Nickel-Catalyzed Synthesis of Structurally Diverse N-(hetero)aryl Pyrroles

Abstract

Pyrrole is an important five-membered aromatic nitrogen compound found in various pharmaceuticals and natural products, including functional materials. Many methods have been developed to create substituted pyrroles. Nevertheless, the structurally diverse synthesis of N-substituted pyrroles is less documented. Herein, we describe a simple procedure for the preparation of functionalized pyrroles employing 2,5-hexandione and anilines as starting materials in the presence of a well-defined homogeneous nickel catalyst (NiCl₂·6H₂O + dppe). Sensitive functional groups in anilines, such as halogen (F, Cl, Br, and I), ester, nitrile, and sulfur moieties, were well-tolerated and yielded a diverse array of N-(hetero)aryl pyrroles in high yields (50%–95%). These results were relatively challenging to achieve with previous methods. The reaction also occurs efficiently with succinaldehyde to yield a series of desired N-aryl pyrrole skeletons.