Copper-Catalyzed\nCascade Cyclization of 2‑Nitrochalcones\nwith NH-Heterocycles

We developed a method for allowing cascade cyclization\nof 2-nitrochalcones\nwith pyrazoles, imidazole, and indazole in the presence of CuI catalyst,\nDBU base, and THF solvent. The conditions were tolerant of an array\nof useful functionalities including ester, nitro, cyano, halogen groups.\nA mechanistic consideration was also provided, as H<sub>2</sub>O<sub>2</sub> was presumably a byproduct. Our method appears to be a rare\nexample to directly prepare C3-heterocyclic unprotected indoles.