N-Heterocyclic Carbene-Catalyzed Formal Intramolecular [3 + 2] Annulations of Cyclohexadienone-Tethered Ynals.

A formal [3 + 2] annulation of cyclohexadienone-tethered ynals is enabled by an N-heterocyclic carbene (NHC) catalyst, affording a tricyclo[6.2.1.0 4,11 ]undecane framework. This study represents the first demonstration of using C═C double bonds as the reaction partner in the NHC-catalyzed annulation of ynals. This strategy is characterized by mild reaction conditions and 100% atom economy as well as high catalytic performance and efficiency.