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An 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. [ABSTRACT FROM AUTHOR]

Axially chiral diaryl ethers are a type of unique atropisomers bearing two potential axes, which have potential applications in a variety of research fields. However, the catalytic enantioselective synthesis of these diaryl ether atropisomers is largely underexplored when compared to the catalytic asymmetric synthesis of biaryl or other types of atropisomers. Herein, we report a highly efficient catalytic asymmetric synthesis of diaryl ether atropisomers through an organocatalyzed enantioselective desymmetrization protocol. The chiral phosphoric acid‐catalyzed asymmetric electrophilic aromatic aminations of the symmetrical 1,3‐benzenediamine type substrates afforded a series of diaryl ether atropisomers in excellent yields and enantioselectivities. The facile construction of heterocycles by the utilizations of the 1,2‐benzenediamine moiety in the products provided access to a variety of structurally diverse and novel azaarene‐containing diaryl ether atropisomers. [ABSTRACT FROM AUTHOR]

Axially chiral diaryl ethers are a type of unique atropisomers bearing two potential axes, which have potential applications in a variety of research fields. However, the catalytic enantioselective synthesis of these diaryl ether atropisomers is largely underexplored when compared to the catalytic asymmetric synthesis of biaryl or other types of atropisomers. Herein, we report a highly efficient catalytic asymmetric synthesis of diaryl ether atropisomers through an organocatalyzed enantioselective desymmetrization protocol. The chiral phosphoric acid‐catalyzed asymmetric electrophilic aromatic aminations of the symmetrical 1,3‐benzenediamine type substrates afforded a series of diaryl ether atropisomers in excellent yields and enantioselectivities. The facile construction of heterocycles by the utilizations of the 1,2‐benzenediamine moiety in the products provided access to a variety of structurally diverse and novel azaarene‐containing diaryl ether atropisomers. [ABSTRACT FROM AUTHOR]

Herein, we report the first example of diazotization of aminopyridines and aminoquinolines with t-BuONO in hexafluoropropan-2-ol in the absence of acids or other initiators. For aminopyridines, this reaction is the first general route toward 2-, 3-, and 4-[(1,1,1,3,3,3-hexafluoropropan-2-yl)oxy]pyridines. [ABSTRACT FROM AUTHOR]

• Nucleophilic aromatic substitution (SNAr) of pentafluoropyridine with aliphatic alcohols and phenols afforded a series of six 4-substituted 2,3,5,6-tetrafluoropyridine (TFP) hetero ethers. • 4-substituted TFP hetero ethers served as intermediates for the preparation of terepyridine scaffolds 3,5-difluoro-2,6-bis(pyrazolyl)pyridine and 4-(hexyloxy)−2,3,5,6-tetra(1H -pyrazol-1-yl)pyridine. • The highly organic soluble, low vapor pressure TFP hetero ethers should garner interest for weakly binding to heterogeneous surfaces and influence bulk properties by nature of the aliphatic/aromatic substitution. • 3,5-Difluoro-2,6-bis(pyrazolyl)pyridine and 4-(hexyloxy)−2,3,5,6-tetra(1H -pyrazol-1-yl)pyridine compounds could serve as strong metal binding as ligands or scaffolds within larger macromolecular systems. A series of six, 4-substituted 2,3,5,6-tetrafluoropyridine (TFP) hetero ethers have been synthesized via regio-selective, nucleophilic aromatic substitution (SNAr) of pentafluoropyridine with aliphatic alcohols and phenols. Furthermore, the hexyloxy modified TFP substrate also served as a synthetic intermediate for the preparation of 3,5-difluoro-4-(hexyloxy)-2,6-di(1H -imidazol-1-yl)pyridine, as well as 4-(hexyloxy)-2,3,5,6-tetra(1H -pyrazol-1-yl)pyridine, which offers a terpyridine scaffold. This work outlines their synthetic methodology in addition to detailing the TFP intermediates' unexpected reactivity with imidazole and pyrazole nucleophiles [Display omitted] [ABSTRACT FROM AUTHOR]

Acyclic α-tertiary ethers represent a highly prevalent functionality, common to high-value bioactive molecules, such as pharmaceuticals and natural products, and feature as crucial synthetic handles in their construction. As such their synthesis has become an ever-more important goal in synthetic chemistry as the drawbacks of traditional strong base- and acid-mediated etherifications have become more limiting. In recent years, the generation of highly reactive intermediates via redox approaches has facilitated the synthesis of highly sterically-encumbered ethers and accordingly these strategies have been widely applied in α-tertiary ether synthesis. This review summarises and appraises the state-of-the-art in the application of redox strategies enabling acyclic α-tertiary ether synthesis. [ABSTRACT FROM AUTHOR]

Lactol carbocyclisations provide a succinct method of constructing the oxabicyclo[3.2.1]octane scaffold, a motif present in various natural products of medicinal interest. Lactols containing an unsaturated ketone or ester were prepared by olefin cross-metathesis; an electrophilic alkene derived from methyl vinyl ketone underwent concomitant terminal α-methylenation and oxa-Michael addition to give a bridged lactol which then underwent oxygen-to-carbon transposition in the presence of titanium (IV) chloride giving the desired unsaturated carbocyclic seven-membered bridged ether via a novel dehydrative cascade considered to involve titanium enolates. [ABSTRACT FROM AUTHOR]

A one-pot method for the synthesis of aromatic ethers using hypervalent iodine(III) reagents obtained from the corresponding iodoaryl compounds is developed. In this concise method, six diaryl ethers and three heterocyclic aromatic ethers are synthesized in good yields. Furthermore, possible mechanisms for the syntheses of the hypervalent iodine reagents and construction of the aromatic ethers are proposed. [ABSTRACT FROM AUTHOR]

An unprecedented AgI‐catalyzed efficient method for the coupling of imino ethers and enol diazoacetates through a [3+2]‐cycloaddition/C−O bond cleavage/[1,5]‐proton transfer cascade process is reported. The general class of imino ethers that includes oxazolines, benzoxazoles and benzimidates are applicable substrates for these reactions that provide direct access to fully substituted pyrroles with uniformly high chemo‐ and regioselectivity. High variability in substitution at the pyrrole 2‐, 5‐ and N‐positions characterizes this methodology that also presents an entry point for further pyrrole diversification via facile modification of resulting N‐functional pyrroles. [ABSTRACT FROM AUTHOR]

An unprecedented AgI‐catalyzed efficient method for the coupling of imino ethers and enol diazoacetates through a [3+2]‐cycloaddition/C−O bond cleavage/[1,5]‐proton transfer cascade process is reported. The general class of imino ethers that includes oxazolines, benzoxazoles and benzimidates are applicable substrates for these reactions that provide direct access to fully substituted pyrroles with uniformly high chemo‐ and regioselectivity. High variability in substitution at the pyrrole 2‐, 5‐ and N‐positions characterizes this methodology that also presents an entry point for further pyrrole diversification via facile modification of resulting N‐functional pyrroles. [ABSTRACT FROM AUTHOR]

Multicomponent reactions provide efficient means to access molecular complexity. Herein, we report a copper‐catalyzed three‐component reaction of diazo compounds, alcohols and ethynyl benziodoxole (EBX) reagents for the synthesis of propargyl ethers. Extensive variations of the three partners of the reaction is possible, leading to highly functionalized and structurally diverse products under mild conditions. Alkynylation of a copper ylide intermediate is postulated as key step for this transformation. [ABSTRACT FROM AUTHOR]

We report a catalytic, light‐driven method for the intramolecular hydroetherification of unactivated alkenols to furnish cyclic ether products. These reactions occur under visible‐light irradiation in the presence of an IrIII‐based photoredox catalyst, a Brønsted base catalyst, and a hydrogen‐atom transfer (HAT) co‐catalyst. Reactive alkoxy radicals are proposed as key intermediates, generated by direct homolytic activation of alcohol O−H bonds through a proton‐coupled electron‐transfer mechanism. This method exhibits a broad substrate scope and high functional‐group tolerance, and it accommodates a diverse range of alkene substitution patterns. Results demonstrating the extension of this catalytic system to carboetherification reactions are also presented. [ABSTRACT FROM AUTHOR]

We report a catalytic, light‐driven method for the intramolecular hydroetherification of unactivated alkenols to furnish cyclic ether products. These reactions occur under visible‐light irradiation in the presence of an IrIII‐based photoredox catalyst, a Brønsted base catalyst, and a hydrogen‐atom transfer (HAT) co‐catalyst. Reactive alkoxy radicals are proposed as key intermediates, generated by direct homolytic activation of alcohol O−H bonds through a proton‐coupled electron‐transfer mechanism. This method exhibits a broad substrate scope and high functional‐group tolerance, and it accommodates a diverse range of alkene substitution patterns. Results demonstrating the extension of this catalytic system to carboetherification reactions are also presented. [ABSTRACT FROM AUTHOR]

Vinylation by acetylene of lupane-type pentacyclic triterpene C-28- and C-3β-alcohols and C-20-oximes in superbase solutions synthesized the corresponding C-28- and C-3β-O-vinyl ethers and C-20-O-vinyloximes. The reaction of 3β,28-dimethoxy-29-norlupan-20-one with acetylene in superbase KOH–DMSO produced a derivative with an N-vinylpyrrole ring in the C-19 side chain. [ABSTRACT FROM AUTHOR]

Development of innovative technologies for efficient, yet eco-friendly, biomass delignification is required to achieve higher sustainability than traditional processes. In this context, the use of deep eutectic solvents (DESs) for the delignification process could fulfil these requirements and stands today as a promising alternative. This work focuses on understanding the fundamental chemistry behind the cleavage of the β-O-4 ether bond present in 2-phenoxy-1-phenylethanol (PPE), a lignin model compound, with three acidic DESs, including Propionic acid/Urea (PA : U), Lactic acid/Choline Chloride (LA : ChCl) and p-Toluenesulphonic acid/Choline chloride (pTSA : ChCl). The acidic nature of each DES influenced the efficiency of PPE cleavage and determined the extent of further side reactions of cleavage products. Although PA : U (2 : 1) demonstrated the ability to dissolve lignin, it is unable to cleave β-O-4 ether linkage in PPE. On the other hand, LA : ChCl (10 : 1) allowed PPE cleavage, but an esterification between the PPE and lactic acid as well as oligomerization of lactic acid was detected. Among the examined solvents, pTSA : ChCl (1 : 1) demonstrated the highest performance in the PPE cleavage, although the high acidity of this system led to the condensation of cleavage products with prolonged time. The presence of water decreases the ability of DESs for cleavage, but the extension of undesired side reactions was also reduced. Finally, the analysis of intermediates and products of the reactions allowed the identification of a chlorinated species of PPE that precedes the cleavage reaction. A kinetic study using pTSA : ChCl (1 : 1) and pTSA : ChBr (1 : 1) was performed to unveil the role of the halide counterion present in DESs in the cleavage of the β-O-4 ether bond and a new reaction mechanism was herein proposed and supported by density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

Methods for synthesizing C–O digallate structures, the basic unit of diaryl ether components of natural ellagitannins, are described. In the designed building block derived from gallic acid, consonantly overlapped mesomeric effects enhanced its electrophilicity. This building block demonstrated substantial reactivity to improve the synthesis of dehydrodigalloyl, tergalloyl, and valoneoyl groups. [ABSTRACT FROM AUTHOR]

Two cocrystals of 18‐crown‐6 with isophthalic acid derivatives, 5‐hydroxyisophthalic acid and trimesic acid, have been successfully grown by the slow evaporation solution growth technique. Crystal structures of (18‐crown‐6)·6(5‐hydroxyisophthalic acid)·10(H2O) (I) and (18‐crown‐6)·2(trimesic acid)·2(H2O) (II) elucidated by single crystal X‐ray diffraction reveal that both cocrystals pack the centrosymmetric triclinic space group. The molecules are associated by strong/weak hydrogen bonds, π...π and H...H stacking interactions. Powder X‐ray diffraction analyses, experimental and simulated from single‐crystal diffractogram data have been matched. The vibrational patterns in FT–IR spectra are used to identify the functional groups. The band gap energy is estimated by the application of the Kubelka–Munk algorithm. Hirshfeld surfaces derived from X‐ray diffraction analysis reveal the type of molecular interactions and their relative contributions. The constructed supramolecular assembly of crown ether cocrystal is thoroughly described. Both cocrystals exhibit a significant third‐order nonlinear optical response and it is observed that (I) possesses a significant first‐order molecular hyperpolarizability whereas it is negligible for (II). [ABSTRACT FROM AUTHOR]

The reaction mechanism of bimetallic Pd–Zn-catalyzed cycloaddition of alkynyl aryl ethers with internal alkynes has been studied theoretically. Besides cycloaddition reaction, the dimerization of alkynyl aryl ethers was also considered. Both C6H5OC≡CSiiPr3 and C6H5OC≡CSiMe3 were chosen as the substrates. The reactions involve C–H activation of the substrate, acetic acid rotation, H transformation, MeC≡CMe or substrate insertion into the Pd–phenyl bond and reductive elimination steps. It is found that cycloaddition is favored for C6H5OC≡CSiiPr3, while dimerization is preferred for C6H5OC≡CSiMe3, because the steric repulsion between two bulky SiiPr3 groups is relatively large and the steric repulsion between two small SiMe3 groups is relatively small. In addition, besides C6H5OC≡CSiiPr3, four other substrates C6H5CH2C≡CSiiPr3, C6H5C(O)C≡CSiiPr3, C6H5SC≡CSiiPr3 and C6H5N(H)C≡CSiiPr3 have been calculated as the substrates for cycloaddition reaction with MeC≡CMe. Among the five substrates, C6H5OC≡CSiiPr3 has the lowest energy barrier (29.9 kcal mol−1), consistent with the experimental observation that C6H5OC≡CSiiPr3 is the appropriate substrate for successful cycloaddition. [ABSTRACT FROM AUTHOR]

Selective oxidation of ethers to lactones with O2 as a benign oxidant using Au/CeO2 as the catalyst has been developed. The oxygen vacancies and Au0 species on the surface of CeO2 contribute to the activation of O2. The excellent selectivity of lactones is due to the adsorption of ethers and activation of the C(sp3)–H bond on Au/CeO2. [ABSTRACT FROM AUTHOR]

The reaction of activated phenolic compounds, 2,4,6-triaryloxy-1,3,5-triazine (aryl-triazine ethers), with various isocyanates or carbodiimides in the presence of a nickel pre-catalyst resulted in the synthesis of aryl amides in good to excellent yields. [ABSTRACT FROM AUTHOR]

Herein, a novel and scalable synthesis of electron rich 1,3‐dienes based on KOtBu mediated isomerization of propargylic ether derivatives was developed. This new process features easy handling reaction conditions, transition‐metal‐free isomerization, high isolated yields, and most of all, it could be used for modification of natural products at late stage functionalizations. [ABSTRACT FROM AUTHOR]

The hydrogenolysis of the aromatic C−O bond in aryl ethers catalyzed by Ni was studied in decalin and water. Observations of a significant kinetic isotope effect (kH/kD=5.7) for the reactions of diphenyl ether under H2 and D2 atmosphere and a positive dependence of the rate on H2 chemical potential in decalin indicate that addition of H to the aromatic ring is involved in the rate‐limiting step. All kinetic evidence points to the fact that H addition occurs concerted with C−O bond scission. DFT calculations also suggest a route consistent with these observations involving hydrogen atom addition to the ipso position of the phenyl ring concerted with C−O scission. Hydrogenolysis initiated by H addition in water is more selective (ca. 75 %) than reactions in decalin (ca. 30 %). [ABSTRACT FROM AUTHOR]

The hydrogenolysis of the aromatic C−O bond in aryl ethers catalyzed by Ni was studied in decalin and water. Observations of a significant kinetic isotope effect (kH/kD=5.7) for the reactions of diphenyl ether under H2 and D2 atmosphere and a positive dependence of the rate on H2 chemical potential in decalin indicate that addition of H to the aromatic ring is involved in the rate‐limiting step. All kinetic evidence points to the fact that H addition occurs concerted with C−O bond scission. DFT calculations also suggest a route consistent with these observations involving hydrogen atom addition to the ipso position of the phenyl ring concerted with C−O scission. Hydrogenolysis initiated by H addition in water is more selective (ca. 75 %) than reactions in decalin (ca. 30 %). [ABSTRACT FROM AUTHOR]

Obtaining reduced discrete metal atoms that are stable in liquid solvents by in‐situ reduction of an ionic metal precursor has been a challenge until recently. A liquid surfactant polydimethylsiloxane‐polyethylene glycol (PDMS‐PEG) enabled the synthesis of stable discrete platinum atoms (Pt1) by reducing Pt(IV) and Pt(II) salts. Here we report the successful preparation of discrete mononuclear platinum atoms (Pt1) in a crown ether, [15]crown‐5, as a structurally much simpler solvent, and the prepared Pt1@[15]crown‐5 was demonstrated for ultra‐high catalytic activity and selectivity in hydrosilylation reactions. A combination of spectroscopic characterizations proves the reduced Pt species is Pt1(0) with partially positive charge. 195Pt NMR and DFT calculation indicate the Pt1(0) is stabilized by the pseudo octahedral structure of ([15]crown‐5)PtCl−2H+2 involving two adjacent oxygens from the crown ether ring, although the oxygens in the crown ether ring have been known to host and stabilize certain metal cations. The Pt1@[15]crown‐5 shows ultrahigh activity (TOF of 8.3×108 h−1) with excellent terminal adducts selectivity in catalytic olefin hydrosilylation. This catalyst was found to be highly stable under hydrosilylation conditions. For examples, the turnover number (TON) exceeded 1.0×109 for hydrosilylation between 1‐octene and (Me3SiO)2MeSiH without showing sign of deactivation; the TON exceeded 2.0×108 while the catalyst remained active for a catalytically more demanding reaction between styrene and (Me3SiO)2MeSiH. [ABSTRACT FROM AUTHOR]

Ni‐catalyzed C−O(Py) bond activation and silylation of aryl 2‐pyridyl ethers with silylzinc chlorides were carried out. This protocol allowed the 2‐pyridyloxy group to be substituted by a silyl group with short reaction times, mild reaction conditions, and good compatibility of functional groups. [ABSTRACT FROM AUTHOR]

A direct and simple strategy to heteroaryl ethers via a visible‐light‐induced alkoxylation of quinoxalin‐2(1H)‐ones with alcohols under ambient conditions was developed. The commercially available, low cost alcohols served as alkoxylation reagents and solvents. This reaction has advantages of novel protocol, mild conditions, good functional‐group tolerance, and high yields of products. [ABSTRACT FROM AUTHOR]

3p-Methyl ether of dehydroepiandrosterone was obtained by microbiological transformation of 3ß-methyl ether of cholesterol with Mycobacterium sp. Androstane-3,17-dione, androst-4-ene-3,17-dione, and androsta-1,4-diene-3,17-dione were minor transformation products. [ABSTRACT FROM AUTHOR]

Cleavage of aromatic ether bonds is a key step for lignin valorization, and the development of novel heterogeneous catalysts with high activity is crucial. Herein, bifunctional Ru/hydroxyapatite has been prepared via ion exchange and subsequent reduction. The obtained Ru/hydroxyapatite could efficiently catalyze the cleavage of various compounds containing aromatic ether bonds via transfer hydrogenolysis without additional bases. Systematic studies indicated that the basic nature of hydroxyapatite and electron-enriched Ru sites resulted in the high activity of the catalyst. A mechanism study revealed that the direct cleavage of aromatic ether bonds was the main reaction pathway. [ABSTRACT FROM AUTHOR]

The cationic polymerization of C4 mixed feed and isobutylene co-initiated by AlCl3×OiPt2, iBuAlCl2×nOiPr2, and [emim]Cl-FeCl3×nOiPr2 ([emim]Cl: 1-ethyl-3-methylimidazolium chloride) has been investigated. AlCl3×OiPr2 co-initiated cationic polymerization of C4 mixed feed proceeds at a lower rate than polymerization of isobutylene affording polymers with higher molecular weight. Complexes of iBuAlCl2 with diisopropyl ether of different compositions are more suitable co-initiators than AlCl3×OiPr2 for the synthesis of highly reactive polyisobutylene (HR PIB) from C4 mixed feed due to their higher activity in the polymerization as well as possibility to prepare polyisobutylenes with lower molecular weight and higher content of exo-olefin end groups. However, iBuAlCl2 needs activating via addition of external water (initiator) and/or interaction with salts hydrates in order to increase the reaction rate and the saturated monomer conversion. [Emim]Cl-FeCl3/iPr2O is a quite promising catalyst for the preparation of HR PIB with high exo-olefin end group content (> 80%) and relatively low polydispersity (Mw/Mn < 2.8) via cationic polymerization of C4 mixed feed. The sonication of reaction mixture in case of using [emim]Cl-FeCl3 allowed increasing the reaction rate and decreasing the molecular weight. [ABSTRACT FROM AUTHOR]

The development of a cross‐coupling reaction protocol between aryl ethers and Grignard reagents catalyzed by carbodicarbene (CDC) nickel complexes to afford biaryl compounds through C–O cleavage is reported. Aromatic substrates featuring a broad range of electron neutral, donating, or withdrawing groups are introduced at the desired position. The method has proven effective over a wide range of naphthyl methyl ethers, anisoles, and Grignard reagents. The robustness of the protocol is validated by performing multiple cleavage reactions, gram scale synthesis, and arylation of a dimethoxy esterdiol derivative. [ABSTRACT FROM AUTHOR]

Boehmite is a cubic orthorhombic structure of aluminum oxide hydroxide, which prepared via addition of sodium hydroxide solution to an aluminum nitrate solution at room temperature. In this work, the surface of boehmite nanoparticles (BNPs) modified by 3‐choloropropyltrimtoxysilane (3‐CPTMS), then reacted with N,N,N′,N′‐tetraethyldiethylentriamine (TEDETA). Eventually, CuI immobilized on modified boehmite (CuI‐TEDETA@BNPs). Structure of this catalyst was characterized using FT‐IR, TEM, SEM, EDS, TGA, and AAS techniques. Finally, the catalytic activity of CuI‐TEDETA@BNPs was studied for the synthesis of ethers and sulfides. All ethers and sulfides were obtained in high yields, which reveals the high activity of described catalyst. This catalyst was reused for several times without significant loss of its catalytic efficiency. Recovered catalyst was characterized by SEM and FT‐IR techniques, which shown a good agreement with fresh catalyst. Also, heterogeneity and stability of CuI‐TEDETA@BNPs confirmed by hot filtration test. [ABSTRACT FROM AUTHOR]

• Aryl trifluorovinylethers were used as precursors for preparing a diverse pool of hydro-/vinylfluoroethers. • Hydro-/vinylfluoroethers were prepared in a facile base-promoted addition using heteronucleophiles. • Regioselectivity of generated vinylfluoroethers was dependent on heteroatom of the nucleophile as demonstrated by nine examples. • Versatile synthetic methodology of this new class of fluorinated ethers synthesis should garner interest as useful intermediates for a multitude of materials applications. The nature of the structural configuration of fluorinated ethers has been widespread as a crucial component for improving high performance polymers, industrial agrochemicals, and targets for important pharmaceutical drugs. This is a result of countless advances in organo-fluorine methodologies with this unique substructure in order to overcome many traditional synthetic challenges. In this work, we expand on the preparation of fluorinated ethers by introducing hetero-nucleophiles to a highly electrophilic aryl trifluorovinyl ether affording a new class of difunctional aryl/alkyl fluorinated ethers that would serve as useful intermediates. The facile reaction chemistry of various nucleophile substrates, effect of base concerning regio-selectivity, and structural elucidation trends of the synthesized aryl/alkyl fluoroethers will be discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

The review systematizes and generalizes modern approaches to the synthesis of ethers using metal complex catalysts. [ABSTRACT FROM AUTHOR]

Synthetically versatile imidazolium chlorides, especially 1,3‐bis‐(2,6‐diisopropylphenyl)‐imidazolium chloride (IPrHCl) along with copper (I) iodide and cesium carbonate, were found to be useful to form C−O bonds via coupling of phenols and aryl/heteroaryl bromides. In this catalysis, the metal:ligand (Cu:IPr) loading was optimised to 1.0 mol%, making it an inexpensive and a simple one pot catalytic route for synthesising a variety of diaryl ethers. The catalytic cycle was probed by UV‐Vis, FT‐IR and HRMS techniques confirming involvement of a copper‐imidazolium‐carbonate complex. [ABSTRACT FROM AUTHOR]

Six regioisomeric nonracemic dimethylphenyl glycerol ethers were synthesized by asymmetric dihydroxylation of the corresponding allyl dimethylphenyl ethers. The enantioselectivity of the reaction with o-methyl derivatives was lower (down to 34% ee) than with m-methylphenyl ethers (up to 86% ee). Enantiomeric 3-(3,4-dimethylphenoxy)propane-1,2-diols were used to obtain enantiomerically pure physiologically active amino alcohols and their derivatives. [ABSTRACT FROM AUTHOR]

The efficient and metal free, white light mediated 3C alkylation of quinoxalin-2(1H)-ones via a cross dehydrogenative coupling reaction with cyclic ethers using eosin Y as a photocatalyst is described. This reaction has broad substrate scope and strong functional group tolerance with good to excellent yields. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The first cross-dehydrogenative coupling of secondary benzylic ethers. • Isochroman-based tertiary ether synthesis in high efficiency. • Coupling of α-substituted isochromans with indoles and pyrroles. • The first example of catalytic asymmetric cross-dehydrogenative coupling leading to quaternary center. Abstract Current studies on cross-dehydrogenative coupling of benzylic ethers for new C–C bond construction predominantly focus on primary ether moieties. Oxidative cross-coupling of secondary benzylic ethers remains elusive. Herein, we describe the first cross-dehydrogenative coupling of secondary benzylic ethers with indoles and pyrroles for tertiary ether construction. A broad range of α-aryl substituted isochromans react with a variety of electronically varied indoles and pyrroles smoothly under mild metal-free conditions in high efficiency. In addition, the catalytic asymmetric variant was preliminarily explored, and corresponding tertiary ether was obtained in 69% ee. [ABSTRACT FROM AUTHOR]

Reported herein is a novel photoredox‐catalyzed approach for ether synthesis and it involves alkoxyl radicals generated from N‐alkoxypyridinium salts. A wide range of alkenes are smoothly difunctionalized in an anti‐Markovnikov fashion, affording various functionalized alkyl alkyl ethers. Notably, this mild process tolerates a number of functional groups and is efficiently carried out under both batch and flow conditions. Importantly, electron paramagnetic resonance (EPR) experiments by spin trapping were carried out to characterize the radical intermediates involved in this radical/cationic process. Falling into a trap: Alkoxyl radicals generated under visible light photoredox catalysis from N‐alkoxypyridinium salts were efficiently trapped by alkenes in an intermolecular fashion under either batch or flow conditions. This alkoxylation strategy provides access to a wide variety of functionalized alkyl alkyl ethers by the difunctionalization of alkenes with perfect anti‐Markovnikov selectivity. [ABSTRACT FROM AUTHOR]

Abstract: Alkyl aryl ethers are an important class of compounds in medicinal and agricultural chemistry. Catalytic C(sp3)−O cross‐coupling of alkyl electrophiles with phenols is an unexplored disconnection strategy to the synthesis of alkyl aryl ethers, with the potential to overcome some of the major limitations of existing methods such as C(sp2)−O cross‐coupling and SN2 reactions. Reported here is a tandem photoredox and copper catalysis to achieve decarboxylative C(sp3)−O coupling of alkyl N‐hydroxyphthalimide (NHPI) esters with phenols under mild reaction conditions. This method was used to synthesize a diverse set of alkyl aryl ethers using readily available alkyl carboxylic acids, including many natural products and drug molecules. Complementarity in scope and functional‐group tolerance to existing methods was demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: Cross‐hydroalkenylation of a vinyl ether (1) with an α‐olefin (2) was first achieved by a set of [NHC‐Ni(allyl)]BArF (NHC=N‐heterocyclic carbene) catalysts. Both 1,2‐ and 1,3‐disubstituted allyl ethers were obtained, highly selectively, by using NHCs of different sizes. In contrast, the chemoselectivity (i.e., 1 as acceptor and 2 as donor) was controlled mostly by electronic effects through the catalyst–substrate interaction. Sterically bulkier alkenes (2) were used as preferred donors compared to smaller alkenes. This electronic effect also served as a basis for the first tail‐to‐head cross‐hydroalkenylations of 1 with either a vinyl silane or boronic ester. [ABSTRACT FROM AUTHOR]

A synthesis of tricyclic oxoisochromene derivatives via an intramolecular direct arylation of cycloalkyl-1,3-diketone-derived α,β-unsaturated ketone substrates is described. Interesting mechanistic insight has been gathered, based on deuterium migration studies, induced by palladium (Pd). [ABSTRACT FROM AUTHOR]

The utility of RockPhos, Ad-BippyPhos, JosiPhos (CyPF- tBu), and Mor-DalPhos in palladium-catalyzed C-O cross-coupling reactions involving aliphatic alcohols and (hetero)aryl halides under analogous conditions was examined, both at room temperature and at elevated temperature (90 °C). In general, the RockPhos-based catalyst system proved superior, especially at room temperature, but catalysts based on the other ligands examined also proved effective across a range of C-O cross-couplings, in some cases providing better catalytic performance than RockPhos. New reactivity was established in terms of the scope of room temperature reactions. Proof-of-principle examples of such cross-couplings involving aryl mesylates were also demonstrated. [ABSTRACT FROM AUTHOR]

Quercetin (Q) methyl ethers were synthesized from CHI under various conditions. The principal products from the reactions of Q with alkylhalides (CHI, CHBr) in DMF were 3,7,4′-tri-O-alkyl ethers. The structures of the products were confirmed by PMR and C NMR spectra. The antioxidant activity of Q tetra- and tri-O-methyl ethers was demonstrated by chemiluminescence in model systems generating active oxygen species and promoting lipid peroxidation. [ABSTRACT FROM AUTHOR]

• Synthesis of polyfluoroalkylethyl ethers. • Study the phase behavior of fluorinated ethers near the critical values of the fluorine content. • Determination of fluorous partition coefficients and fluorophilicity values of fluorinated ethers by GLC. • The linear relationship between fluorophilicity and the fluorine content in the molecule for the series of CF 3 - and HCF 2 - homologues. A synthetic method of preparing polyfluoroalkylethyl ethers by the reaction of fluoroalcoholates with bromoethane in the presence of KOH (aq), a solubilizer (1,4-dioxane), and tetrabutylammonium bromide was developed. Fluorous partition coefficients and fluorophilicity values of fluorinated ethers were determined in the perfluorooctane/organic solvent system by GLC. The linear relationship between fluorophilicity and the fluorine content in a molecule is characterized by correlation coefficients from 0.96 to 0.999 in the CF 3 - and HCF 2 -series of polyfluoroalkylethyl ethers. [Display omitted] [ABSTRACT FROM AUTHOR]

A simple iron- and silyl chloride catalyzed method for the preparation of symmetrical and nonsymmetrical ethers is presented. Various aldehydes and ketones were reductively etherified by using triethylsilane as a reducing agent in the presence of 2 mol% of iron(III) oxo acetate and 8 mol% of chloro(trimethyl)silane. The reactions can be carried out at ambient temperatures and pressures with ethyl acetate as the solvent. [ABSTRACT FROM AUTHOR]

The use of a gold-catalyzed, microwave protocol to activate alcohols through an intermolecular, SN1-type reaction to directly form unsymmetrical ethers and SN-benzyloxy carbamate- (Cbz) protected amines is reported. Results have shown this reaction to be highly reproducible and tolerant of moisture, and moderate to high product yields (53-99%) were obtained. Significantly, the intermolecular catalytic amination of alcohols to directly afford Cbz-protected amines is heretofore unprecedented using gold catalysis. [ABSTRACT FROM AUTHOR]

Addition of propargylic or homopropargylic ynols to dicobalt hexacarbonyl propargylium cations gave the expected ether products of the Nicholas reaction, with the exception of 4-phenyl-3-butyn-1-ol which gave a dihydrofuran due to propargylium cation promoted 5-endo ring-closure. Use of chiral dicobalt hexacarbonyl complexed propargylic ynols as both propargylium cation precursor and nucleophile gave racemic doubly complexed disymmetric diyne ethers, each as a single diastereoisomer. Addition of dicobalt hexacarbonyl complexed 1-phenyl-1-butyne-3-ene to the propargylium cation derived from dicobalt hexacarbonyl complexed 1-phenyl-1-butyn-3-ol, followed by the addition of a nucleophile (NuH), gave double complexed 1,7-diphenyl-3-Nu-5-methylhepta-1,6-diynes ( d . r . > 10:1). [ABSTRACT FROM AUTHOR]

Five reactions were rate-accelerated relative to the standard reflux workup in both multi-mode and mono-mode microwave ovens, and the results were compared to determine whether the sequential processing of a mono-mode unit could provide for better lab logistics and pedagogy. Conditions were optimized so that yields matched in both types of microwave ovens for a Diels-Alder cycloaddition, Wittig salt formation, Fischer esterifications, an E2 alkyne formation, and Williamson ether synthesis. Typically, a 10-fold rate acceleration was observed under mono-mode heating versus multi-mode heating, reducing the total run-time between 1.5 and 3.0 min per sample, which rivals the batch run-time of a multi-mode unit in ~16 student lab sections. Thus, the mono-mode microwave oven required a similar quantity of total reaction time in the lab, allowing students to run their experiments individually with less wait-time, competition for chemicals, equipment, and instrumentation and to complete the experiments in the lab period. [ABSTRACT FROM AUTHOR]

The reduction of usninic acid pyrazole derivatives by complex boron hydrides under various conditions was studied. New ether derivatives containing added alcohols were obtained upon reduction of the carbonyl. The reaction occurred presumably through a quinonemethide intermediate. [ABSTRACT FROM AUTHOR]