Discovery and Biological Evaluation of 3-(1,2,3-Thiadiazol-5-yl)-1-arylimidazolidine-2,4-diones as Potential Plant Growth Regulators

A simple method for the synthesis of 1,2,3-thiadiazol-5-ylimidazolidine-2,4-dionesstructural analogues of the plant growth regulator thidiazuronhas been developed. The effects of 8 new compounds, as well as thidiazuron (<b>TDZ</b>), 6-benzylaminopurine (<b>6-BAP</b>), and indole-3-acetic acid (<b>IAA</b>), on cucumber seed germination and seedling morphology have been studied. Two 1,2,3-thiadiazol-5-ylimidazolidine-2,4-diones, <b>A1</b> and <b>B1</b>, were discovered to exhibit growth-regulating effects similar to those of <b>TDZ</b> and considered promising candidates for further investigation. At a concentration of 5 mg/L, these compounds significantly inhibited the growth of lateral roots and retarded the elongation of the primary root, without negatively affecting the vegetative parts of the seedlings. Evaluation of the fungicidal activity of the 1,2,3-thiadiazol-5-ylimidazolidine-2,4-diones at a concentration of 50 μg/mL against 8 strains of phytopathogenic fungi revealed 4 compounds with moderate activity (<i>I</i> > 50%) against <i>Alternaria solani</i> and 2 compounds against <i>Plenodomus lingam</i>.