Organic transformations catalyzed by gold nanoparticles supported on functionalized silica

Recently, we presented the preparation, without any need of additional reducing and/or stabilizing agents, of a variety of stable silica-supported gold nanoparticles (AuNPs) by using as the only reactants an aqueous solution of HAuCl4 and different functionalized-silica supports. We started using commercial polyethyleneimine-functionalized silica beads (SiO2-PEI)1 and we went on preparing silica nanoparticles with alkynyl carbamate moieties (SiO2-Yne, Fig. 1)2 later post-functionalized by thiol-yne radical chemistry to give the amino-sulfide-branched silica (SiO2@AeThio).3 Fig. 1 Alkyne- and amino-sulfide-modified silica nanoparticles SiO2@Yne and SiO2@AeThio. All the AuNPs-modified systems are catalytically active and possess a remarkable activity in the reduction of 4-nitrophenol to 4-aminophenol. We now present the latest results obtained with these catalysts in the field of selective catalytic oxidation of alcohols in aqueous medium via continuous-flow chemistry. References 1. “Straightforward Synthesis of Gold Nanoparticles Supported on Commercial Silica-Polyethyleneimine Beads”, S. Fazzini , D. Nanni , B. Ballarin , M. C. Cassani , M. Giorgetti , C. Maccato, A. Trapananti , G. Aquilanti, S. I. Ahmed, J. Phys. Chem. C, 2012, 116, 25434−25443. 2. "Novel Synthesis of Gold Nanoparticles Supported on Alkyne-Functionalized Nanosilica", S. Fazzini, M.C. Cassani, B. Ballarin, E. Boanini, J.-S. Girardon, A.-S. Mamede, A. Mignani, D. Nanni, J. Phys. Chem. C, 2014, 118, 24538-24547. 3. “Functionalizaton of Silica through Thiol-Yne Radical Chemistry: a Catalytic System based on Gold Nanoparticles Supported on Amino-Sulfide-Branched Silica” M. C. Cassani, B. Ballarin, D. Barreca, E. Boanini, E. Bonansegna, G. Carraro, S. Fazzini, A. Mignani, D. Nanni, D. Pinelli, RSC Adv., 2016, 6, 25780-25788