- Acylative Dynamic Kinetic Resolution of Secondary Alcohols: Tandem Catalysis by HyperBTM and B?ckvall's Ruthenium Complex
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Non-enzymatic dynamic kinetic resolution (DKR) of secondary alcohols by enantioselective acylation using an isothiourea-derived HyperBTM catalyst and racemization of slowly reacting alcohol by B?ckvall's ruthenium complex is reported. The DKR approach fea
- Kinens, Artis,Balkaitis, Simonas,Ahmad, Omar K.,Piotrowski, David W.,Suna, Edgars
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p. 7189 - 7202
(2021/05/29)
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- 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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- Acylative Kinetic Resolution of Alcohols Using a Recyclable Polymer-Supported Isothiourea Catalyst in Batch and Flow
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A polystyrene-supported isothiourea catalyst, based on the homogeneous catalyst HyperBTM, has been prepared and used for the acylative kinetic resolution of secondary alcohols. A wide range of alcohols, including benzylic, allylic, and propargylic alcohols, cycloalkanol derivatives, and a 1,2-diol, has been resolved using either propionic or isobutyric anhydride with good to excellent selectivity factors obtained (28 examples, s values up to 600). The catalyst can be recovered and reused by a simple filtration and washing sequence, with no special precautions needed. The recyclability of the catalyst was demonstrated (15 cycles) with no significant loss in either activity or selectivity. The recyclable catalyst was also used for the sequential resolution of 10 different alcohols using different anhydrides with no cross-contamination between cycles. Finally, successful application in a continuous flow process demonstrated the first example of an immobilized Lewis base catalyst used for the kinetic resolution of alcohols in flow.
- Neyyappadath, Rifahath Mon,Chisholm, Ross,Greenhalgh, Mark D.,Rodríguez-Escrich, Carles,Pericàs, Miquel A.,H?hner, Georg,Smith, Andrew D.
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p. 1067 - 1075
(2018/02/14)
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- Kinetic resolution of secondary carbinols by a chiral N,N-4-dimethylaminopyridine derivative containing a 1,1′-binaphthyl unit: Hydrogen bonding affects catalytic activity and enantioselectivity
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We developed an acylative kinetic resolution of secondary carbinols using a binaphthyl-based N,N-4-dimethylaminopyridine (DMAP) derivative 1d with tert-Alcohol substituents. The reaction proceeded with a wide range of carbinols with moderate to high selectivity (s) (up to s = 79.5). Kinetic studies revealed that catalyst 1d was more catalytically active than the corresponding bis-methyl ether 1d′ or DMAP. Hydrogen bonding between tert-Alcohols of the catalyst and secondary carbinols was responsible for the enhanced reaction rate and high enantioselectivity.
- Fujii, Kazuki,Mitsudo, Koichi,Mandai, Hiroki,Suga, Seiji
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supporting information
p. 1081 - 1092
(2016/10/11)
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- Catalytic enantioselective acyl transfer: the case for 4-PPY with a C-3 carboxamide peptide auxiliary based on synthesis and modelling studies
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A series of 4-pyrrolidinopyridine (4-PPY) C-3 carboxamides containing peptide-based side chains have been synthesised and evaluated in the kinetic resolution of a small library of chiral benzylic secondary alcohols. A key design element was the incorporation of a tryptophan residue in the peptide side chain for promoting π-stacking between peptide side chain and the pyridinium ring of the N-acyl intermediate, in which modelling was used as a structure-based guiding tool. Together, a catalyst containing a LeuTrp-N-Boc side chain (catalyst 8) was identified that achieved s-values up to and in slight excess of 10. A transition-state model based on the modelling is proposed to explain the origin of enantioselectivity. This study establishes the usefulness of modelling as a structure-based guiding tool for enantioselectivity optimization as well as the potential for developing scalable peptide-based DMAP-type catalysts for large-scale resolution work.
- Cozett, Rudy E.,Venter, Gerhard A.,Gokada, Maheswara Rao,Hunter, Roger
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supporting information
p. 10914 - 10925
(2016/12/06)
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- Fluxionally chiral DMAP catalysts: Kinetic resolution of axially chiral biaryl compounds
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Can organocatalysts that incorporate fluxional groups provide enhanced selectivity in asymmetric transformations? To address this issue, we have designed chiral 4-dimethylaminopyridine (DMAP) catalysts with fluxional chirality. These catalysts were found
- Ma, Gaoyuan,Deng, Jun,Sibi, Mukund P.
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supporting information
p. 11818 - 11821
(2015/03/13)
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- Structure-activity relationship of dihydroimidazo-, dihydropyrimido, tetrahydrodiazepino-[2,1-b]-thiazoles, and -benzothiazoles as an acylation catalyst
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Cyclic isothioureas 1, 2, 3, and 4 were synthesized through a four-step procedure from the corresponding ortho-bromoanilines 10 via Pd- or Cu-catalyzed cyclization-benzothiazole formation. Nonbenzo analogues 7, 8, and 9 were synthesized by a condensation reaction of cyclic thioureas 15 and α-bromoacetophenones 14. Investigations of the acylation reactions of 1-phenylethanol with acid anhydrides in the presence of these cyclic isothiourea catalysts revealed their structure-activity relationships. Remarkable electronic effects resulting from substituent(s) on a benzo or phenyl moiety and the influence of the size of the annulating ring were observed. Introduction of an electron-donating substituent(s) enhanced the reaction rate. A few substitution effects on chiral catalysts of type 3 and 7 were also studied.
- Okamoto, Sentaro,Sakai, Yuzo,Watanabe, Saki,Nishi, Shohei,Yoneyama, Aya,Katsumata, Hitomi,Kosaki, Yu,Sato, Rumi,Shiratori, Megumi,Shibuno, Misuzu,Shishido, Tsukasa
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p. 1909 - 1912
(2014/03/21)
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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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- Design, synthesis, and evaluation of a helicenoidal DMAP lewis base catalyst
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The design, synthesis, and study of a helical dialkylaminopyridine Lewis base catalyst is reported. Helical DMAP analogue 4 is based upon a helicenoid structure and displays good to excellent levels of selectivity (S ≤ 116) in the kinetic resolution of chiral secondary alcohols. Catalyst 4 displays excellent reactivity with exceptionally low loadings of 0.05 mol % effecting practical levels of selectivity in kinetic resolutions.(Figure Presented)
- Crittall, Matthew R.,Rzepa, Henry S.,Carbery, David R.
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supporting information; experimental part
p. 1250 - 1253
(2011/04/25)
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- Organocatalysis with azahelicenes: The first use of helically chiral pyridine-based catalysts in the asymmetric acyl transfer reaction
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The successful utilisation of a helicene-based organocatalyst in acylative kinetic resolution of racemic secondary alcohol was described. Employing rac-1-phenylethanol, optically pure (-)-(M)-2-aza[6]helicene (5-20 mole %), isobutyric anhydride and N-ethyldiisopropylamine in chloroform at 22-40 °C, an asymmetric acyl transfer reaction took place overwhelming the uncatalysed background process. Moderate reactivity as well as selectivity factor (s = 9, 10) were observed. An effective control of the enantiodiscriminating step in acylative kinetic resolution by the helically chiral organocatalyst was proven for the first time.
- Samal, Michal,Misek, Jiri,Stara, Irena G.,Stary, Ivo
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scheme or table
p. 1151 - 1159
(2010/04/28)
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- An enantiopure cyclophane-type imidazole with no central but planar chirality
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An enantiopure cyclophane-type imidazole with planar chirality was synthesized, which was expected to serve as a useful component for the development of novel chiral molecular devices, such as ligands, organocatalysts, and receptors.
- Ishida, Yasuhiro,Iwasa, Eriko,Matsuoka, Yuki,Miyauchi, Hiroyuki,Saigo, Kazuhiko
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supporting information; experimental part
p. 3401 - 3403
(2009/12/07)
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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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- New class of pyridine catalyst having a conformation switch system: Asymmetric acylation of various sec-alcohols
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We have developed a new class of pyridine catalyst for asymmetric acylation of sec-alcohols having a conformation switch system in which interconversion between self-complexation and uncomplexation is induced by acylation and deacylation steps, respectively. Kinetic resolution of various sec-alcohols is performed by the asymmetric acylation with isobutyric anhydride using 0.05 to 0.5 mol % catalyst 1a with s values of up to 30. In addition, dl-diols are also resolved in a similar manner in good selectivity. Moreover, asymmetric desymmetrization of meso-1,X-diols (X = 2-6) are achieved in the presence of 0.5-5 mol % catalyst 1a. A working model for the reaction mechanism is proposed on the basis of the 1H NMR measurements, X-ray structural analyses, and AM1 and DFT calculations, where the conformation switch system governed by an intramolecular cation-π interaction between a pyridinium ring and a thiocarbonyl group would play a key role to attain both good selectivity and high catalytic activity.
- Yamada, Shinji,Misono, Tomoko,Iwai, Yuko,Masumizu, Ayako,Akiyama, Yukiko
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p. 6872 - 6880
(2007/10/03)
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- Enantioselective acylation of secondary alcohols catalyzed by chiral N-heterocyclic carbenes
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(Chemical Equation Presented). The synthetic utility of chiral N-heterocyclic carbenes, which have been used mainly in transition metal-catalyzed reactions as a ligand, was demonstrated by the enantioselective acylation of secondary alcohols.
- Kano, Taichi,Sasaki, Kouji,Maruoka, Keiji
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p. 1347 - 1349
(2007/10/03)
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- Kinetic resolution of sec-alcohols by a new class of pyridine catalysts having a conformation switch system
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The catalysts having a conformation switch system induced by acylation and deacylation serve as asymmetric acylating catalysts of sec-alcohols. The kinetic resolution of various sec-alcohols resulted in good to excellent selectivities in the presence of 0.5 to 0.05 mol % of catalyst 1a. The conformation switch system plays a key role to attain both good selectivity and high catalytic activity.
- Yamada, Shinji,Misono, Tomoko,Iwai, Yuko
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p. 2239 - 2242
(2007/10/03)
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- A highly enantioselective phosphabicyclooctane catalyst for the kinetic resolution of benzylic alcohols
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A new class of chiral phosphines belonging to the P-aryl-2-phosphabicyclo[3.3.0]octane family (PBO) has been prepared by enantioselective synthesis starting from lactate esters and 2,2-dimethylcy-clopentanone enolate 5. A selective enolate alkylation method has been developed for preparation of 9 and 10 using a chelating ester substituent in the triflate alkylating agent 11. Subsequent conversion to the PBO catalysts 2 and 39 relies on a diastereoselective cyclization from the cyclic sulfate 17 and LiPHAr to afford the more hindered endo-aryl phosphines. These phosphines function as efficient catalysts for the kinetic resolutions of aryl alkyl carbinols by benzoylation (16, 21, 22) or iso-butyroylation in the case of the less hindered aryl alkyl carbinol substrates. With o-substituted aryl alkyl carbinols, the enantioselectivities exceed 100, and s = 380 ± 10 has been demonstrated in the case of methyl mesityl carbinol. The PBO- catalyzed acylations probably involve a P-acylphosphonium carboxylate intermediate and a tightly ion paired transition state.
- Vedejs, Edwin,Daugulis, Olafs
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p. 4166 - 4173
(2007/10/03)
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- Axially chiral analogues of 4-(dimethylamino)pyridine: Novel catalysts for nonenzymatic enantioselective acylations
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A concise seven-step synthesis of atropisomeric 3-aryl analogues of DMAP from 4-pyridone 8 has been developed. A representative compound of this class, biaryl (±)-15, has been resolved using CSP HPLC and shown to be an efficient nucleophilic catalyst for kinetic resolution of a series of secondary alcohols on both an analytical and preparative scale (stereoselectivity factors, s = 8.9-29).
- Spivey, Alan C.,Fekner, Tomasz,Spey, Sharon E.
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p. 3154 - 3159
(2007/10/03)
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