Design, synthesis, and biological evaluation of 2-benzylpyrroles and 2-benzoylpyrroles based on structures of insecticidal chlorfenapyr and natural pyrrolomycins

Based on structures of insecticidal chlorfenapyr and antibiotic natural pyrrolomycins, a series of new 2-benzylpyrroles and 2-benzoylpyrroles (with or without ethoxymethyl group on the nitrogen of pyrrole) were designed and synthesized. These compounds or their parent compounds possess weak acidity and high lipophilicity, the two characteristic properties for uncouplers of oxidative phosphorylation; therefore, they are expected to have insecticidal and acaricidal activity. The bioassay result verified that both 2-benzylpyrroles 17 and 2-benzoylpyrroles 19 had varied degrees of insecticidal activity against oriental armyworm depending on the substituents on the benzene ring, but they did not give any acaricidal activity. Conversely, most N-alkylated compounds 18 and 20 exhibited both insecticidal activity and acaricidal activity, of which compound 18i [4-bromo-2-(2,4-dichlorobenzyl)-1-(ethoxymethyl) -5-(trifluoromethyl) - 1-pyrrole-3-carbonitrile] has IC as low as 10-20 mg L on both activities.