Fluorine‐Directed Diastereoselective Iodocyclizations.

An inside job: β‐Fluorinated lactones and tetrahydrofurans are synthesized by iodocyclization of various allylic fluorides. The fluorine substituent acts as a highly efficient syn‐stereodirecting group for the ring closure. The experimental results combined with theoretical studies provide evidence in support of an “inside fluoro effect” to account for the sense and level of stereocontrol of these reactions.