Hydrofunctionalization of Polyunsaturated Hydrocarbons via Palladium(0) π-Lewis Base-Mediated Protonation

Palladium(0)-catalyzed asymmetric hydrofunctionalization of polyunsaturated hydrocarbons offers an atom-economic and highly stereoselective strategy for the synthesis of chiral molecules. Traditionally, these transformations are initiated via well-established mechanisms such as Pd─H insertion or ligand-to-ligand hydrogen transfer (LLHT). More recently, a distinct catalytic mode has emerged, wherein Pd⁰ acts as a π-Lewis base catalyst to promote the outer-sphere protonation of diverse polyunsaturated hydrocarbons, such as 1,3-dienes, 1,3-enynes, and allenes, through η²-coordination and subsequent π-backdonation, emphasizing its unique mechanistic features and reaction patterns. Importantly, this approach has enabled the construction of a broad array of C─C, C─N, C─O, and C─P bonds with the resultant Pd^II intermediates, generally in an enantioselective manner, offering efficient synthetic routes to chiral scaffolds and paving new avenues for asymmetric hydrofunctionalization.