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

Abstract

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.

Development of a Sulfur-Modified Glass-Supported Pd Nanoparticle Catalyst for Suzuki–Miyaura Coupling

“…As reported in our previous research, [17][18][19][20][21][22][23][24][25][26][27] SAPd absorbs very few organic compounds and can therefore be used in combinatorial synthesis because of its small surface area. It was envisaged that SGlPd would perform in a similar manner to SAPd.…”

“…Organic materials containing sulfate and xylene as the major ingredients are distributed between the Pd nanoparticles, allowing for the formation of stable high-density PdNPs without condensation. [17][18][19][20][21][22][23][24][25][26][27] The results of the XANES analysis suggest that the oxidized sulfur preserves the structure of the PdNPs in SGlPd as well as SAPd.…”

“…Notably, this catalyst exhibited good recyclability properties in all cases with low palladium leaching. [17][18][19][20][21][22][23][24][25][26][27] In 2015, we successfully analyzed the structure of our SAPd catalyst by X-ray absorption fine structure (XAFS) and transmission electron microscopy (TEM) analyses and found that the Au particles in this material simply acted as a solid support for the SAPd membrane. 27) SAPd is now commercially available as a safe, facile, recyclable and low-leaching PdNP catalyst.…”

Development of Metal Nanoparticle Catalysis toward Drug Discovery

“…The reverse oxidation from 18 to 17 with oxygen gas succeeded by our established condition smoothly, then reversible redox switching of pentaphene derivative 17 was completed. 15) Because the microwave technique sometimes allows for reduced reaction times and increased yields than those obtained using conventional heating methods, microwave-assisted chemical reactions are becoming a popular technique in organic synthesis. [77][78][79] Our idea was to adopt SAPd(0) as a new solid-support for the Suzuki-Miyaura reaction and use the microwave technique to make the system much more efficient.…”

“…In this review, we summarize our recently developed novel Pd NPs catalyst, named self-assembled Au-supported palladium (SAPd(0)), which can repeatedly catalyze Suzuki-Miyaura coupling, Buchwald-Hartwig reaction, carbon(sp 2 and sp 3 )hydrogen functionalization, double carbonylation, removal of the allyl protecting groups of allyl esters, and redox switching without any ligand. [11][12][13][14][15][16][17][18][19][20][21][22] We also introduce the chemical and structural properties of SAPd(0) by spectroscopic analysis. 23) Transmission electron microscopy (TEM) analyses and extended X-ray absorption fine structure (EXAFS) experiments were performed to clarify the geometrical properties of Pd catalysis in SAPd(0).…”