Synthesis and Insecticidal Assessment of Some Innovative Heterocycles Incorporating a Pyrazole Moiety

Abstract

The compound 1,3-diphenyl-1H-pyrazole-4-carbaldehyde (1) was utilized as a fundamental component in the synthesis of novel N-phenyl pyrazole derivatives. Substituted N-phenyl pyrazole compounds including 2-cyano-3-(1,3-diphenyl-1H-pyrazol-4-yl)-N-Substituted-acrylamide derivatives (4a–h), 4-(hydrazineylidenemethyl)-1,3-diphenyl-1H-pyrazole (6) and 2-cyano-N'-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)-acetohydrazide (11) were obtained in moderate yields through the reaction of 1 with 2-cyano-N-substituted acetamide derivatives 3a–h, hydrazine hydrate, and cyanoacetohydrazide under basic-catalyzed conditions, respectively. Moreover, hydrazinyl-pyarzole 6 reacted with 4,5,6,7-tetrabromoisobenzofuran-1,3-dione (7) to afford 4,5,6,7-tetrabromo-2-(((1,3-diphenyl-1H-pyrazol-4-yl)methylene)amino)- isoindoline-1,3-dione (8). Furthermore, pyrazoloacetohydrazide 11 is condensed with salicylaldehyde derivatives 12a–e to give pyrazolochromene carbohydrazide derivatives 13a–e. Also, acetohydrazide 11 refluxed with N, N-dimethylformamide dimethyl acetal to produce 2-cyano-3-(dimethylamino)-N'-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)acrylohydrazide (15), which upon exposure to acidic conditions underwent cyclization to form 4-((dimethylamino)methylene)-6-(1,3-diphenyl-1H-pyrazol-4-yl)pyridazine-3,5(4H,6H)-dione (16). The newly synthesized compounds were identified and confirmed using elemental and spectral data analyses as IR, MS, ¹H NMR, ¹³C NMR, and 2D NMR analysis (H-H COSY, HSQC, HMBC, and NOSEY), Also, DFT studies were done to prove the geometrical optimization and spatial distributions orbitals of compounds 4a and 11. The toxicity of N-phenylpyrazole compounds was tested against the corn leaf aphid (Rhopalosiphum maidis) and the mealy plum aphid (Hyalopterus pruni). Compounds 4c, 13c, and 13d were found to be the most potent to control the two insects compared with acetamiprid 20% SP recommended by the Ministry of Agriculture. The biochemical investigation of insects was studied to the most effective compounds on insects as well, and the toxicity of compounds 4c, 13c, and 13d was studied on the predators (Hippodamia variegata, Cydonia vicina isis, Cydonia vicina nilotica, and 4^th instar larvae H. variegata) under laboratory conditions.