Synthesis and herbicidal activity of 1-aryl-5-halo-and 1-aryl-5-(trifluoromethyl)-1H-pyrazole-4-carboxamides
1990
Waldrep, T.W. | Beck, J.R. | Lynch, M.P. | Wright, F.L.
A series of 1-aryl-5-halo- and 1-aryl-5-(trifluoromethyl)-1H-pyrazole-4-carboxamides exhibit moderate to strong herbicidal activity in preemergence and postemergence tests. At 1/2 lb/acre, corn, rice, wheat, cotton, and soybean show tolerance, while large crabgrass, foxtail millet, common lambsquarters, redroot pigweed, wild mustard, velvetleaf, jimsonweed, and zinnia were killed or severely injured. A total of 83 5-halo analogues and 47 5-trifluoromethyl analogues were synthesized and their herbicidal activities determined in order to examine the structure-activity relationships. The order of activity at C-5 of the pyrazole ring was CF3 > Cl approximately equal to Br > I. The order of activity involving substitution on the carboxamide moiety was cyclopropyl approximately equal to methyl > dimethyl > ethyl > isopropyl. Substitution on the benzene ring did not result in any major increase in activity when compared with the corresponding phenyl analogue.
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