Acaricides Containing Halogens

A survey of the new ISO provisionally approved active ingredients for modern crop protection available in the time frame 2000-2006 (February) shows that around 74% of them are halogen-substituted (Br, I < Cl, Cl/F < F). In this time, approximately four times more halogen-containing insecticides acaricides and fungicides, as well as two times more herbicides, were approved than non-halogenated active ingredients. 

Up to now, eleven BPUs have been commercialized or are on late-stage development as chitin synthesis inhibitors that contain both fluorine (2-9) and chlorine (1-3) atoms. Early studies on structure-activity relationships (SAR) of BPUs reflected little scope for variation of substituents at the N-benzoyl moiety. Only derivatives with at least one ortho substituent retained insecticidal activity. Such an ortho-substituent (R ) can be methyl, OCF3, or OC2F5 and lead to active derivatives. However, all commercialized products have ortho-halogen substituents and the insecticidal or acaricidal activity generally follows in the order (Hal, Ri) 2,6-F2 > 2-Cl, 6H > 2,6-Cl2 > 2-F, 6H (Fig. 35.10, Table 35.7). 

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