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Gold-catalyzed intermolecular oxidations of internal alkynes are achieved with high regioselectivities by using 8-alkylquinoline N-oxides as oxidants and in the absence of acid additives. The reaction has allowed [alpha],[beta]-unsaturated carbonyls to be masked as propargyl moieties, which has provided a practical solution to compatibility issues with these functional groups encountered in syntheses of complex structures.

A complex of [[Ir(OMe)(cod)].sub.2] and 4,4-di-tert-butyl-2,2-bipyridine (dtbpy) has catalyzed the Z-selective, dehydrative silylation of terminal alkenes, but not 1,2-disubstituted alkenes, with triethylsilane or benzyldimethylsilane in THF. Yields and Z-stereoselectivity are improved by 2-norbornene, whereas [alpha],[beta]-unsaturated esters are unreactive and the reaction has proceeded through a Heck-type mechanism.

A CuI-catalyzed domino process for the assembly of 2,3-disubstituted benzofurans from 1-bromo-2-iodobenzenes and [beta]-keto esters is presented.

Hollow Au-Cu2O core-shell nanoparticles were synthesized by using hollow gold nanoparticles (HGNs) as the plasmon-tailorable cores to direct epitaxial growth of Cu2O nanoshells. The effective geometry control of hollow Au-Cu2O core-shell nanoparticles was achieved through adjusting the HGN core sizes, Cu2O shell thicknesses, and morphologies related to structure-directing agents. The morphology-dependent plasmonic band red-shifts across the visible and near-infrared spectral regions were observed from experimental extinction spectra and theoretical simulation based on the finite-difference time-domain method. Moreover, the hollow Au-Cu2O core-shell nanoparticles with synergistic optical properties exhibited higher photocatalytic performance in the photodegradation of methyl orange when compared to pristine Cu2O and solid Au-Cu2O core-shell nanoparticles under visible-light irradiation due to the efficient photoinduced charge separation, which could mainly be attributed to the Schottky barrier and plasmon-induced resonant energy transfer. Such optical tunability achieved through the hollow cores and structure-directed shells is of benefit to the performance optimization of metal-semiconductor nanoparticles for photonic, electronic, and photocatalytic applications. [ABSTRACT FROM AUTHOR]

Gold-catalyzed intramolecular oxidation of terminal alkynes with an arenesulfinyl group as the tethered oxidant is a reaction of high impact in gold chemistry, as it introduced to the field the highly valued concept of gold carbene generation via alkyne oxidation. The proposed intermediacy of α-oxo gold carbenes in these reactions, however, has never been substantiated. Detailed experimental studies suggest that the involvement of such reactive intermediates in the formation of dihydrobenzothiepinones is highly unlikely. Instead, a [3,3]-sigmatropic rearrangement of the initial cyclization intermediate offers a reaction path that can readily explain the high reaction efficiency and the lack of sulfonium formation. With internal alkyne substrates, however, the generation of a gold carbene species becomes competitive with the [3,3]-sigmatropic rearrangement. This reactive intermediate, nevertheless, does not proceed to afford the Friedel–Crafts-type cyclization product. Extensive density functional theory studies support the mechanistic conclusion that the cyclized product is formed via an intramolecular [3,3]-sigmatropic rearrangement instead of the previously proposed Friedel–Crafts-type cyclization. With the new mechanistic insight, the product scope of this versatile formation of mid-sized sulfur-containing cycloalkenones has been expanded readily to various dihydrobenzothiocinones, a tetrahydrobenzocyclononenone, and even those without the entanglement of a fused benzene ring. Besides gold, Hg(OTf)2 can be an effective catalyst, thereby offering a cheap alternative for this intramolecular redox reaction. [ABSTRACT FROM AUTHOR]

CuI-catalyzed coupling of 1-bromo-2-iodobenzenes with β-keto esters in THF at 100 °C leads to 2,3-disubstituted benzofurans. This domino transformation involves an intermolecular C-C bond formation and a subsequent intramolecular C-O bond formation process. Benzofurans with different substituents at the 5- and 6-position are accessible by employing the corresponding 1-bromo-2-iodobenzenes. [ABSTRACT FROM AUTHOR]

Gold-catalyzed intermolecular oxidations of internal alkynes have been achieved with high regioselectivities using 8-alkylquinoline N-oxides as oxidants and in the absence of acid additives. Synthetically versatile α,β-unsaturated carbonyls are obtained in good to excellent yields and with excellent Eselectivities. A range of functional groups such as THP, MOMO, N3, OTBS, and N-Boc are tolerated. This reaction allows α,βunsaturated carbonyls to be masked as propargyl moieties, thus offering a practical solution to compatibility issues with these functional groups likely encountered in syntheses of complex structures. [ABSTRACT FROM AUTHOR]

CuI-catalyzed coupling of 2-halobenzylamines with β-keto esters or 1,3-diketones in i-PrOH under the action of K 2CO 3produced 1,2-dihydroisoquinolines as the coupling/condensative cyclization products, which underwent smooth dehydrogenation under air atmosphere to afford substituted isoquinolines. [ABSTRACT FROM AUTHOR]