Highly Efficient Synthesis and Acaricidal and Insecticidal Activities of Novel Oxazolines with N-Heterocyclic Substituents

Homologous Design and Three-Dimensional Quantitative Structure-Activity Relationship Study of Acaricidal 2,4-Diphenyloxazolines Containing Different Heteroatoms and Alkyl Chains

In order to speculate the three-dimensional structure of the potential binding pocket of the chitin synthase inhibitor, a series of 2,4-diphenyloxazoline derivatives with different lengths of alkyl chains and heteroatoms were designed and synthesized by a homologous strategy. The bioassay results indicate that both the length of the alkyl chains and the type of substituents can affect the acaricidal activity against mite eggs. Compounds containing chloropropyl, alkoxyalkyl, and para-substituted phenoxyalkyl or phenylthioalkyl groups exhibit good activity, while those containing steric hindrance substituents or carbonyl substituents on the benzene ring exhibit reduced activity. Three-dimensional quantitative structure-activity relationship (3D-QSAR) study showed that there may be a narrow hydrophobic region deep in the pocket, and the steric effect plays a more important role than the electrostatic effect. The current work will provide assistance for future molecular design and target binding research.

Synthesis and Insecticidal Activity of Novel Anthranilic Diamide Insecticides Containing Indane and Its Analogs

Diamide insecticides have always been a hot research topic in the field of pesticides. To further discover new compounds with high activity and safety, indane and its analogs were introduced into chlorantraniliprole, and a battery of chlorfenil derivatives, including indane and its analogs, were designed and prepared for biological testing. Their characterization and verification were carried out through nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS). Biological detection showed that all the compounds exhibited good insecticidal activity against Mythimna separata. At 0.8 mg/L, the insecticidal activity of compound 8q against Mythimna separata was 80%, which was slightly better than that of chlorantraniliprole. The results of the structure-activity relationship (SAR) analysis indicated that the indane moiety had a significant effect on insecticidal activity, especially in the R-configuration. The results indicated that chlorantraniliprole derivatives containing indane groups could serve as pilot compounds for the further development of new insecticides.

Morpholine Derivatives in Agrochemical Discovery and Development

Derivatives of morpholine are biologically active organic compounds with special structures discovered in multiple drugs. As a result of the terminal pharmacophore of action and extraordinary activity, they attracted fair attention with regard to pesticide innovation and development. Analysis of brief structure-activity relationships and the summarization of the characteristics of pesticides containing morpholine fragments with efficient activity are key steps in the development of novel pesticides. This review primarily overviews morpholine compounds with insecticidal, fungicidal, herbicidal, antiviral, and plant growth regulation properties to provide educational insight for the creation of new morpholine-containing compounds.

2-Phenylpyridine Derivatives: Synthesis and Insecticidal Activity against Mythimna separata, Aphis craccivora, and Tetranychus cinnabarinus

The increase in the insecticide resistance of pests, such as Mythimna separata, Aphis craccivora Koch, and Tetranychus cinnabarinus, necessitates the development of new heterocyclic compounds with high insecticidal activity. A series of novel 2-phenylpyridine derivatives containing N-phenylbenzamide moieties were designed and synthesised with Suzuki-Miyaura cross-coupling, nucleophilic substitution, and amidation reactions. The reaction conditions in each step are mild, and the product is easy to separate (yield is about 85%). The structures of the compounds were characterised using ¹H and ¹³C NMR spectroscopy and HRMS. Moreover, the insecticidal activity of the compounds was analysed using the leaf dipping method. The compounds 5a, 5d, 5g, 5h, and 5k at 500 mg/L exhibited 100% inhibition against Mythimna separata. Therefore, the 2-phenylpyridine moieties have the potential to lead to the discovery of novel and effective insecticides.

A Facile Synthesis of 2-Oxazolines via Dehydrative Cyclization Promoted by Triflic Acid

2-oxazolines are common moieties in numerous natural products, pharmaceuticals, and functional copolymers. Current methods for synthesizing 2-oxazolines mainly rely on stoichiometric dehydration agents or catalytic dehydration promoted by specific catalysts. These conditions either generate stoichiometric amounts of waste or require forcing azeotropic reflux conditions. As such, a practical and robust method that promotes dehydrative cyclization while generating no byproducts would be attractive to oxazoline production. Herein, we report a triflic acid (TfOH)-promoted dehydrative cyclization of N-(2-hydroxyethyl)amides for synthesizing 2-oxazolines. This reaction tolerates various functional groups and generates water as the only byproduct. This method affords oxazoline with inversion of α-hydroxyl stereochemistry, suggesting that alcohol is activated as a leaving group under these conditions. Furthermore, the one-pot synthesis protocol of 2-oxazolines directly from carboxylic acids and amino alcohols is also provided.

Design, Synthesis, Acaricidal Activities, and Structure-Activity Relationship Studies of Oxazolines Containing Ether Moieties

To develop highly efficient and low cost acaricides, a series of 2,4-diphenyl-1,3-oxazolines containing an ether moiety at the para position of the 4-phenyl group were synthesized from different alcohols and phenols. The bioassay results showed that most of the compounds, especially the short-chain alkyl ethers, exhibited excellent acaricidal activity against both the larvae and the eggs of Tetranychus cinnabarinus. In particular, the n-propyl ether compound Ic possessed much better larvicidal activity (LC₅₀ = 0.0015 mg/L) and ovicidal activity (LC₅₀ = 0.0008 mg/L) than commercial acaricide etoxazole (LC₅₀ = 0.0145 and 0.02 mg/L for larvae and eggs, respectively). In addition, some compounds also exhibited insecticidal activity, especially compound Iw (4-CF₃-phenyl ether) showed higher mortality than etoxazole against Mythimna separata, Helicoverpa armigera, and Pyrausta nubilalis. Considering the high acaricidal activity and relatively low cost, Ic was worthy of further study as an acaricide agent. An alternative synthetic route for the large-scale synthesis of Ic was then studied.

Novel Pyrimidine Derivatives Bearing a 1,3,4-Thiadiazole Skeleton: Design, Synthesis, and Antifungal Activity

In this study, twenty novel pyrimidine derivatives bearing a 1,3,4-thiadiazole skeleton were designed and synthesized. Then their antifungal activity against Botrytis cinereal (B. cinereal), Botryosphaeria dothidea (B. dothidea), and Phomopsis sp. were determined using the poison plate technique. Biological test results showed that compound 6h revealed lower EC₅₀ values (25.9 and 50.8 μg/ml) on Phompsis sp. than those of pyrimethanil (32.1 and 62.8 μg/ml).

Conventional and microwave-assisted synthesis, anticancer evaluation, 99mTc-coupling and In-vivo study of some novel pyrazolone derivatives

New pyrazolone derivatives were successfully synthesized by both microwave-assisted and conventional techniques. Compound 3 (3-(3-Methyl-5-oxo-4,5-dihydro-1H-pyrazol-1-yl)-3-oxopropanehydrazide) displayed remarkable anti-cancer activity (IC₅₀ obtained at 8.71 and 10.63 µM for HCT-116 and MCF-7, respectively. Moreover, biodistribution study using radiolabeling approach revealed a remarked uptake of [^99mTc]Tc-compound 3 complex into tumour induced in mice. The biodistribution showed high accumulation in tumour tissues with T/NT of 6.92 after 60 min post injection. As a result of these promising data, the newly synthesized compounds especially compound 3 affords a potential radio-carrier that could be used as a tumour marker and can be used for cancer therapy after further preclinical studies.

Phosphorus-Based Organocatalysis for the Dehydrative Cyclization of N-(2-Hydroxyethyl)amides into 2-Oxazolines

A metal-free, biomimetic catalytic protocol for the cyclization of N-(2-hydroxyethyl)amides to the corresponding 2-oxazolines (4,5-dihydrooxazoles), promoted by the 1,3,5,2,4,6-triazatriphosphorine (TAP)-derived organocatalyst tris(o-phenylenedioxy)cyclotriphosphazene (TAP-1) has been developed. This approach requires less precatalyst compared to the reported relevant systems, with respect to the phosphorus atom (the maximum turnover number (TON) ∼ 30), and exhibits a broader substrate scope and higher functional-group tolerance, providing the functionalized 2-oxazolines with retention of the configuration at the C(4) stereogenic center of the 2-oxazolines. Widely accessible β-amino alcohols can be used in this approach, and the cyclization of N-(2-hydroxyethyl)amides provides the desired 2-oxazolines in up to 99% yield. The mechanism of the reaction was studied by monitoring the reaction using spectral and analytical methods, whereby an ¹⁸O-labeling experiment furnished valuable insights. The initial step involves a stoichiometric reaction between the substrate and TAP-1, which leads to the in situ generation of the catalyst, a catechol cyclic phosphate, as well as to a pyrocatechol phosphate and two possible active intermediates. The dehydrative cyclization was also successfully conducted on the gram scale.

Synthesis and Antifungal Activity of Pyrimidine Derivatives Containing an Amide Moiety

In this study, 17 novel pyrimidine derivatives containing an amide moiety were synthesized. Then their in vitro antifungal activities against Botryosphaeria dothidea (B. dothidea), Phomopsis sp., and Botrytis cinereal (B. cinereal) were determined. A preliminary biological test showed that compounds 5-bromo-2-fluoro-N-(2-((2-methyl-6-(trifluoromethyl)pyrimidin-4-yl)oxy)phenyl)benzamide (5f) and 5-bromo-2-fluoro-N-(3-((2-methyl-6-(trifluoromethyl)pyrimidin-4-yl)oxy)phenyl)benzamide (5o) exhibited higher antifungal activity against Phomopsis sp., with an inhibition rate of 100% compared to that of Pyrimethanil at 85.1%. In particular, compound 5o exhibited excellent antifungal activity against Phompsis sp., with the EC₅₀ value of 10.5 μg/ml, which was even better than that of Pyrimethanil (32.1 μg/ml). As far as we know, this is the first report on the antifungal activities against B. dothidea, Phomopsis sp., and B. cinereal of this series of pyrimidine derivatives containing an amide moiety.