The usage of gold, copper and silver in the synthesis of heterocycles is discussed. An exploration of the mechanism of the reactions with regard to substrate activation and reaction pathways is ...presented.
Central nervous system diseases are often associated with somatosensory dysfunction. Somatosensory deficits affect postural and motor control. However, postural and motor control can be improved by ...using visual and vestibular sensory information, and by emphasizing somatosensory information. An understanding of somatosensory function should distinguish it from other dysfunctions.
Organic synthesis using gold has gained tremendous attention in last few years, especially heterogeneous gold catalysis based on gold nanoparticles has made its place in almost all organic reactions, ...because of the robust and green nature of gold catalysts. In this context, gold nanopore (AuNPore) with a 3D metal framework is giving a new dimension to heterogeneous gold catalysts. Interestingly, AuNPore chemistry is proving better than gold nanoparticles based chemistry. In this review, along with recent advances, major discoveries in heterogeneous gold catalysis are discussed.
Heterocyclic compounds are worthy of attention for many reasons; chief among them are their biological activities, and many drugs are heterocycles. Therefore, organic chemists have been making ...extensive efforts to produce these heterocyclic compounds by developing new and efficient synthetic transformations.
Aromatic functionalizations are of current interest and importance in organic chemistry, recent transition‐metal catalyzed reactions can transform inert C−H bond into C−X (X=C, O, N, etc.) bonds, ...greatly enriching aromatic chemistry and related fields. Some well‐known palladium‐containing intermediates such as palladacycles and allylpalladium intermediates play an important role in organic conversions. Similar with allyl group, benzyl group also possesses the capability of stabilizing palladium through η3‐binding. In the process of the formation of benzyl palladium intermediate, there is a transition state of dearomatization. Therefore, it is a challenging and meaningful research topic to seize these aromatic destruction intermediates, realize selective functionalization reaction on aromatic ring via them, and inhibit the formation of traditional benzylated products. Herein, we summarized the recent efforts on expanding the synthetic utility, as well as exploring the mechanism in aromatic functionalization via reactive benzyl palladium intermediates. We envision that the transformation via benzyl palladium intermediates will help promote the development in the field of palladium–catalyzed aromatic regioselective functionalization.
Distinct from inert bulk gold, nanoparticulate gold has been found to possess remarkable catalytic activity towards oxidation reactions. The catalytic performance of nanoparticulate gold strongly ...depends on size and support, and catalytic activity usually cannot be observed at characteristic sizes larger than 5 nm. Interestingly, significant catalytic activity can be retained in dealloyed nanoporous gold (NPG) even when its feature lengths are larger than 30 nm. Here we report atomic insights of the NPG catalysis, characterized by spherical-aberration-corrected transmission electron microscopy (TEM) and environmental TEM. A high density of atomic steps and kinks is observed on the curved surfaces of NPG, comparable to 3-5 nm nanoparticles, which are stabilized by hyperboloid-like gold ligaments. In situ TEM observations provide compelling evidence that the surface defects are active sites for the catalytic oxidation of CO and residual Ag stabilizes the atomic steps by suppressing {111} faceting kinetics.
We achieved the lowest-ever transmission losses of 0.1419 dB/km at 1560 nm wavelength and 0.1424 dB/km at 1550 nm in a Ge-free silica-core optical fiber. It was an improvement by 4 mdB/km from the ...previous record realized in 2015. The Ge-free silica core included fluorine co-doping, which helps to reduce disorder in the microscopic glass network structure that causes Rayleigh scattering loss without a significant increase in waveguide imperfection loss. A two-layered polymer coating with an inner layer having lower elastic modulus than before also contributed to the ultralow loss without influence of microbending loss increase even with an enlarged effective area of 147 μm2. The present fiber with ultralow loss and a large effective area benefits an ultralong haul optical transmission system including transoceanic submarine cable systems. We estimate system performance based on the fiber figure of merit theory that the present fiber enables a 0.10 bit/s/Hz increase in spectral efficiency or 7% reduction in the number of repeaters, compared to the previous record-loss fiber.
Nanoporous metal (MNPore) skeleton catalysts have attracted increasing attention in the field of green and sustainable heterogeneous catalysis owing to their unique three‐dimensional nanopore ...structural features. In general, MNPores are fabricated through chemical or electrochemical corrosive dealloying of monolithic alloys. The dealloying process produces various MNPores with an open nanoporous network structure by formation of concave and convex hyperboloid‐like ligaments. The large surface‐to‐volume ratio compared to bulk metals and high density of steps and kinks on ligaments of the unsupported MNPores make them promising heterogeneous catalyst candidates for highly active and selective molecular transformations. In this context, a variety of heterogeneous catalytic reactions using MNPores as nanocatalysts under gas‐ and liquid‐phase conditions were developed over the last decade. In addition, the bulk metallic shape and mechanistic rigidity of the MNPore catalysts make the processes of catalyst recovery and reuse more facile and greener. This Minireview mainly focuses on the catalytic performance of nanoporous Au, Pd, Cu, and AuPd with respect to the achievements on catalytic applications in various molecular transformations.
Precious holes to transform: Nanoporous metals prepared by dealloying methods have emerged as green and sustainable heterogeneous catalysts because of their high surface area, high catalytic activity and selectivity, facile recovery method, and high reusability. This Minireview describes, by highlighting recent advances, remarkable catalytic performances of nanoporous gold, palladium, copper, and AuPd alloy on a variety of organic molecular transformations in the liquid phase.
An efficient and general Au(III)-catalyzed tandem reaction, heteroenyne metathesis and Nazarov cyclization, of 1,3-enynyl ketones to produce fused tri- and tetracyclic enones has been developed. The ...products were formed with excellent regioselectivity of the double bond position and with very high diastereoselectivities. In this reaction, the Au(III) catalyst exhibits dual roles for activating both alkynes and carbonyls.
