ABSTRACT Oxa‐ and aza‐spiro2.4heptane frameworks are privileged scaffolds in bioactive molecules. Herein, we report a catalyst‐controlled divergent synthesis of these spirocycles from readily accessible enyne‐amides and α‐bromomalonates. Under Au(I) catalysis, cycloisomerization generates a furan‐fused azadiene intermediate, which undergoes base‐promoted (2+1) annulation to afford 5‐oxa‐spiro2.4heptanes with excellent diastereoselectivity (>20:1). In contrast, Pd(II) catalysis triggers an intramolecular hydroamination to form a pyrrole‐fused oxodiene, followed by (2+1) annulation to deliver 5‐aza‐spiro2.4heptanes. This protocol enables selective assembly of diverse spirocyclic products under mild conditions, providing good to excellent yields with high diastereoselectivity.
Sun et al. (Mon,) studied this question.