In Situ Generation of Highly Active Dissolved Palladium Species from Solid Catalysts - A Concept for the Activation of Aryl Chlorides in the Heck Reaction

摘要

Heck reactions [Eq. (1)], typically catalyzed by palladium complexes in solution, are of growing interest in organic and fine-chemical synthesis. Expensive and often sensitive ligands are necessary to activate palladium and to stabilize it against agglomeration (palladium-black formation). On the other hand Reetz et al. and de Vries et al. achieved surprisingly high activity with "ligand"-free (if acetate is ignored) palladium acetate in reactions even with nonactivated aryl bromides. Genuinely ligand-free, heterogeneous palladium/activated carbon catalysts convert bromobenzene with similarly high activity.