Reaction Of Acetate Research Articles

Silylium‐Catalyzed Alkynylation and Etherification Reactions of Benzylic Acetates

AbstractAddition of catalytic amounts of bistriflimide triggers useful coupling reactions of benzyl acetates with trimethyl(alkynyl)silanes and trimethyl(alkoxy)silanes to afford propargyl arenes and benzyl alkyl ethers, respectively. The added acid assists the release of reactive trimethylsilylium ion into the reaction media, which were found to act as the ultimate catalytic species responsible for the C−C and the C−O forming steps. The cationic nature of these coupling processes is documented.

Highly active and scalable SO3H functionalized carbon catalyst synthesized from bagasse for transformation of bio-based platform chemicals into fuel precursors and its in-depth characterization studies

Scalable synthesis of SO3H functionalized carbon from sugar industry waste (bagasse) and detailed structural characterization and activity were reported. The incorporation of SO3H functionality groups on the carbon surface and the growth of the aromatic carbon framework was supported by FT-IR and 13C CP-MAS NMR analysis. The hydrothermally synthesized carbon exhibited total acidity of 5 mmol/g and uniform distribution of sulphur on the surface of carbon. The synthesized catalyst was found to be efficient for the acetalization, alkylation and alcoholysis reactions and exhibits excellent stability during the reactions. Various bio-derived carbonyl compounds were demonstrated by the solvent-free acetalization of bio-derived glycerol gives 50–100% conversion and 52–98% selectivity towards solketal derivatives at room temperature. The synthesized catalyst's reactivity was better than the commercially used Brønsted/Lewis acids. Furthermore, the SO3H functionalized carbon was also used for alcoholysis followed by ring-opening of furfuryl alcohol, giving 67–98% selectivity towards alkyl levulinates with complete conversion of furfuryl alcohol. The mechanistic pathway suggests that the alcoholysis reaction goes through three different intermediates (2-alkoxymethylfuran, 4,5,5-trialkoxypentan-2-one, and 5-hydroxy-4,5-dialkoxypentan-2-one) to produce the alkyl levulinates. Additionally, the catalyst was tested for solvent-free condensation of 2-methylfuran with various carbonyl compounds to selectively produce an excellent yield of fuel precursors (for C12-C15 hydrocarbons) at 60 °C. The catalyst was reused up to four cycles with 14% loss in the conversion of furfural for acetalization of glycerol, and negligible losses in the alkylation of 2-methylfuran were observed.

Sunflower-Assisted Bio-Derived ZnO-NPs as an Efficient Nanocatalyst for the Synthesis of Novel Quinazolines with Highly Antioxidant Activities.

The present report presents a green method for the rapid biogenic synthesis of nanoparticles that offers several advantages over the current chemical and physical procedures. It is easy and fast, eco-friendly, and does not involve any precious elements, hazardous chemicals, or harmful solvents. The synthesized ZnO nanoparticles were characterized using different techniques, such as UV-Visible spectroscopy. The surface plasmon resonance confirmed the formation of ZnO nanoparticles at 344 nm, using UV-Visible spectroscopy. The leaf extract acts as a source of phytochemicals and is primarily used for the reduction and then the formation of stable ZnO nanoparticles by the characteristic functional groups of the extract; the synthesized ZnO nanoparticles were identified using FTIR spectroscopy. The crystalline nature of ZnO-NPs was confirmed via powder X-ray diffraction (XRD). Size and morphology were measured via high resolution transmission electron microscopy (HR-TEM) analysis. The stability of the nanoparticles is established using dynamic light scattering (DLS) and thermogravimetric analysis (TGA). The synthesized ZnO nanoparticles have been found to be a good and efficient catalyst for the synthesis of novel 1,2-dihydro quinazoline derivatives under the green method via a one-pot reaction of 2-amino benzophenone, 1,3-diphenyl-1H-pyrazole carbaldehydes, and ammonium acetate. The synthesized compounds (4a–o) were characterized by the 1H NMR, 13C NMR, and HRMS spectra and were further validated for free-radical scavenging activity. The synthesized ZnO nanoparticles exhibited good antioxidant activity.

Stable anodes for lithium-ion batteries based on tin-containing silicon oxycarbonitride ceramic nanocomposites

Tin nanoparticles are a promising candidate for Li-ion battery anodes to replace carbon materials due to their high theoretical Li-ion storage capacity (994 mAh/g), which is much higher than that of graphite (372 mAh/g). However, the poor cycling stability of tin emerged from large volume expansion, and contraction remains a challenging issue. To overcome these limitations, we designed Sn-containing silicon oxycarbonitride ceramic nanocomposites (Sn/SiOCN) by the chemical reaction of tin acetate with poly(vinyl)silazane Durazane 1800 in ice bath under argon, followed by the pyrolysis of as-obtained precursors at 1000 °C for 3 h under argon atmosphere. The Sn/SiOCN nanocomposites with different Sn contents are tested as anodes for lithium-ion batteries, delivering a high-discharge capacity of ∼320 mAh/g at a current density of 2220 mA/g and extremely long cycling stability even at high charging rates (approximately 90% of the capacity is maintained after 1000 cycles). The outstanding electrochemical performance of Sn/SiOCN nanocomposites can be attributed to the improved charge transfer process due to the incorporation of metallic Sn nanoparticles into the amorphous SiOCN ceramic matrix, as revealed by electrochemical impedance spectroscopy (EIS) characterization. In situ XRD results confirm the formation of lithium-rich alloy phase Li7Sn2 during the lithiation process.

Catalytic Intramolecular Cyclization of Alkynyl Cyclic Acetals via Chemoselective Activation Leading to a Phenanthrene Core

Abstract An intramolecular cyclization reaction of alkynyl cyclic acetals to synthesize various phenanthrene derivatives in the presence of silver triflate (AgOTf) or boron trifluoride etherate (BF3·OEt2) as catalysts has been developed. By using AgOTf or BF3·OEt2 appropriately depending on the substituents various alkynyl cyclic acetals were converted to the corresponding phenanthrene derivatives. Investigations of reaction mechanisms, X-ray structure of the product, and computational density functional theory (DFT) study suggested that the reaction proceeds via alkyne activation (π-activation) or acetal activation (σ-activation) pathways based on π- or σ-Lewis acidities.

Polyaromatic Carboxylate Ligands Based Zn(II) Coordination Polymers for Ultrasound-Assisted One-Pot Tandem Deacetalization–Knoevenagel Reactions

Solvothermal reactions between the polyaromatic group containing carboxylic acid pro-ligands 5-{(pyren-1-ylmethyl)amino}isophthalic acid (H2L1) and 5-{(anthracen-9-ylmethyl)amino}isophthalic acid (H2L2) with Zn(NO3)2·6H2O led to the formation of the new 1D coordination polymer [Zn(L1)(NMF)]n (1) and four other coordination polymers, [Zn(L1)(DMF)]n (2), [Zn(L1)(4,4′-Bipy)]n (3), [Zn(L2)(DMF)(H2O)2]n·n(H2O) (4) and [Zn2(L2)2(DMF)(CH3OH)]n (5), which were previously reported by our group. Single crystal X-ray diffraction analyses revealed that the CP 1 has a one-dimensional (1D) double-chain-type structure similar to that of CP 2. For CP 3, the assembly of the Zn(II) ion with a deprotonated L12− ligand and 4,4′-bipyridine produces a 3D network. CP 4 and 5 exhibit 1D linear and 2D layered-type structures. The ultrasound-assisted tandem reactions promoted by CPs have not yet been well studied. Thus, in the present work, we have investigated the catalytic activities of the newly synthesized CP 1, as well as of the other CPs 2–5, towards the tandem deacetalization–Knoevenagel condensation reactions of various acetals under ultrasonic irradiation. They proved to be highly efficient, with special emphasis on catalyst 1, which completely converted the substrate (benzaldehyde dimethyl acetal) into the desired product (2-benzylidenemalononitrile) after 2 h. The stability of the catalysts, namely regarding the action of ultrasonic radiation, was demonstrated by their reuse, where only a slight loss of activity was observed after four cycles. Heterogeneity was also demonstrated, and no leaching was detected over the various cycles.

Catalyst-free synthesis of tetrahydrodipyrazolopyridines via an one-pot tandem and green pseudo-six-component reaction in water

BackgroundA new, green and environmentally friendly protocol has been developed for the synthesis of tetrahydrodipyrazolopyridine derivatives. The structures of these products were determined in terms of melting point, FTIR, NMR and Mass spectroscopy.ResultsThe tetrahydrodipyrazolopyridine derivatives were synthesized in water through a catalyst-free pseudo-six-component reaction of hydrazine hydrate, ethyl acetoacetate, ammonium acetate and aldehyde at room temperature.ConclusionsThis novel procedure has some advantages such as aqueous media, high yield and simple work-up.Graphical

Tandem [3+2]-cycloaddition/homo-Baldwin rearrangement of silyl nitronates and donor-acceptor cyclopropenes. A novel approach to polysubstituted aziridines starting from nitro compounds

The synthesis of substituted N-silyloxy aziridines through reaction of silyl nitronates and enol diazo acetates is described. The process involves in situ transformation of enol diazo acetates into donor-acceptor cyclopropenes, their [3 + 2]-cycloaddition with nitronates and subsequent rearrangement of fused isoxazolidine intermediates. Depending on the substrate type, generation of prerequisite cyclopropenes could be promoted by various rhodium carboxylates (acetate, octanoate) in catalysts loadings as low as 50 ppm. Relative configuration of all three stereocenters in aziridine ring was established by NMR techniques and supported by quantum chemical calculations.

Ordered WOx/mesoporous SnO2 catalysts with excellent acetalization performance for producing bio-additives from glycerol

• Highly ordered mesoporous WOx/SnO2 catalysts have been applied to the glycerol acetalization reaction. • Mesoporous WOx/SnO2 catalysts exhibited excellent catalytic performance in batch-type and continuous flow-type processes for catalytic synthesis of solketal from glycerol. • In a batch type process, 100% glycerol conversion and a solketal yield of 97.4% were achieved. Highly ordered WO x /mesoporous SnO 2 (WO x /meso‑SnO 2 ) catalysts with varying WO x loadings of (5 ∼ 20) wt% displaying excellent catalytic performance were demonstrated in the acetalization of glycerol with acetone. The synthesized catalysts were analyzed using various techniques including X-ray diffraction, N 2 -isotherm, electron microscopy, H 2 temperature programmed reduction, raman spectroscopy, and thermogravimetric analysis. For the acetalization of glycerol with acetone, the most active catalyst was found to be WO x /meso‑SnO 2 with 20 wt% WO x , and the maximum conversion of glycerol (100%) was obtained after 2 h at 20 °C, providing 97.4% selectivity (97.4% yield) for the five-membered product (solketal), due to the presence of a large number of acidic sites on the surface of the catalyst. The catalytic activity of 20 wt% WO x /meso‑SnO 2 was also studied in a flow reactor. Tests were carried out at 30 °C, acetone/glycerol=30, WHSV=(4 or 8) h − 1 , and atmospheric pressure for 24 h. The catalytic results showed that, when the WHSV was 4 h − 1 , after 24 h of time-on-stream, both the glycerol conversion of (100 to 97.9)% and solketal yield of (97.5 to 93.6)% slightly decreased. This result suggests the potential of the 20 wt% WO x /meso‑SnO 2 catalyst for the industrial acetalization of glycerol.

KCC-1-nPr-NH-Arg as an efficient organo-nanocatalyst for the green synthesis of 1,8-dioxo decahydroacridine derivatives.

In the present work, an innovative biocompatible heterogeneous organo-nanocatalyst is prepared based on the grafting of arginine amino acid on the channels and pores of dendritic fibrous nano silica. The designed organo-nanocatalyst (KCC-1-nPr-NH-Arg) was characterized by using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, map analysis, and adsorption/desorption instruments. The results of analysis show that the engineered catalyst has uniform fibrous spheres and dendritic structure with high surface area (104.9 m2 /g) and great pore volume (0.83 cm3 g-1 ). Because of exceptional dendritic structure of the prepared organo-nanocatalyst, the active sites are available and the difusion and adsorption capacity of the reagents and products increase in the pores and channels of the catalyst. Hence, KCC-1-nPr-NH-Arg was used as an capable heterogeneous basic nanocatalyst in the synthesis of 1,8-dioxo decahydroacridine derivatives from the one-pot four component reactions of aromatic aldehydes, dimedone, and ammonium acetate in solvent free conditions with shorter reaction times (13-35 minutes) and higher yields (94%-98%) in evaluation with other reported works. It is expected that the green organo-nanocatalyst can be used to synthesize other organic compounds.

Cesium Loaded on an Al-Modified Silica Support Catalyst for Methyl Acrylate Synthesis by Aldol Condensation of Methyl Acetate and Formaldehyde

An Al-modified silica-supported cesium catalyst was prepared by an incipient wetness impregnation method for the gas-phase aldol condensation reaction of methyl acetate and formaldehyde. The effect of the Al-modified silica support on the structure, specific surface area, and the acid property was studied using X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption–desorption, NH3-temperature programmed desorption, X-ray photoelectron spectroscopy, and Py-IR. Adding the cesium species, the Cs–Al/SiO2 catalyst performed well based on the evaluation results in a fixed-bed reactor. A combination of these characterization and testing results manifests the influence of acid–base properties on the catalytic activity. It was found that the selectivity was related to the amount of weak acid sites and medium-strong base sites. The highest selectivity of methyl acrylate (MA) was obtained at T = 355 °C, LHSV = 0.6 h–1, and Ma/FA/MeOH molar ratio = 1:1:2 over the 10% Cs–3% Al/SiO2 catalyst. Finally, the performance of the optimized catalyst did not exhibit an obvious decrease via three times in situ regeneration.

From Biomass to the KarrikinsviaSelective Catalytic Oxidation of Hemicellulose‐Derived Butyl Xylosides and Glucosides

AbstractMembers of the karrikin family of bioactive small molecules are known to promote germination of a range of plants following large scale fires. As a result, they are relevant and interesting compounds. This report describes their synthesis from a biomass‐derived product stream. During work to fractionate biomass with the goal of obtaining high quality lignins, an interesting co‐product stream derived from the hemicellulose in the biomass, was obtained. Whilst many applications of this co‐product stream can be proposed, in this case the major monosaccharides have been converted to relevant karrikins in short reaction sequences. Key results include a highly selective catalytic oxidation reaction, conversion of the resulting ketone to a butenolide by two alternative approaches, a selective acetal reductive opening reaction, X‐ray crystallographic analysis of two compounds and detailed comparison of the final products with previous literature reports. Only through successful use of all the components generated during biomass refining, can economic sustainability be potentially achieved.

Use of Iridium‐Catalyzed Transfer Vinylation for the Synthesis of Bio‐Based (bis)‐Vinyl Ethers

AbstractThe iridium catalyzed transfer vinylation of bio‐based polyols and of other alcohols and phenols with interesting structural motifs was accomplished with vinyl acetate in 2‐MeTHF as a green solvent. The optimized synthetic procedure has as main advantages the use of catalytic instead of stoichiometric amounts of base and high selectivities towards the formation of bis‐vinyl ethers as a result of the suppression of the acetal formation reaction that typically occurs in the vinylation of diols. In addition, the thermodynamically preferred transesterification reaction leading to the acetate esters and bis‐esters was completely suppressed. DFT calculations revealed an iridium‐acetate complex as the active catalytic species and they disclosed the importance of the carbonyl group of vinyl acetate for the formation of a six‐membered cyclic intermediate.magnified image

Post Synthesis Architectural Pore Modification of Mobil Five (MFI) Zeolite for Enhancing its Catalytic Activity

Dealumination and desilication of synthesized nanoporous MFI samples have been investigated in order to create and modify the acidity of the samples. Desilication of the synthesised samples carried out by treating the samples by an alkaline solution leads to an impressive nanoporosity development with increase in the acidic properties, while dealumination of the synthesised samples carried out by treating the samples by an acidic solution mainly modifies the acidity of the synthesised MFI zeolite. The present study shows that application of alkaline and acidic treatments results in modification of the MFI zeolites with independently tailored pore architecture and acidic properties. Such modification enhances the catalytic activity of the samples under different conditions. XRD as well as FT-IR studies have been carried out to characterize the formation of the parent as well as modified MFI zeolite. Specific surface area, pore diameter and pore volume of the samples were studied by N2 adsorption-desorption isotherm. BET specific surface area was found to increase with increase in Si/Al molar ratio. The thermal stability of the samples was studied using thermal gravimetric analysis. The synthesised samples were found to show weight loss in three different ranges. The shape and size of crystalline MFI samples were investigated with SEM analysis. The catalytic activity of synthesized parent and modified MFI zeolites were investigated by the acetalization reaction of cyclohexanone with methanol under different reaction conditions. The % conversions of the dealuminated samples were found to be greater than that of the desilicated catalyst.

Utility of arylglyoxal hydrates in synthesis of 4-aroyl-[1,3,5]triazino[1,2-a]benzimidazol-2(1H)-imines and 5-aryl-2-phenyl-4H-imidazol-4-imines.

Nucleophilic substitution reaction for arylglyoxal hydrates (AGs-hydrate) was studied via their reaction with some mono- and multi-nucleophilic reagents in the presence of sodium ethoxide as basic catalyst. Thus, reaction of phenylglyoxal hydrate (1a) with hydrogen sulfide and/or ammonium acetate afforded the corresponding 2-hydroxy-2-mercapto-1-phenylethanone (2) and 2-oxo-2-phenylethanimidamide (3), respectively. Heterocyclization reaction of AGs-hydrate 1a-f with 1-(1H-benzimidazol-2-yl)guanidine (4) gave 4-aroyl-[1,3,5]triazino[1,2-a]benzimidazol-2(1H)-imines 5a-f. Also, a series of 5-aryl-2-phenyl-4H-imidazol-4-imines 7a-d was synthesized via one-pot multicomponent reaction of AGs-hydrate 1a-d, benzonitrile (6) and ammonium acetate. Imidazole-4-imines 7a-d can be also prepared using other route via multicomponent reaction of AGs-hydrate 1a-d, benzenecarboximidamide acetate (8) and ammonium acetate.

A density functional theory study on the effect of acetylene on vinyl acetate synthesis from acetoxylation of ethylene over Pd-Au catalysts

In this work, the reaction network of acetylene on Pd-Au catalyst was constructed firstly, and the single adsorption configurations and adsorption energies and electronic properties of key species in the reaction network were calculated with Density Functional Theory (DFT). It was found that most of the species tend to be adsorbed on the sites around Pd atoms and acetylene does not occupy the active site of ethylene. Then the energy barrier and reaction energy of the related reaction of acetylene on the Pd-Au surface and the geometric configuration of the transition state were calculated through DFT. Acetylene is highly reactive and oxidation, hydrogenation and polymerization were easy to occur. Among all the reactions, the oxidation reaction had the most competitive advantage. CO2 was the most in the final product, followed by the intermediate product C2H3. CO2 and C2H3 have no adverse effect on the reaction system, so the trace of acetylene in the raw material ethylene had a very weak effect on the vinyl acetate reaction system.

Postsynthetic Defect Formation in Three-Dimensional Hofmann-Type Coordination Polymers and Its Impact on Catalytic Activity.

We report a systematic investigation of postsynthetic defect formation in Hofmann-type coordination polymers M(pz)[M'(CN)4] (M = Fe2+, Co2+, Ni2+; M' = Pd2+, Pt2+; pz = pyrazine). These compounds readily undergo selective ligand exchange at the pyrazine site when immersed in methanol (MeOH) at ambient temperature. The ligand exchange changes the chemical formula to M(pz)1-x(MeOH)2x[M'(CN)4] (0 < x < 0.3), affording a defective coordination environment around the M ions. The defect concentration is highly dependent on the combination of the metal ions and solvent species, reaching the defect concentration of ca. 30% (x ∼ 0.3) at maximum. The magnetic state of one such coordination polymer gives an additional control of the defect formation, making the compound less susceptible to the ligand exchange at the low-spin state. Structures that form the defects at a high concentration function as catalysts and promote an acetalization reaction heterogeneously by providing Lewis acidic sites. The solvent-dependent character of the defect formation can be used to control the catalytic activity of the active compounds, demonstrating a facile defect engineering for functionalizing solid materials.

Synthesis of 2-acetal-1,3-enynes by Sonogashira reaction of bromovinyl acetals with alkynes: application to the formal synthesis of a glucagon antagonist

The preparation of functionalized 1,3-enynes bearing an acetal moiety at the 2-position has been studied through Sonogashira reaction of bromovinyl acetals with various alkyl- and aryl-substituted terminal alkynes.

Vanadium-substituted polycationic Al-oxo cluster in a porous ionic crystal exhibiting Lewis acidity.

Herein we present the first example of a vanadium-substituted δ-Keggin Al13-based (Al28V4) porous Ionic crystal (PIC) (Al28V4-PW9V3). Structural and theoretical studies suggested that Al28V4 may exhibit Lewis acidity, which was confirmed by acetalization reaction with Al28V4-PW9V3 as a solid catalyst and investigations with pyridine or 2,6-lutidine as basic probe molecules. A comparative study with the δ-Keggin Al13 monomer based PIC indicated that the vanadium-substitution gave rise to the Lewis acidity.

Synthesis of the two isomers of heteroleptic Rh12L6L′6metal–organic polyhedra by screening of complementary linkers

We have synthesised and characterised the two possible isomers of heteroleptic trigonal antiprismatic M12L6L'6 MOPs by screening reactions of rhodium acetate with different pairs of complementary dicarboxylate linkers. The resulting 12 new MOPs (eight of isomer A + four of isomer B) are microporous in the solid state, exhibiting Brunauer-Emmett-Teller (BET) surface areas as high as 770 m2 g-1.