Phosphine-Catalyzed Asymmetric (3 + 2) Annulations of δ‑Acetoxy Allenoates with β‑Carbonyl Amides: Enantioselective Synthesis of Spirocyclic β‑Keto γ-Lactams

While the phosphine catalysis is a powerful tool for the construction of N-heterocycles, the phosphine-catalyzed annulations toward lactam motif are still extremely scarce. Here, we report the asymmetric (3 + 2) annulations of δ-acetoxy allenoates with β-carbonyl amides by using the (R)-SITCP catalyst. The δC and γC of allenoate respectively engage in annulation with the αC and N of the amide, forging a γ-lactam with good to excellent stereoselectivity.