Sustainable Heck–Mizoroki and Suzuki–Miyaura reactions mediated by aqueous palladium nanoparticles and imidazolium–sulfonate additives

Abstract

Herein, we present an efficient and sustainable approach to the Heck–Mizoroki (HM) and Suzuki–Miyaura (SM) cross-coupling reactions catalyzed by Pd nanoparticles dispersed in water. The protocol eliminates the need for organic co-solvents, phosphine ligands, or inert atmosphere, making it environmentally benign. The inclusion of novel branched imidazolium sulfonate-based zwitterionic additives (ImS3b-n) significantly enhances the solubility and mixing of hydrophobic reactants, optimizing reaction conditions. The catalytic system demonstrated excellent reusability, with both Pd nanoparticles and the additives recovered and reused for four cycles in the HM reaction between ethyl acrylate and iodobenzene, achieving a remarkable total turnover number (TON) of 8821 for ethyl cinnamate. Furthermore, the Pd nanoparticles effectively catalyzed the SM reactions of aromatic boronic acids. Both reactions were successfully scaled up to the gram level, maintaining exceptional reproducibility compared to small-scale reactions. The methodologies developed here not only utilize low Pd loading (0.03 mol%) but also obviate the need for chromatography purification, offering a streamlined, greener alternative for cross-coupling reactions. This work underscores a commitment to advancing Green Chemistry principles while achieving high efficiency and practicality in catalysis.