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Abstract Catalytic oxidation of tricyclic endo-norbornene-fused tetrahydrofuran with the bimetallic nanocluster Cu/Au-PVP in the presence of H2O2 or t-BuOOH as the oxidant leads to C–H bond oxidation adjacent to the ether function to give 4-oxa-tricyclo[5.2.1.0]-8,9-exo-epoxydecane, however, oxidation with Pd/Au-PVP takes place at the C=C double bond to give the same epoxide and the oxidative three-bond forming dimeric product, dodecahydro-1,4:6,9-dimethanodibenzofurano[2,3-b:7,8-b′]bisoxolane. Formation of the latter product suggests the involvement of a reactive Pd–C intermediate. Similarly, oxidative C–C bond-forming reactions are observed in cycloaddition reactions of N2-Boc-1,2,3,4-tetrahydro-γ-carbolines and 2,3-dihydroxybenzoic acid with Cu/Au-PVP (2–5 mol%) and H2O2 at 25 °C, providing two-bond-forming [4+2] cycloadducts. Under similar reaction conditions, Pd/Au-PVP did not produce the corresponding cycloadduct, indicating a need for complexation between Cu and the carboxylic acid group of 2,3-dihydroxybenzoic acid and the allylic amine function of the γ-carbolines during the cyclization reaction. The reported intermolecular coupling reactions using Pd/Au-PVP or Cu/Au-PVP nanocluster catalysts under oxidative conditions at 25 °C are unprecedented.
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This content will become publicly available on March 1, 2026
Understanding the promotional role of Pd in oxidative alcohol coupling reactions over dilute PdAu alloys
Oxidative coupling reactions enable biomass-derived oxygenates to serve as sustainable platform molecules for a wide range of high-value chemicals. These catalytic reactions can be selectively triggered over alloys wherein a highly active dopant metal such as Pd is diluted into a sea of highly selective host metal atoms such as Au. Here, a range of supported Pd1Aux (x = 5–200) alloy nanoparticles were synthesized using a sequential reduction method with colloidal Au to achieve a high degree of compositional control and particle size uniformity. The promotional role of Pd was examined in the oxidation of ethanol to yield acetaldehyde and the coupling product ethyl acetate. Reactivity trends indicate that both the overall rate of ethanol oxidation and the selectivity toward coupling increase with Pd doping. Rate order and activation energy trends further suggest that the promotional role of Pd does not likely originate from simple O2 dissociation and spillover but rather from the stabilization of alkoxides at Pd-Au interfaces, disproportionately increasing coupling vs simple oxidation. Infrared spectroscopy and density functional theory calculations offer further insights into Pd microstructures in the presence of various key adsorbates, suggesting that Pd can lend this promotion in an isolated state. While this state is generally unstable in the surface due to preferences for segregation into the bulk, oxygen and pathway intermediates may aid in stabilizing surface structures. These findings lay groundwork to explain selectivity and activity control in a much wider range of oxidative functionalizations and to guide further catalyst development.
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- Award ID(s):
- 2400227
- PAR ID:
- 10583812
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Journal of Catalysis
- Volume:
- 443
- Issue:
- C
- ISSN:
- 0021-9517
- Page Range / eLocation ID:
- 115942
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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