Advances in transition-metal-catalyzed synthesis of 3-substituted isocoumarins

3-Substituted isocoumarins are the most abundant class of naturally isocoumarins, found in several biologically active scaffolds and are precursors towards complex natural products. Considerable attempts have been devoted to the synthesis of these isocoumarins both by metal free or transition-metal-catalyzed reactions. Among the metal catalyzed reactions, the use of palladium, copper, gold, iron, nickel, rhodium, ruthenium, zinc, chromium, iridium, silver or thallium salts/complexes for the construction of 3-substituted isocoumarin ring is noteworthy due to being economical and good functional group tolerance. The current review focusses the recent reports on the Pd-, Cu-, Ag-, Fe-, Ni-, Rh-, Ru-, Zn, Cr-, Ir-, Ag- and Ti -catalyzed synthesis of isocoumarins.