Synthesis and insecticidal activities of novel N-sulfenyl-N'-tert-butyl-N,N'-diacylhydrazines. 1. N-alkoxysulfenate derivatives

Synthesis and insecticidal activity studies of novel phenylpyrazole derivatives containing arylimine or carbimidate moiety

Phenylpyrazole insecticides are successful for crop protection and public hygiene by blocking gamma-aminobutyric acid (GABA)-gated chloride channels and glutamate-gated chloride (GluCl) channels. A series of novel phenylpyrazoles containing arylimine or 1-methoxyaryl groups were designed and synthesized. The addition reaction of methanol to the imines 1-11 was investigated and the cayno addition products 13-15 were obtained. The compounds 1-15 were confirmed by ¹H NMR and elemental analysis. The results of bioassay indicated that some compounds exhibited comparable bioactivity to fipronil against a broad spectrum of insects such as bean aphid (Aphis craccivora), mosquito (Culex pipiens pallens), diamondback moth (Plutella xylostella) and Oriental armyworm (Mythimna separata). Especially, the foliar contact activity against bean aphid of compound 7 at 10 µg mL^-1 was 68%, the larvacidal activity against mosquito of compounds 5, 13 and 15 at 0.0025 µg mL^-1 was 100%, the larvacidal activity against diamondback moth of compounds 9 and 11 at 0.05 µg mL^-1 was 100%, the larvacidal activity against Oriental armyworm of compound 9 at 1 µg mL^-1 was 100%. The 3-cayno moiety on pyrazole ring was essential for the high insecticidal activities against bean aphid, diamondback moth and Oriental armyworm, while the 3-carbimidate moiety on pyrazole ring was crucial to the excellent high insecticidal activities against mosquito.

Investigation of Novel Pesticides with Insecticidal and Antifungal Activities: Design, Synthesis and SAR Studies of Benzoylpyrimidinylurea Derivatives

In order to find pesticides with insecticidal and antifungal activities, a series of novel benzoyl pyrimidinylurea derivatives were designed and synthesized. All target compounds were identified by ¹H-NMR spectroscopy and HRMS. Insecticidal and antifungal activity of these compounds were evaluated and the structure-activity relationships (SAR) were clearly and comprehensively illustrated. Compound 7, with low toxicity to zebrafish (LC50 = 378.387 µg mL-1) showed 100% inhibition against mosquito (Culex pipiens pallens) at 0.25 µg mL-1. Both compounds 19 and 25 exhibited broad-spectrum fungicidal activity (>50% inhibitory activities against 13 phytopathogenic fungi), which were better than those of the commercial pesticide pyrimethanil (>50% inhibitory activities against eight phytopathogenic fungi). Furthermore, compounds 19 and 25 exhibited protective activity against Sclerotinia sclerotiorum on leaves of Brassica oleracea L. during in vivo experiments.

Crystal structure of 1-phenyl-N′-(1-phenyl-5-(thiophen-2-yl)-1H-pyrazole-3-carbonyl)-5-(thiophen-2-yl)-1H-pyrazole-3-carbohydrazide, C28H20N6O2S2

C28H20N6O2S2, triclinic, P1̅ (no. 2), a = 10.6738(6) Å, b = 11.7869(7) Å, c = 12.5381(7) Å, α = 112.842(6)°, β = 91.963(4)°, γ = 116.129(6)°, V = 1264.38(15) Å3, Z = 2, R gt(F) = 0.0523, wR ref(F 2) = 0.1390, T = 296(2) K.

Natural Product-Based Pesticide Discovery: Design, Synthesis and Bioactivity Studies of N-Amino-Maleimide Derivatives

Natural products are an important source of pesticide discovery. A series of N-amino-maleimide derivatives containing hydrazone group were designed and synthesized based on the structure of linderone and methyllinderone which were isolated from Lindera erythrocarpa Makino. According to the bioassay results, compounds 2 and 3 showed 60% inhibition against mosquito (Culex pipiens pallens) at 0.25 µg·mL−1. Furthermore, the results of antifungal tests indicated that most compounds exhibited much better antifungal activities against fourteen phytopathogenic fungi than linderone and methyllinderone and some compounds exhibited better antifungal activities than commercial fungicides (carbendazim and chlorothalonil) at 50 µg·mL−1. In particular, compound 12 exhibited broad-spectrum fungicidal activity (>50% inhibitory activities against 11 phytopathogenic fungi) and compounds 12 and 14 displayed 60.6% and 47.9% inhibitory activity against Rhizoctonia cerealis at 12.5 µg·mL−1 respectively. Furthermore, compound 17 was synthesized, which lacks N-substituent at maleimide and its poor antifungal activity against Sclerotinia sclerotiorum and Rhizoctonia cerealis at 50 µg·mL−1 showed that the backbone structure of N-amino-maleimide derivatives containing hydrazone group was important to the antifungal activity.

Synthesis and insecticidal activity of diacylhydrazine derivatives containing a 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole scaffold

Background

The diacylhydrazine derivatives have attracted considerable attention in recently years due to their simple structure, low toxicity, and high insecticidal selectivity. As well as 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole is an important scaffold in many insecticidal molecules. In an effort to discover new molecules with good insecticidal activity, a series of diacylhydrazine derivatives containing a 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole scaffold was synthesized and bio-assayed.

Results

Bioassays demonstrated that some of the title compounds exhibited favorable insecticidal activities against Helicoverpa armigera and Plutella xylostella. The insecticidal activity of compounds 10g, 10h, and 10w against H. armigera were 70.8, 87.5, and 79.2%, respectively. Compounds 10c, 10e, 10g, 10h, 10i, 10j and 10w showed good larvicidal activity against P. xylostella. In particular, the LC₅₀ values of compounds 10g, 10h, and 10w were 27.49, 23.67, and 28.90 mg L⁻¹, respectively.

Conclusions

A series of diacylhydrazine derivatives containing a 3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole scaffold was synthesized and bio-assayed. The results of insecticidal tests revealed that the synthesized diacylhydrazine derivatives possessed weak to good insecticidal activities against H. armigera and P. xylostella. Compounds 10g, 10h, and 10x showed much higher insecticidal activity than tebufenozide, and exhibited considerable prospects for further optimization. Primary structure–activity relationship revealed that phenyl, 4-fluoro phenyl and four fluorophenyl showed positive influence on their insecticidal activities, and introduction of a heterocyclic ring (pyridine and pyrazole) showed negative impacts on their insecticidal effects.

Electronic supplementary material

The online version of this article (doi:10.1186/s13065-017-0279-z) contains supplementary material, which is available to authorized users.

Design, Synthesis, Acaricidal/Insecticidal Activity, and Structure-Activity Relationship Studies of Novel Oxazolines Containing Sulfone/Sulfoxide Groups Based on the Sulfonylurea Receptor Protein-Binding Site

Enormous compounds containing sulfone/sulfoxide groups have been used in a variety of fields, especially in drug and pesticide design. To search for novel environmentally benign and ecologically safe pesticides with unique modes of action, a series of 2,4-diphenyl-1,3-oxazolines containing sulfone/sulfoxide groups as chitin synthesis inhibitors (CSIs) were designed and synthesized on the basis of the sulfonylurea receptor protein-binding site for CSIs. Their structures were characterized by (1)H and (13)C nuclear magnetic resonance and high-resolution mass spectrometry. The acaricidal and insecticidal activities of the new compounds were evaluated. It was found that most of the target compounds displayed wonderful acaricidal activities against spider mite (Tetranychus cinnabarinus) larvae and eggs. Especially compounds I-4, II-3, and II-4 displayed higher activities than commercial etoxazole at a concentration of 2.5 mg L(-1). Some target compounds exhibited insecticidal activities against lepidopteran pests. The present work demonstrated that these compounds containing sulfone/sulfoxide groups could be considered as potential candidates for the development of novel acaricides in the future.

Synthesis and Larvicidal Activity of Novel Thenoylhydrazide Derivatives

A pair of chemical isomeric structures of novel N-tert-butylphenyl thenoylhydrazide compounds I and II were designed and synthesized. Their structures were characterized by MS, IR, ¹H NMR, elemental analysis and X-ray single crystal diffraction. The regioselectivity of the Meerwein arylation reaction and the electrophilic substitution reaction of N-tert-butyl hydrazine were studied by density functional theory (DFT) quantum chemical method. The larvicidal tests revealed that some compounds I had excellent larvicidal activity against Culex pipiens pallens. As the candidates of insect growth regulators (IGRs), the larval growth inhibition and regulation against Culex pipiens pallens were examined for some compounds, especially I1 and I7. Compounds I1 and I7 were further indicated as an ecdysteroid agonist by reporter gene assay on the Spodoptera frugiperda cell line (Sf9 cells). Finally, a molecular docking study of compound I7 was conducted, which was not only beneficial to understand the structure-activity relationship, but also useful for development of new IGRs for the control of mosquitos.

Synthesis, biological activities and SAR studies of novel 1-Ethyl-7-methyl-4-oxo-1,4-dihydro-[1,8]naphthyridine-3-carboxylic acid based diacyl and sulfonyl acyl hydrazines

BACKGROUND

Diacyl hydrazines have attracted significant interest in medicine, pesticide chemistry and material science. It is an important class of insect growth regulators. In this study, acyl hydrazine, the essential active group was incorporated in to nalidixic acid with the aim of combining the active groups to generate more potent agrochemical.

RESULTS

Various nalidixic acid based diacyl and sulphonyl acyl hydrazines derivatives were synthesized and characterized by spectral techniques. These compounds were screened for the antifungal activity against five pathogenic fungi, nitrification inhibitory activity and insect growth regulator (IGR) activity against Spodoptera litura. The fungicidal activity was screened against R. bataticola, S. rolfsii, R. solani, F. oxysporum and A. porri. Most of the compounds showed moderate to good antifungal activity against A. porri (ED50 = 29.6-495.9 µg/mL). All the compounds showed significant nitrification inhibitory activity at 5% level. IGR activity was examined by feeding method against S. litura.

CONCLUSION

The study revealed that a few compounds possessed good activity against three different pests namely certain fungus, soil bacteria and insect, among which, compound 37 (R' = 4-chlorophenyl) behaved the best.

Design, synthesis, biological activities and 3D-QSAR of new N,N'-diacylhydrazines containing 2,4-dichlorophenoxy moieties

A series of new N,N'-diacylhydrazine derivatives were designed and synthesized. Their structures were verified by 1H-NMR, MS and elemental analysis. The herbicidal activities and plant growth regulating activity of these N,N'-diacylhydrazines were evaluated. The herbicidal activity results showed that most of these N,N'-diacyl-hydrazines showed excellent in vivo activities against Echinochloa crus-galli, Digitaria sanguinalis, Brassica napus, Amaranthus retroflerus. Most of them exhibited higher herbicidal activities against dicotyledonous weeds than monocotyledonous weeds. To further investigate the structure-activity relationship, comparative molecular field analysis (CoMFA) was performed on the basis of herbicidal activity data. Both the steric and electronic field distributions of CoMFA are in good agreement in this work.

Design, synthesis and insecticidal activities of novel pyrazole amides containing hydrazone substructures

BACKGROUND

Pyrazole and hydrazone derivatives possess good insecticidal activities; their substructural units are widely used in pesticide design. In an effort to discover new molecules with good insecticidal activities, a series of pyrazole amide derivatives containing hydrazone substructures were synthesised and bioassayed.

RESULTS

Bioassays demonstrated that some of the title compounds exhibited notable control of Plutella xylostella (Linnaeus), Helicoverpa armigera (Hübner), Culex pipiens pallens, Laphygma exigua (Hübner), Spodoptera litura (Fabricius), Nilaparvata lugens (Stål) and Rhopalosiphum maidis (Fitch) at 5, 10, 0.25, 200, 20, 100 and 500 mg L(-1) respectively. Comparative molecular field analysis (CoMFA) based on the bioactivities for P. xylostella was studied; the values of q(2) and r(2) for the CoMFA model were 0.701 and 0.964 respectively.

CONCLUSION

Some of the title compounds displayed good and broad-spectrum insecticidal activities against different insect species; the CoMFA model revealed that a bulky and negatively charged group at the 4-position of benzene could enhance insecticidal activity. These results could provide useful information for the design of novel insecticide containing substructural units of pyrazole amide and hydrazone.

Design and development of novel insect growth regulators: synthesis, characterization and effect of benzoyl thymyl thioureas and ureas on total haemocyte count of Dysdercus koenigii

Insect-growth regulators (IGRs) have been receiving foremost attention as potential means of selective insect control. Benzoyl phenyl urea (BPU) is a well-known IGR having chitin synthesis inhibitor activity. Mimics of BPU have been synthesized by suitable derivatization of a naturally occurring monoterpenoid, thymol (2-isopropyl-5-methyl phenol) to form a = series of substituted benzoyl thymyl thioureas (BTTUs) [IVa-f] and benzoyl thymyl ureas (BTUs) [Va-f]. The synthesized compounds have been characterized by (1)H and (13)C NMR, LC-MS and elemental analysis. These derivatives have been screened for their effect on total haemocyte count of Dysdercus koenigii. It has been observed that the introduction of substituted benzoyl thiourea and urea linkage into a thymol ring via an amino group results in higher activity than the parent compound thymol and a comparable pattern of results with the standard insect-growth regulators, Penfluron. Urea [Va-f] compounds exhibited greater effect on Total Haemocyte Count (THC) than thiourea [IVa-f]. Fluoro substitution enhanced the effect on THC more than chloro substituted compounds, while ortho-substitution resulted in a better effect than para-substitution. The results described in this paper are promising and provide new array of synthetic chemicals that may be utilized as insect growth regulators.

Design, synthesis, structure, and acaricidal/insecticidal activity of novel spirocyclic tetronic acid derivatives containing an oxalyl moiety

A series of novel spirocyclic tetronic acid derivatives containing an oxalyl moiety was designed and synthesized via the key intermediate 3-(2,4,6-trimethyl)-2-oxo-1-oxaspiro[4.4]-decyl-3-en-4-ol. The target compounds were identified by (1)H NMR and elemental analysis or high-resolution mass spectrum (HRMS). The results of bioassays indicated that most of the target compounds possessed excellent acaricidal activities against carmine spider mite larvae and eggs. Especially, diisopropylamino oxalyl compound 7g and piperidine oxalyl compound 7h were 1.4- and 2.3-fold as high as the activities of commercial Spiromesifen, respectively, against spider mite eggs. Moreover, most of the target compounds exhibited insecticidal activities against Lepidoptera pest. Interestingly, compounds containing alkylamino-substituted oxalyl moiety showed obvious selectivity between spider mite larvae and eggs because the activities against spider mite eggs of 7g and 7h were 25-fold those against spider mite larvae, whereas Spiromesifen had no significant differences in these activities. This meant that the introduction of an oxalyl moiety to spirocyclic tetronic acid might lead to novel biological activity characteristics.

Design, synthesis, and insecticidal activities of novel monohalovinylated pyrethroids

A series of novel monohalovinylated pyrethroids are designed and synthesized to replace one halo atom with a hydrogen atom on the double bond of dihalopyrethroids. Bioassays indicate that some of the synthesized compounds, such as 3j and 1j, exhibit high insecticidal activities against mosquitoes ( Culex pipiens pallens ), oriental armyworms ( Mythimna separata ), alfalfa aphids ( Aphis medicagini ), and carmine spider mites ( Tetranychus cinnabarinus ). Photolytic results of E-cis-1j suggest that monohalovinylated pyrethroids are photodegraded more easily than compound 12.

Design, synthesis and insecticidal activity of novel phenylpyrazoles containing a 2,2,2-trichloro-1-alkoxyethyl moiety

A series of novel phenylpyrazoles containing a 2,2,2-trichloro-1-alkoxyethyl moiety were designed and synthesized via the key intermediate 5-trichloroethylideneimino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-alkylsulfenylpyrazole (5). The addition reaction of the imine 5 was closely related with the nature of the alcohol. The target compounds were confirmed by (1)H NMR and elemental analysis. The results of bioassays indicated that the target compounds possessed excellent activities against a broad spectrum of insects such as bean aphid (Aphis craccivora), mosquito (Culex pipiens pallens) and diamondback moth (Plutella xylostella). Especially, the foliar contact activity against bean aphid of compound 7h at 2.5 mg kg(-1) was 89%, the larvacidal activity against mosquito of compound 6c at 2.5 microg kg(-1) was 100%, the activity against diamondback moth of compound 7a at 5 mg kg(-1) was 87%, and all of these activities were much higher than the contrast ethiprole. The results of insecticidal activities showed that the two pairs of enantiomers 7d-1 and 7d-2 gave activities without distinctive difference, and it was the similar situation for 7e-1 and 7e-2. Interestingly, the target compounds exhibited high selectivity between diamondback moth and oriental armyworm, both of which are of the order Lepidoptera. The 2,2,2-trichloro-1-alkoxyethyl moiety was essential for high insecticidal activities.

Synthesis and insecticidal activities and SAR studies of novel benzoheterocyclic diacylhydrazine derivatives

Two series of novel N'-tert-butyl-N'-substituted benzoyl-N-2,3-dihydrobenzofuran-5-carbohydrazide derivatives were synthesized, their activities and different insecticidal action modes for different Lepidopteral larvicidal assays were evaluated carefully. The results of larvicidal activities against oriental armyworm and mosquito indicate that different benzoheterocyclic analogues of diacylhydrazide have different structure-activity relationships according to the types and patterns of substitution on the benzene, and 3,5-dimethyl is the most efficient substituent for benzoheterocyclic diacylhydrazine. Among them, N'-tert-butyl-N'-(3,5-dimethylbenzoyl)-N-2,4-dimethyl-2,3-dihydrobenzofuran-5-carbohydrazide (Ii) stood out as the best compound with high activity. Compound Ii and N'-tert-butyl-N'-(3,5-dimethylbenzoyl)-N-5-chloro-6-chromanecarbohydrazide (F) have higher contact activities against diamond-back moth and stomach toxicities against cotton bollworm than ANS-118 and JS-118. Compound F has higher contact toxicity against beet armyworm than ANS-118 and JS-118. These results indicate that different heterocycles and substitutents on the benzene rings of benzoheterocyle moiety not only influence the larvicidal activities strongly but also are very sensitive to the insecticidal action modes for different Lepidopteran larvicidal insects.

Synthesis and insecticidal activities of novel N-sulfenyl-N'-tert-butyl-N,N'-diacylhydrazines. 3. N-(alkyldithio), n-(aminothio), and N,N-dithio derivatives

A series of novel N-(alkyldithio) and N-aminothio derivatives of N'-tert-butyl-N,N'-diacylhydrazines were designed and synthesized as insect growth regulators via the key intermediates N-chlorosulfenyl-N'-tert-butyl-N,N'-diacylhydrazines. A series of novel N,N-dithio derivatives were also designed and synthesized with N'-tert-butyl-N,N'-diacylhydrazines and sulfur chloride in the presence of sodium hydride. Compared to the parent compounds, these derivatives displayed better solubility and improved hydrophobicities. The insecticidal activities of the target compounds were evaluated. The results of bioassays showed that the target compounds possessed comparable activities against oriental armyworm with the corresponding parent compounds. In particular, N-(morpholinosulfenyl)-N'-tert-butyl-N-4-ethylbenzoyl-N'-3,5-dimethylbenzoylhydrazide (IIIk) has higher toxicities against oriental armyworm and diamondback moth than the parent compound, RH-5992.

Synthesis, insecticidal, and acaricidal activities of novel 2-aryl-pyrrole derivatives containing ester groups

A series of novel 2-aryl-pyrrole derivatives containing ester groups were synthesized, and their structures were characterized by (1)H NMR spectroscopy and elemental analysis. The insecticidal activities against oriental armyworm, mosquito, diamondback moth, green rice leafhopper, and bean aphids and acaricidal activities against spider mite of these new compounds were evaluated. The results of bioassays indicated that some of these title compounds exhibited excellent insecticidal and acaricidal activities. The insecticidal activities against oriental armyworm of compounds IVa, IVd, IVe, IVf, IVg, IVi, IVk, and IVp were equal to commercialized Chlorfenapyr, and the insecticidal activities of most of compounds IVb, IVc, IVd, IVf, IVg, IVj, IVk, IVl, IVs, IVt, IVu, IVw, IVx, IVz, and Chlorfenapyr against mosquito at 0.10 mg kg (-1) were 100%, and the acaricidal activities of compounds IVd, IVe, IVf, IVg, IVh, IVi, and IVk were equal or superior to Chlorfenapyr. Especially, the results indicated that the acaricidal activity of [4-bromo-2-(4-chlorophenyl)-3-cyano-5-(trifluoromethyl)pyrrol-1-yl]methyl 3-methylbutanoate ( IVg) against spider mite was 2.65-fold as high as that of Chlorfenapyr from the value of LC 50.

Synthesis, crystal structure, and insecticidal activity of novel N-alkyloxyoxalyl derivatives of 2-arylpyrrole

Two series of novel N-alkyloxyoxalyl derivatives of 2-arylpyrrole were synthesized, and their structures were characterized by (1)H NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction analysis. The insecticidal activities of the new compounds were evaluated. The results of bioassays indicated that some of these title compounds exhibited excellent insecticidal activities, and their insecticidal activities against oriental armyworm, mosquito, and spider mite are comparable to those of the commercialized Chlorfenapyr.

Synthesis and insecticidal activities of novel N-sulfenyl-N'-tert-butyl-N,N'-diacylhydrazines. 2. N-substituted phenoxysulfenate derivatives

A series of novel N-substituted phenoxysulfenyl- N'- tert-butyl- N, N'-diacylhydrazines were designed and synthesized as insect growth regulators via the key intermediates N-chlorosulfenyl- N'- tert-butyl- N, N'-diacylhydrazines. Compared to the parent compounds, these N-substituted phenoxysulfenyl derivatives displayed better solubility and improved hydrophobicities. The insecticidal activities of the new compounds were evaluated. The results of bioassays showed that the title compounds possessed a combination of strong stomach as well as contact poison property higher than the corresponding parent compounds. In particular, N-(4-chlorophenoxy)sulfenyl -N'- tert-butyl- N-4-ethylbenzoyl- N'-3,5-dimethylbenzoylhydrazide ( IIIi) as a field testing candidate has higher stomach toxicities against oriental armyworm and tobacco cutworm than the corresponding parent compound RH-5992. Furthermore, the compound IIIi exhibits higher contact activities against Asian corn borer, tobacco cutworm, and cotton bollworm than RH-5992.