Combined Experimental and Computational Study on the Transformation of a Novel 1,3,4-Oxadiazole Thioether Nematicide in Aqueous Solutions

Abstract

It has been demonstrated that Exianliuyimi (EXLYM) exhibits good nematocidal activity. As a potential nematicide, EXLYM and its transformation products (TPs) may generate emerging pollutants with hazardous effects on the ecosystem. In this study, the fate of EXLYM in aqueous solutions was investigated using experimental and theoretical approaches. Laboratory-scale experiments showed that EXLYM is hydrolytically stable. Microbial processes are primarily responsible for the oxidation of sulfur in aqueous solutions. Under simulated sunlight, the t 1/2 values of EXLYM in acidic, neutral, and alkaline buffer solutions were 5.02, 3.83, and 5.55 h, respectively. Six TPs were identified using a non-target screening strategy realized by ultra-high-performance liquid chromatography coupled with Q-Exactive Orbitrap high-resolution mass spectrometry and 18 O-labeling experiments. Four of these were unambiguously confirmed using authentic standards. Reactive oxygen species scavenging experiments, 18 O-labeling experiments, and quantum-theoretical calculations suggested that EXLYM could degrade mainly through four pathways: sulfur oxidation, nucleophilic aromatic photosubstitution, C−S bond cleavage, and oxidative ring-opening. The proposed degradation kinetics, TPs, and transformation pathways in aqueous solutions provide valuable information on the fate of EXLYM in aquatic ecosystems and lay the foundation for further toxicological tests.

Degradation of the Novel Heterocyclic Insecticide Pyraquinil in Water: Kinetics, Degradation Pathways, Transformation Products Identification, and Toxicity Assessment

“…Due to complex matrix effects and low concentration level, the search for unknown TPs of pesticide, especially those without reference standards, is often difficult. − Recent developments in high-resolution mass spectrometry (HRMS) can provide high sensitivity, high resolution, and accurate mass measurements of both parent compounds and any other compound in the samples, thus making it possible to screen and identify TPs without standards. , Thereinto, ultrahigh-performance liquid chromatography coupled with quadrupole Orbitrap high-resolution mass spectrometry (UHPLC-Orbitrap-HRMS) has become an increasingly prominent platform for the detection and structural elucidation of pesticide TPs. − Meanwhile, a powerful data processing and analysis software Compound Discoverer, which operates with suspect and nontarget screening strategies, was co-applied to make the TP identification simpler and more feasible. − …”

Synthesis and pesticidal activity of new 1,3,4-oxadiazole thioether compounds containing a trifluoromethylpyrazoyl moiety

“…In the last two decades, 1,3,4-oxadiazoles have emerged as the one of the most promising pharmacophores exhibiting important biological activities like anti-tumor [ 20 ], ketol-acid reductoisomerase inhibitors [ 21 ], antiproliferative [ 22 ], anti-SARS-CoV-2 [ 23 ], insecticidal [ 24 ], fungicidal activities [ 25 ], cardioprotective agents [ 26 ], nematocidal activity [ 27 ], anti-TMV activity [ 28 ] and anti-Alzheimer agents [ 29 ]. The hybridization of 1,3,4-oxadiazole unit with several other heterocycles like benzimidazole [ 30 ], coumarin [ 31 ], pyridine [ 32 ], glycosyl [ 33 ], and triazole [ 34 ] has empowered to develop various molecular hybrid displaying excellent activity.…”

Organophosphorus-Catalyzed Direct Dehydroxylative Thioetherification of Alcohols with Hypervalent Organosulfur Compounds

“…Thioethers are widely used in medicines, 1 materials, 2 and agrochemicals. 3 In a variety of chemical processes, including those involving sulfone and NH-sulfoximines, they also serve as a form of helpful building scaffold. 4 As a result, the synthesis of the thioethers using novel synthetic techniques has drawn a lot of attention.…”

“…Thioethers are widely used in medicines, materials, and agrochemicals . In a variety of chemical processes, including those involving sulfone and NH-sulfoximines, they also serve as a form of helpful building scaffold .…”