Palladium‐Catalyzed Annulations of an Anti‐Bredt Olefin

A famous class of alkene‐containing compounds that have intrigued chemists for more than a century are anti‐Bredt olefins (ABOs). ABOs are a subclass of bridgehead alkenes that reside in small ring systems, thus rendering them unstable and historically challenging to leverage in chemical synthesis. The present study describes metal catalyzed reactions of a [2.2.1]‐bridged bicyclic ABO, wherein two in situ‐generated species, both present in low concentration and generated transiently, undergo a productive reaction. The transformation uses palladium catalysis to unite the aforementioned ABO with indole‐based trapping partners, thus delivering unusual heterocyclic products. The scope of the reaction is reported, as well as computations concerning the putative Pd‐bound ABO species. The latter suggests that the short‐lived ABO is stabilized by Pd via the energetically favorable formation of an intermediate palladacycle. This methodology is expected to prompt the further development of unconventional reactions, including metal‐catalyzed processes of ABOs and other transient olefins.