One‐Pot Transformation Strategy of o‐Hydroxyphenyl Propargylamines for Modular Access to 3‐Functionalized Benzofurans

Abstract A one‐pot strategy to C3‐functioanlized benzofurans is achieved from o ‐hydroxyphenyl propargylamines ( o ‐HPPAs). 3‐Aminobenzofurans were obtained in 64–96% yields through the cascade alkyne‐allene tautomerization and 5‐ exo‐dig annulation of o ‐HPPAs in the presence of KOH/NaO t Bu as the fruitful base combination. Moreover, with benzenesulfinates and diphenylphosphine oxide as nucleophiles, a one‐pot protocol towards these derivatives was also demonstrated through a cascade 1,4‐conjugate addition/5‐ exo‐dig annulation/aromatization process. Additionally, a gram‐scale synthesis and further transformation into other valuable functionalized benzofurans were conducted to show the potential in organic synthesis of these developed synthetic approaches.