Synthesis and Insecticidal Activity of New Benzyl- and Indanyl-Oxazolines, Thiazolines and Alkoxy-Alkyl-Imidazolines

How active ingredient localisation in plant tissues determines the targeted pest spectrum of different chemistries

“…IM belongs to the same chemistry type as OX, acting on octopamine receptors . IM is trapped to a greater extent than OX in vacuoles, but there is a negligible amount in the apoplast (the lowest of all test compounds), and it is mostly adsorbed inside the cytosol.…”

Pro‐insecticidal approach towards increasing in planta activity

“…It has been hypothesized that the insecticidal efficacy of oxazoline compounds, such as 1, could be limited as they may be trapped in plant vacuoles owing to their basicity (Fig. ) . In addition, the specialized feeding behavior of aphids and whitefly, which avoids disrupting plant cells to target phloem and xylem, may limit their exposure to the toxicants that are trapped in the cellular vacuoles .…”

“…The predicted p K a for 4 (12.85) was very basic and therefore possibly subject to vacuole trapping. It was further postulated that reducing the polarity and basicity might not only reduce the potential for vacuole trapping but also allow for greater penetration through the waxy cuticle of a leaf surface …”

“…The known adrenergic agent clonidine was shown to have insecticidal activity against sucking pests, and literature analogs have also been reported with aphicidal activity . This insecticidal activity does not translate to cotton, so a prodrug approach was attempted to increase translaminar movement across the leaf cuticle.…”

“…Structures in open‐chain form were of greater interest because they contain more positions for substitution and therefore have greater potential for structural diversity and structural scaffold hopping. In addition, open‐chain structures were hypothesized to have more desirable physical properties than other putative octopaminergic insecticides, potentially allowing greater systemic movement through the plant . Because certain oxazoline‐containing analogs were suspected of vacuole entrapment, owing to their basic pH, and it was speculated that open‐chain forms may suffer a similar fate on account of their basicity, a prodrug analog with improved physical properties based on 4 was pursued (Scheme ) .…”