N‐(pyrid‐3‐yl)thioureas and derivatives as acaricides. II. Quantitative structure‐activity relationships and chemodynamic behaviour

Abstract

The biological activity of a series of N‐(pyrid‐3‐yl)thioureas and ‐carbodiimides, analogues of the insecticide/acaricide diafenthiuron, towards the carmine spider mite (Tetranychus cinnabarinus Boisd.) and the two‐spotted spider mite (T. urticae Koch) was analysed using QSAR methodology. A canonical correlation analysis allowed for the establishment of a prediction model and the identification of outliers within that model. The chemodynamic behaviour of certain compounds in the two series, including these outliers, determined by using photochemical experiments in the laboratory as well as in the glasshouse, was shown to be responsible for anomalous results obtained in the biological tests. It was found from the above study that the biological activity towards both spider mite species is extremely sensitive to the kinetics of formation of the carbodiimides from the corresponding thioureas and to the photostability of the former. The results obtained with a thiourea which underwent no appreciable photochemical transformation into the corresponding carbodiimide supported the hypothesis that the thioureas are also in‐vivo propesticides of the acaricidal carbodiimides.

Photodegradation of diafenthiuron in water

“…When the concentration ratios of CGA‐140 408 and CGA‐177 960 in Figs 4(A) and (B) were compared, relatively high levels of CGA‐177 960 indicated that diafenthiuron could be transformed to CGA‐177 960 directly or via reactive intermediates, which agreed with previous suggestions 6. 7, 15, 16…”

“…3 Studies also suggest that diafenthiuron is a pro‐insecticide and its activity correlates with its biological and chemical transformation rates into the corresponding carbodiimide 4–6. One study concluded that the acaricidal activity of diafenthiuron and its analogues highly correlated with the photochemical formation of carbodiimide derivatives 7…”

QSAR of 2,4-diphenyl-1,3-oxazolines for ovicidal activity against the two-spotted spider mite Tetranychus urticae

“…QSAR analyses of other acaricides were also executed, and it was shown that hydrophobicity is an important physicochemical property for activity [29][30][31][32][33] . For instance, acaricidal activities of pyrethroids 31) and alkanesulfonates 29) were parabolically correlated with hydrophobicity parameters such as p and log kЈ.…”

A New Class of Glucosyl Thioureas: Synthesis and Larvicidal Activities

“…We believe that chitin synthase probably follows a “like uses like” principle, and misuses these “anti-chitin structure” chemicals as chitin precursors for chitin synthesis and this leads to the discontinuation of chitin synthesis. The thiourea group is used as a functional group for some pesticides to achieve highly efficient larvicidal activity, for instance, diafenthiuron [45,46,47,48] containing one thiourea moiety shows a strong larvicidal ability toward mites (Figure 3). With this in mind, inclusion of a thiourea group is a feature of the designed molecules presented in this paper.…”