Rhodium-Catalyzed Formal C–H and X–H Insertion Reaction Involving an Exocyclic Vinylic Cation Intermediate

The carbocation is one of the highly reactive intermediates in synthetic chemistry; however, catalytic selective transformations involving vinylic cation species remain elusive in comparison to sp²-hybrid ones. Herein, we report a Rh-catalyzed formal C-H and X-H insertion reaction of in situ-generated exocyclic vinylic cations with a variety of nucleophiles, affording tetrasubstituted alkenes incorporating a cyclobutanone motif with a broad substrate scope under mild conditions. The utility of this method has been demonstrated for the synthesis of 3-methylenecyclobutanone derivatives, which are difficult to access using other methods, serving as versatile building blocks for a range of postfunctionalization conversions.