α-卤代腙与异氰的[4+1]环化反应合成5-氨基吡唑类化合物

[4+1]Annulation ofα-Halo Hydrazones and Isocyans to Access Pyrazol-5-amines

异氰与原位生成的1,2-二氮杂-1,3-共轭二烯发生[4+1]环化反应。通过优化合成工艺,得到最佳反应条件为:α-卤代腙(1.0 eq.),异氰酸酯(1.2 eq.),无水碳酸钠(1.2 eq.),二氯甲烷作溶剂,室温反应24 h。并在此条件下进行了底物普适性考察,以高达99%的收率得到一系列5-氨基吡唑化合物,其结构经1H NMR,13C NMR和HR-MS(ESI)表征。

A series of pyrazol-5-amines were obtained in up to 99%yield via[4+1]annulation of isocyans and in situ generated 1,2-diaza-1,3-dienes fromα-halo hydrazones.After optimization of reaction conditions,the optimal conditions were confirmed:α-halo hydrazones(1.0 eq.)and isocyans(1.2 eq.)in CH2Cl2 with anhydrous Na2CO3(1.2 eq.)at room temperature for 24 h.The structure was characterized by 1H NMR,13C NMR and HR-MS(ESI).