Dibenzyl Ether Research Articles

Graphene Oxide: Carbocatalyst or Reagent?

AbstractMetal‐free heterogeneous carbon‐based materials have the potential to facilitate a wide range of organic transformations in an economical and environmentally‐friendly manner. However, the mechanism of their action is often obfuscated by their ill‐defined nature, so careful analysis of the reaction products is essential before they can be labelled “catalysts” in accordance with the IUPAC definition. We present here our findings on the archetypal “carbocatalytic” conversion of benzyl alcohol to benzaldehyde, in which graphene oxide is reduced and a major side product, dibenzyl ether, is also formed. Thus, our work reclassifies graphene oxide as a reagent and presents an important step in the proper evaluation of reactions in the nascent field of carbocatalysis.

Graphene Oxide: Carbocatalyst or Reagent?

Metal-free heterogeneous carbon-based materials have the potential to facilitate a wide range of organic transformations in an economical and environmentally-friendly manner. However, the mechanism of their action is often obfuscated by their ill-defined nature, so careful analysis of the reaction products is essential before they can be labelled "catalysts" in accordance with the IUPAC definition. We present here our findings on the archetypal "carbocatalytic" conversion of benzyl alcohol to benzaldehyde, in which graphene oxide is reduced and a major side product, dibenzyl ether, is also formed. Thus, our work reclassifies graphene oxide as a reagent and presents an important step in the proper evaluation of reactions in the nascent field of carbocatalysis.

A Novel Magnetic Solid Acid for Specially Cleaving the C‐O Bridged Bond in Dibenzyl Ether

AbstractA novel magnetic solid acid was prepared by immobilizing trifluoromethanesulfonic acid (TFMSA) and AlCl3 on a magnetic support (i. e., Fe3O4 coated by SiO2). Dibenzyl ether (DBE) which contains C−O bridged‐bond was used as a coal model compound to evaluate the activity of the catalyst for cleaving Calk‐O bonds in coal. The prepared magnetic solid acid was characterized by X‐ray diffraction, transmission electron microscopy, Fourier transform infrared spectrometer, scanning electron microscopy and energy dispersive spectrometer, and NH3‐temperature‐programmed desorption. The results show that the prepared catalyst possesses nanometer size, core‐shell structure and strong acidity. The Calk‐O bond in DBE can be cleaved at a temperature of as low as 413 K over the catalyst AlCl3‐TFMSA/Fe3O4/SiO2. The attack of H+ that generated from the magnetic solid acid and/or via hydrogen heterolysis on oxygen atom of DBE could be a crucial step for DBE hydrocracking over the magnetic solid acid.

Direct synthesis of hierarchically structured MFI zeolite nanosheet assemblies with tailored activity in benzylation reaction

The MFI zeolites with nanosheet assemblies morphology were prepared by a seed-assisted strategy using specially designed bolaform surfactant [C6H13-N+(CH3)2-C6H12-N+(CH3)2-(CH2)12-O-(p-C6H4)2-O-(CH2)12-N+(CH3)2-C6H12-N+(CH3)2-C6H13] [Br−]4 (C6-12-diphe) as a structure-directing agent. The MFI zeolite nanosheet assemblies were composed of MFI nanosheets with randomly organized structure, exhibiting a narrow mesopore distribution. By tuning the Si/Al ratios of MFI zeolite nanosheet assemblies from 60 to 10, the morphology of resultant zeolites changed from nanosheet stacks to house-of-cards-like structures, and to nanosponges. In addition, the porosity and Brønsted acid/Lewis acid ratio exhibited a parabola-type dependence on the Si/Al ratios of obtained zeolites, indicating that meso-/microporosity and acidity of MFI nanosheet assemblies can be systematically tailored by changing the constituents of zeolites. Catalytic performance of MFI zeolite nanosheet assemblies was investigated in the benzylation of benzyl alcohol with mesitylene. The results revealed that MFI zeolite nanosheet assemblies exhibited extraordinary catalytic activity compared to conventional ZSM-5 zeolite. The conversion of benzyl alcohol and selectivity (1,3,5-trimethyl-2-benzylbenzene vs dibenzyl ether) of zeolite catalysts were linearly dependent on the Brønsted acid/Lewis acid ratio, and they exhibited a parabola-type dependence on the Sext/SBET, indicating that a balance between acidity and porosity of zeolites can be realized to modulate the catalytic properties of MFI zeolite nanosheet assemblies guided by C6-12-diphe.

Indium-catalyzed Direct Conversion of Dibenzyl Ethers to Dibenzyl Sulfides Using Elemental Sulfur and a Hydrosilane and Its Application to the Preparation of Benzyl Selenides

Described herein is a catalytic system composed of an indium(III) compound, a hydrosilane and an easily handled form of elemental sulfur (S8) that effectively and directly catalyzes the sulfidation of dibenzyl ethers to produce dibenzyl sulfides. This system could also be applied to selenium in a straightforward conversion to dibenzyl selenides.

Quaternary ammonium functionalized Fe3O4 & P(GMA-AA-DVB) magnetic Janus particles as highly efficient catalysts for phase transfer reactions.

This work describes the preparation and catalytic performance of magnetic Janus quaternary ammonium phase transfer catalysts Fe3O4 & P(GMA-AA-DVB)N+(CH3)3OH- (MJPTCs). The morphologies, structures and other physical properties of the Janus catalysts prepared by a modified solvent thermal method were characterized by TEM, FTIR, TGA, VSM and XRD. The reaction of benzyl alcohol and benzyl bromide to generate dibenzyl ether was chosen as the model reaction to evaluate the catalytic activity of the MJPTCs. Besides, the influence of catalyst concentration and reaction temperature on catalytic efficiency was investigated in detail. The experimental results showed that the MJPTCs exhibited great catalytic activity with a conversion rate of 99% in only 2.5 h, and excellent reusability with a conversion rate of 97% after 8 cycles.

Ether modified poly(ether ether ketone) nonwoven membrane with excellent wettability and stability as a lithium ion battery separator

In this study, poly(ether ether ketone) is first chloromethylated to improve the solubility and is later used for nonwoven membrane fabrication by electrospinning. Finally, the chloromethyl group was converted to the ethyl ether group and dibenzyl ether group in a hot alkaline solution. The abundant polar groups endow the membrane with excellent wettability, reducing the contact angle to 0°. The polymer matrix is crosslinked by dibenzyl ether group, endowing the membrane with excellent stability (insolubility in many solvents, and ultra-low swelling in the electrolyte at 80 °C) and good anti-shrinkage property (0% at 180 °C). The electrospinning-fabricated membrane remains stable until 4.812 V (vs. Li+/Li), meeting the requirement for use in lithium ion batteries. The interwoven structure of the nonwoven membrane effectively gives rise to the high electrolyte uptake of 215.8%. The ionic conductivity of the electrolyte-swelled electrospinning-fabricated membrane is 51% higher than that of the electrolyte-swelled Celgard membrane. As a result, the lithium ion battery with this nonwoven membrane exhibits an enhanced rate performance (up to 42.5% higher than the lithium ion battery with a PP separator) and satisfactory cycling performance.

On the development of kinetic models for solvent-free benzyl alcohol oxidation over a gold-palladium catalyst

Bimetallic Au-Pd nanoparticles supported on TiO2 show excellent catalytic activity and selectivity to benzaldehyde in the solvent-free transformation of benzyl alcohol to benzaldehyde, where toluene is the main observed by-product, together with smaller amounts of benzoic acid, benzyl benzoate and dibenzyl ether. However, despite the industrial relevance of this reaction and importance of tuning the selectivity to the desired benzaldehyde, only a few attempts have been made in the literature on modeling the reaction kinetics for a quantitative description of this reaction system. A kinetic model for the oxidation of benzyl alcohol over Au-Pd is proposed in this paper. The model assumes that hydrogenolysis, disproportionation and dehydrogenation reactions may occur in parallel, and it has been found satisfactory after a model discrimination procedure was applied to a number of simplified candidate models developed from microkinetic studies. Despite its relative simplicity, the proposed model is capable of representing the reactant conversion and distribution of products observed in experiments carried out at different temperature, pressure and catalyst mass in a stirred batch reactor. Major findings include the quantitative evaluation of the impact of hydrogenolysis and disproportionation pathways on benzaldehyde production. At low temperature the disproportionation reaction is the dominant route to toluene formation, while hydrogenolysis dominates at high temperature.

A Novel Brønsted-Lewis acidic catalyst based on heteropoly phosphotungstates: Synthesis and catalysis in benzylation of p-xylene with benzyl alcohol

A novel Brønsted-Lewis acidic catalyst, Hf0.5[TEAPS]PW12O40, has been prepared by the replacement of protons in neat phosphotungstic acid with both organic and metal cations and characterized by FT-IR, Py-IR, XRD, TG-DTG, ICP-AES, BET, elemental analysis and n-butylamine potentiometeric titration techniques. This hybrid heterogeneous catalyst with both Brønsted and Lewis acidity can efficiently promote the conversion of dibenzyl ether, the self-condensation product of benzyl alcohol, to the benzylation products, as well restrain the polybenzylation of aromatics. As a result, it exhibits excellent catalytic activity and selectivity in the benzylation of p-xylene with clean benzylation reagent benzyl alcohol. Thus, an environmentally friendly route for the benzylation reaction of p-xylene with high atomic economy has been developed by this reusable Hf0.5[TEAPS]PW12O40 catalyst.

Synthesis of symmetrical α-alkyl- and α-arylalkylbenzyl and diarylmethyl ethers by HCl-catalyzed intermolecular dehydration

α-Alkyl-, α-arylalkyl-, and α-aryl-substituted benzyl alcohols were converted into the corresponding symmetrical dibenzyl ethers in the presence of a catalytic amount of 10% aqueous HCl both in methylene chloride and under solvent-free conditions. Analogous reactions in dioxane and on heating afforded mainly the corresponding arylalkenes, whereas symmetrical dibenzyl ethers were formed as minor products.

Consecutive loss of two benzyl radicals from the [M + Na]+ adduct ions of pyrogallol tribenzyl ether and its derivatives.

The electrospray ionization-collision-induced dissociation mass spectra of nine pyrogallol tribenzyl ethers, 2-10, and a catechol dibenzyl ether, 11, that bear various functional groups or larger structural extensions have been studied with respect to the occurrence of a highly characteristic consecutive loss of two benzyl radicals from the sodiated molecular ions, [M + Na]+. It is shown that this specific fragmentation reaction strongly dominates other fragmentation routes, such as loss of carbon monoxide, formaldehyde and water. In addition, elimination of benzaldehyde occurs as a minor fragmentation channel in most cases. In contrast to these aryl-benzyl ethers, the consecutive two-fold loss of C7H7• is suppressed in the [M + Na]+ ions of dibenzyl ethers derived from multiply benzylated gallocatechin and catechin, where the elimination of benzyl alcohol prevails the primary fragmentation almost completely. The secondary fragmentation of the [M + Na]+ ions, which also comprises the two-fold loss of C7H7•, as well as a remarkable primary fragmentation of a flavene-based congener leading to particularly stable sodium-free chromylium product ions is also presented. † Deceased.

Production of monocyclic phenols by the liquid-phase hydrogenolysis of benzofuran and dibenzyl ether using in situ hydrogen production from methanol

We herein report our study into the hydrogenolysis of benzofuran, a model compound for the poorly decomposable compounds derived from lignin, over Pt supported catalysts in methanol in the absence of gaseous hydrogen. In this in situ hydrogenolysis reaction system, it was elucidated that both hydrogen production from methanol and selective hydrogenolysis of the furan moiety proceeded simultaneously to yield monophenolic compounds and gaseous hydrogen. This in situ hydrogenolysis reaction was investigated at temperatures between 180 and 220 °C and with reaction times ranging from 1 to 48 h. We found that the hydrogenolysis reaction was accelerated with increased hydrogen concentrations in the solvent. The molar ratio of consumed hydrogen to net hydrogen production increased gradually upon increasing the reaction temperature and time. In addition, the in situ hydrogenolysis of benzofuran under a hydrogen gas atmosphere revealed that the hydrogen produced in situ was more effective in the reaction than gaseous hydrogen, likely due to the dissolution and diffusion resistances of the solvent. Furthermore, dibenzyl ether was hydrogenolyzed to give monocyclic aromatic compounds under the same reaction conditions, suggesting that this in situ hydrogenolysis process could be effective in converting the by-products obtained during lignin depolymerization into valuable aromatic compounds.

Reductive Deoxygenation of Dibenzyl Ethers via Nickel Catalysis

Reductive Deoxygenation of Dibenzyl Ethers via Nickel Catalysis

Tubulin-binding dibenz[c,e]oxepines: Part 2. Structural variation and biological evaluation as tumour vasculature disrupting agents

5,7-Dihydro-3,9,10,11-tetramethoxybenz[c,e]oxepin-4-ol 1, prepared from a dibenzyl ether precursor via Pd-catalysed intramolecular direct arylation, possesses broad-spectrum in vitro cytotoxicity towards various tumour cell lines, and induces vascular shutdown, necrosis and growth delay in tumour xenografts in mice at sub-toxic doses. The biological properties of 1 and related compounds can be attributed to their ability to inhibit microtubule assembly at the micromolar level, by binding reversibly to the same site of the tubulin αβ-heterodimer as colchicine 2 and the allocolchinol, N-acetylcolchinol 4.

Light-Sheet Fluorescence Microscopy: Chemical Clearing and Labeling Protocols for Ultramicroscopy.

Light-sheet microscopy is an effective technique in neuroscience, developmental biology, and cancer research for visualizing and analyzing cellular networks and whole organs in three dimensions. Because this technique requires specimens to be translucent they commonly have to be cleared before microscopy inspection. Here, we provide 3DISCO based protocols for preparing cleared samples of immuno-stained neural networks, lectin-labeled vascular networks, and Methoxy-X04 labeled beta-amyloid plaques in mice. 3DISCO utilizes the lipophilic solvents tetrahydrofuran (THF) and dibenzylether (DBE) for dehydration and successive clearing. Crucial steps for obtaining transparent tissues and preserving the fragile endogenous GFP are the transcardial perfusion, as well as the proper implementation of the 3DISCO clearing process using peroxide free chemicals. We further provide a protocol for resin embedding of 3DISCO cleared specimens that allows long term archiving of samples for years with virtually no loss in signal quality.

Enzymatic Synthesis of a Bio-Based Copolyester from Poly(butylene succinate) and Poly((R)-3-hydroxybutyrate): Study of Reaction Parameters on the Transesterification Rate.

The enzyme-catalyzed synthesis of fully biobased poly(3-hydroxybutyrate-co-butylene succinate) (poly(HB-co-BS)) copolyesters is reported for the first time. Different Candida antarctica lipase B (CALB)-catalyzed copolyesters were produced in solution, via a one-step or a two-step process from 1,4-butanediol, diethyl succinate, and synthesized telechelic hydroxylated poly(3-hydroxybutyrate) oligomers (PHB-diol). The influence of the ester/hydroxyl functionality ratio, catalyst amount, PHB-diol oligomer chain length, hydroxybutyrate (HB) and butylene succinate (BS) contents, and the nature of the solvent were investigated. The two-step process allowed the synthesis of copolyesters of high molar masses (Mn up to 18 000 g/mol), compared to the one-step process (Mn ∼ 8000 g/mol), without thermal degradation. The highest molar masses were obtained with diphenyl ether as solvent, compared with dibenzyl ether or anisole. During the two-step process, the transesterification rate between the HB and BS segments (i) increased with increasing amount of catalyst and decreasing molar mass of the PHB-diol oligomer, (ii) decreased when anisole was used as the solvent, and (iii) was not influenced by the HB/BS ratio. Tendencies toward block or random macromolecular architectures were observed as a function of the reaction time, the PHB-diol oligomer chain length, and the chosen solvent. Immobilized CALB-catalyzed copolyesters were thermally stable up to 200 °C. The crystalline structure of the poly(HB-co-BS) copolyesters depended on the HB/BS ratio and the average sequence length of the segments. The crystalline content, Tm and Tc decreased with increasing HB content and the randomness of the copolymer structure.

Special features of gas chromatography determination of dibenzyl ether hydroperoxide impurity in benzyl alcohol

Chromato–mass spectrometric analysis of a benzyl alcohol sample has revealed the presence of dibenzyl ether hydroperoxide C6H5CH(OOH)OCH2C6H5 impurity showing the retention index 1894±10 on a standard stationary phase (RTX-5). A special feature of this hydroperoxide is its stability under conditions of gas chromatography separation (retention temperature 190°С). This has been confirmed by the measurement of the analytical signal between the chromatographic peaks of the hydroperoxide and the major product of its decomposition (benzyl benzoate). From this criterion, dibenzyl ether hydroperoxide is more stable that, for instance, monomethyl phthalate.

Complete hydrocracking of dibenzyl ether over a solid acid under mild conditions

A novel solid acid was prepared by impregnating trifluoromethanesulfonic acid (TFMSA) onto mesoporous ZrO2 coated attapulgite (MPZCA) via one-pot synthesis method. Dibenzyl ether (DBE) was used as a coal-related model compound to evaluate the catalytic activity of TFMSA/MPZCA for cleaving Calk–O bridged bonds in low-rank coals. The results show that DBE conversion over TFMSA/MPZCA could reach 100% at 160°C in C2H5OH without charging H2. TFMSA/MPZCA proved to be stable after 4 cycles with only slight loss in catalytic activity. Moreover, a H+ transfer mechanism was proposed, which reasonably deduces possible pathways for DBE hydrocracking over TFMSA/MPZCA.

Thermolysis of biomass-related model compounds and its promotion on the thermal dissolution of coal

The thermolysis of biomass-related model compounds was carried out and its promotion on the thermal dissolution of coal was probed in this study. Benzyl phenyl ether was easily to pyrolyze than dibenzyl ether, and the thermolysis conversions of benzyl phenyl ether and dibenzyl ether were 98.3 and 32.4% at 360 °C respectively. The product analysis of the thermolysis suggests that the pyrolysis of the biomass-related model compounds follows the radical reaction route and some phenyl oxygen free radicals are formed in the process. Addition of 2% phenol could obviously increase the thermolysis conversion of dibenzyl ether, suggesting that the free radicals formed from phenol can promote the pyrolysis of dibenzyl ether. Addition of 10% benzyl phenyl ether could obviously promote the thermal dissolution of Shenfu sub-bituminous coal, and the thermal dissolution yield of Shenfu sub-bituminous coal could be increased by 20.8% at 360 °C. The enhancement of thermal dissolution of Shenfu coal by benzyl phenyl ether can be attributed to that the benzyloxy and phenoxy radicals formed from the thermolysis of benzyl phenyl ether attack the coal molecules, thus promoting the depolymerization of coal.

A straightforward green synthesis of N-(tert-butylsulfinyl)imines

A straightforward and environment-friendly protocol for the synthesis of valuable chiral N-(tert-butylsulfinyl)imines has been developed. Different from traditional process with benzaldehydes as substrates, arylmethyl alcohols, benzylthiol, dibenzyl ether, thioether, and disulfide are used as alternative substrates to react with tert-butanesulfinamide in the presence of KOtBu under air for the synthesis of chiral N-(tert-butylsulfinyl)imines. This is a transition metal-free, mild, cost-effective, and simple process.