Sigmatropic Dearomatization/Defluorination Strategy for C−F Transformation: Synthesis of Fluorinated Benzofurans from Polyfluorophenols

Facile synthesis of fluorinated benzofurans from polyfluorophenols has been accomplished by means of a sigmatropic dearomatization/defluorination strategy composed of three processes: (1) interrupted Pummerer reaction of ketene dithioacetal monoxides with polyfluorophenols followed by [3,3] sigmatropic rearrangement, (2) Zn‐mediated smooth reductive removal of fluoride from the dearomatized intermediate, and (3) acid‐promoted cyclization/aromatization. Mechanistic investigations revealed important characteristic reactivity of polyfluorophenols in the present system. Some of the fluorinated benzofuran products were transformed by utilizing the 2‐methylsulfanyl moieties. Facile synthesis of fluorinated benzofurans from polyfluorophenols has been accomplished by means of a sigmatropic dearomatization/defluorination strategy composed of three processes: interrupted Pummerer reaction followed by [3,3] sigmatropic rearrangement, Zn‐mediated smooth reductive removal of fluoride from the dearomatized intermediate, and acid‐promoted cyclization/aromatization.