Oxidation Of Double Bond Research Articles

Facile ligand-regulated synthesis of defective Fe-MOF nanosheets for efficient tetracycline degradation via photoassisted enhanced activation of persulfate

In this work, defective Fe-based metal organic framework (Fe-MOF) were synthesized by a simple and eco-friendly method, in which the benzenetricarboxylic acid (BTC) ligand was partially replaced by cheap terephthalic acid (TPA) to regulate the crystalline morphology, pore structure and ligand defects. At BTC/TPA = 5/3, 4/4 and 3/5 (molar ratio), lamellar crystal (1-Fe-MOF), a mixture of lamellar crystal and nanosheets (2-Fe-MOF), and nanosheets (3-Fe-MOF) were obtained, respectively, which were distinctly different from the octahedral Fe-MOF. In the visible-light-driven persulfate (PS) activation coupled system, 3-Fe-MOF exhibited highest catalytic activity for tetracycline hydrochloride (TCH). 96.5% of TCH was removal within 20 min and the degradation kinetics rate of 0.144 min−1 was 3.5 times higher than that over the intact Fe-MOF. The enhancement in degradation activity was mainly attributed to the emergence of mesoporous structure, exposure of more metal active sites, and accelerated Fe2+/Fe3+ cycling due to more efficient charge separation and electron transfer efficiency, which favored the generation and dominant role of ∙SO4− in TCH degradation. Furthermore, demethylation, deamidation, double-bond oxidation and ring-opening reactions were inferred as the two possible degradation pathways of TCH in 3-Fe-MOF/PS/Vis system. This study provides useful guidance for the design of novel and sustainable MOFs with good application performance and industrialization potential.

Effectiveness of sulfuric acid and hydrochloric acid catalysts in the esterification of frankincense cinnamic acid with ethanol and methanol

This research aims to compare the effectiveness of sulfuric acid and hydrochloric acid catalysts in the esterification of frankincense cinnamic acid (STYRAX paraleoncomud PERK). Esterification of sulfuric acid catalyst is carried out with ethanol and for hydrochloric acid catalyst with methanol. Esterification was carried out by refluxing a mixture of 1:20 cinnamic acid - ethanol and methanol, with 3 mL of each catalyst at a temperature of 60oC for one hour. The results were rinsed with 3 x 50 mL distilled water and dried with anhydrous sodium sulfate. The results were filtered and verified for functional groups using FTIR and composition analysis using GC – MS. The results of FTIR interpretation show a decrease in absorption intensity (-OH) at 3500 cm-1 as a functional group that reacts compared to the ester results as an indication of the ongoing esterification reaction. The resulting ethyl cinnamate has a high conversion of 84.42%. Methyl cinnamate also has a distinctive ester aroma but is clearer and based on GC-MS, the content of methyl cinnamate is relatively low, namely 34.40%, the remaining cinnamic acid is 37.28%, and various side products of 28.32%. Thus, the catalyst that provides better conversion is sulfuric acid, but it requires further purification by examining the appropriate absorbent and bleaching agent. The brown color of the ester product catalyzed by sulfuric acid is thought to occur due to the oxidation of the cinnamic acid double bond by the catalyst.

Sesquiterpenoids from aged Artemisia argyi and their 3D-QSAR for anti-HBV activity

Artemisia argyi Levl. Et Vant, commonly known as "Chinese Mugwort," has been utilized in traditional Chinese medicine and cuisine for centuries. Aged Chinese Mugwort has been uncovered to possess superior quality and safety, and its ethyl acetate extract has been found to exhibit anti-hepatitis B virus (HBV) activity. In this study, twenty-five sesquiterpenoids were isolated and characterized from three-year-aged A. argyi. Among them, 14 previously undescribed sesquiterpenoids (1–14), featuring double bond oxidation or ring opening. It is hypothesized that during the aging process, sesquiterpenes undergo oxidative transformation of their double bonds to form alcohols due to external factors and inherent properties. The anti-HBV activity and cytotoxicity of all compounds were assessed in vitro using HepG 2.2.15 cells, and their structure-activity relationships were analyzed through three-dimensional quantitative structure-activity relationship (3D-QASR) techniques. The α-methylene-γ-lactone sesquiterpenoid derivatives were discovered to have potent inhibitory activity against HBV. This research may broaden the potential applications of Chinese Mugwort and offer further guidance for its development and utilization as functional food or traditional Chinese medicine.

QUANTUM CHEMICAL STUDY OF HYDROGENATION OF SUNFLOWER OIL OVER NICKEL CATALYSTS

Vegetable oil hydrogenation is vital in edible margarine production, preventing rapid deterioration caused by double bond oxidation. Hydrogenation preserves vegetable oils by countering double bond oxidation, ensuring product quality. During this process, geometric isomers, notably trans isomers, form, driven by thermodynamic stability. Nickel catalysts are crucial in the oil and ghee industry for efficient hydrogenation. Purpose. Our study investigates the hydrogenation of sunflower oil with nickel catalysts, aiming to uncover molecular dynamics and interactions shaping this process. We reveal essential insights into linoleic acid-nickel interactions, elucidating hydrogenation mechanisms and implications for glycerol production. Methodology. Quantum chemical calculations and HyperChem software were employed to study the linoleic acid-nickel interaction during hydrogenation. This study delves into the hydrogenation of sunflower oil using nickel catalysts, employing quantum chemical calculations and HyperChem software. Results. Our research elucidates robust linoleic acid-nickel interactions through optimized structures, molecular electrostatic maps, molecular orbitals, bond lengths, and energies. These findings enhance our understanding of hydrogenation mechanisms. Additionally, we found that nickel-metal interactions primarily drive glycerol production from biofuels, promising efficiency gains. Conclusion. Our study yields insights into vegetable oil hydrogenation with nickel catalysts, optimizing processes in the oil and ghee industry. Furthermore, it has implications for glycerol production from biofuels, offering potential advancements in this area.

Molecular-level evidence of early lipid transformations throughout oceanic depths

Our understanding of lipid biogeochemistry of the ocean’s interior is still in its infancy. Here we focus on early lipid transformation and the formation of lipid degradation products in the NE Atlantic Ocean (49.0°N, 16.5°W). We employed high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), a method that allows observation and elemental composition assignment of thousands of lipids in a single sample. Using these data, we infer molecular-level changes that occur during lipid transformation in the oceanic water column to shed new light on early lipid transformation processes and the formation of lipid decomposition intermediates, here termed CHO compounds (i.e., lipid-derived species that contain carbon, hydrogen and oxygen in their molecular formula). We considered the distribution of molecular rings and/or double bonds (DBE), H/C and O/C ratios, molecular diversity based on the number of mass spectral signals for monoisotopic species, and carbon number in CHO molecules. Data are elaborated for the four ocean zones, the epipelagic, mesopelagic, bathypelagic and abyssal. The highest molecular diversity characterizes CHO compounds associated with the epipelagic zone, which is explained by numerous and diverse planktonic communities inhabiting the epipelagic and by the effects of both biotic and abiotic processes on lipid transformation. Lipid transformations include crosslinking (condensation), partial degradation or fragmentation, double bond reduction, oxidation, hydrogenation, dehydrogenation and cyclization. Crosslinking likely results in a unimodal distribution of carbon number of CHO compounds, in contrast to cell lipids (referred to as Reported lipids based on the Lipid Maps Database), which have a bimodal distribution of carbon number. CHO compounds that appear to be formed by fragmentation (decrease of the number of C atoms) and ring/double bond reduction were more stable to further transformation and remained longer in the water column, i.e., these compounds were transferred deeper into the water column. Low unsaturation and fast transport to depth promotes CHO compound preservation in the water column. Dehydrogenation leads to increased unsaturation (average DBE up to 21.3), condensation, and cyclization, resulting in high molecular weight compounds with a high degree of unsaturation. Our data demonstrate that lipids with cyclic structures are more refractory than those with acyclic structures. The formation of aromatic structures is not a significant process during early lipid transformation in the oceanic water column.

Aspergillus brasiliensis-mediated biotransformation of methyl p-coumarate via phenyloxiran moiety: A predictive model for environmental bioremediation

Among the various types of industry-generated effluents, those containing phenolic compounds are serious recalcitrant. There is therefore a need to develop new technologies that emphasize the depletion of these pollutants from the environment, and that work as a viable alternative to traditional physical and chemical remediation methods. Filamentous fungi are capable of producing a great number of enzymes that efficiently transform several organic compounds. Despite the use of fungi as first-choice agents for bioremediation of hazardous contaminants, the definitions of the chemical reactions and products that are included in the fungal transformation processes still are poorly reported. In this work, Aspergillus brasiliensis efficiently transformed methyl p-coumarate under an unexpected way into two new compounds, 5-(oxiran-2-yl)benzene-1,2,3-triol (23.03%) and 4-(3-hydroxyoxiran-2-yl)benzene-1,2-diol (4.90%), along with acetophenone (72.07%). The chemical structures of derivatives were determined by gas chromatography coupled to mass spectrometry (GC-MS) analysis and a plausible bioremediation pathway for phenolic recalcitrant was proposed. Interestingly, the uncommon phenyloxirane moiety has been formed as part of the transformation from 4-vinylphenol intermediate through double bond oxidation. Certainly, our results will open new insights in the bioremediation of phenolic compounds and they will be useful guidance for future planning of other similar processes.

The Adsorption of Ozone on the Solid Catalyst Surface and the Catalytic Reaction Mechanism for Organic Components

AbstractOzone is a strong gas oxidant and is often considered as an important source of atomic oxygen. It can not only sterilize but also decompose most organic components in water. In organic reactions, it can be used for carbon‐carbon double bond oxidation. Because ozone is unstable and easy to decompose, the oxidations usually need to be carried out in the presence of low temperature or catalysts to improve the ozone utilization. The adsorption mechanisms of ozone on the surface of solid catalysts are different due to the characteristics of the ozone molecule and the different reaction conditions. In this paper, the adsorption and reaction mechanisms of ozone on solid catalyst surface are reviewed: Firstly, the ozone has weak alkalinity similar to that of CO, but the distribution of electrons in the ozone molecule exists the difference. The difference in electron distribution makes ozone to be a dipole. The central oxygen atom can accept electrons as the Lewis acid, while the terminal oxygens are electron donors to be the Lewis base. Secondly, the functional groups, which have Lewis acid and base sites, such as hydroxyl groups, can be adsorbed with the central or terminal oxygen of ozone to form a surface complex. Last, the solvents also have a critical effect on the adsorption of ozone and subsequent oxidation. According to the above mechanisms, the design and preparation of ozonation catalysts are also proposed to improve the ozonation selectivity.

The oxidative degradation of Caffeine in UV/Fe(II)/persulfate system-Reaction kinetics and decay pathways.

In this study, the degradation of caffeine was investigated by UV/Fe2+ /persulfate (PS) process. Caffeine (CAF) degradation in sole-UV, UV/Fe2+ , UV/PS, and Fe2+ /PS systems was also conducted to examine the contribution of isolated processes to CAF degradation. The effects of pH levels, the concentration of Fe2+ and PS, inorganic anions, and initial concentration of CAF on the performance of UV/Fe2+ /PS process were evaluated. Radical competitive reactions indicated both hydroxyl radicals and sulfate radicals played important roles in CAF degradation in UV/Fe2+ /PS system. Nine intermediates, among which three were detected for the first time, were identified by ultra-performance liquid chromatography/electrospray-time-of-flight mass spectrometry (UPLC/ESI-TOF-MS) and SPME (solid-phase microextraction)/GC/MS. The possible degradation pathways of CAF were proposed, among which demethylation, hydroxylation, the oxidation of olefinic double bond, and the cleavage of pyrimidine ring and imidazole ring were involved in the degradation of CAF in UV/Fe2+ /PS system. PRACTITIONER POINTS: Caffeine degradation by UV/Fe2+ /PS process was investigated. Caffeine degradation did not follow a simple pseudo-first order kinetics Chloride ions promoted CAF degradation. The anions NO3 - , SO4 2- , and H2 PO4 - exerted a negative influence on caffeine degradation. Nine intermediates were detected, and decay pathways were proposed.

The application of TS-1 materials with different titanium contents as catalysts for the autoxidation of α-pinene

Titanium-silicalite TS-1 catalysts with different titanium contents were synthesized by the hydrothermal method and characterized by means of the FTIR, UV–Vis, XRD, XRF, and SEM techniques. The studies showed that in the tested reaction system the process of isomerization of α-pinene over these TS-1 catalysts did not occur; however, the self-oxidation of α-pinene did proceed. The main directions of autoxidation of α-pinene were the double-bond oxidation and the oxidations at allylic positions 2 and 10. This work presents the explanation of the mechanism of the α-pinene self-oxidation process. In addition, isomerization and hydration products of α-pinene oxide were formed. It was found that the optimal condition for the production of the oxide is to perform the autoxidation process at the temperature of 80 °C for the TS-1 20:1 catalyst (content 1 wt%), and at the reaction time of 24 h. Under these conditions, the selectivity of α-pinene oxide was 30.25 mol%, and the conversion of α-pinene reached 41.81 mol%. In addition to the production of α-pinene oxide, verbenol, verbenone, and campholenic aldehyde can also be obtained, which are products that can find valuable applications in the cosmetics industry, in medicine, and in the production of various polymers.

In Vitro Phase I Metabolism of the Recently Emerged Synthetic MDMB-4en-PINACA and Its Detection in Human Urine Samples.

MDMB-4en-PINACA (methyl (S)-3,3-dimethyl-2-(1-(pent-4-en-1-yl)-1H-indazole-3-carboxamido)butanoate) is a recently emerged synthetic cannabinoid in Turkey. MDMB-4en-PINACA was detected in herbal material investigated by the Council of Forensic Medicine, Istanbul Narcotics Department in Turkey in April 2019. MDMB-4en-PINACA was added to the drug abuse list and quickly reported in biological samples after its first detection. In this study, the in vitro metabolism of MDMB-4en-PINACA was investigated by using a pooled human liver microsomes (HLMs) assay and liquid chromatography-high-resolution mass spectrometry (LC-HRMS). MDMB-4en-PINACA (5μmol/L) was incubated with HLMs for up to 1h, and the metabolites were identified using LC-HRMS and software-assisted data mining. The in vivo metabolism was investigated by the analysis of 22 authentic urine samples and compared to the data received from the in vitro metabolism study. Less than 7.5% of the MDMB-4en-PINACA parent compound remained after the 1h incubation. We identified 14 metabolites, which were formed via double bond oxidation, ester hydrolysis, N-dealkylation, hydroxylation, dehydrogenation and further oxidation to N-pentanoic acid or a combination of these reactions in vitro. In 10 urine samples (total n=22), MDMB-4en-PINACA was detected as the parent drug. Three of the identified main metabolites, double bond oxidation in combination with ester hydrolysis and hydroxylation metabolite (M3), MDMB-4en-PINACA butanoic acid (M14) and monohydroxypentyl-MDMB-4en-PINACA (M12), were suggested as suitable urinary markers. In vitro screening of 2,150 authentic urine samples for these identified MDMB-4en-PINACA metabolites resulted in 56 cases of confirmed MDMB-4en-PINACA consumption (2.6%).

The dietary peroxidized lipid, 13-HPODE, promotes intestinal inflammation by mediating granzyme B secretion from natural killer cells.

It is well known that consumption of a high-fat diet (HFD) promotes intestinal inflammation despite little being known about causative factors. Recent evidence implicates dietary peroxidized lipids (POLs), which are typically formed from the oxidation of polyunsaturated fatty acid double bonds, as potential contributors due to their enrichment in HFDs, ability to be formed during gastrointestinal transit, and immunogenic and cytotoxic properties. 13-HPODE, the most common dietary POL, demonstrates pro-inflammatory activity in a variety of immune cells, especially Natural Killer (NK) cells whose role in mediating intestinal inflammation remains unclear. Therefore, we set out to investigate how 13-HPODE and other POLs modulate NK-cell activity in the context of intestinal inflammation. We not only found that NK cells fully decompose exogenous 13-HPODE, but that direct treatment stimulates TNF-α and MCP1 expression as well as Granzyme B (GZMB) secretion in a dose-dependent manner. Similar results were observed upon incubation of NK cells with oxidized, but not-unoxidized, low-density lipoproteins. Secretory products from 13-HPODE-treated NK cells were able to induce Caco2 intestinal cell inflammation in the same way as exogenous GZMB with greater sensitivity in undifferentiated compared to differentiated cells. Results were recapitulated in 13-HPODE-fed mice, demonstrating both spatial and temporal patterns of elevated GZMB expression that favored acute treatments in the distal intestinal epithelium. Collectively, our results suggest that that HFD-derived POLs, like 13-HPODE, potentially contribute to intestinal inflammation by stimulating the secretion of pro-inflammatory granzymes by resident NK cells, ultimately revealing a more direct role for diet in modulating gut homeostasis and the immune environment.

Persulfate activation by oxidation biochar supported magnetite particles for tetracycline removal: Performance and degradation pathway

In this study, the oxidation biochar supported magnetite particles (OBC-Fe3O4) was prepared to activate persulfate (PS) for antibiotic tetracycline (TC) degradation. The as-prepared OBC-Fe3O4 exhibited the better catalytic performance for PS activation due to its abundant oxygen-containing groups on the surface and Fe3O4 particles. In the OBC-Fe3O4/PS system, TC was degraded and removed through the synergistic effects of catalyst's adsorption and sulfate radical (SO4•−) oxidation. The optimum conditions were determined as pH 3.0, PS concentration 10 mM and OBC-Fe3O4 dosage 0.4 g/L, which resulted in 92.3% of TC removal within 2 h. The electron spin resonance (ESR) and radicals quenching studies revealed the mechanism of TC degradation in OBC-Fe3O4/PS system included the radical and nonradical pathway involving the generation of SO4•−, •OH and 1O2, while SO4•− and •OH radicals played more dominant role in the reaction. Moreover, the intrinsic atom arrangements of carbon hybridization, defective sites and persistent free radicals (PFRs) on the catalysts also related to its catalytic efficiency. Eight transformation products were identified which mainly derived from oxidation of double bonds, loss of dimethyl amino, dehydration, oxidation of aromatic ring and cleavage of carboatomic ring of TC. Consequently, a possible degradation pathway of TC was suggested. Overall, OBC-Fe3O4 could be an economic and high-efficiency heterogeneous catalyst for PS activation to remove organic pollutants in waste water.

In vitro metabolism of magnolol and honokiol in rat liver microsomes and their interactions with seven cytochrome P substrates.

Magnolol and honokiol are the main active components of Magnolia officinalis Rehd. et Wils. The study of their interactions with liver microsomes is very important for the clinical safety of M. officinalis Rehd. et Wils. The main metabolites of magnolol and honokiol in rat liver microsomes were investigated using ultrahigh-performance liquid chromatography/mass spectrometry and their possible structures were identified. In addition, cytochrome P450 (CYP450) isoenzymes of the major rat metabolites of magnolol and honokiol were identified using a specific inhibitor. This study suggests that the CYP2E1 subtype is responsible for the oxidation of magnolol and honokiol terminal double bonds to epoxy metabolites. CYP3A4 appears to be the major subtype responsible for further hydrolytic metabolism, while CYP1A2 may promote decarboxylation of the metabolites. CYP2A6 may be the main subtype responsible for the hydrogenation of magnolol (p< 0.05). This study demonstrated that different CYP450 enzyme isoforms showed different activities in the in vitro metabolism of magnolol and honokiol in rat liver microsomes. It has certain practical applications in that we should pay attention to drug-drug interactions in clinical medications and also to drug-enzyme interactions.

Controlled modification of hyaluronic acid for photoinduced reactions in tissue engineering.

Implementation of up-to-date 3D printing methods for tissue engineering applications requires synthesis of novel materials possessing both biocompatibility and processability properties. Since the hyaluronic acid is an endogenous material it represents an attractive candidate for scaffold formation. In this work, chemical modification of hyaluronic acid with glycidyl methacrylate (HAGM) was used to produce derivatives that are capable of photoinduced cross-linking. Aiming to control the degree of substitution in hyaluronic acid by glycidyl methacrylate we developed a new quantitative method based on oxidation of double bonds in HAGM by permanganate ions. HAGM hydrogel scaffolds have been produced and examined as in vitro and in vivo.

Cleavage of double bond using metal‐loaded ZSM‐5 zeolite catalysts for renewable biochemical application

This work aimed to investigate the use of mesoporous metal‐loaded ZSM‐5 zeolites for efficient cleavage of C═C double bonds for renewable biochemical applications. In the presence of a benign H2O2, these catalysts exhibited the high catalytic activities for oxidation of double bonds in styrene and fatty acids. Selective oxidation of styrene forming benzaldehyde was first studied using mesoporous Cr/ZSM‐5 zeolite as a model reaction to evaluate the catalytic activity in the cleavage of the double bond. Oxidation of double bonds in some typical fatty acids such as oleic, erucic, and linoleic acids was carried out subsequently following the model reaction. The mesoporous Cr/ZSM‐5 zeolite showed a high conversion yield of styrene (over 85 % after 6 h reaction at 70 °C) and high selectivity for benzaldehyde (over 74 %) as well as a high conversion yield of cleavage of double bond in fatty acids. To enhance the activity of the catalyst, tungsten transition metal was loaded on the Cr/ZSM‐5 particles. The mesoporous W‐Cr/ZSM‐5 zeolite was then applied as a catalyst for oxidative cleavage of several fatty acids for the generation of useful, low molecular weight chemicals from renewable natural resources. The results showed that the mesoporous W‐Cr/ZSM‐5 zeolite provided a higher conversion of fatty acids but lower selectivity in aldehyde type products than the mesoporous Cr/ZSM‐5 zeolite. The influences of reaction conditions such as reaction time and temperature on the efficiency of oxidation were also investigated.

Oxygen-Delivery Materials: Synthesis of an Open-Cage Fullerene Derivative Suitable for Encapsulation of H2 O2 and O2.

An open-cage [60]fullerene was prepared through a multiple-step sequence based on peroxide-mediated cage-opening reactions. Key steps include repeated C60 -sensitized singlet-oxygen oxidation of electron-rich amino enol double bonds to form two lactone and two lactam moieties on the rim of the orifice. Single-crystal X-ray analysis shows that the 22-membered orifice has an ellipsoid shape with the major axis at 6.7 Å and the minor axis at 3.5 Å. Encapsulation of H2 O2 was observed under atmospheric pressure at room temperature. Oxygen is also effectively trapped during the process.

Laser Mass Spectrometry Analysis of the Formation of Phosphazene-Containing Epoxy Oligomers

The main features of two methods for the synthesis of phosphazene-containing epoxy oligomers— namely, the methods based on oxidation of double bonds in organooxyphosphazenes and on the reaction of chlorocyclophosphazenes with diphenols and the subsequent interaction of the resulting hydroxy-aryloxy phosphazenes with epichlorohydrin—were examined. Using the example of hexa- and octa-eugenol derivatives of the corresponding cyclophosphazenes, optimal conditions were established for the oxidation of allyl groups of these compounds with peroxy acids and hexa- and octa-epoxide cyclophosphazenes were characterized. It was noted that the epoxidation of eugenol derivatives of a mixture of cyclophosphazenes with three to eight phosphazo groups is accompanied by side reactions leading to the formation of P–OH bonds and the partial opening of oxirane cycles. Bisphenol A phosphazene-containing oligoepoxides were synthesized both via the stage involving the formation of hydroxy-aryloxy cyclophosphazenes and their subsequent epoxidation with epichlorohydrin and via the direct interaction of chlorocyclophosphazenes with an excess of bisphenol A (BPA) in the presence of solid alkali. In the latter case, the resulting oligomers are mixtures of the conventional epoxide and phosphazene-containing epoxy oligomers. The content of the latter can be adjusted up to 50%. The synthesized oligomers contain 1–5% phosphorus. They can be cured by conventional hardeners to form flameproof or noncombustible compositions.

Selective liquid phase oxidation of cyclohexene over magnetic Fe3O4/graphene oxide nanocomposite

Magnetic graphene based nanocomposite catalysts were used for the first time in cyclohexene oxidation reaction. Fe3O4 was found to be the active phase of Fe in the catalysts as evident from the XRD analysis of the samples. Presence of graphene as graphene oxide in the nanocomposites is confirmed from FTIR spectral analysis. The distribution of more or less spherical particles of Fe3O4 over the graphene sheets was evident from the TEM photographs. The activity of bare Fe3O4 increased drastically upon graphene incorporation. Maximum conversion of 92% was attained using tert-butyl hydroperoxide as the oxidant over the best nanocomposite catalyst in which Fe3O4 was supported over 2 wt% graphene oxide. Using H2O2, double bond oxidation was the major reaction (78.27% conversion) and 1,2-cyclohexane diol was the major product (87.89% selectivity) under the selected reaction conditions of 0.05 g of catalyst with 5 mL of acetonitrile solvent at 70 °C in the 6 h reaction between 2 mmol of cyclohexene and 10 mmol of oxidant. Catalysts recovery from the reaction mixture was very easy by the use of a magnet that in turn facilitated the effective reusability of the Fe3O4 /graphene nanocomposite. The reused catalyst was characterized using TEM and FTIR spectral analyses and it is found that the partial loss in activity can be a resultant of the oxidation of graphenic C=C and the formation of epoxy linkage and –OH groups in the sheets, which hinders the efficient electron migration during catalysis.

One-pot synthesis of α-bromo- and α-azidoketones from olefins by catalytic oxidation with in situ-generated modified IBX as the key reaction

Simple one-pot protocols for the syntheses of α-bromoketones and α-azidoketones starting from olefins have been developed by employing catalytic oxidation of the intermediary bromohydrins with in situ-generated modified IBX as the key reaction. The improved procedure involves initial formation of bromohydrin by the reaction of olefin with NBS in acetonitrile-water mixture (1:1) at rt followed by oxidation with in situ-generated 3,4,5,6-tetramethyl-2-iodoxybenzoic acid (TetMe-IBX), produced in catalytic amounts from 3,4,5,6-tetramethyl-2-iodobenzoic and Oxone. α-Bromoketones are further converted in the same pot to the corresponding α-azidoketones using NaN3/NaHCO3. The one-pot conversions are versatile for a variety of olefins that include cyclic as well as acyclic aliphatic olefins and electron-rich and electron-deficient styrenes. Chemoselective bromohydroxylation of electron-rich double bond and subsequent oxidation to the α-bromoketone is demonstrated for a substrate that contains both electron-rich and deficient double bonds.

Chemoenzymatic Synthesis of Triazololactams Structurally Related to Pancratistatin

Four tricyclic lactams that structurally resemble alkaloids with the pancratistatin skeleton were synthetized from bromobenzene by a chemoenzymatic strategy. The sequence involved enzymatic dihydroxylation, efficient stereodirected oxidation of double bonds, inter‐ or intramolecular Huisgen cycloaddition, and a solvent‐free cyclization. The complex structures were obtained in high chemical and optical purity and may be good candidates for biological testing.