N‐Heterocyclic Carbene‐Catalyzed Asymmetric Cyclization of Cyclohexadienone‐Tethered Ynals to Stereodivergent 6,5‐Bicyclic and 6,5,5‐Tricyclic Products

Transforming a prochiral substrate into two stereodivergent products using a single chiral catalyst remains a significant challenge. Herein, an NHC‐catalyzed asymmetric cyclization of cyclohexadienone‐tethered ynals, enabling the preparation of two stereodivergent products: 6,5‐bicyclic and 6,5,5‐tricyclic frameworks, is reported. The reaction proceeds through two distinct pathways: an allenolate‐Michael addition/esterification sequence and an allenolate‐Michael addition/intramolecular Dieckmann condensation process. This approach represents a novel and efficient strategy for transforming a prochiral substrate into two products in a stereodivergent manner.