Assembly of (E)‐γ‐Lactones Fused Five‐ or Six‐Membered Ring via Palladium‐Catalyzed Cascade Annulation Reaction

Abstract A palladium‐catalyzed divergent cascade annulation reaction of unactivated cycloalkenes with alkynoic acids under aerobic conditions is accomplished. This catalytic protocol provides an efficient and economical strategy to accommodate a broad scope of (E)‐ γ ‐lactones fused five‐ or six‐membered ring motifs with good regioselectivities and yields ( 57 examples, up to 94 % yield and E/Z up to 98 : 2 ). More importantly, the developed catalytic strategy is applicable to a wide array of unactivated cycloalkenes, including cyclopentene, cyclohexa‐1,3‐diene, cyclohexa‐1,4‐diene, cyclohepta‐1,3‐diene and conjugated 1,3‐diene.