Dual Cobalt and Photoredox Catalysis Enabled Redox‐Neutral Annulation of 2‐Propynolphenols

A hydroxyl‐assisted, organophotoredox/cobalt dual catalyzed annulation of 2‐propynolphenols to form 2‐hydroxymethyl‐benzo[ b ]furans was developed by employing 1,2,3,5‐tetrakis(carbazol‐9‐yl)‐4,6‐dicyanobenzene (4CzIPN) as photosensitizer and CoCl 2 (PPh 3 ) 2 /5,5′‐dimethyl‐2,2′‐bipyridine as cobalt catalytic precursor. Various substrates and functional groups were tolerated. The practical applications of this reaction were further demonstrated by enlarged gram‐scale and various derivations for complex heterocycles. Primary mechanistic studies suggested the involvement of cobalt‐hydride mediated hydrogen atom transfer (HAT) process. magnified image