Construction of Isochromanones via Hemin-Catalyzed Phenol-Enamine Oxidative Annulation

We have developed a hemin-catalyzed biomimetic oxidative annulation of 2,3-dihydroxybenzoic acid with an array of cyclic enamines to form isochromanones in good to excellent yields and high regioselectivity. This formal [4+2] cycloaddition protocol showed high efficiency and remarkable functional group tolerance. Mechanistic studies indicate the involvement of a single-electron oxidation pathway. Preliminary biological investigations showed that isochromanones 3ag and 3ca exhibited antineoplastic activities against MCF-7 cell lines with IC₅₀ values of 25.21 and 29.09 μM, respectively.