Palladium‐Based Dyotropic Rearrangement Enables A Triple Functionalization of Gem‐Disubstituted Alkenes: An Unusual Fluorolactonization Reaction.

We report in this paper a Pd(II)‐catalyzed migratory gem‐fluorolactonization of ene‐carboxylic acids. Reaction of 4‐methylenealkanoic acid derivatives with Selectfluor in the presence of Pd(OAc)2 (1.0 mol %) at room temperature affords fluorolactones in good to excellent yields. 2‐(2‐Methylenecycloalkanyl)acetic acids are transformed to bridged fluorolactones under identical conditions. One C−C, one C−O and one tertiary C−F bond were generated along the gem‐disubstituted carbon‐carbon double bond in this operationally simple transformation. Trapping experiments indicates that the reaction is initiated by a 5‐exo‐trig oxypalladation followed by Pd oxidation, regioselective ring‐enlarging 1,2‐alkyl/Pd(IV) dyotropic rearrangement and C−F bond forming reductive elimination cascade. Post‐transformations of these fluorolactones taking advantage of the electrophilicity of the 1‐fluoroalkylcarboxylate function are also documented. [ABSTRACT FROM AUTHOR]