Photosynthetic electron transport inhibition by pyrimidines and pyridines substituted with benzylamino, methyl and trifluoromethyl groups

The decrease of the number of ring nitrogen atoms of 2-benzylamino-4-methyl -6-trifluoromethyl-1,3,5-triazines on herbicidal activity and inhibition of photosynthetic electron transport (PET) was assayed using thylakoids from Spinacia oleracea or atrazine-resistant Chenopodium album. Three 2-benzylam ino-4-methyl-6-trifluoromethyl-1,3,5-triazines, nine pyrimidines with a ben zylamino-, methyl- and trifluoromethyl-group, 2-benzylamino-6-methyl-4-trif luoromethyl- pyridine and N-benzyl-3-methyl-5-trifluoromethylaniline were s ynthesized and assayed. 2-(4-Bromobenzylamino)-4-methyl-6-trifluoromethylpy rimidine exhibited the highest PET inhibitory activity against Spinacia ole racea thylakoids of all compounds tested. The 2-benzylaminopyrimidines and 2-methylpyrimidines having a 4-halobenzylamino group exhibited higher PET i nhibition than atrazine and 2-trifluoromethylpyrimidines against Spinacia o leracea thylakoids. These PET inhibitory active compounds also exhibited a strong and similar inhibition both against atrazine-resistant Chenopodium a lbum thylakoids as well as against thylakoids from wild-type Chenopodium. T he herbicidal activity of 4-(4-bromobenzylamino)-2-methyl-6- trifluoromethy lpyrimidine was equivalent to that of known herbicides like simetryne, sima zine or atrazine.