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[reaction: see text] Treatment of tethered alkynyl enynones 8, in which a carbon chain is attached to the carbonyl group, with a catalytic amount of AuBr(3) in (ClCH(2))(2) gave the naphthyl ketones 9 in good to high yields (top-down approach). Analogously, the AuBr(3)-catalyzed benzannulations of 10, in which a carbon tether is extended from the alkynyl terminus, also proceeded smoothly, and the cyclized naphthyl ketones 11 were obtained in high yields (bottom-up approach). Similarly, when two kinds of tethered alkenyl enynones 12 and 14 were treated with Cu(OTf)(2) catalyst, the corresponding dihydronaphthyl ketone products 13 and 15 were obtained in high yields, respectively. The present formal [4 + 2] intramolecular cycloaddition proceeds most probably through the coordination of the triple bond at the ortho position of substrates to Lewis acids, the formation of benzopyrylium ate complex 16 via the nucleophilic addition of the carbonyl oxygen atom, the reverse electron demand type Diels-Alder addition of the tethered alkynes or alkenes to the ate complex, and subsequent bond rearrangement.

Goldene Aussichten: Nanoporöses Gold (AuNPore) zeigt eine bemerkenswerte katalytische Aktivität für die Oxidation von Organosilanen mit Wasser. Der Katalysator lässt sich leicht zurückgewinnen und wiederholt verwenden, ohne dass Verluste durch Auflösung oder Aktivitätseinbußen auftreten.

Aerobic oxidation of alcohols in the liquid phase proceeded smoothly in the presence of nanoporous gold catalyst. The catalyst is reusable multiple times without leaching and loss of the catalytic activity. The reaction was applied successfully to a flow system. Adsorptions of O(2) and 1-phenylethanol into the AuNPore were confirmed by TDS analysis.

Nanoporous copper (CuNPore) catalysts with tunable nanoporosity were fabricated from Cu 30 Mn 70 alloy by controlling the de-alloying temperature under free corrosion conditions. The tunable nanoporosity of CuNPore led to a significant enhancement of catalytic activity in click chemistry without using any supports and bases. Characterization of CuNPore surface, high reusability, leaching experiment, and formation of nanostructured copper acetylide revealed that the click reaction occurred at the catalyst surface.Keywords: click reaction; heterogeneous catalysis; high reusability; nanoporous copper catalyst; tunable nanoporosity Nanoporous metals are promising materials for catalysis, [1][2][3] sensing, [4] and actuation [5] applications due to their interesting structural, optical and surface properties. In spite of the growing number of studies on various applications of nanoporous metals, the catalytic properties in chemical reactions are still less explored, although the interesting features of nanoporous metals make them potentially attractive candidates for new heterogeneous catalysts; [1][2][3] the three-dimensional, open-pore network structures and metal ligaments allow the transport of molecules and ions, a high surface-to-volume ratio in comparison with bulk metals results in outstanding catalytic efficiency; furthermore, the potentially high reusability and rather simple work-up are favorable for practical synthetic methodology. Moreover, in contrast to the supported nanoparticles (NPs) catalyst, a nanoporous metal without supports should be a challenging catalyst system to understand the relevant catalytic mechanism more easily and to extend the catalytic application widely by elimination of the support effect problems and relaxation of aggregation. In this regard, we have focused on the study of the catalytic properties of unsupported nanoporous metals in organic molecular transformations under liquid-phase conditions.