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.

Dihydropiperazine neonicotinoid compounds. Synthesis and insecticidal activity.

Syntheses of various isomeric dihydropiperazines can be approached successfully by taking advantage of the regioselective monothionation of their respective diones. Preparation of the precursor unsymmetrical N-substituted piperazinediones from readily available diamines is key to this selectivity. The dihydropiperazine ring system, as exemplified in 1-[(6-chloropyridin-3-yl)methyl]-4-methyl-3-oxopiperazin-2-ylidenecyanamide (4) and 1-[(2-chloro-1,3-thiazol-5-yl)methyl]-4-methyl-3-oxopiperazin-2-ylidenecyanamide (25), has been shown to be a suitable bioisosteric replacement for the imidazolidine ring system contained in neonicotinoid compounds.