Cyclic Ethers Research Articles

4]Rhombene: Solution-Phase Synthesis and Application in Distributed Feedback Lasers With Emission Beyond 830 nm.

Graphene-like molecules with multiple zigzag edges are emerging as promising gain materials for organic lasers. Their emission wavelengths can vary widely, ranging from visible to near-infrared (NIR), as the molecular size increases. Specifically, rhombus-shaped molecular graphenes with two pairs of parallel zigzag edges, known as [n]rhombenes, are excellent candidates for NIR lasers due to their small energy gaps. However, synthesizing large-size rhombenes with emission beyond 800 nm in solution remains a significant challenge. In this study, we present a straightforward synthesis of an aryl-substituted [4]rhombene derivative, [4]RB-Ar, using a method that combines intramolecular radical-radical coupling with Bi(OTf)3-mediated cyclization of vinyl ethers. The structure of [4]RB-Ar was confirmed through X-ray crystallographic analysis. Bond length analysis and theoretical calculations indicate that aromatic sextets are predominantly localized along the molecule's long axis. Significantly, [4]RB-Ar demonstrates narrow amplified spontaneous emission at around 834 nm when dispersed in polystyrene thin films. Moreover, solution-processed distributed feedback lasers employing [4]RB-Ar as the active gain material display tunable narrow emissions in the range of 830 to 844 nm.

Ready Access to [5,6,5]-Trioxa-spiro and Fused Ketals via Ag-Catalyzed Cascade Annulation of 4-Pentyn-1-ols and Aldehydes.

In this study, we unveil the versatility of 4-pentyn-1-ols as carbonyl surrogates for the unprecedented synthesis of diverse oxygen heterocycles, including [5,6,5]-bis-spiroketals (trioxadispiroketals) and [5,6,5]-furano-spiroketals related to bioactive natural products. These reactions commence with the π-activation-induced intramolecular hydroalkoxylation of 4-pentyn-1-ols, yielding cyclic enol ethers, which undergo subsequent three-component annulation with aldehydes in a [2+2+1+1] fashion, resulting in the formation of [5,6,5]-bis-spiroketals. Notably, the distinctive steric features of alkynyl alcohols, particularly those with a secondary or tertiary alcohol functionality, dictate divergent reaction pathways, leading to the formation of [5,6,5]-furano-spiroketals.

Unveiling the electron-induced ionization cross sections and fragmentation mechanisms of 3,4-dihydro-2H-pyran.

The interactions of electrons with molecular systems under various conditions are essential to interdisciplinary research fields extending over the fundamental and applied sciences. In particular, investigating electron-induced ionization and dissociation of molecules may shed light on the radiation damage to living cells, the physicochemical processes in interstellar environments, and reaction mechanisms occurring in combustion or plasma. We have, therefore, studied electron-induced ionization and dissociation of the gas phase 3,4-dihydro-2H-pyran (DHP), a cyclic ether appearing to be a viable moiety for developing efficient clinical pharmacokinetics and revealing the mechanisms of biofuel combustion. The mass spectra in the m/z = 10-90 mass range were measured at several different energies of the ionizing electron beam using mass spectrometry. The mass spectra of DHP at the same energies were simulated using on-the-fly semi-classical molecular dynamics (MD) within the framework of the QCxMS formalism. The MD settings were suitably adjusted until a good agreement with the experimental mass spectra intensities was achieved, thus enabling a reliable assignment of cations and unraveling the plausible fragmentation channels. Based on the measurement of the absolute total ionization cross section of DHP (18.1 ± 0.9) × 10-16cm2 at 100eV energy, the absolute total and partial ionization cross sections of DHP were determined in the 5-140eV electron energy. Moreover, a machine learning algorithm that was trained with measured cross sections from 25 different molecules was used to predict the total ionization cross section for DHP. Comparison of the machine learning simulation with the measured data showed acceptable agreement, similar to that achieved in past predictions of the algorithm.

Gem-Difluoroalkylation of Cyclic Ethers Enabled by Cobalt-Catalyzed C(sp3)-H Oxidation under Mild Conditions.

Fluorinated rings have emerged as privileged structural modules in the fields of drug discovery and materials research. The incorporation of fluorine atoms into aromatic rings or heterocycles can lead to significant improvements in the physicochemical and biological properties of small molecules, making them valuable components in the design of new drugs and functional materials. Herein, we presented a cobalt-catalyzed C-H oxidation/gem-difluorination cascade reaction of readily available cyclic ethers with difluoroenoxysilanes, affording a series of gem-difluorinated analogues with moderate to high yields. The obtained products as versatile fluoroalkyl building blocks were showcased through divergent-oriented transformations.

Cyclic Ether-Based Electrolyte with a Weak Solvation Structure for Advanced Potassium Metal Batteries.

Potassium metal batteries (PMBs) are promising candidates for large-scale energy storage. Conventional carbonate electrolytes exhibit unsatisfactory thermodynamic stability against potassium (K) metal anode. Linear ether is widely adopted because of its compatibility with K metal, but the poor oxidation stability restricts the application with high-voltage cathodes. Herein, a weakly solvating cyclic ether is proposed as a solvent to stabilize the K-electrolyte interface and build a robust solid-electrolyte interphase (SEI). This weakly solvating electrolyte (WSE) possesses an anion-dominated solvation structure, which facilitates the anion decomposition for constructing an inorganic-rich SEI. The superior mechanical properties of the SEI, as examined by atomic force microscopy, prevent the SEI from fracture. Consequently, this WSE achieves highly reversible plating/stripping behavior of K metal for 1300h with a high average Coulombic efficiency of 99.20%. Stable full cells are also demonstrated with a high-voltage cathode at harsh conditions. This work complements the design of WSEs for advanced PMBs by cyclic ether solvents.

Research pro gress on historical processing evolution, chemical constituents,and pharmacological effects of Plantaginis Semen

Plantaginis Semen is a traditional Chinese medicine(TCM) commonly used in clinical practice in China, which has the effects of clearing heat, inducing diuresis for treating stranguria, draining dampness and relieving diarrhea, brightening eyes, and eliminating phlegm. Plantaginis Semen has a long history of processing. In the Han Dynasty, there were records of stir-frying, and then processing with wine, processing with salt water, processing with rice water, and other processing methods appeared. Plantaginis Semen after processing can weaken the cold nature of the drug, suitable for clinical application. Modern research has shown that the main chemical constituents of Plantaginis Semen are phenylethanol glycosides, cyclic enol ether terpenes, polysaccharides, and flavonoids, with diuretic, anti-inflammatory, hypoglycemic, hypolipidemic, antioxidant, and other pharmacological effects. This article reviewed the materia medica, medicine books, and related literature in various dynasties and analyzed the historical processing evolution, chemical constituents, and pharmacological effects of Plantaginis Semen, so as to provide a reference for the relevant research on Plantaginis Semen.

Bespoke Dual‐Layered Interface Enabled by Cyclic Ether in Localized High‐Concentration Electrolytes for Lithium Metal Batteries

Bespoke Dual‐Layered Interface Enabled by Cyclic Ether in Localized High‐Concentration Electrolytes for Lithium Metal Batteries

Rhodium-Catalyzed Enantioselective Intramolecular Hydroalkoxylation of Allenes and Application in the Total Synthesis of (R,R,R)-α-Tocopherol.

We report herein of a novel, enantioselective and rhodium- catalyzed cyclisation of allenyl alcohols towards chiral α-vinylic, cyclic ethers employing a rhodium/(R,R)-Me-ferrocelane catalyst. The corresponding chiral cyclic products were obtained in general high yields and enantioselectivities. The synthetic value of our obtained products was further exemplified by transformations of the allylic ether function. Furthermore, applying our newly developed method in our previously reported route towards the total synthesis of (R,R,R)-α-tocopherol, we accomplished a significantly improved 2nd generation synthesis of the chromane building providing a total number of 13 steps and an overall total yield of 27 %.

Structure-Activity Relationship of Benzophenazine Derivatives for Homogeneous and Heterogenized Photooxygenation Catalysis.

Singlet oxygen is a powerful oxidant used in various applications, such as organic synthesis, medicine, and environmental remediation. Organic and inorganic photosensitizers are commonly used to generate this reactive species through energy transfer with the triplet ground state of oxygen. We describe here a series of novel benzophenazine derivatives as a promising class of photosensitizers for singlet oxygen photosensitization. In this study, we investigated the structure-activity relationship of these benzophenazine derivatives. Akin to a molecular compass, the southern fragment was first functionalized with either aromatic tertiary amines, alkyl tertiary amines, aromatic sulfur groups, alkyl sulfur groups, or cyclic ethers. Enhanced photophysical properties (in terms of triplet excited-state lifetime, absorption wavelength, triplet state energy, and O2 quenching capabilities) were obtained with cyclic ether and sulfur groups. Conversely, the presence of an amine moiety was detrimental to the photocatalysts. The western and northern fragments were also investigated and slightly undesirable to negligible changes in photophysical properties were observed. The most promising candidate was then immobilized on silica nanoparticles and its photoactivity was evaluated in the citronellol photooxidation reaction. A high NMR yield of 97 % in desired product was obtained, with only a slight decrease over several recycling runs (85 % in the fourth run). These results provide insights into the design of efficient photosensitizers for singlet oxygen generation and the development of heterogeneous systems.

Iron-Catalyzed Multicomponent C-H Alkylation of in Situ Generated Imines via Photoinduced Ligand-to-Metal Charge Transfer.

Herein, we describe a novel photoinduced iron-catalyzed strategy for multicomponent C-H alkylation of in situ generated imines. By utilizing the alkyl radicals generated through iron-mediated photocatalytic C-H activation, the imines formed in situ are further subjected to addition reactions, resulting in the synthesis of various secondary and tertiary amine products. This method is simple to operate and does not require additional oxidants. It is applicable to inert alkane substrates such as cyclic alkanes, cyclic ethers, toluene, and ketones. The reaction is also compatible with various aromatic amines, alkyl amines, halogenated aromatic amines, as well as aromatic aldehydes, alkyl aldehydes, and cinnamaldehyde, among other different types of aldehydes.

Lewis Acid-Initiated Ring-Opening Reactions of Five- and Six-Membered Cyclic Ethers Based on the Oxonium Ylide Intermediates

Lewis Acid-Initiated Ring-Opening Reactions of Five- and Six-Membered Cyclic Ethers Based on the Oxonium Ylide Intermediates

Inorganic–organic polymer networks derived from a cyclic siloxane tetrafunctional glycidyl ether resin

AbstractA tetrafunctional glycidyl ether cyclic siloxane epoxy resin (TGTS) has been synthesized, characterized and cured with four aromatic amine hardeners: 1,3‐phenylenediamine (PDA), diethyltoluenediamine (DETDA), 4,4‐diaminodiphenylmethane (DDM) and 1,3‐bis(4‐aminophenoxy)benzene (APB). Each of the cured networks produces transparent and homogeneous networks, although when TGTS is cured with DETDA, reduced compatibility led to lower epoxide consumption, a more heterogenous microstructure and deleterious effects upon properties. Reduced miscibility of DETDA significantly impacts the chemical structure and microstructure of the network, resulting in significant reductions in thermal and mechanical properties but higher UV‐A transmission. The PDA‐, APB‐ and DDM‐cured networks conversely were more miscible and display properties typical of organic–inorganic hybrid networks, such as good mechanical properties at ambient and sub‐ambient temperatures, comparatively high glass transition temperatures, improved resistance to oxidation and lower UV‐A transmission. © 2024 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Acidity of saturated (hetero)cyclic α-fluoro carboxylic acids and lipophilicity of their amide derivatives

Analysis of the physicochemical parameters of saturated (hetero)cyclic carboxylic acids and their α-fluorinated analogues is described. Measured pKa values revealed a significant influence of the single fluorine substituent on the compound's acidity (pKa decreased by 1.3–2.4 units). This effect did not demonstrate additivity with electronic effects of other heteroatom (i.e., cyclic ether moiety). On the contrary, lipophilicity (LogP) of the corresponding anilides was almost unaffected upon α-substitution with a fluorine atom and mainly governed by the nature of the (hetera)cycloalkyl substituent. The obtained results suggest that polarization of the C–F bonds themselves does not define the fluorine effect on the compound's lipophilicity.

Changes in Rehmanniae Radix processing and their impact on ovarian hypofunction: potential mechanisms of action.

This study evaluates the research developments concerning Rehmanniae Radix in ovarian hypofunction diseases. It explores the processing methods of Rehmanniae Radix, the variations in its compounds before and after processing, the mechanism of Rehmanniae Radix and its active compounds in improving ovarian function, and the advancements in clinical applications of traditional Chinese medicine (TCM) compound that include Rehmanniae Radix. Comprehensive literature search was conducted using databases such as China National Knowledge Infrastructure (CNKI), China Science and Technology Journal Database, National Science and Technology Library, the Pharmacopoeia of the People's Republic of China, Pubmed, and the Web of Science Database. The search utilized the following Medical Subject Headings (MeSH) and keywords: "Rehmanniae Radix," "Drying Rehmannia Root," "Rehmannia glutinosa," "Rehmanniae Radix Praeparata," "Traditional Chinese Medicine Processing," "Pharmacological Effects," "Ovarian Aging," "Diminished ovarian reserve," "Premature ovarian insufficiency," "Premature Ovarian Failure," "Ovarian hypofunction diseases". The ancient Chinese medical books document various processing techniques for Rehmanniae Radix. Contemporary research has identified changes in its compounds processing and the resultant diverse therapeutic effects. When processed into Rehmanniae Radix Praeparata, it is noted for its ability to invigorate the kidney. TCM compound containing Rehmanniae Radix is frequently used to treat ovarian hypofunction diseases, demonstrating significant clinical effectiveness. The key changes in its compounds processing include cyclic dilute ether terpene glycosides, phenylethanol glycosides, sugars, and 5-hydroxymethylfurfural. Its pharmacological action is primarily linked to the improvement of granulosa cell proliferation, antioxidative and anti-aging properties, and modulation of the immune and inflammatory microenvironment. Furthermore, Rehmanniae Radix also offers therapeutic benefits for cardiovascular and cerebrovascular diseases, osteoporosis and cognitive dysfunction caused by low estrogen levels. Thereby Rehmanniae Radix mitigates both the short-term and long-term health risks associated with ovarian hypofunction diseases. Processed Rehmanniae Radix has shown potential to improve ovarian function, and its compound prescriptions have a definite effect on ovarian dysfunction diseases. Therefore Rehmanniae Radix was garnering interest for both basic and clinical research, with promising application prospects as a future therapeutic agent for ovarian hypofunction diseases. However, further studies on its toxicology and the design of standardized clinical trials are necessary to fully establish its efficacy and safety.

Feasibility of fractional distillation of Eucalyptus hybrida essential oil for the separation of valuable compounds

Raw essential oil (EO) of Eucalyptus hybrida extracted from the leaves of trees found in Uttarakhand state and nearby areas consists of a mixture of monoterpenoids, sesquiterpenoids and several different volatile compounds of which 1,8-cineole i.e., eucalyptol, a monoterpenoid cyclic ether is a major component. The eucalyptol rich EO also holds antimicrobial, anti-inflammatory, broncholytic and mucolytic potential. In this work experimental tests were done to evaluate the feasibility of batch fractionation or fractional distillation (FD) technique in performing value addition of eucalyptus essential oil. The proximity of boiling points of eucalyptol, limonene and p-cymene act as a barrier in separating these compounds. A two-stage FD procedure was devised, which recovers relatively light terpene fractions in first stage and provides eucalyptol rich fractions in second stage. The GC-MS analysis of the fractionated samples revealed good separation results with three stage-B fractions (B8, B9 and B10) containing >90% purity of eucalyptol, while two stage-A fractions (A1 and A2) containing >90% purity of pinene mixture (α-pinene and β-pinene). FD thus proved to be an effective method for adding value to the eucalyptus EO.

The influence of molecular structure on the oxidation reactivity of long-chain ethers: Experimental observation and theoretical analysis

Long-chain ethers have been proposed as promising biofuels for advanced combustion methods, yet their low-temperature oxidation (LTO) characteristics remain poorly understood. In this study, the LTO reactivities of n-heptane and five long-chain ethers with different structures, including dibutyl ether (DBE), diethylene glycol dimethyl ether (DGM), polyoxymethylene dimethyl ethers (PODE), 1,2-dimethoxyethane (1,2-DME), and dipropyleneglycol dimethyl ether (DPGDE) are investigated using a cooperative fuel research (CFR) engine, which is closer to the actual internal combustion engine operating environment. Products formed from LTO of ethers and n-heptane are investigated over a wide range of compress ratios (CRs), and their relationship to the global oxidation reactivity is suggested based on the quantum chemistry calculation. The presence of oxygen atoms in long-chain ethers significantly enhances oxidation reactivity, with the global oxidation reactivity ranking as follows: DGM > DPGDE > 1,2-DME > DBE > PODE > n-heptane. The key intermediate species generated during the LTO of n-heptane include aldehydes, ketones, and cyclic ethers, while oxygen atoms in ethers facilitate the formation of acids. The species pathway analysis and quantum chemistry calculations reveal that (1,5) and (1,6) H-transfers of alkylperoxy radical (ROȮ) are critical chain-propagation channels, playing pivotal roles in the LTO process. The impact of oxygen on oxidation reactivity can be attributed to two primary factors: accelerating the H-abstraction of ȮH and H-transfer of ROȮ by weakening the neighboring C-H bonds, and enhancing the branching ratio of H-transfer of ROȮ. The arrangement of two oxygen atoms between every two carbon atoms (–OCH2CH2O–) is optimal for oxidation reactivity, while the arrangement of oxygen and carbon (–OCH2OCH2–) weakens the oxidation activity due to fewer available hydrogens for H-transfer. The methyl group in branching-chain, exhibit reduced oxidation reactivity due to the strength of C-H bonds. Additionally, for ethers with the same structure, a longer carbon chain allows for more available hydrogens, resulting in stronger oxidation reactivity.

Pd‐Catalyzed [3+6+3+6] Macrocyclizations of Aryl α‐Diazo‐β‐Ketoesters

AbstractThanks to Pd(II)‐catalysis, an efficient synthesis of unsaturated macrocycles is achieved by [3+6+3+6] condensation of cyclic ethers with aryl α‐diazo‐β‐ketoesters. The presence of the electron‐rich aryl ester moieties forbids the use of dirhodium complexes as these diazo decomposition catalysts provoke unforeseen intermolecular Csp2−H insertion reactions that derail the targeted reactivity. However, with Pd(acac)2, using high concentration conditions (1 M), a variety of 18‐membered macrocycles (16 examples) is afforded with both aryl and alkyl diazo reagents. Catalyst selection for either electrophilic aromatic substitution (Rh) or ylide (Pd) pathways are explained by computational approaches.

Visible Light-promoted C(sp3)-H α-Carbamoylation of Cyclic Ethers with Isocyanides.

A protocol exploiting isocyanides as carbamoylating agents for the α-C(sp3)-H functionalization of cyclic ethers has been optimized via a combined visible light-driven hydrogen atom transfer/Lewis acid-catalyzed approach. The isocyanide substrate scope revealed an exquisite functional group compatibility (18 examples, with yields up to 99 %). Both radical and polar trapping, kinetic isotopic effect and real-time NMR studies support the mechanistic hypothesis and provide insightful details for the design of new chemical processes involving the generation of oxocarbenium ions.

Excess Thermodynamic Properties of Binary Liquid System Containing (Cyclic Ether + Octan-1-Ol) At Different Temperature

The ultrasonic velocity (u), density (ρ), and viscosity ( ) for the binary mixture 1,4-Dioxane (1) + Octan-1-ol (2) were measured over the whole composition range at temperature T = (298.15, 303.15 and 305.15) K. The experimental data have been used to calculate excess molar volume (VE), excess adiabatic compressibility ( ), excess viscosity ( ), excess intermolecular free length ( and excess internal pressure (PiE) over the entire composition range. These results have been fitted to the Redlich-Kister polynomial equation. Excess molar volume (VE), excess adiabatic compressibility ( ), excess viscosity ( ), excess intermolecular free length ( and excess internal pressure (PiE) were found to be negative for all temperatures. The results obtained have been discussed and interpreted in terms of the type and nature of the specific intermolecular interactions between the components.

Extraction and Physicochemical Characterization of Pectin from Noni (Morinda citrifolia) Fruit

Noni (Morinda citrifolia) is a popular plant in Asian countries and has great potential as pectin source for thickening agents in food products. In general, ethanol has been widely used to precipitate pectin, but the proportion can affect the quality of the product. Therefore, this study aimed to characterize the physicochemical properties of pectin from noni fruit. Extraction was performed using 0.1 N HCl at pH 1.5 and heated at 80°C for 15 min, followed by precipitation with different proportions of 96% ethanol including A (1:1), B (1:2), and C (1:3) v/v, while commercial orange pectin was used as a reference. The results showed that all pectin extracted belonged to the high methoxyl category. The FTIR spectra confirmed the presence of important functional groups including OH-hydroxyl, CH3-saturated aliphatic methyl, C=O carbonyl, and -O- cyclic ether. Furthermore, the crystalline and amorphous structures of noni pectin were confirmed by X-ray diffraction observation. The highest yield was achieved using the proportion of 1:3, followed by 1:2, and 1:1 on a wet basis. The MeO and AUA content of sample B (1:2) were relatively similar to those of the reference. Based on extraction results, noni possesses good characteristics and has the potential for commercial pectin production.