Synthesis of inventive biphenyl and azabiphenyl derivatives as potential insecticidal agents against the cotton leafworm, Spodoptera littoralis

Abstract

The emergence of pest resistance of Spodoptera littoralis (order; Lepidoptera, family; Noctuidae) towards the large scale of different classes of insecticides necessitates the development of some new poly-functionalized biphenyl and azabiphenyl with highly anticipated insecticidal bioresponse. Four new biphenyl carboxamidines 4a–d and four aza-analogue picolinamidine derivatives 8a–d were designed and prepared via the treatment of their corresponding carbonitriles with lithium-bis trimethylsilylamide [LiN(TMS)2], followed by hydrolysis with hydrogen chloride. Furthermore, these compounds were elucidated by spectral data, and their toxicity and insecticidal activity were screened against Spodoptera littoralis. Whereby, toxicological and biochemical aspects of the inventively synthesized biphenyl and azabiphenyl derivatives against the cotton leafworm, Spodoptera littoralis were inspected. As regards the indomitable LC50 and LC90 values, biphenyl and aza-analogues 8d, 8a, 4b, and 8b, revealed the furthermost forceful toxic effects with LC50 values of 113.860, 146.265, 216.624, and 289.879 ppm, respectively. Whereby, their LC90 values are 1235.108, 1679.044, 2656.296, and 3381.256 ppm, respectively, and toxicity index being 22.31%, 17.36%, 11.72%, and 8.76%, respectively, comparing with the already recommended, methomyl insecticide, lannate 90% SP (LC50, 25.396 and LC90, 57.860 and toxicity index, 100%). Additionally, electrochemical parameters via DFT studies were carried out for demonstrating and elucidation of structure–activity relationship (SAR) according to highly motived compounds, descriptors, and the in vivo insecticidal activities. Graphical Abstract