- Towards ortho-selective electrophilic substitution/addition to phenolates in anhydrous solvents
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Alkyl-substituted Li-phenolates with BnBr in water solution lead to a mixture of o- and p-Bn-substituted phenols together with a substantial amount of phenol Bn ether. In CPME, and especially in toluene with 1–2 equivalents of ether or alcohol additives, ortho-selective alkylation is achieved. In the case of o,o,p-tri- and o,o-di-substituted phenols dearomatization occurs affording o-Bn-substituted alkyl cyclohexadienones with yields up to 92% with an o/p ratio up to 90/1.
- Lopu?anskaja, Eleana,Kooli, Anni,Paju, Anne,J?rving, Ivar,Lopp, Margus
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- Metal-Free C-O Bond Functionalization: Catalytic Intramolecular and Intermolecular Benzylation of Arenes
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A catalytic, metal-free intramolecular rearrangement of benzyl phenyl ethers using nitrosonium salt as a catalyst is described. The optimized reaction conditions enabled a catalytic and metal-free Friedel-Crafts alkylation reaction with benzylic alcohols, producing water as the stoichiometric byproduct. A comprehensive scope (>50 examples) for both approaches and application in drug synthesis were demonstrated. Mechanistic studies suggest a Lewis acid-based mechanism for the metal-free Friedel-Crafts reaction.
- Bering, Luis,Jeyakumar, Kirujan,Antonchick, Andrey P.
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supporting information
p. 3911 - 3914
(2018/07/22)
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- Protecting group-free use of alcohols as carbon electrophiles in atom efficient aluminium triflate-catalysed dehydrative nucleophilic displacement reactions
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Benzylic and allylic alcohols are rendered electrophilic without chemical modification by the use of aluminium triflate as catalyst. The reaction succeeds with alcohol, thiol, carbon and nitrogen nucleophiles. When phenols are employed as nucleophiles, C-alkylation ensues. An advanced application of the method is demonstrated in the synthesis of 2H-chromenes and their N and S analogues.
- Cullen, Adam,Muller, Alfred J.,Williams, D. Bradley G.
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p. 42168 - 42171
(2017/09/11)
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- Benzylation of aromatic compounds catalyzed by 3-methyl-1-sulfonic acid imidazolium tetrachloroaluminate and silica sulfuric acid under mild conditions
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In this work, efficient procedures for benzylation of a range of aromatic compounds by benzyl acetate in the presence of catalytic amounts of 3-methyl-1-sulfonic acid imidazolium tetrachloroaluminate ([Msim]AlCl 4) or silica sulfuric acid (SSA) under mild conditions are described. Simple methodology, easy workup procedure, clean reaction and reusability of the catalyst are some advantages of this work. Georg Thieme Verlag Stuttgart New York.
- Zolfigol, Mohammad Ali,Vahedi, Hooshang,Azimi, Saeid,Moosavi-Zare, Ahmad Reza
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p. 1113 - 1116
(2013/06/27)
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- Tin exchanged heteropoly tungstate: An efficient catalyst for benzylation of arenes with benzyl alcohol
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The partial exchange of tin with the protons of 12-tungstophosphoric acid (TPA) results in a highly active heterogeneous catalyst for benzylation of arenes with benzyl alcohol as benzylating agent. The catalysts were characterized by X-ray diffraction, Laser-Raman and FT-IR of pyridine adsorption. The catalytic activity depends significantly on the extent of tin exchanged with the protons of heteropoly tungstate. The characterization results suggest the presence of Lewis acidic sites by the exchange of tin. The catalyst with partial exchange of Sn showed high benzylation activity, which in turn related to variation in acidity of the catalysts. The catalyst is highly active for benzylation reaction irrespective of the nature of substituted arenes and benzyl alcohols. These catalysts are highly active compared to other acid catalysts used for benzylation of different arenes. The catalyst is easy to separate from reaction mixture and exhibit consistent activity upon reuse. The plausible reaction mechanism based on the role of both Lewis and Bronsted acid sites of the catalyst was discussed.
- Ramesh Kumar, Ch.,Rao, K.T. Venkateswara,Sai Prasad,Lingaiah
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experimental part
p. 17 - 24
(2011/04/21)
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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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- Chemoselectivity in the microwave-assisted solvent-free solid-liquid phase benzylation of phenols: O- versus C-alkylation
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The outcome of the solvent-free benzylation of phenol and 4-substituted phenols (such as 4-cresol and 4-chlorophenol) under MW irradiation was found to depend on the absence or presence of the base (K2CO3) and catalyst (triethylbenzy
- Keglevich, Gy?rgy,Bálint, Erika,Karsai, éva,Grün, Alajos,Bálint, Mária,Greiner, István
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p. 5039 - 5042
(2008/12/22)
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- Zirconia-modified superacid UDCaT-5: An efficient and versatile catalyst for alkylation reactions under solvent-free conditions
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UDCaT-5, a modified version of zirconia, efficiently catalyzes alkylation of phenols with alcohols under environmentally safe, heterogeneous reaction conditions with high selectivity and in excellent yields. The high content present in UDCaT-5 with preservation of tetragonal phase of zirconia was responsible for the superactivity. Several phenolic compounds carrying either electron-sulfer releasing or electron-withdrawing substituents in the ortho, meta, and para positions afforded high yields of the products. Copyright Taylor & Francis Group, LLC.
- Yadav, Ganapati D.,Pathre, Ganesh S.
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p. 2684 - 2691
(2008/12/22)
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- Molecular iodine-catalyzed benzylation of arenes with benzyl alcohols
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A novel molecular iodine-catalyzed benzylation of arenes with benzyl alcohols has been developed. The reaction can be carried out under mild conditions to afford a series of diarymethane derivatives in high yields and good regioselectivities.
- Sun, Gaojun,Wang, Zhiyong
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p. 4929 - 4932
(2008/09/21)
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- Efficient and selective alkylation of arenes and heteroarenes with benzyl and allyl ethers using a Ir/Sn bimetallic catalyst
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A high-valent heterobimetallic catalyst namely [Ir2(COD)2(SnCl3)2(Cl)2(μ-Cl)2] (5 mol %), or dual catalyst system of [Ir(COD)Cl]2 (1 mol %) and SnCl4 (4 mol %), promotes the benzylation or allylation of arenes and heteroarenes using ethers as the alkylating agents. An electrophilic mechanism is proposed from a Hammett correlation.
- Podder, Susmita,Roy, Sujit
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p. 9146 - 9152
(2008/02/09)
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- Ionic liquids as reagent and reaction medium: Preparation of alkyl aryl ethers
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Room temperature ionic liquid, [bmIm]OH, is used as a green recyclable reaction medium and reagent for the alkylation of phenols in excellent yields. The recovered ionic liquid was reused five to six times with consistent activity.
- Mohanazadeh, Farajollah,Aghvami, Majid
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- METHOD FOR PRODUCING 2-BENZYLPHENOL COMPOUND
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[Task] Provide a process for producing a 2-benzylphenol compound easily, efficiently and selectively. [Means for Achievement] A process for producing a 2-benzylphenol compound represented by the following general formula (2) (in the formula, R1, R2, R3 and R4 may be the same or different and are each independently hydrogen atom, alkyl group or the like; and R5, R6, R7, R8 and R9 may be the same or different and are each independently hydrogen atom, alkyl group or the like), characterized by reacting, in the presence of a dehydrogenating agent, a benzylidenecyclohexanone compound represented by the following general formula (1) (in the formula, R1, R2, R3, R4, R5, R6, R7, R8 and R9 have the same definitions as given above). [Effect] A 2-benzylphenol compound substantially free from isomers can be produced from a benzylidenecyclohexanone compound (an easily obtainable raw material) selectively, efficiently and in a simple operation, under mild conditions without using any special reactor.
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- METHOD FOR PRODUCING 2-BENZYLPHENOL COMPOUND
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Disclosed is a simple method for efficiently and selectively producing a 2-benzylphenol compound. Specifically disclosed is a method for producing a 2-benzylphenol compound represented by the following general formula (2): (wherein R1, R2, R3, R4, R5, R6, R7, R8 and R9 represent the same as defined in the general formula (1) below) which is characterized by reacting a benzylidenecyclohexane compound represented by the following general formula (1): (wherein R1, R2, R3 and R4 may be the same or different and respectively represent a hydrogen atom, an alkyl group or the like; and R5, R6, R7, R8 and R9 may be the same or different and respectively represent a hydrogen atom, an alkyl group or the like) in the presence of a dehydrogenation agent. Consequently, a 2-benzylphenol compound substantially containing no isomers can be produced selectively and efficiently under mild conditions by a simple procedure using an easily-available benzylidenecyclohexane compound as the raw material without requiring a special reaction equipment.
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Page/Page column 35
(2008/06/13)
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- BENZYLPHENOL DERIVATIVES AS ANTIOXIDANTS FOR AUTOXIDATION OF TETRALIN.
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A series of 4-benzylphenols, 2-methyl-4-benzylphenols, 4-methyl-2-benzylphenols and 4-methoxy-2-benzylphenols have been prepared and evaluated as antioxidants for tetralin at 60 degree C by means of an oxygen-absorption method. Very good activities have been observed with a series of 4-methoxy-2-benzylphenols. The electrochemical oxidation potentials of these compounds were determined using linear-sweep voltammetry. The antioxidative activities were found to correlate with both the **1**3C NMR chemical shifts ( delta ) of the ipsocarbon of the OH substituents and their peak potentials (E//p).
- Yamada,Nishiyama,Suzuura,Yamamura
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p. 115 - 119
(2007/10/02)
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- MECHANISMUS DER PHOTO-UMLAGERUNG VON BENZYLARYLETHERN
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Aus Absorptions- and Emissionsspektren konnten die ES- and ET-Werte einiger Benzylarylether bestimmt werden.Die Photo-Claisen-Umlagerung dieser Ether erfolgt aus dem S1-Zustand, wie durch Sensibilisierungs- and Loeschexperimente mit aromatischen Kohlenwasserstoffen bzw.Diacetyl bewiesen wurde.Bei der Photolyse werden primaer Benzyl- und Phenoxyradikale gebildet, deren Entstehen durch Spin-Trapping-Experimente bewiesen wurde.Die Spaltung der Ether geschieht mit hohen Quantenausbeuten, die wenig von Substituenten sowohl im Phenoxy- als auch im Benzylteil der Ether beeinflusst werden.In protischen Loesungsmitteln steigen die Werte geringfuegig an.Die Quantenausbeuten fuer die Reaktionsprodukte wurden ebenfalls bestimmt; deren Summe ergibt die Groesse fuer den Etherabbau.Die Produktverteilung bei der Photolyse einiger p-substituierter Ether legt nahe, dass die Benzylradikale auch in p-Stellung der Phenoxyradikale angreifen.Es wird ein allgemeiner Mechanismus diskutiert and kinetisch modelliert.Dadurch werden die Geschwindigkeitskonstanten einiger Teilschritte zugaenglich und wahrscheinlich gemacht, dass die Radikale auch zum Ether rekombinieren.
- Timpe, Hans-Joachim,Dietrich, Reinhard,Boeckelmann, Juergen,Friedel, Ingrid,Boegel, Horst,Haucke, Guenther
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p. 219 - 239
(2007/10/02)
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