A variety of 1,5-disubstituted imidazoles and related compounds were prepared, and their bleaching activity was evaluated by using the lettuce seedling test. 5-(4-Benzyloxyphenyl)-l-ethylimidazole (13) caused clear chlorosis, while the 2- and 3-benzyloxyphenyl analogs had no activity. In the 5-(4-benzyloxyphenyl)imidazole series, only the 1-propyl analog showed significant activity, as well as compound 13. Both substituents at the 1- and 5-position of the imidazole ring were indispensable for this activity. Of the series of compounds tested, l-ethyl-5-stilbenylimidazole (22) and 5-[4-(3-chlorobenzyloxy)phenyl]-l-ethylimid-azole (33) showed the highest activity. Compound 33 at 30 ppm decreased the chlorophyll content in the lettuce seedlings to less than 20% of that in the control.
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