Catalytic Procedure Research Articles

Reduction of imines with a reusable bimetallic PdCo-Fe3O4 catalyst at room temperature under atmospheric pressure of H2.

Bimetallic nanocatalysts have been used for the development of organic reactions, owing to the synergistic effect between the transition metals. A new procedure for synthesizing amines by the reduction of imines with H2 at atmospheric pressure and room temperature in the presence of PdCo–Fe3O4 nanoparticles is reported. The straightforward procedure, mild reaction conditions, high turnover number, and recyclability extend the scope of this reaction to practical applications.

Primary amines from lignocellulose by direct amination of alcohol intermediates, catalyzed by RANEY® Ni.

Primary amines are crucially important building blocks for the synthesis of a wide range of industrially relevant products. Our comprehensive catalytic strategy presented here allows diverse primary amines from lignocellulosic biomass to be sourced in a straightforward manner and with minimal purification effort. The core of the methodology is the efficient RANEY® Ni-catalyzed hydrogen-borrowing amination (with ammonia) of the alcohol intermediates, namely alkyl-phenol derivatives as well as aliphatic alcohols, obtained through the two-stage LignoFlex process. Hereby the first stage entails the copper-doped porous metal oxide (Cu20PMO) catalyzed reductive catalytic fractionation (RCF) of pine lignocellulose into a crude bio-oil, rich in dihydroconiferyl alcohol (1G), which could be converted into dihydroconiferyl amine (1G amine) in high selectivity using ammonia gas, by applying our selective amination protocol. Notably also, the crude RCF-oil directly afforded 1G amine in a high 4.6 wt% isolated yield (based on lignin content). Finally it was also shown that the here developed Ni-catalysed heterogeneous catalytic procedure was equally capable of transforming a range of aliphatic linear/cyclic primary/secondary alcohols - available from the second stage of the LignoFlex procedure - into their respective primary amines.

Hemilabile MIC^N ligands allow oxidant-free Au(i)/Au(iii) arylation-lactonization of γ-alkenoic acids.

Oxidant-free Au-catalyzed reactions are emerging as a new synthetic tool for innovative organic transformations. Oxidant-free Au-catalyzed reactions are emerging as a new synthetic tool for innovative organic transformations. Still, a deeper mechanistic understanding is needed for a rational design of these processes. Here we describe the synthesis of two Au(i) complexes bearing bidentated hemilabile MIC^N ligands, [AuI(MIC^N)Cl], and their ability to stabilize square-planar Au(iii) species (MIC = mesoionic carbene). The presence of the hemilabile N-ligand contributed to stabilize the ensuing Au(iii) species acting as a five-membered ring chelate upon its coordination to the metal center. The Au(iii) complexes can be obtained either by using external oxidants or, alternatively, by means of feasible oxidative addition with strained biphenylene Csp2–Csp2 bonds as well as with aryl iodides. Based on the fundamental knowledge gained on the redox properties on these Au(i)/Au(iii) systems, we successfully develop a novel Au(i)-catalytic procedure for the synthesis of γ-substituted γ-butyrolactones through the arylation-lactonization reaction of the corresponding γ-alkenoic acid. The oxidative addition of the aryl iodide, which in turn is allowed by the hemilabile nature of the MIC^N ligand, is an essential step for this transformation.

Polymeric Droplets on SiO2 Nanoparticles through Wastewater Treatment of Carbon‐Based Contaminants in Photocatalytic Degradation

The current work focus is on utilizing sunlight to catalyze the destruction of carbon‐based (organic) pollutants. To increase the morphological area and improve the proficiency of the photocatalytic technique, sodium alginate was used as a polymeric tool and arranged as drop practice. SiO2 nanoparticles were doped into sodium alginate droplets. The developed SiO2 nanomaterials were able to spread the wavelength diversity throughout a significant wavelength constituency. In the photocatalytic technique employing the lot photoreactor, MB was used as a sample of carbon‐based pollutants. The sunlight catalytic procedure was implemented from UV‐Vis or photo light droplets. The analysis of the synthesized droplets was tested using devices X‐ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) analysis. Correspondingly, the influences of different concentrations of SiO2 nanosolution (5 ml, 10 ml, 15 ml, and 20 ml) on the photocatalytic effectiveness of the deposited nanoparticles were studied. The output result revealed that sodium alginate beads doped with SiO2 at 20 ml were able to reduce (degrade) 98.9% underneath UV‐visible light. However, in the case of using other concentrations, SiO2 at 5, 10, and 15 ml were able to degrade 50%, 56.7%, and 67.9% under sunlight, respectively, after 2 h.

Cartap wastewater treatment by a microwave-induced catalytic oxidation procedure over Ce/Co/γ-Al2O3

Microwave-assisted catalytic technology is potentially promising in the application of water treatment due to its merits of high reaction rates, simple equipment and operations. In case of the cartap wastewater rarely studied, the easy transformation of cartap into metabolites could induce higher toxicity. This study aimed to develop a novel catalyst Ce/Co/γ-Al2O3 to dispose cartap effectively. The catalyst was prepared by loading Ce and Co on the surface of the support Al2O3, followed by characterization with X-ray diffraction, scanning and transmission electron microscopies. Based on the treatment results, the microwave-induced catalytic oxidation procedure over Ce/Co/γ-Al2O3 could decompose the contaminants efficiently and fast in the case of a low oxidant dosage and a wide pH range. Under the conditions of pH of 5, microwave power of 450 W, catalyst dosage of 0.7 g and hydrogen peroxide dosage of 0.2 mL, the activity of Ce/Co/γ-Al2O3 catalyst could reach up to 86.08%. Importantly, the Ce/Co/γ-Al2O3 catalyst displayed excellent stability after using for 6 times in the degradation process. This work paved a new way for the effective catalyst design for efficient microwave-induced oxidative degradation.

Photocatalytic Arylation of P4 and PH3 : Reaction Development Through Mechanistic Insight.

Detailed 31P{1H} NMR spectroscopic investigations provide deeper insight into the complex, multi‐step mechanisms involved in the recently reported photocatalytic arylation of white phosphorus (P4). Specifically, these studies have identified a number of previously unrecognized side products, which arise from an unexpected non‐innocent behavior of the commonly employed terminal reductant Et3N. The different rate of formation of these products explains discrepancies in the performance of the two most effective catalysts, [Ir(dtbbpy)(ppy)2][PF6] (dtbbpy=4,4′‐di‐tert‐butyl‐2,2′‐bipyridine) and 3DPAFIPN. Inspired by the observation of PH3 as a minor intermediate, we have developed the first catalytic procedure for the arylation of this key industrial compound. Similar to P4 arylation, this method affords valuable triarylphosphines or tetraarylphosphonium salts depending on the steric profile of the aryl substituents.

Photocatalytic Arylation of P4 and PH3: Reaction Development Through Mechanistic Insight

AbstractDetailed 31P{1H} NMR spectroscopic investigations provide deeper insight into the complex, multi‐step mechanisms involved in the recently reported photocatalytic arylation of white phosphorus (P4). Specifically, these studies have identified a number of previously unrecognized side products, which arise from an unexpected non‐innocent behavior of the commonly employed terminal reductant Et3N. The different rate of formation of these products explains discrepancies in the performance of the two most effective catalysts, [Ir(dtbbpy)(ppy)2][PF6] (dtbbpy=4,4′‐di‐tert‐butyl‐2,2′‐bipyridine) and 3DPAFIPN. Inspired by the observation of PH3 as a minor intermediate, we have developed the first catalytic procedure for the arylation of this key industrial compound. Similar to P4 arylation, this method affords valuable triarylphosphines or tetraarylphosphonium salts depending on the steric profile of the aryl substituents.

Carbocatalytic Cascade Synthesis of Polysubstituted Quinolines from Aldehydes and 2‐Vinyl Anilines

AbstractOxidized active carbon (oAC) catalyses the formation of polysubstituted quinolines from o‐vinyl anilines and aldehydes. The reaction proceeds in a cascade manner through condensation, electrocyclization and dehydrogenation, and gives access to a wide range of quinolines with alkyl and/or aryl substituents as demonstrated with 40 examples. The metal‐free catalytic procedure allows a heterogeneous protocol for the synthesis of various polysubstituted quinolines. The mechanistic studies imply that both the acid and quinoidic groups in oAC are integral for the catalytic manifold.magnified image

Cysteine-Mediated Cyclic Metabolism Drives the Microbial Degradation of Keratin

Keratinase is a key enzyme to degrade keratin. However, the extremely low efficiency of keratinase hydrolyzing keratin after being separated from living cells is still the bottleneck of its application. Living cells seem to provide synergistic factors for the efficient catalysis of keratinase. To this end, we analyzed the role of the metabolic activity of living cells in the hydrolysis of feather keratin by keratinase. Here, studies have shown that sulfite is the key to switch on the catalytic procedure of keratinase, and cysteine is the bridge for living cells to control this process. Cysteine catabolism mediated by an intracellular detoxification mechanism produces sulfite and is secreted to promote the hydrolysis of keratin by keratinase. Then, the cysteine released by keratin hydrolysis will enter the cell and continue to be converted into sulfite through catabolism. These two processes form a perpetual chain reaction for the adequate hydrolysis of keratin. Furthermore, we confirmed that loading this self-circulation synergistic catalysis system into keratinase-secreting cells can significantly enhance their keratin hydrolysis capacity. This work demonstrated the missing link of keratinase-catalyzed keratin hydrolysis and obtained engineered strains with improved hydrolysis capacity.

Nanostructured KIT-6 materials functionalized with sulfonic groups for catalytic purposes

In the present study, a series of ordered nanostructured KIT-6 silica, functionalized with different numbers of sulfonic groups (–SO3H) introduced by grafting or co-condensation, were synthesized. The obtained samples were subjected to thorough physicochemical characterization using X-ray diffraction, transmission electron microscopy, low temperature nitrogen sorption, infrared spectroscopy and elemental analysis. It has been observed that the amount of the used functional group precursor clearly affects the structural and textural parameters of the studied materials synthesized by co-condensation. On the other hand, the samples modified by grafting, irrespective of the number of the introduced –SO3H groups, exhibit a stable mesoporous structure with Ia3d symmetry, characteristic of KIT-6 materials. The developed synthesis procedures yielded potential solid acid catalysts, which were used in the test catalytic reactions: Friedel-Crafts alkylation, fatty acid esterification and Pechmann condensation. Both the developed synthesis algorithm and the catalytic reaction procedures comprised elements of "green chemistry", as the transformation of the functional groups precursor (–SH to –SO3H) took place in the presence of H2O2, an oxidant considered to be environmentally friendly, while the catalytic reactions were carried out without solvents and under microwave-assisted conditions, which allowed a significant shortening of the reaction time.

Rapidly, highly yielded and green synthesis of dihydrotetrazolo[1,5‐a]pyrimidine derivatives in aqueous media using recoverable Pd (II) thiazole catalyst accelerated by ultrasonic: Computational studies

Here, we synthesized new thiazole complexes from Cu (II), Fe (III), and Pd (II) ions. Such complexes were characterized to present their chemical formulae, firstly. The octahedral geometry was suggested for the investigated complexes except Pd (II) complex (ARPTPd), which has a square‐planer arrangement. ARPTPd was planned to be used as a catalyst for synthesis of dihydrotetrazolo[1,5‐a]pyrimidine derivatives at mild conditions. The catalytic activity of ARPTPd complex in four‐components reaction approach was deliberately monitored till it reaches the most favorable conditions. The advantages of suggested catalyst were basically summarized by using green solvent (H2O), lower reaction time, and high products yields. Also, the superiority of ARPTPd complex and ultrasonic irradiation towards synthesis of dihydrotetrazolo[1,5‐a]pyrimidine derivatives was revealed compared with other Lewis acids, basic, and ionic liquid catalysts. Furthermore, the mildness of conversion and compatibility with different functional groups makes it attractive. In addition, in consecration, computational aspects were often taken according to their effect on the declaration or discrimination of variable functional characteristics. Crystal packing systems of complexes were configured to extract important surface properties. DFT study was also applied to explain the causes behind the superiorly of ARPTPd complex. Also, the optimization process for intermediates was executed to support the suggested mechanism. Finally, this simple, economical, and green catalytic procedure may be applied to the industry in future.

A nickel complex of 2,2-dicyanoethylene-1,1-dithiolate, a catalyst for electrochemical and photochemical driven hydrogen evolution

The reaction of NiCl2, K2(i-mnt) (i-mnt2−= 2,2-dicyanoethylene-1,1-dithiolate) and 1-benzyl-4-amino-pyridinium bromide [BzPyNH2]Br affords a nickel complex, [BzPyNH2]2[Ni(i-mnt)2], a molecular catalyst for electrochemical and photochemical driven hydrogen evolution. As an electrocatalyst, [BzPyNH2]2[Ni(i-mnt)2] can electrocatalyze hydrogen generation from a neutral buffer with a turnover frequency (TOF) of 556 (±3) mol of hydrogen per mole of catalyst per hour (mol H2/mol catalyst/h) at an overpotential (OP) of 837.6 mV. As a photocatalyst, combining with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H2A) as a sacrificial electron donor, [BzPyNH2]2[Ni(i-mnt)2] photocatalyzes hydrogen evolution in heterogeneous environments with a turnover number (TON) of 18420 (±5) mol H2 per mol of catalyst during 60 h irradiation. The highest apparent quantum yield (AQY) is ∼10% at 469 nm. Several chemical and physical methods are employed to understand catalytic procedures for H2 production.

Preparation and Characterization of a Novel Magnetic Nano Catalyst for Synthesis and Antibacterial Activities of Novel Furan-2(5H)-Ones Derivatives

Sulfamic acid 2-Aminobenzothiazole-6-carboxylic acid functionalized Fe3O4 nanoparticles as a novel organic-inorganic hybrid heterogeneous catalyst were manufactured and characterized by FT-IR, XRD, TGA, SEM, TEM, and VSM techniques. The catalytic activity of the magnetic catalyst was investigated through the one-pot synthesis of novel 3,4,5-trisubstituted furan-2(5H)-ones derivatives from aryl aldehydes, 4-amino pyridine, and dimethyl acetylenedicarboxylate. The structure of all the new synthesized derivatives was determined by FT-IR, 1H-NMR, and 13C-NMR. The synthetic compounds exert moderate activity against both Gram-positive and Gram-negative bacteria and their effectiveness is higher against Bacillus subtilis. This green nano catalytic procedure has good reversibility and provides clean production in a short reaction time. These characters make the method practical and economical for researchers.

The environmental impact of potassium tungstophosphate/ZSM-5 zeolite: Insight into catalysis and adsorption processes

Environmental implementation of novel composite materials comprising potassium tungstophosphate (KPW) and ZSM-5 zeolite was tested in ethene production and pesticide removal. The study revealed that the binding of KPW to ZSM-5 zeolites of different Si/Al ratios affects the formation of active centres for catalytic and adsorption processes. Brønsted active sites present in the zeolite framework are synergistically joined with Lewis centres and additional Brønsted centres through the impregnation of potassium tungstophosphate, which resulted in improvement of stability and activity of investigated materials. Adsorption and catalytic performance were found to be influenced by the order of addition of salt precursors and by post-synthesis thermal treatment. The best results found both in ethanol dehydration and nicosulfuron removal were for the same sample of KPW supported at zeolite ZSM-5 (SiO2/Al2O3 = 30). The prominent ethanol conversion of 98% and the highest and most stable selectivity toward ethene were evidenced, along with the capacity of 28.4 mg of targeted pesticide retained per gram of designed KPW/ZSM composite. This comprehensive investigation enabled insight into active site formations in the efficient KPW/ZSM composites. Different approaches to implementation revealed that a lower Si/Al ratio in zeolite promotes efficient K+ exchange, which combined with two-phased in situ preparation of KPW as active phase, evidently leads to the formation of isolated sites of superior activity for both catalytic and adsorptive procedures.

Los orígenes de la organocatálisis enantioselectiva y el premio Nobel de Química de 2021

Any advanced society requires new molecules and materials to be used as drugs, agrochemicals, energy production and storage and countless other applications. This, in turn, requires the development of new methods for synthesis. The 2021 Nobel Prize in Chemistry was awarded to Professors Benjamin List and David MacMillan “for the development of asymmetric organocatalysis”. This is a relatively new tool for enantioselective organic synthesis that has undergone an explosive growth since its introduction in 2000 by the awardees and serves as an alternative to the more traditional catalytic procedures based on the use of enzymes and metal-based catalysts.

Counterion-Enhanced Pd/Enamine Catalysis: Direct Asymmetric α-Allylation of Aldehydes with Allylic Alcohols by Chiral Amines and Achiral or Racemic Phosphoric Acids.

We report a straightforward and efficient Pd/enamine catalytic procedure for the direct asymmetric α-allylation of branched aldehydes. The use of simple chiral amines and easily prepared achiral or racemic phosphoric acids, together with a suitable Pd-source resulted in a highly active and enantioselective catalyst system for the allylation of various α-branched aldehydes with different allylic alcohols. The reported procedure could provide an easy access to both product antipodes. Furthermore, two possible orthogonal derivatizations of the enantioenriched aldehydes were performed without any decrease in enantioselectivity.

Hydrogenation of Aqueous Acetic Acid over Ru-Sn/TiO2 Catalyst in a Flow-Type Reactor, Governed by Reverse Reaction

Ru-Sn/TiO2 is an effective catalyst for hydrogenation of aqueous acetic acid to ethanol. In this paper, a similar hydrogenation process was investigated in a flow-type rather than a batch-type reactor. The optimum temperature was 170 °C for the batch-type reactor because of gas production at higher temperatures; however, for the flow-type reactor, the ethanol yield increased with reaction temperature up to 280 °C and then decreased sharply above 300 °C, owing to an increase in the acetic acid recovery rate. The selectivity for ethanol formation was improved over the batch process, and an ethanol yield of 98 mol % was achieved for a 6.7 min reaction (cf. 12 h for batch) (liquid hourly space velocity: 1.23 h−1). Oxidation of ethanol to acetic acid (i.e., the reverse reaction) adversely affected the hydrogenation. On the basis of these results, hydrogenation mechanisms that include competing side reactions are discussed in relation to the reactor type. These results will help the development of more efficient catalytic procedures. This method was also effectively applied to hydrogenation of lactic acid to propane-1,2-diol.

Catalytic Processes for the Neutralization of Sulfur Mustard.

Research on the decontamination of the chemical warfare agent sulfur mustard pursues several objectives that include the neutralization of spared ammunition, the cleaning of affected areas, and also the development of protective equipment or tools. Neutralization of vesicant sulfur mustard involves different chemical routes such as hydrolysis, dehydrochlorination, oxidation, or complete mineralization. This review weighs the pros and cons associated with the different systems reported in the literature, with an emphasis on catalytic procedures, to selectively convert sulfur mustard or its simulants into harmless products.

Carbonyl oxygen-coordinated metallic cobalt nanoparticles anchored on hybrid mesoporous silica matrix to enhance 4-nitrophenol hydrogenation

In this paper, urea group functionalized periodic mesoporous organosilica was utilized as matrix to introduce cobalt precursor into framework. After pyrolysis in nitrogen atmosphere, urea group was decomposed into carbon species and simultaneously the cobalt precursor was reduced to metallic cobalt nanoparticles. The metallic cobalt nanoparticles can be stabilized by coordinating to carbonyl oxygen atoms in carbon species. The supported metallic cobalt exhibited excellent catalytic performance towards 4-nitrophenol hydrogenation reaction. The largest turnover frequency number can reach up to 164.8 h−1, and the reaction rate constant can be as high as 0.77 min−1. The influence of pyrolysis temperature on catalytic performance was also investigated. Compared with the results obtained by samples prepared with wet impregnation method or different pyrolysis rate, it can be concluded that the coordination to carbonyl oxygen atom in carbon species plays a crucial role in improving electron transfer between metallic cobalt and carbon species during catalytic procedure. Metallic cobalt nanoparticles with high dispersion were introduced into urea group functionalized mesoporous silica matrix via pyrolysis in nitrogen atmosphere. The coordination to carbonyl oxygen atom enhances the catalytic performance in 4-nitrophenol hydrogenation.

Sonosynthesis of Spiro-Oxindoles Using Crosslinked Sulfonated Polyacrylamide Tethered to nano-Fe3O4 as High Performance Catalyst

Crosslinked sulfonated polyacrylamide (Cross-PAA-SO3H) tethered to nano-Fe3O4 as a superior heterogeneous solid acid catalyst has been used for the preparation of eight spiro-oxindoles by reactions of phenylhydrazine or hydrazine hydrate, isatins, ketoesters and naphthylamine or 2-naphthol under ultrasonic irradiations. The present catalytic procedure is extensible to a wide diversity of substrates for the synthesis of a variety-oriented library of oxindoles. The structures of the prepared oxindoles were fully characterized by 1H and 13C NMR spectra, FT-IR spectra, and elemental analysis. Experimental simplicity, wide range of products, excellent yields in short reaction times, reusability of the catalyst, low catalyst loading and use of ultrasonic irradiation, are some of the substantial features of this method. The feasibility of performing one-pot multi-component synthesis under ultrasonic irradiation with a heterogeneous catalyst could improve the reactions rates and shorten the reactions times.