Copper Nanoparticles Stabilized in a Porous Chitosan Aerogel as a Heterogeneous Catalyst for C−S Cross-coupling

Cu nanoparticles (NPs) embedded into chitosan fibrils act as a heterogeneous catalyst for the C−S coupling of aryl halides and thiophenol in toluene. The catalyst can be reused under optimal conditions with some activity decrease from the first to the second use. Characterization of the reused catalyst shows that Cu NPs do not undergo agglomeration. Cu‐chitosan is more active for aryl iodides than aryl bromides and chlorides. The presence of chitosan in a large excess is detrimental for the catalytic activity, probably because of the increase of solvent viscosity. It was found that halides formed as byproducts in the reaction act as a catalyst poison and may influence the extent of Cu leaching. Something fishy going on: The fibrils of chitosan, a natural polysaccharide from crustacean skins, define macropores in which Cu nanoparticles are stabilized, and the resulting solid promotes the reaction of thiophenol and iodobenzene.