Abstract
3-Arylimino-5, 6-dihydro-3H-thiazolo[2, 3-c][1, 2, 4]thiadiazoles (III) were synthesized by oxidative ring closure of 3-(N-arylthiocarbamoyl)-2-iminothiazolidines. And this synthetic method was successfully applied to the synthesis of other 3-arylimino-1, 2, 4-thiadiazolo-fused heterocyclic systems. In foliage treatment this series of compounds exhibited fast-acting and light dependent herbicidal actions which are similar to those of diphenyl ethers and tetrahydrophthalimides. The potency of the herbicidal activity was found to depend on both the substituents on the benzene ring and heterocyclic moieties. Substituent effect of the benzene ring on the herbicidal activity was similar to that of tetrahydrophthalimides. Acid-catalyzed hydrolysis, base-catalyzed hydrolysis and photo-decomposition of III were also studied. Several products were isolated and their structures were determined. However any 1, 2, 4-triazole-3-thione derivative, which is known to exhibit herbicidal activity similar to that of tetrahydrophthalimides, was not isolated. Under such chemical conditions, the rearrangement of 3-arylimino-1, 2, 4-thiadiazolo-fused ring systems to form 2-aryl-3-thio-1, 2, 4-triazolo-fused ring systems seemed to be difficult.
