- Chromatography-Free Esterification Reactions Using a Bifunctional Polymer
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A linear polystyrene functionalized with both nucleophilic DMAP groups and sterically hindered tertiary amine groups was synthesized and used homogeneously in a range of esterification reactions between alcohols and various carboxylic acid derivatives. The polymer was highly effective in such reactions where the DMAP groups served as catalytic groups. The ester products of these reactions could be isolated in high purity and yield without the need for chromatographic purification, and the polymer could be recovered and reused numerous times with no apparent decrease in utility.
- Ma, Shuang,Toy, Patrick H.
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Read Online
- Two Approaches for CAL-B-Catalyzed Enantioselective Deacylation of a Set of α-Phenyl Ethyl Esters: Organic Solvent with Sodium Carbonate and Micro-aqueous Medium
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Herein, we report an efficient enantioselective cleavage of the acyl- moiety of a set of α- phenyl ethyl esters with different chain-lengths catalyzed by lipase B from Candida antarctica (CAL-B) by comparing two reactional approaches: anhydrous media with sodium carbonates and micro-aqueous medium. The deacylation is performed in organic solvent, in the presence of Na2CO3 in the first case, and by addition of a drop of phosphate buffer solution pH 7 in the second. The results show the high efficiency of the deacylation in the presence of the sodium carbonate for the enzymatic resolution of all the esters and that in term of reactivity (31% ≤ conv ≤ 50%) and selectivity (E > 200). While, during the hydrolysis in micro-aqueous media, the conversion is strongly affected by the length of the acyl-chain side, the conversion decreases from conv = 50% with the 1-phenylethyl acetate 1a to conv = 19% with 1-phenyethyl dodecanoate 6a, and this, even if the selectivity remains high (E > 89). In both conditions, the lipase CAL-B shows a high enantioselectivities in favor of (R)-1-phenyl ethanol enantiomer (conv > 45%, E > 200) but the reactivity is modulated by the form and the size of the acyl-chain side. Graphic Abstract: [Figure not available: see fulltext.].
- Razi, Samra,Zeror, Saoussen,Merabet-Khelassi, Mounia,Kolodziej, Emilie,Toffano, Martial,Aribi-Zouioueche, Louisa
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p. 2603 - 2611
(2021/01/15)
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- 18O-Labeled chiral compounds enable the facile determination of enantioselectivity by mass spectroscopy
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The synthesis of 18O-labeled enantioenriched compounds and their facile evaluation system to determine enantiomeric excess (ee) using mass spectroscopy was described. Equimolar mixture of 18O-labeled and non-labeled pseudo-enantiomers were used as a substrate for enzyme-catalyzed kinetic resolution. Ees determined by mass spectroscopy showed good agreement with those by HPLC. Our method would be a promising tool for fast evaluation of ee and contribute to development of enantioselective transformations.
- Mandai, Kyoko,Tsuchihashi, Yuta,Ashikari, Yosuke,Yoshida, Jun-ichi,Nagaki, Aiichiro
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- An extremely efficient and green method for the acylation of secondary alcohols, phenols and naphthols with a deep eutectic solvent as the catalyst
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The typical deep eutectic solvent [CholineCl][ZnCl2]3, easily prepared from choline chloride and zinc chloride, is green and useful for the acylation of secondary alcohols, phenols, and naphthols with acid anhydrides. Its efficiency allows the acylation of sterically hindered secondary alcohols and acid anhydrides to proceed in high yield under mild condition. The catalyst is cheap, easy to handle, conveniently synthesized in a single step, and recyclable for several times without significant loss of catalytic activity.
- Nguyen, Hai Truong,Tran, Phuong Hoang
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p. 98365 - 98368
(2016/10/31)
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- Efficient O-Acylation of Alcohols and Phenol Using Cp2TiCl as a Reaction Promoter
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A method has been developed for the conversion of primary, secondary, and tertiary alcohols, and phenol, into the corresponding esters at room temperature. The method uses a titanium(III) species generated from a substoichiometric amount of titanocene dichloride together with manganese(0) as a reductant, as well as methylene diiodide. It involves a transesterification from an ethyl ester, or a reaction with an acyl chloride. A radical mechanism is proposed for these transformations.
- Durán-Pe?a, María Jesús,Botubol-Ares, José Manuel,Hanson, James R.,Hernández-Galán, Rosario,Collado, Isidro G.
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supporting information
p. 3584 - 3591
(2016/07/28)
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- Dynamic double kinetic resolution of amines and alcohols under the cocatalysis of Raney nickel/Candida antarctica lipase B: From concept to application
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Herein, we have established a dynamic double kinetic resolution (DDKR) strategy under the co-catalysis of Raney nickel and Candida antarctica lipase B (CAL-B) for the one-pot simultaneous resolution of primary amines and secondary alcohols (or esters). The DDKR strategy was successfully applied to the resolution of a series of racemic amines and secondary alcohols (or esters) as well as mexiletine, an important antiarrhythmic agent. The catalysts could be recycled and reused several times with the same high activity. Scale-up experiments were also successful. As a more atom-economical and efficient process than traditional simple kinetic resolutions, the DDKR strategy can be widely used to prepare optically pure amines and alcohols.
- Xia, Bo,Cheng, Guilin,Lin, Xianfu,Wu, Qi
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p. 2917 - 2923
(2014/05/20)
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- Bi-aryl rotation in phenyl-dihydroimidazoquinoline catalysts for kinetic resolution of arylalkyl carbinols
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Chiral nucleophilic catalysts, 6-aryl-phenyl-dihydroimidazoquinolines (PIQs), were designed, synthesised and applied to the kinetic resolution of arylalkyl carbinols with very high selectivity (S) factors (up to 530). Density functional theory calculations indicate that multiple noncovalent interactions play a key role in chiral recognition between 6-aryl-PIQ catalysts and chiral secondary alcohol substrates. The Royal Society of Chemistry 2014.
- Wang, Zheng,Ye, Jinjin,Wu, Rui,Liu, Yang-Zi,Fossey, John S.,Cheng, Jiagao,Deng, Wei-Ping
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p. 1909 - 1913
(2014/06/24)
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- Kinetic studies on sec-alcohol racemization with dicarbonylchloro(pentabenzylcyclopentadienyl)- and dicarbonylchloro(pentaphenylcyclopentadienyl)ruthenium catalysts
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Pentasubstituted cyclopentadienyl complexes of ruthenium R5CpRu(CO)2Cl (R=Ph, benzyl) form, upon activation with tBuOK, highly active catalysts for racemization of chiral sec-alcohols. In combination with suitable resolving enzymes, such catalyst systems can efficiently be utilized for dynamic kinetic resolution reactions providing chiral alcohols, after hydrolysis of the corresponding acetates, in high yields and high enantiomeric purities. Here, three such ruthenium complexes were first characterized by NMR spectroscopy and cyclic voltammetry analysis (CVA) for elucidating their electronic characteristics in detail. Then, accurate kinetic studies were performed providing for the first time the calculated racemization rate constants for such catalyst systems. Furthermore, the dependence of the racemization rate on the electronic structure of the catalyst was investigated from the Hammett constants, substitution patterns of the substrate, and by isotopic labeling studies. The results obtained support the earlier suggested racemization reaction mechanism and indicated that the electron-rich catalyst Bn5CpRu(CO)2Cl (Bn=benzyl) racemizes electron-rich substrates more efficiently and in most cases faster than its pentaphenyl substituted analogue, formerly often considered as the leading catalyst candidate for dynamic kinetic resolution applications. The electron-deficient catalyst Ph5CpRu(CO)2Cl, in turn, is more efficient for electron-poor substrates.
- Mavrynsky, Denys,Murzin, Dmitry Yu.,Leino, Reko
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p. 2436 - 2445
(2013/08/23)
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- Kinetic resolution of secondary alcohols by chiral dmap derivatives prepared by the Ugi multicomponent reaction
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The kinetic resolution of secondary alcohols was examined by new chiral DMAP derivatives, which can readily be prepared by the Ugi multicomponent reaction in a one-pot operation. The initial screening of DMAP derivatives indicated that the catalyst bearing L-valine with an S configuration at the a-position of amide showed the best stereoselectivity factor. After the reaction conditions were optimized with (S,S)-4a in the kinetic resolution of secondary alcohols, various acyclic and cyclic secondary alcohols could be resolved with an s -factor of up to 12.
- Mandai, Hiroki,Irie, Shunsuke,Akehi, Masaru,Yuri, Kazunobu,Yoden, Masaaki,Mitsudo, Koichi,Suga, Seiji
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p. 329 - 340
(2013/03/28)
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- Obtaining enriched compounds via a tandem enantioselective reaction and kinetic resolution polishing sequence
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Herein we describe a tandem method of coupling an enantioselective reaction with a nonenzymatic kinetic resolution to prepare highly enantioenriched compounds. The procedure employs a moderately selective enantioselective reaction on a ketone or aldehyde to form an enriched alcohol followed by a kinetic resolution of the alcohol to generate ee's of >99% in yields greater than what is possible with a kinetic resolution. This method highlights an avenue to quickly acquire highly enriched compounds without developing and optimizing a new methodology.
- Klauck, Maggie I.,Patel, Sachin G.,Wiskur, Sheryl L.
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experimental part
p. 3570 - 3575
(2012/06/15)
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- Nonenzymatic dynamic kinetic resolution of secondary alcohols via enantioselective acylation: Synthetic and mechanistic studies
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Because of the ubiquity of the secondary carbinol subunit, the development of new methods for its enantioselective synthesis remains an important ongoing challenge. In this report, we describe the first nonenzymatic method for the dynamic kinetic resolution (DKR) of secondary alcohols (specifically, aryl alkyl carbinols) through enantioselective acylation, and we substantially expand the scope of this approach, vis-a-vis enzymatic reactions. Simply combining an effective process for the kinetic resolution of alcohols with an active catalyst for the racemization of alcohols did not lead to DKR, due to the incompatibility of the ruthenium-based racemization catalyst with the acylating agent (Ac2O) used in the kinetic resolution. A mechanistic investigation revealed that the ruthenium catalyst is deactivated through the formation of a stable ruthenium-acetate complex; this deleterious pathway was circumvented through the appropriate choice of acylating agent (an acyl carbonate). Mechanistic studies of this new process point to reversible N-acylation of the nucleophilic catalyst, acyl transfer from the catalyst to the alcohol as the rate-determining step, and carbonate anion serving as the Bronsted base in that acyl-transfer step.
- Lee, Sarah Yunmi,Murphy, Jaclyn M.,Ukai, Atsushi,Fu, Gregory C.
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p. 15149 - 15153
(2012/10/30)
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- Immobilized redox enzymatic catalysts: Baeyer-Villiger monooxygenases supported on polyphosphazenes
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A novel method has been employed for the selective covalent co-immobilization of a Baeyer-Villiger monooxygenase (phenylacetone monooxygenase from Thermobifida fusca) and a NADPH recycling enzyme (glucose-6-phosphate dehydrogenase) on the same polyphosphazene carrier for the first time starting from {NP[O2C12H8-x(NH 2)x]}n (x ranging from 0.5 to 2) using glutaraldehyde as connector. In all cases the preparation was active and it was found that the optimum proportion of amino groups in the starting polyphosphazene was 0.5 per monomer. The immobilized biocatalysts showed similar selectivity when compared with the isolated monooxygenase, demonstrating the potential of this novel type of immobilizing material, although their recyclability must still be improved.
- Cuetos, Anibal,Rioz-Martinez, Ana,Valenzuela, Maria L.,Lavandera, Ivan,De Gonzalo, Gonzalo,Carriedo, Gabino A.,Gotor, Vicente
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experimental part
p. 178 - 183
(2012/03/22)
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- Evaluation of snake venom phospholipase A2: Hydrolysis of non-natural esters
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Phospholipase A2 from the rattlesnake Crotalus durissus terrificus was employed for the first time to test its enantioseletivity on the hydrolysis of different non-natural esters. It was observed that the structure of this small enzyme is restrictive in the choice of its lipase action with non-natural substrates. Two forms of the enzyme were used; free and as its cross-linked enzyme aggregate (CLEA). With all substrates, the free enzyme showed activity similar to the CLEA preparation. The advantage of the CLEA phospholipase is the possibility to reuse it in several consecutive reactions without a decrease of activity and selectivity with good but higher yields and ee than with the free enzyme.
- Pirolla, Renan A. S.,Baldasso, Paulo A.,Marangoni, Se?rgio,Moran, Paulo J. S.,Rodrigues, Jose? Augusto R.
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experimental part
p. 300 - 307
(2011/10/05)
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- Structure-enantioselectivity effects in 3,4-dihydropyrimido[2,1-b] benzothiazole-based isothioureas as enantioselective acylation catalysts
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The catalytic activity and enantioselectivity in the kinetic resolution of (±)-1-naphthylethanol with a range of structurally related 3,4-dihydropyrimido[2,1-b]benzothiazole-based catalysts is examined. Of the isothiourea catalysts screened, (2S,3R)-2-phenyl-3-isopropyl substitution proved optimal, giving good levels of selectivity in the kinetic resolution of a number of secondary alcohols (S values up to >100 at ～50% conversion). Low catalyst loadings (0.10-0.25 mol%) of the optimal isothiourea can be used to generate enantiopure alcohols (>99% ee) in good yields.
- Belmessieri, Dorine,Joannesse, Caroline,Woods, Philip A.,MacGregor, Callum,Jones, Caroline,Campbell, Craig D.,Johnston, Craig P.,Duguet, Nicolas,Concellon, Carmen,Bragg, Ryan A.,Smith, Andrew D.
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scheme or table
p. 559 - 570
(2011/03/16)
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- Dynamic kinetic resolution of secondary aromatic alcohols with new efficient acyl donors
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A new and efficient dynamic kinetic resolution (DKR) process of secondary aromatic alcohols by using long carbon-chain esters as acyl donors has been developed. During the process, the transesterification catalyzed by CD8604 was found to be the main reason for the decrease in enantiomeric excess (ee). Using complex acyl donors, such as 4-chlorophenyl valerate, we could effectively inhibit the resin-catalyzed transesterification, and an excellent ee value (>99%) at high yield (>99%) was achieved. The mechanism for the inhibition of resin-catalyzed transesterification is believed to be the formation of micro-micelles in the pores of CD8604. It is noteworthy that the system can be reused more than 20 times without a loss of yield or ee value.
- Xu, Gang,Chen, Yongjun,Wu, Jianping,Cheng, Yongmei,Yang, Lirong
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experimental part
p. 1373 - 1378
(2011/11/06)
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- Esterase screening using whole cells of Brazilian soil microorganisms
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A miniaturized enzymatic assay using fluorescent probes to reveal esterase producing microorganisms was optimized and applied to screen 64 soil bacterial strains. The best results were validated using traditional non-fluorogenic assays with acetyl and propanoyl phenylethanol to confirm the miniaturized results. The most active microorganisms belong to the genus Bacillus showing esterase activity and good enantiomeric ratios for the resolution of phenylethanol derivatives (E > 30). Part of the microorganisms are kept in our laboratory in glycerol or freezedried and the best microorganisms will be deposited in the CBMAI/CPQBA/Unicamp culture collection.
- Mantovani, Simone M.,De Oliveira, Luciana G.,Marsaioli, Anita J.
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experimental part
p. 1484 - 1489
(2010/11/05)
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- BVMO-catalysed dynamic kinetic resolution of racemic benzyl ketones in the presence of anion exchange resins
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4-Hydroxyacetophenone monooxygenase from Pseudomonas fluorescens ACB was employed in the presence of a weak anion exchange resin to perform dynamic kinetic resolutions of racemic benzyl ketones with high conversions and good optical purities. Different parameters that affect to the efficiency of the enzymatic Baeyer-Villiger oxidation and racemisation were analyzed in order to optimize the activity and selectivity of the biocatalytic system. The Royal Society of Chemistry.
- Rodriguez, Cristina,De Gonzalo, Gonzalo,Rioz-Martinez, Ana,Torres Pazmino, Daniel E.,Fraaije, Marco W.,Gotor, Vicente
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body text
p. 1121 - 1125
(2010/06/20)
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- A highly selective ferrocene-based planar chiral PIP (Fc-PIP) acyl transfer catalyst for the kinetic resolution of alcohols
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Novel planar chiral ferrocene nucleophilic catalysts (Fc-PIP) containing both central and planar chiral elements were designed and synthesized for catalytic enantioselective acyl transfer of secondary alcohols. A remarkably efficient catalyst with high selectivity factors (up to S = 1892) was identified. Comparing the combination of central and planar chirality revealed a strong requirement for the "matched" chiral elements, indicating that the stereogenic center of the imidazole rings should present itself on the same face as the ferrocenyl fragment; otherwise, the catalyst is completely inactive. An exclusively stacked transition state that accounts for the high selectivity of the kinetic resolution of secondary alcohols is proposed. Notably, this newly designed catalyst family is suitable for the catalytic kinetic resolution of bulky arylalkyl carbinols, producing esters with extremely high ee (>99%).
- Hu, Bin,Meng, Meng,Wang, Zheng,Du, Wenting,Fossey, John S.,Hu, Xinquan,Deng, Wei-Ping
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supporting information; experimental part
p. 17041 - 17044
(2011/02/16)
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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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- 2,2-disubstituted propionic anhydrides: Effective coupling reagents for the kinetic resolution of secondary benzylic alcohols using BTM
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A variety of optically active benzylic alcohols possessing aliphatic substituents at the C-1 position are produced by the kinetic resolution of racemic secondary alcohols using free carboxylic acids with 2,2-disubstituted propionic anhydrides and (+)-benzotetramisole (BTM). Evaluation of the efficiency of this asymmetric esterification using several anhydrides derived from aliphatic carboxylic acids were carried out by comparing the efficiencies of the kinetic resolution of (±)-1-phenyl-l-propanol. It was found that not only pivalic anhydride is a very widely usable reagent to produce the corresponding esters with high ee's in the presence of BTM, but other 2,2-disubstituted propionic anhydrides, such as 2-methyl-2-phenylpropionic anhydride (MPPRA) and 2,2-diphenylpropionic anhydride (DPPRA), are also applicable as effective coupling reagents for producing the optically active esters and alcohols with high selectivities. This protocol directly provides chiral carboxylic esters from free carboxylic acids and racemic secondary alcohols by utilizing the transacylation process to generate mixed anhydrides from the acid components and sterically hindered carboxylic anhydrides.
- Shiina, Isamu,Nakata, Kenya,Sugimoto, Masuhiro,Onda, Yu-Suke,Iizumi, Takashi,Ono, Keisuke
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scheme or table
p. 801 - 810
(2010/09/18)
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- o-benzenedisulfonimide as a soft, efficient, and recyclable catalyst for the acylation of alcohols, phenols, and thiols under solvent-free conditions: Advantages and limitations
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o-Benzenedisulfonimide turns out to be a highly efficient Bransted acid catalyst for the acylation of a number of alcohols, phenols, and thiols under a metal- and solvent-free procedure; reaction conditions are mild and yields very good. After the workup, the catalyst can be easily recovered and purified, ready to be reused, with economic and ecological advantages. Georg Thieme Verlag Stuttgart · New York.
- Barbero, Margherita,Cadamuro, Silvano,Dughera, Stefano,Venturello, Paolo
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experimental part
p. 3625 - 3632
(2009/07/04)
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- Origin of enantioselectivity in CF3-PIP-catalyzed kinetic resolution of secondary benzylic alcohols
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Computational studies provide support for the involvement of intermolecular π-interactions in the chiral recognition of secondary benzylic alcohols by the enantioselective acyl transfer catalyst CF3-PIP. Copyright
- Li, Ximin,Liu, Peng,Houk,Birman, Vladimir B.
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supporting information; experimental part
p. 13836 - 13837
(2009/02/07)
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- Enzymatic kinetic resolution of racemic ketones catalyzed by Baeyer-Villiger monooxygenases
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A set of racemic cyclic and linear ketones, as well as 2-phenylpropionaldehyde, were tested as substrates in the enzymatic Baeyer-Villiger oxidation catalyzed by two Baeyer-Villiger monooxygenases: phenylacetone monooxygenase (PAMO) and 4-hydroxyacetophenone monooxygenase (HAPMO). Excellent enantioselectivites (E > 200) can be obtained in the kinetic resolution processes depending on the substrate structure and the reaction conditions. The parameters affecting the biocatalytic properties of these enzymes were also studied, in order to establish a deeper understanding of these novel biocatalysts.
- Rodriguez, Cristina,de Gonzalo, Gonzalo,Fraaije, Marco W.,Gotor, Vicente
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p. 1338 - 1344
(2008/02/09)
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- Benzotetramisole: A remarkably enantioselective acyl transfer catalyst
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A commercially available pharmaceutical, tetramisole, was found to be a competent enantioselective acylation catalyst. Its benzannellated analogue, benzotetramisole (BTM), produced outstanding enantioselectivities in kinetic resolution of secondary benzylic alcohols.
- Birman, Vladimir B.,Li, Ximin
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p. 1351 - 1354
(2007/10/03)
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- Kinetic resolution of alcohols using a 1,2-dihydroimidazo[1,2-a]quinoline enantioselective acylation catalyst
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(Chemical Equation Presented) A new enantioselective acylation catalyst (CI-PIQ), designed to provide enhanced π-stacking with benzylic and cinnamyl alcohol substrates, was found to give considerably increased reaction rates and selectivities compared with the first-generation catalyst CF3-PIP.
- Birman, Vladimir B.,Jiang, Hui
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p. 3445 - 3447
(2007/10/03)
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- Enantioselective acyl transfer catalysts and their use in kinetic resolution of alcohols and desymmetrization of meso-diols
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Novel enantioselective acylation catalysts comprising chiral derivatives of DHIP and DHIQ, having the following representative general structures are disclosed: These new compounds are useful for resolving racemates or further enhancing the enantiomeric excess of an enantiomerically enriched composition and for desymmetrizing meso compounds.
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Page/Page column 19-20
(2008/06/13)
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- Method for producing organic compounds by substituting halogen atoms
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The invention pertains to a method in which a halogen atom of an organic compound is replaced with a group derived from a nucleophilic agent, at high yield and high efficiency, by the following method which includes a step of reacting the nucleophilic agent with an organic material having a halogen atom bonded to a carbon atom having four σ bonds, more specifically: a method for producing an organic compound having Q, the method including a step of reacting a compound represented by general formula (2) with an organic starting material having at least one halogen atom bonded to a carbon atom having four σ bonds so as to replace the halogen atom in the organic starting material with Q:MQa (wherein M represents an alkali metal atom, an alkali earth metal atom, or a rare earth metal atom; Q represents a moiety of an inorganic acid or an active hydrogen compound derived by eliminating a proton, wherein Q is a halogen atom different from the halogen atom in the organic starting material having the halogen atom bonded to the carbon atom having the four σ bonds; and a represents an integer of 1 to 3) in the presence of a compound represented by general formula (1) (wherein Z- represents an anion derived by eliminating a proton from an inorganic acid or an active hydrogen compound; R2 is the same or different; R2 each independently represent a C1-C10 hydrocarbon group or two R2 on the same nitrogen atom may be bonded with each other to form a ring with the nitrogen atom).
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- 2,3-Dihydroimidazo[1,2-a]pyridines: A new class of enantioselective acyl transfer catalysts and their use in kinetic resolution of alcohols
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The long-known, but previously unexplored 2,3-dihydroimidazo[1,2-a]pyridine (DHIP) has been shown to be a competent acyl transfer catalyst. Its chiral 2-phenyl derivatives obtainable in two steps from commercially available starting materials have proved to be effective acylation catalysts, giving high levels of enantioselectivity (s = 20-85) in kinetic resolution of secondary benzylic alcohols. A transition state model explaining the observed selectivity has been proposed. Copyright
- Birman, Vladimir B.,Uffman, Eric W.,Jiang, Hui,Li, Ximin,Kilbane, Corey J.
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p. 12226 - 12227
(2007/10/03)
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- Microwave oven synthesis of esters promoted by imidazole
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Using imidazole as promotion agent, primary, secondary and phenolic alcohol compounds were esterified with aliphatic and aromatic carboxylic acid anhydrides. Heating a ternary mixture of alcohol, anhydride and imidazole in an unmodified microwave oven produced esters in low to high yields, depending on the steric bulk of the alcohol.
- Hirose, Takuji,Kopek, Benjamin G.,Wang, Zhao-Hui,Yusa, Ritsuko,Baldwin, Bruce W.
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p. 1831 - 1833
(2007/10/03)
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- Esterification of alkene with cerium(IV) sulfate in carboxylic acid
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Reaction of alkenes [cyclohexene (1), cycloheptene (2), cyclooctene (3), 1-heptene (4), 1-octene (5), styrene (6), 1,7-octadiene (7), indene (8), and 1,2-dihydronaphthalene (9)] with cerium(IV) sulfate (CS) in carboxylic acids [formic acid, acetic acid, and propionic acid] readily yielded the corresponding carboxylic esters. This addition reaction follows the Markovnikov rule. This reaction provides a new simple method for preparing carboxylic esters from alkenes. It was also found that this method is useful for formylation.
- Horiuchi, C. Akira,Fukushima, Tomoaki,Furuta, Noriyuki,Chai, Wen,Ji, Shun-Jun,Saito, Yoshikazu,Hashimoto, Chikao,Takahashi, T. Tomoyoshi,Sugiyama, Takashi,Muto, Akinori,Sakata, Yusaku,Nozaki, Sukekatsu
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p. 270 - 272
(2007/10/03)
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- Resolution of secondary alcohols using 2-acyl-3-phenyl-l-menthopyrazoles as enantioselective acylating agents
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The chelation of AlCl3 with N-acylpyrazoles leads to structural fixation of the acyl moiety and an acceleration in the rate of acylation of secondary alcohols. The chiral environment of the fixed acyl moiety of 2-acyl-3-phenyl-l-menthopyrazole 2 causes diastereofacial selectivity in the reaction with secondary alcohols, and thus 2 behaves as an enantioselective acylating agent. By the use of 2.4 molar equivalents of racemic 1-phenylethanol 3a, 2-acetyl-3-phenyl-l-menthopyrazole 2a afforded (S)-1-phenylethyl acetate (S)-4aa enantioselectively and unreacted 3a was recovered with (R)-configuration. Furthermore, the inverse configurational preferences were observed to give (R)-4aa and (S)-3a by the addition of strongly basic amines, which sometimes behaved as catalysts for enolate formation from 2 and AlCl3. These dramatic changes in stereoselective preference should be useful properties of 2-acyl-3-phenyl-l-menthopyrazole 2 as an enantioselective acylating agent.
- Kashima, Choji,Mizuhara, Saori,Miwa, Yohei,Yokoyama, Yukihiro
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p. 1713 - 1719
(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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- The chemistry of acylals. Part I. The reactivity of acylals towards Grignard and organolithium reagents
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Aldehyde acylals have been prepared and reacted with Grignard and alkyllithium reagents. Acylals from formaldehyde furnished complex reaction mixtures when reacted with both reagents. Acylals of other aldehydes gave reaction mixtures that consisted mainly of an ester, generated by replacing one of the carboxy groups with the organic part of the organometallic reagent, and regenerated aldehyde. The esters were formed in the highest yields. Yields above 90% were experienced when the acylals were reacted with Grignard reagents under Barbier conditions.
- Sydnes, Leiv K.,Sandberg, Marcel
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p. 12679 - 12690
(2007/10/03)
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- The Reaction between Acyl Halides and Alcohols: Alkyl Halide vs. Ester Formation
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In the reaction between an acyl halide and an alcohol the thermodynamically favoured products are the free carboxylic acid and the alkyl halide.The initial reaction is, generally, the formation of an ester and HHal.When the alcohol is very prone to yield an alkyl cation upon protonation by HHal, formed H2O exhibited a superior reactivity and competed successfully with the alcohol for the acyl halide making, therefore, ester formation practically confined to a triggering role.But, in those cases where the cation is less easily formed, ester formation was favoured and, consequently, became the necessary elementary step towards alkyl halide formation.Tis final product, on the other hand, might be extremely slow to form in an SN2 reaction between the protonated ester function and the halide ion.In these instances, therefore, as well as in the cases when a basic solvent competes for the proton of HHal, the ester is the final product.A notable exception of the situation above outlined, is given by α-hydroxy-α-phenylbenzeneacetic acid (2y), which appears to undergo direct chlorine-hydroxyl interchange through a quaternary intermediate (E), in the end collapsing to α-chloro-α-phenyl-benzeneacetic acid (4y).Different systems were compared using CH2Cl2 as a solvent under strictly similar conditions.Some 28 different substrates were tested for reaction with AcCl (1a), whereas the action of eight acyl halides (a) against (RS)-α-methylbenzenemethanol (2n) and α-phenylbenzenemethanol (2p), as well as the effect of five different solvents on the reaction between two alcohols (2p and 2-methyl-2-propanol, 2c) with 1a, were observed.
- Strazzolini, Paolo,Giumanini, Angelo G.,Verardo, Giancarlo
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p. 217 - 254
(2007/10/02)
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- Enantiomeric Resolution of 1-Phenyl-2-propanol by Pseudomonas cepacia
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Pseudomonas cepacia hydrolyzed rac-1-phenyl-2-propyl acetate and propionate asymmetrically, affording R(-)-1-phenyl-2-propanol and the ester of S(+)-1-phenyl-2-propanol.
- Horiuchi, Kenichi,Kobashi, Kazunori,Nagata, Hidetomo,Satoh, Toshinobu,Suemitsu, Rikisaku
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p. 1330 - 1331
(2007/10/02)
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- Palatable solid pesticidal compositions of ethylene and vinyl acetate copolymer
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The invention comprises compositions in solid form of ethylene/vinyl acetate copolymer with an effective amount of bioactive agent, a protein/carbohydrate-lipid source, 0 to 20% of an edible oil and optionally an attractant, dye, preservative, adversive agent and biomarker and the use, thereof, to control pests.
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- Utility of Acyloxypyridines and Acylazoles for the Lipase-catalyzed Enantioselective Acylation of 1-Phenylethanol
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3-Acyloxypyridines and 4-acetyl-1,2,4-triazole were found to react enantioselectively with (RS)-1-phenylethanol to give (R)-1-phenethyl carboxylates in high purity, catalyzed by lipase P (from Pseudomonas fluorescens).
- Keumi, Takashi,Hiraoka, Yasumasa,Ban, Takasi,Takahashi, Ichiro,Kitajima, Hidehiko
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p. 1989 - 1992
(2007/10/02)
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- EFFECT OF THE NATURE OF THE ACYLATING AGENT ON THE ASYMMETRIC ACYLATION OF ALCOHOLS
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During the acylation of racemic 1-phenylethanol by the action of carboxylic acid anhydrides in the presence of S-(-)-N,N-dimethyl-α-phenylethylamine the unreacted alcohol is enriched in the S isomer.Its optical purity increases with increase in the steric demands of the anhydride from 2percent for acetic anhydride to 9percent for benzoic anhydride.When carboxylic acid chlorides are used, optically active 1-phenyl-1-chloroethane and bis-1-phenylethyl ether are isolated in addition to S-(-)-1-phenylethanol.
- Potapov, V. M.,Dem'yanovich, V. M.,Klebnikov, V. A.,Korovina, T. G.
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p. 1095 - 1097
(2007/10/02)
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- Mecanisme d'acetolyse d'esters d'enol styreniques
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We have studied the reaction of enol esters in acidic media: wherein Z = H, CH3, CH2Cl, CHCl2 and CCl3.The raction is first order.Log kex = α H'0 + β (H'0 = acidity function of Hammett) with α-1.A general acid catalysis is observed.Following a discussion of possible SN, AAC2 and ASE2 mechanisms, we propose an ASE2 mechanism for this reaction.
- Montheard, Jean-Pierre,Camps, Marcel,Chatzopoulos, Michel,Benzaid, Ahmed
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p. 109 - 116
(2007/10/02)
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- Search for Electron-Transfer Decomposition and the Production of Electronically Excited State Species in the Thermolysis of p-(Dimethylamino)phenyl-Substituted Dialkyl Peroxides
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Kinetic, product, and chemiluminescence (CL) studies were made with 1-ethyl tert-butyl peroxide (1), 2-propyl tert-butyl peroxide (2), and 1-phenylethyl tert-butyl peroxide (3).Activation parameters for 1 in chlorobenzene are as follows: Ea = 36.2 +/- 0.6 kcal/mol, log A = 15.45 +/- 0.32, ΔH(excit) = 35.4 +/- 0.6 kcal/mol, ΔS(excit) = 9.66 + 1.35 eu.These activation parameters are within the range expected for simple peroxide bond homolysis.The small rate acceleration by the p-dimethylamino group (k1/k3 = 2.07 at 129 deg C) is reasonable, again for the simple peroxide bond homolysis.Product studies with 1 and 2 in comparison to 3, indicate that the dimethylamino group serves as a good hydrogen atom donor.This was further substantiated by the thermolysis of 3 in the presence of N,N-dimethylaniline and 2,6-di-tert-butyl-p-cresol.CL was observed in the thermolysis of 1 and 2 in aerated o-dichlorobenzene solutions at 140 deg C.The CL quantum yield decreased significantly when solutions of 1 and 3 were purged with nitrogen or argon.No CL was observed in the thermolysis of 3, but CL was observed when N,N-dimethylaniline was added to the aerated solution.These results suggest that the CL from 1 and 2 is due primarily or entirely to autoxidation processes involving the dimethylamino group and not to electron-transfer processes involving this group and the peroxide bond.
- Richardson, William H.,Thomson, Stephen A.
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p. 4515 - 4520
(2007/10/02)
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- Acylation of Alcohols by Fatty Acid Esters in Presence of Lithium Aluminium Hydride
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A novel acylation of alcohols by fatty acid esters in the presence of lithium aluminium hydride is reported.A plausible mechanism of this acylation through the formation of a lithium aluminium tetraalkoxide complex has been suggested.
- Kumar, Shiv,Kansal, V. K.,Prashad, Mahavir,Bhaduri, A. P.
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p. 856 - 858
(2007/10/02)
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- Sodium Borohydride-Carboxylic Acid Systems - A new Method of Acylation of Alcohols, Phenols and Thiophenols
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A new method of acylation of alcohols, phenols and thiophenols in sodium borohydride-carboxylic acid system is described.A plausible mechanism of this acylation through tetraacyloxyborate derivative has been postulated.
- Prashad, Mahavir,Jigajinni, Veerappa B.
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p. 822 - 823
(2007/10/02)
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