Isomerization and Peroxidizing Phytotoxicity of Thiadiazolidine Herbicides

Abstract

Certain 5-(arylimino)-3,4-tetramethylene-1,3,4-thiadiazolidin-2-ones (thiadiazolidines) are peroxidizing bleaching herbicides which interrupt chlorophyll biosynthesis, inhibit the activity of protoporphyrinogen oxidase, lead to accumulation of protoporphyrin IX, and induce ethane formation in the light. The same effects are caused by their isomers, the 4-aryl-1,2-tetramethylene-l,2,4-triazolidin-3-one-5-thiones (triazolidines). Couples of thiadiazolidines and corresponding triazolidine isomers were synthesized. Thiadiazolidines with a 4-bromophenylimino, 4-chlorophenylimino, 4-chloro-2-methylphenylimino, 4-chloro- 2-fluorophenylimino, 4-chloro-2-fluoro-5-propargyloxyphenylimino and 4-chloro-2-fluoro- 5-isopropoxyphenylimino moiety were converted to the corresponding triazolidines both with Echinochloa seedlings or a spinach homogenate present, depending on the 5-arylimino moiety. The 5-[4-(chlorobenzyloxy)phenylimino]-3,4-tetramethylene-1,3,4-thiadiazolidin-2- one analogue did not convert to the corresponding triazolidine under both conditions. Thiadiazolidines as well as triazolidines having a 4-chloro-2-fluoro-5-methoxycarbonylmethylthiophenyl moiety were converted to an unidentified compound whose structure is assumed to be 4-(4-chloro-2-fluoro-5-carboxymethylthiophenyl)-1,2-tetramethylene-1,2,4- triazolidin-3-one-5-thione. Apparently, the general conversion mechanism is caused by enzymatic hydrolysis of thiadiazolidines to an unstable intermediate which rapidly and spontaneously changes to the corresponding triazolidine isomer.

Propesticides and their use as agrochemicals

“…The isomerisation in vivo of the isourazole proherbicide fluthiacet‐methyl (Appeal ® , 1999; Kumiai Chemical Industry Co., Ltd, Tokyo, Japan) in the plant by glutathione S ‐transferase (GST) resulted in the urazole derivative (Fig. ), which gives strong and selective post‐emergence herbicidal control of annual broadleaf weeds in cotton (10–15 g AI ha −1 ) and in maize/corn, turf and soybeans (5–10 g AI ha −1 ) …”

Weed Control, 2. Individual Herbicides

“…It is stable towards hydrolysis. Fluthiacet-methyl is produced by reaction of 1-[(2-fluoro-4-chloro-5-thiomethylacetate)phenylthiocarbamoyl]-2-methoxycarbonylhexahydropyridazine with methanolic potassium hydroxide, followed by treatment with trichloromethyl chloroformate [455].…”

Peroxidizing Phytotoxicities of 1, 2-Dialkyl-1, 2, 4-triazolidines and 3, 4-Dialkyl-1, 3, 4-thiadiazolidines

“…A similar tendency was observed with both the triazolidinediones (2, 5, 9, 12 and 15) and triazolidine-dithiones (4, 7, 11, 14 and 17). The order of Protox inhibition among the triazolidin-one-thiones, triazolidine-diones and triazolidine-dithiones is as follows: tetramethylene analogues (12, 13 and 14) > trimethylene analogues (9, 10 and 11) > pentamethylene analogues (15,16 It has been reported that maximum length and width of peroxidizing herbicides match closely with the full-length and one-half width of the protoporphyrinogen-IX molecule.18' 19) So, our objective was to find out a relationship between Protox inhibition and steric parameters, maximum length (L) and maximum width (W) between the N1-and N2-substituent in the most stable conformation (see Fig. 2), with respect to our triazolidin-onethione compounds (1, 3, 6, 8, 10, 13 and 16 n stands for number of data, r the correlation coefficient, s the standard deviation, respectively.…”