Redox‐Neutral Vicinal Dialkylation of Aryl Boronic Esters via the Palladium/Norbornene Cooperative Catalysis

ABSTRACT Palladium/norbornene (Pd/NBE) cooperative catalysis has become an increasingly important tool for ipso/ortho difunctionalization of arenes; however, the ipso functionalization is primarily limited to coupling of a nucleophile or a π‐system. Here, we report a new type of Pd/NBE‐catalyzed difunctionalization reaction that simultaneously couples two alkyl electrophiles at the ipso and ortho positions of arenes. Diverse aryl boronic esters are employed as substrates. The redox‐neutral feature of this reaction allows broad functional group tolerance. The synthetic utility is demonstrated in a streamlined preparation of a complex benzoazepane. Mechanistic studies reveal the potential involvement of an unusual radical‐mediated ipso functionalization.