Hydrogenation of Azides over Copper Nanoparticle Surface Using Ammonium Formate in Water

Bypassing Sulfonyl Halides: Synthesis of Sulfonamides from Other Sulfur-Containing Building Blocks

This review disclosed synthetic approaches to sulfonyl amides from non-sulfonyl halogenated precursors. Known methods were systematized into groups and subgroups according to the type of starting organosulfur compound. Thiols, disulfides, and sulfonamides form a group of S(II)-containing precursors, which are used in oxidative amination reactions. An important and versatile group for oxidative amination is represented with S(IV)-containing compounds, i. e., sufinates, sulfinamides, DMSO, N-sulfinyl-O-(tert-butyl)hydroxylamine, etc. A series of S(VI)-containing precursors for amination reactions (except sulfonyl halides) include sulfonic acids, sulfonyl azides, thiosulfonates, and sulfones. All approaches are represented with the most prominent examples of the resulting sulfonamides, which could be obtained in high yields mostly via short reaction sequences. Promising electrochemical methods for the preparation of sulfonamides from thiols, disulfides, sulfonamides, sulfinic acid derivatives, and dimethyl sulfoxide under mild and green conditions are also highlighted.

Recent advances in nanoparticles towards sustainability and their application in organic transformations in aqueous media

Nanoparticles (NPs) play a crucial role in organic transformation and are becoming increasingly attractive in the field of catalysis as they show good catalytic activity in organic as well as aqueous media. Numerous NPs have been utilized for several organic transformations in aqueous media, which have led to dedicated efforts for the complete coverage of the application of metal, metal oxide, bimetallic and supported NPs in water-mediated organic transformations in the last decades. This review aims to provide current highlights on the application of various types of metal NPs for organic transformations in aqueous media. The remarkable benefits associated with the catalytic application of NPs in water allows for various transformations to be performed under very mild and green conditions. Lastly, the author's perspectives are briefly considered, including future developments and crucial challenges in the ever-growing field of nanocatalysis.

Copper nanoparticles catalyzed carbon–heteroatom bond formation and synthesis of related heterocycles by greener procedures

A variety of procedures for the carbon–nitrogen, carbon–oxygen, carbon–sulfur and carbon–selenium bond formation using copper nanoparticles in greener conditions have been highlighted. The synthesis of several heterocyclic compounds of biological importance has also been reported using these protocols.

Metal-Free, Rapid, and Highly Chemoselective Reduction of Aromatic Nitro Compounds at Room Temperature

In this study, we developed a metal-free and highly chemoselective method for the reduction of aromatic nitro compounds. This reduction was performed using tetrahydroxydiboron [B₂(OH)₄] as the reductant and 4,4'-bipyridine as the organocatalyst and could be completed within 5 min at room temperature. Under optimal conditions, nitroarenes with sensitive functional groups, such as vinyl, ethynyl, carbonyl, and halogen, were converted into the corresponding anilines with excellent selectivity while avoiding the undesirable reduction of the sensitive functional groups.

1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU)-promoted reduction of azides to amines under metal-free conditions

A simple and novel metal-free reduction of azides to amines in the presence of DBU is reported. This DBU-promoted transformation features good functional group tolerance and high chemo-selectivity.

Heterogeneous photocatalysis of azides: extending nitrene photochemistry to longer wavelengths

The photodecomposition of azides to generate nitrenes usually requires wavelengths in the <300 nm region. In this study, we show that this reaction can be readily performed in the UVA region (368 nm) when catalyzed by Pd-decorated TiO2. In aqueous medium the reaction leads to amines, with water acting as the H source; however, in non-protic and non-nucleophilic media, such as acetonitrile, nitrenes recombine to yield azo compounds, while azirine-mediated trapping occurs in the presence of nucleophiles. The heterogeneous process facilitates catalyst separation while showing great chemoselectivity and high yields.

Synthesis of Z-Enamides through Heterogeneous Gold-Catalyzed Stereoselective Hydrogenation of Ynamides

A facile synthesis of Z-enamides via heterogeneous Au/TiO₂ catalyzed stereoselective hydrogenation of ynamides has been developed. Easy to handle and inexpensive ammonium formate was used as the hydrogen source, and Z-enamides were formed in a highly stereoselective manner. The commercially available gold nanoparticle catalyst could be recycled multiple times without a significant loss of activity.

A Highly Efficient Ga(OTf)3/KI-Catalysed Transformation of aryl azides to aryl amines using low catalyst loading

A highly proficient transformation of aryl azides to aryl amines under Ga(OTf)3/KI catalysis is described.

Design of Copper-Based Bimetallic Nanoparticles for Carbon Dioxide Adsorption and Activation

Cu-based nanoparticles (NPs) are promising candidates for the catalytic hydrogenation of CO₂ to useful chemicals because of their low cost. However, CO₂ adsorption and activation on Cu is not feasible. In this work we demonstrate a computational framework that identifies Cu-based bimetallic NPs able to adsorb and activate CO₂ based on DFT calculations. We screen a series of heteroatoms on Cu-based NPs based on their preference to occupy a surface site on the NP and to adsorb and activate CO₂ . We revealed two descriptors for CO₂ adsorption on the bimetallic NPs, the heteroatom (i) local d-band center and (ii) electropositivity, which both drive an effective charge transfer from the NP to CO₂ . We identified the CuZr bimetallic NP as a candidate nanostructure for CO₂ adsorption and showed that although the Zr sites can be oxidized because of their high oxophilicity, they are still able to adsorb and activate CO₂ strongly. Importantly, our computational results are verified by targeted synthesis, characterization, and CO₂ adsorption experiments that demonstrate that i) Zr segregates on the surface of Cu, ii) Zr is oxidized to form a bimetallic mixed CuZr oxide catalyst, which iii) can strongly adsorb CO₂ , whereas Cu NPs cannot. Overall our work highlights the importance of the generation of binding sites on a NP surface based on (catalyst) stability and electronic structure properties, which can lead to the design of more effective CO₂ reduction catalysts.

Visible-light-driven Efficient Photocatalytic Reduction of Organic Azides to Amines over CdS Sheet-rGO Nanocomposite

CdS sheet-rGO nanocomposite as a heterogeneous photocatalyst enables visible-light-induced photocatalytic reduction of aromatic, heteroaromatic, aliphatic and sulfonyl azides to the corresponding amines using hydrazine hydrate as a reductant. The reaction shows excellent conversion and chemoselectivity towards the formation of the amine without self-photoactivated azo compounds. In the adopted strategy, CdS not only accelerates the formation of nitrene through photoactivation of azide but also enhances the decomposition of azide to a certain extent, which entirely suppressed formation of the azo compound. The developed CdS sheet-rGO nanocomposite catalyst is very active, providing excellent results under irradiation with a 40 W simple household CFL lamp.

Copper-mediated reduction of azides under seemingly oxidising conditions: catalytic and computational studies

The reduction of aryl azides in the presence of water and air and without an obvious reducing agent is reported.

Catalytic Organic Reactions in Water toward Sustainable Society

Traditional organic synthesis relies heavily on organic solvents for a multitude of tasks, including dissolving the components and facilitating chemical reactions, because many reagents and reactive species are incompatible or immiscible with water. Given that they are used in vast quantities as compared to reactants, solvents have been the focus of environmental concerns. Along with reducing the environmental impact of organic synthesis, the use of water as a reaction medium also benefits chemical processes by simplifying operations, allowing mild reaction conditions, and sometimes delivering unforeseen reactivities and selectivities. After the "watershed" in organic synthesis revealed the importance of water, the development of water-compatible catalysts has flourished, triggering a quantum leap in water-centered organic synthesis. Given that organic compounds are typically practically insoluble in water, simple extractive workup can readily separate a water-soluble homogeneous catalyst as an aqueous solution from a product that is soluble in organic solvents. In contrast, the use of heterogeneous catalysts facilitates catalyst recycling by allowing simple centrifugation and filtration methods to be used. This Review addresses advances over the past decade in catalytic reactions using water as a reaction medium.

5-O-Mycaminosyltylonolide antibacterial derivatives: design, synthesis and bioactivity

Tylosin is a 16-membered macrolide broad-spectrum antibiotic that has an important role in veterinary medicine, active against Gram-positive and a restricted range of Gram-negative bacteria. We synthesized 15 types of tylosin-related derivatives by chemical modification and evaluated them against mastitis pathogens. Among them, 20-deoxy-20-{N-methyl-N-[1-(3-quinolyl)-1H-1,2,3-triazol-4-yl]methylamino}-5-O-mycaminosyltylonolide 2f and 20-deoxy-20-{N-benzyl-N-[1-(3-quinolyl)-1H-1,2,3-triazol-4-yl]methylamino}-5-O-mycaminosyltylonolide 2k were found to not only expand their antibacterial impact to include Gram-negative bacteria, such as Escherichia coli and Klebsiella pneumoniae, but also to retain or increase antibacterial activity against Gram-positive bacteria, such as Staphylococcus aureus and Streptococcus uberis in comparison with the parent tylosin.

Au/TiO2 catalyzed reductive amination of aldehydes and ketones using formic acid as reductant

The combination of commercial easily available Au/TiO₂ as catalyst and cost-effective formic acid as reductant was able to render reductive amination of various carbonyl compounds.

Supported gold nanoparticles catalyzed cis-selective semihydrogenation of alkynes using ammonium formate as the reductant

TiO₂ supported gold nanoparticles with a low loading (0.5 mol%) are able to semihydrogenate non-fluorinated and gem-difluorinated alkynes to cis-alkenes with high selectivity, using cost-effective and easy-to-handle ammonium formate as the reductant.

Iridium-catalyzed transfer hydrogenation of nitroarenes to anilines

An [Ir(cod)Cl]₂/phenanthroline catalytic system shows high activity for the reduction of nitroarenes to aminoarenes using 2-propanol as a hydrogen donor.

Nano Cu-catalyzed efficient and selective reduction of nitroarenes under combined microwave and ultrasound irradiation

In situ preparation of copper nanoparticles from a copper acetate precursor and its application as an efficient catalyst for the selective reduction of aromatic nitro compounds with hydrazine hydrate under combined microwave and ultrasound irradiation were described in detail. The results reveal the synergetic effect of microwave and ultrasound on the synthesis of copper nanoparticles, and formation of various amino derivatives.

Quinoline and phenanthroline preparation starting from glycerol via improved microwave-assisted modified Skraup reaction

An efficient “green” modified Skraup reaction in neat water was developed using inexpensive, abundant and environmentally-friendly glycerol under microwave irradiation conditions.

Self-assembly and applications of ultraconcentrated nanoparticle solutions

We demonstrate a highly efficient method for concentrating, purifying and separating gold nanoparticles. The method relies on localized density gradients that can be formed at an aqueous | organic phase interface. We show that this method is able to concentrate aqueous gold nanoparticles to the point where confinement leads to variable interparticle separations. Furthermore, the physical properties of the resulting solution are drastically altered when compared to water. For example, densities higher than 4.5 g/cm(3) could be generated without nanoparticle aggregation. As far as we are aware, this is one of the highest reported densities of an aqueous solution at room temperature. Finally, the compositions of the solutions generated are highly dependent on parameters such as particle size and background analyte making this technique highly advantageous for the separation of multimodal NP populations and chemical purification, with 99.5% and >99.9% efficiency, respectively.