Palladium(0)-Catalyzed Nucleophilic Cyclization of Conjugated Enyne-Carbonyls Leading to Cyclic Allenic Alcohols

Conjugated enynes bearing carbonyl functionality undergo alkoxylative, alkylative, and aminative cyclizations under palladium(0) catalysis to afford cyclic allenic alcohols. The reaction affords two diastereomers due to the presence of both point chirality at secondary or tertiary alcohols and axial chirality of the allene, and the diastereoselectivity depends on the substituents on the terminal alkene and the electrophile as well as the identity of the nucleophile and additional phosphine ligands. The reaction is proposed to proceed via back-donation-driven activation of the conjugated enyne system, followed by nucleophilic substitution onto an <i>exo</i>-alkylidene-π-allylpalladium intermediate.