Synthesis, bleaching activity, and germination promoting activity of 3,4-disubstituted-4H-1,2,4-triazoles

A series of 3,4-disubstituted-4H-1,2,4-triazoles was prepared and evaluated for their activity to cause bleaching injury in lettuce seedlings and to promote germination of lettuce seeds at a high temperature of 30°C. In the 3-propargylthio-4-substituted-4H-1,2,4-triazole series, the 3,4-dichlorophenyl analog 8 with the highest bleaching activity promoted the seed germination at 30°C, however, its activity was much less than that of fluridone, an inhibitor of abscisic acid biosynthesis. 4-Phenyl-3-(4-trifluoromethylphenyl)- 4H-1,2,4-triazole (30) showed germination promoting activity comparable to that of compound 8. There was no apparent correlation between the ability of 4-phenyl-3-substituted-4H-1,2,4-triazoles to cause bleaching injury and the germination promoting activity on lettuce seeds at 30°C.