Two series of new nitromethylene neonicotinoid analogues (2a-2h and 3a-3h) were designed and prepared, with the cis-configuration confirmed by X-ray diffraction. Preliminary bioassays showed that most analogues exhibited excellent insecticidal activities at 500 mg/L, and analogues with optical activity (2c-2g) were highly potent at 100 mg/L, while compound 2d had >90% mortality at 20 mg/L, which suggested that it could be used as a lead for future insecticides development. Modeling the ligand-receptor complexes by molecular docking study explained the structure-activity relationships observed in vitro and revealed an intriguing molecular binding mode at the active site of the nAChR model, thereby possibly providing some useful information for future receptor structure-based designs of novel insecticidal compounds.

Nitromethylene neonicotinoids analogues with tetrahydropyrimidine fixed cis-configuration: synthesis, insecticidal activities, and molecular docking studies.

The environmental fates of nitenpyram (NPM), a widely used neonicotinoid insecticide, are not well-known. A thin solid film of NPM deposited on a germanium attenuated total reflectance (ATR) crystal was exposed to radiation from a low-pressure mercury lamp at 254 nm, or from broadband low pressure mercury photolysis lamps centered at 350 or 313 nm. The loss during photolysis was followed in time using FTIR. The photolysis quantum yields (ϕ), defined as the number of NPM molecules lost per photon absorbed, were determined to be (9.4 ± 1.5) × 10–4 at 350 nm, (1.0 ± 0.3) × 10–3 at 313 nm, and (1.2 ± 0.4) × 10–2 at 254 nm (±2σ). Imines, one with a carbonyl group, were detected as surface-bound products and gaseous N2O was generated in low (11%) yield. The UV–vis absorption spectra of NPM in water was different from that in acetonitrile, dichloromethane, and methanol, or in a thin solid film. The photolytic lifetime of solid NPM at a solar zenith angle at 35° is calculated to be 36 min, while that for NPM in w...

Photochemistry of Solid Films of the Neonicotinoid Nitenpyram.

The neonicotinoid nitenpyram (NPM) is a multifunctional nitroenamine [(R1N)(R2N)C=CHNO2] pesticide. As a nitroalkene, it is structurally similar to other emerging contaminants such as the pharmaceuticals ranitidine and nizatidine. Because ozone is a common atmospheric oxidant, such compounds may be oxidized on contact with air to form new products that have different toxicity compared to the parent compounds. Here we show that oxidation of thin solid films of NPM by gas-phase ozone produces unexpected products, the majority of which do not contain oxygen, despite the highly oxidizing reactant. A further surprising finding is the formation of gas-phase nitrous acid (HONO), a species known to be a major photolytic source of the highly reactive hydroxyl radical in air. The results of application of a kinetic multilayer model show that reaction was not restricted to the surface layers but, at sufficiently high ozone concentrations, occurred throughout the film. The rate constant derived for the O3-NPM reaction is 1 × 10-18 cm3⋅s-1, and the diffusion coefficient of ozone in the thin film is 9 × 10-10 cm2⋅s-1 These findings highlight the unique chemistry of multifunctional nitroenamines and demonstrate that known chemical mechanisms for individual moieties in such compounds cannot be extrapolated from simple alkenes. This is critical for guiding assessments of the environmental fates and impacts of pesticides and pharmaceuticals, and for providing guidance in designing better future alternatives.

Unexpected formation of oxygen-free products and nitrous acid from the ozonolysis of the neonicotinoid nitenpyram.

Novel nitenpyram analogues with tetrahydropyridone-fixed cis-configuration : synthesis, insecticidal activities, and molecular docking studies

Neonicotinoid (NN) pesticides have widespread use, largely replacing other pesticides such as the carbamates. Hence, there is a need to understand their environmental fates at a molecular level in various media, especially water. We report here the studies of a nitroenamine NN, nitenpyram (NPM), in aqueous solution where the absorption cross sections in the actinic region above 290 nm are observed to dramatically decrease compared to those in nonaqueous solvents. Quantum chemical calculations show that addition of a proton to the tertiary amine nitrogen in NPM breaks the conjugation in the chromophore, shifting the absorption to shorter wavelengths, consistent with experiment. However, surprisingly, adding a proton to the secondary amine nitrogen leads to its immediate transfer to the NO2 group, preserving the conjugation. This explains why the UV absorption of ranitidine (RAN), which has a similar chromophore but only secondary amine nitrogens, does not show a similar large blue shift in water. Photolysi...

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Experimental and Theoretical Studies of the Environmental Sensitivity of the Absorption Spectra and Photochemistry of Nitenpyram and Analogs

In the title compound, C11H15ClN4O2, the amino group is involved in intra- and inter­molecular N—H⋯O hydrogen bonds. The former contributes to the mol­ecular conformation, while the latter link the mol­ecules into centrosymmetric dimers. The crystal structure also exhibits weak inter­molecular C—H⋯O inter­actions.

https://journals.iucr.org/e/issues/2008/06/00/cv2407/cv2407.pdf

(E)-N-(6-Chloro-3-pyridylmeth-yl)-N-ethyl-N'-methyl-2-nitro-ethyl-ene-1,1-diamine.

The title compound, C7H12O3, was synthesized as an inter­mediate for the synthesis of the selective broad-spectrum nonsystemic acaricide spiro­diclofen (trade name Envidor). The cyclo­hexane ring adopts a chair conformation. The mol­ecules pack in layers, with O—H⋯O hydrogen bonds connecting the layers on one side and only van der Waals inter­actions on the other side.

1-Hydroxycyclohexanecarboxylic acid

The title compound, C12H14N2O3, was synthesized as an inter­mediate for the synthesis of metamitron. The benzene ring forms dihedral angles of 86.3 (2) and 10.0 (3)° with the ethyl group and the acetyl­imino plane, respectively. The crystal structure involves inter­molecular C—H⋯O and N—H⋯O hydrogen bonds.

/pdf/ethyl-2-acetyl-hydrazono-2-phenyl-acetate-48ja32leea.pdf

Ethyl 2-acetyl-hydrazono-2-phenyl-acetate.

The title compound, C10H12N4O2, was prepared as an inter­mediate for the synthesis of metamitron. The benzene ring plane forms dihedral angles of 66.0 (1) and 3.5 (5)° with the hydrazine plane and the acetyl­imino plane, respectively. The crystal structure involves inter­molecular N—H⋯O hydrogen bonds.

/pdf/2-acetyl-hydrazono-2-phenyl-aceto-hydrazide-3q0qcq8vqn.pdf

2-Acetyl­hydrazono-2-phenyl­aceto­hydrazide

The title compound, C20H15Cl4N3O, was prepared by the reaction of 2,2-bis­(2,6-dichloro­styr­yl)oxirane and 1,2,4-triazole. In the crystal structure, mol­ecules assemble along the b axis, forming helical suprastructures, which further assemble along the c axis, forming two-dimensional layer structures.

Xu Yi

Papers

(E)-N-(6-Chloro-3-pyridylmeth-yl)-N-ethyl-N'-methyl-2-nitro-ethyl-ene-1,1-diamine.

1-Hydroxycyclohexanecarboxylic acid

Ethyl 2-acetyl-hydrazono-2-phenyl-acetate.

2-Acetylhydrazono-2-phenylacetohydrazide

1,5‐Bis(2,6‐dichlorophenyl)‐3‐[(1H‐1,2,4‐triazol‐1‐yl)methyl]penta‐1,4‐dien‐3‐ol

Xu Yi

Papers

(E)-N-(6-Chloro-3-pyridylmeth-yl)-N-ethyl-N'-methyl-2-nitro-ethyl-ene-1,1-diamine.

1-Hydroxycyclohexanecarboxylic acid

Ethyl 2-acetyl-hydrazono-2-phenyl-acetate.

2-Acetyl­hydrazono-2-phenyl­aceto­hydrazide

1,5‐Bis(2,6‐dichlorophenyl)‐3‐[(1H‐1,2,4‐triazol‐1‐yl)methyl]penta‐1,4‐dien‐3‐ol

2-Acetylhydrazono-2-phenylacetohydrazide