Synthesis Of Ethers Research Articles

Highly dispersed Cs2O/SiO2 catalysts for selective intramolecular dehydration of ethylene glycol monoethyl ether to ethyl vinyl ether

Highly selective intramolecular dehydration of ethylene glycol monoethyl ether to ethyl vinyl ether over dispersed Cs2O/SiO2 catalysts.

Dense arrangement of crown ethers in graphene: novel graphitic carbon oxides with enhanced optoelectronic properties.

Incorporating crown ethers into a graphene lattice presents an efficient means of tuning its properties and expanding its range of potential applications. This study employed density functional theory calculations to introduce a series of novel graphitic carbon oxides through the dense arrangement of crown ethers featuring varying cavity sizes within the graphene structure. These newly developed graphitic carbon oxides exhibit thermodynamic and dynamic stability. They also manifest improved stability relative to previously reported graphene oxides with similar oxygen content. Notably, a robust linear relationship is observed between the cohesive energies and the proportion of oxygen atoms. The electronic properties of these graphitic carbon oxides span a spectrum of characteristics, including semi-metallic, metallic, and semi-conducting behavior. Their calculated band gaps range from 0.11 eV to 4.38 eV. Specifically, our analysis reveals that C6G-1, characterized by its largest crown ether-like nanopore with six oxygen atoms, holds potential as a material for photocatalytic water splitting. Moreover, these materials exhibit anisotropic optical properties, showcasing a significant enhancement in absorption within the infrared and visible regions relative to pristine graphene. Given the successful experimental synthesis of crown ether in graphene, we anticipate that our findings will contribute to the widespread utilization of graphene derivatives in low-dimensional electronic, catalytic, and optical devices.

Evolution in the asymmetric synthesis of biaryl ethers and related atropisomers.

Axially chiral biaryl ethers and related compounds hold valuable potential in natural products, medicinal chemistry, and catalysis; however, their asymmetric syntheses have always been overlooked compared to other biaryl/hetero-biaryl atropisomers. Unlike the later class molecules bearing a single chiral axis, the former category possesses a unique type of atropisomerism bearing two potential axes. Due to their great importance in diverse research domains, catalytic atropselective biaryl ether synthesis has recently witnessed an upsurge. This highlight article provides an elaborated view on the developments of catalytic synthetic methods that have been explored to achieve dual axial chirality in biaryl ethers and related scaffolds.

Dioxane promoted photochemical O-alkylation of 1,3-dicarbonyl compounds beyond carbene insertion into C-H and C-C bonds.

A photochemical synthesis of enol ethers and furan-3(2H)-ones from 1,3-dicarbonyl compounds and aryl diazoacetates has been developed. Significantly, 1,4-dioxane promoted O-alkylation of various 1,3-dicarbonyl compounds beyond previous carbene insertion into C-H and C-C bonds has been disclosed.

Synthesis of oxime ethers via a formal reductive O-H bond insertion of oximes to α-keto esters.

This study describes an efficient approach to access oxime ethers via P(III)-mediated O-H bond insertion reaction of oximes with α-keto esters. The strategy involves the protonation of in situ generated Kukhtin-Ramirez adducts, followed by SN2-type reaction. Important features include a good functional group tolerance, operational simplicity, and application to gram scale synthesis and the synthesis of an acaricide.

Pd(II)-catalyzed hydroarylations/hydroalkenylations of terminal alkynes: regioselective synthesis of allylic, homoallylic, and 1,3-diene systems.

A Pd-catalyzed regioselective hydroarylation of terminal alkynes containing a heteroatom has been developed via carbopalladation for the synthesis of allylic ethers, amines, and homoallylic alcohols. Moreover, hydroalkenylation of alkynes produces a variety of stereodefined 1,4-dienes with high regioselectivity. The important features of the present protocol are that it is highly regioselective, operationally rapid, and scalable with a huge substrate scope using only 3 mol% of PdCl2(PPh3)2 catalyst in the presence of a mild base KOAc.

Unlocking a reductive hydroalkoxylation cascade for the stereoselective synthesis of cyclic ethers: total synthesis of (±)-isolaurepan and (±)-cis-lauthisan.

A Lewis acid-mediated, 5/6/7/8-endo-dig reductive hydroalkoxylation cascade on enynols gives expeditious, diastereoselective access to small and medium ring cyclic ethers with a long aliphatic side chain. The brevity of the approach allowed a 4-step, stereoselective total synthesis of (±)-isolaurepan and (±)-cis-lauthisan.

Novel chalcone-based crown ethers: synthesis, characterization, antioxidant activity, biological evaluations, and wastewater remediation.

Macrocycles play a pivotal and indispensable role within the realms of both medicine and industry. In the course of our research endeavors, we have successfully synthesized five distinct macrocyclic chalcone entities, each showcasing remarkable biological and anti-oxidative properties. Furthermore, these compounds exhibit exceptional promise as potent agents for the removal of dyes in wastewater treatment processes. The synthesis of these key constituents was achieved through the judicious application of the Robinson ether synthesis and Claisen-Schmidt condensation reactions. The structures of compounds 1a-f and 2a-e were characterized by using analytical techniques such as FTIR, 1H NMR, 13C NMR, and DEPT 13C NMR spectroscopy. These macrocycles also underwent in vitro assessments to measure their antibacterial activity using the agar well diffusion method. The results revealed that the macrocyclics were more sensitive to Gram-positive than Gram-negative bacteria. For example, compound 2d exhibited an inhibition zone of 20 mm at 150 ppm. The antioxidant activity as determined via the DPPH method established that all tested compounds showed moderate radical-scavenging ability. Specifically, compound 2e (at 1000 ppm) exhibited antioxidant activity of 79% inhibition of radicals, in comparison to 90% for the standard ascorbic acid. The latter was demonstrated by using methylene blue as an adsorbate under simulated wastewater conditions. Outstandingly, the most effective compounds were 2d and 2c, which achieved removal rates of 96.54% and 92.37%, respectively, for methylene blue dye.

Traditional, one-pot three-component synthesis and anti-bacterial evaluations of some new pyrimidine derivatives

In this study, a novel series of pyrimidine compounds featuring azo linkages was synthesized via a sequence of stepwise and one-pot three-component reactions. The synthetic process commenced with the diazotization of 3-chloro-4-methyl aniline, followed bycoupling reaction with 4-hydroxy acetophenone, yielding the azo molecule denoted as 1-(3-((3-chloro-4-methylphenyl)diazenyl)-4-hydroxyphenyl)ethan-1-one. Subsequently, this compound underwent benzylation with benzyl bromide by Williamson ether synthesis, leading to the formation of 1-(4-(benzyloxy)-3-((3-chloro-4-methylphenyl)diazenyl)phenyl)ethan-1-one. The resultant azo-benzyloxy compound was then subjected to both classical and one-pot methodologies to synthesize pyrimidine derivatives, from results obtained from one pot reaction were in good yield. Structural elucidation of the newly synthesized compounds was characterized by spectral analysis, including FT-IR, 1H NMR, 13C NMR, and 13C-DEPT-135-NMR. The spectroscopic data confirmed the integrity of the molecular structures. Lastly, certain pyrimidine derivatives were evaluated for their antimicrobial activity against two strains of bacteria, namely Staphylococcus aureus and Escherichia coli. The results revealed that as the increasing of concentration, the sensitivity increased as reached 800 µg /mL no growth of bacterial was seen, It is also notable that the synthesized compounds have antimicrobial efficacy against both bacterial types.

Experimental study and comprehensive kinetic modeling of the direct dimethyl ether synthesis on Cu/ZnO/ZrO2 and H-FER-20

In the direct dimethyl ether (DME) synthesis, the combination of Cu/ZnO/ZrO2 (CZZ) and H-FER-20 (FER) has shown high selectivity and productivity for a broad range of CO2/COX ratio. Aiming to understand the behavior of the studied catalyst system under distinct operating conditions, we developed a new 9-parameter kinetic model. The parameters were estimated based on 815 steady-state experiments carried out at several values of pressure (30–54 bar), temperature (190–250 ℃), space-velocity (0.79–4.34 s−1) and inlet gas composition. This broad database was used in the development and validation of a new 9-parameter kinetic model for the direct DME synthesis. The model adequately simulates experiments in several process conditions, with 95% of the simulated points presenting a deviation lower than 20% with respect to the experimental results for outlet DME molar percentage. In addition, it correctly predicts the trends with respect to variations in H2 inlet fraction, which is of high relevance for processes using fluctuating renewable power sources for H2 production. In comparison to state-of-the-art models with more parameters, the new model is significantly more accurate. It benefits from the broad range of validity and elevated number of experimental points, which makes it a reliable model that can be applied for process optimization and scale-up.

A Formal Exchange Reaction between Ketones and Vinyl Ethers with Solid Catalysts

AbstractThe formal exchange of functional groups in internal positions of two different molecules is of interest in synthetic chemistry, as a simple retrosynthetic strategy. Here the formal exchange reaction between internal α-methylene ketones and vinyl ethers, retaining the original C–O bonds is presented. This process offers a new route for the synthesis of vinyl ethers in one step from ketones, including 1,3-diketones, under mild reaction conditions. Besides, the reaction is catalyzed by reusable cheap solids and can be carried out in flow for 20 days without signs of catalyst depletion. Combined experimental and computational mechanistic studies unveil the key role of carbonyl–enol equilibria.

Computational insights into the spontaneity of epoxide formation from halohydrins and other mechanistic details of Williamson’s ether synthesis

The reaction mechanism of several Williamson‟s ether syntheses have been studied using density functional theory with triple-ζ basis sets. These computations show that the synthesis of geometrically-strained epoxide from deprotonated halohydrins is due to the combined effects of favourable solvation of the products, higher bond enthalpy of C-O bonds vs. C-Cl bonds and increased vibrational entropy of the epoxide vs. the original halohydrin. Examination of the pathways leading to the formation of larger cyclic ethers revealed that the experimentally-observed preference for the formation of five-atom rings over six-atom-rings is due to the preference of the intervening methylene groups for staggered conformations, which entails that the alkyl carbon in the reactant state leading to the six-atom cyclic ether is initially not properly aligned with the attacking alkoxide. Study of the competing elimination reactions further shows that during the synthesis of five-atom cyclic ethers the competing elimination reaction is strongly disfavoured due to steric effects. The temperature dependence of both reactions favours elimination over SN2 as temperature rises, though only when the alkoxide and the halogen moieties are not part of the same carbon chain.

Total Syntheses of Rhodomollins A and B.

The first and asymmetric total syntheses of rhodomollins A and B, two rhodomollane type grayanoids featuring a d-homograyanane carbon skeleton and an oxa-bicyclo[3.2.1] core, were accomplished via a convergent strategy. A Stille coupling and a lithium-halogen exchange/intramolecular nucleophilic addition to the aldehyde sequence were employed to assemble two enantioenriched fragments. The oxa-bicyclo[3.2.1] core was achieved through an intramolecular SN2 substitution of cyclic sulfate of 1,2-diols (Williamson ether synthesis). The A ring oxidation states were adjusted by a Payne/Meinwald rearrangement sequence and subsequent redox transformations.

Synthesis of Alkyl Aryl Ethers by O-Arylation of Alcohols with Diaryliodonium Salts: Scope, Limitations, and Mechanism

AbstractWe describe the development of a C–O coupling reaction between aryl(2,4,6-trimethoxyphenyl)iodonium salts and aliphatic alcohols under weak base conditions. The scope of the reaction is presented, with 16 examples ranging in yield from moderate to high (54–96%). The limitations of the reaction are also presented. Mechanistic experiments reveal a complex network of reactions that include side reactions that generate arynes and oxidize the alcohol nucleophile.

Photoredox Synthesis of Silyl Ethers via Radical Coupling of Ketones with Hydrosilanes and [1, 2]‐Brook Rearrangement

AbstractAn expedient synthesis of silyl ethers is reported via photocatalytic free radical coupling of ketones with hydrosilanes and subsequent [1, 2]‐Brook rearrangement. This strategy features the advantages of 100 % atom economy, environmental friendliness, easily available starting materials as well as late‐stage functionalization of complex molecules.

Harnessing the Peterson Reaction for the Stereospecific Synthesis of Z-Vinyl Ethers.

Vinyl ethers are valuable synthetic intermediates which are also found as natural products, including aflatoxins, rifamycins and plasmalogens. The latter are ubiquitous phospholipids in human cells and contain a vinyl ether moiety with specifically Z configuration. Although numerous methods are available for synthesis of vinyl ethers, there is a lack of methods for obtaining Z isomers of molecules of the type RCH=CHOR' that are applicable to plasmalogens. A variant of the Peterson reaction is described that generates such molecules with very high stereoselectivity (Z/E ratio: 99 : 1). (R,R)/(S,S)-1-alkoxy-2-hydroxyalkylsilanes were synthesized from 1-trimethylsilylalkynes by a sequence of reduction with di-isobutylaluminium hydride to a (Z)-1-trimethylsilylalkene, epoxidation of the alkene to a 2-trimethylsilyl-3-substituted epoxide and regioselective, boron-trifluoride catalyzed ring-opening of the epoxide by reaction with an alcohol. Conversion of the (R,R)/(S,S)-1-alkoxy-2-hydroxyalkylsilanes to vinyl ethers (RCH=CHOR') was achieved under basic conditions as in a standard Peterson reaction. However, near exclusive formation of a Z vinyl ether was only achieved when the reaction was performed using potassium hydride in the non-polar solvent α,α,α-trifluorotoluene, more polar solvents giving increasing amounts of the E isomer. The sequence described embraces a variety of substituents and precursors, proceeds in overall high yield and is readily scalable.

Synthesis of Cardanil Methyl Ether via Etherification Reaction Cardanol Isolated from Cashew Nut Shells (Anacardium occidentale L.) with Variations of Molar Methyl Iodide

The synthesis of the Cardanyl methyl ether is carried out through an etherization reaction between Cardanyl seed skin extract (CNSL) isolated from the methyl iodide. Cardanol is isolated with the addition of acetone, Ca(OH)2, NH4OH 25%, n-hexane: ethyl acetate (98:2), washing with NaOH 2.5%, HCl 5%, aquadest, and Na2SO4 anhydrate. The yield of the obtained cardanol is 74.39 g (74.39% of the initial weight of the CNSL) and has the following characteristics: acid count 1.2863 mgKOH/g, iodine count 215.6535 g I2/100 g, viscosity 38.7 cP, density 0.8266 g/mL, pH = 6.14. The FT-IR methyl ether Cardanyl spectrum shows an absorption band at 1162.9-1259.8 cm-1 shows a C-O stretching group at a wave number of 1043.6-1148.0 cm-1 showing the formation of an asymmetric and symmetrical C- O-C stretching band of the ether compound, the Spectra of the FT - IR methyl ether Cardanyl shows an absorptive band at 1162-1259-125,8 cm-1, showing a C-O stretching Group, at the wave number of 1043.6-1148.0 cm-1 indicating the formation, as a result, of an Asymmetric and Symmetric Stretching Group of the ethereal Compound. The Cardanyl methyl ether was synthesized by adding K2CO3, the solvent acetone and the iodide-methyl, with a reflux time of 8 hours. As for the parameters carried out in this study, the molar variation of the Cardanyl is the Methyl Iodide (1:1.5, 1:3, and 1:4.5) and yields 3.555 g; 12.084 g; 11.472 g of Cardanyl ether. Methyl ether Cardanyl was obtained in analysis with FT-IR and GC-MS spectroscopic photometers. The results of the analysis of Cardanyl methyl ethers with GC -MS were 63.28%, and the results of analysis of the Cardanyl ether with a variation of the molar ratio Cardanyl: Methyl iodide (1:1.5; 1:3; 1:4.5) with GC-MS obtaining 3.05%, 30.29%, and 26.58%. These results show the maximum percentage of methyl ethers Cardanyl at the reaction conditions of the variation molar ratios Cardanyl iodides (1:3), K2CO3 17.3 g, 50 mL of acetone, and 8 hours of reflux time.

A novel power, DME, and ammonia polygeneration system using Aspen plus based on the integration of biomass gasification and syngas chemical looping

To solve the problems of fossil energy shortage and environmental pollution, a novel polygeneration system based on corn straw gasification was developed using Aspen Plus. The system consists of gasification, the supercritical CO2 cycle, syngas chemical looping, ammonia synthesis, methanol synthesis, and dimethyl ether (DME) synthesis subsystems. This system can simultaneously generate power, DME, and ammonia. Sensitivity, energy, and exergy analyses were conducted on the system. The results showed that the thermal and exergy efficiencies of the system are 60.15% and 46.70%, respectively. The system can recover the initial investment cost in 8 years, and within a 20-year life cycle, the net present value of this new solution can reach 1566.61 k$. The sustainability index (SI) value of the entire system is 1.88.

Synthesis of Methyl Glycerol Ethers over a Zeolite Catalyst in a Fixed-Bed Reactor

Synthesis of Methyl Glycerol Ethers over a Zeolite Catalyst in a Fixed-Bed Reactor

Transition-metal and base-free ether synthesis via alcohol-participated yne-allylic substitution

Ethers are among the most important chemicals in organic synthesis, the pharmaceutical industry, agrochemical production, and material science. C–O bond formation via substitution is one of the most widely used strategies for ether formation. However, known methods usually employ transition-metal and bases to facilitate the process. In this work, we describe the base- and transition-metal-free ether formation via alcohol and phenol-participated substitution. The protocol allows access to a large number of ethers with enyne functional moieties, and features mild reaction conditions, high efficiency, and good regio- and stereoselectivities. The reaction could be readily scaled up, and the products could be used in a range of further transformations.