Palladium Pincer Complex Catalyzed Cross-Coupling of Vinyl Epoxides and Aziridines with Organoboronic Acids

摘要

Palladium-catalyzed cross-coupling of vinyl epoxides and aziri-dines with organoboronic acids was performed by using 0.5-2.5 mol % pincer-complex catalyst.The reactions proceed under mild conditions affording allyl alcohols and amines with high regioselectivity and in good to excellent yields.Under the applied reaction conditions aromatic chloro-,bromo and iodo substituents are tolerated.Our results indicate that the mechanism of the pincer complex catalyzed and the corresponding palladium(O)catalyzed process is substantially different.It was concluded that the transformations proceed via transmetalation of the organoboronic acids to the pincer-complex catalyst followed by an S_N2'-type opening of the vinyl epoxide or aziridine substrate.In this process the palladium atom is kept in oxidation state +2 under the entire catalytic process,and therefore oxidative side reactions can be avoided.