Ethers on a benzene ring
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Category:Benzofuran ethers at the benzene ring ; Upload media. bookmakersports.website Wikipedia · Authority control. Wikidata Q Aromatic ethers undergo Friedel-Crafts alkylation to give o-and p- alkyl anisole and with acylation it gives o- and p- alkoxy acetophenone. definition. In this study, mild conditions for aromatic substitutions during the syntheses of aryl ethers were developed. In the reaction conditions, the. GRAFICO BITCOIN TRADE
Nomenclature Ethers are commonly named by listing the names of the groups attached to the oxygen atom and adding the word ether. Examples include: IUPAC nomenclature names ethers as alkoxy alkanes, alkoxy alkenes, or alkoxy alkynes. The group in the chain that has the greatest number of carbon atoms is designated the parent compound. In the case of aromatic ethers, the benzene ring is the parent compound.
Physical properties The bonds between the oxygen atom and the carbon atoms of the alkyl groups in an ether molecule are polarized due to a difference in electronegativities between carbon and oxygen. These facts show that ether molecules must be dipoles molecules having both a center of positive and negative charge with weak polarities.
Thus, the structure of ether is similar to that of water. However, in water the hydrogen atoms have a greater partial positive charge than the hydrogen atoms on ether. In water, the charge is localized only on the hydrogens and not delocalized spread throughout as with the alkyl groups, so the charge is stronger in water than in ethers.
Comparisons were then pursued among four functionalized DAEs—diphenyl ether, 4-phenoxyanisole, 4-phenoxytoluene and 4-phenoxyphenol—together with their reaction products. Based on the combined results of rate comparisons, substituent electronic and positional studies, isotope labeling experiments, and regioselectivity investigations, two distinct mechanisms for C-O cleavage were established for the four representative functionalized substrates.
Extension to ortho- and meta-substituted analogues, and analysis of the effects of a suite of additional substituents revealed their impacts on the rates and selectivities of aryl C-O bond cleavage, and also uncovered the activation of various functional groups CH3, CF3 commonly seen as unreactive. The mechanistic insights obtained also uncovered conditions in which the strong sp2 C-O ether bond could be cleaved without over reduction of the monomeric phenolic products.
Two potential routes to these products can be envisioned for the cleavage process. Phenol then undergoes fast ring saturation to generate cyclohexanol. In Route B, one of the phenyl rings first undergoes ring hydrogenation, converting it into cyclohexyl phenyl ether; C-O cleavage then gives benzene and cyclohexanol. Full size image To determine which of paths A or B is preferred, the reaction time sequences were analyzed.
As shown in Fig. Importantly, however, neither cyclohexane nor cyclohexyl phenyl ether were detected. If the latter aryl alkyl ether product were indeed formed, it would not be expected to cleave to cyclohexanol and benzene; other simple alkyl phenyl ethers such as anisole are unreactive under these conditions. Our previous study of 2-phenoxyacetophenone cleavage had found acetone to be an inhibitor of phenol ring reduction and explored its use to tune reduction selectivity Thus, the direct cleavage pathway A is preferred; if partial or total ring reduction Route B preceded ether cleavage, in the presence of acetone as co-solvent, cyclohexanol should arise in parallel with phenol production.
Diphenyl ether undergoes slow isotope exchange To further probe the cleavage mechanism of DPE, isotope labeling experiments were performed. Under more vigorous reaction conditions using freshly activated Ni catalyst with applied current, the amount of isotope incorporation was still very low in the recovered DPE, as it was undergoing cleavage into benzene and phenol for details, see Supplementary Fig.
This suggests that upon Ni insertion into the ortho C-H bond of the activated benzene ring, forward reaction to cleave the C-O ether bond dominates over reversal that would scramble the ortho hydrogens with surface deuterium atoms. As shown by the studies above, however, the activated ring of diphenyl ether is not reduced prior to the C-O cleavage. A more attractive alternative exchange pathway is reversible ortho-metallation of a C-H site, pointing to a benzyne pathway for ether cleavage vide infra.
Proposed C-O cleavage mechanisms of diphenyl ether On the basis of the above information, three different direct C-O cleavage mechanisms of diphenyl ether were proposed. In route I, double ring coordination allows ortho C-H insertion on the phenyl ring that is perpendicular to the catalytic surface Fig. Elimination of the vicinal phenoxide then forms a surface-bound benzyne intermediate, which is rapidly reduced to benzene by reaction with surface hydrogen atoms.
For additional time courses and product analyses see supplementary Fig. The dotted orange line highlights the variability in analysis due to borderline solubility of this substrate in the reaction medium. Full size image An alternative candidate cleavage via single ring activation is shown in route II Fig. Here, with one of the phenyl rings coordinated to the catalyst, oxidative C-O insertion by Ni followed by reductive elimination with hydrogen could directly break the ether bond.
This pathway has been demonstrated in single metal Ni molecular catalysis studies, where the nickel center was spatially positioned and electronically modified by its ligand donor set Lastly, Route III, also beginning with single ring binding, would activate the phenyl ring by delivery of a surface-bound hydrogen atom to the ipso sp2 carbon of the bound ring, followed by rearomatization of the coordinated ring via cleavage of the C-O bond.
As presented in Fig. To identify the preferred DAE cleavage mechanism, further time-course, substituent effect, and isotopic labeling studies were pursued. Besides the proposed cleavage paths, Fig. In contrast to the fast C-O cleavage, the isotope incorporation is slow. Evidently, if the ortho carbon activation represents the first step in the cleavage process, the forward C-O cleavage predominates over the reverse process, replacing the original hydrogen with deuterium. Alternative exchange paths such as reversible hydrogenation involving the ortho carbon appear less likely, given the observed resistance of aryl ethers to hydrogenation.
Addition would also lead to an anti-relationship between the bound Ni surface and the ortho C-H in the CHD site, complicating the release of the ortho hydrogen and retention of deuterium. These predict opposite cleavage selectivities; the dual-ring coordination would lead to cleavage of the left C-O bond, while the single-ring coordination cleaves the right C-O bond. Study of the symmetrical diphenyl ether substrate could not fully differentiate the mechanisms, since all the paths lead to the same products benzene, phenol.
However, with a substituent on one of the aryl rings, the different coordination modes would generate different cleavage products Fig. Therefore, 4-phenoxyanisole, the singly para-methoxylated DPE was synthesized and its cleavage regioselectivity was examined. This cleavage result anisole and phenol is also opposite to those seen in previous reports interpreted in terms of oxidative insertion Route II 35 , Meanwhile, the reaction of bis- 4-methoxyphenyl ether disubstituted methoxylated model was extremely sluggish For details, see Supplementary Fig.
The rate contrast between mono- and di-substituted methoxylated DPE Fig. Importantly, ECH of para-methoxylated DPE also rules out hydrolysis as a significant pathway of diaryl ether C-O cleavage; hydrolysis would yield 4-methoxyphenol and phenol. But as shown in Fig. As predicted by Route I, the cleavage rates of plain DPE purple hexagon and the para-methoxylated navy diamond and methylated blue hollow circle analogues are similar, suggesting that in the cleavage mechanism these moieties do not directly interact with the catalytic surface in a way that significantly affects the cleavage processes Fig.
C-O ether bond cleavage rate of different electron-donating group substituted diphenyl ether under standard ECH condition. Full size image A strikingly different result was observed in the case of 4-phenoxyphenol, the singly para-hydroxylated analogue orange circle of DPE.
Here, the presence of the hydroxyl group in the aromatic ring significantly accelerates the C-O cleavage. Our previous studies suggested that the electron-rich nucleophilic nickel cathode surface has a high affinity for the carbonyl functionality As with phenol itself, the hydroxyl site on the phenolic ring can equilibrate with the keto form, which binds tightly to the nucleophilic nickel surface, resulting in rapid cleavage. Second, the exchange locations were at the same carbon site for both, ortho to the C-O bond being cleaved.
Notably, the exchange in the latter substrate occurs on the anisole ring, not the phenyl. Meanwhile, the anisole formed as the cleavage product was doubly deuterated at a level almost independent of the slow deuteration of starting material for details see Supplementary Fig. These similar behaviors imply that these two diaryl ethers react via similar cleavage mechanisms Fig.
Full size image Fast benzylic activation on the methyl group is independent of the ether cleavage mechanism Introducing a methyl moiety to the diphenyl ether system slightly slowed the overall cleavage rate Fig. Similar growth rates of D1, D2, and D3 suggested that once the Ni inserted at the benzylic carbon, the incorporation of D happened rapidly Fig.
Thus, on the basis of its cleavage products toluene and phenol; see Supplementary Fig. As predicted by this picture, a small amount of penta-deuterated toluene was detected among cleavage products from the exchange experiment for details, see Supplementary Fig. Thus, the ether cleavage reaction proceeds via the same mechanism as the unsubstituted DPE Route I , but with a small slowdown due to competition with the methyl group for binding.
Analogous behavior is also seen in the trifluoromethyl-substituted analogue, as detailed below. Orienting the substituted ring perpendicular to the Ni surface enables the activation of this ortho aromatic C-H but not those of the unsubstituted phenyl ring. Meanwhile, the parallel adsorption of the unsubstituted phenyl ring to the nickel surface is also required.
Notably, bis- 4-methoxyphenyl ether has low reactivity Fig. Overall, a dual ring coordination mechanism that leads to a surface-bound aryne intermediate is proposed for the cleavage of diphenyl ether DPE and its corresponding methoxy and methyl congeners Fig. The fast outlier: hydroxylated-DPE Only cyclohexanol and phenol were observed as the products from ECH of the hydroxylated model, also known as 4-phenoxyphenol for details, see Supplementary Fig.
The D sequential growth processes in Fig. Full size image The above rate and labeling site differences strongly suggest that hydroxylated DPE cleaves via a mechanism different from that working in the other three models.
After phenoxide removal, the surface-bound cyclohexadienone would be either rapidly reduced to cyclohexanol or released and rearomatized via tautomerization back to phenol. Importantly, a comparison of the inhibitory effects of acetone on the cleavage rates of simple DPE vs. However, for the hydroxylated analogue, the cleavage half-life changes from ca. Effects of substituent position on cleavage rates Not surprisingly, variations in the positions of the above-discussed substituents also exert potent effects on the rates.
Especially for the methoxy and methyl substituents, the ortho-substituted DPEs had very low reactivity. Importantly, this pattern of rate decreases with changing substituent positions was consistent across all three types of substituents. Regioselectivity distribution of para, meta and ortho-substituted structures of h methoxylated diphenyl ether i methylated diphenyl ether. For additional time courses and product analyses see supplementary Figs.
Full size image The above reactivity trends may be attributed to binding and reactivity modulation due to variations in the torsion angles around the respective ether C-O bonds. The closer the R group lies to the ether linkage between the two aromatic rings, the stronger the expected twisting distortion will be. Compared with a mononuclear molecular catalyst 35 , binding to the heterogeneous Ni catalyst surface is presumably more sterically demanding, creating a higher barrier to cleavage in those distorted structures.
But in the case of ortho substituents, the direct clash between the R group and the catalytic surface generates a mismatch, which significantly inhibits the cleavage. Despite the decreases in cleavage rates with substituent position, for the hydroxylated model, all three structures still react significantly faster than the corresponding methyl and methoxy systems Fig.
This overall faster conversion supports the idea that the hydroxylated DPE analogues react via mechanisms different from those of the methyl and methoxy cases. Evidently, enhanced substrate binding via enol to keto tautomerization is effective for all three phenoxyphenol isomers, albeit much weaker in the ortho case.
We speculate that in the ortho phenoxyphenol Fig. C-O ether bond cleavage regioselectivity in aryl phenyl ethers With one ring substituted, the two aromatic rings are no longer identical, setting up an internal competition between the two possible C-O bond cleavage sites Fig. Here we examine the cleavage regioselectivity of the three models para-substituted methyl, methoxy, hydroxyl and several other examples with substituents on the 4 position of one of the benzene rings.
Figure 7g summarizes the regioselectivity distribution of all the tested para-substituted aryl ethers. As shown, all of the ethers preferred cleavage on the left-hand side blue bars , breaking the C-O bond connected to the substituted aromatic ring. These selectivities are insensitive to variations in current and thus to electrode potential; for details, see Supplementary Fig.
Lowering current only decreases the cleavage rate, presumably due to the decreased rate of active hydrogen production. However, in these strongly reducing conditions, most of the electron-withdrawing functionalities were reduced prior to aryl C-O cleavage. For example, the acetyl group was rapidly reduced to the corresponding alcohol, which then underwent C-O ether bond cleavage Supplementary Fig.
This result accords with the earlier noted strong preference of the Ni to bind and reduce carbonyl compounds. But even strong bonds like the sp3 C-F in trifluoromethyl were completely reduced to C-H before the C-O ether bond cleavage. No trifluoromethyl benzene the direct cleavage product was observed, but both toluene and phenoxytoluene, the defluorinated substrate, were easily detected Supplementary Fig.
Thus, all the fluorines were replaced prior to C-O cleavage. Notably, ECH cleavage of the CF3 substituted aryl ether was the slowest among those studied here for rate comparisons, see Supplementary Fig.
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As with alcohols, only saturated carbon atoms may be substituted in alkenes and alkynes.
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|Betmgm first bet promo||If the latter aryl alkyl ether product were indeed formed, it would not be expected to cleave to cyclohexanol and benzene; other simple alkyl phenyl ethers such as ethers on a benzene ring are unreactive under these conditions. Benzyne intermediates have also been identified in LEED and HREELS experiments on metal surfaces, including Ni, that have been dosed with benzene and warmed, with evidence pointing to the benzyne ring plane being tilted from the surface The figure above left is for PEK one ether, one ketone with two intervening benzene rings and the one on the right is for PEEK, the polymer with two ethers and one ketone plus three intervening benzene rings. That is, the attacking nucleophile approaches the substituted aliphatic carbon and smoothly replaces the leaving group, all in one smooth process with only one transition state. Lignin, the other major fraction 9 read article, 10has potential as a carbon-rich feedstock to make both renewable fuels and chemicals 111213but its ethers, strong linkages make it recalcitrant. Elimination of the vicinal phenoxide then forms a surface-bound benzene ring intermediate, which is rapidly reduced to benzene by reaction with surface hydrogen atoms.|
|Ethers on a benzene ring||Click on either image and you can view a 3D version that you can rotate and zoom. Further support for the proposed Route I pathway is found in the isotopic labeling in the products of the ether cleavage for details and discussion, see Supplementary Figs. Importantly, ECH of para-methoxylated DPE also rules out hydrolysis as a significant pathway of diaryl ether C-O cleavage; hydrolysis would yield 4-methoxyphenol and phenol. There are two requirements for NAS to occur. Full size image To determine which of ethers on a benzene ring A or B is preferred, the reaction time sequences were analyzed.|
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|Ethers on a benzene ring||Study of the symmetrical diphenyl ether substrate could not fully differentiate the mechanisms, since all the paths lead to the same products benzene, phenol. With the acetone additive, however, both water-soluble and insoluble diaryl ethers can be selectively cleaved into aromatic monomers with minimal ring reduction. Therefore, ether molecules cannot form hydrogen bonds with other ether molecules. Comparisons were then pursued among four functionalized DAEs—diphenyl ether, 4-phenoxyanisole, 4-phenoxytoluene and 4-phenoxyphenol—together with their reaction products. Notably, ECH cleavage of the CF3 substituted aryl ether was the slowest among those studied here for rate comparisons, see Supplementary Fig. Analogous, albeit highly constrained, structures have been observed in molecular complexes as well 55 ,|
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|Nba logo bedding||Because the fluorine likes extra electron density around itself and pulls it from the carbon it's attached to, kind of like movies stars attracting paparazzi. Clearly observed bubbling on the carbon electrode surface suggested successful hydrogen evolution, but essentially no aryl ether cleavage product was detected Supplementary Fig. Normally the SN2 acronym for substitution-nucleophilic-second-order reaction involves a one-step process with a single transition state. Selective inhibition with acetone allows selectivity for cyclohexanol or phenol products Since the cleavage takes place without immediate reduction of the aromatic products, it is possible to select for phenolic or cyclohexanol products via the use ethers acetone to prevent phenol reduction, as exploited in the opening discussion that ruled out the formation benzene ring cyclohexyl phenyl ether. In higher temperature classical nickel-catalyzed reductions, 2-propanol has been used as a liquid source of hydrogen 66 Further support for the proposed Route I pathway is found in the isotopic labeling in the products of the ether cleavage for details and discussion, see Supplementary Figs. This qualitatively different behavior pattern is additional evidence that phenolic substrates react via a mechanism different from the path followed by all the other substituted DAEs studied here.|
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They can be used as the therapeutics for treating and preventing the skin disease caused by over-reproduced melanin. Ar—[O— X p—R? I Polymers formed from the functionalized phenolics are expected to have controllable degradation profiles, enabling them to release an active component over a desired time range.
The polymers are also expected to be useful in a variety of medical applications. The conduit reactor utilized contains wettable fibers onto which one stream is substantially constrained and a second stream is flowed over to continuously create a new interface there between to efficiently bring about contact of the reactive species and thus promote reactions thereof or extractions thereby.
Co-solvents and phase transfer catalysts may be employed to facilitate the process. Type: Application Publication date: May 24, Inventors: Elena Benedetti, Pietro Campaner, Daniele D'Amico, Andrea Minigher, Cristina Stifani, Antonella Tarzia Adamantane derivative, method for producing the same, and resin composition containing adamantane derivative Patent number: Abstract: Adamantane derivatives are provided including a phenolic hydroxyl group-containing adamantane derivative, a glycidyloxy group-containing adamantane derivative, and an adamantyl group-containing epoxy modified acrylate, which exhibit excellent transparency, light resistance, and heat resistance properties.
Also provided are resin compositions containing the adamantane derivatives. Further provided are corresponding methods for producing the adamantane derivatives, as well as the resin compositions containing the same. The invention further provides a process for producing such a catalyst- and lignin-comprising composition and its use for preparing an aromatics composition.
The phosphazene-supported catalyst is highly effective to catalyze various organic reactions, and further has no reduction of activity even after recovery and reuse of the catalyst, thus it being economically advantageous. In addition, the polymerization of cyclic monomers, substitution of substituents, carbon-carbon bond forming reactions and the like can be conducted with extremely high efficiency. A process for conversion of a lignin material to bio-fuels can include subjecting the lignin material to a base catalyzed depolymerization reaction to produce a partially depolymerized lignin.
Following partial hydrodeoxygenation, the partially hydrodeoxygenated product can be reacted in a hydroprocessing step to form a bio-fuel. Each of these reaction steps can be performed in single or multiple steps, depending on the design of the process. The production of an intermediate partially hydrodeoxygenation product and subsequent reaction thereof can significantly reduce or eliminate reactor plugging and catalyst coking. Zmierczak, Jan D.
Miller Spatially-defined macrocyclic compounds useful for drug discovery Patent number: Abstract: Novel spatially-defined macrocyclic compounds containing specific conformational control elements are disclosed. Libraries of these macrocycles are then used to select one or more macrocycle species that exhibit a specific interaction with a particular biological target. In particular, compounds according to the invention are disclosed as agonists or antagonists of a mammalian motilin receptor and a mammalian ghrelin receptor.
Hoveyda, Sylvie Beaubien, Mark L. Peterson Polyether polyols based on cashew nutshell liquid and flexible foams Patent number: Abstract: This invention relates to novel polyether polyols which are prepared by alkoxylation of renewable resource materials, and particularly cashew nutshell liquid CNSL , and to a process for the preparation of these novel polyether polyols. This invention also relates to flexible polyurethane foams prepared from these long chain polyether polyols, and to a process for the production of these flexible polyurethane foams.
Type: Grant Date of Patent: June 1, Assignee: Sumitomo Chemical Company, Limited Inventor: Kazuaki Sasaki Sulphonylated diphenylethylenediamines, method for their preparation and use in transfer hydrogenation catalysis Patent number: Abstract: A diamine of formula I is described, in which A is hydrogen or a saturated or unsaturated C1-C20 alkyl group or an aryl group; B is a substituted or unsubstituted C1-C20 alkyl, cycloalkyl, alkaryl, alkaryl or aryl group or an alkylamino group and at least one of X1, X2, Y1, Y2 or Z is a C1-C10 alkyl, cycloalkyl, alkaryl, aralkyl or alkoxy substituting group.
The chiral diamine may be used to prepare catalysts suitable for use in transfer hydrogenation reactions. Inventors: Beatriz Dominguez, Antonio Zanotti-Gerosa, Gabriela Alexandra Grasa, Jonathan Alan Medlock Sulphonylated diphenylethylenediamines, method for their preparation and use in transfer hydrogenation catalysis Patent number: Abstract: A diamine of formula I is described, in which A is hydrogen or a saturated or unsaturated C1-C20 alkyl group or an aryl group; B is a substituted or unsubstituted C1-C20 alkyl, cycloalkyl, alkaryl, alkaryl or aryl group or an alkylamino group and at least one of X1, X2, Y1, Y2 or Z is a C1-C10 alkyl, cycloalkyl, alkaryl, aralkyl or alkoxy substituting group.
The multifunctional alcohols or polyols can be used in polyurethanes and polycarbonates. The multifunctional crosslinkers can be used in optical coating and waveguide compositions to increase curing speed and crosslink density. The multifunctional phosphates can be used in flame resistant plastics as the highly pendant phosphorus containing phosphate non-halogen flame retardant additives. One preferred compound is 2,3-dimethoxymethyl-[1,4]benzoquinone, also known as coenzyme Q0 CoQ0.
Also disclosed are novel compounds and intermediates, and a method for the preparation of coenzyme Qn, preferable the coenzyme Q Inter alia, the invention relates to a process for the manufacture of a compound of the formula II, or a salt thereof, and a compound of formula VI or a salt thereof, wherein R3 and R4 as well as Act are as defined in the specification, and processes of manufacturing these.
The chelating moiety stabilizes the sulfonate leaving group by forming a complex with a cation of a cation-nucleophile combination. The stabilized leaving group is more easily displaced under many conditions than are standard arylsulfonate leaving groups such as the toxyl group. The chelating moiety also favors certain cations depending on the identity of the moiety thereby enhancing the reaction rate with nucleophilic salts containing the preferred cation.
Use of the inventive leaving groups results in improved yields, decreased reaction times and improved product purity. The hydrophobic polyols can be used in polyurethane systems, in coatings, adhesive bonds, sealants or moulding compounds, which can be used to coat substrates.
Type: Grant Date of Patent: July 1, Assignee: Bayer MaterialScience AG Color stabilization of hydroquinone hydroxyethyl ether products Patent number: Abstract: The present invention relates to the color stabilization of hydroquinone hydroxyethyl ethers by phosphite compounds containing the bis-cyclic structure of spiro phosphites, both rings being attached to the same tertiary carbon atom in the phosphite molecule.
Substituted stilbenes and their reactions Patent number: Abstract: The present invention relates to stilbene and quinone compounds related to combretastatin A-4 and their use as anticancer compounds and prodrugs. The present invention further relates to the photochemical reactions of stilbene compounds, either the above compounds disclosed for the first time herein or compounds based on prior art stilbenes. Thus, the structure of ether is similar to that of water. However, in water the hydrogen atoms have a greater partial positive charge than the hydrogen atoms on ether.
In water, the charge is localized only on the hydrogens and not delocalized spread throughout as with the alkyl groups, so the charge is stronger in water than in ethers. Like water, ether is capable of forming hydrogen bonds. However, because of the delocalized nature of the positive charge on the ether molecule's hydrogen atoms, the hydrogens cannot partake in hydrogen bonding.
Thus, ethers only form hydrogen bonds to other molecules that have hydrogen atoms with strong partial positive charges. Therefore, ether molecules cannot form hydrogen bonds with other ether molecules. This leads to the high volatility of ethers. Ethers are capable, however, of forming hydrogen bonds to water, which accounts for the good solubility of low molecular weight ethers in water.
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