- Regio- And Stereoselective (S N2) N -, O -, C - And S -Alkylation Using Trialkyl Phosphates
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Bimolecular nucleophilic substitution (S N 2) is one of the most well-known fundamental reactions in organic chemistry to generate new molecules from two molecules. In principle, a nucleophile attacks from the back side of an alkylating agent having a suitable leaving group, most commonly a halide. However, alkyl halides are expensive, very harmful, toxic and not so stable, which makes them problematic for laboratory use. In contrast, trialkyl phosphates are inexpensive, readily accessible and stable at room temperature, under air, and are easy to handle, but rarely used as alkylating agents in organic synthesis. Here, we describe a mild, straightforward and powerful method for nucleophilic alkylation of various N -, O -, C - and S -nucleophiles using readily available trialkyl phosphates. The reaction proceeds smoothly in excellent yield, and quantitative yield in many cases, and covers a wide range of substrates. Further, the rare stereoselective transfer of secondary alkyl groups has been achieved with inversion of configuration of chiral centers (up to 98% ee).
- Banerjee, Amit,Hattori, Tomohiro,Yamamoto, Hisashi
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- Preparation of alkylated compounds using the trialkylphosphate
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[Problem] trialkylphosphate strong base used reaction agent, a carboxylic acid, a ketone, an aldehyde, amine, amide, thiol, ester or Grignard reagent to a variety of substrates, and/or high efficiency to generate a highly stereoselective alkylation reaction, the alkylated compounds capable of producing new means. [Solution] was used as the alkylating agent in the alkylation of compound trialkylphosphate, strongly basic reaction production use. [Drawing] no
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Paragraph 0168-0169
(2021/11/02)
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- Chemiluminescence-promoted oxidation of alkyl enol ethers by NHPI under mild conditions and in the dark
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The hydroperoxidation of alkyl enol ethers using N-hydroxyphthalimide and molecular oxygen occurred in the absence of catalyst, initiator, or light. The reaction proceeds through a radical mechanism that is initiated by N-hydroxyphthalimide-promoted autoxidation of the enol ether substrate. The resulting dioxetane products decompose in a chemiluminescent reaction that allows for photochemical activation of N-hydroxyphthalimide in the absence of other light sources.
- Anderson,Andia, Alexander A.,Woerpel
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supporting information
(2021/02/03)
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- Palladium-catalyzed synthesis of α-aryl acetophenones from styryl ethers and aryl diazonium saltsviaregioselective Heck arylation at room temperature
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Preparation of α-aryl acetophenones from styryl ethers and aryldiazonium salts is described. The reaction is catalyzed by palladium acetate at room temperature in the absence of ligand and base. The developed method is highly attractive in terms of reaction conditions, substrate scope, functional group tolerance and yields. Synthetic applications of the present method are demonstrated by preparing α-aryl indoles and 3-aryl isocoumarin from styryl ethers.
- Kandasamy, Jeyakumar,Lee, Yong Rok,Singh, Adesh Kumar,Venkatesh, Rapelly
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supporting information
p. 7832 - 7837
(2021/09/28)
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- Cleavage of aryl-ether bonds in lignin model compounds using a Co-Zn-beta catalyst
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Efficient cleavage of aryl-ether linkages is a key strategy for generating aromatic chemicals and fuels from lignin. Currently, a popular method to depolymerize native/technical lignin employs a combination of Lewis acid and hydrogenation metal. However, a clear mechanistic understanding of the process is lacking. Thus, a more thorough understanding of the mechanism of lignin depolymerization in this system is essential. Herein, we propose a detailed mechanistic study conducted with lignin model compounds (LMC) via a synergistic Co-Zn/Off-Al H-beta catalyst that mirrors the hydrogenolysis process of lignin. The results suggest that the main reaction paths for the phenolic dimers exhibiting α-O-4 and β-O-4 ether linkages are the cleavage of aryl-ether linkages. Particularly, the conversion was readily completed using a Co-Zn/Off-Al H-beta catalyst, but 40% of α-O-4 was converted and β-O-4 did not react in the absence of a catalyst under the same conditions. In addition, it was found that the presence of hydroxyl groups on the side chain, commonly found in native lignin, greatly promotes the cleavage of aryl-ether linkages activated by Zn Lewis acid, which was attributed to the adsorption between Zn and the hydroxyl group. Followed by the cobalt catalyzed hydrogenation reaction, the phenolic dimers are degraded into monomers that maintain aromaticity. This journal is
- Chang, Hou-Min,Dou, Xiaomeng,Jameel, Hasan,Jiang, Xiao,Li, Wenzhi,Zhu, Chaofeng
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p. 43599 - 43606
(2020/12/25)
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- One-Pot Preparation of C1-Homologated Aliphatic Nitriles from Aldehydes through a Wittig Reaction under Metal-Cyanide-Free Conditions
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A one-pot protocol to obtain C1-homologated aliphatic nitriles was achieved by treating aromatic and aliphatic aldehydes with the (methoxymethyl)triphenylphosphonium ylide followed by hydrolysis of the resulting methyl vinyl ethers with pTsOH (Ts = para-toluenesulfonyl) and treatment with molecular iodine and aqueous ammonia under metal cyanide free conditions. Neopentyl-type nitriles, which could not be obtained by conventional methods that involved conversion of the neopentyl alcohol into a tosylate and treatment with metal cyanide, were successfully obtained by using the present method.
- Ezawa, Masatoshi,Togo, Hideo
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p. 2379 - 2384
(2017/05/01)
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- Cleavage of the lignin β-O-4 ether bond: Via a dehydroxylation-hydrogenation strategy over a NiMo sulfide catalyst
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The efficient cleavage of lignin β-O-4 ether bonds to produce aromatics is a challenging and attractive topic. Recently a growing number of studies have revealed that the initial oxidation of CαHOH to CαO can decrease the β-O-4 bond dissociation energy (BDE) from 274.0 kJ mol-1 to 227.8 kJ mol-1, and thus the β-O-4 bond is more readily cleaved in the subsequent transfer hydrogenation, or acidolysis. Here we show that the first reaction step, except in the above-mentioned pre-oxidation methods, can be a Cα-OH bond dehydroxylation to form a radical intermediate on the acid-redox site of a NiMo sulfide catalyst. The formation of a Cα radical greatly decreases the Cβ-OPh BDE from 274.0 kJ mol-1 to 66.9 kJ mol-1 thereby facilitating its cleavage to styrene, phenols and ethers with H2 and an alcohol solvent. This is supported by control experiments using several reaction intermediates as reactants, analysis of product generation and by radical trap with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) as well as by density functional theory (DFT) calculations. The dehydroxylation-hydrogenation reaction is conducted under non-oxidative conditions, which are beneficial for stabilizing phenol products.
- Zhang, Chaofeng,Lu, Jianmin,Zhang, Xiaochen,Macarthur, Katherine,Heggen, Marc,Li, Hongji,Wang, Feng
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supporting information
p. 6545 - 6555
(2018/06/06)
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- Searching for Dual Inhibitors of the MDM2-p53 and MDMX-p53 Protein-Protein Interaction by a Scaffold-Hopping Approach
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Two libraries of substituted benzimidazoles were designed using a 'scaffold-hopping' approach based on reported MDM2-p53 inhibitors. Substituents were chosen following library enumeration and docking into an MDM2 X-ray structure. Benzimidazole libraries were prepared using an efficient solution-phase approach and screened for inhibition of the MDM2-p53 and MDMX-p53 protein-protein interactions. Key examples showed inhibitory activity against both targets.
- Zaytsev, Andrey,Dodd, Barry,Magnani, Matteo,Ghiron, Chiara,Golding, Bernard T.,Griffin, Roger J.,Liu, Junfeng,Lu, Xiaohong,Micco, Iolanda,Newell, David R.,Padova, Alessandro,Robertson, Graeme,Lunec, John,Hardcastle, Ian R.
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p. 180 - 189
(2015/02/19)
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- Synthesis, structure and catalytic activity of a gold(i) complex containing 1,2-bis(diphenylphosphino)benzene monoxide
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The gold(i) complex [Au(dppbO)Cl] was synthesized by reaction of Na[AuCl4]·2H2O with 1,2-bis(diphenylphosphino)benzene (dppb) in the presence of water. This is a new method for the synthesis of a bisphosphine monoxide gold(i) complex. The new gold(i) complex was characterized by NMR spectroscopy and X-ray crystal structure analysis. In the solid state structure a relatively short contact between the oxygen atom of the phosphine oxide group and the gold center was observed. The catalytic activity of [Au(dppbO)Cl] was tested for three different intermolecular alkyne hydrofunctionalization reactions. Silver tetrafluoroborate was used as co-catalyst for halide abstraction. While the bisphosphine monoxide gold(i) complex showed moderate activity for the hydration of various alkynes and the hydroamination of phenyl acetylene, high activity was observed for the hydroarylation of ethylpropiolate. Electron-rich arenes add very fast to the C-C triple bond but with relatively low selectivity.
- Hahn, Christine,Cruz, Leticia,Villalobos, Amanda,Garza, Liliana,Adeosun, Samuel
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p. 16300 - 16309
(2015/01/09)
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- Rhodium-catalyzed anti-Markovnikov intermolecular hydroalkoxylation of terminal acetylenes
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We report here the first transition-metal-catalyzed anti-Markovnikov intermolecular hydroalkoxylation of terminal acetylenes to give enol ethers in high yields without using bases. Arylacetylenes as well as alkenyl- and alkylacetylenes were coupled with aliphatic alcohols, and the products were obtained with high Z selectivity in most cases. Effective catalysts were 8-quinolinolato rhodium complexes, which are structurally simple but have been relatively unexplored as catalysts.
- Kondo, Masataka,Kochi, Takuya,Kakiuchi, Fumitoshi
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body text
p. 32 - 34
(2011/03/16)
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- Intramolecular O-H...O hydrogen-bond-mediated reversal in the partitioning of conformationally restricted triplet 1,4-biradicals and amplification of diastereodifferentiation in their lifetimes
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The photoreactivity and nanosecond transient phenomena have been investigated for a rationally designed set of ketones 4-9 in order to gain comprehensive insights concerning the influence of intramolecular hydrogen bonding on (i) the lifetimes of triplet 1,4-biradicals and (ii) the partitioning of the latter between cyclization and elimination. Comparisons of the photochemical results and lifetime data for the biradicals of ketones 6 versus 8 and 7 versus 9 revealed a remarkable influence of hydrogen bonding when superimposed upon steric factors: while 6 and 7 yielded cyclobutanols in poor yields, cyclization was found to be overwhelmingly predominant for 8-anti and moderately so for 9-anti, with a high stereoselectivity in the formation of cyclobutanols (>95% for 8-anti). The diastereochemistry in the case of 8 permitted the occurrence of fragmentation or cyclization almost exclusively (>90% cyclization for 8-anti and >75% elimination for 8-syn). Significantly, the intramolecular hydrogen bonding in the biradicals of 8 and 9 was found to reverse their partitioning between cyclization and elimination compared with the behavior of the biradicals of ketones 3; the ketones 8-anti and 9-anti underwent cyclization in benzene, predominantly leading to cyclobutanols with syn stereochemistry between the C2 and C3 substituents. In accordance with photoproduct profiles, an unprecedented ~2-fold difference in the lifetimes of the intermediate diastereomeric triplet biradicals of ketones 8 in nonpolar solvents (e.g., τsyn = 123 ns and τanti = 235 ns in cyclohexane) was observed via nanosecond laser flash photolysis, while no such difference in lifetimes was found for the triplet biradicals of acetoxy ketones 9. The intriguing diastereodifferentiation in the lifetimes of the diastereomeric triplet 1,4-biradicals of 8 and the product profiles of ketones 6, 7, and 9 are best reconciled via a unified mechanistic picture in which superposition of steric factors over varying magnitudes of O-H...O hydrogen bonding selectively facilitates a particular pathway. In particular, the diastereodifferentiation in the photochemical outcomes for the diastereomers of ketone 8 and in the lifetimes of their triplet biradicals can be understood on the basis of rapid deactivation of the 8-syn triplet biradical via fragmentation and slow cyclization of the 8-anti triplet biradical from chair- and twist-boat-like hydrogen-bonded conformations, respectively. The photolysis in polar aprotic solvents such as DMSO and pyridine was found to reverse the chemoselectivity, yielding reactivity paralleling that of ketones 3, for which the steric factors between the C2 and C3 substituents control the photochemical outcome.
- Moorthy, Jarugu Narasimha,Samanta, Subhas,Koner, Apurba L.,Saha, Satyajit,Nau, Werner M.
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scheme or table
p. 13608 - 13617
(2009/02/06)
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- o-Quinone methide based approach to isoflavans: application to the total syntheses of equol, 3′-hydroxyequol and vestitol
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A concise strategy is developed for the synthesis of isoflavans employing a Diels-Alder reaction between o-quinone methides and aryl-substituted enol ethers followed by reductive cleavage of the acetal group. The method is extended towards the total syntheses of equol, 3′-hydroxyequol and vestitol.
- Gharpure, Santosh J.,Sathiyanarayanan,Jonnalagadda, Prasad
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p. 2974 - 2978
(2008/09/20)
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- Synthesis of 1-Azaazulenes from Cycloheptatrienylmethyl Ketone O-Pentafluorobenzoyloximes by Palladium-Catalyzed Cyclization and Oxidation
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Various 1-azaazulenes are synthesized from cycloheptatrienylmethyl ketone O-pentafluorobenzoyloximes by treatment with a catalytic amount of Pd(dba) 2-t-Bu3P (dba = dibenzylideneacetone) and triethylamine in the presence of MS 4A via alkylideneaminopalladium(II) intermediates generated by oxidative addition of the oximes to a Pd(0) complex.
- Chiba, Shunsuke,Kitamura, Mitsuru,Saku, Osamu,Narasaka, Koichi
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p. 785 - 796
(2007/10/03)
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- Peroxycarbenium-mediated C-C bond formation: Applications to the synthesis of hydroperoxides and peroxides
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The Lewis acid-mediated reaction of alkene nucleophiles with peroxyacetals provides an effective route for the synthesis of homologated peroxides and hydroperoxides. In the presence of Lewis acids such as TiCl4, SnCl4, and trimethylsilyl triflate, peroxyacetals and peroxyketals undergo reaction with allyltrimethylsilane, silyl enol ethers, and silyl ketene acetals to afford homoallyl peroxides, 3-peroxyketones, and 3-peroxyalkanoates, respectively. Reactions of peroxyacetals are Lewis acid dependent; TiCl4 promotes formation of ethers while SnCl4 and trimethylsilyl triflate promote formation of peroxides. Lewis acid-promoted reactions of silylated hydroperoxyacetals furnish silylated hydroperoxides, which can be deprotected to homologated hydroperoxides. Hydroperoxyketals undergo Lewis acid-mediated allylation to furnish 1,2-dioxolanes via attack of hydroperoxide on the intermediate carbocation. Lewis acid-mediated cyclization of unsaturated peroxyacetals furnishes 1,2-dioxanes, 1,2-dioxepanes, and 1,2-dioxacanes through 6-endo/exo, 7-endo/endo, and 8-endo/endo pathways. The corresponding reactions involving 6-endo/endo and 5-endo/exo pathways were unsuccessful.
- Dussault,Lee, In Quen,Lee,Lee,Niu,Schultz,Zope
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p. 8407 - 8414
(2007/10/03)
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- A new generation of 'instant ylids': Powder mixtures of phosphonium salts and potassium hydride as storable precursors to Wittig reagents
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Mixing a finely pulverized alkyltriphenylphosphonium salt and potassium hydride in 1:1 molar ratio gives a ready-to-use powder the components of which react rapidly when tert-butyl methyl ether is added under stirring. When, in general after a few minutes, the generation of the (triphenylphosphonio)alkanide is complete, it can be immediately used for the Wittig olefination of a carbonyl compound. Compared to sodium amide based 'instant ylids', the new blends offer little advantage as long as simple phosphonium salts are ingredients but they extend considerably the shelf life of mixtures containing heterosubstituted derivatives such as methylthiomethyl- or picolyltriphenylphosphonium salts. Copyright (C) 1996 Elsevier Science Ltd.
- El-Khoury, Mirella,Wang, Qian,Schlosser, Manfred
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p. 9047 - 9048
(2007/10/03)
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- Electrophilic behavior of lithiated 1-alkoxyalkyl and 1-alkylthioalkyl sulfones. Regioselective synthesis of enol ethers and vinyl sulfides
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The readily available 1-alkoxyalkyl and 1-alkylthioalkyl sulfones display electrophilic behavior when lithiated.For example, both react regioselectively with lithiated alkyl sulfones to give enol ethers and vinyl sulfides, respectively.A series of methyl and tert-butyl enol ethers and vinyl sulfides have been prepared. - Keywords: sulfones / alkoxyalkyl sulfones / carbenoids / enol ethers / heterosubstituted carbanions / alkylthioalkyl sulfones / vinyl sulfides
- Habermann, Anne-Kathrin,Julia, Marc,Verpeaux, Jean-Noel,Zhang, Da
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p. 965 - 972
(2007/10/02)
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- Synthesis of Cyclic and Acyclic Enol Ethers (Vinyl Ethers)
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A general method has been developed for the conversion of both cyclic and acyclic acetals of cyclic ketones, acyclic ketones, and aldehydes into enol ethers through treatment of the acetal with trimethylsilyl triflate in the presence of N,N-diisopropylethylamine.The range of isolated yields of enol ethers from the various classes of acetals was as follows: cyclic acetals of cyclic ketones, 83-98percent; acyclic acetals of ketones, 72-94percent; acyclic and cyclic acetals of aldehydes, 65-90percent.
- Gassman, Paul G.,Burns, Stephen J.,Pfister, Keith B.
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p. 1449 - 1457
(2007/10/02)
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- THE METHYLENATION OF ENOLIZABLE KETONES AND ESTERS USING ORGANOTITANIUM CHEMISTRY
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The titanium methylidene fragment, Cp2Ti=CH2, resulting from Tebbe's reagent, Cp2TiCH2*AlMe2Cl or the β,β-disubstituted metallacycle, Cp2TiCH2C(Me)(n-Pr)CH2, methylenates enolizable acidic ketones and converts α,α-disubstituted ketones into titanium enolates.The reagent reacts selectively with ketones over esters.
- Clawson, Leigh,Buchwald, Stephen L.,Grubbs, Robert H.
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p. 5733 - 5736
(2007/10/02)
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- SYNTHESIS OF VINYL ETHERS BY HOMOLOGATION OF ALDEHYDES VIA RADICAL REDUCTIVE ELIMINATION
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Methoxyphenylthiomethyllithium 1 reacts with aldehydes to give adducts which are then transformed into xanthates.These compounds, by reaction with tri-n-butylstannane, afford vinyl ethers in good yields.
- Vatele, Jean-Michel
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p. 5997 - 6000
(2007/10/02)
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- Nucleophilic Substitutions of Unactivated Vinyl Halides with Alkanethiolate Anions in Hexamethylphophoramide
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The reactions of unactivated vinyl halides with the sodium salts of alkanethiols in HMPA gave vinyl alkyl sufides in high yields.These reactions occur with complete retention of configuration.With di-, tri-, and tetrachloroethylenes all the chlorine atoms are substituted by alkylthio groups.By treatment with alkanethiolates the vinyl sulfides are dealkylated to give the sodium salts of the ene thiols.By reaction with sodium all the alkylthiogroups present in the molecule suffer fragmentation to give the sodium salts of the corresponding mercaptoethylenes.
- Tiecco, Marcello,Testaferri, Lorenzo,Tingoli, Marco,Chianelli, Donatella,Montanucci, Manuela
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p. 4795 - 4800
(2007/10/02)
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- The Allopolarization Principle and its Applications, VI. The Alkylation of Enolate Anions: Polarity and Regioselectivity
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The O/C methylation ratio in the reaction of sodium enolates with dimethylsulfate depends on the polar (electronic) effect of substituents.The relative ?-charge density Px/y = lx/ly can be used as a measure for the polarity of ambifunctional anions; in case of enolate anions PO/C = lO/lC.The change of the regioselectivity Sf = log QO/QC in the alkylation of enolates is a function of a change in the polarity PO/C; ΔSf=f(ΔPx/y).The polar effect of substituents influences the charge control during the alkylation process via a change of the polarity of the enolate system: The higher the polarity of the anion, the stronger the charge control and the higher the yield of enol ether (O-alkylation). - Keywords: Alkylation, Enolate Anions
- Gompper, Rudolf,Vogt, Hans-Hubert,Wagner, Hans-Ulrich
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p. 1644 - 1652
(2007/10/02)
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