Design, synthesis and structure–activity relationship of novel diphenylamine derivatives

Design, Synthesis, and Fungicidal Activities of Novel N-(Pyrazol-5-yl)benzamide Derivatives Containing a Diphenylamine Moiety

To accelerate the development of novel fungicides, a variety of N-(pyrazol-5-yl)benzamide derivatives with a diphenylamine moiety were designed and synthesized using a pharmacophore recombination strategy based on the structure of pyrazol-5-yl-aminophenyl-benzamides. The bioassay results demonstrated that most of the target compounds had excellent in vitro antifungal activities against Sclerotinia sclerotiorum, Valsa mali, and Botrytis cinerea. In particular, compound 5IIIh exhibited remarkable activity against S. sclerotiorum (EC50 = 0.37 mg/L), which was similar to that of fluxapyroxad (EC50 = 0.27 mg/L). In addition, compound 5IIIc (EC50 = 1.32 mg/L) was observed to be more effective against V. mali than fluxapyroxad (EC50 = 12.8 mg/L) and comparable to trifloxystrobin (EC50 = 1.62 mg/L). Furthermore, compound 5IIIh demonstrated remarkable in vivo protective antifungal properties against S. sclerotiorum, with an inhibition rate of 96.8% at 100 mg/L, which was close to that of fluxapyroxad (99.6%). Compounds 5IIIc (66.7%) and 5IIIh (62.9%) exhibited good in vivo antifungal effects against V. mali at 100 mg/L, which were superior to that of fluxapyroxad (11.1%) but lower than that of trifloxystrobin (88.9%). The succinate dehydrogenase (SDH) enzymatic inhibition assay was conducted to confirm the mechanism of action. Molecular docking analysis further revealed that compound 5IIIh has significant hydrogen-bonding, π-π, and p-π conjugation interactions with ARG 43, SER 39, TRP 173, and TYR 58 in the binding site of SDH, and the binding mode was similar to that of the commercial fungicide fluxapyroxad. All of the results suggest that compound 5IIIh could be a potential SDH inhibitor, offering a valuable reference for future studies.

Design, synthesis and herbicidal evaluation of novel uracil derivatives containing an isoxazoline moiety

BACKGROUND

Glyphosate is the most widely used and successful herbicide discovered to date, but its utility is now threatened by the occurrence of several glyphosate-resistant weed species. Saflufenacil is a relatively new herbicide developed by BASF in 2010. It is a highly effective selective herbicide showing excellent control on broadleaf weeds (more than 90 species), significantly superior to other protoporphyrinogen oxidase (PPO) inhibitor herbicides at the level of weeds controlled. It is also effective against glyphosate-resistant Conyza canadensis if used in combination with glyphosate. A series of novel uracil-based PPO inhibitors containing an isoxazoline moiety were designed via the intermediate derivatization method, synthesized using a key saflufenacil raw material as starting material and evaluated for herbicidal activity.

RESULTS

The target compounds were characterized by ¹ H NMR and high-resolution electrospray mass spectra. Bioassays indicated that some title compounds can control efficiently and effectively both broadleaf weeds and grassy weeds at low doses, especially the glyphosate-resistant weeds C. canadensis and Eleusine indica.

CONCLUSION

This work provides a basis for further studies of 9b for control of a wider range of weeds, particularly for glyphosate-resistant weeds.

Design, Synthesis, Crystal Structure, and Fungicidal Activity of Two Fenclorim Derivatives

Two fenclorim derivatives (compounds 6 and 7) were synthesized by linking active sub-structures using fenclorim as the lead compound. The chemical structures of the two compounds were confirmed by NMR spectroscopy, high resolution mass spectrometry, and X-ray diffraction analysis. Their fungicidal activity against six plant fungal strains was tested. Compounds 6 and 7 both crystallized in the monoclinic system, with a P21/c space group (a = 8.4842(6) Å, b = 24.457(2) Å, c = 8.9940(6) Å, V = 1855.0(2) Å3, Z = 4) and Cc space group (a = 10.2347(7) Å, b = 18.3224(10) Å, c = 7.2447(4) Å, V = 1357.50(14) Å3, Z = 4), respectively. The crystal structure of compound 6 was stabilized by C–H···N and C–H···O hydrogen bonding interactions and N–H···N hydrogen bonds linked the neighboring molecules of compound 7 to form a three-dimensional framework. Compound 6 displayed the most excellent activity, which is much better than that of pyrimethanil against Botrytis cinerea in vivo. Additionally, compound 6 exhibited greater in vitro activity against Pseudoperonospora cubensis compared to that of pyrimethanil. Moreover, compound 7 exhibited strong fungicidal activity against Erysiphe cichoracearum at 50 mg/L in vitro, while pyrimethanil did not. Compounds 6 and 7 could be used as new pyrimidine fungicides in the future.

Design, Synthesis, and Structure-Activity Relationship of Novel Spiropyrimidinamines as Fungicides against Pseudoperonospora cubensis

Harmful fungus and the developed resistance to available fungicides seriously threaten the yield and quality of crops; thus, the search for new, highly efficient, and resistance-overcoming fungicides remains a quite urgent goal of agricultural scientists. In this study, a series of novel spiropyrimidinamine derivatives were designed and synthesized by employing the intermediate derivatization method (IDM). Their structures were identified by ¹H NMR, elemental analyses, and MS spectra. The structure of compound 5 was further confirmed by X-ray diffraction. Bioassays indicated that a number of the title compounds exhibited some fungicidal activities against Pseudoperonospora cubensis. Especially, compound 5 displayed excellent activity (EC₅₀ = 0.422 mg/L), significantly higher than those of the commercialized fungicides cyazofamid, flumorph, and diflumetorim. The structure-activity relationship was also discussed. It was concluded that compound 5 with super fungicidal potency and a novel structure is a promising agrochemical fungicide candidate for further development.

Design, Synthesis, and Structure-Activity Relationship of New Arylpyrazole Pyrimidine Ether Derivatives as Fungicides

To explore a novel fungicide effectively against cucumber downy mildew (CDM), a series of new arylpyrazole containing pyrimidine ether derivatives were designed and synthesized by employing the intermediate derivatization method (IDM). The structures of synthesized compounds were identified by ¹H NMR, ¹³C NMR, elemental analyses, MS, and X-ray diffraction. Bioassays demonstrated that some of the title compounds exhibited excellent fungicidal activities against CDM. Especially, compound 7 (EC₅₀ = 1.22 mg/L) displayed significantly higher bioactivity than that of commercial fungicides diflumetorim and flumorph and nearly equal effect to that of cyazofamid. The relationship between the structure and fungicidal activity of the synthesized compounds was discussed as well. The study showed that compound 7 was a promising fungicide candidate for further development.

Synthesis of blue-red emissive amido-substituted di(het)aryl and tri(het)aryl amine derivatives via chemoselective N-mono and N,N-diarylation of (het) aryl amino amides using benzyne/arynes

Chemoselective synthesis of amide-substituted triaryl and diaryl amines by N-mono and N,N-diarylation of (het)aryl amino amides using arynes has been reported. Selected triarylamines showed blue-red emission.

Molecular topology and QSAR multi-target analysis to boost the in silico research for fungicides in agricultural chemistry

The aim of the present study is to show how molecular topology can be a powerful in silico tool for the prediction of the fungicidal activity of several diphenylamine derivatives against three fungal species (cucumber downy mildew, rice blast and cucumber gray mold). A multi-target QSAR model was developed, and two strategies were followed. First is the construction of a virtual library of molecules using DesMol2 program and a subsequent selection of potential active ones. Second is the selection of molecules from the literature on the basis of molecular scaffolds. More than 700 diphenylamine derivatives designed and other 60 fluazinam's derivatives with structural similarity higher than 80% were studied. Almost twenty percent of the molecules analyzed show potential activity against the three fungal species.

Synthesis and biological activity of benzoylcyclohexanedione herbicide SYP-9121

Benzoylcyclohexanedione herbicides work by inhibiting 4-hydroxyphenylpyruvate dioxygenase which was the last new target site introduced for herbicides. In an attempt to find new 4-hydroxyphenylpyruvate dioxygenase inhibitors with high efficacy and selectivity, a novel benzoylcyclohexanedione compound SYP-9121 was synthesized and studied in greenhouse and field. In the greenhouse, SYP-9121 showed broad spectrum herbicidal activity and good safety to maize. Its control of barnyard grass, crabgrass, redroot pigweed, purslane, dayflower and night shade was equivalent to that of the commercial herbicide mesotrione. Three field trials in summer maize showed that SYP-9121 could efficiently control both grass and broadleaf weeds with good selectivity. Herbicidal activity of SYP-9121 was comparable to that of mesotrione.

Intermediate derivatisation method in the discovery of new acaricide candidates: synthesis of N-substituted piperazine derivatives and their activity against phytophagous mites

BACKGROUND

To discover and exploit novel acaricidal compounds, a series of novel N-substituted piperazine derivatives were designed and synthesised using a tert-butyl piperazine-1-carboxylate as the starting material by intermediate derivatisation methods, and their acaricidal activities were evaluated.

RESULTS

Compounds 11 and 12 exhibited significant acaricidal activity against adults of Tetranychus cinnabarinus in greenhouse tests. Compound 12, in particular, was found to be the best potential candidate acaricide and proved to be more active than the commercial positive controls spirodiclofen and pyridaben, with an LC₅₀ of 0.8977 mg L^-1 . Results concerning acaricidal activity against larvae and eggs of T. cinnabarinus indicated that compound 12 possessed equivalent larvicidal activity to spirodiclofen and higher larvicidal activity than pyridaben. Meanwhile, compound 12 showed less ovicidal activity than pyridaben, but higher activity than spirodiclofen. Furthermore, the results of the field trial demonstrated that compound 12 could effectively control Panonychus citri and P. ulmi with long-lasting persistence and rapid action.

CONCLUSIONS

The present work indicates that compound 12 could be a novel acaricide candidate for spider mite control. © 2016 Society of Chemical Industry.

Synthesis and biological activity of pyridazine amides, hydrazones and hydrazides

BACKGROUND

Optimization studies on compounds initially designed to be herbicides led to the discovery of a series of [6-(3-pyridyl)pyridazin-3-yl]amides exhibiting aphicidal properties. Systematic modifications of the amide moiety as well as the pyridine and pyridazine rings were carried out to determine if these changes could improve insecticidal potency.

RESULTS

Structure-activity relationship (SAR) studies showed that changes to the pyridine and pyridazine rings generally resulted in a significant loss of insecticidal potency against green peach aphids [Myzus persicae (Sulzer)] and cotton aphids [(Aphis gossypii (Glover)]. However, replacement of the amide moiety with hydrazines, hydrazones, or hydrazides appeared to be tolerated, with small aliphatic substituents being especially potent.

CONCLUSIONS

A series of aphicidal [6-(3-pyridyl)pyridazin-3-yl]amides were discovered as a result of random screening of compounds that were intially investigated as herbicides. Follow-up studies of the structure-activity relationship of these [6-(3-pyridyl)pyridazin-3-yl]amides showed that biosteric replacement of the amide moiety was widely tolerated suggesting that further opportunities for exploitation may exist for this new area of insecticidal chemistry. Insecticidal efficacy from the original hit, compound 1, to the efficacy of compound 14 produced greater than 10-fold potency improvement against Aphis gossypii and greater than 14-fold potency improvement against Myzus persicae. © 2016 Society of Chemical Industry.

Design, Synthesis, and Structure-Activity Relationship of New Pyrimidinamine Derivatives Containing an Aryloxy Pyridine Moiety

The pyrimidinamine diflumetorim is an ideal template for the discovery of agrochemical lead compounds due to its unique mode of action, novel chemical structure, and lack of reported resistance. To develop a new pyrimidinamine fungicide effective against cucumber downy mildew (CDM), a series of new pyrimidinamine derivatives containing an aryloxy pyridine moiety were designed and synthesized by employing the recently reported intermediate derivatization method (IDM). The structures of all compounds were identified by ¹H NMR, elemental analyses, HRMS, and X-ray diffraction. Bioassays demonstrated that some of the title compounds exhibited excellent fungicidal activities against CDM. Compound 9 gave the best activity (EC₅₀ = 0.19 mg/L), which is significantly better than the commercial fungicides diflumetorim, flumorph, and cyazofamid. The relationship between structure and fungicidal activity of the synthesized pyrimidinamines was explored. The study showed that compound 9 is a promising fungicide candidate for further development.