New routes to Cu(I)/Cu nanocatalysts for the multicomponent click synthesis of 1,2,3-triazoles

PAVEL ABDULKIN; YANINA MOGLIE; BENJAMIN R. KNAPPETT; DAVID A. JEFFERSON; MIGUEL YUS; FRANCISCO ALONSO; ANDREW E. H. WHEATLEY

Nanoscale

Royal Society of Chemistry

Año: 2013 vol. 5 p. 342 - 359

2040-3364

An array of copper and copper?zinc based nanoparticles (NPs) have been fabricated employing a variety of polymeric capping agents. Analysis by TEM, XRPD and XPS suggests that by manipulating reagent, reductant and solvent conditions it is possible to achieve materials that are mono-/narrow disperse with mean particle sizes in the #10 nm regime. Oxidative stability in air is achieved for monometallic NPs using poly(methyl methacrylate) (PMMA) anti-agglomerant in conjunction with a variety of reducing conditions. In contrast, those encapsulated by either poly(1 vinylpyrrolidin-2-one) (PVP) or poly(4- vinylpyridine) (PVPy) rapidly show Cu2O formation, with all data suggesting progressive oxidation from Cu to Cu@Cu2O core?shell structure and finally Cu2O. Bimetallic copper?zinc systems, reveal metal segregation and the formation of Cu2O and ZnO. Catalysts have been screened in the synthesis of 1,2,3- triazoles through multicomponent azide?alkyne 1,3-dipolar cycloaddition. Whereas PMMA- and PVPycoating results in reduced catalytic activity, those protected by PVP are highly active, with quantitative triazole syntheses achieved at room temperature and with catalyst loadings of 0.03 mol% metal for Cu and CuZn systems prepared using NaH2PO2, N2H4 or NaBH4 reductants.