Palladium‐Catalyzed Cascade Carboesterification of Cycloalkenes With Alkynoic Acids: A Facile Access to Fused (E)‐Chloro‐Substituted γ‐Lactones

A palladium‐catalyzed regiodivergent carboesterification of cycloalkenes with alkynoic acids under aerobic conditions with ionic liquids as an environmentally benign medium is accomplished. Using a combination of 1 mol% IPr ^{t Bu} –Pd–Cin–Cl, 2 equiv. of LiCl in [Amim]BF ₄ at rt for 16 h in the open air, a diverse array of alkynoic acids and cycloalkenes could be excellently tolerated. This cascade carboesterification approach features good yields (up to 83%), excellent regioselectivities ( Z / E up to 2:98), good functional group compatibility and high atom‐ and step‐economy. Notably, the robustness and potential of this synthetic strategy have also been successfully demonstrated by the gram‐scale synthesis and the synthesis of the challenging dual condensed γ‐lactones.