Synthesis of Functionalized Indoles via Palladium-Catalyzed Aerobic Cycloisomerization of o-Allylanilines Using Organic Redox Cocatalyst.

A scalable and practical synthesis of functionalized indoles via Pd-(BuONO)-Bu-t cocatalyzed aerobic cycloisomerization of o-allylanilines is reported. Using molecular oxygen as a terminal oxidant, a series of substituted indoles were prepared in moderate to good yields. The avoidance of hazardous oxidants, heavy-metal cocatalysts, and high boiling point solvents such as DMF and DMSO enables this method to be applied in pharmaceutical synthesis. A practical gram-scale synthesis of indomethacin demonstrates its application potential.