Palladium‐Catalyzed Aerobic Synthesis of Terminal Acetals from Vinylarenes Assisted by π‐Acceptor Ligands

Terminal acetals were synthesized from various vinylarenes and 1,2‐ or 1,3‐diols using a simple PdCl 2 (MeCN) 2 /methoxy‐ p ‐benzoquinone (MeOBQ)/CuCl catalyst system and 1 atm of O 2 under mild reaction conditions by the anti‐Markovnikov nucleophilic attack of an oxygen nucleophile on the coordinated vinylarenes. Cyclic α,β‐unsaturated carbonyl compounds such as MeOBQ and N ‐phenylmaleimide were especially effective as additives to afford higher yields of the desired terminal acetals. Kinetic experiments indicated that MeOBQ operates as a π‐acceptor ligand for Pd to accelerate the reaction and that the dissociation of a chloride ion from Pd precedes the rate‐determining step.