Synthesis and herbicidal properties of substituted 1,4-dihydro-1,2,4-benzotriazines

A series of 1,4-dihydro-1,2,4-benzotriazines exhibits slight to moderate herbicidal activity in preemergence and postemergence tests. Postemergence applications of these benzotriazines at 4 lb/acre provided good control of large crabgrass, foxtail millet, redroot pigweed, wild mustard, and tomato, but no selectivity was observed among the various plant species. At 4 lb/acre preemergence, corn, wheat, rice, cotton, and soybean show tolerance, while large crabgrass, foxtail millet, redroot pigweed, common lambsquarters, velvetleaf, and jimsonweed were killed or severely injured. A total of 36 analogues was synthesized, and their herbicidal activities were determined to examine the structure-activity relationships. In general, we found that, among the variations investigated, cyano substitution on the benzo portion, small alkyl at the 1-position, and hydrogens at the 3- and 4-positions led to the most active herbicides