摘要： A facile ring closure reaction with the N-l nitrogen of the 1,2,4-triazine ring occurs when 3-amino-6-hydrazino-1,2,4-triazin-5-one(1) is refluxed in either acid, orthoester/dimethylformamide, carbon disulfide, cyanogen bromide or nitrous acid. 3-amino-2-benzyl-6-hydrazino-1,2,4-triazin-5-one(2), containing the benzyl group on the 2-position of 1, can not be cyclized under the above reaction conditions except refluxed with carbon disulfide in pyridine-water(1:1), which will pass through a novel rearrangement cyclization to afford a bicycloheterocyclic compound,6-amino-3-benzylmercapto-1,2,4-triazolo[3,4-f][l,2,4]triazin-8(7H)-one(3). The mechanisms of their ring closure and rearrangement cyclization will be presented in detail.

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