Stereoselective [8 + 2] Cycloaddition Reaction of Azaheptafulvenes with α-Chloro Aldehydes via N-Heterocyclic Carbene Catalysis.

A highly efficient [8 + 2] cycloaddition reaction of azaheptafulvenes with α-chloro aliphatic aldehydes enabled by N-heterocyclic carbene catalysis is presented, delivering cis-cycloheptatriene-fused γ-lactams with good yields, moderate to good diastereoselectivies, and excellent enantioselectivies. This higher order cycloaddition reaction can be readily expanded to the gram scale, and the products could be further transformed to other useful compounds via simple operations.