Ligand-Enabled γ-C(sp3)-H Olefination of Free Carboxylic Acids

We report the ligand-enabled C-H activation/olefination of free carboxylic acids in the gamma-position. Through an intramolecular Michael addition, delta-lactones are obtained as products. Two distinct ligand classes are identified that enable the challenging palladium-catalyzed activation of free carboxylic acids in the gamma-position. The developed protocol features a wide range of acid substrates and olefin reaction partners and is shown to be applicable on a preparatively useful scale. Insights into the underlying reaction mechanism obtained through kinetic studies are reported.