TRIAZOLINES .29. 1,5-DIARYL-DELTA(2)-1,2,3-TRIAZOLINES AS APHICIDES - MECHANISM OF ACTION VIA AZIRIDINE FORMATION

The aphicidal activity of 21 different 1,5-diphenyl-DELTA2-1,2,3-triazolines, conveniently prepared utilizing the catalytic effect of water on the 1,3-cyclo-addition of diazomethane to Schiff bases in aqueous dioxane, was evaluated. Triazolines bearing an o-Cl substituent on the C-phenyl, either alone (4) or in combination with a m- and/or a p-substituent on the N-phenyl (14, 15, 17 and 18), showed significant activity, with a combined m-, p- substitution on the N-phenyl the most effective (17 and 18). While an o-Cl substituent led to greater activity than an o-NO2 group, the introduction of an additional p-Cl substituent on the C-phenyl eliminated activity (21). The aphicidal activity of triazoline 18 was found to be dependent on the presence of UV light. Since fluorescent lighting used in the testing procedure contains UV light and since triazolines undergo photolysis when exposed to UV light to yield aziridines, it was logical to conclude that the aphicidal activity of the triazolines was, in fact, derived from the aziridines formed during the testing procedure. This mechanism of action was confirmed by preparing the aziridines 22, 23 and 24 corresponding to the active triazolines 14, 15 and 18, and showing that they possessed aphicidal activity equal to or better than that of the triazolines, and by the activity observed in several other structurally related aziridine analogues (25-28). Unlike aziridinyl phosphorous compounds, the aziridines described here are not mutagenic in the Ames assay and thus afford a safer class of pesticides.