3-Aryl-l,2,4-triazin-5-ones

There are many examples of the formation of cr -adducts derived from nucleophilic attack by G-nucleophiles at an unsubstituted carbon atom of the 1,2,4-triazine ring. For instance, the reaction of 3-aryl-l,2,4-triazin-5-ones 34 with indole and its methyl derivatives affords 3-aryl-6-(indolyl-3)-l,6-dihydro-l,2,4-triazin-5(2//)-ones 35 (Scheme 21) <1997JHC1013, 1998RJ0297>. In a similar way, adducts of 34 with iV,iV-dimethylaniline, viz. 36, are formed (Scheme 21) <1997JHC573, 1998RJ0297, 2001H(55)2349>. 

Stabilities of o -adducts derived from nucleophilic addition of alcohols and alkox-ide ions to azaaromatic compounds are varied to a great extent. A whole number of alkoxy adducts of 1,4-diazinium and 1,2,4-triazinium cations have been registered by NMR [114] however, attempts to isolate them failed. Contrary to that, treatment of 3-aryl-l,2,4-triazin-5-ones with primary or secondary alcohols in the presence of acetic anhydride results in the formation of rather stable 6-aIkoxy-l-acetyl-l,6-dihydro-l,2,4-triazin-5-ones (Scheme 38) [117, 140, 141],... 

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See also in sourсe #XX -- [ ]

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