Facile Synthesis of 2‐Fluorobenzofurans: 5‐endo‐trig Cyclization of β,β‐Difluoro‐o‐hydroxystyrenes

Efficient synthetic methods were established for obtaining 2‐fluorobenzofurans involving various substituents. Upon being treated with 1,8‐diazabicyclo[5.4.0]undec‐7‐ene under microwave irradiation, the α‐unsubstituted β,β‐difluoro‐o‐hydroxystyrenes underwent nucleophilic 5‐endo‐trig cyclization to afford the corresponding 2‐fluorobenzofurans in high yields. Furthermore, 2‐fluoro‐3‐iodobenzofuran was successfully synthesized, and its transformation to various 3‐substituted 2‐fluorobenzofurans was demonstrated.