Cationic Suzuki-Miyaura Coupling with Acutely Base-Sensitive Boronic Acids

Fast, base-promoted protodeboronation of polyfluoroaryl and heteroaryl boronic acids complicates their use in Suzuki-Miyaura coupling (SMC) because a base is generally required for catalysis. We report a cationic SMC method using a PAd3-Pd catalyst that proceeds at rt in the absence of a base or metal mediator. A wide range of sensitive boronic acids, particularly polyfluoroaryl substrates that are poorly compatible with classic SMC conditions, undergo clean coupling. Stoichiometric experiments implicate the intermediacy of organopalladium cations, which supports a long-postulated cationic pathway for transmetalation in SMC.