Abstract
A number of 3-alkylthio-4-aryl-4H-1, 2, 4-triazoles were synthesized and evaluated for their bleaching activity by using a lettuce seedling test. In a series of 4-phenyl-4H-1, 2, 4-triazoles, 3-propylthio and 3-propargylthio analogs caused complete bleaching symptoms at 50ppm, while the activity fell off with increasing or decreasing size of the alkylthio group at the 3-position of the triazole ring. The introduction of a chloro, trifluoromethyl, methyl or ethoxy substituent at the meta- or para-position on the benzene ring increased the activity in comparison with that of the phenyl analog. 4-(3-Chlorophenyl and 4-chlorophenyl)-3-propargylthio-4H-1, 2, 4-triazole (16 and 17) markedly reduced β-carotene content as well as chlorophyll in plants. Inhibition of β-carotene formation was accompanied by an accumulation of large amounts of phytoene, suggesting that these 1, 2, 4-triazoles inhibit the desaturation of phytoene.
