- Generation and hetero-Diels-Alder reactions of an o-quinone methide under mild, anionic conditions: Rapid synthesis of mono-benzannelated spiroketals
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Deprotonation of o-hydroxybenzyl acetate with iPrMgCl provides a method of generating an o-quinone methide under mild, anionic conditions, such that highly sensitive exo-enol ethers can be employed as 2π partners in hetero-Diels-Alder reactions
- Bray, Christopher D.
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- Lipase-mediated selective acetylation of primary alcohols in ethyl acetate
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An environmental friendly process to selectively acetylate primary alcohols was demonstrated. The esterification process consists of treatment of a primary alcohol in the presence of immobilized C. antarctica lipase (Novozyme-435) in ethyl acetate at room temperature. Primary alcohols were acetylated in the presence of secondary alcohols and phenols.
- de Souza, Ernane C.,Romero-Ortega, Moises,Olivo, Horacio F.
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supporting information
p. 287 - 290
(2017/12/29)
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- Efficient and selective N-, S- and O-acetylation in TEAA ionic liquid as green solvent. Applications in synthetic carbohydrate chemistry
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Background: The ionic liquid triethylammonium acetate (TEAA) was found to be an efficient solvent in the acetylation of alcohols, amines, oximes and thiols to their corresponding acetyl compounds using only a 10% excess of acetic anhydride under mild conditions. Moreover TEAA is not only an inexpensive and recyclable solvent but also an anomeric selective catalyst in the per-O-acetylation of sugar moieties. Methods: Simple and effective organic synthesis protocols were provided for the selective acetylation of several substrates. The products were fully characterized by 1H and 13C NMR spectroscopy and the anomeric ratios were obtained from the 1H spectra. Results: Structurally diverse alcohols, phenols, thiols, amines, carbohydrates and oximes underwent acylation under mild conditions by this procedure to provide the corresponding acetates in excellent yields. TEAA ionic liquid is unique in its capability to act as both, solvent and high selective catalyst. As expected, the reaction proceeds with high b anomeric selectivity for sugars derivatives. Moreover, the ionic liquid was regenerated, recycled and reused for three times without apparent loss of reactivity and selectivity in all cases. Conclusions: The present procedure provides a powerful and versatile acylation method for alcohols, phenols, thiols, amines, oximes and carbohydrates. This protocol is endowed with several unique merits: selectivity, cost-efficiency, atom-economy and mild reaction conditions tolerable to acid sensitive functionalities. With these features, this method may be considered as a better alternative for the acetylation of a wide range of substrates.
- Lafuente, Leticia,Díaz, Gisela,Bravo, Rodolfo,Ponzinibbio, Agustín
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p. 195 - 200
(2016/02/26)
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- Copper(I)-catalyzed hydroalkoxylation/hydrogen-bonding-induced asymmetric hetero-diels-alder cycloaddition cascade: An approach to aromatic spiroketals
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One thing leads to another: Bis(benzannelated) 5,6-spiroketal skeletons can be constructed by an efficient cascade process involving an unprecedented CuI-catalyzed intramolecular alkyne hydroalkoxylation and an asymmetric hetero-Diels-Alder cyc
- Li, Xin,Xue, Jijun,Huang, Chusheng,Li, Ying
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supporting information; experimental part
p. 903 - 906
(2012/07/03)
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- Solvent free, highly chemoselective N and O-acylation on silica and silica magnesium oxide: A recyclable solid surface
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Silica or silica/magnesium oxide mixed surface mediates the N and O-acylation, benzoylation or sulfonylation of hosts of substrates under solvent free conditions at ambient temperature with high chemoselectivity.
- Ghosh, Pranab,Mandal, Amitava
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p. 261 - 268
(2012/10/29)
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- A green method for selective acetylation of primary alcohols using ethyl acetate and solid potassium carbonate
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A simple and selective acetylation of primary alcohols in the presence of other reactive functionalities such as secondary alcohol, phenol, acetonide and amine is described using mild ethyl acetate as the acetyl-transfer agent and solid potassium carbonate as the catalyst.
- Mallesha,Rao, S. Prahlada,Suhas,Gowda, D. Channe
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experimental part
p. 536 - 539
(2011/11/30)
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- Microwave-assisted rapid and efficient deprotection and direct esterification and silylation of MOM and EOM ethers catalyzed by [Hmim][HSO 4] as a Bronsted acidic ionic liquid
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1-Methylimidazolium hydrogensulfate, [Hmim] [HSO4], a Bronsted acidic room temperature ionic liquid, is used as a catalyst and reaction medium for facile and ecofriendly deprotection of methoxymethyl (MOM) and ethoxymethyl (EOM) ethers to their corresponding alcohols under thermal conditions (Δ) and microwave irradiation (MW). Furthermore, one-pot interconversion to the respective acetates and trimethylsilyl (TMS) ethers was also achieved. Springer-Verlag 2010.
- Mohammadpoor-Baltork, Iraj,Moghadam, Majid,Tangestaninejad, Shahram,Mirkhani, Valiollah,Khosropour, Ahmad Reza,Mirjafari, Arsalan
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experimental part
p. 1083 - 1088
(2012/06/18)
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- An approach to benzannelated [5,6]-spiroketals
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Heating a variety of 2-hydroxybenzyl acetates bearing a range functional groups on the 4- or 5-position of the aromatic ring at 100°C in neat γ-methylene-γ-butyrolactone (1.0 M) for 20 hours gives a series of benzannelated [5,6]-spiroketals in 75-89% yiel
- Bray, Christopher D.
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body text
p. 2500 - 2502
(2009/04/11)
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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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- Selective acetylation of alcohols and amines with ethyl acetate in the presence of H6[PMo9V3O40] as the catalyst
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Acetylation of various alcohols and benzyl amine was tested in the presence of H6[PMo9V3O40], a mixed addenda heteropolyacid, in ethyl acetate under reflux condition. Phenols and anilines are not affected under the reaction conditions. Selective transestrification of alcohols can be achieved in the presence of phenol and aniline derivatives using this method. Springer-Verlag 2007.
- Heravi, Majid M.,Bakhtiari, Khadijeh,Javadi, Negar M.,Oskooie, Hossein A.,Bamoharram, Fatemeh F.
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p. 445 - 447
(2008/02/02)
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- Expeditious synthesis of the aromatic spiroketal skeleton using hetero-Diels-Alder cycloaddition
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The hetero-Diels-Alder reactions of enolic ethers generated from methylenation of various esters are described, which allow for the rapid synthesis of various substituted [6,6] aromatic spiroketal skeletons.
- Zhou, Guanglian,Zheng, Deping,Da, Shijun,Xie, Zhixiang,Li, Ying
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p. 3349 - 3352
(2007/10/03)
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- Transformation of primary benzyl amines to benzyl esters
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Primary benzyl amines, upon treatment with aq. NaNO2 and appropriate organic acids at 0-5°C, give their respective benzyl esters. Copyright Taylor & Francis, Inc.
- Naik, Ramesh,Pasha
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p. 2823 - 2826
(2007/10/03)
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- The regioselective synthesis of monomethoxynaphthylene diacetates
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Methods for the conversion of 1,4,5-naphthalenetriols into the corresponding monomethoxy diacetates are described. All utilise the formation of peri-bridged intermediates.
- Maiti, Bhim C.,Musgrave, Oliver C.,Skoyles, Douglas
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p. 1765 - 1771
(2007/10/03)
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- A new and efficient method for o-quinone methide intermediate generation: Application to the biomimetic synthesis of the benzopyran derived natural products (±)-lucidene and (±)-alboatrin
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Lucidene and alboatrin are complex benzopyran derived natural products. A key step in their biogenesis may involve a hetero Diels-Alder cycloaddition between an o-quinone methide intermediate with a simple, or activated tri-substituted olefin. Experimental evidence is provided to support this hypothesis, with the biomimetic synthesis of both (±)-lucidene and (±)-alboatrin successfully achieved using a new and efficient method for o-quinone methide generation. The Royal Society of Chemistry 2005.
- Rodriguez, Raphael,Moses, John E.,Adlington, Robert M.,Baldwin, Jack E.
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p. 3488 - 3495
(2007/10/03)
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- A new and efficient method for o-quinone methide intermediate generation: Application to the biomimetic synthesis of (±)-Alboatrin
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(Chemical Equation Presented) A new and efficient method for o-quinone methide intermediate generation from o-methyleneacetoxy-phenols has been developed and applied to the biomimetic synthesis of (±)-Alboatrin.
- Rodriguez, Raphael,Adlington, Robert M.,Moses, John E.,Cowley, Andrew,Baldwin, Jack E.
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p. 3617 - 3619
(2007/10/03)
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- Lewis acid catalyzed acylation reactions: Scope and limitations
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Acylation of alcohols, thiols, and sugars were studied with a variety of Lewis acids, and it was found that Cu- and Sn(OTf)2 are very efficient in catalyzing the reaction under mild conditions. Among these two catalysts, Cu(OTf)2 was preferred because of its lower cost and relatively higher yield of the acylated product. The reaction was studied in several solvents, but CH2Cl2 was preferred. It was also observed that the present method is suitable for acylation of tertiary alcohols. Sugars were also acylated without any epimerization at the anomeric center. It is further shown here that this method is also suitable for selective acylation of primary or secondary alcohols over tertiary ones.
- Chandra, Kusum L,Saravanan,Singh, Rajesh K,Singh, Vinod K
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p. 1369 - 1374
(2007/10/03)
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- Sulfurated borohydride exchange resin: Reductive cleavage of aryl acetates under mild conditions
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A variety of aryl acetates are selectively cleaved to the corresponding phenols using sulfurated borohydride exchange resin in methanol at 25°C. Other sensitive groups present elsewhere in the molecule remain unaltered under these reaction conditions.
- Bandgar,Kamble
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- Enzyme-catalyzed chemoselective transesterification reactions on hydroxymethylated phenolic compounds
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The chemoselective capabilities of porcine pancreatic lipase (PPL) in tetrahydrofuran and Candida rugosa lipase (CRL) in diisopropyl ether have been investigated for selective acetylation and deacetylation of hydroxymethylated phenols and hydroxyaryl alky
- Parmar, Virinder S.,Prasad, Ashok K.,Pati, Hari N.,Kumar, Rajesh,Azim, Abul,Roy, Sucharita,Errington, William
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p. 119 - 134
(2007/10/03)
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- Lipase-catalysed chemoselective monoacetylation of hydroxyalkylphenols and chemoselective removal of a single acetyl group from their diacetates
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It was demonstrated that Pseudomonas cepacia PS lipase adsorbed on Celite, has the ability to catalyse the chemoselective monoacetylation of various hydroxyalkylphenols or the chemoselective removal of a single acetyl group from the corresponding acetate.
- Allevi, Pietro,Ciuffreda, Pierangela,Longo, Alessandra,Anastasia, Mario
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p. 2915 - 2924
(2007/10/03)
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- Regio- and Chemo-selective Properties of Lipase from Candida cylindracea
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Lipase from Candida cylindracea allows discrimination between the two connectively non-equivalent hydroxy groups in primary diols or their esters via acylation-hydrolysis, with high regioselectivity.The same technique is used to distinguish between hydroxy groups of different nature in phenolic compounds.
- Pedrocchi-Fantoni, Giuseppe,Servi, Stefano
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p. 1029 - 1034
(2007/10/02)
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- Photocyclisations de cetoacetals aromatiques en vue d'une approche synthetique de la crombenine
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Combenin 1 is a spiropeltogynoid compound with a spiroacetal moiety.A similar structure was synthesized starting from and orthocarbonylphenoxyisochroman by a Norrish type II photocyclisation.With an isochroman compound, the aromatic ring induces benzyl ra
- Cottet, Francoise,Cottier, Louis,Descotes, Gerard
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p. 1251 - 1257
(2007/10/02)
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- PROTECTION DES PHENOLS PAR LE GROUPEMENT AZIDOMETHYLENE APPLICATION A LA SYNTHESE DE PHENOLS INSTABLES
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Phenols are protected by the azidomethylene group in basic, nucleophilic, oxidative, weakly reductive and weakly acidic media.This group is obtained by the reaction of sodium azide with aryloxymethyl chlorides.Its utility lies in the ease with which it can be removed under very mild conditions which allows the synthesis of very unstable phenolic compounds.
- Loubinoux, Bernard,Tabbache, Samir,Gerardin, Philippe,Miazimbakana, Joseph
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p. 6055 - 6064
(2007/10/02)
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