Latest generation of halogen-containing pesticides

Visible light induced hydroxyfluoroalkylation of quinoxalin-2(1H)-ones with N-trifluoroethoxyphthalimide under catalyst-free conditions

For the first time, we achieved visible light-induced direct C3-hydroxyfluoroalkylation of quinoxalin-2(1H)-ones using N-trifluoroethoxyphthalimide as the trifluoroethanol radical precursor, without the need for a photocatalyst. The metal-free and catalyst-free nature of this method makes it an efficient and environmentally friendly approach for synthesizing C3-hydroxyfluoroalkylated quinoxalin-2(1H)-ones.

New Active Ingredients for Sustainable Modern Chemical Crop Protection in Agriculture

Today, the agrochemical industry faces enormous challenges to ensure the sustainable supply of high-quality food, efficient water use, low environmental impact, and the growing world population. The shortage of agrochemicals due to consumer perception, changing needs of farmers and ever-changing regulatory requirements is higher than the number of active ingredients that are placed on the market. The introduction of halogen atoms into an active ingredient molecule offers the opportunity to optimize its physico-chemical properties such as molecular lipophilicity. As early as 2010, around four-fifths of modern agrochemicals on the market contained halogen atoms. In addition, it becomes clear that modern agrochemicals have increasingly complex molecular structures with one or more stereogenic centers in the molecule. Today, almost half of modern agrochemicals are chiral molecules (herbicides, insecticides/acaricides/nematicides ≪ fungicides) and most of them consist of mixtures such as racemic mixtures of enantiomers, followed by mixtures of diastereomers and mixtures of pure enantiomers. Therefore, it is important that halogen-containing substituents or stereogenic centers are considered in the structural optimization of the active ingredients to ultimately develop sustainable agrochemicals in terms of efficacy, ecotoxicology, ease of use and cost-effectiveness.

Exploring Fluorinase Substrate Tolerance at C-2 of SAM

The fluorinase enzyme (EC 2.5.1.63) utilises fluoride ion and S-adenosyl-L-methionine (SAM) as substrates for conversion to 5'-fluoro-5'-deoxy-adenosine (5'-FDA) and L-methionine (L-Met). The enzyme has a very strict substrate specificity, however it has been shown to tolerate acetylenes and NH2 replacements for H at C-2 of the adenine ring of SAM. This substrate tolerance is explored further here with -NHR, -N3, -OR and -SR substituents attached to C-2. New activities are demonstrated, for example with NH-methyl, NH-propyl,NH-butyl and O-butyl substrates at C-2, however azide and thioethers were not tolerated. Outcomes are supported by in silico analysis, revealing favourable H-bonding interactions involving NH and O substituents at the adenine C-2 position with N278 and the backbone amide of A279 at the active site respectively. The study informs on the selectivity of the fluorinase as a tool for radiolabelling candidate ligands with fluorine-18 for positron emission tomography programmes.

The effects of different halogenated-pyrethroid pesticides on soil microbial community

The application of pesticides increases crop yields but affects the structure and function of the soil microbial community. Halogens are common functional modification groups in chemical compounds, and innovative pesticides have been developed on the basis of these groups. However, the effects of different halogen substituents on soil microorganisms remain unclear. This study investigated the effects of three pyrethroid pesticides (deltamethrin, cypermethrin, and cyfluthrin) on the soil microbiota. Our results revealed that all these pesticides significantly reduced the stability of the bacterial communities and decreased bacterial diversity at high concentrations. Compared with deltamethrin (Br-) and cypermethrin (Cl-), low concentrations (0.5 mg/kg) of cyfluthrin (F-) increased soil bacterial diversity by 23.14 % and increased the potential for nitrogen fixation by 2.00 % and nitrification by 3.39 %, thus making it a relatively eco-friendly option. Our findings provide new insights into the potential ecological effects of halogenated pyrethroid pesticides on soil ecosystems.

Insights into the C-Cl Bond Breaking in Epichlorohydrin Induced by Low Energy (<10 eV) Electrons

Epichlorohydrin is used as an intermediate for the synthesis of polymers and, more particularly, epoxy adhesives. The traditional process involves the cleavage of the carbon-chlorine bond in an alkaline solution. Here, we investigate the breakage of this bond induced by low-energy (<10 eV) electrons. We show the production of the chlorine anion via a resonant process at different energies. The experimental observations are completed by quantum chemistry calculations of the involved molecular orbitals in the formation of the precursor temporary anions, and their decay mechanisms are discussed in terms of the complex potential energy curve crossing network. The gained information may potentially contribute to a strategy of synthesis by other means where low-energy electrons are implicated, i.e., cold plasmas or even scanning tunnelling microscope for which the bond breakage can be controlled by the energy of the colliding electrons.

Mechanistic Investigations of Chiral Lithium Binaphtholate Catalysis for Asymmetric Aldol-Tishchenko Reaction of α-Fluoroarylketones

In this study, we analyzed the asymmetric aldol-Tishchenko reaction of α-fluoroarylketones with aldehydes in the presence of chiral lithium binaphtholate, which was readily prepared from a chiral BINOL derivative and lithium tert-butoxide. This tandem reaction afforded enantiomerically enriched 2-fluoro-1,3-diols with three contiguous stereogenic centers in high yield and with high diastereo- and enantioselectivities. Moreover, mechanistic investigations of the lithium binaphtholate-catalyzed enantioselective aldol-Tishchenko reaction were performed based on the kinetic isotope effect and computational analyses.

Chemical Synthesis, Herbicidal Activity, Crop Safety, and Molecular Basis of ortho-Fluoroalkoxy Substituted Sulfonylureas as Novel Acetohydroxyacid Synthase Inhibitors

In the face of increasing resistance to the currently used commercial herbicides and the lack of success in identifying new herbicide targets, alternative herbicides need to be developed to control unwanted monocotyledon grasses in food crops. Here, a panel of 29 novel sulfonylurea-based compounds with ortho-fluoroalkoxy substitutions at the phenyl ring were designed and synthesized. Pot assays demonstrated that two of these compounds, 6d and 6u, have strong herbicidal activities against Echinochloa crus-galli, Eleusine indica, Alopecurus aequalis, and Alopecurus japonicus Steudel at a dosage of 15 g ha-1. Furthermore, these two compounds exhibited <5% inhibition against wheat at a dosage of 30 g ha-1 under post-emergence conditions. 6u also exhibited <5% inhibition against rice at a dosage of 30 g ha-1 under both post-emergence and pre-emergence conditions. A kinetics study demonstrated that 6d and 6u are potent inhibitors of Arabidopsis thaliana acetohydroxyacid synthase (AHAS; EC 2.2.1.6) with potent Ki values of 18 ± 1.1 and 11.9 ± 4.0 nM, respectively. The crystal structure of 6u in complex with A. thaliana (At)AHAS has also been determined at 2.7 Å resolution. These new compounds represent new alternative herbicide choices to protect wheat or rice from invading grasses.

Diastereodivergent nucleophile-nucleophile alkene chlorofluorination

The selective hetero-dihalogenation of alkenes provides useful building blocks for a broad range of chemical applications. Unlike homo-dihalogenation, selective hetero-dihalogenation reactions, especially fluorohalogenation, are underdeveloped. Current approaches combine an electrophilic halogen source with a nucleophilic halogen source, which necessarily leads to anti-addition, and regioselectivity has only been achieved using highly activated alkenes. Here we describe an alternative, nucleophile-nucleophile approach that adds chloride and fluoride ions over unactivated alkenes in a highly regio-, chemo- and diastereoselective manner. A curious switch in the reaction mechanism was discovered, which triggers a complete reversal of the diastereoselectivity to promote either anti- or syn-addition. The conditions are demonstrated on an array of pharmaceutically relevant compounds, and detailed mechanistic studies reveal the selectivity and the switch between the syn- and anti-diastereomers are based on different active iodanes and which of the two halides adds first.

Design, synthesis, and nematicidal activity of novel 1,2,4-oxadiazole derivatives containing amide fragments

Plant-parasitic nematodes are seriously affecting agricultural production worldwide and there are few highly effective and low-risk nematicides to control nematode diseases. In order to discover new nematicides, a series of 1,2,4-oxadiazole derivatives containing amide fragments have been designed and synthesized with the principle of active substructure splicing. The nematicidal activity of the target compounds was evaluated in vitro and it indicated that compound C3 exhibited the most nematicidal activity against Bursaphelenchus xylophilus, Aphelenchoides besseyi, and Ditylenchus destructor with the LC50 values of 37.2, 36.6, and 43.4 μg/mL, respectively, which were superior to positive agent tioxazafen. The preliminary mechanism results revealed that compound C3 not only inhibited the reproduction of B. xylophilus populations, but also affected the production of ROS and the accumulation of lipofuscin and lipids. Furthermore, compound C3 showed good inhibition of succinate dehydrogenase (SDH) with the IC50 value of 45.5 µmol/L. Molecular docking indicated that compound C3 had excellent binding to amino acids around the SDH active pocket. This work indicated that 1,2,4-oxadiazole derivative containing amide fragment is a promising template for the discovery of new nematicides and compound C3 can be used as a potential nematicide candidate.

Short- and long-term effects of commercial formulations of imidacloprid, spirotetramat, and mixtures of these active ingredients on pupae of Diaeretiella rapae (Hymenoptera: Braconidae) and its progeny

BACKGROUND

Compatibility studies of insecticides and natural enemies usually focus on short-term lethal effects, without considering the long-term sublethal effects (including progeny). Even less-explored are the effects of commercial insecticides formulated with more than one active product. Short- and long-term lethal and sublethal effects were studied for the first time on the progeny of commercial formulations of spirotetramat, imidacloprid and a commercial mixture of these active ingredients on pupae of Diaeretiella rapae (M'ntosh) (Hymenoptera: Braconidae), an endoparasitoid of aphids considered to be a potential biological control agent. Insecticides were exposed topically on aphid mummies in which the parasitoid was in the pupal stage.

RESULTS

Imidacloprid reduced adult emergence by more than 30% and prolonged intra-host development time with respect to control from half the maximum recommended field dose (MFRD). Spirotetramat and commercial mixture only showed significant effects on these endpoints at doses above the MFRD. The tested formulations did not affect adult longevity, sex ratio, and percentage of parasitism in the exposed generation. At low concentrations the active ingredients in the commercial mixture behave synergistically, whereas at medium and high concentrations they behave antagonistically. Considering the 10% lethal dose (LD10), imidacloprid showed the highest hazard coefficient, whereas the commercial mixture was more hazardous when considering the LD50 and LD90. The commercial mixture and imidacloprid induced higher adult emergence and altered the sex ratio in the progeny.

CONCLUSIONS

The following order of toxicity on D. rapae can be established: imidacloprid > commercial mixture > spirotetramat. Joint use of this species with imidacloprid and commercial mixture should be avoided in integrated pest management programs. © 2024 Society of Chemical Industry.

Insecticidal potential and risk assessment of diamide pesticides against Spodoptera frugiperda in maize crops

The effectiveness, tolerance, and safety of pesticides must be established before their scientific or rational. This study evaluates the field control efficacy of broflanilide, tetraniliprole, and chlorantraniliprole in combating Spodoptera frugiperda in maize crops, as well as the resistance of S. frugiperda to these three diamide pesticides after exposure. By assessing field control efficiency, toxicity, effects on development and reproduction, and detoxification enzyme activity of these diamide pesticides on S. frugiperda, highlights broflanilide's significant insecticidal potential. A highly sensitive and efficient method using QuEChERS/HPLCMS/MS was developed to simultaneously detect residues of these three pesticides on maize. Initial concentrations of broflanilide, tetraniliprole, and chlorantraniliprole ranged from 2.13 to 4.02 mg/kg, with their respective half-lives varying between 1.23 and 1.51 days. Following foliar application, by the time of harvest, the terminal residue concentrations of these pesticides were all under 0.01 mg/kg. Chronic dietary intake risk assessments and cumulative chronic dietary exposure for three pesticides indicated that the general population's terminal residue concentration was within acceptable limits. Not only does this research provide valuable insights into field control efficiency, insecticidal effects, resistance, residues, and risk assessment results of broflanilide, tetraniliprole, and chlorantraniliprole on maize, but additionally, it also paves the way for setting suitable Maximum Residue Limits (MRLs) values based on pre-harvest interval values, rational dosage, and application frequency.

Sulfone Electrophiles in Cross-Electrophile Coupling: Nickel-Catalyzed Difluoromethylation of Aryl Bromides

Fluoroalkyl fragments have played a critical role in the design of pharmaceutical and agrochemical molecules in recent years due to the enhanced biological properties of fluorinated molecules compared to their non-fluorinated analogues. Despite the potential advantages conferred by incorporating a difluoromethyl group in organic compounds, industrial adoption of difluoromethylation methods lags behind fluorination and trifluoromethylation. This is due in part to challenges in applying common difluoromethyl sources towards industrial applications. We report here the nickel-catalyzed cross-electrophile coupling of (hetero)aryl bromides with difluoromethyl 2-pyridyl sulfone, a sustainably sourced, crystalline difluoromethylation reagent. The scope of this reaction is demonstrated with 24 examples (67 ± 16% average yield) including a diverse array of heteroaryl bromides and precursors to difluoromethyl-containing preclinical pharmaceuticals. This reaction can be applied to small-scale parallel synthesis and benchtop scale-up under mild conditions. As sulfone reagents are uncommon electrophiles in cross-electrophile coupling, the mechanism of this process was investigated. Studies confirmed the formation of •CF2H instead of difluorocarbene. A series of modified difluoromethyl sulfones revealed that sulfone reactivity does not correlate exclusively with reduction potential and that coordination of cations or nickel to the pyridyl group is essential to reactivity, setting out parameters for matching the reactivity of sulfones in cross-electrophile coupling.

Radical meta-C-H Halogenation of Azines via N-Benzyl Activation Strategy

Regioselective halogenation of six-membered N-heteroarenes is crucial for precise functional derivatization. We present a meta-selective halogenation method for pyridines, quinolines, and isoquinolines via electrophilic halogen radical addition utilizing an N-benzyl activation strategy. This method achieves C3- and C5-dihalogenation in pyridines, C3- and C6-dihalogenation in quinolines, and C3-monohalogenation in isoquinolines. The feasibility and potential applications of this method were validated through scale-up reactions and the bromination of quinoline derivatives with biomolecular fragments.

Reasons why life on Earth rarely makes fluorine-containing compounds and their implications for the search for life beyond Earth

Life on Earth is known to rarely make fluorinated carbon compounds, as compared to other halocarbons. We quantify this rarity, based on our exhaustive natural products database curated from available literature. We build on explanations for the scarcity of fluorine chemistry in life on Earth, namely that the exclusion of the C-F bond stems from the unique physico-chemical properties of fluorine, predominantly its extreme electronegativity and strong hydration shell. We further show that the C-F bond is very hard to synthesize and when it is made by life its potential biological functions can be readily provided by alternative functional groups that are much less costly to incorporate into existing biochemistry. As a result, the overall evolutionary cost-to-benefit balance of incorporation of the C-F bond into the chemical repertoire of life is not favorable. We argue that the limitations of organofluorine chemistry are likely universal in that they do not exclusively apply to specifics of Earth's biochemistry. C-F bonds, therefore, will be rare in life beyond Earth no matter its chemical makeup.

Defluorination of Organofluorine Compounds Using Dehalogenase Enzymes from Delftia acidovorans (D4B)

Organofluorine compounds have been widely used as pharmaceuticals, agricultural pesticides, and water-resistant coatings for decades; however, these compounds are recognized as environmental pollutants. The capability of microorganisms and enzymes to defluorinate organofluorine compounds is both rare and highly desirable to facilitate environmental remediation efforts. Recently, a strain of Delftia acidovorans (D4B) was identified with potential biodegradation activity toward perfluoroalkyl substances (PFAS) and other organofluorine compounds. Genomic analysis found haloacid and fluoroacetate dehalogenases as enzymes associated with Delftia acidovorans. Here, defluorination activity of these enzymes toward different fluorinated substrates was investigated after their recombinant expression and purification from E. coli. Using an electrochemical fluoride probe, 19F NMR, and mass spectrometry to monitor defluorination, we identified two dehalogenases, DeHa2 (a haloacid dehalogenase) and DeHa4 (a fluoroacetate dehalogenase), with activity toward mono- and difluoroacetate. Of the two dehalogenases, DeHa4 demonstrated a low pH optimum compared to DeHa2, which lost catalytic activity under acidic conditions. DeHa2 and DeHa4 are relatively small proteins, operate under aerobic conditions, and remain active for days in the presence of substrates. Significantly, while there have been many reports on dehalogenation of monofluoroacetate by dehalogenases, this study adds to the relatively small list of enzymes reported to carry out enzymatic defluorination of the more recalcitrant disubstituted carbon in an organofluorine compound. Thus, DeHa2 and DeHa4 represent organofluorine dehalogenases that may be used in the future to design and engineer robust defluorination agents for environmental remediation efforts.

Recent developments in fluorine-containing pesticides

To ensure ongoing sustainability, the modern agrochemical industry is faced with enormous challenges. These arise from provision of high-quality food to increasing water use and environmental impact as well as a growing world population. The loss of previous agrochemicals due to consumer perception, changing grower needs and ever-changing regulatory requirements is higher than the number of active ingredients that are being introduced into the crop protection market. Therefore, the development of novel agrochemicals is essential to provide improved efficacy and environmental profiles. In this context, the introduction of fluorine atoms and fluorine-containing motifs into a molecule is an important method to influence its physicochemical properties. These include, for example, small difluoro- and trifluoromethyl, or trifluoromethoxy groups at aryl or heterocyclic aryl moieties but also fragments like 2,2,2-trifluoroethoxycarbonyl, trifluoromethylsulfonyl, trifluoroacetyl, as well as the so far unusal rest like heptafluoro-iso-propyl. This review gives an overview of recent developments of fluorine-containing pesticides launched over the past 7 years and describes a selection of current fluorine-containing development candidates. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Mechanistic and data-driven perspectives on plant uptake of organic pollutants

Establishing reliable predictive models for plant uptake of organic pollutants is crucial for environmental risk assessment and guiding phytoremediation efforts. This study compiled an expanded dataset of plant cuticle-water partition coefficients (Kcw), a useful indicator for plant uptake, for 371 data points of 148 unique compounds and various plant species. Quantum/computational chemistry software and tools were utilized to compute various molecular descriptors, aiming to comprehensively characterize the properties and structures of each compound. Three types of models were developed to predict Kcw: a mechanism-driven pp-LFER model, a data-driven machine learning model, and an integrated mechanism-data-driven model. The mechanism-data-driven GBRT-ppLFER model exhibited superior performance, achieving RMSEtrain = 0.133 and RMSEtest = 0.301 while maintaining interpretability. The Shapley Additive Explanation analysis indicated that pp-LFER parameters, ESPI, FwRadicalmax, ExtFP607, and RDF70s are the key factors influencing plant uptake in the GBRT-ppLFER model. Overall, pp-LFER parameter, ESPI, and ExtFP607 show positive effects, while the remaining factors exhibit negative effects. Partial dependency analysis further indicated that plant uptake is not solely determined by individual factors but rather by the combined interactions of multiple factors. Specifically, compounds with ppLFER parameter >4, ESPI > -25.5, 0.098 < FwRadicalmax <0.132, and 2 < RFD70s < 3, are generally more readily taken up by plants. Besides, the predicted Kcw values from the GBRT-ppLFER model were effectively employed to estimate the plant-water partition coefficients and bioconcentration factors across different plant species and growth media (water, sand, and soil), achieving an outstanding performance with an RMSE of 0.497. This study provides effective tools for assessing plant uptake of organic pollutants and deepens our understanding of plant-environment-compound interactions.

Discovery of Novel Pyridazine Herbicides Targeting Phytoene Desaturase with Scaffold Hopping

Phytoene desaturase (PDS) is a critical functional enzyme in blocking ζ-carotene biosynthesis and is one of the bleaching herbicide targets. At present, norflurazon (NRF) is the only commercial pyridazine herbicide targeting PDS. Therefore, developing new and diverse pyridazine herbicides targeting PDS is urgently required. In this study, diflufenican (BF) was used as the lead compound, and a scaffold-hopping strategy was employed to design and synthesize some pyridazine derivatives based on the action mode of BF and PDS. The preemergence herbicidal activity tests revealed that compound 6-chloro-N-(2,4-difluorophenyl)-3-(3-(trifluoromethyl)phenoxy)pyridazine-4-carboxamide (B1) with 2,4-diF substitution in the benzeneamino ring showed 100% inhibition rates against the roots and stems of Echinochloa crus-galli and Portulaca oleracea at 100 μg/mL, superior to the inhibition rates of BF. Meanwhile, compound B1 demonstrated excellent postemergence herbicidal activity against broadleaf weeds, which was similar to that of BF (inhibition rate of 100%) but superior to that of NRF. This indicated that 6-Cl in the pyridazine ring is the key group for postemergence herbicidal activity. In addition, compound B1 could induce downregulation of PDS gene expression, 15-cis-phytoene accumulation, and Y(II) deficiency and prevent photosynthesis. Therefore, B1 can be considered as a promising candidate for developing high-efficiency PDS inhibitors.

Molecular Insights into Converting Hydroxide Adenosyltransferase into Halogenase

Halogenation plays a unique role in the design of agrochemicals. Enzymatic halogenation reactions have attracted great attention due to their excellent specificity and mild reaction conditions. S-adenosyl-l-methionine (SAM)-dependent halogenases mediate the nucleophilic attack of halide ions (X-) to SAM to produce 5'-XDA. However, only 11 SAM-dependent fluorinases and 3 chlorinases have been reported, highlighting the desire for additional halogenases. SAM-dependent hydroxide adenosyltransferase (HATase) has a similar reaction mechanism as halogenases but uses water as a substrate instead of halide ions. Here, we explored a HATase from the thermophile Thermotoga maritima MSB8 and transformed it into a halogenase. We identified a key dyad W8L/V71T for the halogenation reaction. We also obtained the best performing mutants for each halogenation reaction: M1, M2 and M4 for Cl-, Br- and I-, respectively. The M4 mutant retained the thermostability of HATase in the iodination reaction at 80 °C, which surpasses the natural halogenase SalL. QM/MM revealed that these mutants bind halide ions with more suitable angles for nucleophilic attack of C5' of SAM, thus conferring halogenation capabilities. Our work achieved the halide ion specificity of halogenases and generated thermostable halogenases for the first time, which provides new opportunities to expand the halogenase repertoire from hydroxylase.

Tri-enzyme fusion of tryptophan halogenase achieves a concise strategy for coenzyme self-sufficiency and the continuous halogenation of L-tryptophan

The halogenase-based catalysis is one of the most environmentally friendly methods for the synthesis of halogenated products, among which flavin-dependent halogenases (FDHs) have attracted great interest as one of the most promising biocatalysts due to the remarkable site-selectivity and wide substrate range. However, the complexity of constructing the NAD+-NADH-FAD-FADH2 bicoenzyme cycle system has affected the engineering applications of FDHs. In this work, a coenzyme self-sufficient tri-enzyme fusion was constructed and successfully applied to the continuous halogenation of L-tryptophan. SpFDH was firstly identified derived from Streptomyces pratensis, a highly selective halogenase capable of generating 6-chloro-tryptophan from tryptophan. Then, using gene fusion technology, SpFDH was fused with glucose dehydrogenase (GDH) and flavin reductase (FR) to form a tri-enzyme fusion, which increased the yield by 1.46-fold and making the coenzymes self-sufficient. For more efficient halogenation of L-tryptophan, a continuous halogenation bioprocess of L-tryptophan was developed by immobilizing the tri-enzyme fusion and attaching it to a continuous catalytic device, which resulted in a reaction yield of 97.6% after 12 h reaction. An FDH from S. pratensis was successfully applied in the halogenation and our study provides a concise strategy for the preparation of halogenated tryptophan mediated by multienzyme cascade catalysis.

An artificial nickel chlorinase based on the biotin-streptavidin technology

Herein, we report on an artificial nickel chlorinase (ANCase) resulting from anchoring a biotinylated nickel-based cofactor within streptavidin (Sav). The resulting ANCase was efficient for the chlorination of diverse C(sp3)-H bonds. Guided by the X-ray analysis of the ANCase, the activity of the artificial chlorinase could be significantly improved. This approach opens interesting perspectives for late-stage functionalization of organic intermediates as it complements biocatalytic chlorination strategies.

Design, Synthesis, and Herbicidal Activity of Substituted 3-(Pyridin-2-yl)Phenylamino Derivatives

To discover protoporphyrinogen oxidase (PPO) inhibitors with robust herbicidal activity and crop safety, three types of substituted 3-(pyridin-2-yl)phenylamino derivatives bearing amide, urea, or thiourea as side chain were designed via structure splicing strategy. Postemergence herbicidal activity assessment of 33 newly prepared compounds revealed that many of our compounds such as 6a, 7b, and 8d exhibited superior herbicidal activities against broadleaf and monocotyledon weeds to commercial acifluorfen. In particular, compound 8d exhibited excellent herbicidal activities and high crop safety at a dosage range of 37.5-150 g ai/ha. PPO inhibitory studies supported our compounds as typical PPO inhibitors. Molecular docking studies revealed that compound 8d provided effective interactions with Nicotiana tabacum PPO (NtPPO) via diverse interaction models, such as π-π stacking and hydrogen bonds. Molecular dynamics (MD) simulation studies and degradation studies were also conducted to gain insight into the inhibitory mechanism. Our study indicates that compound 8d may be a candidate molecule for the development of novel herbicides.

Design, Synthesis, Nematicidal Activity, and Mechanism of Novel Amide Derivatives Containing an 1,2,4-Oxadiazole Moiety

To discover new nematicides, a series of novel amide derivatives containing 1,2,4-oxadiazole were designed and synthesized. Several compounds showed excellent nematicidal activity. The LC50 values of compounds A7, A18, and A20-A22 against pine wood nematode (Bursaphelenchus xylophilus), rice stem nematode (Aphelenchoides besseyi), and sweet potato stem nematode (Ditylenchus destructor) were 1.39-3.09 mg/L, which were significantly better than the control nematicide tioxazafen (106, 49.0, and 75.0 mg/L, respectively). Compound A7 had an outstanding inhibitory effect on nematode feeding, reproductive ability, and egg hatching. Compound A7 effectively promoted the oxidative stress of nematodes and caused intestinal damage to nematodes. Compound A7 significantly inhibited the activity of succinate dehydrogenase (SDH) in nematodes, leading to blockage of electron transfer in the respiratory chain and thereby hindering the synthesis of adenosine triphosphate (ATP), which consequently affects the entire oxidative phosphorylation process to finally cause nematode death. Therefore, compound A7 can be used as a potential SDH inhibitor in nematicide applications.

Applications of Bioisosteres in the Design of Biologically Active Compounds

The design of bioisosteres represents a creative and productive approach to improve a molecule, including by enhancing potency, addressing pharmacokinetic challenges, reducing off-target liabilities, and productively modulating physicochemical properties. Bioisosterism is a principle exploited in the design of bioactive compounds of interest to both medicinal and agricultural chemists, and in this review, we provide a synopsis of applications where this kind of molecular editing has proved to be advantageous in molecule optimization. The examples selected for discussion focus on bioisosteres of carboxylic acids, applications of fluorine and fluorinated motifs in compound design, some applications of the sulfoximine functionality, the design of bioisosteres of drug-H2O complexes, and the design of bioisosteres of the phenyl ring.

Genome-Wide Expression Analysis Unravels Fluoroalkane Metabolism in Pseudomonas sp. Strain 273

Pseudomonas sp. strain 273 grows with medium-chain terminally fluorinated alkanes under oxic conditions, releases fluoride, and synthesizes long-chain fluorofatty acids. To shed light on the genes involved in fluoroalkane metabolism, genome, and transcriptome sequencing of strain 273 grown with 1,10-difluorodecane (DFD), decane, and acetate were performed. Strain 273 harbors three genes encoding putative alkane monooxygenases (AlkB), key enzymes for initiating alkane degradation. Transcripts of alkB-2 were significantly more abundant in both decane- and DFD-grown cells compared to acetate-grown cells, suggesting AlkB-2 catalyzes the attack on terminal CH3 and CH2F groups. Coordinately expressed with alkB-2 was an adjacent gene encoding a fused ferredoxin-ferredoxin reductase (Fd-Fdr). Phylogenetic analysis distinguished AlkB that couples with fused Fd-Fdr reductases from AlkB with alternate architectures. A gene cluster containing an (S)-2-haloacid dehalogenase (had) gene was up-regulated in cells grown with DFD, suggesting a possible role in the removal of the ω-fluorine. Genes involved in long-chain fatty acid biosynthesis were not differentially expressed during growth with acetate, decane, or DFD, suggesting the bacterium's biosynthetic machinery does not discriminate against monofluoro-fatty acid intermediates. The analysis sheds first light on genes and catalysts involved in the microbial metabolism of fluoroalkanes.

Synthesis of Alkylated Polyfluorobenzenes through Decarboxylative Giese Addition of Aliphatic N-Hydroxyphthalimide Esters with Polyfluorostyrene

Polyfluoroaromatic compounds play crucial roles in medicinal and material science. However, the synthesis of alkylated polyfluoroarenes has been relatively underdeveloped. In this study, we devised a novel decarboxylative coupling reaction between aliphatic N-hydroxyphthalimide esters and polyfluorostyrene, leveraging the photochemical activity of electron donor-acceptor (EDA) complexes. This method offers simple reaction conditions, a broad substrate scope, and excellent functional group tolerance. Furthermore, we have demonstrated the practicality of this protocol through late-stage polyfluoroaryl modification of biologically active molecules using readily available carboxylic acids as starting materials, thus providing an important supplement to the current toolbox for accessing alkylated polyfluoroaryl motifs.

Design, synthesis and antifungal evaluation of novel nopol derivatives as potent laccase inhibitors

BACKGROUND

To explore further potential natural product-based antifungal agents, a series of novel nopol-based carboxamide and hydrazide derivatives containing a natural pinene structure were designed, synthesized, and evaluated for their inhibitory activities against seven phytopathogenic fungi and oomycetes.

RESULTS

The bioassay results indicated that some compounds exhibited good inhibitory activities against Gibberella zeae, Sclerotinia sclerotiorum, and Phytophthora capsici. Among them, compound 3h displayed excellent in vitro activities against G. zeae, with EC₅₀ values of 1.09 mg L^-1 , which was comparable with the commercial fungicides bixafen and carbendazim (median effective concentration [EC₅₀ ] = 1.21 and 0.89 mg L^-1 , respectively). Notably, in vivo bioassay results suggested that compound 3h also showed prominent protective and curative effects (95.6% and 94.2%) at 200 mg L^-1 against G. zeae. The scanning electron microscopy study indicated that compound 3h could destroy the morphological integrity of G. zeae hyphae. The in vitro enzyme inhibitory bioassay revealed that compound 3h exhibited potent inhibitory activity against laccase with median inhibitory concentration (IC₅₀ ) values of 4.93 μm, superior to positive control cysteine (IC₅₀  = 35.50 μm), and its binding modes with laccase were elucidated by molecular docking study. In addition, the fluorescent imaging of the dansylamide-labeled derivatives 8 on wheat leaf epidermal cells and the hyphae of G. zeae revealed that this class of hydrazide derivatives could readily permeate into wheat leaves and reached the laccase target in fungal cells.

CONCLUSION

Some nopol-based hydrazide derivatives exhibited excellent anti-G. zeae activity and laccase inhibitory activity, which merits further development as a new fungicide candidate for controlling Fusarium head blight. © 2023 Society of Chemical Industry.

Hydrolytic Behavior of Novel Pesticide Broflanilide and Its Dissipative Properties in Different Types of Soils

All pesticides are toxic by nature and pose short- or long-term safety risks to human or the environment, especially when they were used extensively and absence of safety measures. As a new insecticidal active compound with a novel mechanism of action, there is a serious inadequate of information on the hydrolytic behavior of broflanilide in the aqueous environment, as well as its degradation pattern in agricultural soils. In particular, the effects of temperature and pH of the aqueous environment on its hydrolytic behaviors and the dissipation pattern in different types of agricultural soils were still in a dark box. And the further understanding and insights into this insecticidal active ingredient were being deeply conditioned by these doubts. The hydrolysis behavior of broflanilide and the dissipation pattern in soil were systematically investigated by constructing hydrolysis systems with different temperatures and pH values, and conducting spiking experiments in different types of agricultural soil in the laboratory. The obtained results showed that the longest hydrolysis half-life of 10 mg/L broflanilide at 25 °C was 43.32 h (in pH 4.0 buffer), while it was only 12.84 h in pH 9.0 buffer. In pH 7.0 buffer, the hydrolysis rate of broflanilide exhibited a significant temperature dependence, as shown by the fact that for every 10 °C increase in the system temperature, the corresponding hydrolysis rate will increase about 1.5 times. The dissipation experiments in soils showed that broflanilide was most rapidly dissipated in fluvo-aquic soil (half-life of 1.94 days), followed by lime concretion black soil (half-life of 2.53 days) and cinnamon soil (half-life of 3.11 days), and slower in paddy soil (half-life of 4.03 days). It was indicated that broflanilide was a readily degradable pesticide in both aqueous environment and agricultural soil, and it was significantly affected by the temperature and pH of the system.

A straightforward access to trifluoromethylated natural products through late-stage functionalization

Covering: 2011 to 2021Trifluoromethyl (CF3)-modified natural products have attracted increasing interest due to their magical effect in binding affinity and/or drug metabolism and pharmacokinetic properties. However, the chemo and regioselective construction of natural products (NPs) bearing a CF3 group still remains a long-standing challenge due to the complex chemical scaffolds and diverse reactive sites of NPs. In recent years, the development of late-stage functionalization strategies, including metal catalysis, organocatalysis, light-driven reactions, and electrochemical synthesis, has paved the way for direct trifluoromethylation process. In this review, we summarize the applications of these strategies in the late-stage trifluoromethylation of natural products in the past ten years with particular emphasis on the reaction model of each method. We also discuss the challenges, limitations, and future prospects of this approach.

Impact analysis of different applications of cyantraniliprole on control of horse chestnut leaf miner (Cameraria ohridella) larvae supported by biophoton emission

Cameraria ohridella is one of the most invasive pests of horse chestnut. Cyantraniliprole is one of the most perspectively active insecticides, which can transport within the plant in several ways, and its efficacy against this pest has not yet been tested. All three modes of application were effective against the target pest, but there was a difference in the time of action between them. However, no demonstrable difference in the speed of action was detected between the doses used. A more intense rate of acropetal translocation was confirmed compared to basipetal translocation. A trend-like effect between the applied concentration of cyantraniliprole and the photon emission intensity per unit area of plant tissue was observed in the translaminar and acropetal treatment settings. In both cases, a clear increase in photon emission was observed, indicating metabolic upregulation. Therefore, we can conclude that biophoton emission measurements can be utilized to conduct efficient pesticide translocation investigations.

Synthesis, Structural Determination, and Antifungal Activity of Novel Fluorinated Quinoline Analogs

A series of new fluorinated quinoline analogs were synthesized using Tebufloquin as the lead compound, 2-fluoroaniline, ethyl 2-methylacetoacetate, and substituted benzoic acid as raw materials. Their structures were confirmed by ¹H NMR, ¹³C NMR, and HRMS. The compound 8-fluoro-2,3-dimethylquinolin-4-yl 4-(tert-butyl)benzoate (2b) was further determined by X-ray single-crystal diffraction. The antifungal activity was tested at 50 μg/mL, and the bioassay results showed that these quinoline derivatives had good antifungal activity. Among them, compounds 2b, 2e, 2f, 2k, and 2n exhibited good activity (>80%) against S. sclerotiorum, and compound 2g displayed good activity (80.8%) against R. solani.

Toxicity assessment of two IGR insecticides on eggs and larvae of the ladybird Eriopis connexa

BACKGROUND

Eriopis connexa is an important predator in the Neotropical region, associated with pests of economic relevance on horticultural crops in Argentina. The use of broad-spectrum insecticides could reduce the biodiversity of these natural enemies in agroecosystems and put at risk its conservation. New, selective "risk reduced" insecticides could be an alternative to conventional chemical control to promote sustainable agriculture. The goal of this work was to assess the lethal and sublethal effects of two insect growth regulator (IGR) insecticides on eggs and two larval instars of E. connexa exposed to insecticides.

RESULTS

Pyriproxyfen and cypermethrin significantly affected egg hatching by 28.8% and 70.4%, respectively. Pyriproxyfen reduced the survival of larvae that emerged by ≈52% from Day (D3)3 after hatching and caused the lengthening of developmental time for both larval and pupal stages. By contrast, teflubenzuron did not reduce hatching and survival but shortened the developmental time of the pupae stage. Cypermethrin reduced the survival of 2nd (L2 ) and 4th (L4 ) larval instars by 36.4% and 74.6%, respectively, and lengthened the development time of L2 . Pyriproxyfen lengthened the development time of L4 and reduced the fecundity and fertility of females. Teflubenzuron reduced survival of L2 and L4 larval instars by 46.9% and 28.6%, respectively, and lengthened the total development time for the larval stage. In addition, teflubenzuron reduced the fecundity and fertility of females.

CONCLUSIONS

Both eggs and larvae were susceptible to exposure to IGR, showing lethal and sublethal effects. This study highlights, once again, the higher toxicity of cypermethrin to E. connexa. The toxicity of both IGR insecticides could impair the performance of E. connexa as a biological control agent in agroecosystems. © 2022 Society of Chemical Industry.

Discovery of 1,2,4-Oxadiazole Derivatives Containing Haloalkyl as Potential Acetylcholine Receptor Nematicides

Plant-parasitic nematodes pose a serious threat to crops and cause substantial financial losses due to control difficulties. Tioxazafen (3-phenyl-5-thiophen-2-yl-1,2,4-oxadiazole) is a novel broad-spectrum nematicide developed by the Monsanto Company, which shows good prevention effects on many kinds of nematodes. To discover compounds with high nematocidal activities, 48 derivatives of 1,2,4-oxadiazole were obtained by introducing haloalkyl at the 5-position of tioxazafen, and their nematocidal activities were systematically evaluated. The bioassays revealed that most of 1,2,4-oxadiazole derivatives showed remarkable nematocidal activities against Bursaphelenchus xylophilus, Aphelenchoides besseyi, and Ditylenchus dipsaci. Notably, compound A1 showed excellent nematocidal activity against B. xylophilus with LC50 values of 2.4 μg/mL, which was superior to that of avermectin (335.5 μg/mL), tioxazafen (>300 μg/mL), and fosthiazate (436.9 μg/mL). The transcriptome and enzyme activity results indicate that the nematocidal activity of compound A1 was mainly related to the compound which affected the acetylcholine receptor of B. xylophilus.

Theoretical investigation on the elusive structure-activity relationship of bioinspired high-valence nickel-halogen complexes in oxidative fluorination reactions

Very recently, bioinspired high-valence metal-halogen complexes have been proven to be competent oxidants in the C-H bond activation and heteroatom dihalogenation reactions. However, the structure-activity relationship of such active species and the reaction mechanisms of oxidations mediated by these oxidants are still elusive. In this study, density functional theory (DFT) calculations were performed to systematically study the oxidizing ability of the high-valence Ni^III-X (X = F and Cl) complexes Et₄N[Ni^III(Cl/F)(L)], (1_Cl/F, Et = ethyl, L = N,N'-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamide), such as the reaction mechanism of fluorination of 1,4-cyclohexadiene (CHD) by 1_F in the presence of AgF and the reaction mechanism of difluorination of triphenyl phosphine (PPh₃) by 1_F. All calculated results fit well with the experiments and present new mechanistic findings. The C-H bond activation by the high-valence nickel(III)-halogen complexes was found to proceed via a hydrogen-atom transfer (HAT) mechanism by analysis of the molecular orbitals of the transition states. C-H bond activation by 1_F takes a Ni-F-H angle of ca. 180°, whereas that by 1_Cl takes an angle of ca. 120° on the transition states. These results indicate that the exchange-enhanced reactivity is responsible for the dramatic oxidative difference between these two oxidants. The role of AgF in C-H fluorination of CHD by 1_F is proposed to act as a Lewis acid adduct, AgF-binding Ni(III)-fluorine complex 1_F-Ag-F, which acts both as an oxidant in C-H bond activation and as a fluorine donor in the fluorination step. A cooperative oxidation mechanism involving two 1_F oxidants was proposed for the difluorination of PPh₃ by 1_F. These theoretical findings will enrich the knowledge of high-valence metal-halogen chemistry and play a positive role in the rational design of new catalysts.

Amide-Ligand-Promoted Silver-Catalyzed C-H Fluorination via Radical/Polar Crossover

We describe an efficient method for benzylic C-H fluorination via sequential hydrogen-atom transfer (HAT) and oxidative radical-polar crossover utilizing the Ag(I)/Selectfluor system. Amide ligands, such as benzamide and sulfonamide, substantially facilitate the processes leading to a carbocation intermediate, which subsequently reacts with nucleophilic fluorinating reagent to form a C-F bond. This protocol is applicable to the fluorination of all 1°, 2°, and 3° C-H bonds as well as to late-stage C-H fluorination of bioactive molecules.

Adamantyl-ureas with pyrazoles substituted by fluoroalkanes as soluble epoxide hydrolase inhibitors

A series of soluble epoxide hydrolase (sEH) inhibitors containing halogenated pyrazoles was developed. Inhibition potency of the obtained compounds ranges from 0.8 to 27.5 nM. 1-Adamantyl-3-[(4,5-dichloro-1-methyl-1Н-pyrazol-3-yl)methyl]urea (3f, IC50 = 0.8 nM) and 1-[(Adamantan-1-yl)methyl]-3-[(4,5-dichloro-1-methyl-1Н-pyrazol-3-yl)methyl]urea (4f, IC50 = 1.2 nM) were found to be the most potent sEH inhibitors within the described series.

Visible-light-induced selective defluoroalkylations of polyfluoroarenes with alcohols

To provide α-polyfluoroarylalcohols, a novel protocol for the selective defluoroalkylation of polyfluoroarenes with easily accessible alcohols was reported via the cooperation of photoredox and hydrogen atom transfer (HAT) strategies with the assistance of Lewis acids under visible light irradiation. The protocol featured broad scope, excellent regioselectivity for both C-H and C-F bond cleavages, and mild conditions. Mechanistic studies suggested that the reaction occurred through Lewis acid-promoted HAT to provide an alkyl radical and sequential addition to polyfluoroarenes. Impressively, the regioselectivity for C-F cleavage was verified with the Fukui function. The feasibility and application of this protocol on fluoroarene synthesis were well illustrated by gram-scale synthesis under both batch and flow conditions, late-stage decoration of bioactive compounds, and further transformations of the fluoroarylalcohols.

Catalytic and Chemodivergent Synthesis of 1-Substituted 9H-Pyrrolo[1,2-a]indoles via Annulation of β-CF3 Enones with 3-Substituted Indoles

Chemodivergent reactions are more advantageous in organic synthesis that yield diversely functionalized scaffolds from common starting materials. Herein, we report an efficient metal-free chemodivergent protocol for the synthesis of 1-substituted 9H-pyrrolo[1,2-a]indole derivatives in the presence of catalytic amounts of Lewis acid/Brønsted acid conditions using 3-substituted indoles and β-trifluoromethyl-α,β-unsaturated ketones. Fine-tuning of the catalyst and solvent system in the reaction conditions deliver the trifluoromethyl, trifluoroethylcarboxylate, or carboxylic acid substituents on the C1-position of 9H-pyrrolo[1,2-a]indole derivatives in situ. It is postulated that the solvent and LA/BA catalyst interaction was found to be crucial for the catalytic C-F activation in these transformations.

4'-Fluoro-nucleosides and nucleotides: from nucleocidin to an emerging class of therapeutics

The history and development of 4'-fluoro-nucleosides is discussed in this review. This is a class of nucleosides which have their origin in the discovery of the rare fluorine containing natural product nucleocidin. Nucleocidin contains a fluorine atom located at the 4'-position of its ribose ring. From its early isolation as an unexpected natural product, to its total synthesis and bioactivity assessment, nucleocidin has played a role in inspiring the exploration of 4'-fluoro-nucleosides as a privileged motif for nucleoside-based therapeutics.

Discovery of quinazoline compound as a novel nematicidal scaffold

With the aim of discovering novel nematicidal scaffolds, the nematicidal activities of a series of quinazoline compounds were tested, with some compounds showing excellent results. Among them, the LC₅₀ values of compound K11 against Bursaphelenchus xylophilus, Aphelenchoides besseyi, and Ditylenchus destructor were 7.33, 6.09, and 10.95 mg/L, respectively. In addition, the nematicidal activity of compound K11 against Meloidogyne incognita was 98.77% at 100 mg/L. Compound K11 not only increased the production of reactive oxygen species and the accumulation of lipofuscin and lipids in nematodes, but it also attenuated nematode pathogenicity by reducing the nematodes' antioxidant capacity. Transcriptomic analysis showed that compound K11 had significant effects on fatty acid degradation, metabolic pathways, and the differentially expressed genes related to redox processes in nematodes. Furthermore, the expression levels of the corresponding differentially expressed genes were verified using real-time quantitative polymerase chain reaction. Quinazoline can be used as a new nematicidal scaffold, and it is expected that more work will be done on the discovery of novel nematicides based on the lead compound K11 in the future.

Synthesis and Reactions of 3-Halogenated 2-CF3-Indoles

Halogenation of 2-trifluoromethylindole afforded 3-chloro-, 3-bromo- and 3-iodo derivatives in up to 98% yield. Methyl-, benzyl- and tosyl-groups can be installed at the nitrogen atom of prepared indoles in high yields by base catalyzed reaction with the corresponding alkylating (sulfonylating) reagents. A high synthetic utility of the prepared haloindoles in the reaction with various nucleophilies was shown. The reaction with 4-methylthiophenol and copper cyanide afforded the corresponding sulfides and nitriles in high yield. Palladium catalyzed cross-coupling with phenyl boronic acid and phenylacetylene gave the corresponding 3-phenyl-2-CF₃-indoles and acetylenic derivatives in 72-98% yield.

Combining target analysis with sum parameters-a comprehensive approach to determine sediment contamination with PFAS and further fluorinated substances

Recent studies aiming at a fluorine mass balance analysis in sediments combined the determination of extractable organic fluorine (EOF) with target analysis. They reported high fractions of unidentified organic fluorine (UOF) compounds, as the target analysis covers only a limited number of per- and polyfluoroalkyl substances (PFAS). For this reason, in this study, a comprehensive approach was used combining target analysis with an extended PFAS spectrum, the EOF and a modified total oxidisable precursor (TOP) assay, which includes trifluoroacetic acid, to determine the PFAS contamination in sediments (n=41) and suspended solids (n=1) from water bodies in Northern Germany (Lower Saxony). PFAS are ubiquitous in the sediments (detected in 83% of the samples). Perfluorinated carboxylic acids (PFCAs) were found in 64% of the samples; perfluorinated sulfonic acids (PFSAs) were detected less frequently (21%), with the highest concentration observed for perfluorooctanesulfonic acid (PFOS). Levels of precursors and substitutes were lower. Applying the TOP assay resulted in an increase in PFCAs in 43% of the samples analysed. In most cases, target analysis and the TOP assay could not account for the EOF concentrations measured. However, as the fraction of UOF decreased significantly, the application of the TOP assay in fluorine mass balance analysis proved to be an important tool in characterising the PFAS contamination of riverine sediments.

Acid-Switchable Synthesis of Trifluoromethylated Triazoles and Isoxazoles via Reaction of CF3-Ynones with NaN3: DFT Study of the Reaction Mechanism

A detailed study of the reaction of CF₃-ynones with NaN₃ was performed. It was found that the reaction permits the selective synthesis of either 4-trifluoroacetyltriazoles or 5-CF₃-isoxazoles. The chemoselectivity of the reaction was switchable via acid catalysis. The reaction of CF₃-ynones with NaN₃ in EtOH produced high yields of 4-trifluoroacetyltriazoles. In contrast, the formation of 5-CF₃-isoxazoles was observed under catalysis by acids. This acid-switchable procedure can be performed at sub-gram scale. The possible reaction mechanism was supported by DFT calculations. The synthetic utility of the prepared 4-trifluoroacetyltriazoles was demonstrated.

Non-fumigant Nematicides are Promising Alternatives to Fumigants for the Management of Meloidogyne enterolobii in Tobacco

Experiments were conducted to evaluate the efficacy of three currently available non-fumigant chemical nematicides (oxamyl, fluopyram, and fluensulfone) and a biological nematicide derived from Burkholderia against Meloidogyne enterolobii on tobacco in a growth room environment. The non-fumigant chemical nematicides greatly suppressed nematode egg production compared to the untreated control, the suppression being 99.9% for fluensulfone and oxamyl, and 93% for fluopyram. Similarly, oxamyl-, fluensulfone-, and fluopyram-treated pots, respectively, had 99%, 98%, and 94% less J2/100 cm3 of soil than those in the control. The biological nematicide did not have a significant effect on nematode egg production and the soil abundance of J2. The root biomass of tobacco was significantly reduced by the application of fluensulfone, while the effects of oxamyl, fluopyram, and Burkholderia metabolites were not significant compared to the untreated control. Results from this study suggest that non-fumigant nematicides have a potential to serve as an alternative to fumigant nematicides.

A super-hydrophobic perfluoropolyether coated polytetrafluoroethylene sheets substrate for detection of acetamiprid surface-enhanced Raman spectroscopy

In this paper, a hydrophobic substrate as concentrators including an inner layer of polytetrafluoroethylene (PTFE) and an outer layer covered a thin layer of perfluoropolyether (PFPE) was constructed to achieve a higher sensitivity for acetamiprid (AC) SERS detection. The condensation effect of the PTFE-PFPE hydrophobic substrate-induced aggregation of gold nanoparticles (Au NPs) result ''hot spots'' for SERS. The hydrophobic substrate is better reproducibility (RSD < 5%) compared with that on a conventional silicon wafer. A further application of the hydrophobic substrate was demonstrated by the detection of AC in tea samples within a detection range of 0.03 mg/L to 3 mg/L. The hydrophobic substrate eliminates the problem of solution diffusion to avoid the "coffee ring" effect (When a droplet adheres to a solid surface, the suspended molecular particles usually deposit on the edge of the droplet to form a ring).

Synthesis and insecticidal activities of 4-(propargyloxy) benzenesulfonamide derivatives

A series of 4-(propargyloxy) benzenesulfonamide derivatives with different substituents on the benzene ring were synthesized and evaluated for their insecticidal activity. Some of the compounds showed good insecticidal activity against Mythimna separata, and the LC₅₀ value of the most active compound B2.5 was 0.235 mg/ml. Ultrastructural changes in the midgut epithelial cells of Mythimna separata were observed using transmission electron microscopy, and severe structural damage was found in microvilli, mitochondria and rough endoplasmic reticulum. It indicates that the possible site of action of these benzenesulfonamides is the cytoplasmic membrane and endomembrane system of the midgut epithelial cells. The above provides a basis for the development of novel insecticidal active compounds with a novel mechanism of action.

Applications of Isosteres of Piperazine in the Design of Biologically Active Compounds: Part 2

Applications of piperazine and homopiperazine in drug design are well-established, and these heterocycles have found use as both scaffolding and terminal elements and also as a means of introducing a water-solubilizing element into a molecule. In the accompanying review (10.1021/acs.jafc.2c00726), we summarized applications of piperazine and homopiperazine and their fused ring homologues in bioactive compound design along with illustrations of the use of 4-substituted piperidines and a sulfoximine-based mimetic. In this review, we discuss applications of pyrrolidine- and fused-pyrrolidine-based mimetics of piperazine and homopiperazine and illustrate derivatives of azetidine that include stretched and spirocyclic motifs, along with applications of a series of diaminocycloalkanes.

Transition-Metal-Free, Site-Selective C-F Arylation of Polyfluoroarenes via Electrophotocatalysis

Direct C_Ar-F arylation is effective and sustainable for synthesis of polyfluorobiaryls with different degrees of fluorination, which are important motifs in medical and material chemistry. However, with no aid of transition metals, the engagement of C_Ar-F bond activation has proved difficult. Herein, an unprecedented transition-metal-free strategy is reported for site-selective C_Ar-F arylation of polyfluoroarenes with simple (het)arenes. By merging N,N-bis(2,6-diisopropylphenyl)perylene-3,4,9,10-bis(dicarboximide)-catalyzed electrophotocatalytic reduction and anodic nitroxyl radical oxidation in an electrophotocatalytic cell, various polyfluoroaromatics (2F-6F and 8F), especially inactive partially fluorinated aromatics, undergo sacrificial-reagents-free C-F bond arylation with high regioselectivity, and the yields are comparable to those for reported transition-metal catalysis. This atom- and step-economic protocol features a paired electrocatalysis with organic mediators in both cathodic and anodic processes. The broad substrate scope and good functional-group compatibility highlight the merits of this operationally simple strategy. Moreover, the easy gram-scale synthesis and late-stage functionalization collectively advocate for the practical value, which would promote the vigorous development of fluorine chemistry.

Spectroscopic characterization of a Ru(III)-OCl intermediate: a structural mimic of haloperoxidase enzymes

Haloperoxidase enzymes utilize metal hypohalite species to halogenate aliphatic and aromatic C-H bonds to C-X (X = Cl, Br, I) in nature. In this work, we report the synthesis and spectroscopic characterization of a unique Ru^III-OCl species as a structural mimic of haloperoxidase enzymes. The reaction of [(BnTPEN)Ru^II(NCCH₃)]²⁺ (BnTPEN = N¹-benzyl-N¹,N²,N²-tris(pyridine-2-ylmethyl)ethane-1,2-diamine) with hypochlorite in the presence of an acid in CH₃CN : H₂O mixtures generated a novel [(BnTPEN)Ru^III-OCl]²⁺ species that persists for 4.5 h at room temperature. This new species was characterized by UV-vis absorption, EPR, and resonance Raman spectroscopic techniques, and ESI-MS. The Ru^III-OCl species is capable of performing oxygen atom transfer and hydrogen atom abstraction to various organic substrates.