Tony K. Trullinger

Synthesis and Biological Activity of a New Class of Insecticides: the N-(5-Aryl-1,3,4-thiadiazol-2-yl)amides.

BACKGROUND Optimization studies on a high-throughput screening (HTS) hit led to the discovery of a series of N-(6-arylpyridazin-3-yl)amides with insecticidal activity. It was hypothesized that the isosteric replacement of the pyridazine ring with a 1,3,4-thiadiazole ring could lead to more potent biological activity and/or a broader sap-feeding pest spectrum. The resulting N-(5-aryl-1,3,4-thiadiazol-2-yl)amides were explored as a new class of insecticides. RESULTS Several methods for 2-amino-1,3,4-thiadiazole synthesis were used for the preparation of key synthetic intermediates. Subsequent coupling to variously substituted carboxylic acid building blocks furnished the final targets, which were tested for insecticidal activity against susceptible strains of Aphis gossypii (Glover) (cotton aphid), Myzus persicae (Sulzer) (green peach aphid) and Bemisia tabaci (Gennadius) (sweetpotato whitefly). CONCLUSION Structure-activity relationship (SAR) studies on both the amide tail and the aryl A-ring of novel N-(5-aryl-1,3,4-thiadiazol-2-yl)amides led to a new class of insecticidal molecules active against sap-feeding insect pests.

Synthesis and Biological Potency of Anilino‐Triazine Insecticides

BACKGROUND An insecticide screening effort identified N-(4-bromophenyl)-4,6-bis(2,2,2-trifluoroethoxy)-1,3,5-triazine-2-amine as having weak potency against two lepidopteran species, Helicoverpa zea and Spodoptera exigua. A structure-activity relationship study about the trifluoroethoxy substituents and the aniline of this compound was carried out in an effort to improve insecticidal potency. RESULTS Initially, a series of analogs bearing various substituents on the aniline were prepared, and the insecticidal potency was evaluated against H. zea and S. exigua in greenhouse diet feeding assays. The results showed that electron-withdrawing substituents, such as Cl, Br and CF3 , were preferred over electron-donating substituents, such as methoxy, and that potency was significantly better when the substituent was in the para-position. Additional investigations showed that bis(anilino)trifluoroethoxytriazines were more potent. Replacement of the remaining trifluoroethyl group in the bis(anilino)triazine series with an alkyl amine lead to compounds of equal or superior efficacy. CONCLUSION The work presented showed that electron-withdrawing substituents in the para-position of the aniline ring of the initial hit delivered the best levels of insecticidal potency against the two insect species tested. Further investigations showed that potency could be improved by replacing one of the two trifluoroethoxy groups with additional 4-substituted aniline. This level of potency was maintained or further improved when the remaining trifluoroethoxy was replaced with a substituted amine.