Direct assembly of 3,4-difunctionalized benzofurans and polycyclic benzofurans by phenol dearomatization and palladium-catalyzed domino reaction

A method to directly convert 2-alkynylphenols to 3,4-difunctionalized benzofurans and polycyclic benzofurans was developed. This protocol involves a hypervalent-iodine-mediated oxidative dearomatization to break the aromaticity of 2-alkynylphenols, and a palladium-catalyzed domino reaction to install two functional groups at the C3 and the C4 positions and restore the aromaticity of benzofurans. Destruction and reconstruction: The combination of a hypervalent-iodine-mediated oxidative dearomatization and palladium-catalyzed domino reaction provides a practical approach to 3,4-difunctionalized benzofurans and polycyclic benzofurans from 2-alkynylphenols.