Palladium-catalyzed decarboxylative [4 + 2] cycloaddition of δ-vinylvalerolactones for the synthesis of spirocyclohexane compounds

All-carbon π-allylpalladium species, generated in situ from α,α-diester-δ-vinylvalerolactones, were first used as 1,4-dipoles in [4 + 2] cycloaddition reactions for the construction of structurally diverse spirocyclohexanes.