Microwave-Assisted Synthesis and Insecticidal Evaluation of Novel 2H-Pyran-3-Carbonitrile Derivatives Against...

The growing resistance to conventional chemical pesticides has become a key driver in the development of new insecticidal agents. Examining new classes of insecticidal compounds with distinct modes of action is one way to meet this problem. Thus, a novel series of 2H-pyran-3-carbonitrile derivatives 4a-h was synthesized via one-pot multicomponent reaction using microwave irradiation. The structure of all compounds was confirmed via IR, ¹H NMR, ¹³C NMR spectra, and elemental analysis 4a-h. Simplicity, high yields (86%-94%), rapid reaction times (7-12 min), eco-friendliness, and avoidance of any toxic solvents are some advantages of this approach. Under laboratory conditions, all synthesized compounds were evaluated as insecticidal agents. Bioassays demonstrated significant larvicidal activity against the second- and fourth-instar larvae of Spodoptera littoralis. Among them, 4-(3-bromo-4-hydroxyphenyl)-6-(3-chlorophenyl)-2-oxo-2H-pyran-3-carbonitrile (4f) exhibited the most potent insecticidal activity, with LC₅₀ values of 118.7 mg/L for the second-instar larvae and 293.2 mg/L for the fourth-instar larvae.