Heterocyclic compounds play an important role as the main sources of lead molecules of agrochemicals. Synthesis and biological activity of thiadiazole-containing 1,2,4-triazolo[3,4-b][1,3,4]-thiadiazoles were seldom reported. To find novel lead compounds with various biological activities, a series of 6-substituted-3-(4-methyl-1,2,3-thiadiazolyl)[1,2,4]triazolo[3,4-b][1,3,4]thiadizoles were rationally designed and synthesized according to the principle of combinations of bioactive substructures by the condensation of 3-(4-methyl-1,2,3-thiadiazolyl)-4-amino-1,2,4-triazole-5-thione with various carboxylic acids and phosphorus oxychloride. All newly synthesized compounds were identified by proton nuclear magnetic resonance ((1)H NMR), infrared spectroscopy (IR), electroionization mass spectrometry (EI/MS), and elementary analysis. The crystal structure of 3-(4-methyl-1,2,3-thiadiazolyl)-6-(4-methylphenyl)[1,2,4]triazolo[3,4-b][1,3,4]thiadizole was determined by X-ray diffraction crystallography. In this crystal, two intermolecular hydrogen bonds (N2...H-C12 and N3...H-C13), a weak intermolecular interaction (S...S), and the weak ppi-ppi intermolecular interaction were observed. Fungicide screening indicated that all of the target compounds showed certain extent of growth inhibition against fungi tested. 3-(4-Methyl-1,2,3-thiadiazolyl)-6-n-propyl[1,2,4]triazolo[3,4-b][1,3,4]thiadizole and 3-(4-methyl-1,2,3-thiadiazolyl)-6-trichloromethyl[1,2,4]triazolo[3,4-b][1,3,4]thiadizole were found to have potential wide spectrum of fungicide activity. The median effective concentrations (EC(50)) detected for 3-(4-methyl-1,2,3-thiadiazolyl)-6-trichloromethyl[1,2,4]triazolo[3,4-b][1,3,4]thiadizole to six fungi were from 7.28 micromol/L against Pellicularia sasakii (Shirai) to 42.49 micromol/L against Alternaria solani . The results indicated that thiadiazole-containing 1,2,4-triazolo[3,4-b][1,3,4]-thiadiazoles were potential fungicide lead compounds.
N-tert-Butyl-N,N'-diacylhydrazines are nonsteroidal ecdysone agonists used as environmental benign pest regulators. In this paper, two series of new N-tert-butyl-N,N'-diacylhydrazine derivatives containing 1,2,3-thiadiazole were designed and synthesized. All structures of the synthesized compounds were confirmed by proton nuclear magnetic resonance ((1)H NMR), infrared spectroscopy (IR), and high-resolution mass spectrometry (HRMS). Bioasssay results indicated that most of the synthesized compounds possessed good insecticidal activities against Plutella xylostella L. and Culex pipiens pallens as compared with the positive control, tebufenozide. The results of this study indicated that 1,2,3-thiadiazoles, as an important active substructure, could improve or maintain the activity of the dicylhydrazines and favor novel pesticide development.
BACKGROUND Picolinate/picolinic acid compounds are an important class of synthetic auxin herbicides. To explore the herbicidal activity of 6‐pyrazolyl picolinate compounds, a series of 3‐chloro‐6‐pyrazolyl‐picolinate derivatives was designed and synthesized. RESULTS Twenty‐five 3‐chloro‐6‐pyrazolyl‐picolinate derivatives synthesized were tested for herbicidal activity and the IC50 value of compound c5 to the growth of Arabidopsis thaliana root was 27 times lower than that of the commercial herbicide clopyralid. Compound c5 displayed better post‐emergence herbicidal activity and broader (Picloram, Clopyralid, Aminopyralid) herbicidal spectrum at a dosage of 400 g ha−1 in comparison with clopyralid; it also was safe to wheat and maize at this dosage. Arabidopsis thaliana phenotypes and expression of auxin‐response genes demonstrated that compound c5 might be a novel auxin‐type herbicide. Molecular docking analyses revealed that compound c5 had stronger binding ability to receptor AFB5 (auxin signaling F‐box protein 5) than clopyralid. CONCLUSION These 6‐pyrazolyl picolinate compounds could be used as potential lead structures for the discovery of a novel synthetic auxin herbicide. © 2021 Society of Chemical Industry
The Ugi reaction is a green and rapid one-pot reaction for lead derivation. To develop novel candidate pesticides with diverse biological activities, two series of 4-methyl-1,2,3-thiadiazole derivatives containing active substructures of 3-chloro-4-methylphenyl or 3-fluoro-4-methylphenyl, respectively, were rationally designed and synthesized via Ugi reaction according to the principle of combinations of bioactive substructures. All of the structures of newly synthesized compounds were confirmed by proton nuclear magnetic resonance and high-resolution mass spectrometry. Biological activities of the target compounds including fungicide activity, antivirus activity in vitro and in vivo, and systemic acquired resistance were evaluated systematically. The results indicated that derivatives containing 3-(trifluoromethyl)phenyl and 2-methylphenyl possessed a potential wide spectrum of fungicidal activity. Derivatives containing 3-(trifluoromethyl)phenyl and 4-hydroxyphenyl possessed good potential direct antivirus activities against tobacco mosaic virus (TMV) in vitro, and the replacement of Cl atom by F atom improved their direct inhibition activities against TMV in vitro. Derivatives containing phenyl, 2-(trifluoromethyl)phenyl, 3-(trifluoromethyl)phenyl, 3-nitrophenyl, 4-nitrophenyl, 2-methylphenyl, and 4-hydroxyphenyl possessed good potential bioactivities in vivo including protection, inactivation, curative, and induction activities against TMV. These studies indicate that the newly synthesized 4-methyl-1,2,3-thiadiazole derivatives possessed good potential bioactivities, and a combination of bioactive substructures via Ugi reaction was an effective way to find bioactive compounds for novel pesticide development.
1,2,3-Thiadiazoles, an important synthetic active substructure, are nowadays becoming one of the important branches in novel pesticide development. To develop pesticide candidates with diverse biological activities and probe their structure-activity relationship, three series of 5-methyl-1,2,3-thiadiazoles were rationally designed and synthesized using a simple and convenient one-step synthetic procedure via Ugi reaction. Biological activities of the target compounds including fungicidal activity, antivirus activity in vitro and in vivo, and systemic acquired resistance were systematically evaluated. The results indicated that compound III(10) showed broad-spectrum of activities against most fungi tested, and compounds I(10) and II(17) showed excellent potential antivirus activities as compared to positive control agent ribavirin. The preliminary structure-activity relationship was also discussed. The results of these studies indicated that the 5-position-substituted 1,2,3-thiadiazoles exhibited good antivirus activity and were worthy of further study in pesticide development.
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