Iodine(III)‐Mediated Unexpected Ring‐Contraction Rearrangement and Halogenated Addition Reaction to Synthesize 3‐Substituted Phthalides and Isochroman‐1‐One Derivatives

Abstract Iodine(III)‐mediated ring‐contraction rearrangement and halogenated addition reaction have been realized. A series of 3‐substituted phthalides and isochroman‐1‐one derivatives bearing multiple functional groups were obtained in good to excellent yields under mild reaction conditions. Computational studies indicated that the reaction proceeds via a proton transfer followed by ring opening and ring formation to produce the target product. Moreover, preliminary biological evaluations revealed that both of 3‐substituted phthalides and isochroman‐1‐one derivatives show good antitumor activities.