Solvent-, Ligand, and Additive-Free Sonogashira-Type C–C Coupling by Mechanochemical Extrusion with Chitin-Derived Catalysts

Mechanochemical extrusion provides a sustainable and efficient approach for the preparation of mono- and bimetallic palladium and copper catalysts supported on nitrogen-doped carbons. In this study, palladium and copper mono- and bimetallic catalysts were synthesized via solvent-free extrusion and thoroughly characterized by XRD, HRTEM, N2 physisorption, and XPS, revealing uniformly dispersed nanoparticles with strong metal–support and metal–metal interactions. The catalysts were evaluated in the model Sonogashira coupling of iodobenzene with phenylacetylene under continuous mechanochemical extrusion. The bimetallic Pd-Cu system exhibited superior activity and selectivity, effectively suppressing side reactions, such as phenylacetylene dimerization. A comprehensive parametric study, as well as analyses of substrate extent and catalyst recyclability, highlighted the crucial role of mechanical energy in enabling these transformations. Moreover, the dimerization of phenylacetylene was separately investigated, providing further insight into the formation of the corresponding dimer. Overall, these results demonstrate the ability of extrusion to finely control catalyst properties, optimize catalyst-substrate interactions, and offer a sustainable, solvent-free route to high-performance heterogeneous catalysts suitable for continuous-flow applications.