Synthesis, stability and insecticidal activity of 2‐arylstilbenes

BACKGROUND: A chemical scaffold‐hopping approach from known 3‐hydroxyl‐3‐methylglutaryl‐CoA (HMG‐CoA) reductase inhibitors identified (E/Z)‐2‐arylstilbenes as novel insecticidal hits against two lepidopteran species, Spodoptera exigua and Trichoplusia ni. A structure–activity relationship (SAR) study of the aryl substituents and the E/Z conformations was carried out in an effort to improve insecticidal potency. RESULTS: A series of (E/Z)‐2‐arylstilbenes was prepared and separated to evaluate their insecticidal potency against lepidopterous species in diet‐feeding assays. The results showed that the (Z)‐2‐arylstilbenes were more active than their corresponding (E)‐isomers, and a stereoselective synthesis was utilized to expand the SAR of the (Z)‐2‐arylstilbenes. (Z)‐4'‐Fluoro‐3′‐methyl‐2‐(2,4‐difluorostyryl)‐4‐fluoro‐5‐methoxy‐1,1′‐biphenyl was the most potent analog in this study with strong activity against S. exigua, T. ni, Helicoverpa zea, Plutella xylostella and Pseudoplusia includens. CONCLUSION: The (Z)‐2‐arylstilbenes were found to have strong insecticidal potency against five lepidopteran species. Ultimately, synthetic efforts could not improve insecticidal potency to commercial levels, and a lack of UV stability led to efforts being discontinued. © 2019 Society of Chemical Industry