Palladium‐Catalyzed (5+3) Annulation of 4‐Vinyl‐4‐butyrolactones with C,N‐Cyclic Azomethine Imines: Construction of Eight‐Membered Ring

In this paper, we designed and synthesized 4‐vinyl‐4‐butyrolactone as a precursor to generate the zwitterionic allylpalladium intermediates, which behaved as five‐membered all‐carbon synthon in palladium‐catalyzed (5+3) annulation with azomethine imines, giving eight‐membered ring‐fused heterocycles (26 examples, 49% to 97% yield, >20:1 dr).