- Application of axially dissymmetric ligand recoverable with fluorous solvent as a chiral auxiliary
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(Ra)-(R)2-2,2′-Bis(1-hydroxy-1H-perfluorooctyl)biphenyl ((Ra)-(R)2-1c), which is an axially dissymmetric ligand with two chiral centers, works as a good chiral auxiliary for asymmetric aldol reaction. Thus, the reaction of monopropan
- Omote, Masaaki,Nishimura, Yuji,Sato, Kazuyuki,Ando, Akira,Kumadaki, Itsumaro
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Read Online
- Copper-Catalyzed Enantioselective Reductive Aldol Reaction of α,β-Unsaturated Carboxylic Acids to Alkyl Aryl Ketones: Silanes as Activator and Transient Protecting Group
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The first enantioselective reductive aldol reaction of unprotected α,β-unsaturated carboxylic acids was developed by employing a copper/bisphosphine catalyst. The reaction features in situ protection and activation of an α,β-unsaturated carboxylic acid by a hydrosilane. The copper enolate formed in situ reacts with an alkyl aryl ketone to afford the β-hydroxy carboxylic acid with excellent enantioselectivity (up to 99 % ee). The corresponding gram-scale reaction with a low catalyst loading and the derivatization of the β-hydroxy carboxylic acids highlight the practicality of this transformation.
- Suzuki, Hirotsugu,Yoneoka, Kenji,Kondo, Sora,Matsuda, Takanori
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supporting information
(2022/01/26)
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- Visible-Light-Driven, Metal-Free Divergent Difunctionalization of Alkenes Using Alkyl Formates
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In recent decades, difunctionalization of alkenes has received considerable attention as an efficient and straightforward way to increase molecular complexity. However, examples of the difunctionalization of alkenes initiated by the intermolecular addition of alkoxycarbonyl radicals providing substituted alkanoates are still rare. Herein, we present the visible light-driven metal-free divergent difunctionalization of alkenes triggered by the intermolecular addition of alkoxycarbonyl radicals under ambient conditions. Employing alkyl formates as precursors of alkoxycarbonyl radicals and 4CzIPN as the photocatalyst, a variety of substituted alkanoates, including β-alkoxy, β-hydroxy, β-dimethoxymethoxy, and β-formyloxy alkanoates, could be facilely accessed with high functional group tolerance and high efficiency. Moreover, the mechanism study revealed that β-hydroxy alkanoates were generated by a selective decomposition of orthoformates promoted by the N-alkoxyazinium salt.
- Zheng, Ming,Hou, Jing,Zhan, Le-Wu,Huang, Yan,Chen, Ling,Hua, Li-Li,Li, Yan,Tang, Wan-Ying,Li, Bin-Dong
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p. 542 - 553
(2021/01/14)
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- Fe-Catalyzed Anaerobic Mukaiyama-Type Hydration of Alkenes using Nitroarenes
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Hydration of alkenes using first row transition metals (Fe, Co, Mn) under oxygen atmosphere (Mukaiyama-type hydration) is highly practical for alkene functionalization in complex synthesis. Different hydration protocols have been developed, however, control of the stereoselectivity remains a challenge. Herein, highly diastereoselective Fe-catalyzed anaerobic Markovnikov-selective hydration of alkenes using nitroarenes as oxygenation reagents is reported. The nitro moiety is not well explored in radical chemistry and nitroarenes are known to suppress free radical processes. Our findings show the potential of cheap nitroarenes as oxygen donors in radical transformations. Secondary and tertiary alcohols were prepared with excellent Markovnikov-selectivity. The method features large functional group tolerance and is also applicable for late-stage chemical functionalization. The anaerobic protocol outperforms existing hydration methodology in terms of reaction efficiency and selectivity.
- Bhunia, Anup,Bergander, Klaus,Daniliuc, Constantin Gabriel,Studer, Armido
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supporting information
p. 8313 - 8320
(2021/03/08)
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- Manganese-Catalyzed anti-Selective Asymmetric Hydrogenation of α-Substituted β-Ketoamides
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A Mn-catalyzed diastereo- and enantioselective hydrogenation of α-substituted β-ketoamides has been realized for the first time under dynamic kinetic resolution conditions. anti-α-Substituted β-hydroxy amides, which are useful building blocks for the synthesis of bioactive molecules and chiral drugs, were prepared in high yields with excellent selectivity (up to >99 percent dr and >99 percent ee) and unprecedentedly high activity (TON up to 10000). The origin of the excellent stereoselectivity was clarified by DFT calculations.
- Ding, Kuiling,Han, Zhaobin,Wang, Zheng,Zhang, Linli
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supporting information
p. 15565 - 15569
(2020/07/06)
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- Ni-Catalyzed chemoselective alcoholysis of: N -acyloxazolidinones
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Although N-acyloxazolidinone-based (catalytic) asymmetric synthetic methodologies occupy an important position in modern organic synthesis, the catalytic cleavage of a chiral auxiliary remains underdeveloped. We report the Ni(cod)2/bipyr.-catalyzed alcoholysis of N-acyloxazolidinones to deliver esters. The reaction is broad in scope for both N-acyloxazolidinone substrates and alcohol nucleophiles, and displays good functional group tolerance and excellent chemoselectivity. A gram-scale methanolysis allowed the enantioselective synthesis of the C22-C26 segment of a close analogue of the potent immunosuppressant agent FK506.
- Huang, Pei-Qiang,Geng, Hui
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supporting information
p. 593 - 599
(2018/02/14)
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- Stereoselective Construction of Entire Diastereomeric Stereotetrads Based on an Asymmetric Morita–Baylis–Hillman Reaction
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A method for the enantio- and diastereoselective construction of all possible stereoisomers of a polypropionate stereotetrad having four contiguous stereogenic centers has been developed. The approach features an iterative sequence of cinchona-alkaloid-ca
- Yoshimura, Hikaru,Ishihara, Jun,Hatakeyama, Susumi
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p. 2719 - 2729
(2017/05/29)
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- Chiral ferrocene P-N-N ligand with high steric hindrance, and preparation method and application thereof
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The invention provides a chiral ferrocene P-N-N ligand compound with high steric hindrance, and a preparation method and application thereof, specifically application of the chiral ferrocene P-N-N ligand compound to asymmetric catalytic hydrogenation of beta-keto ester compounds. The preparation method for the chiral ferrocene P-N-N ligand compound with high steric hindrance comprises the following steps: dissolving a chiral ferrocenephosphine-amine compound and a pyridone compound in a reaction solvent; adding active Al2O3 and a dehydrating agent; carrying out a reflux condensation reaction; then carrying out re-dissolving in absolute ethyl alcohol after filtering and desolventizing; adding a palladium/carbon catalyst and carrying out a hydrogenation reaction in an autoclave under a certain reaction pressure; and then successively carrying out filtration, desolventizing and column chromatographic treatment so as to obtain the desired chiral ferrocene P-N-N ligand compound with high steric hindrance. The chiral ferrocene P-N-N ligand compound with high steric hindrance in the invention can be used for asymmetric catalytic hydrogenation of beta-keto ester and can realize high-yield, high-diastereoselectivity high-enantioselectivity preparation of chiral beta-hydroxy ester.
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Paragraph 0121-0124
(2018/01/13)
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- Direct Catalytic Asymmetric Aldol Reaction of α-Alkylamides
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A catalytic asymmetric aldol reaction directly employing amides as latent enolates has remained elusive because of the resistance of amides to enolization. A direct aldol reaction of α-alkylamides without any electron-withdrawing group harnessed by specif
- Liu, Zijian,Takeuchi, Toshifumi,Pluta, Roman,Arteaga Arteaga, Fernando,Kumagai, Naoya,Shibasaki, Masakatsu
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supporting information
p. 710 - 713
(2017/02/10)
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- Sterically Hindered Chiral Ferrocenyl P,N,N-Ligands for Highly Diastereo-/Enantioselective Ir-Catalyzed Hydrogenation of α-Alkyl-β-ketoesters via Dynamic Kinetic Resolution
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A new class of sterically hindered chiral ferrocenyl P,N,N-ligands have been prepared through a two-step transformation from (Sc,Rp)-PPFNH2, in which a new (R)-stereogenic center at the pyridinylmethyl position was generated in high diastereoselectivity. With these newly developed P,N,N-ligands, Ir-catalyzed asymmetric hydrogenation of various α-alkyl-substituted β-aryl-β-ketoesters via dynamic kinetic resolution has been realized in high diastereo- and enantioselectivities for the first time, which led to a variety of optically active anti-β-hydroxyesters in up to 99% ee. The study indicated that the additional stereocenter at the pyridinylmethyl position of these ligands is crucial to realize this hydrogenation.
- Hou, Chuan-Jin,Hu, Xiang-Ping
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supporting information
p. 5592 - 5595
(2016/11/17)
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- Asymmetric reductive aldol-type reaction with carbonyl compounds using dialkyl tartrate as a chiral ligand
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An asymmetric reductive aldol-type reaction of α,β-unsaturated esters with carbonyl compounds using Rh catalyst and Et2Zn was investigated. A chiral zinc complex from α,β-unsaturated ester was easily generated as the key intermediate from Et2Zn and Wilkin
- Isoda, Motoyuki,Sato, Kazuyuki,Tokura, Yoriko,Tarui, Atsushi,Omote, Masaaki,Ando, Akira
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p. 956 - 961
(2014/12/11)
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- Polymer-supported PPh3 as a reusable organocatalyst for the Mukaiyama aldol and Mannich reaction
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An easily accessible and user-friendly polymer-supported phosphine PS-PPh3 catalyzes the aldol reaction of aldehydes and imines. A broad range of aldehydes and imines could be applied under mild conditions using 5-10 mol% PS-PPh3. PS-PPh3 was easily recovered and reused with minimal loss of activity. This journal is the Partner Organisations 2014.
- Matsukawa, Satoru,Fukazawa, Kazuki,Kimura, Junya
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p. 27780 - 27786
(2014/07/21)
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- Regio-and enantioselective bioreduction of methyleneketoesters using both polymeric resin and cellulose matrix
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Methyleneketoesters were prepared in >90% yield by performing an IBX oxidation of Morita-Baylis-Hillman adducts. A methodology was developed to achieve methyl 3-aryl-3-keto-2-methylenepropanoate reduction using a screening of yeast strains in three different reaction procedures to obtain products with both high yield and diastereoselectivity. The reactions conducted in water provided inferior yields (50%) for substrates 2b-c. Employing Amberlite XAD7HP which was a substrate reservoir that also immediately extracted the products from the reaction medium after their formation, syn-4a-c and anti-4a-c were isolated in 60-70% yield, with high stereoselectivity (98-99% ee). The best results were obtained using substrates adsorbed on filter paper which provided products yields above 70%, a 99% ee and a diastereomoeric ratio (syn-4: anti-4) 9:1. Cellulose matrix has excellent potential to be successfully employed in general biocatalytic reactions.
- Chaves, Michel R.B.,Moran, Paulo J.S.,Rodrigues, J. Augusto R.
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- Reductive aldol-type reaction of α,β-unsaturated esters with aldehydes or ketones in the presence of Rh catalyst and Et2Zn
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The reaction of RhCl(PPh3)3 with Et2Zn easily generated a rhodium-hydride complex (Rh-H) that added to α,β-unsaturated esters to form rhodium enolate complexes by formal 1,4-reduction. These rhodium enolates gave the corre
- Sato, Kazuyuki,Isoda, Motoyuki,Tokura, Yoriko,Omura, Keiko,Tarui, Atsushi,Omote, Masaaki,Kumadaki, Itsumaro,Ando, Akira
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p. 5913 - 5915
(2013/10/21)
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- Cyclopropenone catalyzed substitution of alcohols with mesylate ion
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The cyclopropenone catalyzed nucleophilic substitution of alcohols by methanesulfonate ion with inversion of configuration is described. This work provides an alternative to the Mitsunobu reaction that avoids the use of azodicarboxylates and generation of hydrazine and phosphine oxide byproducts. This transformation is shown to be compatible with a range of functionality. A cyclopropenone scavenge strategy is demonstrated to aid purification.
- Nacsa, Eric D.,Lambert, Tristan H.
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supporting information
p. 38 - 41
(2013/03/28)
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- Solvent- or temperature-controlled diastereoselective aldol reaction of methyl phenylacetate
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Unlike the enolboration-aldolization of methyl propanoate, the choice of either the solvent or temperature determines the diastereoselectivity during the enolboration-aldolization of methyl phenylacetate. In CH2Cl 2, the reaction favors the anti-pathway at -78 °C and the syn-pathway at rt. Conversely, the reaction produces the anti-isomer up to rt and the syn-isomer at refluxing temperatures in nonpolar solvents.
- Ramachandran, P. Veeraraghavan,Chanda, Prem B.
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supporting information
p. 4346 - 4349
(2012/10/29)
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- Reductive Reformatsky-Honda reaction of α,β-unsaturated esters: Facile formation of 1,3-dicarbonyl compounds and β-hydroxy esters
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The reaction of tris(triphenylphosphine)rhodium chloride [RhCl(PPh 3)3] with diethylzinc (Et2Zn) easily afforded a rhodium-hydride complex that effects the 1,4-reduction of α,β- unsaturated esters to give rhodium enolates. Formation of the rhodium enolate is followed by transmetalation with the zinc species to give a Reformatsky-type reagent, and this reacts with various acid chlorides at the α-position to give β-keto esters. The Reformatsky-type reagent also reacts with various electrophiles such as aldehydes, ketones and acid anhydrides to give the corresponding products in which the electrophiles were introduced reductively at the α-position of α,β-unsaturated esters. Copyright
- Sato, Kazuyuki,Isoda, Motoyuki,Ohata, Shizuka,Morita, Shuhei,Tarui, Atsushi,Omote, Masaaki,Kumadaki, Itsumaro,Ando, Akira
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supporting information; scheme or table
p. 510 - 514
(2012/04/23)
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- Double molecular recognition with aminoorganoboron complexes: Selective alcoholysis of β-dicarbonyl derivatives
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Double duty: Aminoorganoboron (AOB) complexes recognize alcohol and β-dicarbonyl units, and thereby facilitate chemo- and site-selective alcoholysis of the latter (see scheme). The complex activates both reaction partners. This strategy enables C-C, C-N, and C-O bond cleavage in addition/elimination reactions under near neutral pH conditions and provides a new method for functional group conversions. Copyright
- Oishi, Shunsuke,Saito, Susumu
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supporting information; experimental part
p. 5395 - 5399
(2012/06/18)
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- Influence of chiral thiols on the diastereoselective synthesis of γ-lactams from cyclic anhydrides
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The synthesis of γ-lactams from both four-component and imine-anhydride reactions is reported. The synthesis of 2-phenylcyclohexanethiol is described and this compound was evaluated along with an additional seven chiral thiols. A range of selectivity and yields was observed and comparisons to established reactions are made in order to account for the observed reactivity.
- Younai, Ashkaan,Fettinger, James C.,Shaw, Jared T.
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scheme or table
p. 4320 - 4327
(2012/07/28)
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- Development of a catalytic platform for nucleophilic substitution: Cyclopropenone-catalyzed chlorodehydration of alcohols
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Cyclopropenone makes the switch: 2,3-Bis-(p-methoxyphenyl)cyclopropenone is a highly efficient catalyst for the chlorodehydration of 20 diverse alcohol substrates (see scheme; X=Cl). With oxalyl chloride as catalytic activator, this nucleophilic substitution proceeded through cyclopropenium-activated intermediates and resulted in complete stereochemical inversion in substrates with chiral centers.
- Vanos, Christine M.,Lambert, Tristan H.
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supporting information; experimental part
p. 12222 - 12226
(2012/02/02)
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- Importance of open structure of nonmetal based catalyst in hydrogen bond promoted methanolysis of activated amide: Structure dynamics between monomer and dimer enabling recombinant covalent, dative, and hydrogen bonds
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(Figure Presented) We disclosed structural dynamics hidden behind a series of aminoorganoboron (AOB) compounds that involved a recombinant of covalent, dative, and hydrogen bonds. A combination process occurred via reorganizing elements and bonds between
- Oishi, Shunsuke,Yoshimoto, Junichi,Saito, Susumu
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supporting information; experimental part
p. 8748 - 8749
(2009/12/04)
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- Synthesis of chiral 2-hydroxy-1-methylpropanoates by rhodium-catalyzed stereoselective hydrogenation of α-(hydroxymethyl)-acrylate derivatives
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The synthesis of chiral 3-hydroxy-2-methylpropanoic acid esters (e.g., "Roche ester" 3a) based on the rhodium-catalyzed stereoselective hydrogenation of Baylis-Hillman reaction products was investigated. Full conversions and enantioselectivities of up to 99% at a substrate/catalyst ratio of up to 500/1 were achieved by application of bisphospholanes of the catASium M series as ancillary ligands. An interesting kinetic resolution was observed by the diastereoselective hydroxy-directed hydrogenation of related racemic β-branched precursors affording mainly anti-isomers with up to 96%ee.
- Holz, Jens,Schaeffner, Benjamin,Zayas, Odalys,Spannenberg, Anke,Boerner, Armin
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scheme or table
p. 2533 - 2543
(2009/09/25)
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- Ti-direct, powerful, stereoselective aldol-type additions of esters and thioesters to carbonyl compounds: Application to the synthesis and evaluation of lactone analogs of jasmone perfumes
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An efficient TiCl4-Et3N or Bu3N-promoted aldol-type addition of phenyl and thiophenyl esters or thioaryl esters with aldehydes and ketones was performed (total 46 examples). The present method is advantageous from atom-economical and cost-effective viewpoints; good to excellent yields, moderate to good syn-selectivity, substrate variations, reagent availability, and simple procedures. Utilizing the present reaction as the key step, an efficient short synthesis of three lactone [2(5H)-furanone] analogs of jasmine perfumes was performed. Among them, the lactone analog of cis-jasmone had a unique perfume property (tabac). The Royal Society of Chemistry.
- Nagase, Ryohei,Matsumoto, Noriaki,Hosomi, Kohei,Higashi, Takahiro,Funakoshi, Syunsuke,Misaki, Tomonori,Tanabe, Yoo
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p. 151 - 159
(2008/03/28)
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- Ni-catalyzed activation of α-chloroesters: a simple method for the synthesis of α-arylesters and β-hydroxyesters
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Coupling reactions of α-chloroesters with aryl halides (α-arylation) or carbonyl compounds (Reformatsky) using nickel catalyst allow, under mild conditions, the preparation of various functionalized aryl propionic acid derivatives or β-hydroxyesters. In the synthesis of aryl propionic acid derivatives, the process is efficient with aryl halides bearing either electron-withdrawing or electron-donating groups.
- Durandetti, Muriel,Gosmini, Corinne,Périchon, Jacques
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p. 1146 - 1153
(2007/10/03)
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- Iron-catalysed Reformatsky-type reactions
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A Reformatsky-type reaction has been developed using iron catalysis in acetonitrile or DMF. Reduction of iron(II) bromide by manganese metal in acetonitrile provides a low-valent iron catalyst, which is the active species; under these conditions, α-chloro
- Durandetti, Muriel,Perichon, Jacques
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p. 1542 - 1548
(2007/10/03)
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- Copper(I)-catalyzed enantio- and diastereoselective tandem reductive aldol reaction
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(Chemical Equation Presented) An efficient method for the enantioselective tandem reductive aldol reaction of methyl acrylate with aldehydes is reported. By using a copper-(I) precursor and a proper diphosphane ligand, high reactivities can be reached, with TOF up to 40 000 h-1. Taniaphos-based ligands lead to enantioselectivities of up to 97% in the case of the major syn diastereoisomer.
- Chuzel, Olivier,Deschamp, Julia,Chausteur, Christophe,Riant, Olivier
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p. 5943 - 5946
(2007/10/03)
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- 4-substituted-phenyl(bisoxazoline)-rhodium complexes: Efficiency in the catalytic asymmetric reductive aldol reaction
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Electronic effects of the substituents on the phenyl ring of the phenyl(bisoxazoline) ligand skeleton of rhodium catalysts was examined in the asymmetric reductive aldol reactions of acrylates and aldehydes. The electron-withdrawing NO2 group o
- Shiomi, Takushi,Ito, Jun-Ichi,Yamamoto, Yoshihiko,Nishiyama, Hisao
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p. 5594 - 5600
(2008/02/04)
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- Aldol reaction of trimethylsilyl enolate with aldehyde catalyzed by pyridine N-oxide as a Lewis base catalyst
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Aldol reaction of trimethylsilyl enolate with aldehydes proceeded in the presence of a catalytic amount of a Lewis base, pyridine N-oxide, and lithium chloride in DMF at room temperature. Not only aryl aldehydes but also alkyl aldehydes provided the aldol
- Hagiwara, Hisahiro,Inoguchi, Hideyuki,Fukushima, Masakazu,Hoshi, Takashi,Suzuki, Toshio
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p. 2388 - 2390
(2007/10/03)
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- High performance of Rh(Phebox) catalysts in asymmetric reductive aldol reaction: High anti-selectivity
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Chiral rhodium(bisoxazolinylphenyl) complexes (1 mol %) efficiently catalyze the asymmetric reductive aldol reaction of aldehydes and α,β-unsaturated esters at 50 °C for ca. 0.5-1.0 h with several hydrosilanes to give the corresponding β-hydroxypropionates with extremely high anti-selectivity (up to 98%) and enantioselectivity (up to 96% ee). The stereochemical outcome is likely due to a chairlike cyclic transition state involving rhodium-(E)-enolate. Copyright
- Nishiyama, Hisao,Shiomi, Takushi,Tsuchiya, Yasunori,Matsuda, Isamu
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p. 6972 - 6973
(2007/10/03)
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- Lewis base activation of Lewis acids: Catalytic, enantioselective addition of silyl ketene acetals to aldehydes
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The concept of Lewis base activation of Lewis acids has been reduced to practice for catalysis of the aldol reaction of silyl ketene acetals and silyl dienol ethers with aldehydes. The weakly acidic species, silicon tetrachloride (SiCl4), can b
- Denmark, Scott E.,Beutner, Gregory L.,Wynn, Thomas,Eastgate, Martin D.
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p. 3774 - 3789
(2007/10/03)
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- Lewis Acid Catalysis in Supercritical Carbon Dioxide. Use of Poly(ethylene glycol) Derivatives and Perfluoroalkylbenzenes As Surfactant Molecules Which Enable Efficient Catalysis in ScCO2
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Lewis acid catalysis in supercritical carbon dioxide (CO2) was investigated. While solubility of most organic materials is low in scCO 2, poly(ethylene glycol) derivatives or perfluoroalkylbenzenes were found to work as surfactants to dissolve organic materials in scCO2. In the presence of these molecules, Lewis acid catalyzed organic reactions such as aldol-, Mannich-, and Friedel-Crafts-type reactions proceeded smoothly in scCO2. Formation of emulsions was observed in these reactions, and the systems were studied in detail.
- Komoto, Ichiro,Kobayashi, Shu
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p. 680 - 688
(2007/10/03)
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- Lithium acetate-catalyzed aldol reaction between aldehyde and trimethylsilyl enolate in anhydrous or water-containing N,N-dimethylformamide
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Lithium acetate (AcOLi)-catalyzed aldol reactions between trimethylsilyl enolates and aldehydes proceed smoothly in anhydrous DMF or pyridine to afford the corresponding aldols in good to high yields under weakly-basic conditions (Tables 1-5). This cataly
- Nakagawa, Takashi,Fujisawa, Hidehiko,Nagata, Yuzo,Mukaiyama, Teruaki
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p. 1555 - 1567
(2007/10/03)
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- An efficient stereoselective synthesis of (E)- and (Z)-trisubstituted alkenes from unactivated Baylis-Hillman adducts using NaBH4/CuCl 2·2H2O
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A convenient and facile stereoselective synthesis of (E)- and (Z)-trisubstituted alkenes has been achieved by treatment of unactivated Baylis-Hillman adducts with NaBH4 in the presence of CuCl 2·2H2O at room temperature for 15 min.
- Das, Biswanath,Banerjee, Joydeep,Majhi, Anjoy,Mahender, Gurram
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p. 9225 - 9227
(2007/10/03)
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- Lithium acetate-catalyzed aldol reaction between aldehyde and trimethylsilyl enolate
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Lithium acetate-catalyzed aldol reaction between trimethylsilyl enolates and aldehydes proceeded smoothly in a DMF or pyridine solvent to afford the corresponding aldols in good to high yields under weakly basic conditions.
- Nakagawa, Takashi,Fujisawa, Hidehiko,Mukaiyama, Teruaki
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p. 462 - 463
(2007/10/03)
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- Iron-mediated electrochemical reaction of α-chloroesters with carbonyl compounds
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(Matrix presented) Reformatsky-type reactions have been performed efficiently using an electroassisted iron-complex catalysis. Valuable product such as β-hydroxyesters, ketones or nitriles are thus prepared with high yields.
- Durandetti, Muriel,Meignein, Clothilde,Perichon, Jacques
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p. 317 - 320
(2007/10/03)
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- The effect of Lewis acidity in carbonyl coupling reactions
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Relative Lewis acidities of (+)-Pr(hfc)3, (+)-Eu(hfc)3 and (+)-Yb(hfc)3 have been estimated by measuring the induced chemical shift of the aldehydic proton of benzaldehyde in the presence of these lanthanide complexes. The order has been estimated as Pr(hfc)3>Yb(hfc)3?Eu(hfc)3. These lanthanide complexes and a few other non-lanthanide compounds such as BBr3, BF3.OEt2, TiCl4 and SnCl4 have been used as Lewis acid catalysts in a coupling reaction between an aldehyde and (E)-1-methoxy-1-(trimethylsilyloxy)propene. Results show that the chemical yield of the reaction is in the same order as the Lewis acidity of the catalyst used. The observation is in consonant with the expectation that higher is the Lewis acidity more should be degree of activation of the carbonyl base by the Lewis acid.
- Purkayastha, Biswajit,Deka, Krishna S.,Deka, Dibakar C.
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p. 938 - 940
(2007/10/03)
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- Highly anti-selective asymmetric aldol reactions using chiral zirconium catalysts. Improvement of activities, structure of the novel zirconium complexes, and effect of a small amount of water for the preparation of the catalysts
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Catalytic asymmetric aldol reactions of silyl enol ethers with aldehydes (Mukaiyama aldol reactions) have been performed using novel chiral zirconium catalysts. The reactions proceeded in high yields under mild conditions, and anti-adducts were obtained i
- Yamashita, Yasuhiro,Ishitani, Haruro,Shimizu, Haruka,Kobayashi, Shu
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p. 3292 - 3302
(2007/10/03)
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- Lithium pyrrolidone catalyzed aldol reaction between aldehyde and trimethylsilyl enolate
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Lithium pyrrolidone catalyzed aldol reaction between trimethylsilyl enolates and aldehydes proceeded smoothly in a DMF or pyridine solvent to afford the corresponding aldols under weakly basic conditions.
- Fujisawa, Hidehiko,Mukaiyama, Teruaki
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p. 858 - 859
(2007/10/03)
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- 1-Dodecyloxy-4-perfluoroalkylbenzene as a Novel Efficient Additive in Aldol Reactions and Friedel-Crafts Alkylation in Supercritical Carbon Dioxide
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matrix presented 1-Dodecyloxy-4-perfluoroalkylbenzenes accelerated organic reactions such as aldol-type reactions and Friedel-Crafts alkylation in supercritical carbon dioxide. The perfluoroalkylbenzene worked as a surfactant in the system, and formation of emulsions during the reactions was observed.
- Komoto, Ichiro,Kobayashi, Shu
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p. 1115 - 1117
(2007/10/03)
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- Magnesium Bromide Mediated Highly Diastereoselective Heterogeneous Hydrogenation of Olefins
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(Matrix Presented) Palladium on carbon combined with magnesium bromide catalyzed hydrogenation of Baylis-Hillman olefins to afford the corresponding aldol derivatives in a highly syn-diastereoselective manner is described.
- Bouzide, Abderrahim
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p. 1347 - 1350
(2007/10/03)
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- Isotopically chiral probes for in situ high-throughput asymmetric reaction analysis
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In this work, we disclose a high-throughput screening assay for in situ analysis of enantioselection. The assay makes use of enantioenriched probe substrates that are isotopically chiral by virtue of a 13C isotope label. Upon catalytic asymmetric transformation, the carbon labels in the pseudoenantiomeric reaction products are in alternate diastereotopic environments and therefore lead to unique resonances. Simple integration allows for calculation of conversion and enantioselection. Copyright
- Evans, Michael A.,Morken, James P.
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p. 9020 - 9021
(2007/10/03)
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- Addition of α-halocarboxylic acid esters to para-substituted benzaldehydes in the presence of pentacarbonyliron
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Pentacarbonyliron promotes addition of α-halocarboxylic acid esters at the carbonyl group of benzaldehyde and its para-substituted analogs. The substituent in the benzene ring strongly affects the process.
- Terent'ev,Vasil'eva,Kuz'mina,Mysova,Chakhovskaya
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p. 1273 - 1275
(2007/10/03)
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- Generation of (E)-Silylketene acetals in a Rhodium-DuPhos catalyzed two-step reductive aldol reaction
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(equation presented) Mechanistic studies employing in situ NMR analysis implicate intermediate silicon enolates as reactive intermediates in the Rh-DuPhos catalyzed two-step reductive aldol reaction with Cl2MeSiH. These enolates undergo noncata
- Zhao, Cun-Xiang,Bass, Jonathan,Morken, James P.
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p. 2839 - 2842
(2007/10/03)
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- Lewis acid catalysis in a supercritical carbon dioxide (scCO2)-poly(ethylene glycol) derivatives (PEGs) system: Remarkable effect of PEGS as additives on reactivity of Ln(OTf)3-catalyzed Mannich and aldol reactions in scCO2
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Use of poly(ethylene glycol) derivatives (PEGs) as additives in supercritical carbon dioxide (scCO2) was found to be effective for Mannich and aldol reactions of silyl enolates with aldehydes and imines, and formation of emulsions was observed in these systems.
- Komoto,Kobayashi
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p. 1842 - 1843
(2007/10/03)
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- An electrochemical coupling of organic halide with aldehydes, catalytic in chromium and nickel salts. the Nozaki-Hiyama-Kishi reaction.
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[reaction: see text] Electrochemical arylation of arenecarboxaldehydes using an iron sacrificial anode in the presence of chromium and nickel catalysts afforded the corresponding arylated secondary alcohols in moderate to good yields. The chromium and nickel salts as catalysts are obtained by oxidation of a stainless steel rod during a preelectrolysis in 7% and 3%, respectively. The process was also applied to the addition of vinyl halide, allyl acetate, or alpha-chloroester to aromatic aldehydes.
- Durandetti,Nedelec,Perichon
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p. 2073 - 2076
(2007/10/03)
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- Enantio- and diastereoselective reductive aldol reactions with iridium-pybox catalysts
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(formula presented) A catalytic amount of [(cod)IrCl]2 and indane-pybox converts diethylmethylsilane, methyl acrylate, and certain aldehydes to the derived reductive aldol adduct with good enantio- and diastereocontrol.
- Zhao, Cun-Xiang,Duffey, Matthew O.,Taylor, Steven J.,Morken, James P.
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p. 1829 - 1831
(2007/10/03)
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- Diastereoselective heterogeneous catalytic hydrogenation of Baylis- Hillman adducts
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We describe herein our results concerning a highly diastereoselective heterogeneous hydrogenation of Baylis-Hillman adducts obtained from aromatic aldehydes. The results obtained are complementary to those already described for homogeneous catalytic hydro
- Mateus, Cristiano R.,Almeida, Wanda P.,Coelho, Fernando
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p. 2533 - 2536
(2007/10/03)
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- Phosphine catalyzed aldol reaction between ketene silyl acetals and aldehydes: Nucleophilic O-Si and C-Si bond cleavage by phosphines
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A highly nucleophilic phosphine, tris(2,4,6-trimethoxyphenyl)phosphine (TTMPP), catalyzes the aldol reaction between ketene silyl acetals and aldehydes to give the corresponding aldol products in good to high yields. This reaction is considered to proceed through naked enolates produced by nucleophilic O-Si and C-Si bond cleavage.
- Matsukawa, Satoru,Okano, Naoko,Imamoto, Tsuneo
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p. 103 - 107
(2007/10/03)
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- Spontaneous aldol and Michael additions of simple enoxytrimethylsilanes in DMSO
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Activation of simple trimethylsilyl ketene acetals by dipolar aprotic solvents has been evidenced, allowing efficient solvent assisted aldol and Michael additions under extremely simple, mild and metal free conditions. (C) 2000 Elsevier Science Ltd.
- Génisson, Yves,Gorrichon, Liliane
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p. 4881 - 4884
(2007/10/03)
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