Metal-catalyzed privileged 2-and 3-functionalized indole synthesis*

This review summarizes the metal-catalyzed approaches for the synthesis of privileged 2- and 3-functionalized indoles via the Fischer indole synthesis, cycloaddition reaction, C-H activation reaction, and coupling reactions. Polycyclic derivatives of indole are also listed including triptamine-based pharmaceutical 5-HT1D agonist L 775,606. Some important mechanism studies are described in details in this review. The review covers literature for the last 20 years.