- An Intramolecular Iodine-Catalyzed C(sp3)?H Oxidation as a Versatile Tool for the Synthesis of Tetrahydrofurans
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The formation of ubiquitous occurring tetrahydrofuran patterns has been extensively investigated in the 1960s as it was one of the first examples of a non-directed remote C?H activation. These approaches suffer from the use of toxic transition metals in overstoichiometric amounts. An attractive metal-free solution for transforming carbon-hydrogen bonds into carbon-oxygen bonds lies in applying economically and ecologically favorable iodine reagents. The presented method involves an intertwined catalytic cycle of a radical chain reaction and an iodine(I/III) redox couple by selectively activating a remote C(sp3)?H bond under visible-light irradiation. The reaction proceeds under mild reaction conditions, is operationally simple and tolerates many functional groups giving fast and easy access to different substituted tetrahydrofurans.
- Br?se, Stefan,Koch, Vanessa
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supporting information
p. 3478 - 3483
(2021/07/22)
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- Phosphotungstic Acid Supported on Magnetic Mesoporous Tantalum Pentoxide Microspheres: Efficient Heterogeneous Catalysts for Acetalization of Benzaldehyde with Ethylene Glycol
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Abstract: In this study, magnetically-recoverable core–shell catalysts with different amount of H3PW12O40 loading [Fe3O4@C@mTa2O5-NH2-PW12 (w%)] were prepared by the application of phosphotungstic acid supported on amino group functionalized magnetic core–shell mesoporous tantalum pentoxide microspheres. The prepared samples were characterized by FT-IR, N2-adsorption–desorption isotherms, TEM, SEM, Pyridine-IR analysis, XRD and magnetism. Fe3O4@C@mTa2O5-NH2-PW12 samples present both Br?nsted and Lewis acidity, large BET surface area and high magnetization. The catalytic activity was evaluated by the acetalization of different aldehydes with diols, and the results show that Fe3O4@C@mTa2O5-NH2-PW12 (14.47%) catalyst exhibits the highest catalytic activity for acetalization of aldehydes with glycols with 94.5% conversion of benzaldehyde and 99% selectivity to benzaldehyde glycol acetal at 80?°C. The catalytic activity of the catalyst for acetalization is related to its total acidity and Br?nsted–Lewis acid synergy. The catalyst Fe3O4@C@mTa2O5-NH2-PW12 can be easily recovered and reused for at least 5 times without obvious decrease of catalytic activity.
- Feng, Caiting,Li, Qinlong,Wu, Panfeng,Liu, Bin,Hu, Huaiming,Xue, Ganglin
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p. 1204 - 1217
(2019/11/19)
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- Direct anodic (thio)acetalization of aldehydes with alcohols (thiols) under neutral conditions, and computational insight into the electrochemical formation of the acetals
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A versatile protocol for the production of acetals/thioacetals by means of direct electrochemical oxidation is developed here under neutral conditions, providing (thio)acetals with good functional group tolerance and a wide scope for both aldehydes and (thio)alcohols. DFT calculations reveal that direct electron transfer from the anode plays a key role in carbonyl activation during this acid free acetalization process.
- Liu, Caiyan,Shen, Yongli,Xiao, Zihui,Yang, Hui,Han, Xue,Yuan, Kedong,Ding, Yi
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p. 4030 - 4034
(2019/08/07)
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- A Direct Method for the Efficient Synthesis of Benzylidene Acetal at Room Temperature
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For the first time, a metal-free direct method has been developed for the efficient synthesis of benzylidene acetal at room temperature using Dowex 50WX8 as a solid acid catalyst and Cl3CCN as a novel water scavenger. At room temperature, a wide variety of aryl and α,β-unsaturated aldehydes react readily with functionalized 1,2- and 1,3-diols to furnish the corresponding acetals in very good yields. Labile functional groups, like N-Boc, N-Cbz, -OTBDMS, -OBn, -N3 and acetonide are found to be stable under the reaction conditions. The versatility of this method is further demonstrated with carbohydrate substrates and optically active diols.
- Reddy, Narra Rajashekar,Kumar, Rashmi,Baskaran, Sundarababu
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supporting information
p. 1548 - 1552
(2019/01/09)
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- Robust acidic pseudo-ionic liquid catalyst with self-separation ability for esterification and acetalization
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The novel acidic pseudo-ionic liquid catalyst with self-separation ability has been synthesized through the quaternization of triphenylphosphine and the acidification with silicotungstic acid. The pseudo-IL showed high activities for the esterification with average conversions over 90%. The pseudo-IL showed even higher activities for acetalization than traditional sulfuric acid. The homogeneous catalytic process benefited the mass transfer efficiency. The pseudo-IL separated from the reaction mixture automatically after reactions, which was superior to other IL catalysts. The high catalytic activities, easy reusability and high stability were the key properties of the novel catalyst, which hold great potential for green chemical processes.
- Shi, Yingxia,Liang, Xuezheng
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p. 1413 - 1421
(2019/05/04)
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- Ce(III)-Based frameworks: From 1d chain to 3d porous metal-organic framework
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The reaction of pyridine-2,4-dicarboxylic acid (2,4-H2 pydc) with Ce(NO3)36H2O, by applying only minor changes to the reaction conditions, generated a series of new one-, two-, and three-dimensional (1D, 2D, and 3D) coordination polymers, namely, [Ce(pydc)(Hpydc)(H2O)4]n (1), [Ce(pydc)(Hpydc)(H2O)2]n (2), and {[Ce3(pydc)4(H2O)2NO3]4H2O}n (3). The ancillary ligand interaction as well as the reaction conditions determine the specific coordination modes for the Hpydc- and pydc2- ligands and, in turn, discriminate between 1D, 2D, and 3D frameworks. Characterization of the prepared materials was performed using single-crystal and powder X-ray diffraction analysis, Fourier transform infrared spectroscopy, CHN elemental analysis, thermogravimetric analysis, and nitrogen adsorption/desorption techniques. Compound 1 consists of 1D chains, that compose of Ce3+ ions bridged by Hpydc- and pydc2- ligands, which further link via noncovalent interactions to form a 3D supramolecular architecture. Compound 2 assembles into 2D sheets with 1D channels. Similarly, via hydrogen-bonding interactions between two adjacent sheets, the 2D layers are further stacked into the final 3D supramolecular structure. Compound 3 is a 3D metal-organic framework (MOF), showing 1D helical channels. The progressive skeletal variation from the 1D chains (1) to 2D sheets (2) and 3D framework (3) is attributed to the flexibility of both the Ce(III) coordination sphere and coordination modes of the Hpydc- and pydc2- ligands under different reaction conditions. The three compounds illustrate how the tuning of the coordination geometry of Ce(III) translates into different dimensionality, which is readily influenced by reaction temperature and ancillary ligand presence. Moreover, the porosity of MOF 3 was confirmed by N2 and CO2 gas adsorption/desorption. Finally, the catalytic activity of MOF 3 was examined in acetalization reactions in a series of aromatic aldehydes with methanol.
- Derakhshandeh, Parviz Gohari,Abednatanzi, Sara,Leus, Karen,Janczak, Jan,Van Deun, Rik,Van Der Voort, Pascal,Van Hecke, Kristof
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p. 7096 - 7105
(2019/11/19)
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- House bulb light-induced photochemical acetalization of carbonyl compounds catalyzed by Eosin Y
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We have systematically studied the reactions of acetalization and found that high reaction efficiency can be achieved using cheap and readily available organic Eosin Y as catalyst. The reaction proceeds smoothly under house bulbs and shows excellent functional group tolerance. The substrates of the reaction system are compatible with aromatic aldehydes, aliphatic aldehydes, aromatic ketones, and cyclic ketones with high yields.
- Zhou, Quan,Jia, Tao,Li, Xiao-Xuan,Zhou, Lin,Li, Chang-Jiang,Feng, Yi-Si
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supporting information
p. 1068 - 1075
(2018/05/23)
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- A containing-SO 3 H acidic magnetic material catalytic preparing acetal (ketone) method
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The invention discloses a method for preparing acetal (ketone) by catalyzing an acidic magnetic material containing -SO3H, which belongs to the technical field of chemical material and preparation thereof. According to the invention, mol ratio of aldehyde or ketone to alcohol used in the preparation method is 1: (1-5), mole of the acidic magnetic material catalyst accounts for 8-10% of that of the used aldehyde or ketone by calculating -SO3H, reaction temperature is 110 DEG C, the reaction time is 0.5-3 hours, the reaction pressure is one atmospheric pressure, a cooling step is carried out to room temperature after reaction is completed, the catalyst is sucked by a magnet, and the conversion rate, selectivity and acetal(ketone) yield of the reaction raw material are detected by a reaction solution through a gas chromatograph. Compared with the preparation method of other catalysts, the method has the advantages of high reaction selectivity, simple separation of the catalyst and the product, the catalyst enables cycle usage without any treatment, the operation of whole preparation process is simple, the economic benefit is high, and the method is convenient for industrial large scale production.
- -
-
Paragraph 0024
(2017/03/08)
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- Acetals from primary alcohols with the use of tridentate proton responsive phosphinepyridonate iridium catalysts
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The association of the new phosphinepyridonate ligands along with an iridium metallic precursor resulted in the selective acetalization of various primary alcohols via a formal dehydrogenative coupling reaction.
- Sahoo,Jiang,Bruneau,Sharma,Suresh,Achard
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p. 100554 - 100558
(2016/11/09)
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- Graphene-catalyzed transacetalization under acid-free conditions
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1,2- and 1,3-Diols are readily protected as cyclic acetals and ketals through a graphene-catalyzed transacetalization process. The methodology features an atom economic procedure since quasi-stoichiometric conditions have been developed. Unlike prior systems, the graphene-catalyzed transacetalization is performed under Br?nsted and Lewis acid-free conditions and without solvent. Our method has been applied to several volatile compounds that are unsuitable for complex work-up and extensive purification steps. The very unusual catalytic properties of graphene for transacetalization reactions are ascribed to molecular charge transfer between graphene and substrates.
- Nongbe, Medy C.,Oger, Nicolas,Ekou, Tchirioua,Ekou, Lynda,Yao, Benjamin K.,Le Grognec, Erwan,Felpin, Fran?ois-Xavier
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p. 4637 - 4639
(2016/09/23)
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- Cyclopentyl methyl ether-NH4X: A novel solvent/catalyst system for low impact acetalization reactions
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Cyclopentyl methyl ether, a low impact ether forming a positive azeotrope with water, was successfully employed as a solvent in the synthesis of 1,3-dioxanes and 1,3-dioxolanes carried out under Dean-Stark conditions by the acetalization of aliphatic and aromatic aldehydes or ketones, employing ammonium salts as environmentally friendly acidic catalysts.
- Azzena, Ugo,Carraro, Massimo,Mamuye, Ashenafi Damtew,Murgia, Irene,Pisano, Luisa,Zedde, Giuseppe
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supporting information
p. 3281 - 3284
(2015/06/25)
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- Synthesis and characterization of a tetracationic acidic organic salt and its application in the synthesis of bis(indolyl)methanes and protection of carbonyl compounds
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A new tetracationic acidic organic salt (TCAOS) based on DABCO was prepared, characterized and applied as an eco-friendly, powerful and reusable catalyst for the synthesis of bis(indolyl)methanes from indoles and carbonyl compounds in water with high turnover frequency (TOF). Also, this catalyst was successfully applied for acetalization of carbonyl compounds with diols under solvent-free conditions.
- Halimehjani, Azim Ziyaei,Hooshmand, Seyyed Emad,Shamiri, Elham Vali
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p. 21772 - 21777
(2015/03/18)
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- Acetalization of aldehydes and ketones over H4[SiW 12O40] and H4[SiW12O 40]/SiO2
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H4[SiW12O40] (H-SiW12) is demonstrated to be able to efficiently catalyze the acetalization of aldehydes and ketones with ethylene glycol and 1,3-propanediol. Nevertheless, the possible leaching and the recycling of H-SiW12 are two major disadvantages that largely restrict its further application in industry. Moreover, H 4[SiW12O40] tends to deactivate strong proton sites due to the small surface area of 10 m2 g-1. Due to interactions with surface silanol groups, the proton sites of polyoxometalates (POMs) on SiO2 are less susceptible to deactivation. As such, immobilization of H4[SiW12O40] onto SiO 2 leads to the heterogeneous catalyst H4[SiW 12O40]/SiO2 (H-SiW12/SiO 2), which can catalyze the acetalization of aldehydes and ketones with ethylene glycol and 1,3-propanediol selectively and efficiently without the need of a drying agent. The acetalization process can proceed smoothly at a relatively low temperature under solvent-free conditions. The catalyst of H 4[SiW12O40]/SiO2 can be recycled at least ten times without an obvious decrease in its catalytic activity. As far as we know, the TONs of the H-SiW12/SiO2-catalyzed acetalization of cyclohexanone with ethylene glycol, and benzaldehyde with 1,3-propanediol are the highest reported so far.
- Zhao, Shen,Jia, Yueqing,Song, Yu-Fei
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p. 2618 - 2625
(2014/07/22)
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- Rapid assessment of protecting-group stability by using a robustness screen
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An experimentally simple method has been developed to rapidly establish the stability of widely utilized silyl, acetal, and carbamate protecting groups to a given set of reaction conditions. Assessment of up to twelve protecting groups in a single experiment has been demonstrated. Evaluation of this protocol in two unrelated synthetic transformations suggests that this method can be used to select appropriate protecting groups in the design of synthetic routes.
- Collins, Karl D.,Ruehling, Andreas,Lied, Fabian,Glorius, Frank
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supporting information
p. 3800 - 3805
(2014/04/03)
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- Visible Light Photocatalytic Reduction of O-Thiocarbamates: Development of a Tin-Free Barton-McCombie Deoxygenation Reaction
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The Barton-McCombie deoxygenation is one of the most important transformations in the toolbox of organic chemists which has been the subject of a number of methodological developments. In this study, we report a photocatalyzed redox deoxygenation of secondary and tertiary alcohols from thiocarbamate precursors under visible light activation. The iridium complex Ir(ppy)3 proved to be the most efficient catalyst in the presence of Hünig's base as sacrifial electron donor. A mechanistic investigation is presented based on fluorescence quenching experiments and cyclic voltammetry.
- Chenneberg, Ludwig,Baralle, Alexandre,Daniel, Marion,Fensterbank, Louis,Goddard, Jean-Philippe,Ollivier, Cyril
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supporting information
p. 2756 - 2762
(2016/02/19)
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- Four acid-catalysed dehydration reactions proceed without interference
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Four acid-catalysed dehydration reactions can proceed in one pot, simultaneously and without interference, to yield one imine, one acetal (or boronic ester), one ester and one alkene, even though many other cross-products could be conceived. This advanced
- Lirag, Rio Carlo,Miljani?, Ognjen ?.
-
supporting information
p. 9401 - 9404
(2014/08/05)
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- Mesoporous poly-melamine-formaldehyde (mPMF)-a highly efficient catalyst for chemoselective acetalization of aldehydes
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A mesoporous poly-melamine-formaldehyde polymer with a high surface area, good porosity and a high density of amine and triazine functional groups was investigated as a highly efficient hydrogen-bonding catalyst. This porous organic polymer was found to be highly effective in catalyzing chemoselective acetalization of aldehydes, without the consumption of any dehydrating agents. The turnover frequency of mesoporous poly-melamine-formaldehyde is hundreds of times higher than melamine monomer, and this high efficiency is due to the high density of aminal (-NH-CH2-NH-) groups and triazine rings in the polymer network, which provides an inherently powerful system with multiple hydrogen bonds. This unique characteristic imparts mesoporous poly-melamine-formaldehyde polymer with a very high activity as a heterogeneous organocatalyst. The polymer is also low cost, and easy to be synthesized and recycled.
- Tan, Mei Xuan,Gu, Liuqun,Li, Nannan,Ying, Jackie Y.,Zhang, Yugen
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p. 1127 - 1132
(2013/06/05)
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- A new generation of aprotic yet Bronsted acidic imidazolium salts: Low toxicity, high recyclability and greatly improved activity
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Catalysts which have low antimicrobial toxicity and are aprotic, yet which can act as Bronsted acidic catalysts in the presence of protic additives have been developed. The catalysts are recyclable, considerably more active (i.e. can be used at 10-50 times lower loadings) and of broader scope than their antecedent generation.
- Myles, Lauren,Gore, Rohitkumar G.,Gathergood, Nicholas,Connon, Stephen J.
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p. 2740 - 2746
(2013/10/08)
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- The catalytic versatility of low toxicity dialkyltriazolium salts: In situ modification facilitates diametrically opposed catalysis modes in one pot
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The ability of triazolium salts to serve as a precatalyst for both an acid and a powerful base/nucleophile (controlled by additives) has been exploited in a process characterised by a unique in situ catalyst modification strategy. The Royal Society of Chemistry 2013.
- Myles, Lauren,Gathergood, Nicholas,Connon, Stephen J.
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supporting information
p. 5316 - 5318
(2013/06/27)
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- Synthesis of 2-R-1,3-dioxanes, derivatives of functionally substituted aldehydes of vanillin series
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By the condensation of substituted aldehydes of vanillin series with 1,3-propanediol in boiling benzene in the presence of sulfo cation exchanger FIBAN K-1 as catalyst functionally 2-R-substituted 1,3-dioxanes were synthesized.
- Dikusar,Potkin,Zvereva,Zhukovskaya,Petkevich,Pavlyuchenkova,Murashova,Polikarpov,Shunkevich,Yuvchenko,Zolotar'
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p. 221 - 227
(2013/07/25)
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- Microwave-assisted synthesis and bioactivity of some 2- dichloromethyl-1,3-dioxacycloalkanes
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A series of 2-dichloromelhyl-1,3-dioxacycloalkanes (3) was synthesized by microwave-assisted cyclization and insertion reaction. All the compounds were characterized by IR, 1H NMR, 13C NMR, MS and elemental analysis. The single crystal of compound (3b) was determined by X-ray crystallographic analysis. The preliminary bioassay results demonstrated that these compounds could alleviate acetochlor injury to maize.
- Ye, Fei,Sun, Chang-Ying,Zhao, Li-Xia,Li, Ying,Fu, Ying
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p. 159 - 164
(2019/01/21)
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- A METHOD OF ACETALIZING AN ALDEHYDE
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A method of acetalizing an aldehyde comprising reacting said aldehyde with an alcohol in the presence of a polymeric catalyst to form an acetal wherein the polymeric catalyst is a mesoporous poly-melamine-formaldehyde polymer.
- -
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Page/Page column 22; 23; 24
(2013/09/26)
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- Synthesis of a novel multi-SO3H functionalized ionic liquid and its catalytic activities
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A novel multi-SO3H functionalized ionic liquid is synthesized and a detailed account of its cata- lytic activities in acetalization and acetylation is given. The results showed that the ionic liquid is very efficient in the conventional acid-catalyzed reactions with good to excellent yields within a short reaction time. Oper- ational simplicity, small amounts required, low cost of the catalyst, high yields, scalability and reusability are the key features of this methodology, which indicates the high potentialities of the novel ionic liquid to be used in environmentally friendly processes. Pleiades Publishing, Ltd., 2012.
- Xudong, Sun,Huiquan, Xiao,Yijun, Du,Jingjing, Zhang,Xuezheng, Liang,Chenze, Qi
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p. 301 - 305
(2012/10/29)
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- Indium(III) triflate catalysed transacetalisation reactions of diols and triols under solvent-free conditions
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Acyclic acetals and ketals undergo transacetalisation in the presence of catalytic quantities of indium(III) triflate (In(OTf)3) and diols or triols under solvent-free conditions to generate the corresponding cyclic acetals and ketals in excellent yield. The methodology has been further developed to encompass a tandem acetalisation-acetal exchange protocol, which provides a facile and high yielding route to cyclic ketals from unreactive ketones under very mild reaction conditions.
- Smith, Brendan M.,Kubczyk, Tomasz M.,Graham, Andrew E.
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p. 7775 - 7781
(2012/09/21)
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- An efficient photoinduced deprotection of aromatic acetals and ketals
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A novel type of photodeprotection reaction of simple aromatic acetals and ketals is described. The deprotection is highly efficient under optimized conditions. The aromatic ring confers the photoreactivity to the compounds. The efficiency of the process depends on the structure of the acetal moiety. The common minor side reaction, the photooxidation, becomes the major reaction pathway in the cases of cyclic acetals. The use of photon as only reagent makes this procedure especially attractive for acetal deprotection.
- Thevenet, Damien,Neier, Reinhard
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experimental part
p. 331 - 346
(2011/04/22)
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- Mesoporous aluminosilicate-catalyzed allylation of carbonyl compounds and acetals
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A mesoporous aluminosilicate (Al-MCM-41) was found to be an effective heterogeneous catalyst for the reaction of both carbonyl compounds and acetals with allylsilanes to afford the corresponding homoallyl silyl ethers and homoallyl alkyl ethers, respectively. Both the mesoporous structure and the presence of aluminum moiety were indispensable for the high catalytic activity of Al-MCM-41. Moreover, Al-MCM-41 could catalyze the reaction of acetals chemoselectively in the presence of the corresponding carbonyl compounds. The solid acid catalyst Al-MCM-41 could be recovered easily by filtration and could be reused three times without a significant loss of catalytic activity.
- Ito, Suguru,Hayashi, Akira,Komai, Hirotomo,Yamaguchi, Hitoshi,Kubota, Yoshihiro,Asami, Masatoshi
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supporting information; experimental part
p. 2081 - 2089
(2011/04/19)
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- Indium triflate mediated tandem acetalisation-acetal exchange reactions under solvent-free conditions
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Acyclic acetals and ketals undergo exchange reactions in the presence of catalytic quantities of indium(III) triflate and diols to generate the corresponding cyclic acetals and ketals in excellent yield. The protocol is rapid, employs mild conditions and can be adapted to employ solvent-free reaction conditions. We have further developed this methodology to encompass a tandem acetalisation-acetal exchange protocol which provides facile access to cyclic ketals from unreactive ketones also under very mild, solvent-free reaction conditions.
- Smith, Brendan M.,Graham, Andrew E.
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experimental part
p. 6281 - 6283
(2011/12/14)
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- Highly recyclable, imidazolium derived ionic liquids of low antimicrobial and antifungal toxicity: A new strategy for acid catalysis
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Imidazolium derived ionic liquid catalysts have been developed which are aprotic and of low antimicrobial and antifungal toxicity, yet which can act as efficient Bronsted acidic catalysts in the presence of protic additives. The catalysts can be utilised at low loadings and can be recycled 15 times without any discernible loss of activity. The Royal Society of Chemistry 2010.
- Myles, Lauren,Gore, Rohitkumar,Pulak, Marcel,Gathergood, Nicholas,Connon, Stephen J.
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supporting information; experimental part
p. 1157 - 1162
(2010/10/04)
-
- The influence of the acidity of ionic liquids on catalysis
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Reactions performed in ionic liquids with BF4- as anion progress under strongly acidic conditions. The acidity of some air- and moisture-stable ionic liquids is explored and its effect on catalytic reactions is studied. The function of these ionic liquids in some traditional acid-catalyzed reactions is also tested, and the results merit a reconsideration of their influence on catalytic reactions and use in other applications.
- Cui, Xinjiang,Zhang, Shiguo,Shi, Feng,Zhang, Qinghua,Ma, Xiangyuan,Lu, Liujin,Deng, Youquan
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experimental part
p. 1043 - 1047
(2011/11/29)
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- Pyridinium ion catalysis of carbonyl protection reactions
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Aprotic pyridinium ions incorporating electron-withdrawing substituents on the aromatic ring are powerful catalysts for the acetalization of aldehydes and the formation of dithianes, dithiolanes, dioxanes, and dioxolanes. Under optimum conditions the best catalyst can be used at a loading as low as 0.1 mol% and can outperform a Bronsted acid catalyst with a pka of 2.2. Georg Thieme Verlag Stuttgart.
- Procuranti, Barbara,Myles, Lauren,Gathergood, Nicholas,Connon, Stephen J.
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scheme or table
p. 4082 - 4086
(2010/03/05)
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- Indium(III)trifluoromethanesulfonate as a mild, efficient catalyst for the formation of acetals and ketals in the presence of acid sensitive functional groups
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Aldehydes and ketones, including acetophenone and benzophenone, are readily protected under mild, neutral conditions in the presence of various alcohols or orthoformates and catalytic amounts of indium(III) trifluoromethanesulfonate (0.8 mol %) under either room temperature or mild heating conditions to give the corresponding cyclic and acyclic acetals and ketals in good to excellent yields. Acid sensitive functional groups, N-Boc, THP, and TBDMS do not undergo competitive deprotection under the reported conditions.
- Gregg, Brian T.,Golden, Kathryn C.,Quinn, John F.
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p. 3287 - 3295
(2008/09/21)
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- Unexpected catalysis: Aprotic pyridinium ions as active and recyclable Bronsted acid catalysts in protic media
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(Chemical Equation Presented) Simple pyridinium salt derivatives have been (rather unexpectedly) shown to promote highly efficient acetalization reactions of both aldehydes and ketones at ambient temperature. The optimum catalyst is aprotic, yet it can promote the formation of benzaldehyde dimethyl acetal at 0.1 mol % loading more efficiently than a protic Bronsted acid catalyst with a pKa of 2.2. The process is of wide scope with respect to both the nucleophilic and electrophilic components, and the ionic catalyst can be readily recovered by precipitation and reused without loss of activity.
- Procuranti, Barbara,Connon, Stephen J.
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supporting information; experimental part
p. 4935 - 4938
(2009/05/07)
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- Lewis acid-promoted intermolecular acetal-initiated cationic polyene cyclizations
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This paper describes a highly efficient intermolecular biomimetic polyene cyclization method using acetal as initiators. Both good yield and asymmetric induction were obtained. Copyright
- Zhao, Yu-Jun,Chng, Shu-Sin,Loh, Teck-Peng
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p. 492 - 493
(2007/10/03)
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- Indium triflate mediated acetalization of aldehydes and ketones
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Aldehydes and ketones are rapidly transformed into either acyclic or cyclic acetals at room temperature in high yields and in very short reaction times using catalytic quantities of indium triflate, in contrast to previous reports.
- Smith, Brendan M.,Graham, Andrew E.
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p. 9317 - 9319
(2007/10/03)
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- Reductive cleavage of acetals and ketals with 9-borabicyclo[3.3.1]nonane
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The reductive cleavage of benzaldehyde acetals and acetophenone ketals with the air-stable crystalline 9-borabicyclo[3.3.1]-nonane dimer provides monobenzylated ether derivatives of diols and 1,2-oxygen-transposed β-phenethyl alcohols, respectively. The boron moiety is effectively recovered through simple procedures which involve convenient air-stable reagents and boron byproducts. The process is particularly selective for 1,3-diols giving the more substituted monobenzyl ether derivatives exclusively. With acetophenone ketals both reduction and elimination occur, permitting 9-BBN-H to hydroborate the resulting styrene to produce 1,2-oxygen-transposed β-phenethyl alcohols cleanly. Potential applications of this new process were illustrated with the synthesis of the hallucinogen, mescaline, and the analgesic, ibufenac.
- Soderquist, John A.,Kock, Iveliz,Estrella, Maria E.
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supporting information
p. 1076 - 1079
(2012/12/23)
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- Chemoselective conversion of aromatic epoxide and 1,2-diol to 1,3-dioxane derivatives with phenyltrimethylammonium tribromide in the presence of a catalytic amount of antimony(III) bromide
-
trans-Stilbene oxide was oxidatively converted to 2-phenyl-1,3-dioxanes with phenyltrimethylammonium tribromide in the presence of various 1,3-diols and a catalytic amount of SbBr3 in DMSO at room temperature. Aromatic 1,2-diol, such as hydrobenzoin, was similarly converted to 2-aryl-1,3-dioxane derivatives under the same reaction conditions.
- Sayama, Shinsei
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p. 4001 - 4005
(2007/10/03)
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- Intermolecular reactions of chlorohydrine anions: Acetalization of carbonyl compounds under basic conditions
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Nonenolizable aldehydes and ketones react with 2-chloroethanol and 3-chloropropanol under basic conditions (t-BuOK, DMF/THF) with formation of 2-substituted 1,3-dioxolanes and 1,3-dioxanes, respectively. Conversion of the two-step addition-alkylation process depends on the electrophilicity of the carbonyl group that governs the equilibrium of addition of chloroalkoxides. This method of protection of carbonyl groups in the form of cyclic acetals under kinetically controlled conditions is complementary to the acid-catalyzed reaction with diols.
- Barbasiewicz, Michal,Makosza, Mieczyslaw
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p. 3745 - 3748
(2007/10/03)
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- Simple, mild and efficient thioacetalization and transthioacetalization of carbonyl compounds and deprotection of thioacetals: Unique role of thiols in the selectivity of thioacetalization
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Silica supported sodium hydrogen sulfate (NaHSO4·SiO 2) has been employed for efficient thioacetalization and transthioacetalization of carbonyl compounds in CH2Cl2 at room temperature. Selectivity of thioacetalization was dependent on the thiols used for the conversion. The same catalyst was also found to be effective for deprotection of thioacetals in CH2Cl2-H2O at room temperature.
- Das, Biswanath,Ramu, Ravirala,Reddy, Majjigapu Ravinder,Mahender, Gurram
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p. 250 - 254
(2007/10/03)
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- N-bromosuccinimide (NBS) catalyzed highly chemoselective acetalization of carbonyl compounds using silylated diols and pentaerythritol under neutral aprotic conditions
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Various types of carbonyl compounds are efficiently converted to their 1,3-dioxanes and pentaerythritol diacetals by the use of either 1,3-bistrimethylsiloxy propane (A) or 1,3-bistrimethylsilanyloxy-2,2- bistrimethylsilanyloxymethyl propane (D) and a catalytic amount of N-bromosuccinimide (3-10 mol%) under essentially neutral aprotic condition, respectively. A variety of functionalities such as both aliphatic and phenolic -OTBDMS, -OMe, -OBz, furan ring, double bonds and more significantly phenolic -OTHP survived under the present reaction condition. The efficient conversion of two α-tertiary ketones to their cyclic acetals was also achieved using the present protocol.
- Karimi, Babak,Hazarkhani, Hassan,Maleki, Jafar
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p. 279 - 285
(2007/10/03)
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- A convenient and highly efficient method for the protection of aldehydes using very low loading hydrous ruthenium(III) trichloride as catalyst
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A convenient method for the chemoselective protections of both aliphatic and aromatic aldehydes has been developed. Ruthenium(III) trichloride (0.1 mol %) has found to be an highly efficient catalyst in the acetalizations of aldehydes with various simple alcohols such as methanol, ethanol, or diols such as 1,2-ethylanediol and 1,3-propanediol under mild reaction conditions.
- Qi, Jian-Ying,Ji, Jian-Xin,Yueng, Chi-Hung,Kwong, Hoi-Lun,Chan, Albert S.C.
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p. 7719 - 7721
(2007/10/03)
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- A simple and practical synthetic protocol for acetalisation, thioacetalisation and transthioacetalisation of carbonyl compounds under solvent-free conditions
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A wide variety of carbonyl compounds can be converted smoothly to the corresponding acetals on treatment with alcohols or diols and triethyl orthoformate in the presence of a catalytic amount of (bromodimethyl)sulfonium bromide at room temperature. Similarly, various carbonyl compounds can be transformed into the corresponding dithioacetals on reaction with thiol or dithiols at room temperature by employing the same catalyst without any solvent. Moreover, O,O-acetals can also be converted into the corresponding dithioacetals under identical conditions. Some of the major advantages are mild reaction conditions, a high degree of efficiency, compatibilty with other protecting groups and the lack of solvents, particularly for thioacetalisation. In addition, no brominations occur at the double bond or α to the keto position or even in the aromatic ring under these experimental conditions. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Khan, Abu T.,Mondal, Ejabul,Ghosh, Subrata,Islam, Samimul
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p. 2002 - 2009
(2007/10/03)
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- Convenient preparation of cyclic acetals, using diols, TMS-source, and a catalytic amount of TMSOTf
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With use of diol, alkoxysilane, and a catalytic amount of trimethylsilyl trifluoromethanesulfonate (TMSOTf), carbonyl compounds are converted to acetals in good yields under mild conditions. This procedure, which was carried out without synthesizing the silylated diols, is a more convenient adaptation of Noyori's method. This acetalization applies to not only simple but also conjugated carbonyl compounds. Moreover, various TMS compounds, including solid supported compounds, are effective for this method instead of alkoxylsilane.
- Kurihara, Masaaki,Hakamata, Wataru
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p. 3413 - 3415
(2007/10/03)
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- Tetrabutylammonium tribromide (TBATB) as an efficient generator of HBr for an efficient chemoselective reagent for acetalization of carbonyl compounds
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Acyclic and cyclic acetals of various carbonyl compounds were obtained in excellent yields under a mild reaction condition in the presence of trialkyl orthoformate and a catalytic amount of tetrabutylammonium tribromide (TBATB) in absolute alcohol. Chemoselective acetalization of an aldehyde in the presence of ketone, unsymmetrical acetal formation, shorter reaction times, mild reaction conditions, the stability of acid-sensitive protecting groups, high efficiencies, facile isolation of the desired products, and the catalytic nature of the reagent make the present methodology a practical alternative.
- Gopinath, Rangam,Haque, Sk. Jiaul,Patel, Bhisma K.
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p. 5842 - 5845
(2007/10/03)
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- 2,4,4,6-Tetrabromo-2,5-cyclohexadienone (TABCO) as a versatile, efficient, and chemoselective catalyst for the acetalization and transacetalization of carbonyl compounds, the preparation of acetonides from epoxides and acylals (1,1-diacetates) from aldehydes
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The efficient and chemoselective preparation of acetals and ketals from carbonyl compounds, transacetalization reactions, the conversion of epoxides to acetonides, and the preparation of acylals from aldehydes in the presence of catalytic amounts of 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TABCO) are described.
- Firouzabadi, Habib,Iranpoor, Nasser,Shaterian, Hamid Reza
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p. 2195 - 2205
(2007/10/03)
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- A fluorous super br?nsted acid catalyst: Application to fluorous catalysis without fluorous solvents
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The preparation of a fluorous super Br?nsted acid catalyst, 4-(1H,1H-perfluorotetradecanoxy)-2,3,5,6-tetrafluorophenylbis (trifluoromethanesulfonyl)methane (3d), is described. The fluorous catalyst 3d can be recycled by using liquid/solid phase separation without fluorous solvents. A perfluorocarbon solvent is not essential for fluorous biphasic catalysis.
- Ishihara, Kazuaki,Hasegawa, Aiko,Yamamoto, Hisashi
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p. 1299 - 1301
(2007/10/03)
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- Highly efficient and chemoselective interchange of 1,3-oxathioacetals and dithioacetals to acetals promoted by N-halosuccinimide
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Highly efficient interconversion of a range of 1,3-oxathiolanes, 1,3-dithiolanes and 1,3-dithianes to their acetals at ambient temperature using N-bromosuccinimide or N-chlorosuccinimide and different types of alcohols and diols was investigated.
- Karimi, Babak,Seradj, Hassan,Maleki, Jafar
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p. 4513 - 4516
(2007/10/03)
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- Iodine-catalyzed, efficient and mild procedure for highly chemoselective acetalization of carbonyl compounds under neutral aprotic conditions
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Various types of carbonyl compounds are efficiently converted to their 1,3-dioxanes by the use of 1,3-bis(trimethylsiloxy)propane (BTSP) and a catalytic amount of iodine (3-7 mol%) under essentially neutral aprotic condition.
- Karimi, Babak,Golshani, Behzad
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p. 784 - 788
(2007/10/03)
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- An efficient procedure for the preparation of cyclic ketals and thioketals catalyzed by zirconium sulfophenyl phosphonate
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A convenient method for the preparation of cyclic ketals and thioketals using zirconium sulfophenyl phosphonate as catalyst is described.
- Curini,Epifano,Marcotullio,Rosati
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p. 1182 - 1184
(2007/10/03)
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- Zirconium tetrachloride (ZrCl4) catalyzed highly chemoselective and efficient acetalization of carbonyl compounds
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Zirconium tetrachloride (ZrCl4) is a highly efficient and chemoselective catalyst for the acetalization, and in-situ transacetalization of carbonyl compounds under mild reaction conditions.
- Firouzabadi, Habib,Iranpoor, Nasser,Karimi, Babak
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p. 321 - 323
(2007/10/03)
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- Efficient and chemoselective conversion of carbonyl compounds to 1,3-dioxanes catalyzed with N-bromosuccinimide under almost neutral reaction conditions
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(formula presented) Various types of carbonyl compounds were converted to the corresponding 1,3-dioxanes in the presence of ethyl orthoformate, 1,3-propanediol, and a catalytic amount of NBS via an in situ acetal exchange process. In contrast to conventional acid-catalyzed acetalization reactions, acid-sensitive substrates such as THP ethers and TBDMS ethers remain intact under described reaction conditions.
- Karimi, Babak,Ebrahimian, G. Reza,Seradj, Hassan
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p. 1737 - 1739
(2008/02/11)
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