Addition Reactions Research Articles

Constructing robust and antioxidant polyurethane–lignin coatings with biodegradable properties for grass press paper films

The practical applications of grass plastic mulch films are limited because their residues turn into microplastics and enter the food chain. This study solves this problem by preparing a degradable cellulose–lignin–waterborne polyurethane composite grass paper film. First, waterborne polyurethane prepared using a mild method was composited with lignin via an addition reaction and the formation of hydrogen bonding between the –OH groups of lignin and the –NCO and –OH groups of polyurethane. Finally, the as-prepared polyurethane–lignin composite was applied as a coating on the surface of a paper-based material to prepare a grass paper mulch film. The relationship between lignin content and the molecular weight, thermal stability, mechanical properties, polymer network crosslinking density, antioxidant capability, and light transmittance of the coating was studied, revealing that higher lignin contents considerably improved the barrier and mechanical properties of the coating and grass paper mulching film. In particular, a lignin content of 20 % resulted in a grass paper mulching film with outstanding grass pressing performance and degradability. Therefore, the multifunctional, ecofriendly grass paper mulch film prepared from cellulose–lignin–waterborne polyurethane composite materials provides an innovative approach to solve the pollution problem of traditional grass plastic paper mulch.

A Photochemical Strategy towards Michael Addition Reactions of Cyclopropenes

AbstractThe development of Michael addition reactions to conjugated cyclopropenes is a challenge in organic synthesis due to the fleeting and reactive nature of such strained Michael acceptor systems. Herein, the development of a photochemical approach towards such conjugated cyclopropenes is reported that serves as a strategic entry point to densely functionalized cyclopropanes in a diastereoselective fashion. The process involves the light‐mediated generation of transient cyclopropenyl α,β‐unsaturated esters from vinyl diazo esters, followed by an organic base catalyzed nucleophilic addition of N‐heterocycles to directly access β‐N‐heterocyclic cyclopropanoic esters. With this synergistic approach, various trisubstituted cyclopropanes bearing N‐heteroaryl and N‐heterocyclic rings such as indole, pyrrole, benzimidazole, isatin, pyridinone, and quinolinone were accessed efficiently in good yield and decent to good diastereoselectivities. Further, β‐indolyl cyclopropanoic acids have been synthesized and were successfully evaluated as FABP‐4 inhibitors. Theoretical calculations have been performed to elucidate the mechanism, which was further supported by experimental findings.

Investigating Gene Delivery Efficiency of Poly(β‐amino ester) Derived From Poly(ethylene glycol) Diacrylate

AbstractPoly(β‐amino ester) (PβAE)‐based polymers hold promise for bacterial gene transfer due to their ability to form stable complexes with genetic material and facilitate efficient delivery into bacterial cells. These polymers are easily modified to improve uptake and protect DNA or RNA from degradation, providing a safer, more controlled alternative to traditional methods like chemical transformation or electroporation. In this study, we evaluated the gene transformation efficiency of cationic PβAE polymer, which was synthesized through an aza‐Michael addition reaction between piperazine and poly(ethylene glycol) diacrylate. Competent cells from E. coli strain DH5α were prepared with the optimized method using Ca2+ and Mg2+ ions. Different concentrations of the polymer were mixed with pRSET‐EmGFP before transforming into competent cells through the heat shock method. Transformed cells were checked on medium containing ampicillin, and by using colony PCR, transformation efficiency was calculated. Based on our findings, we observed a successful transformation of the EmGFP gene in case of having the polymer. Furthermore, the PβAE at high concentrations (20–100 ng µL−1) increased transformation efficiency more than twice as compared to the case of no polymer added. In conclusion, PβAE can effectively increase transformation efficiency.

Facile constructed meroterpenoids with novel hexadecahydroacephenanthrylene carbon skeleton using the biotransformation and chemical synthesis method

Bioaspermeroterpenoid A (1), the first meroterpenoid with an unprecedented hexadecahydroacephenanthrylene carbon skeleton, together with two analogues bioaspermeroterpenoids B and C (2 and 3) were co-isolated from the biotransformation extract of aspermeroterpene C by the fungus Penicillium herquei GZU-31-6. On the other hand, bioaspermeroterpenoid Aa (1a) featuring the same hexadecahydroacephenanthrylene carbon skeleton was synthesized from the precursor aspermeroterpene C by the nucleophilic addition reaction in the presence of CH3ONa. Furthermore, bioaspermeroterpenoids A and C showed good inhibitory activities against lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 cells with IC50 values of 26.08 and 7.50 µM, respectively, compared to the positive control (Indomethacin, IC50 24.1 µM). Especially, bioaspermeroterpenoids A and C also significantly suppressed the protein expression of iNOS and COX-2 at the concentration of 12.5 μM.

Active polyvinyl alcohol films with enhanced strength, antioxidant and antibacterial properties by incorporating nanocellulose and tannin

There is an increasing demand of food packaging materials from sustainable bio- polymers. In this study, tannin-cellulose nanocrystal (TCNCs) fillers were first prepared using dialdehyde cellulose nanocrystal (DACNCs) and tannin through the nucleophilic addition reaction, and then added to PVA matrix as reinforcement fillers to fabricate active food packaging films. FT-IR analysis confirmed the successful reaction between PVA and TCNCs. The incorporation of TCNCs imparted high antibacterial, UV blocking and antioxidant capabilities to the composite films, maximumly achieving a 75 % DPPH free radical scavenging rate while blocking all UV rays. The addition of TCNCs resulted in an increase in water contact angle, alongside decreases in swelling ratio and solubility, indicating the enhanced water resistance. The composite films exhibited a 66.7 % decrease in oxygen permeability (OP) compared to the PVA film, with a slight increase observed in water vapor permeability (WVP). The tensile strength increased from 49.65 MPa to 74.17 MPa by adding 15 % of TCNCs due to the chemical crosslinking between PVA and TCNCs. Wrapping cherry tomatoes with these films prolonged the postharvest life compared to using polyethylene (PE) and pure PVA films. Films derived from sustainable biopolymers show great potential for use in fresh produce packaging.

Development of a Detailed Chemical Kinetic Model for 1-Methylnaphthalene

1-Methylnaphthalene is a critical component for constructing fuel surrogates of diesel and aviation kerosene. However, the reaction pathways of 1-methylnaphthalene included in existing detailed chemical kinetic models vary from each other, leading to discrepancies in the simulation of ignition and oxidation processes. In the present study, reaction classes and pathways involved in the combustion of 1-methylnaphthalene were analyzed, and effects of rate constants of reactions related to 1-methylnaphthalene and its significant intermediates on ignition delay times and species concentration profiles were discussed, involving hydrogen abstraction and substitution reactions of 1-methylnaphthalene, oxidation, isomerization, and addition reactions of 1-naphthylmethyl, hydrogen abstraction and oxidation reactions of indene, as well as the oxidation of indenyl and naphthalene. On this basis, a new detailed chemical kinetic model for 1-methylnaphthalene was developed, which includes 1389 species and 7185 reactions. The validation of this mechanism shows that it can predict accurately the available experimental ignition delay times, species concentration profiles, and laminar flame speeds of 1-methylnaphthalene. Finally, reaction paths and sensitivity analysis of ignition delay times were performed using the proposed reaction mechanism, and the result shows that the conversion of 1-methylnaphthalene to 1-naphthaldehyde plays an important role in its ignition.

A facile strategy for in-situ polymerization of P[sbnd]N network coatings for durable flame-retardant cellulose

In this study, a facile method for durable flame-retardant modification of cotton fibers by in situ polymerization of PN macromolecular physical networks is presented. The proposed method employs an in-situ Michael addition reaction to form a durable, cross-linked phosphine oxide network coatings using trivinylphosphine oxide (TVPO) and polyethyleneimine (PEI) for flame retardant finishing within the cotton fibers. The fabrics were treated using dry and steam cross-linking methods, followed by multiple laundering cycles. SEM analysis and surface characterization verified the deposition of phosphine oxide macromolecules on the surface and inside the cellulose fibers. The finished fabrics exhibited significant improvements in flame resistance, as demonstrated VFT and LOI, which could reach up to 32.5 %. Enhanced flame retardancy and durability were further confirmed through TG and CCT, characterized by increasing residue from 7.00 % to 41.33 % and reducing THR from 11.67 MJ/m2 to 0.68 MJ/m2. Moreover, the finishing fabrics had very good wash resistance and can remain flame retardant after 50 wash cycles. Possible decomposition mechanisms of flame-retardant cotton fabrics were explored by analysis of evolved gas during decomposition through TG-FTIR. The results indicated that the proposed flame-retardant system offered an effective, formaldehyde-free solution with excellent performance.

From gem‐Dichlorocyclobutenones to Cyclobutenols: Unveiling a Ruthenium‐Catalyzed Allylic Reduction‐Asymmetric Transfer Hydrogenation Cascade

Cyclobutenones constitute an appealing class of substrates in catalytic asymmetric transformations leading to diversely substituted enantioenriched four‐membered carbocycles, which are eliciting a growing interest in medicinal chemistry. Whilst several synthetically useful enantioselective conjugate addition reactions have been reported, the catalytic enantioselective reduction of the carbonyl group of simple cyclobutenones remains an elusive transformation. Herein, we disclose the discovery of a novel allylic reduction‐asymmetric transfer hydrogenation cascade, catalyzed by a Noyori‐Ikariya ruthenium complex, from readily available gem‐dichlorocyclobutenones, leading to 2‐chlorocyclobutenols with high optical purities, which can be engaged in postfunctionalization reactions enabling access to substituted four‐membered rings.

Catechol-derived Mannich bases: radical regulatory properties, cytotoxicity and interaction with biomolecules

Free radicals are ubiquitous in biological systems, being responsible for pathogenesis of degenerative diseases and participating in vitally important biochemical processes, which are mediated by radical regulatory agents. The effects of the aliphatic amine substituents in the catechol-derived Mannich bases on their antioxidant and pro-oxidant activity were investigated. It has been found that the presence of catechol moiety in the structure of Mannich bases allows them to act as Cu(II) reductants, efficient Fe(II) chelators and potent DPPH radical scavengers. It has been found that the plausible mechanism of the DPPH radical scavenging proceeds via quinone formation, followed by their interaction with ethanol via the Michael addition reaction. In the neutrophil respiratory burst assay, several compounds have demonstrated a weak antioxidant activity at the micromolar level (0.1–10 µM), whereas at the millimolar level (0.1 mМ) a strong pro-oxidant effect has been observed. Additionally, at the highest used concentrations a pronounced cytotoxicity against dermal fibroblasts DF-2 and an immunosuppressive effect against T-lymphocytes have been observed for all the synthesized compounds. It has been demonstrated that the oxidation of catechols in the presence of low-molecular thiols results in the formation of covalent adducts, which provides an insight into their cytotoxicity and detoxification pathways.

Enantioselective regiospecific addition of propargyltrichlorosilane to aldehydes catalyzed by biisoquinoline N,N'-dioxide.

Distilled propargyltrichlorosilane with >99% isomeric purity was prepared for the first time, and its asymmetric catalytic regiospecific addition reaction to aldehydes was developed through a systematic catalyst structure-reactivity and selectivity relationship study. The observed catalyst structure-enantioselectivity relationship of the present allenylation reaction was found exactly opposite to that of the analogous allylation reaction. The method provided eleven α-allenic alcohols in 22-99% yield with 61:39-92:8 enantiomeric ratios. Furthermore, possible mechanisms of propargyl-allenyl isomerization of propargyltrichlorosilane were computationally investigated.

Molecular Oxygen (O2) Artifacts in Tandem Mass Spectra.

Peak annotation plays an important role in mass spectral evaluation of the NIST 2023 tandem mass spectral library. While most fragment ions are formed by neutral losses, there are peaks that represent adduct ions from these fragments. Previously, we have reported two main types of addition reactions in the collision cell, namely addition of H2O and N2. Here we report a different reaction in the collision cell, with addition of O2 leading to a small peak that could only be assigned to a peroxyl radical ion. For example, some protonated iodoaromatics lose an iodine atom to form a radical cation [M+H-I]+•, which reacts with O2 to generate a peroxyl radical ion [M+H-I+O2]+•. Higher concentrations of O2 result in higher peroxyl radical peaks, which become dominant while the precursor ions are consumed, as examined by five compounds under different concentrations of O2. The correlation of the peroxyl radical peak intensities to the concentration of O2 provides a tool to estimate trace amounts of O2 within the instrument. In the NIST 2023 tandem mass spectral library, the peaks for [M+H-X+O2]+· are most abundant in numbers and in intensity for X = NO2 or I, are much less abundant for X = Br, and are rare for X = Cl. Other leaving groups in this library are SO3H, SO2NH2, CSNH2, CO2C6F5, SO2CH3, and COCH3. The O2 addition reaction is also observed with negative ions in this library. While adducts of H2O and N2 often constitute major peaks, the peaks of the peroxyl radicals under standard conditions are mostly very small and may be mistaken for noise, but their correct annotation improves the quality of the spectra and is important when comparing spectra from different instruments or conditions.

Unveiling the kinetic predominance of fluoride electrosorption at S-modified defect-rich interface: Microscale disordered reconstruction induced accessible synergistic platform

Excessive hazardous fluoride (F−) have necessitated the advancement of fluoride removal electrode materials to mitigate their environmental impact. Herein, a sulfur-modified Bi-containing mesoporous synergistic platform encapsulated in a carbon shell (BiMCS-P) that provides an open nanostructured framework and high-density defects is reported. The BiMCS-P electrode removes fluoride by electrical double layer (EDL) capacitance and additional reversible redox reactions. Due to the diminished reliance of sluggish diffusion and the reduction of activation energy barrier after appropriate sulfidation, the fluoride can be further captured, as verified with high removal capacity (60.23 mg g−1 at an initial pH of 7) when processed in a 100 mg L−1F− solution, efficient energy utilization (72.8 %), and good applicability (about 80 % capacity retention at weakly acid solution). The BiMCS-P electrode can reduce the fluoride concentration from 5 mg L−1 and 2.5 mg L−1 to below the existing regulatory standards (1.5 mg L−1). The intrinsic defects optimize the electron distribution in an unsaturated coordination environment. The topological defects created during the disordered crystallographic conversion from Bi to Bi2S3 reduce the energy barrier of faradaic conversion and improves the redox activity. Moreover, the unique mesoporous framework achieves more defluoridation sites on the electrode’s surface and enables rapid ion storage behavior dominated by capacitive-controlled process at the solid–liquid interface. This study demonstrates a new strategy to improve the electrosorption performance, offering a promising advancement of defluoridation, particularly for materials that exhibit purely capacitive or purely Faradaic electrochemical characteristics.

Fabrication of 3D TPU microfiber structures with embedded dye probes for cyanide ion sensing via charge-reversed electro jet writing

An extremely organized sensing system that indicates the prompt indication of the cyanide ion in water was synthesized. The design of the sensing probe comprises the phenothiazine fluorophore system as an electron donor and tetramethyl-3H-indol-1-ium as an electron acceptor unit. A notable color change in daylight and UV light was observed in the probe when it comes in contact with the solution of cyanide ion. The probe interaction with the cyanide ion results in color change from purple to colorless and these changes occurs in the probe with the disconnection in the ICT process. The detection limit (LOD) 1.3 μM (UV–visible method) and 25 nM (Fluorescence method), denotes that the probe preferentially reacts with cyanide, which is less than the tolerable level of 1.9 μM. The probe reacts with cyanide ions via nucleophilic addition reaction mechanism and it is confirmed through the 1H NMR data. Furthermore, the HRMS value also confirms the same. For practical application of the probe a 3D structure composed of TPU microfiber containing probe molecule was fabricated by charge reversed electro jet writing (CREW) method by 3D printer has been efficiently sense cyanide ion. Also, for cyanide ion sensing probe successfully determines real resources, including cyanide containing various water samples. Besides, the developed PBI-encapsulated Polysulfone (PSF) capsule kit effectively sense cyanide ion in water. Moreover, the test strips, was also employed to detect the cyanide ion in presence of competing anions. Therefore, the synthesized probe displays an outstanding sensing ability towards the cyanide ion.

Stereoselective Michael Addition Reaction for Synthesis of Unnatural Amino Acids

Stereoselective Michael Addition Reaction for Synthesis of Unnatural Amino Acids

Construction of a Dual-Mode Sensing Platform for Ultra-fast Detection of Bisulfite in Food and Environmental Systems.

Sulfur dioxide (SO2) is widely used in food processing to extend the shelf life of food. However, excessive intake of SO2 and its derivatives (HSO3- and SO32-) can cause oxidative damage to the body, and result in several diseases. How to construct probes for rapid real-time detection of HSO3- in the field is beneficial to the developmental needs of practical applications, but it is also very challenging. Here we report a dual-mode fluorescent probe Rh-QL for ultrafast detection of HSO3-, which undergoes a specific 1,4-Michael addition reaction with HSO3- to achieve near-infrared fluorescence turn-on. Probe Rh-QL can rapidly (< 5s) respond to HSO3- with a color change from purple to green and a strong fluorescence emission at 725nm. The probe Rh-QL has been used for the detection of HSO3- in real sugar samples and can be prepared as a portable sensing kit for the detection of HSO3- in the environment due to its high efficiency, rapidity and accuracy. In addition, the probe Rh-QL is able to target label Gram-negative bacteria after reacting with HSO3-, which has the potential to identify the type of pathogenic bacteria.

Proposed Importance of HOCO Chemistry: Inefficient Formation of CO2 from CO and OH Reactions on Ice Dust

With the advent of JWST ice observations, dedicated studies on the formation reactions of detected molecules are becoming increasingly important. One of the most interesting molecules in interstellar ice is CO2. Despite its simplicity, the main formation reaction considered, CO + OH → CO2 + H through the energetic HOCO* intermediate on ice dust, is subject to uncertainty because it directly competes with the stabilization of HOCO as a final product, which is formed through energy dissipation of HOCO* to the water ice. When energy dissipation to the surface is effective during the reaction, HOCO can be a dominant product. In this study, we experimentally demonstrate that the major product of the reaction is indeed not CO2, but rather the highly reactive radical HOCO. The HOCO radical can later evolve into CO2 through H-abstraction reactions, but these reactions compete with additional reactions, leading to the formation of carboxylic acids (R-COOH). Our results highlight the importance of HOCO chemistry and encourage further exploration of the chemistry of this radical.

One‐Step Maleimide‐Based Dual Functionalization of Protein N‐Termini

Maleimide derivatives are privileged reagents for chemically modifying proteins through the Michael addition reaction with cysteine due to their selectivity, operational simplicity, and commercial availability. However, since accessible free cysteine is rarely found in natural proteins, it is highly desirable to find alternative targets to enable direct bioconjugation of proteins with maleimides. In this study, we have developed an operationally simple and straightforward method for the N‐terminal modification of proteins without the need for mutagenesis via a copper(II)‐mediated [3+2] cycloaddition reaction with maleimides and 2‐pyridinecarboxaldehyde (2‐PCA) derivatives under non‐denaturing conditions at pH 6 and 37 °C in aqueous media. Our method utilizes commercially available maleimides to attach diverse functionalities to various N‐terminal amino acids. We demonstrate the preparation of a ternary protein complex cross‐linked at the N‐termini and dually modified trastuzumab equipped with monomethyl auristatin E (MMAE), a cytotoxic agent, and a Cy5 fluorophore (MMAE–Cy5–trastuzumab). MMAE–Cy5–trastuzumab retained human epidermal growth factor receptor 2 (HER2) recognition activity and exerted cytotoxicity against HER2‐positive cells. Furthermore, MMAE–Cy5–trastuzumab allowed successful visualization of HER2‐positive cancer cells in mouse tumors. This straightforward method will expand the accessibility of protein conjugates with well‐defined structures in a wide range of research fields.

One-Step Maleimide-Based Dual Functionalization of Protein N-Termini.

Maleimide derivatives are privileged reagents for chemically modifying proteins through the Michael addition reaction with cysteine due to their selectivity, operational simplicity, and commercial availability. However, since accessible free cysteine is rarely found in natural proteins, it is highly desirable to find alternative targets to enable direct bioconjugation of proteins with maleimides. In this study, we have developed an operationally simple and straightforward method for the N-terminal modification of proteins without the need for mutagenesis via a copper(II)-mediated [3+2] cycloaddition reaction with maleimides and 2-pyridinecarboxaldehyde (2-PCA) derivatives under non-denaturing conditions at pH 6 and 37 °C in aqueous media. Our method utilizes commercially available maleimides to attach diverse functionalities to various N-terminal amino acids. We demonstrate the preparation of a ternary protein complex cross-linked at the N-termini and dually modified trastuzumab equipped with monomethyl auristatin E (MMAE), a cytotoxic agent, and a Cy5 fluorophore (MMAE-Cy5-trastuzumab). MMAE-Cy5-trastuzumab retained human epidermal growth factor receptor 2 (HER2) recognition activity and exerted cytotoxicity against HER2-positive cells. Furthermore, MMAE-Cy5-trastuzumab allowed successful visualization of HER2-positive cancer cells in mouse tumors. This straightforward method will expand the accessibility of protein conjugates with well-defined structures in a wide range of research fields.

Strategy for Optimizing Vitamin B12 Production in Pseudomonas putida KT2440 Using Metabolic Modeling.

Background/Objectives: Vitamin B12 is very important for human health, as it is a cofactor for enzymatic activities and plays various roles in human physiology. It is highly valued in the pharmaceutical, food, and additive production industries. Some of the bacteria currently used for the vitamin production are difficult to modify with gene-editing tools and may have slow growth. We propose the use of the bacteria Pseudomonas putida KT2440 for the production of vitamin B12 because it has a robust chassis for genetic modifications. The present wok evaluates P. putida KT2440 as a host for vitamin B12 production and explore potential gene-editing optimization strategies. Methods: We curated and modified a genome-scale metabolic model of Pseudomonas putida KT2440 and evaluated different strategies to optimize vitamin B12 production using the knockin and OptGene algorithms from the COBRA Toolbox. Furthermore, we examined the presence of riboswitches as cis-regulatory elements and calculated theoretical biomass growth yields and vitamin B12 production using a flux balance analysis (FBA). Results: According to the flux balance analysis of P. putida KT2440 under culture conditions, the biomass production values could reach 1.802 gDW-1·h1·L-1, and vitamin B12 production could reach 0.359 µmol·gDW-1·h-1·L-1. The theoretical vitamin B12 synthesis rate calculated using P. putida KT2040 with two additional reactions was 14 times higher than that calculated using the control, Pseudomonas denitrificans, which has been used for the industrial production of this vitamin. Conclusions: We propose that, with the addition of aminopropanol linker genes and the modification of riboswitches, P. putida KT2440 may become a suitable host for the industrial production of vitamin B12.

Simple and rapid determination of 3-monochloropropane-1,2-diol in food contact papers based on polydopamine-polyethyleneimine copolymerization

The aim of this work was to develop a fluorescence method based on the polydopamine-polyethyleneimine (PDA-PEI) copolymerization, which was subsequently applied for the determination of 3-monochloropropane-1,2-diol (3-MCPD) in food contact papers (FCMs). PEI could provide an alkaline environment and then react with dopamine (DA) to produce copolymers by Michael addition and Schiff-base reactions. This copolymer has a strong fluorescence emission at 527 nm. We found that amino groups of DA and PEI could also react with 3-MCPD in an alkaline medium, which improved the morphology and fluorescence intensity of PDA-PEI copolymers. The fluorescence intensity of the polymers was linear but inversely proportional to the concentration of 3-MCPD in the range of 10.0–500.0 μg kg−1 and the detection limit was 2 μg kg−1. The standard addition method was used in FCMs to demonstrate the practical applicability and the spiked recoveries ranged from 99.8 to 110.3 %. Finally, the levels of 3-MCPD in different FCMs (n = 70) were determined by the proposed method. The detection frequencies ranged from 25 % to 100 % and both the highest detection frequency and levels were observed in kitchen papers. More than half of the samples did not comply with the limits recommended by the German Federal Institute for Risk Assessment, suggesting that 3-MCPD released from FCMs is a major route of human exposure.