Development of Second Generation Gold-Supported Palladium Material with Low-Leaching and Recyclable Characteristics in Aromatic Amination

An improved process for the preparation of sulfur-modified gold-supported palladium material [SAPd, second generation] is presented. The developed preparation method is safer and generates less heat (aqueous Na2S2O8 and H2SO4) for sulfur fixation on a gold surface, and it is superior to the previous method of preparing SAPd (first generation), which requires the use of the more heat-generating and dangerous piranha solution (concentrated H2SO4 and 35% H2O2) in the sulfur fixation step. This safer and improved preparation method is particularly important for the mass production of SAPd (second generation) for which the catalytic activity was examined in ligand-free Buchwald–Hartwig cross-coupling reactions. The catalytic activities were the same between the first and second generation SAPds in aromatic aminations, but the lower palladium leaching properties and safer preparative method of second generation SAPd are a significant improvement over the first generation SAPd.