Hydroxyl Assisted, Photoredox/Cobalt Co‐catalyzed Semi‐Hydrogenation and Tandem Cyclization of o‐Alkynylphenols for Access to 2,3‐Dihydrobenzofurans

Herein, a hydroxyl assisted, photoredox/cobalt co‐catalyzed semi‐hydrogenation and tandem cyclization of o‐alkynylphenols is developed towards direct assembly of 2,3‐dihydrobenzofurans. Moderate to good yields were obtained for a range of sterically and electronically diverse 2‐propynolphenols under mild conditions. Mechanistic studies demonstrated the inevitable role of the alcoholic hydroxyl group with (Z)‐alkene as the real intermediate. Finally, a key low‐valent cobalt catalyzed intramolecular hydroetherification of alkene is proposed.