An efficient synthesis of a series of 6-chloro-3-substituted-[1,2,4]triazolo[4,3-b]pyridazines is described via intramolecular oxidative cyclization of various 6-chloropyridazin-3-yl hydrazones with iodobenzene diacetate. The structures of the newly synthesized compounds were assigned on the basis of elemental analysis, IR, NMR (1H and 13C) and mass spectral data. All the thirty three compounds 3a-q and 4b-q synthesized in the present study were evaluated for their in vitro cytotoxic activities against two Acute Lymphoblastic Leukemia (ALL) cell lines named, SB-ALL and NALM-6, and a human breast adenocarcinoma cell lines (MCF-7). The results revealed that triazoles 4 exhibit better cytotoxicity than their hydrazone precursors 3. Among triazoles, compounds 4f, 4j and 4q exhibited potent cytotoxic activity against SB-ALL and NALM-6 with IC50 values in the range of ∼1.64-5.66 μM and ∼1.14-3.7 μM, respectively, compared with doxorubicin (IC50 = 0.167 μM, SB-ALL). Compounds 4f, 4j and 4q were subjected to apoptosis assay after 48 h treatment and these compounds induced apoptosis of NALM-6 cells via caspase 3/7 activation. Results revealed that compound 4q represents potential promising lead.

中文翻译：

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6-氯哒嗪-3-基和6-氯-3-取代的-[1,2,4]三唑并[4,3-b]哒嗪作为细胞毒剂的合成及生物评价。

通过各种6-氯哒嗪-3-基与碘代苯二乙酸酯的分子内氧化环化反应，描述了一系列6-氯-3-取代-[1,2,4]三唑并[4,3-b]哒嗪的有效合成方法。根据元素分析，IR，NMR（1H和13C）和质谱数据确定了新合成化合物的结构。评价了本研究中合成的全部33种化合物3a-q和4b-q对两种命名为SB-ALL和NALM-6的急性淋巴细胞白血病（ALL）细胞系和人乳腺癌的体外细胞毒活性细胞系（MCF-7）。结果表明，三唑4比其前体3表现出更好的细胞毒性。在三唑中，化合物4f，与阿霉素（IC50 = 0.167μM，SB-ALL）相比，4j和4q对SB-ALL和NALM-6表现出有效的细胞毒性活性，IC50值分别在〜1.64-5.66μM和〜1.14-3.7μM范围内。处理48小时后，对化合物4f，4j和4q进行凋亡分析，这些化合物通过胱天蛋白酶3/7激活诱导了NALM-6细胞的凋亡。结果显示，化合物4q代表潜在的有前途的铅。