Catalysts In Organic Synthesis Research Articles

Preparation and Application of Single-Atom Cobalt Catalysts in Organic Synthesis and Environmental Remediation.

The development of high-performance catalysts plays a crucial role in facilitating chemical production and reducing environmental contamination. Single-atom catalysts (SACs), a class of catalysts that bridge the gap between homogeneous and heterogeneous catalysis, have garnered increasing attention because of their unique activity, selectivity, and stability in many pivotal reactions. Meanwhile, the scarcity of precious metal SACs calls for the arrival of cost-effective SACs. Cobalt, as a common non-noble metal, possesses tremendous potential in the field of single-atom catalysis. Despite their potential, reviews about single-atom Co catalysts (Co-SACs) are lacking. Accordingly, this review thoroughly summarized various preparation methodologies of Co-SACs, particularly pyrolysis; its application in the specific domain of organic synthesis and environmental remediation is discussed as well. The structure-activity relationship and potential catalytic mechanism of Co-SACs are elucidated through some representative reactions. The imminent challenges and development prospects of Co-SACs are discussed in detail. The findings and insights provided herein can guide further exploration and development in this charming area of catalyst design, leading to the realization of efficient and sustainable catalytic processes.

Cellulose-Based Metallogels-Part 3: Multifunctional Materials.

The incorporation of the metal phase into cellulose hydrogels, resulting in the formation of metallogels, greatly expands their application potential by introducing new functionalities and improving their performance in various fields. The unique antiviral, antibacterial, antifungal, and anticancer properties of metal and metal oxide nanoparticles (Ag, Au, Cu, CuxOy, ZnO, Al2O3, TiO2, etc.), coupled with the biocompatibility of cellulose, allow the development of composite hydrogels with multifunctional therapeutic potential. These materials can serve as efficient carriers for controlled drug delivery, targeting specific cells or pathogens, as well as for the design of artificial tissues or wound and burn dressings. Cellulose-based metallogels can be used in the food packaging industry to provide biodegradable and biocidal materials to extend the shelf life of the goods. Metal and bimetallic nanoparticles (Au, Cu, Ni, AuAg, and AuPt) can catalyze chemical reactions, enabling composite cellulose hydrogels to be used as efficient catalysts in organic synthesis. In addition, metal-loaded hydrogels (with ZnO, TiO2, Ag, and Fe3O4 nanoparticles) can exhibit enhanced adsorption capacities for pollutants, such as dyes, heavy metal ions, and pharmaceuticals, making them valuable materials for water purification and environmental remediation. Magnetic properties imparted to metallogels by iron oxides (Fe2O3 and Fe3O4) simplify the wastewater treatment process, making it more cost-effective and environmentally friendly. The conductivity of metallogels due to Ag, TiO2, ZnO, and Al2O3 is useful for the design of various sensors. The integration of metal nanoparticles also allows the development of responsive materials, where changes in metal properties can be exploited for stimuli-responsive applications, such as controlled release systems. Overall, the introduction of metal phases augments the functionality of cellulose hydrogels, expanding their versatility for diverse applications across a broad spectrum of industries not envisaged during the initial research stages.

Insight into the effect of Ca2+, Mg2+ and Zn2+ on serum albumin interaction of benzimidazole-type new isopropyl substituted N-heterocyclic carbene molecules

N-heterocyclic carbenes are not only revolutionary catalysts in organic synthesis but also well-known anthelmintics, fungicides, antacids, and antibiotics. Serum albumin transports various substances in the body such as hormones, fatty acids, bilirubin, certain drugs, and is also crucial in the maintenance of health and bodily functions. For that reason, in this study five novel benzimidazole-type N-heterocyclic carbenes, 1- Isopropyl-3-benzyl-5,6-dimethylbenzimidazolium chloride (2a), 1- Isopropyl-3-(2-chlorobenzyl)-5,6-dimethylbenzimidazolium chloride (2b), 1- Isopropyl-3-(2-methylbenzyl)-5,6-dimethylbenzimidazolium chloride (2c), 1- Isopropyl-3-(2,3,4,5,6-pentamethylbenzyl)-5,6-dimethylbenzimidazolium chloride (2d), 1- Isopropyl-3-naphthyl-5,6-dimethylbenzimidazolium chloride (2e) were gained in 74–85 % yields. The molecules were fully characterized 1H and 13C NMR, elemental analysis, UV–Vis spectroscopy, FT-IR, and DFT- and TDDFT-based in-silico methods. Additionally, Stern-Volmer methods with fluorescence spectroscopy were performed in order to analyze the BSA-binding properties of these molecules. BSA interactions of molecules were evaluated with specific concentrations of Ca2+, Mg2+ and Zn2+. The detailed interaction analyses were also surveyed by molecular docking methods against the BSA and DNA.

Recent applications of heteroatom-centered radicals as catalysts in organic synthesis

Recent applications of heteroatom-centered radicals as catalysts in organic synthesis

Synthesis, Characterization and Antibacterial Activity of PolypyrroleMontmorillonite Nanocomposites

Conducting polymers and its composites found to be promising candidate for the medical and electroanalytical application in various fields. Significant functional exercise on Montmorillonite clay proves wide appliction in food additive , for antibacterial activity against tooth and gum decay, as sorbent for nonionic, anionic, and cationic dyes, and the use as catalyst in organic synthesis. Polypyrrole and Montmorillonite clay are used in the synthesis of Polypyrrole/ Montmorillonite nanocomposites by chemical oxidative method. Obtained PPy/montmorillonite composites are characterised by UV, FTIR and morphology and composition analysis are also done by using FESEM and EDX. Biological activities of the Polypyrrole/Montmorillonite conducting polymers composites (CPs) are studied by using the Bacillus, E.Coli, Pseudomonae as a bacterial cultures. PPY/7.5% MMT composite show antibacterial activity for the Bacillus,bacteria but for the E.Coli, Pseudomonaeno no activity.

Application of N-heterocyclic carbene-Cu(I) complexes as catalysts in organic synthesis: a review.

N-Heterocyclic carbenes (NHCs) are a special type of carbenes in which the carbene carbon atom is part of the nitrogen heterocyclic ring. Due to the simplicity of their synthesis and the modularity of their stereoelectronic properties, NHCs have unquestionably emerged as one of the most fascinating and well-known species in chemical science. The remarkable stability of NHCs can be attributed to both kinetic as well as thermodynamic effects caused by its structural features. NHCs constitute a well-established class of new ligands in organometallic chemistry. Although initially NHCs were regarded as pure σ-donor ligands, later experimental and theoretical studies established the presence of a significant back donation from the d-orbital of the metal to the π* orbital of the NHC. Over the last two decades, NHC-metal complexes have been extensively used as efficient catalysts in different types of organic reactions. Of these, NHC-Cu(I) complexes found prominence for various reasons, such as ease of preparation, possibility of structural diversity, low cost, and versatile applications. This article overviews applications of NHC-Cu(I) complexes as catalysts in organic synthesis over the last 12 years, which include hydrosilylation reactions, conjugate addition, [3 + 2] cycloaddition, A3 reaction, boration and hydroboration, N-H and C(sp2)-H carboxylation, C(sp2)-H alkenylation and allylation, C(sp2)-H arylation, C(sp2)-H amidation, and C(sp2)-H thiolation. Preceding the section of applications, a brief description of the structure of NHCs, nature of NHC-metal bond, and methods of preparation of NHC-Cu complexes is provided.

Covalent or ionic bonding of Eosin Y to silica: New visible-light photocatalysts for redox wastewater remediation

Eosin Y (EY) is an organic dye widely used as a photoredox catalyst in organic synthesis, but there are only few studies on its use in heterogeneous photocatalysis for the degradation of aqueous Contaminants of Emerging Concern (CECs). In this context, several synthetic strategies were used to prepare heterogeneous silica-based photocatalysts where EY is anchored to glass wool (GW) covalently or using ionic bonds for obtaining GW-C-EY and GW-I-EY, respectively. The percentage of EY linked to GW-C-EY (up to 0.0034% w/w) was always lower than the obtained in GW-I-EY (0.165% w/w). Photodegradation of CECs such as noscapine (NOS), sulfamethoxazole (SMX) and ofloxacin (OFX) was studied using the new heterogeneous photocatalysts in water under visible light irradiation and results showed that only NOS is photodegraded. It was also observed that EY photoreactivity in GW-C-EY and GW-I-EY is quite similar. Interestingly, when the photocatalysts were studied using mixtures of the three CECs, a synergistic effect that favors the photodegradation of SMX and OFX was observed. Specifically, GW-I-EY achieves 100% photodegradation for NOS and ca. 50% removal of SMX and OFX. Based on photophysical and photochemical experiments, redox processes initiated by an electron transfer from NOS to the EY triplet excited state and the subsequent reaction of the generated EY•− with SMX or OFX justify the observed synergistic photodegradation. This finding opens up the possibility of working with complex aqueous matrices and also of smart selecting the combination of different types of contaminated waters to favor the efficiency of the photocatalytic decontamination processes.

Fungal lyophilisates as catalysts for organic synthesis: Preparative oxidations with the white-rot fungus Bjerkandera adusta

A clean and selective “on-water-on-air” oxidation of primary alcohols to the corresponding aldehydes with mycelium lyophilisates of the non-toxic white-rot fungus Bjerkandera adusta was developed. The biocatalytic protocol is simple and the catalyst is readily accessible as a powder, which could be stored at least for 7 months without changes of activity. The catalytic activity of the fungus is associated with the presence of aryl-alcohol oxidase, that was isolated from the lyophilisate and characterised. Remarkably, a dichotomy in the fungal reactivity was observed, as the corresponding growing cultures catalyse the reverse process, selectively reducing aldehydes to the corresponding alcohols. Enzymatic oxidations by B. adusta are an excellent non-toxic alternative to metal-mediated oxidations in the lab with potential in food, beverage, cosmetic, and pharmaceutical industries, as it tolerates many functional groups.

Colloidal and nanosized catalysts in organic synthesis. XXVI. Аmines alkylation with alcohols catalyzed by γ-al<sub>2</sub>o<sub>3</sub>-supported nickel and copper nanoparticles

Amines alkylation with alcohols catalyzed by γ-Al2O3-supported nickel and copper nanoparticles under continuous process conditions at atmospheric hydrogen pressure and 180-220°С leads to the formation of alkylated products with selectivity up to 100%.

Colloidal and Nanosized Catalysts in Organic Synthesis:XXVI. Amines Alkylation with Alcohols Catalyzed by γ-Al2O3-Supported Nickel and Copper Nanoparticles

Colloidal and Nanosized Catalysts in Organic Synthesis:XXVI. Amines Alkylation with Alcohols Catalyzed by γ-Al2O3-Supported Nickel and Copper Nanoparticles

TMU-16-NH2: A Metal–Organic Framework as an Efficient, Green, and Heterogeneous Catalyst for the Michael Addition Annulations for the Synthesis of a New Series of 2,4-Diphenylpyrido[4,3-d]Pyrimidines

ABASTRACT Considering the unprecedented attributes governed by metal-organic framework nanostructures, the present report discloses the fabrication of [Zn2(H2N-BDC)2(4-bpdh)]·3DMF as a Zn-based MOF catalyst (TMU-16-NH2 (TMU = Tarbiat Modares University)) through the coordination of 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh) ligand to the Zn(NO3)2·6H2O salt under hydrothermal approach. In order to certify the successful synthesis of the catalyst, FT-IR, XRD, TGA, Elemental microanalysis, ICP OES and BET measurements were employed. The developed TMU-16-NH2 catalytic agent acts as a promising candidate to deliver a new class of pharmaceutically relevant 2,4-diphenylpyrido[4,3-d]pyrimidine scaffolds via the Michael addition annulations of benzimidamid hydrochloride to (3E,5E)-3,5-bis-(benzylidene)-4-piperidone reacting species. The devised methodology is accompanied with noteworthy benefits including mild reaction conditions, wide substrate scope, excellent product yields and short reaction span. Besides, facile retrievability and remarkable reusability of the catalyst for 5 successive runs without any appreciable loss in catalytic efficacy are the additional factors that rationalize this protocol as worthwhile. Our findings highlight the potential of using MOFs as efficient and versatile catalysts in organic synthesis and contribute to the growing body of literature on the synthesis of pyrido[4,3-d]pyrimidines with diverse biological activities.

Synthesis of Azoxy Compounds: from Copper Compounds to Mesoporous Silica-Encaged Ultrasmall Copper Catalysts.

Azoxy compounds have aroused extensive attention due to their unique biological activities, but the chemical synthesis of these compounds often suffers from limitations due to their requirement for stoichiometric oxidants, high costs, and restricted substrate range. Herein, a series of azoxy compounds were constructed via facile coupling reactions by using cost-effective N-methoxyformamide and nitroso compounds over Cu-based catalysts, affording high product yields with excellent tolerance of functional groups. Significantly, the mesoporous silica nanosphere-encapsulated ultrasmall Cu (Cu@MSN) catalyst was developed via a one-pot synthetic method and first used for the synthesis of azoxy compounds. As compared with copper salt catalysts, the Cu@MSN catalyst exhibited remarkably enhanced catalytic activity and superior recycling stability. Such a Cu@MSN catalyst overcame the inherent drawbacks of low activity, fast deactivation, and difficult recycling of traditional metal salt catalysts in organic reactions. This work provides a green and efficient method for the construction of azoxy compounds and also creates new prospects for the application of nanoporous materials confined metal catalysts in organic synthesis.

Electrospray Ionization Tandem Mass Spectrometric Study of Selected Phosphine-Based Ligands for Catalytically Active Organometallics.

Selected organometallic compounds are nowadays extensively used as highly efficient catalysts in organic synthesis. A great variety of different ligand systems exists, of which phosphine-based ligands are a significant subgroup. While mass spectrometry, predominantly electrospray ionization mass spectrometry (ESI-MS), is a standard analytical technique for the identification of new ligands and their metal complexes, there is little information on the behavior of phosphine-based ligands/molecules by electrospray ionization collision-induced dissociation tandem mass spectrometry (ESI-CID-MS/MS) at low collision energies (<100 eV) in the literature. Here, we report a study on the identification of typical product ions occurring in tandem mass spectra of selected phosphine-based ligand systems by ESI-CID-MS/MS. The influence on the fragmentation behavior of different backbones (pyridine, benzene, triazine) as well as different spacer groups (amine, methylamine, methylene), which are directly linked to the phosphine moiety, is investigated by tandem mass spectrometry. In addition, possible fragmentation pathways are elaborated based on the assigned masses in the tandem mass spectra with high-resolution accurate mass determination. This knowledge may be particularly useful in the future for the elucidation of fragmentation pathways for coordination compounds by MS/MS, where the studied compounds serve as building blocks.

Biocatalytic Nitration of Phenols in Microemulsions at Elevated Temperatures Using Enzymes Stabilized on Magnetic Beads

AbstractEnzymes as catalysts in organic syntheses can provide high regio‐ and stereo‐selectivity, which is often not possible with chemical catalysts. Biocatalysis with iron heme enzymes has proven efficient when the enzyme is sequestered in thin films. An added feature is improved stability. For example, peroxidases chemically crosslinked in poly‐lysine in films on silica nanoparticles were stable for 9 hrs or more at 90 °C, and were used for biocatalysis up to 90 °C. We show here for a series of para‐substituted phenols, single nitro‐phenol products can be selectively synthesized using biocatalytic magnetic beads coated with horseradish peroxidase (HRP) crosslinked in polylysine films. Nitrophenols moieties are important as synthetic intermediates and in drugs. For a series of para‐substituted phenols, biocatalytic nitration gave average turnover numbers 1.8‐fold larger at 75 °C than at 25 °C. For phenols giving &lt;50 % conversion after 1 hr at 25 °C, twice the nitration yield was achieved in 1 hr at 75 °C. Results indicate that this approach should be valuable as a general tool for biocatalytic chemical synthesis.

Single-Atom Catalysis in Organic Synthesis.

Single-atom catalysts hold the potential to significantly impact the chemical sector, pushing the boundaries of catalysis in new, uncharted directions. These materials, featuring isolated metal species ligated on solid supports, can exist in many coordination environments, all of which have shown important functions in specific transformations. Their emergence has also provided exciting opportunities for mimicking metalloenzymes and bridging the gap between homogeneous and heterogeneous catalysis. This Review outlines the impressive progress made in recent years regarding the use of single-atom catalysts in organic synthesis. We also illustrate potential knowledge gaps in the search for more sustainable, earth-abundant single-atom catalysts for synthetic applications.

Single‐Atom Catalysis in Organic Synthesis

AbstractSingle‐atom catalysts hold the potential to significantly impact the chemical sector, pushing the boundaries of catalysis in new, uncharted directions. These materials, featuring isolated metal species ligated on solid supports, can exist in many coordination environments, all of which have shown important functions in specific transformations. Their emergence has also provided exciting opportunities for mimicking metalloenzymes and bridging the gap between homogeneous and heterogeneous catalysis. This Review outlines the impressive progress made in recent years regarding the use of single‐atom catalysts in organic synthesis. We also illustrate potential knowledge gaps in the search for more sustainable, earth‐abundant single‐atom catalysts for synthetic applications.

New Developments of Chiral Palladium‐Aqua Complexes as Cooperative Brønsted Acid‐Base Catalysts in Organic Synthesis

AbstractBased upon their exceptional reactivity as cooperative Brønsted acid‐base catalysts chiral diphosphane Pd‐aqua complexes have successfully been utilized in a broad range of asymmetric transformations. Originally discovered by Sodeoka 25 years ago, they readily form reactive chiral Pd enolates upon deprotonation of β‐dicarbonyl compounds and simultaneously, a Brønsted acid liberated from the catalyst activates the electrophile. After the initial report and some ensuing papers had been published in the early 2000s, the field lay dormant for more than a decade. In recent years, however, new developments towards the enantioselective synthesis of various heterocycles and other useful compounds have evolved which take advantage of the unique properties of chiral Pd‐aqua complexes.

HFIP‐Catalyzed Mannich Reaction: Divergent Synthesis of Difluoro‐Substituted 3,4‐Dihydroquinoxalin‐2(1H)‐ones and Monofluoroquinoxalin‐2(1H)‐ones

AbstractHexafluoroisopropanol (HFIP) has been extensively applied in organic synthesis as a versatile reaction media. However, the application of HFIP as an catalyst in organic synthesis has been rarely studied. Presented here, is the example of HFIP‐catalyzed Mannich‐type reaction between quinoxalin‐2(1H)‐ones and difluoroenoxysilanes. The developed protocol tolerates various substituents under mild reaction conditions, providing a divergent approach to the construction of difluoro‐substituted 3,4‐dihydroquinoxalin‐2(1H)‐ones and monofluoroquinoxalin‐2(1H)‐ones in 51–92% yields.magnified image

Versatile application of strong Brønsted acid deep eutectic solvent as recyclable reaction media and catalysts in organic synthesis

Deep eutectic solvents (DESs) will be one of the most promising alternatives to conventional organic solvents. Hitherto, little attention has been dedicated to their applications in organic synthesis about strongly acid DESs. Herein, strong Brønsted acid DESs based on PTSA/PEG4000 were developed and used firstly to synthesize three significant compounds, namely 3,4-dihydrochromans, dihydrocoumarins and indolo[3,2-a]carbazoles, as reaction media and catalysts, and all of desired products were obtained in high yields in a short time. Furthermore, the yield of 3,4-dihydrochroman has not significant loss after five runs revealed that the PTSA/PEG4000 DES has ideal activity and recyclability. The PTSA/PEG4000 DES was characterized by FT-IR and TGA, and the obtained results also verified uniformity structure and the good stability of DES before and after reaction. More importantly, the eco-friendly and sustainable strategy minimized the utilization of organic solvents to a certain extent because crude products can be readily extracted by green solvent n-hexane, avoiding a series of issues introduced by conventional organic solvents.

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.