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A heterogeneously catalyzed protocol for the acceptorless dehydrogenative condensation between N,N¿-disubstituted ureas and 1,2-diols to afford imidazolones was developed. Palladium nanoaggregates stabilized onto an alumina matrix with suitable acidic properties, namely, [Pd/Al2O3], was designed and successfully applied as efficient and reusable heterogeneous nanocatalyst for this relevant transformation. The methodology developed showed its wide applicability through the synthesis of more than 25 imidazolones with moderate to good yields, reaching a turnover number (TON) of up to 19444 and a initial turnover frequency (TOF0) > 290 h¿1. The active nanostructured catalyst was fully characterized [X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), high-resolution scanning transmission electron microscopy (HR-STEM), energy-dispersive X-ray (EDX), Raman spectroscopy, temperature-programmed reduction (TPR), temperature-programmed desorption (TPD)-NH3, TPD-CO2, X-ray photoelectron spectroscopy (XPS), Brunauer¿Emmett¿Teller (BET) area], and mechanistic studies were performed. Moreover, other related Pd-based nanomaterials composed of different acidic or basic inorganic supports were synthesized and extensively compared in this reaction. These studies revealed that the presence of Pd nanoparticles with a wide range of sizes (average particle size 2.8 nm) over a metal oxide support with a high density of acid sites is a key point for the good activity of the material, ¿-Al2O3 being the optimum support. Furthermore, a Pd¿Zn cooperation effect was described for the dehydrogenative condensation of unactivated 1,2-diols, including ethylene glycol, with ureas. Two Pd¿Zn bimetallic materials ([Pd/ZnO] and [Pd(5%)¿Zn(5%)/Al2O3]) were also designed and characterized properly. These materials, as well as the [Pd/Al2O3] system in combination with catalytic amounts of ZnO, showed good activity and selectivity in the acceptorless dehydrogenative condensa

Ether derivatives have myriad applications in several areas of chemical industry and academia. Hence, the development of more effective and sustainable protocols for their production is highly desired. Among the different methodologies reported for ether synthesis, catalytic reductive alcohol etherifications with carbonyl-based moieties (aldehydes/ketones and carboxylic acid derivatives) have emerged in the last years as a potential tool. These processes constitute appealing routes for the selective production of both symmetrical and asymmetrical ethers (including O-heterocycles) with an increased molecular complexity. Likewise, ester-to-ether catalytic reductions and hydrogenative alcohol etherifications with CO to dialkoxymethanes and other acetals, albeit in less extent, have undergone important advances, too. In this Review, an update of the recent progresses in the area of catalytic reductive alcohol etherifications using carbonyl-based compounds and CO have been described with a special focus on organic synthetic applications and catalyst design. Complementarily, recent progress made in catalytic acetal/ketal-to-ether or ester-to-ether reductions and other related transformations have been also summarized.

The first general and efficient cobalt-catalyzed deoxygenative hydrogenation of amides to amines is presented. The optimal catalytic system based on a combination of [Co(NTf2)2] and (p-anisyl)triphos (L3) in the presence of [Me3SiOTf] as acidic co-catalyst facilitates the direct hydrogenation of a broad range of amides to the corresponding amines under mild conditions. A set of control experiments indicate that, after the initial reduction of the amide carboxylic group to the well-known hemiaminal intermediate, the reaction mainly proceeds through C-O bond cleavage though other pathways might be also involved to a minor extent. This journal is

Catalytic hydrogenation of amides is of great interest for chemists working in organic synthesis, as the resulting amines are widely featured in natural products, drugs, agrochemicals, dyes, etc. Compared to traditional reduction of amides using (over)stoichiometric reductants, the direct hydrogenation of amides using molecular hydrogen represents a greener approach. Furthermore, amide hydrogenation is a highly versatile transformation, since not only higher amines (obtained by C–O cleavage), but also lower amines and alcohols, or amino alcohols (obtained by C–N cleavage) can be selectively accessed by fine tuning of reaction conditions. This review describes the most recent advances in the area of amide hydrogenation using H exclusively and molecularly defined homogeneous as well as nano-structured heterogeneous catalysts, with a special focus on catalyst development and synthetic applications.

N-Alkylamines are key intermediates in the synthesis of fine chemicals, dyes, and natural products, and hence are highly valuable building blocks in organic chemistry. Consequently, the development of greener and more efficient procedures for their production continues to attract the interest of both academic and industrial chemists. Reductive procedures such as reductive amination or N-alkylation through hydrogen autotransfer by employing carbonyl compounds or alcohols as alkylating agents have prevailed for the synthesis of amines. In the last few years, carboxylic/carbonic acid derivatives and CO have been introduced as alternative and convenient alkylating sources. The safety, easy accessibility, and high stability of these reagents makes the development of new reductive transformations with them as N-alkylating agents a useful alternative to existing procedures. In this Review, we summarize reported examples of one-pot reductive N-alkylation methods that use carboxylic/carbonic acid derivatives or CO as alkylating agents.

The assumption that oxidative addition is the key step during the cross-coupling reaction of aryl halides has led to the development of a plethora of increasingly complex metal catalysts, thereby obviating in many cases the exact influence of the base, which is a simple, inexpensive, and necessary reagent for this paramount transformation. Here, a combined experimental and computational study shows that the oxidative addition is not the single kinetically relevant step in different cross-coupling reactions catalyzed by sub-nanometer Pt or Pd species, since the reactivity control is shifted toward subtle changes in the base. The exposed metal atoms in the cluster cooperate to enable an extremely easy oxidative addition of the aryl halide, even chlorides, and allow the base to bifurcate the coupling. With sub-nanometer Pd species, amines drive to the Heck reaction, carbonate drives to the Sonogahira reaction, and phosphate drives to the Suzuki reaction, while for Pt clusters and single atoms, good conversion is only achieved using acetate as a base. This base-controlled orthogonal reactivity with ligand-free catalysts opens new avenues in the design of cross-coupling reactions in organic synthesis.

La presente invención describe un procedimiento para la purificación de corrientes de etileno de interés industrial que puede comprender, al menos, las siguientes etapas: - Una primera etapa en la que la corriente de etileno con acetileno y el hidrógeno se ponen en contacto con el catalizador que contiene nanopartículas de óxido de hierro. - Una segunda etapa de calentamiento de la mezcla obtenida. - Una tercera etapa de recuperación del producto

[EN] The invention relates to a method for producing atomic aggregates of gold of less than twenty atoms, comprising at least: adding at least one acid to the solution; adding at least one solvent to the solution; adding a gold compound to the solution; and stirring said solution until the aggregates are formed, [ES] La presente invención se refiere a un procedimiento de obtención de agregados atómicos de oro de menos de veinte átomos que comprende, al menos: -añadir al menos un ácido a la disolución; -añadir al menos un disolvente a la disolución; -añadir un compuesto de oro a la disolución; y agitar dicha disolución hasta la formación de los agregados

La presente invención se refiere a un procedimiento de obtención de agregados atómicos de oro de menos de veinte átomos que comprende, al menos: - añadir al menos un ácido a la disolución; - añadir al menos un disolvente a la disolución; - añadir un compuesto de oro a la disolución; y agitar dicha disolución hasta la formación de los agregados

Small gold nanoclusters in a very narrow size distribution (1.1 ± 0.5 nm) have been stabilized onto multiwalled carbon nanotubes (MWCNT). Theoretical studies supported by XPS and 16O2/18O2 isotopic exchange experiments have shown that, on small gold nanoparticles (0.9–1.5 nm), dissociation of molecular O2 and formation of a surface oxide-like layer is energetically favorable and occurs at room temperature, while O2 recombination and desorption involves a larger activation barrier. CO titration experiments and theoretical studies demonstrate that the reactivity of the oxidized particles toward CO does not only depend on particle size but also on oxygen coverage. The oxidation–reduction process described is reversible, and the oxidized nanoparticles are active in the epoxidation of styrene with air.