Monosubstituted-1,2,4-triazin-3-ones

Oxidation of 3-methoxy- or 3-phenoxy-1,2,4-triazines (228) with perbenzoic acid converted them into the appropriate 1-oxides (229) (71JOC787). Peracid treatment of 1,2,4-triazin-3-ones with an unsubstituted 5-position (84 R5 = H) gave l,2,4-triazine-3,5-diones (182) (69JHC403), while 5-substituted l,2,4-triazin-3-ones (84) afforded the appropriate 1-oxides (230) (66JOC3914). 3-Amino-l,2,4-triazines with an unsubstituted (86a) or a monosubstituted amino group (86b) were oxidized by peracids to give the 2-oxides (231), while the 3-dialkylamino compounds (86c) afforded the 1-oxides (232) (77JOC546). 

By analogy with 4- and 2-chloropyrimidines, it is reasonable to predict the relation 5-as-triazinyl > 3-os-triazinyl. The substantial activation by additional ring-nitrogens, especially in the optimal 1,3,6 arrangement, is evident in the fact that chloro-s-triaasines, even when deactivated by one or two substituents, are equally or more reactive than many chloro-azines or chloro-diazines. For example, 2,4,6-trichloro-s-triazine reacts with various nucleophiles to give monosubstituted derivatives at 0-10°, disubstituted at 20-30°, and trisubstituted at... 

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