Cu-Mediated Ullmann-Type Cross-Coupling and Industrial Applications in Route Design, Process Development, and Scale-up of Pharmaceutical and Agrochemical Processes

Cu-mediated Ullmann-type cross-coupling has experienced significant advances over the last century since the seminal publication by Ullmann in 1901. These advances have significantly expanded the scope of the original classical Ullmann coupling of aryl halides for formation of diaryl compounds to include the formation of carbon–heteroatom and other carbon–carbon bonds. The introduction of bidentate ligands drastically improved the performance of this class of transformations to enable milder reaction conditions that can tolerate a wide range of sensitive functional groups. Recent development of more powerful second-generation bidentate ligands has further allowed the coupling of less reactive aryl chlorides to proceed smoothly and realized low catalyst and ligand loadings for a broad scope of Ullmann-type cross-coupling reactions. As a result of these breakthrough advances in the past decades, Cu-mediated Ullmann-type cross-coupling reactions have been frequently implemented in academic research and have found ubiquitous industrial applications including the preparation of pharmaceutical and agrochemical products. This review provides an overview of selected general Cu-mediated Ullmann-type transformations for the formation of carbon–carbon and carbon–heteroatom (C–N, C–O, C–S, and C–P) bonds and their applications in route design, process development, and scale-up of pharmaceutical and agrochemical processes.