Chemodivergent Higher‐Order Annulation of Azaheptafulvenes with Enals Through N ‐Heterocyclic Carbene Catalysis

A base‐directed, chemodivergent, higher‐order annulation between azaheptafulvenes and enals has been developed through N ‐heterocyclic carbene catalysis. In the presence of an N ‐heterocyclic carbene organocatalyst, DBU promotes an [8 + 3] annulation with excellent chemo‐ and diastereoselectivities, whereas the reaction proceeds via an [8 + 2] annulation when potassium carbonate is used as the base. In addition, the reaction can be carried out on a gram scale, and the products are efficiently converted into bicyclic derivatives.