Ring-opening Reaction Research Articles

Photocatalytic degradation of benzotriazole through synergy of electron donor–acceptor units and Au clusters in covalent organic frameworks

Covalent organic frameworks (COFs) have attracted great attention in photocatalysis, but the high recombination rate of photo-induced electron − hole pairs limits their photocatalytic performance. We report a synergy strategy based on the donor − acceptor (D-A) effect and Au clusters to enable the effective transfer and separation of photogenerated electrons to rationally fabricate visible light driven photocatalyst (MT-COF-Au) for the degradation of benzotriazole (BTA). MT-COF-Au displayed superior photocatalytic activity. The degradation efficiency of BTA was 93 % within 110 min, which was significantly improved 6.7 times than COF. For BTA degradation, O2− played a prominent role based on reactive species trapping experiments. The products of the last stage of the reaction were ketone, imidazole, acetamide, and nitrogen, which were formed via ring opening and isomerization reactions. MT-COF-Au could be reused for at least 5 cycles without significantly deteriorating its catalytic activity. Experiments and theory calculations confirmed the electron transfer mode and photocatalytic mechanism. This work provides new prospects for the design and synthesis of high-efficiency photocatalyst photocatalysts.

Performance evaluation of rapeseed oil-based derivatives modified hard asphalt binders: Towards greener and more sustainable asphalt additives

Hard asphalt binder is regarded as a favorable option in comparison to polymer-modified asphalt for rutting due to the benefits of cost-effectiveness and extreme stiffness behavior. However, its inherent poor ability to withstand fatigue damage and thermal cracking restricts its applications as a pavement material. This study aimed at enhancing the low-temperature and fatigue performance of hard asphalt binders with newly-developed rapeseed oil (RO)-based derivatives. Two rapeseed oil -based derivatives of epoxidized rapeseed oil (ERO) and acrylated epoxidized rapeseed oil (AERO) were laboratory synthesized through oxidation and ring-opening grafting reactions, respectively. Fourier transform infrared spectroscopy (FTIR) and Hydrogen nuclear magnetic resonance (1were conducted to confirm the successful synthesis of derivatives. Mass loss, aging index, performance grading, temperature-frequency sweep, linear amplitude sweep and bending beam rheometer test were employed to assess the modified effects of rapeseed oil-based derivatives on two types of hard asphalt binders. To further explore the differences between RO and derivatives, the properties of modified hard asphalt binders using two derivatives were compared against the performance of RO-modified hard asphalt binders. With the additional RO, ERO, and AERO, the modified hard asphalt binders had significantly improved the resistance to thermal cracking and fatigue damage at low and intermediate temperatures, respectively. RO was found to have the most positive effect on the stress relaxation and the most adverse effect on the stiffness of hard asphalt binders. While, ERO- and AERO-modified hard asphalt binders had shown better antioxidative and anti-aging performance than that of RO-modified hard asphalt binders. Additionally, AERO-modified hard asphalt binders were noticed to have improved the elasticity of hard asphalt binders owing to the formation of a polymer elastic network. According to the study, two rapeseed oil-based derivatives had shown great potential as green and sustainable asphalt modifiers on the improvement of thermal and fatigue cracking resistance with the minimal adverse effect on anti-rutting performance of the hard asphalt binders. The test results revealed that the rapeseed oil-based derivatives modified hard asphalt binders could be employed in various pavement applications with great economic and sustainable benefits.

Genetically light-enhanced immunotherapy mediated by a fluorinated reduction-sensitive delivery system

The lack of safe and efficient therapeutic agent delivery platforms restricts combined therapy’s effect, and combined cancer therapy’s multi-component delivery effect needs improvement. The novel gene delivery system SS-HPT-F/pMIP-3β-KR was proposed to construct fluorine-containing degradable cationic polymers SS-HPT-F by a mild and simple amino-epoxy ring-opening reaction. By modifying the fluorinated alkyl chain, the delivery efficiency of the plasmid was greatly improved, and the cytoplasmic transport of biomolecules was completed. At the same time, a combination plasmid (MIP-3β-KillerRed) was innovatively designed for the independent expression of immune and photodynamic proteins. Which was efficiently transported to the tumor site by SS-HPT-F. The MIP-3β is expressed as an immune chemokine realize the immune mobilization behavior. The photosensitive protein KillerRed expressed in the tumor killed cancer cells under irradiation and released the exocrine immune factor MIP-3β. The immunogenic cell death (ICD) produced by photodynamic therapy (PDT) also induced the immune response of the organism. The synergistic effect of PDT and MIP-3β mobilized the immune properties of the organism, providing light-enhanced immune combination therapy against malignant tumors. Therefore, in subcutaneous tumor-bearing and metastatic animal models, the carrier tumor growth and mobilize organism produce an immune response without systemic toxicity. This work reports the first efficient gene delivery system that achieves light-enhanced immunotherapy.

Enhanced cycloaddition between CO2 and epoxide over a bismuth-based metal organic framework due to a synergistic photocatalytic and photothermal effect

The cycloaddition reaction between CO2 and epoxide is an efficient way to convert CO2 into high value-added chemicals. Therefore, it is particularly important to develop efficient catalysts that can catalyze the reaction under mild conditions. In this work, a metal–organic framework (Bi-HHTP, consisting of bismuth (Bi) as metal dots and 2,3,6,7,10,11-hexahydroxy-triphenylene (HHTP) as organic linkers) with zigzagging corrugated topology was successfully synthesized, which shows excellent catalytic activity under visible light irradiation. Various characterizations suggest that the excellent activity is derived from the following reasons: (1) the abundant exposed Bi sites provide Lewis sites for adsorption of epoxides and CO2; (2) the free holes produced over Bi-HHTP under light irradiation which could oxidize epoxide, which consequently facilitateing the subsequent ring-opening reaction; and (3) the existence of synergistic photocatalytic and photothermal effect in Bi-HHTP. This study provides a new avenue of developing bismuth-based metal organic frameworks to promote the efficiency of cycloaddition of CO2 under mild conditions.

Cellulose pyrolysis under NH3 atmosphere for levoglucosan and pyrrole: An experimental and theoretical study

Cellulose pyrolysis for valuable levoglucosan (LG) can improve the value of cellulose utilization. Here, NH3 was introduced into cellulose pyrolysis by a fixed-bed system to investigate the effect of NH3 on the formation of LG and pyrrole, and the reaction pathways of LG and pyrrole formation were explored by combining experimental results with DFT calculations. Results showed that the highest CO yield reached 147.66 mL/g at 800 °C. The yields of H2 and CH4 significantly increased, while CO2 yield decreased. NH3 increased the content of oxygen-containing substances while inhibiting the formation of aromatic and aliphatic hydrocarbons. In addition, some nitrogen-containing products were generated, and their content increased with increasing temperature, among which, the nitrogen-containing products were mainly pyrroles. The content of LG increased about two times, and its absolute yield reached 10.96 wt% at 600 °C, which was about 4.6 times that of direct pyrolysis. DFT calculations showed that NH3 had a promoting effect on cellulose pyrolysis to produce LG, and the reaction energy barrier of the optimal pathway is 194.05 kJ/mol. Cellobiose is transferred to the glycosidic bond O-site by hydrogen transfer from the C2-site to break the glycosidic bond to form the intermediate a4-i1 and glucose. The intermediate a4-i1 was combined with NH3 to form LG via hydrogen transfer, while the resulting glucose was dehydrated to form LG by combining with NH3. For the pathway of cellulose pyrolysis to form pyrrole, NH3 promoted the deoxidation of FF to form furan, and the combination of NH3 with furan promoted furan to undergo a ring-opening reaction more than that of H2O. After the ring opening, the C2 position amino group was linked to the C5 position to form a ring, and the O atom was removed by dehydration with the formation of a hydroxyl group to form pyrrole. The reaction energy barrier for cellulose pyrolysis to form pyrrole under an NH3 atmosphere was 280.08 kJ/mol. It provided a new approach for the preparation of LG and pyrrole from cellulose.

Rhodium-Catalyzed Direct Vinylene Annulation of 2-Aryloxazolines and Cascade Ring-Opening Using a Vinyl Selenone

AbstractOver the past two decades, transition-metal-catalyzed C–H activation and the subsequent oxidative cyclization with alkynes or their surrogates has emerged as a powerful synthetic tool for fused heteroaromatics. We report a Rh(III)-catalyzed annulation and ring-opening cascade reaction with 2-aryloxazolines. By utilizing a vinyl selenone as an oxidizing acetylene surrogate, the target three-component coupling products were obtained in high yields without using a stoichiometric amount of external oxidant.

C vacancy and F decorated g-C3N4 for boosting photocatalytic ozonation of sodium p-perfluorinated nonoxybenzenesulfonate

Photocatalytic ozonation (PCO) was a novel water treatment method, but the low photo-generated electron (e-) utilization and ambiguous ROS formation mechanism restrained its performance. Herein, C vacancy and F co-decorated g-C3N4 (FCN_Cv) was designed to accelerate the PCO performance with sodium p-perfluorinated nonoxybenzenesulfonate (OBS) acting as model pollutant. Comparative characterizations revealed that FCN_Cv remained the inherent structure of g-C3N4 (BCN), and had an enhanced conduction band potential, narrower band gap and longer e- lifetime. FCN_Cv exhibited the greater activity over BCN, with 99.3 % OBS removal in 30 min but only 78.3 % for BCN during PCO process. •OH was the main ROS for degrading OBS. The greater •OH yield was obtained by FCN_Cv PCO process because of the increase of e- utilization. On one hand, the two electrons reduction of O2 into H2O2 on FCN_Cv was accelerated, which triggered the peroxone reaction between photogenerated-H2O2 and O3. On the other hand, the direct one electron reduction of O3 by e- also accounted for •OH generation. 17 kinds of intermediates were detected and the OBS degradation routes were inferred, which was involved with hydroxylation, C-O cleavage and aromatic ring opening reactions. Overall, this study demonstrated the feasibility of decorating F element and C vacancy on g-C3N4 in enhancing e- utilization and •OH generation during PCO process as well as deepened the understanding of fate of OBS in PCO process.

Thermoresponsive membrane based on UCST-type organoboron polymer for smart gating and self-cleaning

Thermoresponsive polymers can endow membranes with tunable separation and self-cleaning performance. However, up to now, there have been only very limited choices of thermoresponsive polymers for the fabrication of smart membranes. Herein, thermoresponsive membranes based on UCST-type organoboron polymer (Poly(CPBA)) were fabricated for the first time. Poly(CPBA) synthesized via a nucleophilic ring-opening reaction with Poly(GMA) and 3-carboxyphenylboronic acid has shown typical thermoresponsive behavior in water and water/ethanol mixture. Under vacuum conditions, Poly(CPBA) formed the cross-linked boroxine network on the membrane surface via a dehydration-induced condensation reaction. The reversible conformational change of Poly(CPBA) near UCST acted as a smart “gating” to regulate both pore size and surface properties of the membrane. When the temperature exceeded UCST, the fully extended polymer chains provided a strong washing force to remove contaminants, resulting in effective self-cleaning performance (FRR up to 99.2 %). In particular, due to the presence of the boroxine network, the polymer chains were firmly “stuck” on the membrane surface, providing stable performance and superior repeatability of the composite membrane.

Application of Fluorescent Carbon Dots as Catalysts for the Ring-Opening Reaction of Epoxides.

Considering the increased anthropogenic emissions of CO2 into the atmosphere, it is important to develop economic incentives for the use of CO2 capture methodologies. The conversion of CO2 into heterocyclic carbonates shows significant potential. However, there is a need for suitable organocatalysts to reach the required efficiency for these reactions. Given this, there has been an increasing focus on the development of organocatalytic systems consisting of a nucleophile and a hydrogen bond donor (HBD) so that CO2 conversion can occur in ambient conditions. In this work, we evaluated the potential of fluorescent carbon dots (CDs) as catalytic HBDs in the ring-opening reaction of epoxides, which is typically the rate-limiting step of CO2 conversion reactions into heterocyclic carbonates. The obtained results demonstrated that the CDs had a relevant catalytic effect on the studied model reaction, with a rate constant of 0.2361 ± 0.008 h-1, a percentage of reactant conversion of 70.8%, and a rate constant enhancement of 32.2%. These results were better than the studied alternative molecular HBDs. Thus, this study demonstrated that CDs have the potential to be used as HBDs and employed in organocatalyzed CO2 conversion into value-added products.

Utilization of catfish fat by-products for the biological base oils synthesis

In this work, catfish fat by-product was utilized as feedstock in the synthesis of biological base oils. The study performs the effect of parameters on the reaction yield. 91.2% in (H2O2/CH3COOH/C=C) molar ratio of 4.5/1.5/1.0, the temperature of 50 oC, and 3 hours reaction time. The yield of the ring-opening reaction of epoxy with acetic anhydride reached at 90.2% in (acetic anhydride/epoxy) molar ratio of 1.5/1.0, the temperature of 95 oC, and 4.5 hours reaction time. The main functional groups of catfish oil starting material, epoxy catfish oil, and polyester catfish oil final product were identified by FT-IR and 1H-NMR spectral analysis methods. The observed results show that the catfish oil epoxidation reaction with a mixture of H2O2 and CH3COOH and the ring-opening reaction of epoxy with (CH3CO)2O, H2SO4 catalyst has occurred strongly and obtained product of catfish polyester oil could use as an alternative to mineral base oils and an environmentally friendly product.

Removal of ofloxacin using a porous carbon microfiltration membrane based on in-situ generated •OH

This study investigated the removal performance of ofloxacin (OFL) by a novel electro-Fenton enhanced microfiltration membrane. The membranes used in this study consisted of metal-organic framework derived porous carbon, carbon nanotubes and Fe2+, which were able to produce hydroxyl radicals (•OH) in-situ via reducing O2 to hydrogen peroxide. Herein, membrane filtration with bias not only concentrated the pollutants to the level that could be efficiently treated by electro-Fenton but also confined/retained the toxic intermediates within the membrane to ensure a prolonged contact time with the oxidants. After validated by experiments, the applied bias of −1.0 V, pH of 3 and electrolyte concentration of 0.1 M were the relatively optimum conditions for OFL degradation. Under these conditions, the average OFL removal rate could be reach 75% with merely 5% membrane flux loss after 4 cycles operation by filtrating 1 mg/L OFL. Via decarboxylation reaction, piperazinyl ring opening, dealkylation and ipso substitution reaction, etc., OFL could be gradually and efficiently degraded to intermediate products and even to CO2 by •OH. Moreover, the oxidation reaction was preferred to following first-order reaction kinetics. This research verified a possibility for antibiotic removal by electro-enhanced microfiltration membrane.

Eco-Friendly Depolymerization of Alginates by H2O2 and High-Frequency Ultrasonication

Marine biomass has attracted attention as an environmentally sustainable energy source that can replace petroleum-based resources. Alginates, the main natural polysaccharides extracted from seaweeds, are used in various fields, such as food, pharmaceuticals, and chemical raw materials. Because the versatile applications of alginates depend on their physicochemical properties, which are controlled by their molecular weights, proper alginate depolymerization should be established. Previous approaches have limitations such as long reaction times and environmental issues. In this study, we report eco-friendly alginate depolymerization using hydrogen peroxide (H2O2)-induced oxidative decomposition and high-frequency ultrasonication. In oxidative decomposition, the depolymerization tendency depends on both the temperature and the use of iron oxide catalysts that can promote the Fenton reaction. Ultrasonication is effective in promoting selective depolymerization and ring-opening reactions. Oligo-alginates obtained through the precise molecular weight regulation of alginate offer potential applications in medical devices and platform chemicals.

Novel Environmentally Responsive Polyvinyl Polyamine Hydrogels Capable of Phase Transformation with Temperature for Applications in Reservoir Profile Control.

Hydrogel has been widely used in reservoir regulation for enhancing oil recovery, however, this process can experience negative influences on the properties and effects of the hydrogels. Therefore, developing novel hydrogels with excellent environmental responsiveness would improve the formation adaptability of hydrogels. In this study, novel polyvinyl polyamine hydrogels were synthesized by a ring-opening addition reaction between polyvinyl polyamines and polyethylene glycol glycidyl ether. The results of atomic force microscopy and transmission electron microscopy showed that the polyvinyl polyamine gel had a porous and irregular bulk structure and was endowed with water storage. With the temperature rising from 30 °C to 60 °C, the transmittance of diethylenetriamine hydrogel decreased from 84.3% to 18.8%, indicating that a phase transition had occurred. After the polyvinyl polyamine hydrogel with low initial viscosity was injected into the formation in the liquid phase, the increase of the reservoir temperature caused it to turn into an elastomer, thereby migrating to the depth of the reservoir and achieving effective plugging. Polyvinyl polyamine hydrogel could improve the profile of heterogeneous layers significantly by forcing subsequent fluids into the low permeability zone in the form of elastomers in the medium temperature reservoirs of 40-60 °C. The novel environmentally responsive polyvinyl polyamine hydrogels, capable of phase transformation with temperature, exhibited superior performance in recovering residual oil, which was beneficial for applications in reservoir profile control and oilfield development.

PBSeT/lignin: A complete bio-based biodegradable plastic with excellent mechanical and anti-UV properties

Herein, a complete bio-based biodegradable plastic with excellent properties was fabricated based on Poly (butylene sebacate-co-terephthalate) (PBSeT) and lignin. Moreover, a biodegradable epoxidized soybean oil (ESO) was used as the compatibilizer through the ring-opening reaction between ESO and the hydroxyl groups of lignin and PBSeT during the reactive extrusion. The results show that the plastics had excellent properties, the tensile strength and the elongation at break could reach 13.04 MPa and 328.33 %, respectively. Moreover, the addition of lignin endowed PBSeT with good UV resistance. Conclusively, this strategy expands the application of lignin in the degradable polyester matrix and broadens the application of lignin accordingly.

MEDT Study, hemisynthesis via regioselective ring opening of α-Himachalene-Epoxides, ADME survey and docking studies designed to target coronavirus and HIV-1

The ring-opening reaction of the two diepoxides, α-himachalenes 6 and 7, with aluminum lithium hydride (LiAlH4) in ether produced the title compounds C15H24O2 sesquiterpene alcohol. Both experimentally and conceptually, the regio- and stereospecificity of this ring opening reaction were investigated using the Molecular Electron Density Theory (MEDT). The Parr functions and the energy study correctly predicted the best interaction to be between the C13 carbon and the hydride, as evidenced by the attained regio- and stereo-specificity revealed through the experimental research. Moreover, the alcohol 8 is obtained from a kinetic and thermodynamic control while the alcohol 9 is obtained only by a kinetic control, in the maximum conformity with the findings of the experiments. In addition, the performed docking calculations to examine the coronavirus and HIV-1 activities of the products 1–9 revealed that alcohol 9 has a higher affinity against coronavirus while β-himachalene 1 against the HIV-1.

Magnesium catalyzed asymmetric ring-opening reactions of high-strained three membered cyclic systems

Magnesium catalyzed asymmetric ring-opening reactions of high-strained three membered cyclic systems

Thermodynamic and kinetic aspects of epichlorohydrin acetolysis under catalysis by triethylamine in solvents of various polarities

The ring-opening reaction of epichlorohydrin with acetic acid in aprotic solvents under the catalysis by triethylamine in the temperature range of 313–353 K was studied by methods of chemical kinetics. The binary mixtures epichlorohydrin:tetrahydrofuran and epichlorohydrin:nitrobenzene (1:1 vol.) were chosen as solvents, which allowed preserving a significant excess of epichlorohydrin in the reaction system and varying the solvent polarity in the range of =15.1–28.7. The kinetic law of the reaction was established for the studied reaction series, and the observed and catalytic constants were obtained for epichlorohydrin acetolysis. It was demonstrated that the increase in temperature and solvent polarity accelerates the reaction. The temperature dependences plotted in Arrhenius coordinates exhibited linear behavior. The joint effect of temperature and solvents on activation parameters (energy, enthalpy, entropy, and Gibbs energy) of the reaction was investigated. The values of Gibbs energy of activation were found to be similar in all studied reaction systems. The isokinetic temperature of the epichlorohydrin acetolysis in epichlorohydrin and binary solvents epichlorohydrin:tetrahydrofuran and epichlorohydrin:nitrobenzene was established, and the enthalpy–entropy compensation effect was stated by correlation methods.

Upcycling spent lithium battery cathodes into efficient PMS catalysts for organic contaminants degradation

The rapid accumulation of spent lithium-ion batteries (SLIBs) poses a global challenge in terms of their disposal and management. Considering the substantial quantity of transition metals contained in SLIBs, the preparation of derived catalysts for environmental remediation has emerged as a promising approach for the recycling of SLIBs. Herein, the citric acid-based sol-gel method was employed to synthesize the catalyst from SLIBs. The derived spent cathode material (LiNixCoyMn1−x-yO2, NCM) composites exhibit superior catalytic activity and display higher adaptability to the environment, effectively removing typical azo dye, methylene blue (MB), as well as various organic contaminants, sulfamethoxazole (SMX), levofloxacin (LVF) and rhodamine B (RhB) in 30 min. The Co2+ and Mn2+ ions in the catalyst play a crucial role in activating PMS to generate 1O2 and O2•−. The degradation of MB proceeds through several reaction pathways, including demethylation, oxidation, and ring-opening reactions, as confirmed by the Fukui function and UPLC-QTOF-MS analyses. The assessment of toxicity in the degradation products was conducted using T.E.S.T. and ECOSAR 2.0. This proposed method can be highly suggested as a promising strategy for the recycling and utilization of SLIBs, transforming them into efficient catalysts for PMS systems in environmental remediation.

Synthesis, crystal structure, DFT calculation and Hirshfeld surface analysis of N-(4-methyl phenyl)-2-(3-nitro-benzamido) benzamide

A new bis amide N-(4-methylphenyl)-2-(3-nitrobenzamide) benzamide was synthesized from a ring-opening reaction of 2-(3-nitrophenyl)-4H-benzoxazin-4-one, with 4-methyl aniline in a shorten reaction time (1.0 min) and characterized using different spectroscopic techniques (FT-IR, 1H-NMR, 13C-NMR) and single-crystal X-ray diffraction (XRD). In the crystal lattice, the molecules are linked by N–H···O and C–H···O hydrogen bonds. The Hirshfeld surface analysis mapped over shape index, curvedness indices, dnorm revealed strong H...H and H...O/O...H and intermolecular connections a key contributors to crystal packing structure. Density functional theory (DFT) calculations were applied with B3LYP/6-311G(d) level to provide theoretical data along with HOMO-LUMO electronic energy with the MEP map.
 KEY WORDS: Benzamide, Crystal structure, DFT calculation, Hirshfeld surface
 Bull. Chem. Soc. Ethiop. 2024, 38(1), 229-239. DOI: https://dx.doi.org/10.4314/bcse.v38i1.17

Quantum Mechanical/Molecular Mechanical Elucidation of the Catalytic Mechanism of Leukotriene A4 Hydrolase as an Epoxidase.

Leukotriene A4 hydrolase (LTA4H) functions as a mono-zinc bifunctional enzyme with aminopeptidase and epoxidase activities. While the aminopeptidase mechanism is well understood, the epoxidase mechanism remains less clear. In continuation of our prior research, we undertook an in-depth exploration of the LTA4H catalytic role as an epoxidase, employing a combined SCC-DFTB/CHARMM method. In the current work, we found that the conversion of LTA4 to leukotriene B4 (LTB4) involves three successive steps: epoxy ring opening (RO), nucleophilic attack (NA), and proton transfer (PT) reactions at the epoxy oxygen atom. Among these steps, the RO and NA stages constitute the potential rate-limiting step within the entire epoxidase mechanism. Notably, the NA step implicates D375 as the general base catalyst, while the PT step engages protonated E271 as the general acid catalyst. Additionally, we delved into the mechanism behind the formation of the isomer product, Δ6-trans-Δ8-cis-LTB4. Our findings debunked the feasibility of a direct LTB4 to iso-LTB4 conversion. Instead, we highlight the possibility of isomerization from LTA4 to its isomeric conjugate (iso-LTA4), showing comparable energy barriers of 5.1 and 5.5 kcal/mol in aqueous and enzymatic environments, respectively. The ensuing dynamics of iso-LTA4 hydrolysis subsequently yield iso-LTB4 via a mechanism akin to LTA4 hydrolysis, albeit with a heightened barrier. Our computations firmly support the notion that substrate isomerization exclusively takes place prior to or during the initial substrate-binding phase, while LTA4 remains the dominant conformer. Notably, our simulations suggest that irrespective of the active site's constrained L-shape, isomerization from LTA4 to its isomeric conjugate remains plausible. The mechanistic insights garnered from our simulations furnish a valuable understanding of LTA4H's role as an epoxidase, thereby facilitating potential advancements in inhibitor design.