1.2.4- Triazoles ring synthesis from hydrazine derivatives

Synthesis of Triazole Rings from Acyclic Compounds 4.12.4.2,1 Methods employing hydrazine derivatives... 

Synthesis starting from amidrazones (Scheme 59, c -d") is the most versatile preparation of the 1,2,4-triazole ring. Application to specific cases is governed by three considerations. One is the formation of the required amidrazone from a hydrazine with or without substituents and amide derivatives RC(=NH)X or RC(=NCOR )X where X = halide, OH, OAlk, SAlk, NH2, etc. With two reactive hydrazinic NH groups, isomeric amidrazones can be formed but the relative basicities usually predict the correct product. Unsymmetrical hydrazines YZNNH2 also form amidrazones but these cannot be cyclized unless Y or Z is reactive. 

The construction of a heterocyclic ring from two reagents, one of which contains a nitro group, is widely used in the synthesis of the nitro derivatives of pyrazole, isoxazole, and 1,2,3-triazole. Thus, for example, the reaction of sodionitromalonal-dehyde with substituted hydrazines leads to the corresponding derivatives of 4-nitropyrazole [33, 61, 471 173] (Scheme 63). 

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