Metal-catalyzed synthesis of isocoumarin derivatives (microreview)

Isocoumarins (1H-isochromen-1-ones), an important class of naturally occurring unsaturated lactones, exhibit a broad range of pharmacological activities including cytotoxicity toward HeLa cervical cancer cells,1 antioxidant activity in HepG2 cells exposed to oxidative stress conditions induced by H2O2,2 antiangiogenic,3 anticancer,4 , 5 antifungal,6 , 7 and antimicrobial activity.8 Isocoumarins are also important building blocks for the synthesis of a number of medicinally important heterocycles.9 – 11 A number of conventional methods have been used for the synthesis of isocoumarins starting from homophthalic acids,12 , 13 but metal-catalyzed synthesis of isocoumarins has attracted considerable attention due to its economic advantages and good functional group tolerance.14 , 15 Recent reports on the Cu-, Pd-, Ru-, and Rh-catalyzed synthesis of isocoumarins are reviewed here. Besides, an example of Re catalysis has appeared recently.16