Ring-opening Reaction Research Articles

A sustainable rapeseed oil-based bio-additive designed for hard asphalt binders: Performance, environmental, and economic assessment

The inherent properties of hard asphalt binder give it both mechanical and economic benefits, rendering it a naturally advantageous material for preventing permanent deformation at higher temperatures. However, its poor resistance to thermal and fatigue cracking limits its application in the paving industry. This study aimed to improve the low-temperature and fatigue performance of hard asphalt binders by using the newly developed vegetable oil-based sub-epoxidized rapeseed oil (SERO). Two SEROs with epoxidation degree of 49.1% and 98.1% were synthesized through an oxidation reaction, respectively. Subsequently, the microstructural characteristics of SEROs were examined by Fourier transform infrared spectroscopy (FTIR) and Hydrogen nuclear magnetic resonance tests. The anti-oxidative aging properties of SERO modified hard asphalt binders were investigated through the utilization of mass loss and aging index. Additionally, the comprehensive rheological properties of SERO modified hard asphalt binders were explored via dynamic shear rheometer and bending beam rheometer tests. Furthermore, the modification mechanism of SERO on hard asphalt binders was confirmed through the quantitative analysis using the FTIR test. The findings suggested the improvement in anti-volatilization and anti-oxidative aging performance of bio-modified hard asphalt binders, which was positively related to the epoxidation degree of SERO. A notable softening effect of SERO on the hard asphalt binders was observed, which enhanced their resistance to thermal and fatigue cracking at lower and intermediate temperatures. The epoxy groups within SERO engaged in ring-opening reactions, forming a new oxygen bridge bond by combining with the unsaturated double bond presented in the asphalt. Consequently, this process resulted in the formation of cross-linked structures within bio-modified hard asphalt binders, thereby enhancing the elasticity. Notably, this phenomenon was most conspicuous in the SERO-H modified 50# binder. Finally, the environmental and economic assessment of SERO modified hard asphalt binders were conducted by the techno-economic method and the emission factors technique. The data revealed that the production of one ton of SERO modified hard asphalt binders could reduce the production costs by about 30%, energy consumption and CO2 emissions by around 20% in contrast to styrene–butadiene–styrene block copolymer modified asphalt binders. Hence, the substantial economic and environmental advantages make SERO an attractive bio-renewable additive for sustainable pavements.

Triflic Acid-Promoted 1,2-Amino Migration Reactions in α-Arylaminoacrylamides: Access to Substituted β-Aminoamides.

A straightforward synthesis of substituted β-aminoamides from α-arylamino-β-hydroxyacrylamides, α-arylamino-β-oxoamides, or their tautomeric mixture has been described. The (E)-enol triflate intermediates are readily generated in situ from these substrates in the presence of triflic anhydride (Tf2O) and triethylamine (Et3N) in a chemoselective manner and undergo triflic acid (TfOH)-promoted cyclization and ring-opening reactions with alcohols to deliver the desired products. The one-pot two-step synthetic protocol features the use of readily available starting materials, mild reaction conditions, high chemoselectivity, operational simplicity, and a wide range of synthetic potential of the products.

Degradation of organophosphate esters by UV/persulfate: Kinetic, mechanistic and toxicity evaluation

With the ban of brominated flame retardants, organophosphate esters (OPEs) have been widely used. The ultraviolet combined sodium persulfate (UV/PS) process is a promising advanced oxidation process (AOPs), which effectively removes organic micropollutants by generating various reactive substances such as hydroxyl radical (•OH) and sulfate radical (SO• 4−). The degradation kinetics, influencing factors, degradation path, and toxicity of three organic phosphates, trimethyl phosphate (TMP), tris (2-chloroethyl) phosphate (TCEP) and triphenyl phosphine oxide (TPPO) were studied. The results showed that UV/PS could degrade OPEs efficiently, and 254 nm UV light was more conducive to the degradation of OPEs than 365 nm UV light, and the degradation of OPEs accelerated with the increase of PS concentration. Under acidic and neutral conditions, UV/PS was more conducive to the degradation of OPEs, and the concentration of NOM was inversely proportional to the degradation rate of OPEs, Cl− and SO42− had almost no effect on the degradation of OPEs, while HCO3− has an inhibitory effect on the degradation of OPEs. UV/PS also has a good effect on the degradation of OPEs in actual water. •OH and SO• 4−, as the main reactive radicals, participate in the degradation of OPEs. Hydroxylation, debenzene ring, demethylation, and ring opening reactions are the main reactions occurring in the process of OPEs degradation. The theoretical toxicity value of most intermediates is lower than that of the initial OPEs. This study reveals the transformation of OPEs in the UV/PS system and provides a new idea for wastewater treatment of OPEs.

Discovery of an Azabicyclo[2.1.1]hexane Piperazinium Salt and Its Application in Medicinal Chemistry via a Rearrangement.

Herein we report the discovery of an azabicyclo[2.1.1]hexane piperazinium methanesulfonate salt from an unexpected rearrangement reaction in the preparation of ligand-directed degraders (LDDs). This bench-stable compound was found to be a versatile electrophile in a ring-opening reaction with various types of nucleophiles. Its utility as a versatile medicinal chemistry building block is further demonstrated in the synthesis of an LDD compound targeting degradation of the androgen receptor.

Comparative study on oxidation reaction characteristics of different forms of hydroxyl‑containing coal molecules

Hydroxyl groups in coal contain a variety of forms. It is very important to study the reaction characteristics of different forms of hydroxyl‑containing coal molecules for revealing the mechanism of coal spontaneous combustion and the development of inhibitor. Therefore, this study focuses on the influence and reaction mechanism of the molecular oxidation reaction stage of different forms of hydroxyl‑containing coal by molecular dynamics, quantum chemistry and FTIR. The results show that there are two paths in the reaction of different hydroxyl structure: dehydrogenation and hydroxyl addition. The consumption rate of polyhydroxyl coal molecules (88 %) is higher than that of monohydroxyl (18 %), and the consumption rate of 2-methylphenol (58 %) is higher than that of other positions. The reaction of monohydroxyl coal is mainly influenced by aliphatic hydrocarbon, and the reaction of polyhydroxyl coal is mainly influenced by hydroxyl group. Quantum chemical calculation shows that the reactivity difference of different forms of hydroxy‑containing coal molecules is due to the active sites. Furthermore, the free energy barrier of hydroxyl addition reaction is 73–89 KJ /mol and the heat release is 52–56 KJ /mol, which can increase the trend of benzene ring-opening reaction.

A singular chromatographic column breakthrough: Achieving full polarity range separations with the epoxy propanol molecular cage bonded silica stationary phase

The epoxy propanol molecular cage bonded silica stationary phase, RCC3-GLD@silica, synthesized through the ring-opening reaction of secondary amine with epoxy propanol using RCC3-R as the scaffold unit, was successfully prepared as confirmed by infrared spectroscopy, thermogravimetric analysis, and nitrogen adsorption-desorption characterization. This stationary phase demonstrated excellent separation performance in both reversed-phase and hydrophilic chromatography modes, effectively separating a wide variety of compounds including alkylbenzenes, polycyclic aromatic hydrocarbons, phenols, anilines, sulfonamides, nucleosides, amino acids, sugars, and acids. The development of RCC3-GLD@silica benefits from the synergistic effects of its hydrophobic and hydrophilic actions, as evidenced by the U-shaped characteristic of the retention factor for nucleoside compounds with changes in the aqueous content of the mobile phase, further confirming the simultaneous presence of reversed-phase and hydrophilic chromatography mechanisms. Not only did this stationary phase successfully separate 33 compounds in reversed-phase chromatography mode, but it also separated 54 compounds in hydrophilic interaction chromatography mode, showcasing its broad separation capability from weakly polar to strongly polar compounds on a single chromatographic column. This indicates a wide application prospect in the field of chromatographic analysis.

Synthesis of Methylated, Hydroxylated, and Aminated Metallaaromatics via Ring-Opening Reactions of the Fused Three-Membered Ring Units

Synthesis of Methylated, Hydroxylated, and Aminated Metallaaromatics <i>via</i> Ring-Opening Reactions of the Fused Three-Membered Ring Units

Cathode Electrolyte Interphase Engineering for Prussian Blue Analogues in Lithium-Ion Batteries.

The increasing use of low-cost lithium iron phosphate cathodes in low-end electric vehicles has sparked interest in Prussian blue analogues (PBAs) for lithium-ion batteries. A major challenge with iron hexacyanoferrate (FeHCFe), particularly in lithium-ion systems, is its slow kinetics in organic electrolytes and valence state inactivation in aqueous ones. We have addressed these issues by developing a polymeric cathode electrolyte interphase (CEI) layer through a ring-opening reaction of ethylene carbonate triggered by OH- radicals from structural water. This facile approach considerably mitigates the sluggish electrochemical kinetics typically observed in organic electrolytes. As a result, FeHCFe has achieved a specific capacity of 125 mAh g-1 with a stable lifetime over 500 cycles, thanks to the effective activation of Fe low-spin states and the structural integrity of the CEI layers. These advancements shed light on the potential of PBAs to be viable, durable, and efficient cathode materials for commercial use.

Simultaneously Selective Separation of Zearalenone and Four Aflatoxins From Rice Samples Using Co-Pseudo-Template Imprinted Polymers With MIL-101(Cr)-NH2 as Core.

A novel approach for the simultaneous separation of zearalenone (ZEN) and four types of aflatoxins (AFB1, AFB2, AFG1 and AFG2) from rice samples was presented. This approach utilized modified MIL-101(Cr)-NH2 as core, with molecularly imprinted polymers (MIPs) serving as the shell. The MIL-101(Cr)-NH2 was prepared via ring-opening reaction, while the imprinted polymers were synthesized using warfarin and 4-methylumbelliferyl acetate as co-pseudo template, ethylene glycol dimethacrylate as the cross-linker and azobisisobutyronitrile as initiator. The resulting co-pseudo-template-MIPs (CPT-MIPs) were thoroughly characterized and evaluated. Adsorption studies demonstrate that the adsorption process of CPT-MIPs follows a chemical monolayer adsorption mechanism, with imprinted factors ranging from 1.24 to 1.52 and selective factors ranging from 1.29 to 1.52. Self-made columns were prepared, and the method for separation was developed and validated. The limit of detections ranged from 0.12 to 2.09μg/kg, and the limit of qualifications ranged from 1.2 to 6.25μg/kg. To assess the reliability of the method, ZEN and AFs were spiked at three different levels, and the recoveries ranged from 79.53 to 94.58%, with relative standard deviations of 2.90-5.78%.

Palladium/Amine Dual-Catalyzed Tsuji-Trost Fluoroallylation of Aldehydes with gem-Difluorinated Cyclopropanes.

We herein disclose the Pd/amine dual-catalyzed ring-opening cross-coupling reaction between gem-difluorinated cyclopropanes (gem-F2CPs) with aldehydes, which enables the diversity-oriented synthesis (DOS) of 2-fluoroallylic aldehydes bearing all-carbon quaternary centers with features of broad scope and excellent functional group tolerance. The synthetic value of this Tsuji-Trost system was further demonstrated by late-stage functionalization of natural product-derived gem-F2CPs and the diverse synthesis of various fluoroallylic aldehyde derivatives, including alcohol, alkyne, alkene, and amine.

Construction of Zwitterionic Coatings with Lubricating and Anti-Adhesive Properties for Invisible Aligner Applications.

Invisible aligners have been widely used in orthodontic treatment but still present issues with plaque formation and oral mucosa abrasion, which can lead to complicated oral diseases. To address these issues, hydrophilic poly(sulfobetaine methacrylate) (polySBMA) coatings with lubricating, antifouling, and anti-adhesive properties have been developed on the aligner materials (i.e., polyethylene terephthalate glycol, PETG) via a simple and feasible glycidyl methacrylate (GMA)-assisted coating strategy. Poly(GMA-co-SBMA) was grafted onto the aminated PETG surface via the ring-opening reaction of GMA (i.e., "grafting to" approach to obtain G-co-S coating), or a polySBMA layer was formed on the GMA-grafted PETG surface via free radical polymerization (i.e., "grafting from" approach to obtain G-g-S coating). The G-co-S and G-g-S coatings significantly reduced the friction coefficient of PETG surface. Protein adsorption, bacterial adhesion, and biofilm formation on the G-co-S- and G-g-S-coated surfaces were significantly inhibited. The performance of the coatings remained stable after storage in air or artificial saliva for 2 weeks. Both coatings demonstrated good biocompatibility in vitro and did not cause irritation to the oral mucosa of rats in vivo over 2 weeks. This study proposed a promising strategy for the development of invisible aligners with improved performance, which is beneficial for oral health treatment. This article is protected by copyright. All rights reserved.

Enhancing the Lewis acidity of single atom Tb via introduction of boron to achieve efficient photothermal synergistic CO2 cycloaddition

Nowadays, it is becoming increasingly urgent to lower the escalating carbon dioxide (CO2) to reduce greenhouse effect. Fortunately, it is an ideal strategy by using the inexhaustible solar energy as the driving force to manipulate the cycloaddition reaction, the atomic efficiency of which is 100 %. This work represents the first attempt on utilization of rare-earth metal Tb with atomic dispersion, and the structure of Tb coordinated with 4 N-atoms and 2B-atoms was constructed on interconnected carbon hollow spheres. The introduction of electron-deficient B reduces the electron density of Tb, thereby boosting Lewis acidity and promoting the occurrence of ring-opening reaction. The mechanism exploration enunciates that TbN4B2/C is a photothermal synergistic catalyst, the combined action of photogenerated electrons and strong Lewis acidic site of Tb reduces the free energy of the rate-determining step, and then improving the yield of cyclic carbonate up to 739 mmol g-1h−1.

Mechanistic study of OH radical-promoted decomposition of polycyclic aromatic hydrocarbon oxyradicals

Polycyclic aromatic hydrocarbons (PAHs) are widely recognized for their detrimental impact on human health and the atmospheric environment. One of the primary challenges in mitigating these effects is the efficient and rapid decomposition of PAH oxyradicals, a byproduct of PAH oxidation. This study aims to elucidate the promoting mechanism of hydroxyl (OH) radicals on the decomposition of PAH oxyradicals. Employing density functional theory and transition state theory, we systematically investigate the decomposition mechanism of PAH oxyradicals under the influence of OH radicals. Our findings indicate that the interaction between OH radicals and PAH oxyradicals constitutes a pivotal oxidation process within flames. Notably, PAH oxyradicals are more inclined to undergo pyrolysis subsequent to their reaction with OH radicals within a flame, as opposed to direct pyrolysis. This observation underscores the role of OH radicals in facilitating the decomposition of PAH oxyradicals in flame conditions. Further analysis reveals that OH radicals can effectively react with various forms of PAH oxyradicals—zigzag, free, and armchair—leading to the formation of OH-OPAH compounds characterized by HO-C-O functional groups. Importantly, this addition reaction between OH radicals and PAH oxyradicals is found to be independent of the edge types of the PAH oxyradicals. The pyrolysis of OH-OPAH predominantly yields products such as COOH, CO2, and PAHs with five-membered rings, with COOH emerging as the primary oxidation product. This pyrolysis predominantly proceeds via a ring-opening reaction, rather than through cyclization. This study also reveals that the likelihood of PAH oxyradical pyrolysis increases with the number of free edges surrounding the oxygen-containing functional groups. Furthermore, the oxidation activity of the HO-C-O functional group is demonstrated to be more potent than that of the C-O functional group, significantly enhancing the reactivity of PAH oxyradical degradation in the presence of OH radicals. These insights not only contribute to refining the combustion model of PAH oxidation but also advance our understanding of PAH oxyradical decomposition. Such knowledge is crucial for the development and optimization of control technologies targeting PAH pollutants emanating from combustion devices.

Green bio-derived epoxidized linseed-oil plasticizer improves the toughness, strength, and dimensional stability of furfuryl alcohol-modified wood

Furfuryl alcohol (FA) modification represents a sustainable approach to wood modification; however, it significantly reduces the toughness of the wood, limiting its practical applications. This study introduced epoxidized linseed oil (ELO) as an environmentally friendly and bio-derived plasticizer to enhance the toughness and mechanical properties of FA-modified wood. Microstructural analyses confirmed the integration of FA and ELO into the cellular structure of the wood. The chemical interactions between the epoxy groups of ELO and hydroxyl groups of FA were characterized using Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy, illustrating that a ring-opening reaction occurred that grafted the long flexible aliphatic chains of ELO onto the FA chains, thereby enhancing the chain mobility and flexibility. This interaction significantly decreased the crosslinking density, thereby achieving toughening. FA–ELO modification resulted in significantly enhanced dimensional stability and mechanical properties. Specifically, the anti-swelling efficiency exceeded 80 %, while the modulus of elasticity, modulus of rupture, and along-grain compressive strength increased by up to 35.0 %, 36.8 %, and 45.7 %, respectively. Additionally, significant enhancements in the elongation at break and impact strength were achieved, at 369.1 % and 72.4 %, respectively. The loss factor also increased. The optimal ELO content was 20 wt%. This study effectively demonstrated how ELO mitigates the brittleness of FA-modified wood and supports its application in high-value fields such as construction.

Harnessing Enhanced Flame Retardancy in Rigid Polyurethane Composite Foams through Hemp Seed Oil-Derived Natural Fillers.

Over the past few decades, polymer composites have received significant interest and become protagonists due to their enhanced properties and wide range of applications. Herein, we examined the impact of filler and flame retardants in hemp seed oil-based rigid polyurethane foam (RPUF) composites' performance. Firstly, the hemp seed oil (HSO) was converted to a corresponding epoxy analog, followed by a ring-opening reaction to synthesize hemp bio-polyols. The hemp polyol was then reacted with diisocyanate in the presence of commercial polyols and other foaming components to produce RPUF in a single step. In addition, different fillers like microcrystalline cellulose, alkaline lignin, titanium dioxide, and melamine (as a flame retardant) were used in different wt.% ratios to fabricate composite foam. The mechanical characteristics, thermal degradation behavior, cellular morphology, apparent density, flammability, and closed-cell contents of the generated composite foams were examined. An initial screening of different fillers revealed that microcrystalline cellulose significantly improves the mechanical strength up to 318 kPa. The effect of melamine as a flame retardant in composite foam was also examined, which shows the highest compression strength of 447 kPa. Significantly better anti-flaming qualities than those of neat foam based on HSO have been reflected using 22.15 wt.% of melamine, with the lowest burning time of 4.1 s and weight loss of 1.88 wt.%. All the composite foams showed about 90% closed-cell content. The present work illustrates the assembly of a filler-based polyurethane foam composite with anti-flaming properties from bio-based feedstocks with high-performance applications.

Surface thermal-curing phosphorus-containing coated rigid polyurethane foam with highly-efficient flame retardancy and reinforced mechanical property

A phosphorous-containing HEMAP–co–GMA (HPG) prepolymer was successfully prepared by the ring-opening reaction of glycidyl methacrylate (GMA) and 2–hydroxyethyl methacrylate phosphate (HEMAP) as monomers, and flame retardant HEMAP–GMA copolymer (HPG) coating on the surface of rigid polyurethane foam (RPUF) was further fabricated by free-radical thermal-curing. The HPG coating endowed RPUF excellent flame retardancy and fire hazardous safety. The HPG coated on RPUF (HPG/RPUF) reached UL94 V–0 rating, and the limited oxygen index value of the HPG-2/RPUF improved from 19.0 % of RPUF to 27.8 %. The cone calorimetric test results showed that the total heat release and mean peak heat release rate values of the HPG-2/RPUF reduced by 79.6 % and 54.6 % compared to those of RPUF, respectively. The flame–retardant mechanism of HPG/RPUG was speculated the synergistic flame retardant effect between the barrier of the dense char layer and the inhibition of phosphorus–containing free–radicals. The three–dimensional crosslinked HPG coating not only provided HPG/RPUF excellent water resistance, but also enhanced compressive properties and heat–insulation. The highly efficient flame–retardant HPG coating has great potential in fire protection of the heat insulation foams.

Design of a novel D-A-D type furan-based charge transfer organic photoelectric material

Abstract This work describes the synthesis of a novel D-A-D type furan derivative using a [2+2] cycloaddition and ring-opening reaction. Compared to thiophene-based materials, furan derivatives have lower aromaticity and more quinone-like structures, resulting in better π-electron delocalization. The novel D-A-D furan molecule in this paper exhibits a reduced bandgap and enhanced absorption in the near-infrared and visible regions, as well as strong fluorescence and good solubility.

Skeletal Editing of Isatins for Heterocycle Molecular Diversity.

Isatins have been widely used in the preparation of a variety of heterocyclic compounds, where the skeletal editing of isatins has shown significant advantages for the construction of diverse heterocycles. This review highlights the progress made in the last decade (2013-2023) in the skeletal editing of the isatin scaffold. A series of ring expansion reactions for the construction of quinoline skeleton, quinolone skeleton, polycyclic quinazoline skeleton, medium-sized ring skeleton, as well as a series of ring opening reactions for the generation of 2-(azoly)aniline skeleton by the cleavage of C-C bond and C-N bond are highlighted. It is hoped that this review will provide some understanding of the chemical transformations of isatins and contribute to the further realization of its molecular diversity.

Facile preparation of zwitterionic core-shell nanogels for dual-functional coatings: Combining antifouling and antibacterial features in silicon implant model surface modification

To develop surface-coating technology for fabricating functionalized biomedical implant and overcome implant-associated bacterial infections, this study presented an innovative antifouling and antibacterial dual-functional nanogel coating methodology for engineering silicon-based biomedical implants/biochips. Firstly, zwitterionic core-shell PAA@(GMA/SBMA) nanogels were designed and prepared via reflux-precipitation polymerization and were characterized through NMR, FTIR, DLS, AFM and TEM. The nanogels exhibited uniform and spherical morphology, salt-ion responsiveness, and high lysozyme loading capability. Subsequently, the PAA@(GMA/SBMA) nanogels were covalently grafted onto the surface of silicon wafers, via an epoxy-amine ring-opening reaction, to prepare nanogel-coated silicon wafers (Si@nanogels). A comprehensive array of characterization techniques, including SEM-EDS, contact angle measurements, and XPS, validated the effective nanogel-coating. These coatings demonstrated notable resistance to protein adsorption, highlighting their robust antifouling properties. Upon loading with the antibacterial agent lysozyme, the nanogel coating displayed remarkable antibacterial efficacy against both Gram-negative (E. coli) and Grampositive (S. aureus) bacteria and effectively inhibited biofilm formation. Furthermore, the nanogel coatings exhibited good biocompatibility and dynamic stability, thus facilitating the surface-mediated adhesion and growth of fibroblast 3T3 cells. Significantly, this work provided a facile, economic and efficient surface modification approach to fabricate nanogel-coated antifouling/antibacterial dual-functional biomedical implant model towards potential clinical applications.

Origin of Chemoselectivity of Halohydrin Dehalogenase-Catalyzed Epoxide Ring-Opening Reactions.

By performing molecular dynamics (MD), quantum mechanical/molecular mechanical (QM/MM) calculations, and QM cluster calculations, the origin of chemoselectivity of halohydrin dehalogenase (HHDH)-catalyzed ring-opening reactions of epoxide with the nucleophilic reagent NO2- has been explored. Four possible chemoselective pathways were considered, and the computed results indicate that the pathway associated with the nucleophilic attack on the Cα position of epoxide by NO2- is most energetically favorable and has an energy barrier of 12.9 kcal/mol, which is close to 14.1 kcal/mol derived from experimental kinetic data. A hydrogen bonding network formed by residues Ser140, Tyr153, and Arg157 can strengthen the electrophilicity of the active site of the epoxide substrate to affect chemoselectivity. To predict the energy barrier trends of the chemoselective transition states, multiple analyses including distortion analysis and electrophilic Parr function (Pk+) analysis were carried out with or without an enzyme environment. The obtained insights should be valuable for the rational design of enzyme-catalyzed and biomimetic organocatalytic epoxide ring-opening reactions with special chemoselectivity.