SYNTHESIS AND STRUCTURE-ACTIVITY-RELATIONSHIPS OF 1-ARYL-4-SUBSTITUTED-1,4-DIHYDRO-5H-TETRAZOL-5-ONES, A NOVEL CLASS OF PREEMERGENCE AND POSTEMERGENCE HERBICIDES

1-Aryl-4-substituted-1,4-dihydro-5H-tetrazol-5-ones (I) represent a new class of herbicides, which, when applied pre- or post-emergence in the presence of light, control several agriculturally important weed species. Forty-eight analogues have been synthesized and their herbicidal activities determined in order to study structure-activity relationships. In general, these compounds demonstrated: (1) optimum herbicidal activity when the 4-substituent on the tetrazole ring was-CH2CH2CH2F, and the aryl group 2-fluoro-4-chloro-5-substituted phenyl; (2) optimum herbicidal activity over a broad spectrum of grass and broad leaf weeds, with marginal crop selectivity when the C5 substituent on the phenyl group was -OCH2C = CH; and (3) a high degree of selectivity on several major crops and primarily broadleaf weed control when this substituent was - NHSO2CH2CH3.