Design, synthesis, and biological activities of novel 2-cyanoacrylates containing oxazole, oxadiazole, or quinoline moieties

Design, Synthesis, and Nematicidal Activity of Novel Amide Derivatives Containing an 1,2,4/1,3,4-Oxadiazole Moiety against Bursaphelenchus xylophilus

To discover novel structural nematicides, 79 amide compounds containing 1,2,4/1,3,4-oxadiazole moiety were designed, synthesized, and evaluated for nematicidal efficacy against second-stage juveniles of Bursaphelenchus xylophilus (B. xylophilus). Notably, some compounds exhibited superior nematicidal efficacy, for example, the LC50 values of compounds 11, 39, 40, 48, 49, 51, 52, and 54 were 7.4, 31.0, 35.3, 10.3, 12.7, 6.9, 21.5, and 52.2 mg/L, respectively, with nematicidal activities significantly surpassing that of tioxazafen (79.3 mg/L). Compound 51 exhibited multifaceted nematicidal activity through suppression of motility, feeding, and reproduction, combined with induction of oxidative stress. Compound 51 significantly reduced nematode protein content and impaired antioxidant capacity. Meanwhile, compound 51 demonstrates superior binding energy and interaction mode with succinate dehydrogenase (SDH), showing potent SDH inhibition (IC50 = 15.0 μmol/L). Therefore, compound 51, which may become a potential SDH inhibitor, interferes with nematode energy metabolism by inhibiting SDH activity, resulting in nematode death.

Heterocyclic core modifications in trypanosomacidal 2-[(phenylheteroaryl)ethyl]ureas

The protozoan parasites Trypanosoma brucei and Trypanosoma cruzi, which cause human African trypanosomiasis (HAT) and Chagas disease, respectively, are responsible for considerable human suffering. Reduced case numbers and improved treatment options for HAT provide hope, but the outlook for Chagas disease is less promising, and safer, more efficacious chemotherapy is sorely needed. We previously reported the discovery and optimisation of a novel class of potent and selective trypanosomacidal 2-[(2-phenylthiazolyl)ethyl]ureas active against both T. brucei brucei and T. cruzi. In the current work, replacement of the core thiazole with alternative heterocycles has revealed that a contiguous arrangement of phenyl substituent, hydrogen-bond-accepting nitrogen, and alkyl linker are required to maintain activity. Compared to the parent thiazole, increased polarity of the core heterocycle in triazoles, tetrazoles and pyrimidines, leads to a drop in potency against T. b. brucei. A 2,6-disubsituted pyridine is tolerated but in general, 5-membered heterocycles are preferred. Analogues with oxazole, pyrazole and isomeric ('reverse') pyrazole cores displayed comparable T. b. brucei potency and selectivity to the parent thiazole, and in some cases improved lipophilic ligand efficiencies and metabolic stability. These compounds possessing more polar core heterocycles were generally 2-4 times less potent against T. cruzi (compared to T. b. brucei). This study demonstrates robust structure-activity relationships across a variety of heterocyclic scaffolds, providing many options for further optimisation of this class of compounds.

Structural Variety in Transition Metal Complexes of Tripodal Ligands Containing Mixed Quinolyl and Pyridyl Donors

The syntheses of the tripodal tetraamine ligands 2-(pyridin-2-yl)-N,N-bis(quinolin-2-ylmethyl)ethan-1-amine (DQPEA), N-(pyridin-2-ylmethyl)-2-(quinolin-2-yl)-N-(2-(quinolin-2-yl)ethyl)ethan-1-amine (DQEPMA), 2-(pyridin-2-yl)-N,N-bis(2-(quinolin-2-yl)ethyl)ethan-1-amine (DQEPEA), N,N-bis(pyridin-2-ylmethyl)-2-(quinolin-2-yl)ethan-1-amine (QEDPMA), and 2-(pyridin-2-yl)-N-(2-(pyridin-2-yl)ethyl)-N-(2-(quinolin-2-yl)ethyl)ethan-1-amine (QEDPEA) containing mixed quinolyl and pyridyl moieties are reported, with 2-vinylquinoline being used to attach quinolylethyl arms to the aliphatic N atom. X-ray crystal structures of [(Mn(DQPEA))2O2](ClO4)2 ⋅ (CH3CN)2, [Cu(DQPEA)NCCH3](ClO4)2, [Zn(DQPEA)NCCH3](ClO4)2, [Pd(DQEPEA)Cl]Cl ⋅ 11H2O are detailed, with four, five, and six-coordination observed. In addition, the dimeric complex [(DPEA)Co(μ-OH)3Co(DPEA)](ClO4)3 ⋅ 0.5H2O ⋅ MeCN containing the tridentate DPEA ligand formed by N-dealkylation of QEDPEA is reported. Calculations suggest that the very short Co…Co distance of 2.5946(6) Å in this complex is unlikely to be due to a Co-Co bond.

Regiodivergent Synthesis of 4- and 5-Sulfenyl Oxazoles from Alkynyl Thioethers

The regiodivergent synthesis of 4- and 5-sulfenyl oxazoles from 1,4,2-dioxazoles and alkynyl thioethers has been achieved. Gold-catalysed conditions are used to favour the formation of 5-sulfenyl oxazoles via β-selective attack of the nitrenoid relative to the sulfenyl group. In contrast, 4-sulfenyl oxazoles are formed by α-selective reaction under Brønsted acid conditions from the same substrates. The nature of stabilising gold-sulfur interactions have been investigated by natural bond orbital analysis, showing that the S→Au interactions are significantly stronger in the intermediate that favours the 5-sulfenyl oxazoles. A kinetic survey identifies catalyst inhibition processes. This study into the regiodivergent methods includes the development of telescoped annulation-oxidation protocols for regioselective access to oxazole sulfoxides and sulfones.

Quinoline Derivatives in Discovery and Development of Pesticides

Finding highly active molecular scaffold structures is always the key research content of new pesticide discovery. In the research and development of new pesticides, the discovery of new agricultural molecular scaffold structures and new targets still faces great challenges. In recent years, quinoline derivatives have developed rapidly in the discovery of new agriculturally active molecules, especially in the discovery of fungicides. The unique quinoline scaffold has many advantages in the discovery of new pesticides and can provide innovative and feasible solutions for the discovery of new pesticides. Therefore, we reviewed the use of quinoline derivatives and their analogues as molecular scaffolds in the discovery of new pesticides since 2000. We systematically summarized the agricultural biological activity of quinoline compounds and discussed the structure-activity relationship (SAR), physiological and biochemical properties, and mechanism of action of the active compounds, hoping to provide ideas and inspiration for the discovery of new pesticides.

Pyrimido[4,5-b]indole derivatives bearing 1,2,4-oxadiazole moiety as MDM2 inhibitor candidates in cancer treatment

Aim: In this study, novel hybrid structures of pyrimido-indole-oxadiazole were developed as MDM2 inhibitors for restoring the regular function of the p53. Materials & methods: A multistep chemical pathway was used to synthesize the derivatives. Nutlin-3a was used as a standard lead in molecular docking and molecular dynamics simulations. Finally, cytotoxicity was evaluated against MCF-7 cancer cells versus Doxorubicin. Results: The most promising candidate was 12c, which had an NO₂ group in the para position of the oxadiazole ring (IC₅₀: 1.1 μM). A satisfactory result was obtained with the combined application of 12c and Doxorubicin (IC₅₀ decreased to 0.63 μM), which could be potentially attributed to MDM2 inhibition. Conclusion: These hybrid structures can be further investigated as potential MDM2 inhibitors.

Gold-catalyzed synthesis of oxazoles from alkynyl triazenes and dioxazoles

A gold-catalyzed regioselective [3 + 2] cycloaddition of alkynyl triazenes with 1,2,4-dioxazoles was developed.

Recent Advances in the Pesticide Activities of 2-Cyanoacrylate Derivatives

2-Cyanoacrylates are a unique class of compounds with high photosystem II electron transport inhibitory activity. Through the in-depth study of molecular design, synthesis, biological activity, structure-activity relationship, and action mechanism, a large number of 2-cyanoacrylate derivatives with excellent herbicidal activity were found. In addition, 2-cyanoacrylate derivatives with different substituents have also been found to have good fungicidal or anti-plant virus activities. To further guide the design and development of new pesticide candidates, the representative research work of 2-cyanoacrylate derivatives with herbicidal, fungicidal, and anti-plant virus activities was reviewed.

Synthesis of imidazo[1,5-a]pyridines via cyclocondensation of 2-(aminomethyl)pyridines with electrophilically activated nitroalkanes

Imidazo[1,5-a]pyridines were efficiently prepared via the cyclization of 2-picolylamines with nitroalkanes electrophilically activated in the presence of phosphorous acid in polyphosphoric acid (PPA) medium.

New Potential Biologically Active Compounds: Synthesis and Characterization of Urea and Thiourea Derivativpes Bearing 1,2,4-oxadiazole Ring

Background:

Urea, thiourea, and 1,2,4-oxadiazole compounds are of great interest due to their different activities such as anti-inflammatory, antiviral, analgesic, fungicidal, herbicidal, diuretic, antihelminthic and antitumor along with antimicrobial activities.

Objective:

In this work, we provide a new series of potential biologically active compounds containing both 1,2,4-oxadiazole and urea/thiouprea moiety.

Materials and Methods:

Firstly, 5-chloromethyl-3-aryl-1,2,4-oxadiazoles (3a-j) were synthesized from the reaction of different substituted amidoximes (2a-j) and chloroacetyl chloride in the presence of pyridine by conventional and microwave-assisted methods. In the conventional method, 1,2,4-oxadiazoles were obtained in two steps. O-acylamidoximes obtained in the first step at room temperature were heated in toluene for an average of one hour to obtain 1,2,4-oxadiazoles. The yields varied from 70 to 96 %. 1,2,4-oxadiazoles were obtained under microwave irradiation in a single step in a 90-98 % yield at 160 °C in five minutes. 5-aminomethyl-3-aryl-1,2,4- oxadiazoles (5a-j) were obtained by Gabriel amine synthesis in two steps from corresponding 5-chloromethyl-3- aryl-1,2,4-oxadiazoles. Finally, twenty new urea (6a-j) and thiourea (7a-j) compounds bearing oxadiazole ring were synthesized by reacting 5-aminomethyl-3-aryl-1,2,4-oxadiazoles with phenyl isocyanate and isothiocyanate in tetrahydrofuran (THF) at room temperature with average yields (40-70%).

Results and Discussions:

An efficient and rapid method for the synthesis of 1,2,4-oxadiazoles from the reaction of amidoximes and acyl halides without using any coupling reagent under microwave irradiation has been developed, and twenty new urea/thiourea compounds bearing 1,2,4-oxadiazole ring have been synthesized and characterized.

Conclusion:

We have synthesized a new series of urea/thiourea derivatives bearing 1,2,4-oxadiazole ring. Also facile synthesis of 3,5-disubstituted 1,2,4-oxadiazoles from amidoximes and acyl chlorides under microwave irradiation was reported. The compounds were characterized using FTIR, 1H NMR, 13C NMR, and elemental analysis techniques.

BF3·OEt2-TFAA Mediated Tetra-Functionalization of Amino Acids - Synthesis of Di- and Tri-Substituted 2-Trifluoromethyl Oxazoles in One Pot

A highly efficient, TFAA-BF₃·OEt₂ mediated multicomponent coupling of amino acid, TFAA, and aromatics provides a broad library of 2-trifluoromethyl equipped 2,5-disubstituted/2,4,5-trisubstituted oxazoles or N-(trifluoroacetyl)-β-aminoalkyl ketones. This amino acid tetra-functionalization approach involves amidation (C-N), anhydride (C-O), Friedel-Crafts acylation (C-C), and Robinson-Gabriel annulation (C-O) followed by dehydrative aromatization. This reaction takes place under operationally simple, mild, and metal-free conditions using readily available amino acids and aromatic compounds.

Syntheses and Biological Activities of triazole-based Sulfonamides

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The triazole and sulfonamide compounds are known as biologically active agents that were employed for medicinal applications. These compounds were obtained in different forms by a variety of techniques to vast ranges of applications. The broad biological properties of these compounds have encouraged researchers to design and synthesize triazole-based sulfonamide derivatives as compounds with potential biological activity. In this review, we summarized the synthetic procedures of triazole-based sulfonamide compounds together with their biological activities during the last two decades.

Migratory Aptitudes in Rearrangements of Destabilized Vinyl Cations

The Lewis acid-promoted generation of destabilized vinyl cations from β-hydroxy diazo ketones leads to an energetically favorable 1,2-shift across the alkene followed by an irreversible C-H insertion to give cyclopentenone products. This reaction sequence overcomes typical challenges of counter-ion trapping and rearrangement reversibility of vinyl cations and has been used to study the migratory aptitudes of nonequivalent substituents in an uncommon C(sp²) to C(sp) vinyl cation rearrangement. The migratory aptitude trends were consistent with those observed in other cationic rearrangements; the substituent that can best stabilize a cation more readily migrates. However, density functional theory calculations show that the situation is more complex. Selectivity in the formation of one conformational isomer of the vinyl cation and facial selective migration across the alkene due to an electrostatic interaction between the vinyl cation and the adjacent carbonyl oxygen work in concert to determine which group migrates. This study provides valuable insight into predicting migration preferences when applying this methodology to the synthesis of structurally complex cyclopentenones that are differentially substituted at the α and β positions.

Alkynyl Thioethers in Gold-Catalyzed Annulations To Form Oxazoles

Non-oxidative, regioselective, and convergent access to densely functionalized oxazoles is realized in a functional-group tolerant manner using alkynyl thioethers. Sulfur-terminated alkynes provide access to reactivity previously requiring strong donor-substituted alkynes such as ynamides. Sulfur does not act in an analogous donor fashion in this gold-catalyzed reaction, thus leading to complementary regioselective outcomes and addressing the limitations of using ynamides.

Transition-metal-free synthesis of oxazoles: valuable structural fragments in drug discovery

This review article encapsulates the recent developments in the metal-free approaches used to construct oxazole moiety.

Synthesis and Herbicidal Activity of Triketone-Quinoline Hybrids as Novel 4-Hydroxyphenylpyruvate Dioxygenase Inhibitors

4-Hydroxyphenylpyruvate dioxygenase (EC 1.13.11.27, HPPD) is one of the most important targets for herbicide discovery. In the search for new HPPD inhibitors with novel scaffolds, triketone-quinoline hybrids were designed and subsequently optimized on the basis of the structure-activity relationship (SAR) studies. Most of the synthesized compounds displayed potent inhibition of Arabidopsis thaliana HPPD (AtHPPD), and some of them exhibited broad-spectrum and promising herbicidal activity at the rate of 150 g ai/ha by postemergence application. Most promisingly, compound III-l, 3-hydroxy-2-(2-methoxy-7-(methylthio)quinoline-3-carbonyl)cyclohex-2-enone (Ki = 0.009 μM, AtHPPD), had broader spectrum of weed control than mesotrione. Furthermore, compound III-l was much safer to maize at the rate of 150 g ai/ha than mesotrione, demonstrating its great potential as herbicide for weed control in maize fields. Therefore, triketone-quinoline hybrids may serve as new lead structures for novel herbicide discovery.

Iodine catalysed intramolecular C(sp3)–H functionalization: synthesis of 2,5-disubstituted oxazoles from N-arylethylamides

Iodine catalyzed synthesis of 2,5-substituted oxazoles from N-arylethylamides through intramolecular C(sp³)–H functionalization under metal-free conditions is described.

Highly regioselective synthesis of 2,4,5-(hetero)aryl substituted oxazoles by intermolecular [3+2]-cycloaddition of unsymmetrical internal alkynes

A robust N-nucleophilic 1,3-N,O-dipole equivalent reacts with unsymmetrical internal alkynes under gold catalysis. Conjugation from a remote nitrogen lone pair enables and controls this convergent and highly regioselective process.

Room temperature copper(II)-catalyzed oxidative cyclization of enamides to 2,5-disubstituted oxazoles via vinylic C-H functionalization

A copper(II)-catalyzed oxidative cyclization of enamides to oxazoles via vinylic C-H bond functionalization at room temperature is described. Various 2,5-disubstituted oxazoles bearing aryl, vinyl, alkyl, and heteroaryl substituents could be synthesized in moderate to high yields. This reaction protocol is complementary to our previously reported iodine-mediated cyclization of enamides to afford 2,4,5-trisubstituted oxazoles.

Synthesis and anti-protozoal activity of novel dihydropyrrolo[3,4-d][1,2,3]triazoles

1,2,4-Oxadiazole and 1,2,3-triazole containing heterocyclic compounds continue to gain interest in synthesis of chemical entities and exhibit various biological activities as anti-protozoal and anti-cancer agents. By using the principle of bioisosterism, a series of novel oxadiazolyl pyrrolo triazole diones; namely, (3aS,6aR)-1-((3-(4-substituted phenyl)-1,2,4-oxadiazol-5-yl)methyl)-5-phenyl-1,6a-dihydropyrrolo[3,4-d][1,2,3] triazole-4,6(3aH,5H)-diones (5a-k) was designed and synthesized by the 1,3-dipolar cycloaddition reaction of novel 5-azidomethyl 3-aryl substituted 1,2,4-oxadiazoles (4a-k) with N-phenyl maleimide. The structures of all the cycloadducts were elucidated by means of spectroscopic methods and physical characteristics. The in vitro anti-protozoal and cytotoxic activities of these novel heterocyclic compounds were investigated.

Design, synthesis, and biological activities of arylmethylamine substituted chlorotriazine and methylthiotriazine compounds

Heterocyclic rings were introduced into the core structure of s-triazine to design and synthesize a series of novel triazines containing arylmethylamino moieties. These compounds were characterized by using spectroscopic methods and elemental analysis. Their herbicidal, insecticidal, fungicidal, and antitumor activities were evaluated. Most of these compounds exhibited good herbicidal activity, especially against the dicotyledonous weeds, and compound F8 was almost at the same level as the control compound atrazine. Their structure-activity relationships were discussed. At the same time, some triazines had interesting fungicidal and insecticidal activities, of which F4 exhibited 100% efficacy against Puccinia triticina even at 20 ppm, and F5 showed Lepidopteran-specific activity in both leaf-piece and artificial diet assays. Moreover, these compounds showed antitumor activities against leukemia HL-60 cell line and lung adenocarcinoma A-549 cell line.

Design, synthesis, and herbicidal activities of novel 2-cyanoacrylates containing isoxazole moieties

A series of novel 2-cyanoacrylates containing an isoxazole moiety were designed and synthesized. Their structures were characterized by (1)H NMR and elemental analysis (or high-resolution mass spectrometry). Their herbicidal activities against four species were evaluated, and the results indicated that some of the title compounds showed excellent herbicidal activities against rape and amaranth pigweed in postemergence treatment even at a dose of 75 g/ha.