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We report the highly efficient and chemoselective oxidation of benzylic alcohols catalyzed by sodium copper chlorophyllin in water, producing corresponding arylcarbonyl compounds. Importantly, the catalytic system exhibits a wide substrate scope and high functional group tolerance. Moreover, secondary alcohols and even diarylmethanes were smoothly oxidized to the desired aryl ketones with excellent yields.

Ethyl 2-(N-arylcarbamoyl)-2-iminoacetates can be transformed into the corresponding quinoxalin-2-ones in high yield by using the oxidation system of tert-butyl hypochlorite, tetrabutylammonium iodide and tetrabutylammonium chloride. Oxygen exhibits a beneficial effect on the reaction. The reaction is proposed to follow an iminyl radical cyclization mechanism where azaspirocyclohexadienylperoxyl radical is formed as a key intermediate. The quinoxalin-2-one is derived from the azaspirocyclohexadienylperoxyl radical via concurrent oxygen extrusion and rearrangement. [ABSTRACT FROM AUTHOR]

Abstract  The oxidation behavior of pure Mg and Mg–Gd-Y-Zr alloy was studied in O2 at 300 °C with and without the presence of water vapor. The kinetics curves revealed improved oxidation resistance of Mg–Gd–Y–Zr alloy in O2, compared with pure Mg. However, when water vapor co-existed with oxygen, the oxidation rate of Mg–Gd–Y–Zr alloy was accelerated; whereas, the oxidation rate of pure Mg was restrained. Detailed XPS analysis of pure Mg oxidized with water vapor revealed that the reduced oxidation rate could be strongly linked with the outer Mg(OH)2 film. On the contrary, for Mg–Gd–Y–Zr alloy, an incomplete Mg(OH)2 film was present in the outer region of oxide layer, which can provide a ready pathway for water vapor transport to the inner part of the oxide film and which has little oxidation resistance to water vapor. [ABSTRACT FROM AUTHOR]

SiO2/V2O5/TiO2 catalysts were synthesized for removing elemental mercury (Hg0) from simulated coal-combustion flue gas. Experiments were carried out in fixed-bed reactors using both pellet and powder catalysts. In contrast to the SiO2—TiO2 composites developed in previous studies, the V2O5 based catalysts do not need ultraviolet light activation and have higher Hg0 oxidation efficiencies. For Hg0 removal by SiO2—V2O5 catalysts, the optimal V2O5 loading was found between 5 and 8%, which may correspond to a maximum coverage of polymeric vanadates on the catalyst surface. Hg0 oxidation follows an Eley—Rideal mechanism where HCI, NO, and NO2 are first adsorbed on the V2O5 active sites and then react with gas-phase Hg0. HCI, NO, and NO2 promote Hg oxidation, while SO2 has an insignificant effect and water vapor inhibits Hg0 oxidation. The SiO2—TiO2—V2O5 catalysts exhibit greater Hg0 oxidation efficiencies than SiO2—V2O5, may be because the V—O—Ti bonds are more active than the V—O—Si bonds. This superior oxidation capability is advantageous to power plants equipped with wet-scrubbers where oxidized Hg can be easily captured. The findings in this work revealed the importance of optimizing the composition and microstructures of SCR (selective catalytic reduction) catalysts for Hg0 oxidation in coal-combustion flue gas. [ABSTRACT FROM AUTHOR]

A highly efficient oxidation of cyclohexane to cyclohexanone is accomplished over phenanthroline–CuCl2 catalyst in relatively mild conditions. This study realized nearly 100% selectivity for cyclohexanone at 24.4% conversion of cyclohexane. The reaction has been studied by various parameters like performance of copper(II) salts, effect of solvents, influence of bases, the ratio of o-phenanthroline: CuCl2, and reaction time. In order to further study this reaction system, the possible mechanism was proposed. [ABSTRACT FROM AUTHOR]

A novel silica-titania (SiO2-TiO2) nanocomposite has been developed to effectively capture elemental mercury (Hg0) under UV irradiation. Moisture has been reported to have an important impact on this nanocomposite's performance. In this work, the role of moisture on Hg0 removal and reemission as well as the corresponding mechanisms was investigated. Hg0 removal experiments were carried out in a fixed-bed reactor at 65 °C using air as the carrier gas. Without UV irradiation, Hg0 adsorption was found to be insignificant, but it could be enhanced by the photocatalytic oxidation product, mercuric oxide (HgO), possibly due to the high affinity between HgO and Hg0. Under dry conditions 95% of Hg0 can be removed; however, increased humidity levels remarkably suppress both Hg0 adsorption and photocatalytic oxidation. Introducing water vapor can also result in significant reemission of captured Hg0from the nanocomposite, which may be ascribed to the repellant effect of water vapor adsorbed on the superhydrophilic TiO2 surface. Exposure to UV light was found either to prohibit Hg0 reemission when photocatalytic oxidation of reemitted Hg0 prevailed or to promote Hg0 reemission when photocatalytic reduction of HgO to Hg0 dominated later on. The results indicate that minimization of Hg0 reemission can be achieved by appropriate application of UV irradiation. [ABSTRACT FROM AUTHOR]

Phenolic-based fabrics are used as base materials for preparing carbon fiber absorbents by means of oxidation, carbonization, and activation in a continuous semi-open high- temperature furnace. The effect of activation conditions on the pore characteristics and absorption capabilities is studied. The results show that the pore diameter of specimens is within 100 Å, indicating micropore and mesopore structures. In addition, phenolic- based carbon fiber absorbents show over 50% absorption for four volatile organic compounds, and their regeneration capabilities can reach 100%. [ABSTRACT FROM AUTHOR]

A chemoselective synthesis of butenolides was found based on TBAF-mediated deprotection, cyclization, dehydration, and oxidation of 3-hydroxy-4-(tert-butyldimethylsilyloxy)- pentanoates, which yielded either 4-methylbutenolides or 4-hydroxy- 4-methylbutenolides in moderate to good yields. The selectivity depends on the quantity of TBAF. This method was applied to the synthesis of several 4-butenolide compounds. [ABSTRACT FROM AUTHOR]

Nitrogen (N2) gas in the atmosphere is partially replenished by microbial denitrification of ammonia. Recent study has shown that Alcaligenes ammonioxydans oxidizes ammonia to dinitrogen via a process featuring the intermediate hydroxylamine, termed "Dirammox" (direct ammonia oxidation). However, the unique biochemistry of this process remains unknown. Here, we report an enzyme involved in Dirammox that catalyzes the conversion of hydroxylamine to N2. We tested previously annotated proteins involved in redox reactions, DnfA, DnfB, and DnfC, to determine their ability to catalyze the oxidation of ammonia or hydroxylamine. Our results showed that none of these proteins bound to ammonia or catalyzed its oxidation; however, we did find DnfA bound to hydroxylamine. Further experiments demonstrated that, in the presence of NADH and FAD, DnfA catalyzed the conversion of 15N-labeled hydroxylamine to 15N2. This conversion did not happen under oxygen (O2)-free conditions. Thus, we concluded that DnfA encodes a hydroxylamine oxidase. We demonstrate that DnfA is not homologous to any known hydroxylamine oxidoreductases and contains a diiron center, which was shown to be involved in catalysis via electron paramagnetic resonance experiments. Furthermore, enzyme kinetics of DnfA were assayed, revealing a Km of 92.9 ± 3.0 μM for hydroxylamine and a kcat of 0.028 ± 0.001 s-1. Finally, we show that DnfA was localized in the cytoplasm and periplasm as well as in tubular membrane invaginations in HO-1 cells. To the best of our knowledge, we conclude that DnfA is the first enzyme discovered that catalyzes oxidation of hydroxylamine to N2. [ABSTRACT FROM AUTHOR]

CeO2-TiO2 (CeTi) catalysts synthesized by an ultrasound-assisted impregnation method were employed to oxidize elemental mercury (Hg0) in simulated low-rank (sub-bituminous and lignite) coal combustion flue gas. The CeTi catalysts with a CeO2/TiO2 weight ratio of 1-2 exhibited high Hg0 oxidation activity from 150 to 250 °C. The high concentrations of surface cerium and oxygen were responsible for their superior performance. Hg0 oxidation over CeTi catalysts was proposed to follow the Langmuir-Hinshelwood mechanism whereby reactive species from adsorbed flue gas components react with adjacently adsorbed Hg0. In the presence of O2, a promotional effect of HCl, NO, and SO2 on Hg0 oxidation was observed. Without O2, HCl and NO still promoted Hg0 oxidation due to the surface oxygen, while SO2 inhibited Hg0 adsorption and subsequent oxidation. Water vapor also inhibited Hg0 oxidation. HCl was the most effective flue gas component responsible for Hg0 oxidation. However, the combination of SO2 and NO without HCl also resulted in high Hg0 oxidation efficiency. This superior oxidation capability is advantageous to Hg0 oxidation in low-rank coal combustion flue gas with low HCl concentration. [ABSTRACT FROM AUTHOR]

Studies suggest the potential role of a sarcoplasmic reticulum (SR) Ca2+ leak in cardiac contractile dysfunction in sepsis. However, direct supporting evidence is lacking, and the mechanisms underlying this SR leak are poorly understood. Here, we investigated the changes in cardiac Ca2+ handling and contraction in LPS-treated rat cardiomyocytes and a mouse model of polymicrobial sepsis produced by cecal ligation and puncture (CLP). LPS decreased the systolic Ca2+ transient and myocyte contraction as well as SR Ca2+ content. Meanwhile, LPS increased Ca2+ spark-mediated SR Ca2+leak. Preventing the SR leak with ryanodine receptor (RyR) blocker tetracaine restored SR load and increased myocyte contraction. Similar alterations in Ca2+ handling were observed in cardiomyocytes from CLP mice. Treatment with JTV-519, an anti-SR leak drug, restored Ca2+ handling and improved cardiac function. In the LPS-treated cardiomyocytes, mitochondrial reactive oxygen species and oxidative stress in RyR2 were increased, whereas the levels of the RyR2-associated FK506-binding protein 1B (FKBP12.6) were decreased. The Toll-like receptor 4 (TLR4)-specific inhibitor TAK-242 reduced the oxidative stress in LPS-treated cells, decreased the SR leak, and normalized Ca2+ handling and myocyte contraction. Consistently, TLR4 deletion significantly improved cardiac function and corrected abnormal Ca2+ handling in the CLP mice. This study provides evidence for the critical role of the SR Ca2+ leak in the development of septic cardiomyopathy and highlights the therapeutic potential of JTV-519 by preventing SR leak. Furthermore, it reveals that TLR4 activation-induced mitochondrial reactive oxygen species production and the resulting oxidative stress in RyR2 contribute to the SR Ca2+ leak. [ABSTRACT FROM AUTHOR]

Ferrate(VI) (Fe VI O 4 2− , Fe(VI)) is a greener oxidant in the treatment of drinking water and wastewater. The electrochemical synthesis of Fe(VI) may be considered environmentally friendly because it involves one-step process to convert Fe(0) to Fe(VI) without using harmful chemicals. Electrolysis was performed by using a sponge iron as an anode in NaOH solution at different ionic strengths. The cyclic voltammetric (CV) curves showed that the sponge iron had higher electrical activity than the grey cast iron. The optimum current density was 0.054 mA cm −2 in 10 M NaOH solution, which is much lower than the electrolyte concentrations used in other electrode materials. A comparison of current efficiency and energy consumption was conducted and is briefly discussed. The generated ferrate solution was applied to degrade phenol in water at two levels (2 mg L −1 and 5 mg L −1 ). The maximum removal efficiency was ∼70% and the optimum pH for phenol treatment was 9.0. Experiments on phenol removal using conventional coagulants (ferric chloride (FeCl 3 ) and polyaluminium chloride (PAC)) were performed independently to demonstrate that removal of phenol by Fe(VI) occurred mainly by oxidative transformation. A combination of Fe(VI) and coagulant may be advantageous in enhancing removal efficiency, adjusting pH, and facilitating flocculation. [ABSTRACT FROM AUTHOR]

Through a biomimetic pathway, hyperolactone D, 4-hydroxyhyperolactone D, and hyperolactone C were synthesized from methyl acetoacetate via Weiler's dianion method, asymmetric allylic alkylation, biomimetic lactonization, oxidation, and cyclization. The stereochemistry of the quaternary carbon was controlled efficiently by Palladium-catalyzed asymmetric allylic alkylation. This strategy was also used for the synthesis of hyperolactone B. [ABSTRACT FROM AUTHOR]

The article discusses a study which develops a tandem Michael addition/ylide epoxidation for the rapid creation of highly functionalized cyclohexadiene epoxide skeletons with three sterocenters. The study investigated the intramolecular version of the tandem reaction. It is showed that the tandem reaction could access to highly functionalized cyclohexadiene epoxide derivatives with excellent diastereoselectivity and chemoselectivity.