We developed a method for allowing cascade cyclization of 2-nitrochalcones with pyrazoles, imidazole, and indazole in the presence of CuI catalyst, DBU base, and THF solvent. The conditions were tolerant of an array of useful functionalities including ester, nitro, cyano, halogen groups. A mechanistic consideration was also provided, as H₂O₂ was presumably a byproduct. Our method appears to be a rare example to directly prepare C3-heterocyclic unprotected indoles.

中文翻译：

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铜催化的 2-硝基查耳酮与 NH-杂环的级联环化


我们开发了一种允许在 CuI 催化剂、DBU 碱和 THF 溶剂存在下将 2-硝基查耳酮与吡唑、咪唑和吲咪唑级联环化的方法。条件耐受一系列有用的官能团，包括酯、硝基、氰基、卤素基团。还提供了机制考虑，因为 H₂O₂ 可能是副产品。我们的方法似乎是直接制备 C3-杂环无保护吲哚的罕见例子。