Reshaping Ullmann Amine Synthesis in Deep Eutectic Solvents: A Mild Approach for Cu-Catalyzed C-N Coupling Reactions With No Additional Ligands

Abstract

The CuI-catalyzed Ullmann amine cross-coupling between (hetero)aryl halides (Br, I) and aromatic and aliphatic amines has been accomplished in deep eutectic solvents as environmentally benign and recycling reaction media. Under optimized conditions, the reaction proceeds smoothly under mild conditions (60-100°C) in air, in the absence of ligands, with a catalyst (CuI) loading of 10 mol% and K₂CO₃ (aliphatic primary and secondary amines) or t-BuOK (aromatic amines) as the base. A variety of amines have been synthesized in yields up to 98% with a broad substrate scope.

Keywords: Ullmann amination reaction; amine synthesis; copper catalysis; deep eutectic solvents; green chemistry.