1.2.4- Triazin-3 -ones

Condensation of 1,3-diphenyl[ 1,2,4]triazin-6-one 360, obtained from reaction of hippuric acid and phenylhydrazine, with aromatic aldehydes... 

Azirine-3-carboxamides with a second substituent in the 3-position (599) were used by Nishikawa and Sato for the synthesis of dihydro-1,2,4-triazin-6-ones (600) (71JCS(C)2648). 

Reaction of alkali hydroxide with l-methyl-l,2,4-triazinium salts 149 provokes transformation into 1,2,4-triazole derivatives 153 (Scheme 85) (71CC1636). The reaction is presumed to be initiated by addition of the nucleophile on the carbon adjacent to the quaternary nitrogen (i.e., at C-6). Attempts to obtain spectroscopic evidence for the intermediary cr-ad-duct 150 failed however, some support for their formation is provided by the fact that 1-methyl-1,2,4-triazin-6-ones 152 were isolated as by-products when 6-unsubstituted quaternary salts 149 (R3 = H) were treated with alkali under oxidative conditions (Scheme 85) (7ICC 1636). Transformation into triazoles 153 occurs in the presence of nucleofugic groups at C-3 (R1 = OCH3, SCH3) in salts 149 (Scheme 85). 

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