Synthesis Herbicide and Growth Regulating Activity of Some N Alkyl and Phenyl-N'-Pyridylthioureas

Abstract

Thirty N-alkyl and phenyl-N'-pyridylthioureas were synthesized. The herbicidal and growth regulating activity of some N-alkyl and phenyl-N'-pyridylthioureas was studied, using wheat cv. Sadovo 1 and cucumber cv. Bistrenski. The sequence of herbicidal activity was found regarding the 2 test plants with respect to both substituents at the 1st N atom and the pyridyl residuum of the 2nd N atom. Diuron occupied the 1st rank in the sequences of both test plants. Highest selective herbicidal activity was observed in the ethyl derivatives of the pyridylthioureas, on the one side, and in the .alpha.-(4-methyl) pyridyl derivatives of alkyl and phenylthioureas. Higher selective herbicidal activity than the urea herbicidal Diuron (PSA - 1.00:2.43) was manifested by the substances N-allyl-N'-.alpha.-(3-methylpyridyl) thiourea (PSA = 1.00:3.53), N-methyl-N'-.alpha.-(6-methylpyridyl) thiourea (PSA = 1.00:2.84) and others, which could be effective herbicides in the control of monocotyledonous weeds. The tested N-alkyl and phenyl-N'-pyridylthioureas manifest their very high stimulating activity with regard to wheat. Particularly high stimulating activity was observed in the following substances: N-ethyl-N'-.alpha.-pyridylthiourea (176.3% at a concentration of 10-5 and 181.6% at 10-6 M concentration, N-phenyl-N'-.alpha.-pyridylthiourea (174.7% at 10-6 M), N-methyl-N'-.alpha.-pyridylthiourea (170.5% at 10-5 M and 167.0% at 10-6 M) and N-phenyl-N'-.alpha.-(4-methylpyridyl) thiourea (159.4% at 10-6 M).