6-Aryl-1,2,4-triazine 4-oxide, reaction with amines

Similarly, ring opening was found in reactions of 6-aryl-1,2,4-triazine 4-oxides 53 with aliphatic amines, yielding open-chain 6-amino-1-hydroxy- 1,4,5-triazahex-atrienes 85. In this case, however, the nucleophile adds to the 3 position of the... 

The increase in thermodynamic stability of 85 is achieved by easy ring opening (01H127). This knowledge allows one to control the regioselectivity of the oxidative amination of the 6-aryl-l,2,4-tiiazine 4-oxides 53, obtaining either (i) the 5-amino-1,2,4-triazine 4-oxides 56 in the reaction of 53 with amines at low temperature in the presence of the oxidant or (ii) the 3-amino-1,2,4-triazine 4-oxides 88, provided the reaction is carried out in two steps (addition and oxidation) at room temperature or higher. 

Starting from ort/w-aminoarene imines 1. 4-aryl-substituted condensed 1,2,3-triazines 2 can be obtained.7,8 Using the oximes 3 instead of imines, condensed 1,2,3-triazine 3-oxides 4 can be isolated.7,8,127-129,241 Reaction of ort/io-aminoarenecarbamidoximes 3 (R — NH2) with nitrous acid afforded condensed l,2,3-triazin-4-amine 3-oxides 4 (R = NH2).7,8,195... 

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