Fused nitrogen heterocyclesnamely, pyrazolo[3,4-d]pyridazin-7(6H)-ones have been obtained by exploiting the 1,3-dipolar nature of N-arylsydnones, from hydrazones of 3-aryl-4-acetylsydnones via the Vilsmeier–Haack strategy. Facile intramolecular nucleophilic addition followed by CO₂ elimination under reflux or upon microwave irradiation was presented. Plausible mechanisms for the formation of the title compounds are proffered. Structure confirmatory evidence came from single-crystal X-ray crystallography.

中文翻译：

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由3-芳基sydnones偶然形成2 H -Pyrazolo [3,4- d ] pyridazin -7（6 H）-ones

稠合氮heterocyclesnamely，吡唑并[3,4- d ]哒嗪-7-（6 ħ） -酮已通过开发的1,3-偶极性质得到 Ñ -arylsydnones，从3-芳基-4- acetylsydnones腙经由所述Vilsmeier–Haack策略。提出了容易的分子内亲核加成，然后在回流下或微波辐射下消除CO _2的方法。提出了可能的标题化合物形成机理。结构确认证据来自单晶X射线晶体学。