In Situ Preparation of Palladium Nanoparticles for C-2 Selective Arylation of Indoles in Agro-Waste Extract Based Mixed Solvents

An efficient and practical method for the in situ generation of palladium nanoparticles was successfully established in a water extract of pomelo peel ash. The produced palladium nanoparticles were characterized by energy-dispersive X-ray spectroscopy elemental mapping, field emission scanning electron microscopy, high-resolution transmission electron microscope, X-ray powder diffraction, and showed high catalytic activity for selective C-2 arylation of indoles. A series of 2-arylindoles were smoothly installed in moderate to good yields through the direct palladium-catalyzed cross-coupling reactions of indoles and iodoarenes without external ligand, base, oxidant, and preinstallation directing group.

Automated summary

An efficient method for in situ generation of palladium nanoparticles in a water extract of pomelo peel ash was successfully established, enabling the synthesis of highly catalytic palladium nanoparticles for the selective C-2 arylation of indoles. A series of 2-arylindoles were smoothly synthesized in moderate to good yields through direct palladium-catalyzed cross-coupling reactions without the need for external ligands, bases, oxidants, or preinstallation directing groups.