Palladium-Catalyzed C–N Cross-Coupling Reactions

Palladium-catalyzed carbon–nitrogen cross-coupling, often referred to as Buchwald–Hartwig amination, has evolved into a cornerstone of modern synthetic chemistry. This methodology enables the formation of C–N bonds between (hetero)aryl halides and a wide range of nitrogen nucleophiles under relatively mild conditions. Central to its success is the ability of palladium complexes to undergo oxidative addition into aryl–halide bonds, followed by ligand-assisted amine coordination, deprotonation and reductive elimination to release the coupled product. Advances in ligand design have expanded the substrate scope to include primary and secondary amines, amides and more challenging heterocyclic partners. Recent efforts have focused on improving sustainability through the use of recyclable solvents and reducing precious-metal loading, as well as on mechanistic understanding that allows precise control of regioselectivity and functional‐group tolerance. The broad utility of this transformation spans medicinal chemistry, material science and agrochemical synthesis, with applications in the late-stage functionalisation of drug leads and the modular assembly of organic electronic materials.

Research from Nature Portfolio

Mechanistic investigations have shed new light on ligand-dependent pathways that govern C–N bond formation. In particular, studies of ring walking have revealed how chelating ligands can promote or inhibit the intramolecular migration of palladium across a polyhalogenated arene, enabling selective desymmetrisation of tetrabrominated precursors. This insight was applied to the efficient synthesis of spirobisfluorene derivatives, creating diverse libraries of hole-transport materials with unprecedented regioselectivity. Such findings provide a blueprint for harnessing subtle ligand effects to achieve site-selective amination in complex molecular scaffolds.

Palladium-Catalyzed C–N Cross-Coupling Reactions publication trend

The graph below shows the total number of articles in palladium-catalyzed c–n cross-coupling reactions across all publications each year (not limited to Nature Index journals).

Technical terms

Buchwald–Hartwig amination: A palladium-catalysed method for forming C–N bonds between (hetero)aryl halides and nitrogen nucleophiles.

Oxidative addition: The step in which a palladium(0) complex inserts into an aryl–halide bond, generating a palladium(II) intermediate.

Reductive elimination: The step in which two ligands on palladium(II) couple and dissociate, regenerating palladium(0) and releasing the product.

Ligand: A molecule bound to a metal centre that modulates its electronic and steric environment, controlling reactivity and selectivity.

Ring walking: A phenomenon in which a metal catalyst migrates along a conjugated ring system, enabling selective functionalisation of adjacent positions.

Micellar conditions: Reaction media that use surfactant assemblies in water to solubilise organic substrates and catalysts, reducing reliance on organic solvents.

References

1. Ring walking as a regioselectivity control element in Pd-catalyzed C-N cross-coupling. Nature Communications (2022).
2. Ligated Pd-Catalyzed Aminations of Aryl/Heteroaryl Halides with Aliphatic Amines under Sustainable Aqueous Micellar Conditions. JACS Au (2024).
3. Important Role of NH-Carbazole in Aryl Amination Reactions Catalyzed by 2‑Aminobiphenyl Palladacycles. ACS Catalysis (2023).
4. Concatenating Suzuki Arylation and Buchwald–Hartwig Amination by A Sequentially Pd‐Catalyzed One‐Pot Process—Consecutive Three‐Component Synthesis of C,N‐Diarylated Heterocycles. Chemistry - A European Journal (2020).