Palladiumcatalyzed

Palladium-catalyzed reactions refer to transformations that use palladium catalysts to form new chemical bonds, most prominently carbon–carbon and carbon–nitrogen linkages. These reactions are central to modern organic synthesis due to their broad substrate scope, functional-group tolerance, and applicability to complex molecules. Common catalysts are Pd(0) species such as Pd(PPh3)4 or precatalysts that generate active Pd(0) in situ, paired with ligands including phosphines and N-heterocyclic carbenes. Mechanistically, many palladium-catalyzed processes proceed via a Pd(0)/Pd(II) catalytic cycle involving oxidative addition to an electrophile, transmetallation or nucleophilic coupling, and reductive elimination to forge the new bond, regenerating Pd(0). In some cases, high-oxidation-state Pd intermediates or alternative cycles are invoked.

The best-known families are cross-couplings, including Suzuki–Miyaura (boronic acids with aryl/vinyl halides), Stille (tin reagents), Negishi (organozinc), Kumada (Grignard reagents), and Hiyama (silicon-based partners). Other prominent reactions include the Heck reaction, which couples aryl or vinyl halides with alkenes to form alkenes; Sonogashira coupling of terminal alkynes with haloarenes; and Buchwald–Hartwig amination for C–N bond formation. Carbonylation, hydrofunctionalization, and C–H activation variants further extend the repertoire.

Applications span pharmaceutical synthesis, natural product construction, and materials science, enabling rapid assembly of biaryl motifs, heterocycles, and complex scaffolds. Limitations include the cost of palladium, sensitivity to air or moisture for some catalysts, and the need to remove metal residues from products. Ongoing research focuses on more active, robust precatalysts and more sustainable ligand designs.