- DMAP-based flexible polymer networks formed via Heck coupling as efficient heterogeneous organocatalysts
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Two DMAP-based flexible polymer networks TPB-DMAP and TPA-DMAP have been successfully synthesized via palladium catalyzed Heck cross-coupling. The structures of these polymers were confirmed by solid state 13C CP/MAS and Fourier transform infrared spectroscopy (FTIR). Although both polymers have negligible surface areas, they exhibit excellent catalytic efficiency for the acylation of 1-phenylethanol with acetic anhydride due to their good swelling capacities. Utilized as a typical catalyst, the polymer TPA-DMAP shows high activities for acylation of a variety of alcohols to the corresponding esters. Moreover, the catalyst can be recycled at least ten times without obvious loss of catalytic activity.
- Xu, Wei,Xia, Wu,Guan, Yukun,Wang, Yiming,Lu, Cuifen,Yang, Guichun,Nie, Junqi,Chen, Zuxing
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- Relaxation Studies on Model Compounds of Cyclohexyl-Based Polyacrylates
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The equilibrium and dynamic dielectric properties of cyclohexyl isobutyrate (CI) and cyclohexyl 2,4-dimethylglutarate (CG), model compounds of the repeating unit and the dimer of poly(cyclohexyl acrylate) (PCA), respectively, are determined.The results show that the dipole moment at 30 deg C of cyclohexyl 2,4-dimethylglutarate (2.84 D) is significantly higher than the value of this quantity (2.09 D) for its aromatic counterpart, phenyl 2,4-dimethylglutarate (PG), as a consequence of the strong preference for the high polarity t?, t? conformation in the racemic diad of the former compound.The dielectric relaxation spectrum of CI presents a relatively strong secondary relaxation, in comparion with that of the compounds with higher conformational versatility CG.Other esters such as PG and m-chlorophenyl 2,4-dimethylglutarate (MCPG) also exhibit weak secondary relaxations in their dielectric spectra.Attempts are made to explain at the molecular level the weak subglass absorptions of the esters based on 2,4-dimethylglutaric acid.The α relaxations in the model compounds are interpreted as terms of the coupling model.
- Diaz-Calleja, Ricardo,Riande, Evaristo,Roman, Julio San
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- Copper Ion Promoted Esterification of S-2-Pyridyl Thioates and 2-Pyridyl Esters. Efficient Methods for the Preparation of Hindered Esters
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The esterification of the S-2-pyridyl thioates and 2-pyridyl esters with alcohols in acetonitrile is greatly facilitated by the addition of cupric bromide and copper ion is observed to catalyze the reaction.The ester formation is found to be sensitive to solvents, metal salts, and reaction temperatures.The esterification of S-2-pyridyl thioates is much more rapid than the esterification of 2-pyridyl esters under the reaction conditions employed.This method is exceedingly effective in the preparation of sterically hindered esters and has advantages over known methods in many respects such as high yields, the mildness of the reaction, and the rapidity of the reaction.
- Kim, Sunggak,Lee, Jae In
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- A salt made of 4-N,N-dimethylaminopyridine (DMAP) and saccharin as an efficient recyclable acylation catalyst: A new bridge between heterogeneous and homogeneous catalysis
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Here, we report insights into the new recyclable catalyst 1, (DMAP·saccharin). The DMAP·saccharin-catalysed acylation of alcohols has been successfully carried out more than 8 times. Only 1 mol% of catalyst 1 efficiently promotes acylation with almost equimolar amounts of acid anhydrides, under both base-free and solvent-free conditions.
- Lu, Norman,Chang, Wei-Hsuan,Tu, Wen-Han,Li, Chieh-Keng
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- Esterification of sterically hindered acids and alcohols in fluorous media
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Sterically hindered esterification reactions are best performed in specific fluorous media in the presence of catalytic amounts of diphenylammonium triflate. Fluorous media, in addition to their positive effect on yields, have inherent favorable properties respecting environment and permitting simple work-up. Highly congested reagents, however, react only marginally.
- Gacem, Badra,Jenner, Gérard
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- Fluorous analogues of DMAP (F-DMAP): Reusable organocatalysts for acylation reaction
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A short and facile preparation of analogues of DMAP (F-DMAPs) labelled with fluorous chains is reported. These catalysts efficiently promote the acylation of alcohols with anhydrides (Ac2O, (i-PrCO)2O) and can be partially recovered and reused. The effectiveness of F-DMAP is similar to that of DMAP.
- Legros, Julien,Crousse, Benoit,Bonnet-Delpon, Danièle
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- Insight into the Mechanism of the Acylation of Alcohols with Acid Anhydrides Catalyzed by Phosphoric Acid Derivatives
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Insight into the mechanism of a safe, simple, and inexpensive phosphoric acid (H3PO4)-catalyzed acylation of alcohols with acid anhydrides is described. The corresponding in situ-generated diacylated mixed anhydrides, unlike traditionally proposed monoacylated mixed anhydrides, are proposed as the active species. In particular, the diacylated mixed anhydrides act as efficient catalytic acyl transfer reagents rather than as Br?nsted acid catalysts simply activating acid anhydrides. Remarkably, highly efficient phosphoric acid (1-3 mol %)-catalyzed acylation of alcohols with acid anhydrides was achieved and a 23 g scale synthesis of an ester was demonstrated. Also, phosphoric acid catalyst was effective for synthetically useful esterification from carboxylic acids, alcohols, and acid anhydride. Moreover, with regard to recent developments in chiral 1,1′-bi-2-naphthol (BINOL)-derived phosphoric acid diester catalysts toward asymmetric kinetic resolution of alcohols by acylation, some phosphate diesters were examined. As a result, a 31P NMR study and a kinetics study strongly supported not only the acid-base cooperative mechanism as previously proposed by other researchers but also the mixed anhydride mechanism as presently proposed by us.
- Hayashi, Hiroyuki,Yasukochi, Shotaro,Sakamoto, Tatsuhiro,Hatano, Manabu,Ishihara, Kazuaki
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p. 5197 - 5212
(2021/04/12)
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- Selective biocatalytic hydroxylation of unactivated methylene C-H bonds in cyclic alkyl substrates
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The cytochrome P450 monooxygenase CYP101B1 from Novosphingobium aromaticivorans selectively hydroxylated methylene C-H bonds in cycloalkyl rings. Cycloketones and cycloalkyl esters containing C6, C8, C10 and C12 rings were oxidised with high selectively on the opposite side of the ring to the carbonyl substituent. Cyclodecanone was oxidised to oxabicycloundecanol derivatives in equilibrium with the hydroxycyclodecanones.
- Sarkar, Md Raihan,Dasgupta, Samrat,Pyke, Simon M.,Bell, Stephen G.
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p. 5029 - 5032
(2019/05/21)
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- Pyridinium saccharinate salts as efficient recyclable acylation catalyst: A new bridge between heterogeneous and homogeneous catalysis
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It is important to find a way for separation of concerned chemicals from product mixture after reaction, in order to avoid spreading harmful chemicals to society. The homogeneous nature of DMAP-catalyzed acylation still suffers from the problems of catalyst separation and/or residual DMAP contamination. DMAP causes acute dermal toxicity, whereas the corresponding DMAP salt exhibits only slight irritation to the skin. Very recently, we found that the DMAP saccharinate salt is also great recyclable catalyst, whose acylation of alcohols has been successfully and effectively carried out 10 times without loss in activity. This report covers our comprehensive studies on using the pyridinium saccharinate salts as efficient recyclable acylation catalysts including 4-N,N-dimethylaminopyridinium saccharinate (A), 4-(1-pyrrolidinyl) pyridinium saccharinate (B), 2-N,N-dimethylaminopyridinium saccharinate (C), and pyridinium saccharinate (D). Their structure and reactivity have been studied. The salts A, C, and D contain very interesting seven-membered synthon showing multiple H-bonding interactions for pair of pyridinium cation and saccharinate anion in the solid state. The salt B exhibits H-bonding interaction of N(sac) ... H-N(py) in the solid state, instead of seven-membered synthon. The catalytic reactivity studies show that salts A and B are both very effective, with salt B even better in reactivity, and are both recyclable in the esterification of a variety of alcohols, under solvent-free and base-free conditions at room temperature.
- Lu, Norman,Chang, Wei-Hsuan,Wei, Rong-Jyun,Fang, Yung-Cheng,Han, Tu-Wen,Wang, Guo-Quan,Chang, Jia-Yaw,Wen, Yuh-Sheng,Liu, Ling-Kang
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p. 3468 - 3476
(2016/06/06)
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- On the understanding of BF3·Et2O-promoted intra- and intermolecular amination and oxygenation of unfunctionalized olefins
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BF3·Et2O was found to be effective for both intra- and intermolecular amination and oxygenation of unfunctionalized olefins. In the presence of 3 equiv. of BF3·Et2O, intramolecular hydroamination of N-(pent-4-enyl)-p-toluenesulfonamides, N-(hex-5-enyl)-p-toluenesulfonamides, intermolecular hydroamination between sulfonamides and cyclohexene, norbornene or styrene, lactonization of pent-4-enoic acid or hex-5-enoic acid compounds and esterification of cyclohexene with different carboxylic acids all proceeded readily, leading to the corresponding amination or oxygenation products in up to 99% isolated yields. Preliminary NMR experiments and DFT calculations suggested that the intramolecular hydroamination reactions proceeded via a sulfonimidic acid intermediate (N=S-OH), and formation of the corresponding Bronsted acid HF or HBF4 was less likely.
- Yang, Chun-Hua,Fan, Wen-Wen,Liu, Gong-Qing,Duan, Lili,Li, Lin,Li, Yue-Ming
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p. 61081 - 61093
(2015/08/03)
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- Fluorous 4-N,N-dimethylaminopyridium iodide: Recyclable organocatalysts by precipitation for acylation reaction at room temperature
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A novel fluorous DMAP quaternary ammonium iodide salt organocatalyst was prepared. This fluorous organocatalyst was successfully employed to the acylation reaction at room temperature without the use of a stoichiometric amount of external base. It could be recovered 3 times from the reaction mixture by simple precipitation with excellent purity for direct reuse.
- Yi, Wen-Bin,Zhu, Yi-Wei,Cai, Chun
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- RECYCLABLE CATALYSTS FOR ESTERIFICATION OR ACYLATION OF ALCOHOLS
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A compound is useful as a recyclable catalyst for esterification or acylation of alcohols and consists of saccharine and a compound comprising a pyridine moiety. In addition, also a method of preparing the compound and an ester synthesis method using the compound are introduced.
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Page/Page column 3
(2012/07/28)
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- Immobilized DMAP derivatives rivaling homogeneous DMAP
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The copper-catalyzed Huisgen reaction between azides and alkynes was utilized to covalently attach derivatives of 4-(dimethylamino)pyridine (DMAP) to a polystyrene resin (PS) support. The catalytic potential of these constructs as determined in acylation and aza-Morita-Baylis-Hillman reactions far exceeds that of commercially available DMAP-PS resins and is fully competitive with DMAP in homogeneous solution. Immobilization of 3,4-diaminopyridine catalysts on polystyrene by using the copper-catalyzed Huisgen reaction allowed the preparation of new supported catalysts ofunprecedented catalytic activity in acylation and aza-Morita-Baylis-Hillman reactions. Copyright
- D'Elia, Valerio,Liu, Yinghao,Zipse, Hendrik
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supporting information; experimental part
p. 1527 - 1533
(2011/04/22)
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- Fluorous 4-N,N-dimethylaminopyridine (DMAP) salts as simple recyclable acylation catalysts
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The use of an easily accessible fluorous salt of DMAP, 1-R, as an active and recyclable acylation catalyst, under simple conditions has been reported. The recyclability of organic- and metal-based catalysts is of prime interest for the development of sustainable synthesis processes. The alcohol and the anhydride were mixed in a 10 mL round-bottomed flask and 1-R was added. The DMAP-catalyzed esterification reaction of an alcohol is performed in nonpolar solvents with an anhydride as the acyl donor, in the presence of a base in stoichiometric amounts. The simplicity of the process (readily accessible catalyst, easy to handle and to recover) makes it an attractive alternative for cleaner and safer acylation reactions, which could be used with asymmetric dialkylaminopyridines, or in other transformations, such as the Baylis Hillman reaction.
- Vuluga, Daniela,Legros, Julien,Crousse, Benoit,Bonnet-Delpon, Daniele
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supporting information; experimental part
p. 1776 - 1779
(2010/06/14)
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- Dual behavior of alcohols in iodine-catalyzed esterification under solvent-free reaction conditions
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The dual behavior phenomenon of alcohols in iodine-catalyzed esterification under solvent-free reaction conditions (SFRCs) is described; the governing factor is the stability of the carbonium ion generated from the alcohol; high concentration reaction conditions (HCRCs) or dilute solutions are much less suitable. In the case of benzylic alcohols, loss of optical activity was noted, whereas alkyl alcohols furnished a product with retention of stereochemistry.
- Jereb, Marjan,Vra?i?, Dejan,Zupan, Marko
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scheme or table
p. 2347 - 2352
(2009/09/06)
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- Iron-catalysed green synthesis of carboxylic esters by the intermolecular addition of carboxylic acids to alkenes
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Iron triflate, in situ-formed from FeCl3 and triflic acid, or FeCl3 and silver triflate efficiently catalyse the intermolecular addition of carboxylic acids to various alkenes to yield carboxylic esters; the reaction is applicable to the synthesis of unstable esters, such as acrylates. The Royal Society of Chemistry.
- Choi, Jun-Chul,Kohno, Kazufumi,Masuda, Daisuke,Yasuda, Hiroyuki,Sakakura, Toshiyasu
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p. 777 - 779
(2008/09/16)
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- Steric effects in the uncatalyzed and DMAP-catalyzed acylation of alcohols - Quantifying the window of opportunity in kinetic resolution experiments
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The kinetics of the reaction of several alcohols (benzyl alcohol, ethanol, 1-phenylethanol, cyclohexanol, and 1-methyl-1-phenylethanol) with a selection of anhydrides (acetic anyhydride, propionic anhydride, isobutyric anhydride, isovaleric anhydride, and pivalic anhydride) as catalyzed by 4-(N,N-dimethylamino)pyridine (DMAP)/triethyl amine have been studied in CH 2Cl2 at 20°C. In all cases the reaction kinetics can be described by rate laws containing a DMAP-catalyzed term and an uncatalyzed (back-ground) term. The rate constants for the background reaction respond sensi tively to changes in the steric demand of the alcohol and the anhydride substrates, making the reaction of cyclohexanol with acetic anhydride 526 times faster than the reaction with pivalic anhydride. Steric effects are even larger for the catalyzed reaction and the reactivity difference between acetic and pivalic anhydride exceeds a factor of 8000 for the reaction of cyclohexa nol. There is, however, no linear correlation between the steric effects on the catalyzed and the uncatalyzed part. As a consequence there are substrate combinations with dominating catalytic terms (such as the reaction of benzyl alcohol with isobutyric anhydride), while other substrate combinations (such as the reaction of cyclohexanol with pivalic anhydride) are characterized through a dominating background process. The implications of these findings for the kinetic resolution of alcohols are discussed.
- Fischer, Christian B.,Xu, Shangjie,Zipse, Hendrik
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p. 5779 - 5784
(2008/03/14)
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- Electronic and steric substituent influences on the conformational equilibria of cyclohexyl esters: The anomeric effect is not anomalous!
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The cyclohexyl esters of a series of carboxylic acids, RCO2H, spanning a range of electronegativities and quotients of steric hindrance for the R substituent (R = Me, Et, iPr, tBu, CF3, CH2Cl, CHCl2, CH2Br, CHBr2, and CBr3) were prepared. Their conformational equilibria in CD2Cl2 were examined by low-temperature 1H NMR spectroscopy to study the axial or equatorial orientation of the ester functionality with respect to the adopted chair conformation of the cyclohexane ring. The ab initio and DFT geometry-optimized structures and relative free energies of the axial and equatorial conformers were also calculated at the HF/ 6-311G**, MP2/6-311G, and B3LYP/ 6-31G** levels of theory, both in the gas phase and in solution. In the latter case, a self-consistent isodensity polarized continuum model was employed. Only by including electron correlation in the modeling calculations for the solvated molecules was it possible to obtain a reasonable correlation between ΔG°calcd and ΔG°exp. Both the structures and the free energy differences of the axial and equatorial conformers were evaluated with respect to the factors normally influencing conformational preference, namely, 1,3-diaxial steric interactions in the axial conformer and hyperconjugation. It was assessed that hyperconjugative interactions, σC-C/σC-H and σC-O*, together with a steric effect - the destabilization of the equatorial conformer with increasing bulk of the R group - were the determinant factors for the position of the conformational equilibria. Thus, because hyperconjugation is held responsible as the mitigating factor for the anomeric effect in 2-substituted, six-membered saturated heterocyclic rings, and since it is also similarly responsible, at least partly, in these monosubstituted cyclohexanes for a preferential shift towards the axial conformer, the question is therefore raised: can the anomeric effect really be construed as anomalous?
- Kleinpeter, Erich,Taddei, Ferdinando,Wacker, Philipp
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p. 1360 - 1368
(2007/10/03)
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