Copper-catalyzed C-alkylation of secondary alcohols and methyl ketones with alcohols employing the aerobic relay race methodology

By employing aerobic oxidation to aldehydes as a more effective alcohol activation strategy, ligand-free copper catalysts were found to be superior catalysts than other metals in aerobic dehydrative β-alkylation of secondary alcohols and α-alkylation of methyl ketones using alcohols as the green alkylating reagents. Based on our mechanistic studies and also supported by the literature, we deduce that the newly-proposed relay race process rather than the conventional borrowing hydrogen-type mechanisms should be the most possible and a more rational mechanism for the aerobic C-alkylation reactions.     

PHOTOSENSITIZATION BY 2-CHLORO-3, 11-TRIDECADIENE-5, 7, 9-TRIYN-1-OL: DAMAGE TO ERYTHROCYTE MEMBRANES, Escherichia coli, AND DNA

The natural product 2-chloro-3,11-tridecadiene-5,7,9-triyn-1-ol (1) photosensitized the inactivation of Escherichia coli in the presence of near-ultraviolet light (320-400 nm; NUV) under both aerobic and anaerobic conditions. A series of E. coli strains differing in DNA repair capabilities and catalase proficiency exhibited indistinguishable inactivation kinetics following treatment with the chemical plus NUV. The presence of carotenoids did afford some protection to E. coli against inactivation under aerobic conditions, consistent with the involvement of singlet oxygen. The photosensitized hemolysis of human erythrocytes occurred more rapidly in the absence than in the presence of oxygen. Aerobically, the onset of hemolysis was partially inhibited by NaN3 and by 2,6-di-t-butyl-4-methylphenol (BHT) but not by superoxide dismutase (SOD). The aerobic lipid peroxidation observed in the membranes of erythrocyte ghosts was completely inhibited by BHT, and partially by NaN3, but not by SOD. These results suggest that either lipid peroxidation of the membrane is not the main cause of photohemolysis or that BHT has insufficient access to intact erythrocyte lipids to protect them. Aerobically, crosslinking of membrane proteins was also observed; it was not affected by SOD, but was partially inhibited by BHT and NaN3. The anaerobic photosensitized hemolysis of erythrocytes was more rapid; a radical mechanism was suggested since BHT inhibited the hemolysis to a greater extent than under aerobic conditions. Neither lipid peroxidation nor protein crosslinking was observed under conditions believed to be anaerobic. A light-dependent electron transfer to cytochrome c was obtained under argon but not under oxygen. Although induced mutations were not observed in the experiments with E. coli, 1 was capable of damaging both supercoiled pBR322 and Haemophilus influenzae transforming DNA in a manner that seemed to be equivalent under aerobic and anaerobic conditions. In conclusion, 1 can behave as typical photodynamic molecule under aerobic conditions but, in contrast to most photodynamic molecules, it is also phototoxic under anaerobic conditions. The extent to which the radical reactions detected under anaerobic reactions compete with the photodynamic processes when oxygen is present is not known.     

复合仿生催化体系的构建与高效有氧氧化芳基烷烃

直接活化氧气氧化碳氢化合物是件挑战性的研究工作。根据生物酶很容易在温和条件下实现上述反应,以Keggin-型杂多酸[CuPW_(11)O_(39)]5-(简写为CuPW_(11))与金属-有机框架材料HKUST-1形成的复合材料Cu PW_(11)@HKUST-1为催化剂,以N-羟基邻苯二甲酰亚胺为助催化剂,构建模拟酶催化氧化反应体系。其中,CuPW_(11)@HKUST-1中的杂多酸作为氧化还原中心,N-羟基邻苯二甲酰亚胺作为电子供体。该复合模拟酶催化体系在催化活化氧气氧化芳基烷烃的反应中表现出了类似生物酶催化的性质,具有反应条件温和、转化率高、转化数高和选择性高等特点,其中产物产率与转化数分别高达99%和17700,为实现在温和条件下高效活化氧气氧化惰性有机物分子提供了一条切实可行的路线。     

Sorption of radioactive technetium on pyrrhotine

The sorption behavior of technetium on pyrrhotine was studied with batch experiments and diluted sulfuric acid (less than 2.88 mol/l) was used to dissolve the technetium adsorbed on pyrrhotine. A significant sorption of technetium on pyrrhotine was observed under aerobic and anaerobic conditions, and the sorption on the mineral was supposed to be due to the reduction of TcO₄ ^- to insoluble TcO₂ ^.nH₂O. Sorbed technetium on the mineral could be desorbed by diluted sulfuric acid. The maximum desorption ratio under aerobic conditions was much higher than that of under anaerobic conditions, meanwhile, the desorption rates under anaerobic conditions were higher than that of under aerobic conditions in the initial stage of the experiments.     

Environmental influences on diethyl phthalate biodegradation kinetics

The effects of temperature, dissolved oxygen level, and diethyl phthalate (DEP) concentration on the rates of DEP biodegradation have been investigated in shake flask and fermenter experiments, using aerobic and facultatively aerobic microorganisms. The aerobic strain followed Monod growth kinetics, and was negatively affected by temperatures lower than 25 °C and dissolved oxygen levels lower than 0.8 mg/L, whereas the specific DEP-degrading activity of the facultative strain was substrate inhibited under anaerobic conditions, higher at 15°C than 25°C under aerobic conditions, and unaffected by the dissolved oxygen level. Studies were also carried out in soil columns to identify additional factors that might be important for modeling DEP biodegradation.     

Chemoselective Oxidation of Benzyl,Amino, and Propargyl Alcohols to Aldehydes and Ketones under Mild Reaction Conditions

Catalytic oxidation reactions often suffer from drawbacks such as low yields and poor selectivity. Particularly, selective oxidation of alcohols becomes more difficult when a compound contains more than one oxidizable functional group. In order to deliver a methodology that addresses these issues, herein we report an efficient, aerobic, chemoselective and simplified approach to oxidize a broad range of benzyl and propargyl alcohols containing diverse functional groups to their corresponding aldehydes and ketones in excellent yields under mild reaction conditions. Optimal yields were obtained at room temperature using 1 mmol substrate, 10 mol % copper(I) iodide, 10 mol % 4-dimethylaminopyridine (DMAP), and 1 mol % 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) in acetonitrile, under an oxygen balloon. The catalytic system can be applied even when sensitive and oxidizable groups such as alkynes, amines, and phenols are present; starting materials and products containing such groups were found to be stable under the developed conditions.     

Effect of polyethylenimine, a cell permeabilizer, on the photosensitized destruction of algae by methylene blue and nuclear fast red

The present study reports the effect a cell permeabilizer, polyethylenimine (PEI) has on the photodynamic effect of methylene blue (MB) and nuclear fast red (NFR) in the presence of hydrogen peroxide (H2O2). The photosensitized destruction of the algae Chlorella vulgaris under irradiation with visible light is examined. The photodynamic effect was investigated under aerobic and anaerobic conditions. The presence of a permeabilizer during the photosensitized destruction of C. vulgaris does not enhance the activity of the MB, MB/H2O2 system or the NFR, NFR/H2O2 system under aerobic conditions. However under anaerobic conditions we have determined that when a cell permeabilizer was added to the MB/H202 system, the photosensitized destruction of C. vulgaris proceeded via a combination of Type I and Type II mechanisms. The presence of PEI enforces MB/H2O2 to be active toward the destruction of C. vulgaris whether oxygen is present or absent. Under aerobic and anaerobic conditions the activity of NFR was suppressed in the presence of PEI as a result of electrostatic interactions between the photosensitizer and the cell permeabilizer. The decrease in fluorescence recorded is indicative of destruction of the chlorophyll a pigment.     

NEAR-UV INDUCTION OF SISTER CHROMATID EXCHANGES UNDER AEROBIC AND ANAEROBIC CONDITIONS

Abstract— The induction of sister chromatid exchanges (SCE) and cell sensitivity in mouse myeloma cells (66.2 subclone of MPC11) by irradiation with monochromatic near-UV (365 nm) light were studied under aerobic and anaerobic conditions. Sister chromatid exchanges were studied using the fluorescence-plus-Giemsa technique, and sensitivity was determined by the ability of irradiated and nonirradiated control cells to form colonies in soft agar. Cells were found to be 16 times more sensitive to near-UV light under aerobic exposure, producing an F₃₇ value of 7 × 10⁴ J/m² compared to the F₃₇ value of 11.5 × 10⁵ J/m² under anaerobic conditions. The induction of SCE was also 12 times more efficient for aerobic irradiation than for anaerobic irradiation. The data suggest that the SCE-inducing potential of DNA lesions differs when near-UV irradiation is performed in the presence or absence of air. In addition, the DNA lesions responsible for lethality and also those lesions leading to SCE induction may differ under the two irradiation conditions.     

Transformation experiments with two chiral endosulfan metabolites by soil microorganisms — CHIRAL HRGC on lipophilic cyclodextrin derivatives

Two chiral metabolites of the hexachlorinated cyclodien insecticide endosulfan, C₉H₆Cl₆O₃S, the endosulfan hydroxyether and the endosulfan lactone, were separated into their enantiomers using lipophilic β-cyclodextrin derivatives in chiral high-resolution gas chromatography (CHRGC). We separated the hydroxyether on heptakis-(2,3,6-tri-O-pentyl)-β-cyclodextrin (LIPODEX-C) and the endosulfan lactone on heptakis-(3-O-acetyl-2,6-di-O-pentyl)-β-cyclodextrin (LIPODEX-D). We also investigated the enantioselective formation and transformation of these two metabolites by soil organisms. To approximate real world conditions of microbiological transformation, incubation experiments with mixed cultures of soil microorganisms were carried out. Significant differences were observed in the transformation experiments under aerobic and anaerobic conditions. The endosulfan hydroxyether (ESH) is not formed enantioselectively from prochiral endosulfan diol (ESD) in the aerobic transformation pathway. The hydroxyether itself is enantioselectively converted to the endosulfan lactone (ESL) as a major pathway only under aerobic conditions. Corresponding enantiomers of endosulfan hydroxyether and endosulfan lactone with the same absolute configuration could be assigned. The lactone enantiomers are stereoselectively formed via the hydroxyether as a minor pathway under anaerobic conditions. While the first eluting lactone enantiomer was more abundant in the aerobic experiment, it was the second eluting under anaerobic conditions. Four major so far unidentified metabolites were detected in the anaerobic incubations of both the endosulfan hydroxyether and the endosulfan diol.     

Biodegradation of Pyridine and Pyridine Derivatives by Soil and Subsurface Microorganisms

Abstract

Large amounts of aromatic compounds are produced by various industries and two thirds of these are heterocyclic chemicals. Compared with the extensive information available on microbial degradation of homocyclic aromatic compounds, relatively little is known on the transformation and biodegradation of heterocyclic chemicals in soil. Recent concerns about the persistence of hazardous pollutants have led to a renewed interest in the biodegradation of heterocyclic compounds. Hence, we investigated the microbial degradation of pyridine and some of its alkylated derivatives under aerobic and anaerobic conditions in groundwater, subsurface sediment, and soil. Results of the investigation revealed that these compounds were degraded predominantly under aerobic conditions and, to a lesser extent, under anaerobic conditions, with nitrate or sulfate serving as electron acceptors. In groundwater polluted with various pyridine derivatives, biodegradation was limited by the absence of oxygen. Therefore, we conclude that, under appropriate conditions, bioremediation is a potentially feasible method for the clean-up of environments contaminated with heterocyclic chemicals and, in particular, pyridine derivatives.     

An Iron-Catalyzed Protein Desulfurization Method Reminiscent of Aquatic Chemistry

One pillar of protein chemical synthesis based on the application of ligation chemistries to cysteine is the group of reactions enabling the selective desulfurization of cysteine residues into alanines. Modern desulfurization reactions use a phosphine as a sink for sulfur under activation conditions involving the generation of sulfur-centered radicals. Here we show that cysteine desulfurization by a phosphine can be effected efficiently by micromolar concentrations of iron under aerobic conditions in hydrogen carbonate buffer, that is using conditions that are reminiscent of iron-catalyzed oxidation phenomena occurring in natural waters. Therefore, our work shows that chemical processes taking place in aquatic systems can be adapted to a chemical reactor for triggering a complex chemoselective transformation at the protein level, while minimizing the resort to harmful chemicals.     

Influence of Different Redox Conditions on the Biodegradation of the Pesticide Metabolites Phenol and Chlorophenols

Abstract

The fate and behaviour of phenol and monochlorophenols during bankfiltration and underground passage with variable redox conditions were investigated. A model ecosystem was used consisting in laboratory filter columns filled with natural underground material and operated with natural aerobic and anaerobic groundwater to create different redox situations.

The test substances (phenol, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol) were added continuously to the infiltrating water and their concentration in the filter effluents determined. Beside the redox conditions other factors known to affect microbial degradation processes like the substrate concentration and the underground material were varied stepwise.

Phenol was degraded under both, aerobic and anaerobic conditions. The presence of oxygen is more favourable to degradation; no lag phase was observed under aerobic conditions. In a sulfate reducing environment, phenol could only be degraded after microbial adaptation. The length of the lag phase was strongly influenced by the substrate concentration and the undergroundmaterial. Prior contact with phenol resulted in a shorter lag phase.

Monochlorophenols behaved almost persistent in the model system. Degradation could only be observed in a test filter that provided a more active microbial population due to prior adaptation to phenol and a more favourable underground material.     

Degradation and metabolism of imazapyr in soils under aerobic and anaerobic conditions

The degradation of imazapyr in four soils was investigated under laboratory aerobic and anaerobic conditions. Under aerobic conditions, imazapyr degraded faster in yellow–red soil than in other soils, and its persistence decreased depending on soil pH in the order coastal soil (pH 8.8)?>?silt-loamy paddy soil (pH 7.9)?>?fluvio-marine yellow loamy soil (pH 7.1)?>?Yellow–red soil (pH 5.3). However, soil pH did not affect imazapyr degradation under anaerobic conditions. The half-lives of imazapyr in soils under aerobic conditions were in the range of 26–44 days estimated by the first-order kinetics model, while 3–10 days calculated by two-stage model under anaerobic conditions. The preceding results demonstrated that anaerobic conditions contributed to imazapyr disappearance in soils. Based on the spectral data of APCI-MS, ¹H NMR and IR, structures of the following metabolites: 2,3-pyridinedicarboxamide, 2,3-pyridinedicarboxylic anhydride and 2,3-pyridinedicarboximide for aerobic treatments; 2,3-pyridinedicarboxylic anhydride and 2-(4-hydroxy-5-oxo-2-imdazolin-2-yl) nicotinic acid for anaerobic treatments, were identified. Degradation mechanism under the different conditions was also discussed.     

Palladium‐Catalyzed N‐Alkylation of Amides and Amines with Alcohols Employing the Aerobic Relay Race Methodology

Possibly because homogeneous palladium catalysts are not typical borrowing hydrogen catalysts and ligands are thus ineffective in catalyst activation under conventional anaerobic conditions, they had not been used in the N‐alkylation reactions of amines/amides with alcohols in the past. By employing the aerobic relay race methodology with Pd‐catalyzed aerobic alcohol oxidation being a more effective protocol for alcohol activation, ligand‐free homogeneous palladiums are successfully used as active catalysts in the dehydrative N‐alkylation reactions, giving high yields and selectivities of the alkylated amides and amines. Mechanistic studies implied that the reaction most probably proceeds via the novel relay race mechanism we recently discovered and proposed.     

Synthesis of 5-substituted 1H-tetrazoles catalyzed by ceric ammonium nitrate supported HY-zeolite

In this Letter we wish to report a simple and efficient synthetic protocol for the synthesis of 5-substituted 1H-tetrazole derivatives through the [2+3] cycloaddition of nitriles with sodium azide using ceric ammonium nitrate supported HY-zeolite as a novel catalyst. Excellent yields of the corresponding tetrazoles were obtained through this cost-effective protocol under aerobic conditions with shorter reaction time under mild reaction conditions.     

Discovery and mechanistic studies of a general air-promoted metal-catalyzed aerobic N-alkylation reaction of amides and amines with alcohols

The thermodynamically unfavorable anaerobic dehydrogenative alcohol activation to aldehydes and hydridometal species is found to be the bottleneck in metal-catalyzed N-alkylations due to a general and unnoticed catalyst deactivation by amines/amides. Thus, different from the anaerobic dehydrogenation process in borrowing hydrogen or hydrogen autotransfer reactions that require noble metal complexes or addition of capricious ligands for catalyst activation, the water-producing, exothermic, metal-catalyzed aerobic alcohol oxidation is thermodynamically more favorable and the most effective and advantageous aldehyde generation protocol. This leads to a general and advantageous air-promoted metal-catalyzed aerobic N-alkylation methodology that effectively uses many simpler, less expensive, more available, and ligand-free metal catalysts that were inactive under typical anaerobic borrowing hydrogen conditions, avoiding the use of preformed metal complexes and activating ligands and the exclusive requirement of inert atmosphere protection. This aerobic method is quite general in substrate scope and tolerates various amides, amines, and alcohols, revealing its potentially broad utilities and interests in academy and industry. In contrast to the commonly accepted borrowing hydrogen mechanism, based on a thorough mechanistic study and supported by the related literature background, a new mechanism analogous to the relay race game that has never been proposed in metal-catalyzed N-alkylation reactions is presented.     

Degradation of a polyester‐urethane coating: Physical properties

In this article we studied the evolution of thermomechanical properties of a polyester‐urethane coating during degradation under different degradation conditions, i.e., aerobic and anaerobic conditions with and without dry/wet cycling during degradation. Dynamic mechanical and thermal analyses show that under aerobic conditions the coatings become stiffer and more brittle in the glassy state. This stiffening is probably due to the increase in the amount of hydrogen bonding and the formation of oxidized groups which increase the polarity of the material and enhance the interactions of the polymer segments. However, oxidation reactions result in a considerable decrease in cross‐link density and stiffness in the rubbery state. Both changes, in the glassy and rubbery states, give rise to development of internal stresses. These stresses increase as the degradation process proceeds. Nevertheless, for samples exposed to anaerobic conditions, the stiffness remains constant in the glassy state and the cross‐link density slightly increases as a result of degradation. This reconfirms the dominance of the effect of oxidation reactions on the mechanical failure of the coatings. Oxygen permeation measurements show a more‐or‐less time‐independent diffusion coefficient and a gradual decrease in solubility of oxygen as a function of exposure time. This results in a slight decrease in oxygen permeation (mainly in the early stage of the degradation) as degradation proceeds. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 659–671     

The Role of Product Inhibition as a Yield-Determining Factor in Enzymatic High-Solid Hydrolysis of Pretreated Corn Stover

Industrially, enzymatic hydrolysis of lignocellulose at high solid content is preferable over low solids due to a reduction in processing costs. Unfortunately, the economic benefits are counteracted by a linear decrease in yield with solid content, referred to as the “solid effect” in the literature. In the current study, we investigate the contribution of product inhibition to the solid effect (7–33 % solids). Product inhibition was measured directly by adding glucose to high-solid hydrolysis samples and indirectly through variation of water content and beta-glucosidase concentration. The results suggest that the solid effect is mainly controlled by product inhibition under the given experimental conditions (washed pretreated corn stover as substrate). Cellobiose was found to be approximately 15 times more inhibitory than glucose on a molar scale. However, considering that glucose concentrations are at least 100 times higher than cellobiose concentrations under industrial conditions, glucose inhibition of cellulases is suggested to be the main cause of the solid effect.     

Compressed oxygen in drug stability experiments

A drug stability experiment accelerated by compressed oxygen was established. The stability of 10% ascorbic acid solution as a model was studied and the kinetic parameters were obtained with the newly established experimental method. Because ascorbic acid degrades under both anaerobic and aerobic conditions, the total rate constant k(total) can be expressed as: k(total)=k(anaerobic) + k(aerobic), where k(anaerobic) and k(aerobic) are the rate constants of anaerobic and aerobic degradations, respectively. The k(anaerobic) can be expressed as k(anaerobic) = A(anaerobic) x exp(-E(a,anaerobic)/RT) according to Arrhenius equation, and the k(aerobic) was found to be k(aerobic) = A(aerobic) x exp(-E(a,aerobic)/RT) x p(O2) in our study.