemical Reaction of Some Aryl Benzoates in Micellar Green Environment?
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In this study, we carried out preparative and mechanistic studies on the photochemical reaction of a series of p-substituted phenyl benzoates in confined and sustainable micellar environment. The aim of this work is mainly focused to show whether the nature of the surfactant (ionic or nonionic) leads to noticeable selectivity in the photoproduct formation and whether the electronic effects of the substituents affect the chemical yields and the rate of formation of the 5-substituted-2-hydroxybenzophenone derivatives. Application of the Hammett linear free energy relationship (LFER) on the rate of formation of benzophenone derivatives, on the lower energy band of the UV-visible absorption spectra of the aryl benzoates and 5-substituted-2-hydroxybenzophenone derivatives allows a satisfactory quantification of the substituent effects. Furthermore, UV-visible and 2D-NMR (NOESY) spectroscopies have been employed to measure the binding constant Kb and the location of the aryl benzoates within the hydrophobic core of the micelle. Finally, TD-DFT calculations have been carried out to estimate the energies of the absorption bands of p-substituted phenyl benzoates and 5-substituted-2-hydroxybenzophenone derivatives providing good linear correlation with those values measured experimentally.
- Siano, Gastón,Crespi, Stefano,Bonesi, Sergio M.
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p. 1298 - 1309
(2021/05/07)
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- Designing of Highly Active and Sustainable Encapsulated Stabilized Palladium Nanoclusters as well as Real Exploitation for Catalytic Hydrogenation in Water
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Abstract: Encapsulated nanoclusters based on palladium, 12-tunstophosphoric acid and silica was designed by simple wet impregnation methodology. The catalyst was found to be very efficient towards cyclohexene hydrogenation up to five catalytic runs with substrate/catalyst ratio of 4377/1 at 50?°C as well as for alkene, aldehyde, nitro and halogen compounds. Graphic Abstract: Silica encapsulated Pd nanoclusters stabilized by 12-tungstophosphoric acid is proved to be sustainable and excellent for water mediated hydrogenation reaction with very high catalyst to substrate ratio as well as TON.[Figure not available: see fulltext.]
- Patel, Anish,Patel, Anjali
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p. 803 - 820
(2020/08/12)
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- Palladium-catalyzed synthesis of 4-cyclohexylmorpholines from reductive coupling of aryl ethers and lignin model compounds with morpholines
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This work describes the highly efficient Pd-catalyzed direct coupling of aryl ethers (including the typical lignin model compounds) and morpholines to produce 4-cyclohexylmorpholines, a useful class of fine chemicals. Without employing any acidic additives, various 4-cyclohexylmorpholines could be synthesized with good yields from a variety of aryl ethers using H2 as a hydrogen resource. A mechanism study revealed that the desired product was formed via the cleavage of the C(Ar)-O bonds to generate the corresponding cyclohexanones and subsequent reductive amination. This journal is
- Zheng, Bingxiao,Song, Jinliang,Wu, Haihong,Han, Shitao,Zhai, Jianxin,Zhang, Kaili,Wu, Wei,Xu, Caiyun,He, Mingyuan,Han, Buxing
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p. 268 - 273
(2021/01/28)
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- Aluminum Metal-Organic Framework-Ligated Single-Site Nickel(II)-Hydride for Heterogeneous Chemoselective Catalysis
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The development of chemoselective and heterogeneous earth-abundant metal catalysts is essential for environmentally friendly chemical synthesis. We report a highly efficient, chemoselective, and reusable single-site nickel(II) hydride catalyst based on robust and porous aluminum metal-organic frameworks (MOFs) (DUT-5) for hydrogenation of nitro and nitrile compounds to the corresponding amines and hydrogenolysis of aryl ethers under mild conditions. The nickel-hydride catalyst was prepared by the metalation of aluminum hydroxide secondary building units (SBUs) of DUT-5 having the formula of Al(μ2-OH)(bpdc) (bpdc = 4,4′-biphenyldicarboxylate) with NiBr2 followed by a reaction with NaEt3BH. DUT-5-NiH has a broad substrate scope with excellent functional group tolerance in the hydrogenation of aromatic and aliphatic nitro and nitrile compounds under 1 bar H2 and could be recycled and reused at least 10 times. By changing the reaction conditions of the hydrogenation of nitriles, symmetric or unsymmetric secondary amines were also afforded selectively. The experimental and computational studies suggested reversible nitrile coordination to nickel followed by 1,2-insertion of coordinated nitrile into the nickel-hydride bond occurring in the turnover-limiting step. In addition, DUT-5-NiH is also an active catalyst for chemoselective hydrogenolysis of carbon-oxygen bonds in aryl ethers to afford hydrocarbons under atmospheric hydrogen in the absence of any base, which is important for the generation of fuels from biomass. This work highlights the potential of MOF-based single-site earth-abundant metal catalysts for practical and eco-friendly production of chemical feedstocks and biofuels.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Dwivedi, Ashutosh,Manna, Kuntal
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p. 3943 - 3957
(2021/04/12)
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