Catalysts In Organic Synthesis Research Articles

Chiral Carboxylic Acids as Organic Catalysts for Asymmetric Reactions

AbstractCarboxyl groups are frequently found in both natural products with proven bioactivities and small functional molecules with significant synthetic applications. Carboxylic acids are therefore one class of the most critical and easily accessible catalysts in organic synthesis. Herein, a brief overview of chiral carboxylic acid‐catalyzed asymmetric reactions is provided. Typical reactions and mechanisms are systematically discussed. We also provide our own perspectives on the future development within this research field based on our comprehensive understanding of the carboxylic acid‐promoted organocatalytic reactions.

Colloidal and nanosized catalysts in organic synthesis: XXV. Reductive alkylation of nitroarenes with alcohols in the presence of a supported copper nanocatalyst

Using a modified deposition-precipitation method followed by sodium borohydride reduction of the precursor deposited on γ-Al2O3, copper-containing catalysts were obtained, which allow the continuous process of reductive alkylation of nitroarenes with alkanols at 200-220°C and atmospheric pressure of hydrogen with mono- N -alkylated products selectivity up to 100% and complete conversion of nitroarenes.

Colloidal and Nanosized Catalysts in Organic Synthesis: XXV. Reductive Alkylation of Nitroarenes with Alcohols in the Presence of a Supported Copper Nanocatalyst

Colloidal and Nanosized Catalysts in Organic Synthesis: XXV. Reductive Alkylation of Nitroarenes with Alcohols in the Presence of a Supported Copper Nanocatalyst

Gallium(III)- and Indium(III)-Containing Ionic Liquids as Highly Active Catalysts in Organic Synthesis.

The chemical industry still requires development of environmentally friendly processes. Acid-catalysed chemical processes may cause environmental problems. Urgent need to replace conventional acids has forced the search for sustainable alternatives. Metal-containing ionic liquids have drawn considerable attention from scientists for many years. These compounds may exhibit very high Lewis acidity, which is usually dependent on the composition of the ionic liquid with the particular content of metal salt. Therefore, metal-containing ionic liquids have found a lot of applications and are successfully employed as catalysts, co-catalysts or reaction media in various fields of chemistry, especially in organic chemistry. Gallium(III)- and indium(III)-containing ionic liquids help to transfer the remarkable activity of metal salts into even more active and easier-to-handle forms of ionic liquids. This review highlights the wide range of possible applications and the high potential of metal-containing ionic liquids with special focus on Ga(III) and In(III), which may help to outline the framework for further development of the presented research topic and synthesis of new representatives of this group of compounds.

Carbon Quantum Dots: Synthesis, Structure, Properties, and Catalytic Applications for Organic Synthesis

Carbon quantum dots (CQDs), also known as carbon dots (CDs), are novel zero-dimensional fluorescent carbon-based nanomaterials. CQDs have attracted enormous attention around the world because of their excellent optical properties as well as water solubility, biocompatibility, low toxicity, eco-friendliness, and simple synthesis routes. CQDs have numerous applications in bioimaging, biosensing, chemical sensing, nanomedicine, solar cells, drug delivery, and light-emitting diodes. In this review paper, the structure of CQDs, their physical and chemical properties, their synthesis approach, and their application as a catalyst in the synthesis of multisubstituted 4H pyran, in azide-alkyne cycloadditions, in the degradation of levofloxacin, in the selective oxidation of alcohols to aldehydes, in the removal of Rhodamine B, as H-bond catalysis in Aldol condensations, in cyclohexane oxidation, in intrinsic peroxidase-mimetic enzyme activity, in the selective oxidation of amines and alcohols, and in the ring opening of epoxides are discussed. Finally, we also discuss the future challenges in this research field. We hope this review paper will open a new channel for the application of CQDs as a catalyst in organic synthesis.

Synthesis of Oxygen and Nitrogen Containing Heterocycles using Zirconium Dioxide/Mixed Oxide Nanoparticles as Reusable Green Catalysts: A Comprehensive Update

Abstract: The remarkable improvements in organic synthesis facilitated by zirconium dioxide- based nanoparticles are updated and summarized in this review. The ZrO2 acts as a versatile heterogeneous nanocatalyst and is used in various elementary organic reactions and many multicomponent reactions. The employment of these catalysts in organic synthesis leading to bio-active scaffolds provides the opportunity to carry out the reactions using facile synthetic protocol under mild environments that furnish the equivalent products in high yields and shorter reaction times. According to reports in the literature, ZrO2-based catalysts were removed from the reaction mixture and recycled many times.

Efficient synthesis of symmetrically substituted pyridines and substituted alkenes through green and heterogeneous catalysis with zinc phosphate.

This study presents a new environmentally sustainable catalytic method for the synthesis of symmetrically substituted pyridine derivatives and substituted alkene derivatives using zinc phosphate (Zn3(PO4)2·4H2O) as a non-toxic and green heterogeneous catalyst. The catalytic support was prepared by a co-precipitation method, and it was applied for the first time as a heterogeneous catalyst in organic synthesis. Trisubstituted pyridine derivatives were prepared with excellent yields (82-94%) via a three-component, one-pot synthesis of aromatic aldehydes, substituted acetophenones, and ammonium acetate in the presence of 0.4 mol% of Zn3(PO4)2·4H2O using an ethanol/water (4/1) mixture as the solvent, while substituted alkenes were synthesized with up to 90% yield using the prepared catalyst. The experimental results demonstrate the efficiency of these new catalytic syntheses that present various advantages such as short reaction times, excellent yields, and an environmentally friendly profile.

Research Progress in Application of Lignin and Its Derivatives Supported Metal Catalysts in Organic Synthesis

Research Progress in Application of Lignin and Its Derivatives Supported Metal Catalysts in Organic Synthesis

Deep eutectic solvents as reusable catalysts and promoter for the greener syntheses of small molecules: Recent advances

Deep eutectic solvents (DESs) are significant environmentally benign media in the field of green chemistry. They are known not only for their inexpensive nature, biodegradability, non-toxicity, and bioavailability, but also for recyclability and their ease of preparation and purification. DESs are made up of hydrogen bond donor substituents (such as urea, carboxylic acid, glycerol, metals, etc.) and hydrogen bond acceptor substituents such as halide salts; they have a lower melting point than each substituent comprising the mixture. DESs find applications in biotransformation, gas separation, biomass valorization, electrochemistry, extraction, and dissolution process as well as in material chemistry and other assorted fields of chemistry. Interestingly, DESs fulfil a unique dual role as green solvents, promoters and catalysts in organic syntheses. Thus, it is noteworthy that chemical progresses and transformation with external catalysts in cross-coupling reactions, oxidations and reductions are not covered in this overview. This review mostly focuses on leading-edge applications of DES as a reusable catalyst in the expeditious synthesis of assorted small molecules central in the assembly of broad-spectrum pharmaceuticals, and total synthesis of common natural products.

Albumin-catalysed synthesis of flavanones

Flavanones are a family of phytochemicals that have regained importance over the last decade due to their diverse biological activity. The conventional building of the flavanone skeleton is accomplished through a Claisen-Schmidt condensation followed by an intramolecular oxa-Michael addition, but the involved strong basic pH favours side reactions and affects flavanone yield. This work presents a mild access to flavanones based on a sustainable catalyst, bovine serum albumin (BSA), which is a promiscuous protein. BSA catalysed the reaction between a set of 2 ´ -hydroxyacetophenones and benzaldehydes in methanol at 60 °C to give the corresponding flavanones in 58–90% conversions. Experiments showed that BSA promotes the Claisen-Schmidt step as well as accelerates the subsequent oxa-Michael addition. Besides, BSA-catalysed reaction of acetophenone and benzaldehyde was studied, which afforded the Michael adduct 1,3,5-triphenylpentane-1,5-dione (85% conversion). On the whole, the herein reported results expand the potential of BSA as a mild and sustainable catalyst in organic synthesis.

Fluorescence-based measurement of the Lewis acidities of lanthanide triflates in solution

Despite the prominence of rare-earth complexes to act as Lewis acid catalysts in organic synthesis, the comprehensive measure of the Lewis acid strength of such compounds has yet to be performed due to incompatibilities with existing methods. We report our results in measurement of a sequence of lanthanide triflates via our recently established fluorescent Lewis adduct (FLA) method. The persistence in solution of these Lewis acids as solvated coordination complexes is accurately measurable by the FLA method. However, several of the rare-earth species exhibit fluorescence quenching, which may potentially inhibit the measurement. Nevertheless, meaningful FLA measurements were still possible, and the results correspond to both periodic trends and were even consistent with previous correlated reported data.

Role of catalyst in organic synthesis

Catalyst is a common word that comes across while studying chemistry especially while learning about chemical reactions. While some of the chemical reactions occur quickly, some take a long time and require extra materials or effort. In Chemistry, catalysts are defined as those substances which alter the rate of reaction by changing the path of reaction. Most of the time a catalyst is used to speed up or increase the rate of the reaction. However, if we go to a deeper level, catalysts are used to break or rebuild the chemical bonds between the atoms which are present in the molecules of different elements or compounds. In essence, catalysts encourage molecules to react and make the whole reaction process easier and efficient. The present review focuses on history, types and role of catalysis in organic reaction.

Zirconium-Based Catalysts in Organic Synthesis.

Zirconium is a silvery-white malleable and ductile metal at room temperature with a crustal abundance of 162ppm. Its compounds, showing Lewis acidic behavior and high catalytic performance, have been recognized as a relatively cheap, low-toxicity, stable, green, and efficient catalysts for various important organic transformations. Commercially available inorganic zirconium chloride was widely applied as a catalyst to accelerate amination, Michael addition, and oxidation reactions. Well-designed zirconocene perfluorosulfonates can be applied in allylation, acylation, esterification, etc. N-Chelating oganozirconium complexes accelerate polymerization, hydroaminoalkylation, and CO2 fixation efficiently. In this review, the applications of both commercially available and synthesized zirconium catalysts in organic reactions in the last 5years are highlighted. Firstly, the properties and application of zirconium and its compounds are simply introduced. After presenting the superiority of zirconium compounds, their applications as catalysts to accelerate organic transformations are classified and presented in detail. On the basis of different kinds of zirconium catalysts, organic reactions accelerated by inorganic zirconium catalysts, zirconium catalysts bearing Cp, and organozirconium catalysts without Cp are summarized, and the plausible reaction mechanisms are presented if available.

Probing new DABCO-F based ionic liquids as catalyst in organic synthesis

The use of ionic liquids as an alternative to the traditional organic solvents offers many advantages, such as their (relatively) low cost of production, ease of handling and storage, high thermal stability, non-volatility, and ability to dissolve different organic and inorganic compounds. The use of ionic liquids for organic syntheses is also sustainable and environmentally friendly as they can be easily recovered and recycled after use. Herein we have synthesized 1,4-diazabicyclo[2.2.2]octane (DABCO)-based ionic liquids with fluoride anion, hence DABCO-C5-F and DABCO-C7-F, containing C5 and C7 alkyl chains respectively, were synthesized and characterized. Thermal studies (TGA/DSC) were also carried out to find out the decomposition temperature (and hence the working temperature range) of the ionic liquids. Moreover, quantum mechanical calculations were performed to obtain the optimized geometry configuration of ionic liquids and their stability was evaluated via binding energy calculation obtained from the MP2 method on the optimized structures. Finally, the DABCO ionic liquids were investigated for their efficiency for the synthesis of different organic compounds (indoles and 1,4-dihydropyridines), which were prepared in good to excellent yields indicating that these DABCO-F can be successfully utilized in organic syntheses by their dual role as ionic liquid and as a catalyst.

Metal‐ and Additive‐Free Aerobic Dehydrogenation of N‐Heterocycles and Hydrocarbons by N‐Doped Carbon

AbstractOver metal catalysts, N‐heteroarenes, as one of the most versatile building blocks in pharmaceuticals, bioactive molecules and natural products, can be easily accessed by the oxidation of N‐heterocycles. Herein, we describe N‐doped hierarchical pore carbons (N‐HPCs) derived from readily available biomass (flour) efficiently catalyzed aerobic dehydrogenation of N‐heterocycles without any additives under mild conditions, owing to N dopant and high surface area indicated by characterization analysis. A wide range of N‐heteroarenes including quinolines, quinolinol, dihydroisoquinolines, isoquinolines, indoles, quinoxaline and acridine were obtained in good to excellent yields (36 examples, up to 99% yield). Mechanistic studies revealed a strikingly different non‐free radical process from metal catalysts, for which an apparent activation energy of 66.4 kJ mol−1 was found. Moreover, the N‐doped carbon exhibited robust stability and yielded 74.5% quinoline at the sixth reaction. The use of metal‐free catalysts in organic synthesis is attractive but practically challenging. This work provides a promising example for metal‐free catalysis.

Ag-Catalyzed Multicomponent Synthesis of Heterocyclic Compounds: A Review.

The investigation of the procedures for the multi-component synthesis of heterocycles has attracted the interest of organic and medicinal chemists. The use of heterogeneous catalysts, especially transition metal catalysts in organic synthesis, can provide a new, improved alternative to traditional methods in modern synthetic chemistry. The main focus is on the utilization of silver as a catalyst for the multi-component synthesis of heterocyclic compounds. The present review describes some important reported studies for the period of 2010 to 2020. Conclusion: The present review addresses some of the important reported studies on multi-component synthesis of heterocycles in the period of 2010-2020. These approaches were performed under classical and nonclassical conditions, using Ag salts, Ag NPs, Ag on the support, Ag as co-catalysts with other transition metals, ionic liquids, acidic or basic materials. Most of the reported reactions were performed under solvent-free conditions or in green solvents and the utilized catalysts were mostly recyclable. The main aim of the present review is to provide the organic chemists with the most appropriate procedures in the multi-component synthesis of desired heterocycles using silver catalysts.

Carbides of transition metals: Properties, application and production. Review. Part 1. Titanium and vanadium carbides

The properties, application, and methods for producing titanium and vanadium carbides are considered. These carbides are oxygen-free refractory metal-like compounds. As a result, they are characterized by high values of thermal and electrical conductivity. Their hardness is relatively high. Titanium and vanadium carbides exhibit significant chemical resistance in aggressive environments. For these reasons, they have found application in modern technology. These carbides are used as surfacing materials for the application of wear-resistant coatings to steel products. It is possible to use them as catalysts in organic synthesis. Titanium carbide is used in tungsten-free hard alloys, carbide steels. Due to its high hardness, it is used as an abrasive and as a component of ceramic cutting tools. Vanadium carbide serves as an inhibitor of the growth of tungsten carbide grains in hard alloys. The properties of refractory compounds depend on the content of impurities and dispersion (particle size). To solve a specific problem associated with the use of refractory compounds, it is important to choose the right method for their preparation and to determine the permissible content of impurities in the initial components. This leads to existence of different methods for the synthesis of carbides. The main methods for their preparation are: synthesis from simple substances (metals and carbon), metallothermal and carbothermal reduction. Plasma-chemical synthesis (vapor-gas phase deposition) is also used to obtain carbide nanopowders. A characteristic is given to each of these methods. Information on the possible mechanism of the processes of carbothermal synthesis is presented.

Metal Triflates as Catalysts in Organic Synthesis: Determination of Their Lewis Acidity by Mass Spectrometry.

Metal triflates have shown a large variety of possibilities as catalysts in organic reactions. Some selected examples of their catalytic activity, in particular in C-O and C-C bond formation are presented. A better understanding of the mode of interaction between these Lewis acids and organic functional groups as ligands should allow for an easier choice of a tailored metal cation for a given reaction. Electrospray ionization mass spectrometry enables the characterization and the quantification of the donor/acceptor interactions involved in the catalytic processes. Both gas-phase and solution-phase interactions between various metal triflates and organic functionalities were studied. Based on an original probabilistic model, ligand displacement experiments lead us to establish quantitative affinity scales of ligands toward the metal centers. The main structural effects governing the ranking are identified and discussed.

Alcohol Dehydrogenases as Catalysts in Organic Synthesis

Alcohol dehydrogenases (ADHs) have become important catalysts for stereoselective oxidation and reduction reactions of alcohols, aldehydes and ketones. The aim of this contribution is to provide the reader with a timely update on the state-of-the-art of ADH-catalysis. Mechanistic basics are presented together with practical information about the use of ADHs. Current concepts of ADH engineering and ADH reactions are critically discussed. Finally, this contribution highlights some prominent examples and future-pointing concepts.

Immobilization of papain on nitrogen-doped graphene quantum dots improves the enzymatic properties and makes it a biosensor for cystatin C

In recent years enzymes had many applications, such as catalysts in organic synthesis and producing biosensors. In this study, nitrogen-doped graphene quantum dots (NGQDs) were functionalized with glutaraldehyde (NGQD-Glu) and used as a support for the immobilization of papain (NGQD-Glu-Papain). Immobilization of papain on NGQDs has considerably improved papain stability. So, with incubation of the enzymes at 70 °C, immobilized papain maintained 80% of its activity for 150 min while the free enzyme's residual activity was 55% after 50 min. The stability results in the presence of organic solvents showed that the immobilization increased papain stability, especially in polar solvents. The activity results showed that the Km value decreases from 2.02 g L−1 to 1.20 g L−1 after immobilization, and the Vmax value decreases from 932.1 μmol mg−1 min−1 to 62.5 μmol mg−1 min−1. The fluorimetric studies showed that the NGQD-Glu-Papain is specific sensitive to cystatin C at concentrations ranging from 0.05 ng L−1 to 50 ng L−1 with a 0.05 ng L−1 of limit for detection. In conclusion, NGQDs can be suitable for enzyme stabilization and biosensor production.