- Characterization of novel Cs and K substituted phosphotungstic acid modified MCM-41 catalyst and its catalytic activity towards acetylation of aromatic alcohols
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TheMCM-41 supported Cs2.5H0.5PW12O 40 and K2.5H0.5PW12O40 salts were synthesized by incipient wetness impregnation method. The solids were characterized by N2 adsorption-desorption isotherms, FTIR, XRD, and temperature programmed desorption, etc. This catalyst has been found to exhibit excellent activity for acetylation of phenolic compounds. The catalyst is stable and reusable giving 96% conversion with 100% selectivity towards acetate products. Indian Academy of Sciences.
- Rana, Surjyakanta,Mallick, Sujata,Rath, Dharitri,Parida
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- Reductive removal of methoxyacetyl protective group using sodium borohydride
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Herein, we have developed a mild and selective reductive deprotection method for the MAc protected alcohols using sodium borohydride. The new deprotection conditions provide a complete orthogonality between O-MAc and other protecting groups such as tert-butyl ester, N-Boc, Fmoc, Cbz, O-TBDMS, N-benzyl, O-benzyl, O-acetyl, N-acetyl, N-MAc, etc. In addition to O-MAc deprotection, this method is also applicable for S-MAc deprotection.
- Gadekar, Pradip K.,Hoermann, Maryann,Corbo, Faith,Sharma, Rajiv,Sarveswari,Roychowdhury, Abhijit
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- Structure and Catalytic Mechanism of a Bacterial Friedel–Crafts Acylase
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C?C bond-forming reactions are key transformations for setting up the carbon frameworks of organic compounds. In this context, Friedel–Crafts acylation is commonly used for the synthesis of aryl ketones, which are common motifs in many fine chemicals and natural products. A bacterial multicomponent acyltransferase from Pseudomonas protegens (PpATase) catalyzes such Friedel–Crafts C-acylation of phenolic substrates in aqueous solution, reaching up to >99 % conversion without the need for CoA-activated reagents. We determined X-ray crystal structures of the native and ligand-bound complexes. This multimeric enzyme consists of three subunits: PhlA, PhlB, and PhlC, arranged in a Phl(A2C2)2B4 composition. The structure of a reaction intermediate obtained from crystals soaked with the natural substrate 1-(2,4,6-trihydroxyphenyl)ethanone together with site-directed mutagenesis studies revealed that only residues from the PhlC subunits are involved in the acyl transfer reaction, with Cys88 very likely playing a significant role during catalysis. These structural and mechanistic insights form the basis of further enzyme engineering efforts directed towards enhancing the substrate scope of this enzyme.
- Pavkov-Keller, Tea,Schmidt, Nina G.,??d?o-Dobrowolska, Anna,Kroutil, Wolfgang,Gruber, Karl
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- Doping of copper (I) oxide onto a solid support as a recyclable catalyst for acetylation of amines/alcohols/phenols and synthesis of trisubstituted imidazole
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A study of copper-mediated C-heteroatom especially C-N and C-O bond formations using simpler methodologies has been carried out. In the present work, acetylation of various substrates such as amines, phenols and alcohols; synthesis of 2,4,5-trisubstituted imidazole is done using simple and easily available starting materials. Copper (I) oxide was synthesized in situ by the reduction of Fehling's solution with glucose followed by its anchoring onto different supports like silica, HAP, basic alumina and cellulose. Comparison and contrasts between the reactivity of copper (I) oxide supported onto different supports for these reactions are made. The reactivity of copper (I) oxide seems to be largely dependent on the nature of support and the most active catalyst for a particular reaction was further characterized by different spectroscopic techniques such as FTIR, XRD, TGA, XPS, SEM, TEM and AAS. The catalysts were found to be stable, easily recyclable without any significant loss in activity. Graphical abstract: Applications of solid supported copper (I) oxides (where solid support is silica, HAP, cellulose and basic alumina) are studied for various organic transformations with special emphasis on C-N and C-O bond formation reactions.[Figure not available: see fulltext.]
- Gupta, Manjulla,Gupta, Monika
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- Biocatalytic Friedel–Crafts Acylation and Fries Reaction
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The Friedel–Crafts acylation is commonly used for the synthesis of aryl ketones, and a biocatalytic version, which may benefit from the chemo- and regioselectivity of enzymes, has not yet been introduced. Described here is a bacterial acyltransferase which can catalyze Friedel–Crafts C-acylation of phenolic substrates in buffer without the need of CoA-activated reagents. Conversions reach up to >99 %, and various C- or O-acyl donors, such as DAPG or isopropenyl acetate, are accepted by this enzyme. Furthermore the enzyme enables a Fries rearrangement-like reaction of resorcinol derivatives. These findings open an avenue for the development of alternative and selective C?C bond formation methods.
- Schmidt, Nina G.,Pavkov-Keller, Tea,Richter, Nina,Wiltschi, Birgit,Gruber, Karl,Kroutil, Wolfgang
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- Acyl Donors and Additives for the Biocatalytic Friedel–Crafts Acylation
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The Friedel–Crafts acylation is a broadly applied reaction that can be conducted using various types of catalyst. However, a biocatalytic alternative has only been reported recently. In this study, the scope of acetyl donors is described, showing that, in addition to vinyl acetate derivatives, phenyl esters are also suitable donors. Furthermore, it was found that various amines enhance the reaction, whereby the effect do not seem to be correlated to the pH but to the structure of the donor. For instance, 1,4-diazabicyclo[2.2.2]octane (DABCO) turned out to be a viable alternative to imidazole; however the former performed best at pH 9.85, whereas the latter performed best at pH 8.3.
- Schmidt, Nina G.,Kroutil, Wolfgang
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- Acylation of activated aromatics without added acid catalyst
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Phenol and resorcinol can be acetylated to the corresponding esters and ketones in aqueous and neat acetic acid at high temperature (250-300°C) to substantial equilibrium conversion without any added acid catalyst.
- Brown, James S.,Glaeser, Roger,Liotta, Charles L.,Eckert, Charles A.
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- Lipase PS-C catalysed hydrolysis of aryl diesters: A new route to the synthesis of achiral half esters
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Pseudomonas cepacia lipase supported on ceramic particles (PS-C) offers a simple alternative route for the synthesis of achiral half esters, with very high yields, easy work up and remarkable substrate selectivity, as it cleaves only phenolic esters having a phenyl group (i.e. C6H5-O-CO-C6H5).
- Nair, Ranjeet V.,Shukla, Manojkumar R.,Patil, Prashant N.,Salunkhe, Manikrao M.
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- Evaluation of 2-(piperidine-1-yl)-ethyl (PIP) as a protecting group for phenols: Stability to ortho-lithiation conditions and boiling concentrated hydrobromic acid, orthogonality with most common protecting group classes, and deprotection via Cope elimination or by mild Lewis acids
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A new protecting group, 2-(piperidine-1-yl)-ethyl (PIP), was evaluated as a protecting group for phenols. The PIP group was stable to ortho-lithiation conditions and refluxing with concentrated hydrobromic acid. Deprotection was accomplished by two routes, oxidation to N-oxides followed by Cope elimination (CE) and subsequent hydrolysis or ozonolysis of the vinyl ether or one-step deprotection by BBr3?Me2S. The PIP group is orthogonal to the O-benzyl, O-acetyl, O-t-butyldiphenylsilyl, O-methyl, O-p-methoxybenzyl, O-allyl, O-tetrahydropyranyl and N-t-butoxy carbonyl groups. The CE step was systematically studied and was found to give higher yields when the reaction was performed in the presence of silylating agents.
- Norén, Rolf
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- Gold(I)-Catalyzed Intramolecular Hydroarylation of Phenol-Derived Propiolates and Certain Related Ethers as a Route to Selectively Functionalized Coumarins and 2 H-Chromenes
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Methods are reported for the efficient assembly of a series of phenol-derived propiolates, including the parent system 56, and their Au(I)-catalyzed cyclization (intramolecular hydroarylation) to give the corresponding coumarins (e.g., 1). Simple syntheses of natural products such as ayapin (144) and scoparone (145) have been realized by such means, and the first of these subject to single-crystal X-ray analysis. A related process is described for the conversion of propargyl ethers such as 156 into the isomeric 2H-chromene precocene I (159), a naturally occurring inhibitor of juvenile hormone biosynthesis.
- Cervi, Aymeric,Vo, Yen,Chai, Christina L. L.,Banwell, Martin G.,Lan, Ping,Willis, Anthony C.
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p. 178 - 198
(2020/12/22)
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- Utilization of the inherent nucleophile for regioselective O-acylation of polyphenols via an intermolecular cooperative transesterification
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A green and efficient method for regioselective O-acylation of polyphenols has been developed. The acylation can be carried out in potassium carbonate/dimethyl sulphoxide system by utilizing the ‘inherent nucleophile’ via an intermolecular cooperative transesterification under mild condition. This method shows particular advantage in regioselective acylation of polyphenols bearing 2′,4′-dihydroxyacetophenone moiety and can be extended to the synthesis of mono or multiple acetates of polyphenols without this moiety in good yields. Compared with other reported approaches, this method is endowed with atom economy and is more environment-friendly for avoiding the use of any metal-based catalysts.
- Liu, Jingchao,Fu, Junjie,Li, Wenlong,Zou, Yu,Huang, Zhangjian,Xu, Jinyi,Peng, Sixun,Zhang, Yihua
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p. 4103 - 4110
(2016/07/06)
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- Rh-Catalyzed Synthesis of Coumarin Derivatives from Phenolic Acetates and Acrylates via C-H Bond Activation
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An efficient annulation strategy involving the reaction of phenolic acetates with acrylates in the presence of [Rh2(OAc)4] as catalyst and formic acid as reducing agent, leading to the high yield synthesis of coumarin derivatives, has been developed. The addition of NaOAc as a base increased the yield of the products. The reaction is quite successful for both electron-rich as well as electron-deficient phenolic acetates, affording coumarins with excellent regioselectivity, and proceeds via C-H bond activation proven by deuterium incorporation studies.
- Gadakh, Sunita K.,Dey, Soumen,Sudalai, Arumugam
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p. 11544 - 11550
(2015/12/04)
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- Silica-supported boric acid catalyzed synthesis of dihydropyrimidin-2-ones, bis(indolyl)methanes, esters and amides
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Silica-supported boric acid (H3BO3-SiO2) has been established as a green, efficient and recyclable catalyst for the synthesis of dihydropyrimidin-2-ones, bis(indolyl)methanes, and acetylation of alcohols, phenols, amines and thiols under solvent free conditions. The main features of the present method include clean reaction, mild conditions, low loading of environment friendly catalyst and easy workup procedure. The catalyst can be recycled at least five times without any significant loss in activity.
- Kumar, Vishal,Singh, Chitra,Sharma, Upendra,Verma, Praveen K.,Singh, Bikram,Kumar, Neeraj
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- Application of SO3H silica gel to deprotection of silyl ethers
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A newly developed SO3H silica gel cleaved the O-Si bonds in various aryl and alkyl silyl ethers to give the corresponding phenols and alcohols in good to excellent yield. The crude filtrates contained no silyl residues. The solid phase 29Si NMR analyses of the SO3H silica gel strongly suggested that the silyl residues were captured by silanol groups on the surface of the silica gel. The SO3H silica gel could be recycled at least ten times without any loss of activity. The disappearance of silyl residues in the crude filtrate was observed in even the 10th repetition. Our method provides an easily handled desilylation method that requires no further purification. Our method was also applicable to a selective desilylation reaction of a derivative 5 with different siloxy groups or desilylation of an alkaloid derivative 7.
- Fujii, Hideaki,Yamada, Takaaki,Hayashida, Kohei,Kuwada, Miki,Hamasaki, Atom,Nobuhara, Kazunori,Ozeki, Sumio,Nagase, Hiroshi
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p. 2685 - 2691
(2013/01/15)
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- HF-Pyridine: A versatile promoter for monoacylation/sulfonylation of phenolic diols and for direct conversion of t-butyldimethylsilyl ethers to the corresponding acetates
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Monoacylation and trifluoromethanesulfonylation of phenolic diols were achieved by the aid of HF-pyridine, whereas diacylation occurred with pyridine alone. Furthermore, HF-pyridine was found to promote the direct conversion of t-butyldimethylsilyl ethers to the corresponding acetates.
- Michigami, Kyosuke,Yoshimoto, Kazuya,Hayashi, Masahiko
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scheme or table
p. 138 - 139
(2012/03/09)
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- A mild and efficient method for the selective deprotection of silyl ethers using KF in the presence of tetraethylene glycol
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A mild and efficient protocol for the deprotection of silyl ethers using KF in tetraethylene glycol is reported. A wide range of alcoholic silyl ethers can be selectively cleaved in high yield in the presence of certain acid- and base-labile functional groups. Moreover, the phenolic silyl ethers were cleaved exclusively, without affecting the alcoholic silyl ethers, at room temperature. The Royal Society of Chemistry 2011.
- Yan, Hailong,Oh, Joong-Suk,Song, Choong Eui
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supporting information; experimental part
p. 8119 - 8121
(2012/01/04)
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- P-Toluenesulfonyl chloride as a new and effective catalyst for acetylation and formylation of hydroxyl compounds under mild conditions
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The catalytic application of p-toluenesulfonyl chloride for efficient acetylation of various types of alcohols and phenols with acetic anhydride in solvent-free conditions is reported. Also structurally diverse alcohols were formylated using formic acid based on the use of catalytic amount of p-toluenesulfonyl chloride under solvent-free condition. The reactions were carried out in short reaction time and in good to excellent yields at room temperature.
- Khazaei, Ardeshir,Rostami, Amin,Mantashlo, Fatemeh
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experimental part
p. 1430 - 1434
(2011/10/08)
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- Practical, environment-benign and atom economic KOAc-catalysed deprotection of aryl TIPS ethers under mild fluoride-free conditions
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A KOAc-catalysed, fluoride-free protocol not only effects chemoselective deprotection of phenolic TIPS ethers without affecting acetal, ketal, carbamate, O-acetyl and aliphatic silyl ethers, but also improves its atom economy by recycling the silanol byproduct.
- Wang, Bing,Sun, Hui-Xia,Chen, Bo,Sun, Zhi-Hua
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supporting information; experimental part
p. 1112 - 1114
(2010/04/23)
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- Encapsulated molecular catalysts in polysiloxane gels: Ruthenium cluster-catalyzed isomerization of alkenes
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Novel ruthenium-encapsulating polysiloxane gels are prepared by treatment of polymethylhydrosiloxane with diols in the presence of (μ3, η2,η3,η5-acenaphthylene)Ru 3(CO)7, and act as reusable catalysts in the isomerization of alkenes without leakage of the catalyst species. The Royal Society of Chemistry.
- Motoyama, Yukihiro,Abe, Motonori,Kamo, Kazuyuki,Kosako, Yusuke,Nagashima, Hideo
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supporting information; experimental part
p. 5321 - 5323
(2009/03/11)
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- Silica supported zinc chloride catalyzed acetylation of amines, alcohols and phenols
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Silica supported zinc chloride (SiO2-ZnCl2) has been prepared and found to efficiently catalyze the acetylation of amines, alcohols and phenols by stirring in acetonitrile at 80°C under heterogeneous conditions. The catalyst can be separated from the reaction medium simply by filtration and re-used up to four times.
- Gupta, Raman,Kumar, Vineet,Gupta, Monika,Paul, Satya,Gupta, Rajive
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experimental part
p. 1739 - 1743
(2009/06/28)
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- Mild debenzylation of aryl benzyl ether with BCl3 in the presence of pentamethylbenzene as a non-lewis-basic cation scavenger
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Scope and limitations of the debenzylation conditions for aryl benzyl ether, which was developed during our synthetic studies on yatakemycin, were investigated. The chemoselective debenzylation proceeds at low temperature with a combination of BCl3 and pentamethylbenzene as a cation scavenger in the presence of various functional groups.
- Okano, Kentaro,Okuyama, Kei-Ichiro,Fukuyama, Tohru,Tokuyama, Hidetoshi
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scheme or table
p. 1977 - 1980
(2009/04/07)
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- Co-catalyzed mild and chemoselective reduction of phenyl esters with NaBH4: a practical synthesis of (R)-tolterodine
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CoCl2 catalyzes effectively the chemoselective reduction of phenyl carboxylic esters to the corresponding saturated alcohols in high yields using NaBH4 at ambient conditions. By employing this methodology, the synthesis of (R)-tolterodine, a muscarinic receptor antagonist, has been achieved in high yield and optical purity.
- Jagdale, Arun R.,Sudalai, Arumugam
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p. 3790 - 3793
(2008/09/21)
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- PROCESS FOR THE PREPARATION OF 4-ALKYL RESORCINOL ESTERS
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A process for the preparation of one or more esters of 4-alkyl resorcinol comprising the steps of: (i) reacting resorcinol or a pre-cursor thereof with an esterifying agent which comprises at least one of an organic acid, anhydride or chloride having a maximum carbon chain length of 18, at a temperature of 10 to 250 °C; and (ii) reducing the products from step (i) at a pH of 6.5 to 7.5 in the presence of a catalyst in an alcoholic medium.
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- Process for the biocidal treatment of surface
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Process for the biocidal treatment of surfaces, by applying an aqueous biocidal composition containing a biocidal agent (B), a surfactant (SA) when the said biocide is hydrophobic, and at least one water-soluble or water-dispersible organic copolymer (C) comprising at least one oligomeric or macromolecular unit (D) which can interact with the said biocide or with the micelles of surfactant(s) containing the said biocide when it is hydrophobic, and at least one hydrophilic macromolecular unit (E) which can interact with the surface to be treated and optionally with the said biocide. Use of the copolymer (C) in a biocidal composition for the treatment of surfaces, as an agent for the vectorization and/or controlled release of the said biocide onto the surface to be treated.
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- Kinetic and spectroscopic characterization of ternary complexes by numerical fitting methods. Catalysis of acyl-transfer reactions by a macrocyclic azoniacyclophane
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Spectroscopic and computational procedures are presented for the analysis of highly complex kinetic schemes occurring in acyl-transfer reactions which are catalyzed by an azoniacyclophane (CP66). The results, supported by product identification and inhibition experiments, indicate an acyl transfer from intracavity-bound substrates such as 2,4-dinitronaphthyl acetate (DNNA) to hydroxybenzoic acids which are bound as cosubstrates to the positively charged CP66 by electrostatic association. The kinetic system is represented by 11 single steps, including the hydrolysis via a binary complex with CP66 and a side reaction to Meisenheimer products. Seven constants are determined by separate measurements with different techniques; three parameters for the ternary complex are then identified by curve fitting to the observed saturation kinetics. A newly developed numerical integration and optimization program allows the description of all parallel reaction parameters including fast equilibria.
- Schneider, Hans-J?rg,Kramer, Rüdiger,Rammo, J?rg
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p. 8980 - 8984
(2007/10/02)
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- HYDROXYLATION DIRECTE D'ESTERS DE PHENYLE ET D'ANILIDES PAR LE PEROXYDE D'HYDROGENE EN MILIEU SUPERACIDE
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In SbF5-HF, hydrogen peroxide reacts on the aromatic ring of esters 1a-5a and anilides 11a-15a to give monohydroxylated derivatives in good yields.With compounds 2a, 4a and 5a, meta or para isomers are by far the major products, whereas with formate 1a and benzoate 3a, the proportion of the ortho isomer is more important.With anilides, the reaction is less selective, the three isomers being obtained in comparable amounts.Thus, the relative proportions of ortho, meta and para-hydroxylated derivatives obtained using 70 percent H2O2 with acetate 2a and acetanilide 12a are 6/51/43 and 36.5/30/33.5, respectively.The important proportion of meta hydroxylation is the result of the reaction of protonated hydrogen peroxide H3O2+ on the protonated substrate.
- Berrier, Christian,Jacquesy, Jean-Claude,Jouannetaud, Marie-Paule,Morellet, Guy
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p. 158 - 164
(2007/10/02)
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- 2-Formylbenzenesulphonyl Chloride as a Reagent for the Protection of Phenols
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2-Formylbenzenesulphonate esters of phenols are rapidly cleaved by alkali leaving carboxylate esters untouched.
- Shashidhar, M. S.,Bhatt, M. Vivekananda
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p. 654 - 656
(2007/10/02)
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