The following work could bring new insights into the application of heterocyclic N, N′-substituted thiobenzamide derivatives as novel pesticides. Insect growth regulators such as chitin synthesis inhibitors seem promising because of their specific mode of action on insects and their lower toxicity against vertebrates than conventional insecticides. Thus, a novel series of thiobenzamide derivatives have been prepared in a pure state. The structure of these synthesized compounds which related to the most famous insect growth regulator insecticides, were confirmed by elemental and modern spectroscopic analyses (IR, UV, ¹HNMR and ₁₃CNMR). Toxicological and biochemical parameters of the synthesized compounds against the cotton leafworm, Spodoptera littoralis under laboratory conditions were also investigated. Regarding the determined LC₅₀ value for compound 2,4-Dichloro-N-[(2-methoxyphenyl)carbamothioyl]- benzamide 14 showed the most potent toxic effects than the other synthetic target compounds, with LC50 46.84 ppm of 2nd instar larvae and LC50 148.05of the 4th instar larvae.