Layered Double Hydroxides-Supported Diisopropylamide: Synthesis, Characterization and Application in Organic Reactions

Silver Supported Nanoparticles on [Mg4 Al-LDH] as an Efficient Catalyst for the α-Alkylation of Nitriles, Oxindoles and Other Carboxylic Acid Derivatives with Alcohols

An efficient heterogeneous silver-catalyzed α-alkylation of nitriles and oxindoles using alcohols via borrowing hydrogen strategy has been developed for the first time. The active nanostructured material, namely [Ag/Mg4 Al-LDH], composed by silver nanoparticles (3-4 nm average particle size) homogeneously stabilized onto a [Mg4 Al-LDH] support with suitable Brønsted basic properties, constitutes a stable catalyst for the sustainable building of novel C-C bonds from alcohols and C-nucleophiles. By applying this catalyst, a broad range of α-functionalized nitriles and oxindoles has been accessed with good to excellent isolated yields and without the addition of external bases. Moreover, the novel silver nanocatalyst has also demonstrated its successful application to the cyclization of N-[2-(hydroxymethyl)phenyl]-2-phenylacetamides to afford 3-arylquinolin-2(1H)-ones, through a one-pot dehydrogenation and intramolecular α-alkylation. Control experiments, kinetic studies, and characterization data of a variety of [Ag/LDH]-type materials confirmed the silver role in the dehydrogenation and hydrogenation steps, while [Mg4 Al-LDH] matrix is able to catalyze condensation. Interestingly, these studies suggest as key point for the successful activity of [Ag/Mg4 Al-LDH], in comparison with other [Ag/LDH]-type nanocatalysts, the suitable acid-base properties of this material.

Layered Double Hydroxide Materials: A Review on Their Preparation, Characterization, and Applications

Layered double hydroxides (LDHs), a type of synthetic clay with assorted potential applications, are deliberated upon in view of their specific properties, such as adsorbent-specific behavior, biocompatibility, fire-retardant capacity, and catalytic and anion exchange properties, among others. LDHs are materials with two-dimensional morphology, high porosity, and exceptionally tunable and exchangeable anionic particles with sensible interlayer spaces. The remarkable feature of LDHs is their flexibility in maintaining the interlayer spaces endowing them with the capacity to accommodate a variety of ionic species, suitable for many applications. Herein, some synthetic methodologies, general characterizations, and applications of LDHs are summarized, encompassing their broader appliances as a remarkable material to serve society and address several problems viz. removal of pollutants and fabrication of sensors and materials with multifaceted useful applications in the medical, electrochemical, catalytic, and agricultural fields, among others.

Farringtonite as an efficient catalyst for linear-chain α-olefin epoxidation with aqueous hydrogen peroxide

A convenient, scalable, benign, and efficient epoxidation method based on farringtonite, without the use of transition metals, was developed for the first time.

Ultrasonic-Assisted Michael Addition of Arylhalide to Activated Olefins Utilizing Nanosized CoMgAl-Layered Double Hydroxide Catalysts

An efficient cobalt-based layered double hydroxide (LDH)-catalyzed Michael addition of an aryl halide compound onto activated olefin as a Michael acceptor is described. The synthesized catalytic materials were characterized using different techniques to investigate their physicochemical, morphological, and textural properties. The partial isomorphic substitution of magnesium by cobalt ions in the cationic sheets of the layered double hydroxide (CoMgAl-LDH) appears to be an appropriate catalyst to cause this reaction. This technique enables compound synthesis resulting from the 1,4-addition in good to excellent yields. Moreover, ultrasound was found to have beneficial effect on this reaction due to the cavitation phenomenon.

Layered double hydroxide anchored ionic liquids as amphiphilic heterogeneous catalysts for the Knoevenagel condensation reaction

In this paper, three solid base catalysts of LDH-IL-Cn (n = 4, 8, 12) were synthesized by adopting an exfoliation/assembly approach. The as-prepared catalyst showed excellent activity and selectivity for the Knoevenagel reaction in aqueous solution.

Synthesis of polycarbonate diols catalyzed by calcined hydrotalcites doped with the transition metal Ni2+

Calcined hydrotalcites doped with Ni²⁺ (HTC-Ni-T) were prepared and used as catalysts for the synthesis of polycarbonate diols (PCDLs) via transesterification between dimethyl carbonate (DMC) and 1,4-butanediol (BDO).

One pot domino reaction accessing γ-nitroesters: synthesis of GABA derivatives

γ-Nitroesters are synthesized by the one pot domino process. GABA derivatives phenibut and baclofen were readily accessed.

Synthesis of a Thermostable Polymer-supported Strongly Basic Catalyst and its Catalytic Activity

A novel strongly basic polymer-supported catalyst with guanidine groups has been synthesized and its thermal stability has been investigated. To obtain a thermally stable, cross-linked structure, guanidine groups bound to a polystyrene matrix were allowed to react in a nucleophilic manner with p-xylylene dichloride. Compared with the conventional strongly basic anion-exchange resin 201, it possesses higher thermal stability when placed in deionized water at 95°C for 60 h. This was confirmed by thermogravimetric analysis. The excellent thermal stability can be attributed to the unique structure of guanidine and the cross-linking connection mode between this base and the polymeric matrix. The obtained resin was found to efficiently catalyze Knoevenagel condensation reactions with remarkably high yields. Furthermore, the catalytic efficiency of the resin was found to remain unaffected for seven cycles, whereas that of 201 resin was reduced by 25 % owing to degradation of the strongly basic groups.

L-Arginine as a Cost-Effective and Recyclable Catalyst for the Synthesis of α,β-Unsaturated Nitriles and Ketones in an Ionic Liquid

L-Arginine catalysed the Knoevenagel condensations of aromatic, heteroaromatic and α,β-unsaturated aldehydes with malononitrile and acetylacetone to afford α,β-unsaturated nitriles and ketones. The reactions were carried out at room temperature in the ionic liquid, 1-ethyl-3-methylimidazolium ethylsulfate. Moderate to excellent yields (45–100%) were achieved. The L-arginine/ionic liquid combination was successfully recycled for five runs without significant loss of activity.