Sustainable Mn-assisted Cu-catalyzed cross-coupling reaction has been developed for a range of (hetero)aryl, and styrenyl halides with various primary amides, sulfonamides, and cinnamamide, in air without solvents/added ligands. This protocol successfully produced the desired cross-coupling products, N-aryl and N-styryl amides, sulfonamides, and cinnamamides in good to excellent yields with broad substrate scope and tolerance to various sensitive functionalities. Based on several experimental studies, a novel catalytic cycle has been proposed for this transformation.

Abstract

We report, for the first time, an efficient manganese (Mn)-assisted copper (Cu)-catalyzed cross-coupling reaction that involves a range of aryl, heteroaryl, and styrenyl halides with various primary amides, sulfonamides, and cinnamamide, in air without solvents or added ligands. This cost-effective protocol successfully produced the desired cross-coupling products—N-aryl and N-styryl amides, sulfonamides, and cinnamamides—in good to excellent yields. It demonstrates a broad substrate scope (98 examples) and is tolerant to various sensitive functionalities such as –COCH₃, –CO₂Et, –NO₂, –OH, –NH₂, –Br, –Cl, –F, –CF₃, –OCF₃, –OCH₃, –CH₂Ph, and heterocycles. No conventional workup is needed for this protocol, and the developed method is suitable for gram-scale synthesis. Notably, the catalyst is cost-effective, environmentally benign, and can be reused at least five times with minimal loss of catalytic activity. This protocol demonstrates a lower E-factor and PMI value compared to other methods, indicating its sustainability and benignity. Several experiments, including X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM), were carried out to identify the catalytically active species based on Mn–Cu and their oxidation state. Additionally, a radical clock experiment was performed using a radical probe to investigate the reaction mechanism, and a novel Mn–Cu-based catalytic cycle for this transformation has been proposed.