Gold nanoparticle-decorated reduced graphene oxide as a highly effective catalyst for the selective α,β-dehydrogenation of N-alkyl-4-piperidones.

Abstract

Gold nanoparticles (AuNPs) supported on reduced graphene oxide (AuNPs/rGO) were demonstrated to be a highly reactive catalyst for the selective α,β-oxidative dehydrogenation (ODH) of N-alkyl-4-piperidones, using N-methyl-, N-ethyl- and N-benzyl-4-piperidone. The substrate N-methyl-4-piperidone represents a pharmaceutically relevant system as its reaction product N-methyl-2,3-dihydropyridin-4(1H)-one is highly valuable (>1000 €·g^-1) in contrast to the inexpensive starting material (0.15 €·g^-1). Various synthesis methods were employed to prepare AuNPs supported on different carbon materials, including reduced graphene oxide (rGO), activated carbon (AC), and carbon black (CB), to investigate the influence of the carbon support on the catalyst performance. As stabilizing agents for the AuNPs, citrate (Cit) and the polyoxometallate [SiW₉O₃₄]^10- (SiW₉) were used. Among the tested catalysts, the rGO-supported ones, Au-Cit/rGO, Au-SiW₉/rGO, and Au@SiW₉/rGO exhibited the highest catalytic activity for the selective oxidation reaction despite containing the lowest gold loading. These findings highlight the exceptional performance of rGO as a support for AuNP catalysts and provide valuable insights for designing efficient Au-based systems for the dehydrogenation of β-N-substituted saturated ketones and other fine chemical applications.