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

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.