Asymmetric Fluorolactonization with a Bifunctional Hydroxyl Carboxylate Catalyst

We
report the first successful example of a highly enantioselective
fluorolactonization with an electrophilic fluorinating reagent, Selectfluor®, in the presence of a novel bifunctional organocatalyst.
The catalyst design includes a carboxylate anion functioning as a
phase-transfer agent and a benzyl alcohol unit to capture the substrate
through hydrogen bonding. Fluorinated isobenzofuranones were obtained
in good yields with up to 94% ee (97:3 er). On the basis of mechanistic
studies, we propose a unique reaction mechanism with potential for
further applications.