Palladium-Catalyzed Aryne Insertion/Arene Dearomatization Domino Reaction: A Highly Chemoselective Route to Spirofluorenes

A palladium(0)-catalyzed dearomatizing [3+2] spiroannulation of naphthalene-based biaryls with arynes has been developed for the rapid construction of spirofluorene architectures. This reaction was realized by carbopalladation of aryne to generate an arylpalladium species, followed by termination with naphthalene dearomatization, which is a sharp contrast to the conventional C-H functionalization approach. Mechanistic studies revealed that the arene dearomatization might take place through a 5-exo-trig spiroannulation and distal-hydride elimination Heck-type pathway.