Dialkyl Ethers Research Articles

Alkoxyhydrosilane-facilitated cross-etherification reaction of secondary benzyl alcohol with aliphatic alcohol: synthesis of unsymmetrical dialkyl ethers.

Alkoxyhydorosilane is found to be an effective mediator for the cross-etherification reaction between two distinct alcohols, namely, a secondary benzyl alcohol and an aliphatic alcohol, providing the unsymmetrical dialkyl ethers in good-to-high yields. The reaction is also successfully applied to the lignin model compound, which is an important renewable non-fossil organic carbon source. Initial mechanistic studies indicated that the carbocation derived from benzyl alcohol was formed under the present reaction conditions.

The Halogen Bond to Ethers - Prototypic Molecules and Experimental Electron Density.

Halogen bonds to dialkyl ether molecules have remained largely unexplored. We here address the synthesis and the structural chemistry of the first halogen-bonded noncyclic alkyl ethers, combining 1,4-diiodotetrafluorobenzene and the prototypic or commonly used ethers dimethyl ether, tetrahydrofuran, and methyl-tert-butyl ether as halogen acceptors. Two different structural motifs based on moderately strong halogen bonds were obtained: Discrete trimolecular aggregates are formed, and unexpected halogen-bonded supramolecular chain adducts feature oxygen-bifurcated halogen bonds with 1:1 donor:acceptor ratio. Both structure types may be selectively obtained even for the same ether by adjusting the stoichiometry in the crystallization experiments. The geometric features of the etheric oxygen center were found to be flexible, in contrast to the almost linear geometry about the halogen donor atom. A high-resolution X-ray diffraction experiment on the extended adduct of dimethyl ether allowed us to study the electronic details of the acceptor-bifurcated I···O···I halogen bonds. The electron density in the bond critical points and derived properties such as the Laplacian indicate essentially electrostatic interactions and explain the geometrical flexibility of ethers in halogen bonds. Our studies demonstrate the great versatility of ethers as halogen bond acceptors, that can occur in many geometrical arrangements and whose contribution to nature's structural designs should not be underestimated.

Synthesis of Sterically Hindered Dialkyl Ethers via Palladium-Catalyzed Fluoro-alkoxylation of gem-Difluoroalkenes.

Organofluorine compounds are of high value in medicinal and agricultural chemistry. Herein, we report a palladium-catalyzed fluoro-alkoxylation of gem-difluoroalkenes for the synthesis of much more challenging sterically hindered ethers. This reaction represents a direct synthesis method for α-trifluoromethyl ethers with a broad functional group tolerance and excellent regioselectivity. This system employs N-fluorobenzenesulfonimide (NFSI) as an electrophilic fluorine source and alcohols as nucleophilic donors, including but not limited to sterically hindered tert-substituted alcohols.

Mono- to tetra-alkyl ether cardiolipins in a mesophilic, sulfate-reducing bacterium identified by UHPLC-HRMSn: a novel class of membrane lipids.

The composition of membrane lipids varies in a number of ways as adjustment to growth conditions. Variations in head group composition and carbon skeleton and degree of unsaturation of glycerol-bound acyl or alkyl chains results in a high structural complexity of the lipidome of bacterial cells. We studied the lipidome of the mesophilic, sulfate-reducing bacterium, Desulfatibacillum alkenivorans strain PF2803T by ultra-high-pressure liquid chromatography coupled with high-resolution tandem mass spectrometry (UHPLC-HRMSn). This anaerobic bacterium has been previously shown to produce high amounts of mono-and di-alkyl glycerol ethers as core membrane lipids. Our analyses revealed that these core lipids occur with phosphatidylethanomamine (PE) and phosphatidylglycerol (PG) head groups, representing each approximately one third of the phospholipids. The third class was a novel group of phospholipids, i.e., cardiolipins (CDLs) containing one (monoether/triester) to four (tetraether) ether-linked saturated straight-chain or methyl-branched alkyl chains. Tetraether CDLs have been shown to occur in archaea (with isoprenoid alkyl chains) but have not been previously reported in the bacterial Domain. Structurally related CDLs with one or two alkyl/acyl chains missing, so-called monolyso-and dilyso-CDLs, were also observed. The potential biosynthetic pathway of these novel CDLs was investigated by examining the genome of D. alkenivorans. Three CDL synthases were identified; one catalyzes the condensation of two PGs, the other two are probably involved in the condensation of a PE with a PG. A heterologous gene expression experiment showed the in vivo production of dialkylglycerols upon anaerobic expression of the glycerol ester reductase enzyme of D. alkenivorans in E. coli. Reduction of the ester bonds probably occurs first at the sn-1 and subsequently at the sn-2 position after the formation of PEs and PGs.

Anatomical and Metabolome Features of Haloxylon aphyllum and Haloxylon persicum Elucidate the Resilience against Gall-Forming Insects.

Globally, gall-forming insects significantly contribute to the degradation of desert ecosystems. Recent studies have demonstrated that Haloxylon persicum suffers less damage from gall-formers compared to Haloxylon aphyllum. However, the mechanisms driving the long-term metabolic responses of these species to gall-forming biotic stress in their natural environment remain unclear. The current study comparatively analyzes the anatomical features and metabolomic changes in H. aphyllum and H. persicum damaged by gall-forming insects. This research aimed to uncover potential metabolic tolerance mechanisms through GC-MS analysis. The study findings indicate that gall-forming insects cause a reduction in nearly all the anatomical structures of Haloxylon shoots, with the effects being less severe in H. persicum than in H. aphyllum. Thus, the metabolic pathways responsible for the biosynthesis of biologically active substances that enhance resistance to gall inducers were different, specifically in H. aphyllum-the biosynthesis of fatty acids (+their derivatives) and γ-tocopherol (vitamin E) and H. persicum-the biosynthesis of fatty acids (+their derivatives), dialkyl ethers, carbohydrates (+their derivatives), aromatic acid derivatives, phytosterols, γ-tocopherol (vitamin E), phenols, and terpenoids. The results suggest that the modulation of metabolic pathways under biotic stress plays a crucial role in the enhanced survival and growth of H. persicum.

Hydrogen-Induced Formation of Surface Acid Sites on Pt/Al(PO3)3 Enables Remarkably Efficient Hydrogenolysis of C-O Bonds in Alcohols and Ethers.

The hydrogenolysis of oxygenates such as alcohols and ethers is central to the biomass valorization and also a valuable transformation in organic synthesis. However, a mild and efficient catalyst system for the hydrogenolysis of a large variety of alcohols and ethers with various functional groups is still underdeveloped. Here, we report an aluminum metaphosphate-supported Pt nanoparticles (Pt/Al(PO3)3) for the hydrogenolysis of a wide variety of primary, secondary, and tertiary alkyl and benzylic alcohols, and dialkyl, aryl alkyl, and diaryl ethers, including biomass-derived furanic compounds, under mild conditions (0.1-1 atm of H2, as low as 70 °C). Mechanistic studies suggested that H2 induces formation of the surface Brønsted acid sites via its cleavage by supported Pt nanoparticles. Accordingly, the high efficiency and the wide applicability of the catalyst system are attributed to the activation and cleavage of C-O bonds by the hydrogen-induced Brønsted acid sites with the assistance of Lewis acidic Al sites on the catalyst surface. The high efficiency of the catalyst implies its potential application in energy-efficient biomass valorization or fine chemical synthesis.

Hydrogen‐Induced Formation of Surface Acid Sites on Pt/Al(PO3)3 Enables Remarkably Efficient Hydrogenolysis of C−O Bonds in Alcohols and Ethers

AbstractThe hydrogenolysis of oxygenates such as alcohols and ethers is central to the biomass valorization and also a valuable transformation in organic synthesis. However, a mild and efficient catalyst system for the hydrogenolysis of a large variety of alcohols and ethers with various functional groups is still underdeveloped. Here, we report an aluminum metaphosphate‐supported Pt nanoparticles (Pt/Al(PO3)3) for the hydrogenolysis of a wide variety of primary, secondary, and tertiary alkyl and benzylic alcohols, and dialkyl, aryl alkyl, and diaryl ethers, including biomass‐derived furanic compounds, under mild conditions (0.1–1 atm of H2, as low as 70 °C). Mechanistic studies suggested that H2 induces formation of the surface Brønsted acid sites via its cleavage by supported Pt nanoparticles. Accordingly, the high efficiency and the wide applicability of the catalyst system are attributed to the activation and cleavage of C−O bonds by the hydrogen‐induced Brønsted acid sites with the assistance of Lewis acidic Al sites on the catalyst surface. The high efficiency of the catalyst implies its potential application in energy‐efficient biomass valorization or fine chemical synthesis.

Linear ether-based highly concentrated electrolytes for Li-sulfur batteries.

Li-S batteries have attracted attention as next-generation rechargeable batteries owing to their high theoretical capacity and cost-effectiveness. Sparingly solvating electrolytes hold promise because they suppress the dissolution and shuttling of polysulfide intermediates to increase the coulombic efficiency and extend the cycle life. This study investigated the solubility of polysulfide (Li2S8) in a range of liquid electrolytes, including organic electrolytes, highly concentrated electrolytes, and ionic liquids. The Li2S8 solubility was well correlated with the donor number (DNNMR), estimated via23Na-NMR, and was lower than 100 mM_(elemental sulfur) in electrolytes with DNNMR < 14, regardless of the type of electrolyte. Highly concentrated electrolytes comprising lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and linear chain dialkyl ethers such as methyl propyl ether (MPE), n-butyl methyl ether (BME), and ethyl propyl ether (EPE) were studied as sparingly solvating electrolytes for Li-S batteries. Monomethyl ethers, such as BME, showed more pronounced Li-ion coordination and higher ionic conductivity, whereas the steric hindrance of the longer alkyl chains in EPE lowered the solvation number, enhanced ion association, and lowered the ionic conductivity despite the solvents having similar dielectric constants. The charge-discharge rate capabilities of Li-S cells with dialkyl ether-based electrolytes were more impressive than those of cells with a localized high-concentration electrolyte using sulfolane (SL) and hydrofluoroether (HFE), [Li(SL)2][TFSA]-2HFE. The higher rate performance was attributed to the superior Li-ion transport properties of the dialkyl ether-based electrolytes. A pouch-type cell using lightweight [Li(BME)3][TFSA] demonstrated an energy density exceeding 300 W h kg-1 under lean electrolyte conditions.

Re-evaluation of solution enthalpies of aliphatic hydrocarbons functional derivatives and terpenes in n-heptane and their validation by thermochemical consistency

The aim of this study was to investigate the influence of the position of the functional group and the choice of solvent on the relationships between the enthalpies of solution and the alkyl chain length of aliphatic hydrocarbons functional derivatives. The results show that the selection of an appropriate solvent for functional derivatives, such as methanol for alcohols and acetonitrile for alkyl nitriles, is not a viable option because the enthalpies of solution increase non-linearly with increasing alkyl chain length, leading to significant errors in the prediction of enthalpies of solution.On the other hand, the enthalpies of solution of aliphatic hydrocarbons functional derivatives in n-heptane decrease non-linearly with increasing number of methylene fragments in the chain. In this work, complementary measurements of the enthalpies of solution of homologous series of dialkyl ethers, alkyl-amines and nitroalkanes in n-heptane were carried out. These new data were used to develop an approach to estimate the enthalpies of solution of dialkyl ethers, alkyl-nitriles and alkyl-amines in n-heptane. The absolute deviations between predicted and experimental solution enthalpies for most of the investigated compounds do not exceed 0.5 kJ mol−1. The proposed approach to predict the solution enthalpies of aliphatic hydrocarbon derivatives in n-heptane was applied to estimate the enthalpies of fusion of 11 aliphatic hydrocarbon derivatives, which agreed well with the values obtained by differential scanning calorimetry. Complementary vapour pressure measurements were carried out on cyclic aliphatic hydrocarbons from the terpene family using a transpiration method to derive their enthalpies of vaporisation. The latter were used for independent validation of the re-evaluated solution enthalpies.

Study on the possibility of synthesizing oxygenates based on light pyrolysis resin using a modified ion exchange resin

Dialkyl ethers present potential additives to motor fuels. The study considers the possibility of obtaining oxygenates from light pyrolysis resin. The interaction of 75–90 °C fraction from light pyrolysis resin (LPR), having high content of high molecular weight unsaturated hydrocarbons, compared to other lighter fractions of LPR with a significant content of saturated hydrocarbons, and ethanol at different reagent ratios in the presence of a catalyst, Purolite CT-151 ion-exchange resin (sulfonated copolymer of styrene and divinylbenzene) modified with Na+, K+, Cu2+, Ca2+, Co2+, Ni2+ ions, is analyzed. The iodine value is chosen as the key parameter reflecting the content of unsaturated structures. The greatest decrease in the iodine value is observed for the ion exchange resin modified with cobalt ions, which is further used as the etherification catalyst. At 75–90 °C fraction:ethanol ratio of 0.5:1.5 and 60 °C, the yield of oxygenates reached 4.9% by weight.

Catalytically Generated Meerwein's Salt-Type Oxonium Ions for Friedel-Crafts C(sp2)-H Methylation with Methanol.

A catalytic protocol for a Friedel-Crafts-type direct C(sp2)-H methylation of various arenes with methanol is disclosed. The reaction is initiated by counteranion-stabilized silylium or arenium ions, which form Meerwein's salt-like oxonium ions with methanol as the active methylating agents. The silylated methyloxonium ions are stronger electrophiles than their protonated congeners, allowing the Friedel-Crafts alkylation to proceed more efficiently and at a lower reaction temperature. The regeneration of these superelectrophiles within the catalytic cycle is accomplished by the addition of a tetraorganosilane additive, i.e., trimethyl(phenyl)silane or tetraethylsilane, that releases a silylium ion through protodesilylation by the Brønsted acidic Wheland intermediate, thereby acting as a productive "proton-into-silylium ion" generator. By this method, even the C-H methylation of electronically deactivated aryl halides with methanol is achieved. The protocol is also applicable to nonactivated primary as well as π-activated benzylic alcohols. Dialkyl ethers are also competent alkylating agents in the presence of the quaternary phenylsilane additive.

Photoredox-catalyzed C–C bond cleavage of cyclopropanes for the formation of C(sp3)–heteroatom bonds

Sterically congested C–O and C–N bonds are ubiquitous in natural products, pharmaceuticals, and bioactive compounds. However, the development of a general method for the efficient construction of those sterically demanding covalent bonds still remains a formidable challenge. Herein, a photoredox-driven ring-opening C(sp3)–heteroatom bond formation of arylcyclopropanes is presented, which enables the construction of structurally diversified while sterically congested dialkyl ether, alkyl ester, alcohol, amine, chloride/fluoride, azide and also thiocyanate derivatives. The selective single electron oxidation of aryl motif associated with the thermodynamic driving force from ring strain-release is the key for this transformation. By this synergistic activation mode, C–C bond cleavage of otherwise inert cyclopropane framework is successfully unlocked. Further mechanistic and computational studies disclose a complete stereoinversion upon nucleophilic attack, thus proving a concerted SN2-type ring-opening functionalization manifold, while the regioselectivity is subjected to an orbital control scenario.

Experiments and a generalized model of the chemical equilibrium of transacetalization and oligomerization of poly(oxymethylene) dialkyl ethers

Poly(oxymethylene) dialkyl ethers (OAE) are oxygenated oligomers that feature favorable physical properties like emission-reducing potential when used as fuels in combustion engines. This work presents a generalized model to describe the chemical equilibrium of water-free mixtures containing OAE, with various terminating alkyl groups and chain lengths, and 1,3,5-trioxane as anhydrous formaldehyde source. The entirely predictive model is based on a generalized equilibrium constant for the formaldehyde oligomerization and statistical considerations. Reaction experiments with various feed compositions are performed at different temperatures and samples are analyzed by NMR spectroscopy. OAE with chain lengths n⩽5 are quantified. The model performs very well when compared to the experimental results of the present work and is thus able to fully describe the chemical equilibrium in mixtures containing OAE and a formaldehyde source. The presented model serves as reliable base for further extensions regarding more complex alkyl groups and systems containing water and alcohols.

Intermolecular 1,2-Difunctionalization of Alkenes Enabled by Fluoroamide-Directed Remote Benzyl C(sp3)-H Functionalization.

A copper-catalyzed remote benzylic C-H functionalization strategy enabling 1,2-difunctionalization of alkenes with 2-methylbenzeneamides and nucleophiles, including alcohols, indoles, pyrroles, and the intrinsic amino groups, is reported, which is characterized by its redox-neutral conditions, exquisite site-selectivity, broad substrate scope, and wide utilizations of late-stage modifying bioactive molecules. This reaction proceeds through nitrogen-centered radical generation, hydrogen atom transfer, benzylic radical addition across the alkenes, single-electron oxidation, and carbocation electrophilic course cascades. While using external nucleophiles manipulates three-component alkene alkylalkoxylation and alkyl-heteroarylation with 2-methylbenzeneamides to access dialkyl ethers, 3-alkylindoles, and 3-alkylpyrroles, omitting the external nucleophiles results in two-component alkylamidation ([5+2] annulation) of alkenes with 2-methylbenzeneamides to benzo-[f][1,2]thiazepine 1,1-dioxides.

Depolymerization and Demethylation of Kraft Lignin in Molten Salt Hydrate and Applications as an Antioxidant and Metal Ion Scavenger.

To improve the reactivity and enrich the functionality of lignin for valorization, kraft lignin was depolymerized and demethylated via cleaving aryl and alkyl ether bonds in acidic lithium bromide trihydrate (∼60% LiBr aqueous solution). It was found that the cleavage of the ether bonds followed the order of β-O-4 ether > aryl alkyl ether in phenylcoumaran > dialkyl ether in resinol > methoxyl (MeO). The depolymerization via β-O-4 cleavage occurred under mild conditions (e.g., <0.5 M HCl at 110 °C), while sufficient demethylation of the lignin needed harsher conditions (>1.5 M HCl). Both depolymerization and demethylation generated new aromatic hydroxyl (ArOH). With 2.4 M HCl, MeO content dropped from 4.85 to 0.95 mmol/g lignin, and ArOH content increased from 2.78 to 5.09 mmol/g lignin. The depolymerized and demethylated kraft lignin showed excellent antioxidant activity and Cr(VI)-scavenging capacity, compared with original kraft lignin and tannins.

Mesoporous acidic functional N-containing ZrNxOy material for polyoxymethylene diethyl ethers synthesis under mild conditions

Polyoxymethylene dialkyl ethers, which can be blended into diesel fuels, have attracted increasing attentions due to their advantages for fuel additives. It can utilize bioethanol and biomass syngas, helping to achieve the carbon neutral target earlier. Polyoxymethylene diethyl ethers (PODEEn) synthesis requires efficient catalysts with high performance. In this work, the mesoporous acidic functional N-containing ZrNxOy catalysts were prepared with a Sol-Gel assisted solvothermal method. The acid nature and strength, morphology, crystalline structure and pore distribution of catalysts were characterized by fourier transform infrared (FT-IR) spectroscopy, pyridine-adsorption infrared spectra (Py-IR), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), N2 adsorption-desorption isotherm, X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of ammonia (NH3-TPD) etc, showing catalyst possessing crystalline-amorphous mixed domains with smaller defective tetragonal nanoparticles and mesopores. The catalysts were applied in PODEEn synthesis, showing excellent activity and selectivity under mild conditions. And the high trioxane (TOX) conversion of 93 % and excellent PODEE2−8 selectivity of 98 % can be achieved at 80 °C under atmospheric pressure owning to the superior properties.

Physical and Electrolytic Properties of Dialkoxyethanes

1,2-Dimethoxyethane (DME, ethylene glycol dimethyl ether) and 1,2-diethoxyethane (DEE, ethylene glycol diethyl ether) are dialkyl ethers of ethylene glycol. DME shows a high boiling point as compared to diethyl ether and tetrahydrofuran. DME is also used as a reagent in organometallic chemistry and as a solvent in some electrolyte solutions for lithium batteries. The solubility of lithium salts in DEE is much less than that in DME. Partial fluorination of DEE can improve the solubility of lithium salts. In contrast, the polyfluorinated and perfluorinated organic solvents show very low polarity. These solvents are the so-called fluorous media and are often immiscible with organic solvents as well as water. We report the physical and electrochemical properties of fluorinated DEEs: monofluorinated, trifluorinated, and tetrafluorinated DEEs (EFEE, ETFEE, and FETFEE, respectively).The relative permittivity reflects the ease of progress of dielectric polarization. The relative permittivities of FETFEE, EFEE, and EFTEE decreased linearly with an increase in temperature. The relative permittivities of FETFEE, EFEE, and EFTEE decreased linearly with an increase in temperature. The relative permittivity of FETFEE was higher than those of ETFEE and EFEE: FETFEE > ETFEE ≈ EFEE > DEE. The viscosity is the property which opposes the relative motion of the adjacent layers of the liquid. It is regarded as the internal friction and affects electrolytic conductivity. The viscosity (η) of FETFEE was also higher than those of EFEE and ETFEE: FETFEE > EFEE > ETFEE > DEE. The kinematic viscositsiy (v) of ETFEE was as low as that of DEE above 323 K. The plots of log10(η/mPas) vs. T −1 and the plots of log10(v / 10−2 m2 s−1) vs. T −1 gave straight lines.The conductivity of an electrolyte solution is a key factor determining the internal resistance and rate performance of lithium batteries. The conductivities (κ) of electrolyte solutions in ETFEE and FETFEE increased with an increase in temperature (T). The viscosities of the fluorinated DEEs decreased rapidly with an increase in temperature and approached that of DEE at high temperatures. Interestingly, the conductivity of LiPF6 solution in FETFEE was higher than that in ETFEE: EFEE > FETFEE > ETFEE. The partial fluorination can increase the ability of the solvent molecules to form hydrogen bonds. The number of hydrogen atoms that are bound to the same terminal carbon atom as fluorine atoms are as given below: FETFEE (2), EFEE (2), ETFEE (0), and DEE (0). The attraction between FETFEE molecules can be based on nonconventional weak intermolecular hydrogen bonding (CF−H···O or C−H···F−C). The weak hydrogen-bonding system does not exchange its proton and therefore it is no more a genuine hydrogen bond; it is an electrostatic attraction between positive charge on the hydrogen and negative charge on the organic fluorine or the organic oxygen.The hydrogen bonding leads to the high acceptability of an electron-pair of a donor atom from a solute. This effect may result in the increased solvation of PF6 − ions and, consequently, in the higher degree of ionic dissociation. The fluoromethyl group (CH2F-) may serve as an anion-attracting group. In contrast, the polyfluorination can decrease the electron-pair donability of an oxygen atom of the C-O-C moiety. The trifluoromethyl group (CF3-) is a strong electron-withdrawing substituent. The anodic stability of FETFEE was higher than that of EFEE: FETFEE > ETFEE > EFEE. The finding suggests that the electron-pair donability decreases in the inverse order: FETFEE < ETFEE < EFEE. Fluorine is the most electronegative of all the elements. Most conventional measures for the electronic effect of substituents are provided as Taft constants (σ*) for substituents attached to aliphatic chains. The Taft constants of a trifluorometheyl group (CF3-: Taft σ* = 2.61, σ(calcd.) = 2.60) and a fluorometheyl group (CH2F-: Taft σ* = 1.10, σ(calcd.) = 1.17) are substantially larger than that of a metheyl group (CH3-: Taft σ* = 0, σ(calcd.) = −0.07). The value of 1.10 is comparable with a formyl group (-CHO: Taft σ* = 1.1, σ(calcd.) = 1.09).The product of conductivity and viscosity (κη) observed for FETFEE, ETFEE, and EFEE was slightly decreasing at high temperatures. The plots of log10(η/mPas) vs. T −1 gave straight lines. In contrast, the plots of log10(κ/mScm−1) vs. T −1 displayed upward curvature. The decrease in the κη and the convex curve show that the conductivities of LiPF6 solutions in FETFEE, ETFEE, and EFEE are not inversely proportional to the viscosities at elevated temperatures.

Dialkyl Ether Formation at High-Valent Nickel.

In this article, we investigated the I2-promoted cyclic dialkyl ether formation from 6-membered oxanickelacycles originally reported by Hillhouse. A detailed mechanistic investigation based on spectroscopic and crystallographic analysis revealed that a putative reductive elimination to forge C(sp3)–OC(sp3) using I2 might not be operative. We isolated a paramagnetic bimetallic NiIII intermediate featuring a unique Ni2(OR)2 (OR = alkoxide) diamond-like core complemented by a μ-iodo bridge between the two Ni centers, which remains stable at low temperatures, thus permitting its characterization by NMR, EPR, X-ray, and HRMS. At higher temperatures (>−10 °C), such bimetallic intermediate thermally decomposes to afford large amounts of elimination products together with iodoalkanols. Observation of the latter suggests that a C(sp3)–I bond reductive elimination occurs preferentially to any other challenging C–O bond reductive elimination. Formation of cyclized THF rings is then believed to occur through cyclization of an alcohol/alkoxide to the recently forged C(sp3)–I bond. The results of this article indicate that the use of F+ oxidants permits the challenging C(sp3)–OC(sp3) bond formation at a high-valent nickel center to proceed in good yields while minimizing deleterious elimination reactions. Preliminary investigations suggest the involvement of a high-valent bimetallic NiIII intermediate which rapidly extrudes the C–O bond product at remarkably low temperatures. The new set of conditions permitted the elusive synthesis of diethyl ether through reductive elimination, a remarkable feature currently beyond the scope of Ni.

C(sp3)–H Bond Acylation with N-Acyl Imides under Photoredox/ Nickel Dual Catalysis

AbstractA novel Ni/photoredox-catalyzed acylation of aliphatic substrates, including simple alkanes and dialkyl ethers, has been developed. The method combines C–N bond activation of amides with a radical relay mechanism involving hydrogen-atom transfer. The protocol is operationally simple, employs bench-stable N-acyl imides as acyl-transfer reagents, and permits facile access to alkyl ketones under very mild conditions.

Specific Features of the Gas Chromatography–Mass Spectrometry Identification of Monoalkyl Phthalates

A similarity of electron ionization mass spectra of various alkyl esters of benzene-1,2-dicarboxylic (phthalic) acid places special demands on the reliability of the identification of monoalkyl phthalates, often recognized as dialkyl phthalates and vice versa. An original mass spectrometric criterion is proposed for the group identification of monoalkyl phthalates (assignment to a subgroup of homologues), which assumes the calculation of the total relative intensity of ion peaks at m/z > 170. In the mass spectra of monoalkyl esters, this value does not exceed 1%, whereas for dialkyl ethers, it varies from 1 to 172%. Within the set subgroups of isomers, it becomes effective to use the homologous increments of the retention indices, iRI = RI – 100x, where x = int (M/14), to refine the identification results. Using predefined iRI values and the ratio М ≈ 0.14(RI – iRI) + y, we can estimate the molecular weights of compounds in the mass spectra of which the molecular ion signals are not detected or are of low intensity (including monoalkyl phthalates). In addition, iRI values are in many cases informative for estimating the number of branches of the sp3 carbon skeleton of molecules (Z) based on regression relations of the form of iRI = aZ + b. The examination of homologous increments of the retention indices of dialkyl phthalates revealed an anomalous dependence of their values on the number of carbon atoms in the alkyl fragments of the molecules: from +125 (СН3) to –33 (С10Н21). In the subgroup of monoalkyl phthalates, such anomalies were not observed.