Pyridine Derivatives as Insecticides─Part 4: Synthesis, Crystal Structure, and Insecticidal Activity of Some New Thienylpyridines, Thienylthieno[2,3-b]pyridines, and Related Heterocyclic Derivatives

Functionalized Thiadiazole: Synthesis, insecticidal activity, molecular docking and DFT studies of some new 5-substituted 1,2,4-Thiadiazoles based on Norfloxacin

Through plant protection, we hope to contribute to the growth of cotton production-the most significant non-food agricultural commodity. The use of safe substitutes for pesticides has become essential because of a number of grave problems related to their use. Consequently, families of novel environmentally benign Norfloxacin series with insecticidal efficacy based on 5-Substituted 1,2,4-thiadiazoles were identified. The Target synthesized compounds were confirmed by elemental and modern spectroscopic analyses (such as IR, UV, 1H NMR and 13C NMR). The toxicological activity of this compounds were checked towards nymphs and adults of Aphis gossypii which the most affected compound 7 had an LC50 of 0.907 mg/L, while the LC50 of commercial thiacloprid was 0.255 mg/L. Due to the presence of carboxalic acid and fluorophenyl groups in their chemical composition, component 7 may be especially effective. Density Functional Theory (DFT) analysis of the synthesized compounds using the B3LYP hybrid functional and the 6-311G(d,p) basis set provided valuable insights into their electronic properties and chemical reactivity. Frontier Molecular Orbital (FMO) analysis revealed that compound 7, with the smallest HOMO-LUMO gap (ΔE = 2.94 eV), exhibited the highest reactivity, suggesting its potential for significant biological interactions. Moreover, molecular docking studies against the 4EY4 hydrolase enzyme indicated strong binding affinities for compounds 3, 5, 7 and 8 with docking scores surpassing the standard Thiacloprid, confirming their enhanced bioactivity. These results, when correlated with quantum chemical parameters and biological assays, highlight the promising therapeutic potential of the new compounds, especially compound 7.

Exploring the larvicidal and pupicidal activities of new functionalized pyridines against Culex pipiens L. referring to molecular docking and SAR studies

Pesticides are intensively employed to manage pests, but they pose a great challenge, developing pesticide resistance. So, searching for novel chemical structures is crucial to overcoming insecticide resistance. Herein, a new functionalized pyridine derivative 4 was effectively constructed in a one-step reaction through reacting four components, including piperonal, ethyl cyanoacetate, 2-acetylthiophene, and ammonium acetate, under ultrasonic conditions. Treatment of the derivative 5 with hydrazine hydrate in ethanol afforded the acetohydrazide derivative 8 that was utilized as a key precursor for the synthesis of Schiff's bases and other nicotinonitriles. Moreover, new acetohydrazone derivatives (19-21) were furnished by the reaction of 8 with isatin, n-vinylpyrrolididone, and galactose, respectively. The data obtained from the spectral measurements was the basis for elucidating the structures of the new derivatives. The larvicidal and pupicidal potencies of the synthesized thienyl pyridine derivatives were assessed against Culex pipiens L., and most exhibited moderate to good activity. The larvae were more susceptible to 17, 19, 6 and 13 with LC50 of 1.57, 1.91, 2.36 and 2.90 ppm, respectively, while pupae were less susceptible with LC50 of 4.17, 5.03, 6.16 and 7.45 ppm, respectively. The various functional groups connected to the pyridine ring led to variations in the toxicity of synthesized compounds, which were clarified through the SAR study. At the same time, a molecular docking study was performed to demonstrate the compound's mode of action and the effect of inserted moieties on binding with the nicotinic acetylcholine receptors (nAChRs). Collectively, the results imply that the thienyl pyridine derivatives could be used as mosquitocidal agents against C. pipiens larvae and pupae.

Green synthesis, anti-inflammatory evaluation and molecular docking of novel pyridines via one pot multi-component reaction using ultrasonic irradiation

In this paper, we present a green application for the synthesis of novel pyridine derivatives 4a-f via one-pot, multicomponent reaction (MCRs) of some aromatic aldehydes 1a-f with malononitrile (2) and N-(4-acetylphenyl)-4-methylbenzenesulfonamide (3) in the presence of ammonium acetate using ultrasonic irradiation (U.S) in an aqueous solvent H2O:EtOH (2:1). The structures of all synthesized pyridines 4a-f were confirmed via elemental analysis and different spectroscopic techniques. This application has many advantages such as avoiding hazardous solvents, excellent yields, inexpensive, simple application, in addition to obtain pure compounds. The anti-inflammatory activity of the newly compounds was examined with the reference drug Ibuprofen. The obtained results showed that most derivatives are promising anti-inflammatory activates. Moreover, compound 4b exhibits the most anti-inflammatory activity with a percentage of inhibition with 51.67% compared with Ibuprofen 53.96%. Furthermore, the newly compounds were studied in their molecular docking simulations against the enzyme Human Cyclooxygenase-2, with Tolfenamic Acid as a reference ligand (PDB ID: 5IKT). Compound 4b demonstrated a robust binding affinity with the target protein 5ikt, evidenced by its binding affinity score of - 11.16 kcal/mol, which is the highest among the studied compounds.

New Prospective Insecticidal Agents Based on N-(arylcarbamothioyl)arylmide Derivatives Against Spodoptera frugiperda: Design, Synthesis, Toxicological, Biological, Biomedical Studies and Antibacterial Activity

In this work, a novel series of N-(arylcarbamothioyl)arylmide) 2-11 were synthesized by treating One-Pot three-multicomponent of Aroyl chloride, ammonium isothiocyanate and amine compounds under refluxing conditions. Using spectroscopic methods, the chemical structure of the novelty developed compounds were investigated. After five days, the proposed derivatives' insecticidal bioassay was assessed using the median lethal concentration (LC50) against the second & fourth larvae of Spodoptera frugiperda as toxicity agents. The findings showed that, to varying degrees, every tested substance exerted insecticidal effects on S. frugiperda larvae in both of their instars. Compound 9 was the most poisonous of them all, having an LC50 against larvae in their second and fourth instars of 60.45 and 123.21 mg/L, respectively. Additionally, a few biological and biochemical characteristics of the substances that were generated in a lab setting were also looked at. Furthermore, this work discusses how to discover novel compounds that may one day be employed as insecticidal agents. Finally, all the designed components were monitored for their antibacterial effectiveness toward both Gram-positive & Gram-negative bacteria.

Pyridine Derivatives as Insecticides: Part 6. Design, Synthesis, Molecular Docking, and Insecticidal Activity of 3-(Substituted)methylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles Toward Aphis gossypii (Glover, 1887)

Three new series of 3-(substituted)methylthio-4-cyano-5,6,7,8-tetrahydroisoquinolines were designed and synthesized starting from readily available materials, 7-acetyl-4-cyano-1,6-dimethyl-6-hydroxy-8-(4-pyridyl, 3-pyridyl, phenyl, 4-methoxyphenyl, or 4-chlorophenyl)-5,6,7,8-tetrahydrosoquinoline-3(2H)-thiones 2a-e in high yields and very pure states. Thus, compounds 2a-e were reacted with some chloro reagents, namely, N-aryl-2-chloroacetamides 3a-f and N-(naphthalen-2-yl)-2-chloroacetamide (3g) under mild basic conditions to give the first two series of the target compounds, 3-(N-aryl)carbamoylmethylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles 4a-l and 5a-e, respectively. Reaction of compounds 2d,e with ethyl chloroacetate under the same conditions gave the other series, 3-ethoxycarbonyl-methylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles 6d,e. Structural formulas of all of the new compounds were elucidated and confirmed by elemental and spectral analyses. The insecticidal activity of all synthesized 5,6,7,8-tetrahydrosoquinolines toward the nymphs and adults of Aphis gossypii were screened. The results revealed the promising insecticidal activity of some tested compounds. Moreover, the structure-activity relationships as well as molecular docking of some representative compounds were evaluated.

Pyridine Derivatives as Insecticides. Part 5. New Thieno[2,3-b]pyridines and Pyrazolo[3,4-b]pyridines Containing Mainly Ethyl Nicotinate Scaffold and Their Insecticidal Activity toward Aphis gossypii (Glover,1887)

Ethyl 5-cyano-1,6-dihydro-2-methyl-4-(2'-thienyl)-6-thioxonicotinate (A) was synthesized and reacted with ethyl chloroacetate in the presence of sodium acetate or sodium carbonate to give ethyl 5-cyano-6-((2-ethoxy-2-oxoethyl)thio)-2-methyl-4-(2'-thienyl)nicotinate (1a) or its isomeric thieno[2,3-b]pyridine 2a. 3-Aminothieno[2,3-b]pyridine-2-carboxamide 2b was also synthesized by the reaction of A with 2-chloroacetamide. The reaction of 1a with hydrazine hydrate in boiling ethanol gave acethydrazide 3. Heating ester 1a with hydrazine hydrate under neat conditions afforded 3-amino-1H-pyrazolo[3,4-b]pyridine 10. Compounds 2b, 3, and 10 were used as precursors for synthesizing other new thieno[2,3-b]pyridines and pyrazolo[3,4-b]pyridines containing mainly the ethyl nicotinate scaffold. Structures of all new compounds were confirmed by elemental and spectral analyses. Most of the obtained compounds were evaluated for their insecticidal activity toward the nymphs and adults of Aphis gossypii (Glover,1887). Some compounds such as 4, 9b, and 9c showed promising results. The effect of some sublethal concentrations, less than LC50, of compounds 4, 9b, and 9c on the examined Aphis was subjected to a further study. The results demonstrated that exposure of A. gossypii nymphs to sublethal concentrations of compounds 4, 9b, and 9c had noticeable effects on their biological parameters, i.e., nymphal instar duration, generation time, and adult longevity. The highest concentration C1 of all three compounds increased the nymphal instar duration and generation time and decreased adult longevity and vice versa.

Novel Aryl Thioamides Derivatives as Insect Growth Regulators Analogues against Spodoptera littoralis (Lepidoptera: Noctuidae): Design, Synthesis, Insecticidal Activity and Biochemical Impacts

A significant reason for developing innovative insecticidal active agents is the exponential rise in resistance to traditional chemical pesticides. Exploring new classes of insecticidal compounds with distinct mechanisms of action is one way to address this difficulty. So that, novel aryl thioamides derivatives 3-15 has been synthesized viaone-pot, three-component reaction of aroyl chloride, ammonium thiocyanate, and aromatic amines in dry acetone. The newly synthesized compounds' structures were validated by various spectroscopic methods, including elemental analysis, 1H-NMR, 13C NMR, and infrared spectroscopy. Under laboratory circumstances, the synthesized compounds showed good and broad-spectrum insecticidal activities toward S. littorali. When compared to other synthetic target compounds, 2,4-dichloro-N-[(3-fluorophenyl)carbamothioyl]benzamide 11, 2,4-dichloro-N-[(3-fluorophenyl)carbamothioyl]benzenecarbothioamide 13 showed good insecticidal activity, with 46.33 mg/L and LC50 values of 49.25 mg/L for 2nd instar larvae. Furthermore, the compound 3 was the least toxic in controlling the second and fourth instar larvae of S. littoralis on tomato leaves. Additionally, several histopathological and biochemical features of the some synthesized compounds under laboratory circumstances were also examined.

Exploration of Some Heterocyclic Compounds Containing Trifluoromethylpyridine Scaffold as Insecticides Toward Aphis gossypii Insects

Five types of heterocyclic compounds containing trifloromethylpyridine scaffold namely; 3-cyano-2-(N-phenyl)carbamoylmethylthio-6-(thiophen-2-yl)-4-trifluoromethyl-pyridine (6a), thieno[2,3-b]pyridines 3-5 and 7a-c, pyrido[3',2':4,5]thieno[3,2-d] pyrimidines 8-13 and 15a-c, pyrido[3',2':4,5]thieno[3,2-d][1,2,3]triazines 16a,b, and 9-(thiophen-2-yl)-7-(trifluoromethyl) pyrido [3',2':4,5]thieno[2,3-e][1,2,4]triazolo[1,5-c]pyrimidine (14) were synthesized in excellent yields and very pure state. The structures of these compounds were confirmed by elemental and spectral analyses. Most of the synthesized compounds were evaluated as insecticidal agents toward Aphis gossypii insects and promising results obtained. Among all tested compounds, only 6, 7a, 7c and 15c being the most potent compounds against nymphs and adults of Aphis gossypii and their activities are nearly to that of acetamiprid as a reference. The effect of 6a compounds 7a, 7c and 15c on the Aphis digestive system from histological point of view was also included.

Thiadiazole/Thiadiazine Derivatives as Insecticidal Agent: Design, Synthesis, and Biological Assessment of 1,3,4-(Thiadiazine/Thiadiazole)-Benzenesulfonamide Derivatives as IGRs Analogues against Spodoptera littoralis

In keeping with our investigation, a simple and practical synthesis of novel heterocyclic compounds with a sulfamoyl moiety that can be employed as insecticidal agents was reported. The compound 2-hydrazinyl-N-(4-sulfamoylphenyl)-2-thioxoacetamide 1 was coupled smoothly with triethylorthoformate or a variety of halo compounds, namely phenacyl chloride, chloroacetyl chloride, chloroacetaldehyde, chloroacetone, 1,3-dichloropropane, 1,2-dichloroethane, ethyl chloroformate, 2,3-dichloro-1,4-naphthoquinone, and chloroanil respectively, which afforded the 1,3,4-thiadiazole and 1,3,4-thiadiazine derivatives. The new products structure was determined using elemental and spectral analysis. Under laboratory conditions, the biological and toxicological effects of the synthetic compounds were also evaluated as insecticides against Spodoptera littoralis (Boisd.). Compounds 3 and 5 had LC50 values of 6.42 and 6.90 mg/L, respectively. The investigated compounds (from 2 to 11) had been undergoing molecular docking investigation for prediction of the optimal arrangement and strength of binding between the ligand (herein, the investigated compounds (from 2 to 11)) and a receptor (herein, the 2CH5) molecule. The binding affinity within docking score (S, kcal/mol) ranged between -8.23 (for compound 5), -8.12 (for compound 3) and -8.03 (for compound 9) to -6.01 (for compound 8). These compounds were shown to have a variety of binding interactions within the 2CH5 active site, as evidenced by protein-ligand docking configurations. This study gives evidence that those compounds have 2CH5-inhibitory capabilities and hence may be used for 2CH5-targeting development. Furthermore, the three top-ranked compounds (5, 3, and 9) and the standard buprofezin were subjected to density functional theory (DFT) analysis. The highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy difference (ΔE) of compounds 5, 3, and 9 was found to be comparable to that of buprofezin. These findings highlighted the potential and relevance of charge transfer at the molecular level.

One-Pot, Four-Component Reaction for the Design, Synthesis, and SAR Studies of Novel Pyridines for Insecticidal Bioefficacy Screening against Cowpea Aphid (Aphis craccivora)

In this paper, novel pyridines 2-8 were designed and synthesized via the one-pot, four-component reaction of 2-formylphenyl 4-tolylsulfonate with malononitrile, ammonium acetate, and phenols or 2-thioxo-1,3-thiazolidin-4-one or 6-aminopyrimidine-2,4(1H,3H)-dione under microwave irradiation in an aqueous solution of water and ethanol (1:1 ratio). The structures of new pyridines 2-8 were elucidated by elemental and spectral analyses such as IR, 1H NMR, and 13CNMR. This application has many advantages, such as having easy workup, eco-friendliness, reaction time being short (6-13 min), high production (94-98%), inexpensiveness, and avoiding the use of harmful solvents. Moreover, all compounds have been investigated as insecticidal agents against cowpea aphid (Aphis craccivora) insects, and the toxicity effect was studied, followed by the structure-activity relationship. From the LC50 values, it has been found that compounds 7 and 8 were excellent and promising insecticidal agents, with LC50 values of 0.05 and 0.09 ppm against nymphs and 0.93 and 1.01 ppm against adults of cowpea aphid. Furthermore, the obtained results indicated that compounds 2-8 can be applied as insecticidal agents for the control of cowpea aphids and to protect agricultural crops from this destructive pest, which effects crop production and causes major economic damage.

Synthesis and Insecticidal Evaluation of 3,5-Dicyanopyridines Against Cotton Aphids via Microwave-Assisted Multicomponent Reactions

Certain 2-amino-6-alkoxy-4-arylpyridine-3,5-dicyanide 1a-e were prepared via a straightforward process using microwave technology rather than conventional methods. This involved reaction of arylidenemalononitrile thru propanedinitrile in the occurrence of sodium alkoxide under MW. While, their positional isomer 4-amino-6-alkoxy-2-arylpyridine-3,5-dicyanide 3a-j have been separated from the reaction of aryl aldehydes with 2-aminoprop-1-ene-1,1,3-tricarbonitrile 2 in the presence of sodium alkoxide using microwave technic. Furthermore, the insecticidal properties of all synthesized compounds were observed with respect to Cotton aphid nymphs and adults. Neonicotinoid pesticides are indicated as the most effective pesticides toward aphids and many other pests. Many insecticides are discovered as novelties. As a result, several pyridine compounds were chemical method synthesized to serve as equivalents of neonicotinoids, a broad class of insecticides. With LC50 value of 0.03 mg/L, components 3g exhibit the highest insecticidal bioactivity. This work discusses how to find new chemicals that could be used as insecticidal agents in the future.

Green synthesis and bioefficacy screening of new insect growth regulators as eco-friendly insecticides against the cotton mealybug Phenacoccus solenopsis

Overcoming or reducing the majority of difficulties caused by the use of common pesticides requires the use of developed, secure, unique and selective organic compounds. Due to their clear mechanism of action on pests and lower poisonousness towards vertebrates than conventional insecticides, juvenile hormone analogues as an example of insect growth regulators appear promising. Thus, a unique set of pure insect growth regulators has been synthesized. The structure of these synthesized compounds, which were related to the most well-known insect growth regulator insecticides, was confirmed by elemental and contemporary spectroscopic investigations (IR, UV, 1 H-NMR, 13 C NMR, and Dept 135 spectrum). Under laboratory conditions, the effectiveness of a chemically newly synthesized products was tested against the cotton mealybug, Phenacoccus solenopsis, and compared with Fenoxycarb as a reference insecticide. Compound 7 was discovered to be more effective than the other synthetic compounds, with LC50 values of 0.907 mg/L for adult female P. solenopsis and 0.377 mg/L for third instar nymphs. Furthermore, this results concluded that the adult female's stage of P. solenopsis was less sensitive to the checked treatments as matched to the third instar nymphs.