A palladium-catalyzed intermolecular cycloaddition of γ-methylidene-δ-valerolactones with electron-deficient olefins has been developed for the synthesis of spiro [2.4] heptanes with high selectivity through a nucleophilic ring closure to the central carbon of a π-allylpalladium intermediate. It was found that the course of the reaction is dependent on the ligand employed, and selective [4+ 2] cycloadditions can also be achieved by the use of a bulky ...
