- Hydrosilylation of aromatic azomethines
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The reactions of aromatic azomethines with methyldichlorosilane, phenyldichlorosilane, and dimethylchlorosilane, performed in the presence of Speier's, Wilkinson's, and Karstedt's catalysts and a series of Pt(II) complexes LL'PtCl2, give hydrosilylation and reduction products whose ratio depends on the catalyst used. The highest yield of hydrosilylation products is attained with Pt(II) complexes as catalysts.
- Zuev,Kovaleva,Skvortsov
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Read Online
- A new alkylation of aryl alcohols by boron trifluoride etherate
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The ethylation of aryl alcohols by an ethyl moiety of boron trifluoride etherate is described. The reaction proceeded cleanly and afforded good yields of the corresponding aryl ethyl ethers. It tolerated the presence of functional groups such as aryl, alkyl, halogens, nitro, nitrile, and amino. However, the presence of amino or nitro groups ortho to a hydroxyl group of an aryl compound drastically reduced the yields of the anticipated products due to the chelation of the aforementioned functional groups with boron trifluoride etherate. A nitrogen atom in the aromatic ring system, as exemplified by hydroxypyridine and 8-hydroxyquinoline, completely inhibited the reaction. Resorcinol, hydroquinone, and aryl alcohols with aldehyde functions decomposed under the reaction conditions.
- Jumbam, Ndze Denis,Maganga, Yamkela,Masamba, Wayiza,Mbunye, Nomthandazo I.,Mgoqi, Esethu,Mtwa, Sphumusa
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- Transition-Metal-Free C-C, C-O, and C-N Cross-Couplings Enabled by Light
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Transition-metal-catalyzed cross-couplings to construct C-C, C-O, and C-N bonds have revolutionized chemical science. Despite great achievements, these metal catalysts also raise certain issues including their high cost, requirement of specialized ligands, sensitivity to air and moisture, and so-called "transition-metal-residue issue". Complementary strategy, which does not rely on the well-established oxidative addition, transmetalation, and reductive elimination mechanistic paradigm, would potentially eliminate all of these metal-related issues. Herein, we show that aryl triflates can be coupled with potassium aryl trifluoroborates, aliphatic alcohols, and nitriles without the assistance of metal catalysts empowered by photoenergy. Control experiments reveal that among all common aryl electrophiles only aryl triflates are competent in these couplings whereas aryl iodides and bromides cannot serve as the coupling partners. DFT calculation reveals that once converted to the aryl radical cation, aryl triflate would be more favorable to ipso substitution. Fluorescence spectroscopy and cyclic voltammetry investigations suggest that the interaction between excited acetone and aryl triflate is essential to these couplings. The results in this report are anticipated to provide new opportunities to perform cross-couplings.
- Liu, Wenbo,Li, Jianbin,Querard, Pierre,Li, Chao-Jun
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p. 6755 - 6764
(2019/05/06)
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- Synthetic method for dapagliflozin
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The invention relates to a synthetic method for dapagliflozin. The synthetic method is characterized in that 4-methylphenol is taken as a starting raw material, alkylation and bromination are performed, an alkylation reaction is performed with antisepsin, diazotization and chlorination are performed, and condensation, etherification and desmethoxy are performed with 2,3,4,6-tetrakis-O-trimethylsilyl-D-gluconolactone to obtain a hypoglycemic drug (dapagliflozin). The synthetic method has the following advantages: 4-methylphenol is taken as the starting raw material, and 4-methylphenol is low inprice and easily accessible than 5-bromo-2-chlorobenzoic acid; by adoption of the process, industrialization can be easily realized; in the synthesis process, raw materials which are highly toxic arenot used, so that dangerous processes are avoided; the synthesis path is short and novel, so that the operation is simple and convenient; and by adoption of the synthesis path, the purity of a finalproduct can be improved, and the purity can be 99% or above.
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Paragraph 0015
(2018/03/26)
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- Preparation method of dapagliflozin intermediate
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The invention provides a preparation method of a dapagliflozin intermediate. The preparation method comprises the following steps: (1) by taking 4-methylphenol and bromoethane as raw materials, a polar solvent as a reaction solvent and an inorganic base as a catalyst, carrying out reaction for preparing 4-ethyoxyl methylbenzene; (2) by taking N-chlorosuccinimide and 4-ethyoxyl methylbenzene obtained in the step (1) as raw materials, a non-polar solvent as a reaction solvent and dibenzoyl peroxide as an initiator, carrying out reaction, thus obtaining 4-ethyoxyl benzyl chloride; (3) dissolving 4-ethyoxyl benzyl chloride obtained in the step (2) and 4-bromaniline into ethyl acetate, adding a catalyst lewis acid, and carrying out reaction, thus obtaining 5-bromo-2-amino-4-ethyoxyl diphenylmethane; and (4) carrying out diazotization reaction on 5-bromo-2-amino-4-ethyoxyl diphenylmethane obtained in the step (3), and then reacting with cuprous chloride, thus synthesizing 5-bromo-2-chloro-4'-ethyoxyl diphenylmethane. The preparation method provided by the invention has the advantages of low cost, low environmental stress and short synthetic route.
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Paragraph 0022; 0023; 0024; 0025
(2018/03/01)
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- Practical Ligand-Free Copper-Catalysed Short-Chain Alkoxylation of Unactivated Aryl Bromides
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An efficient and practical short-chain alkoxylation of unactivated aryl bromides has been developed with special attention focussed on the applicability of the reaction. Sodium alkoxide is used as the nucleophile, and the corresponding alcohol as the solvent. The reaction requires neither precious metals nor organic ligands. It uses a catalytic system consisting of copper(I) bromide as a catalyst, the corresponding alkyl formate as a noncontaminating cocatalyst, and lithium chloride as an additive. A wide range of substrates and test cases highlight the synthetic utility of the approach. Considering the commercial accessibility and affordability of the feedstocks, this protocol shows promise as a new alternative for the sustainable preparation of aryl alkyl ethers.
- Guo, Ying,Fan, Xue-Min,Nie, Min,Liu, Hong-Wei,Liao, Dao-Hua,Pan, Xian-Dao,Ji, Ya-Fei
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p. 4744 - 4755
(2015/08/03)
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- SNAAP sulfonimidate alkylating agent for acids, alcohols, and phenols 1
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Stable, crystalline ethyl N-tert-butyl-4-nitrobenzenesulfonimidate has been prepared in high yield by direct O-ethylation of N-tert-butyl-4- nitrobenzenesulfonamide with iodoethane and silver(I) oxide in dichloromethane. This sulfonimidate directly ethylates various acids to esters; the stronger the acid, the faster it alkylates and in higher yield. It readily ethylates alcohols and phenols to ethers at room temperature in the presence of tetrafluoroboric acid catalyst without molecular rearrangements or racemization. We have defined these reactions as SNAAP alkylations: [substitution, nucleophilic of acids, alcohols and phenols]. The hard sulfonimidate alkylating agent is chemoselective, preferring oxygen > nitrogen > sulfur. The sulfonamide byproduct of alkylation is readily recycled to the sulfonimidate. Georg Thieme Verlag Stuttgart . New York.
- Maricich, Tom J.,Allan, Matthew J.,Kislin, Brett S.,Chen, Andrea I-T.,Meng, Fan-Chun,Bradford, Christine,Kuan, Nai-Chia,Wood, Jeremy,Aisagbonhi, Omonigho,Poste, Alethea,Wride, Dustin,Kim, Sylvia,Santos, Therese,Fimbres, Michael,Choi, Dianne,Elia, Haydi,Kaladjian, Joseph,Abou-Zahr, Ali,Mejia, Arturo
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p. 3361 - 3368
(2014/01/06)
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- Microwave-assisted alkylation of phenols by quaternary onium salts
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The alkylation of cresol and its analogues was accomplished by quaternary onium salts under solventless and microwave(MW) conditions using Cs 2CO3 as the base. The beneficial energy absorbing ability of the onium saltscould be clearly observed under MW conditions as compared to the thermal experiments and was relevant in the range of 110-125 °C.
- Blint, Erika,Greiner, Istvan,Keglevich, Gyrgy
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scheme or table
p. 22 - 27
(2012/04/10)
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- Bis(μ-iodo)bis[(-)-sparteine]-dicopper: A versatile catalyst for direct O-Arylation and O-Alkylation of phenols and aliphatic alcohols with haloarenes
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The easy to prepare dimeric bis(μ-iodo)bis[(-)-sparteine]- dicopper ([CuI{(-)-spa}]2 complex) is shown to be versatile catalyst for O-arylation and O-alkylation with various aryl halides with phenols and aliphatic alcohols respectively, including less reactive aryl chlorides, such as chlorobenzene under mild conditions.
- Satyanarayana, Ponnam,Maheswaran, Hariharasarma,Kantam, Mannepalli Lakshmi,Bhargava, Suresh
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supporting information; experimental part
p. 788 - 790
(2011/08/22)
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- Copper-catalyzed hydroxylation of aryl halides with tetrabutylammonium hydroxide: Synthesis of substituted phenols and alkyl aryl ethers
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The selective hydroxylation of aryl iodides and aryl bromides with tetrabutylammonium hydroxide pentahydrate is described. For this, the combination of copper(I) iodide and 8-hydroxyquinaldine at 70-130C in a mixture of dimethyl sulfoxide and water (2:3) is used. The resultant phenols can be readily reacted with alkyl and allyl halides in situ to provide the corresponding alkyl or allyl aryl ethers in high yields. The reactions are simple, general, and efficient, affording substituted phenols and alkyl aryl ethers under aerobic conditions
- Paul, Rajesh,Ali, Md Ashif,Punniyamurthy, Tharmalingam
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supporting information; experimental part
p. 4268 - 4272
(2011/02/25)
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- Formation and decomposition of diazo ethers under acidic conditions. Effects of ethanol concentration, acidity, and temperature on the ethanolysis of 4-methylbenzenediazonium ions
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We investigated the effects of solvent composition, acidity, and temperature on the dediazoniation of 4-methylbenzenediazonium (4MBD) ions in EtOH/H2O mixtures by employing a combination of spectrometric and chromatographic techniques. First-order behavior is found in all solvent composition ranges. HPLC Analyses of the reaction mixtures indicate that three main dediazoniation products are formed depending on the particular experimental conditions. These are 4-cresol (ArOH), 4-phenetole (ArOEt), and toluene (ArH). At acidities (defined as -log [HCl])a turnover in the reaction mechanism takes place under acidic conditions. At any given EtOH content, the plot of kobs values against acidity is S-shaped, the inflexion point depending upon the EtOH concentration and the temperature. Similar S-shaped variations are found when plotting the dediazoniation - product distribution against the acidity. The acid dependence of the switch between the homolytic and heterolytic mechanisms suggests that the homolytic dediazoniation proceeds via transient diazo ethers, and this complex kinetic behavior can be rationalized by assuming two competitive mechanisms: i) the spontaneous heterolytic dediazoniation of 4MBD, and ii) an O-coupling mechanism in which the EtOH molecules capture ArN 2+ to yield a highly unstable (Z)-adduct which undergoes homolytic fragmentation initiating a radical process (Scheme). Analyses of the effects of temperature on the equilibrium constant for the formation of the diazo ether and on the rate of splitting of the diazo ether allowed the estimation of relevant thermodynamic parameters for the formation of diazo ethers derived from methylbenzenediazonium ions under acidic conditions.
- Fernandez-Alonso, Alejandra,Bravo-Diaz, Carlos
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scheme or table
p. 877 - 887
(2010/08/06)
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- Heterogeneous phase alkylation of phenols making use of phase transfer catalysis and microwave irradiation
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The benzylation of cresol was studied under liquid-liquid and solid-liquid phase transfer catalytic conditions. Microwave irradiation was useful only in the solid-liquid phase benzylations. Using acetonitrile as the solvent, the benzylations were fully O-selective, but complete conversions were obtained only in the presence of Cs2CO3. There was no need to use an onium salt. In the absence of solvent, an O-selectivity of ca. 90% could be obtained in the presence of an alkali carbonate and an onium salt. The optimum set of conditions was extended to the reaction of other phenol derivatives and alkylating agents.
- Keglevich, Gyoergy,Balint, Erika,Karsai, Eva,Varga, Judit,Gruen, Alajos,Balint, Maria,Greiner, Istvan
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experimental part
p. 535 - 539
(2010/04/23)
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- Solvent-free Williamson synthesis: An efficient, simple, and convenient method for chemoselective etherification of phenols and bisphenols
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Etherification of phenols with dimethyl- and diethylsulfates and benzyl chloride was performed efficiently in the presence of a suitable solid base, NaHCO3 or K2CO3, under solvent-free conditions. The reaction proceeded rapidly at low temperature, and the corresponding ethers were obtained with high purity and excellent yield. Selective etherification of electron-poor phenols in the presence of electron-rich ones and also selective mono-etherification of bisphenols are the noteworthy advantages of this method. This method is environmentally friendly. Copyright Taylor & Francis Group, LLC.
- Massah, Ahmad R.,Mosharafian, Masumeh,Momeni, Ahamad R.,Aliyan, Hamid,Naghash, H. Javaherian,Adibnejad, Mohamad
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p. 1807 - 1815
(2008/02/02)
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- Organosoluble copper clusters as precatalysts for carbon - Heteroelement bond-forming reactions: Microwave and conventional heating
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(Chemical Equation Presented). The coupling of aryl iodides with alcohols under mild conditions has been explored using self-assembled octanuclear copper clusters as catalysts. Reactions involving tetrahydrofurfuryl alcohol were typically complete in 4-8
- Manbeck, Gerald F.,Lipman, Adam J.,Stockland Jr., Robert A.,Freidl, Adrienne L.,Hasler, Amy F.,Stone, Joshua J.,Guzei, Ilia A.
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p. 244 - 250
(2007/10/03)
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- Electrophilic reaction of nitric oxide with Wittig reagents
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Reaction of nitric oxide (NO) with p-substituted benzyl triphenylphosphonium chlorides or bromides (Wittig reagents) in CH 2Cl2 under argon undergoes electrophilic attack of NO on the carbon center of phosphonium ylides, producing be
- Liu, Zhongquan,Zhou, Bo,Liu, Zhongli,Wu, Longmin
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p. 1095 - 1097
(2007/10/03)
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- pH effects on ethanolysis of some arenediazonium ions: Evidence for homolytic dediazoniation proceeding through formation of transient diazo ethers
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The effects of pH on the observed rate constants (kobsd.) and on the solvolytic dediazoniation product distributions of ethanolysis of 2-, 3-, and 4-methylbenzenediazonium ions (2MBD, 3MBD, and 4MBD, respectively) were determined by a combination of spectrophotometric (UV/Vis) and Chromatographic (HPLC) techniques. The variation of both kobsd. and product yields with pH follow S-shaped curves with inflection points at pH ≈ 3.6, depending on solvent composition. With increasing pH, kobsd. values increase by factors of up to about 4 (2MBD), about 3 (3MBD), and about 50 (4MBD) with respect to the kobsd. values at low pH. HPLC analyses of the reaction mixtures show that only heterolytic products are obtained at low pH, indicating that solvolytic dediazoniation takes place through an ionic mechanism, but an increase in pH favors homolytic dediazoniation, with quantitative conversion into the reduction product toluene being obtained at pH ≥ 6 (4MBD), indicating that a turnover from the heterolytic to the homolytic mechanisms is taking place under experimental conditions under which insignificant amounts of EtO- or OH- should be present in solution. The obtained S-shaped profiles suggest that the initiation process of the homolytic pathway is the result of the formation of a highly unstable transient diazo ether complex and not by direct electron transfer from the solvent (EtOH) to the arenediazonium ions as is currently believed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Pazo-Llorente, Roman,Bravo-Diaz, Carlos,Gonzalez-Romero, Elisa
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p. 3221 - 3226
(2007/10/03)
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- Solvolysis of some arenediazonium salts in binary EtOH/H2O mixtures under acidic conditions
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We have determined the product distribution, the rate constants for dediazoniation product formation, and the solvolytic rate constants for 2-, 3-, and 4-methylbenzenediazonium ions (2-, 3-, and 4-MBD, respectively) loss in acidic ethanol/water mixtures over the whole composition range by a combination of spectrophotometric (UV/Vis) and high performance liquid chromatography (HPLC) measurements. The observed rate constants (kobs) for substrate loss are equal to those for product formation, and they remain essentially constant (2-MBD) with changing solvent composition but increase by a factor of ≈2 (4MBD) on going from water to 100% EtOH. Up to four dediazoniation products - cresols (ArOH), chlorotoluene (ArCl), methylphenetole (ArOEt), and toluene (ArH) - were detected, depending on the solvent composition; the major dediazoniation products were the ArOH and ArOEt derivatives. The product selectivity (S) of the reaction towards nucleophiles is low and essentially constant with changing solvent composition, and good linear correlations between log kobs and Yc1 (solvent ionizing power) were observed for the three ArN2+ ions. All data are consistent with the rate-determining formation of an aryl cation, which reacts immediately with available nucleophiles. The data suggest that the distribution of neutral and anionic nucleophiles in the neighborhood of the ground state arenediazonium ion remains essentially unchanged upon dediazoniation, the observed product distribution reflecting the concentrations of nucleophiles in their immediate environment (i.e., in the first solvation shells of the arenediazonium ions). Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Pazo-Llorente, Roman,Bravo-Diaz, Carlos,Gonzalez-Romero, Elisa
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p. 3421 - 3428
(2007/10/03)
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- A new phase transfer catalyst and its applications in organic transformations
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A new quaternary ammonium bromide salt has been used for the first time in phase transfer catalysis (PTC) reactions such as oxidation of alcohols to carbonyl compounds, alkylation and esterification reactions. Improved yields and reduced reaction times have been achieved by this procedure.
- Reddy, Ch. Venkateshwar,Mahesh,Raju,Reddy, V.V. Narayana
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p. 2797 - 2802
(2007/10/03)
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- Alkoxylated p-phenylenevinylene oligomers: Synthesis and spectroscopic and electrochemical properties
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Twenty-one n-alkoxy substituted phenylenevinylene oligomers were synthesized, varying in size, number and position of the OR groups. IR,MS and solubility data are presented. NMR measurements provided the molecular structure as well as information about conformations and molecular dynamics. UV and of cyclic voltammetric data give correlations of chemical structure (number and position of OR substituents) with separate HOMO and LUMO energies.
- Ndayikengurukiye, Henri,Jacobs, Sven,Tachelet, Wim,Van Der Looy, Johan,Pollaris, Anne,Geise, Herman J.,Claeys, Magda,Kauffmann, Jean M.,Janietz, Silvia
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p. 13811 - 13828
(2007/10/03)
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- A New Rearrangement of Alkoxybenzyl Anions
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Alkyl groups migrate from oxygen to carbon in alkyl aryl ethers which have been metalated in benzylic positions. 2,6-Dimethylanisole provides a variety of 2,6-dialkylphenols and their ethers in 45-80percent yields.Rearrangement products are obtained in 10-30percent yields from other dimethylanisoles and from methylanisoles.The reactions appear to proceed, like Wittig rearrangements, by homolytic cleavage of the alkyl-oxygen bond followed by recombination of the resulting radical pair in a different way.The rearrangements can be avoided by using methyl ethers and working at or below room temperature.
- Bates, Robert B.,Siahaan, Teruna J.,Suvannachut, Kessara
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p. 1328 - 1334
(2007/10/02)
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- Preparation and Reactions of Dianions from the Cresols
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With n-BuLi/KO-t-Bu, protons are removed from the hydroxyl and methyl groups of cresols 5 to give dianions 6 in yields of 85percent (ortho), 95percent (meta), and 42percent (para).These dianions react with alkyl halides, Me3SiCl, Bu3SnCl, CO2, and oxidizing agents at carbon only and with dialkyl sulfates at both carbon and oxygen.Thus phenol derivatives bearing primary alkyl groups can be prepared from the corresponding methylphenols via dianions 6.
- Bates, Robert B.,Siahaan, Teruna J.
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p. 1432 - 1434
(2007/10/02)
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- Aryl Radical Departure Aptitudes in Reactions of Diaryliodonium Fluoroborates with Sodium Ethoxide
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Several unsymmetrical diaryliodonium fluoroborates have been prepared and subjected to reaction with sodium ethoxide in ethanol solution at 71 deg C.From quantitative determinations of products, it has been possible to calculate apparent departure aptitudes of several common aryl radical cations of type 6.These results are compared with similar data obtained from thermolysis reactions of hydroxytetraarylstiboranes.
- Lubinkowski, Jacek J.,Arrieche, Cecilia Gimenez,McEwen, William E.
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p. 2076 - 2079
(2007/10/02)
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