Palladium‐Catalyzed Equilibrium Addition of Acidic OH Groups across Dienes

Mildly acidic OH groups undergo transition-metal-catalyzed reversible addition across the CC bonds of cyclic and acyclic dienes. For example, the simple complex [Pd(PPh3)4] (1 mol %) effectively catalyzes both the forward addition of phenol across dienes and the reverse elimination of phenol from allylic ethers (see scheme).