Metal‐Free Synthesis of Furocoumarins: An Approach via Iodine‐Promoted One‐Pot Cyclization between 4‐Hydroxycoumarins and Acetophenones

A transition metal‐free approach was developed to achieve substituted furocoumarins via an iodine‐promoted one‐pot cyclization between 4‐hydroxycoumarins and acetophenones. High yields of furocoumarins were achieved in the presence of NH 4 OAc as an additive, while neither acidic nor basic additives were effective. The reaction would proceed via a 5‐exo‐tet cyclization but not an O‐alkylation. The fact that commercially available starting materials could be used without the need of a transition metal catalyst could be a significant advantage.