1.2.3- Benzotriazin-4 -ones synthesis

Poly(isoimide)s received interest as intermediates for Pis, because the ring closure of the poly(amic acid) runs faster with carbodiimides, e.g., dicyclo-hexylcarbodiimide, in comparison to acetic anhydride [44], However, the use of a carbodiimide yields the isoimide moiety exclusively, whereas acetic anhydride yields the ordinary imide. However, by treatment with suitable isomerizing agents, such as 1-hydroxybenzotriazole, or 3-hydroxy-1,2,3-benzotriazin -one, the isoimide can be converted to the imide. This technique is suitable for the synthesis of liquid thermosetting maleimide resins. 

There is only one reported synthesis of a bcnzannulated 1,2,4-triazocine system. 2-Phenylbenz-azete (1), which can be generated from 4-phenyl-l,2,3-benzotriazine by pyrolysis, is reacted with tetrazine 2 to give a [4 + 2] adduct, which loses nitrogen and finally results in the eight-membered-ring derivative after valence isomerization.2... 

The same methods used for 1,2,4-benzotriazines have,also been applied to the synthesis of naphtho-l,2,4-triazines. l-Amino-2-arylazonaphthalenes (663) with phosgene yield naphtho[l,2-e][l,2,4]-triazin-2-ones (664) (05MI21900), and the isomeric 2-amino-l-arylazonaphthalenes (665) with phosgene or isocyanates similarly gave naphtho[2,l-c]-[l,2,4]triazin-3-ones (666) <78HC(33)189, p.732). 3-Iminonaphtho[2,1 -e][ 1,2,4]triazines (667, 668) were obtained when (665) reacted with cyanogen bromide (08MI21900) or with isothiocyanates and mercury(II) oxide (Scheme 24). 

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