Synthesis of 10‐Membered Azecines through Pd‐Catalyzed Formal [6+4] Cycloaddition and Their Transannular Reaction to Polycyclic Compounds

Abstract Azecine fragments are frequently presented in natural products and bioactive compounds. However, minor efforts have been devoted to these 10‐membered N‐heterocycles, and their synthesis is still challenging. Reported herein is the first catalytic formal [6+4] cycloaddition for the synthesis of 10‐membered azecines. Under palladium catalysis, the reaction of δ ‐vinylvalerolactones and benzofuran‐derived azadienes proceeds smoothly to afford benzofuran‐fused azecines with high diastereoselectivity in moderate to good yields. A unique transannular reaction of these 10‐membered azecines for the construction of polycyclic compounds is also demonstrated.