Treeazole derivatives are an important class of heterocycles which exhibit a broad spectrum of biological activities. In recent years, life threatening systemic infections have become increasingly common, especially in the immune compromised hosts suffering from tuber culosis, cancer or AIDS and in organ transplant cases[1,2]. Several clinical drugs, such as azoles have also been developed to reduce the impact of fungal diseases. Following our research and interest in the synthesis of new biologically active heterocyclic compound. we decided to study the synthesis of new heterocyclic system (3) for this purpose, we first synthesized 2-hydrazinopyridazine (1) which was treated with CS2 and methyliodide in DMF respectively, to obtain quantitatively desired compound (2) .the reaction of compound (2) with hydrazine hydrate gave the hydrazine derivatives which was consequently reacted with various triethylorthoesters to give the corresponding 8choloro- [1,2,4] triazolo [4,3:1,5] [1,2,4] teiazolo [4,3-b] pyridazine 3(a-c) in good yields.(scheme 1).

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