Construction of\nIsochromanones via Hemin-Catalyzed\nPhenol-Enamine Oxidative Annulation

We have developed a hemin-catalyzed biomimetic oxidative\nannulation\nof 2,3-dihydroxybenzoic acid with an array of cyclic enamines to form\nisochromanones in good to excellent yields and high regioselectivity.\nThis formal [4+2] cycloaddition protocol showed high efficiency and\nremarkable functional group tolerance. Mechanistic studies indicate\nthe involvement of a single-electron oxidation pathway. Preliminary\nbiological investigations showed that isochromanones <b>3ag</b> and <b>3ca</b> exhibited antineoplastic activities against\nMCF-7 cell lines with IC<sub>50</sub> values of 25.21 and 29.09 μM,\nrespectively.