- A Novel Imidazolidin-2-one Auxiliary for a Highly Stereoselective Aldol Route to β-Hydroxyesters
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Enantiomerically pure syn-aldols are obtained from the boron enolate of (4R,5S)-1,5-dimethyl-4-cyclohexyl-3-propanoylimidazolidin-2-one.Cleavage of the auxiliary affords the homochiral title esters in good yield.
- Drewes, Siegfried E,Malissar, Dean G S,Roos, Gregory H P
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Read Online
- 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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- Copper-ClickFerrophos-complex-catalyzed enantioselective reductive aldol reaction
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We have prepared several ClickFerrophos families and tested for the Cu(I)-catalyzed asymmetric reductive aldol reaction of ketones and aldehydes with an acrylic ester in the presence of phenylsilane. The Cu(I)-ClickFerrophos complex is efficient for the r
- Kato, Minoru,Oki, Hiroshi,Ogata, Kenichi,Fukuzawa, Shin-Ichi
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experimental part
p. 1299 - 1302
(2009/12/03)
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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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- Catalytic generation of activated carboxylates: Direct, stereoselective synthesis β-hydroxyesters from epoxyaldehydes
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The catalytic generation of activated carboxylates from epoxyaldehydes enables the direct, stereoselective synthesis of β-hydroxyesters under mild, convenient reaction conditions. In addition to providing a new method for the synthesis of anti-aldol adducts, this chemistry unveils a mechanistically viable solution to the catalytic, waste-free synthesis of esters. Copyright
- Chow, Kenneth Yu-Kin,Bode, Jeffrey W.
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p. 8126 - 8127
(2007/10/03)
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- Stereoselective synthesis of syn-α-methyl-β-hydroxy esters
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Boron enolates of an ethyl ketone structurally related to erythrulose react with achiral aldehydes in a highly stereoselective fashion to yield 1,2-syn/1,3-syn stereoisomers. Oxidative cleavage of the aldol adducts yields enantiopure O-formylated syn-α-me
- Carda, Miguel,Murga, Juan,Falomir, Eva,Gonzalez, Florenci,Marco, J. Alberto
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p. 3211 - 3220
(2007/10/03)
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- Chemistry of enoxysilacyclobutanes: Highly selective uncatalyzed aldol additions
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O-(Silacyclobutyl) ketene acetals derived from esters, thiol esters, and amides underwent facile aldol addition with a variety of aldehydes at room temperature without the need for catalysts. The uncatalyzed aldol addition reaction of O-(silacyclobutyl) ketene acetals displayed the following characteristics: (1) the rate of reaction was highly dependent on the spectator substituent on silicon and the geometry of the ketene acetal, (2) the O,O-ketene acetal of E configuration afforded the syn aldol products with high diastereoselectivity (93/7 to 99/1), (3) conjugated aldehydes reacted more rapidly than aliphatic aldehydes, and (4) the reaction was mildly sensitive to solvent. In addition, the aldol reaction was found to be efficiently catalyzed by metal alkoxides. Labeling experiments revealed that the thermal aldol reaction proceeds by direct intramolecular silicon group transfer, while the alkoxide-catalyzed version probably proceeds via in situ generated metal enolates. Computational modeling of the transition states suggests that the boat transition structures are preferred, supporting the observed syn selectivity of the thermal aldol reaction. Both thermal and alkoxide-catalyzed Michael additions were investigated, revealing a competition between 1,2- and 1,4-addition favoring the former.
- Denmark, Scott E.,Griedel, Brian D.,Coe, Diane M.,Schnute, Mark E.
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p. 7026 - 7043
(2007/10/02)
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- Ephedrine-Derived Imidazolidin-2-ones. Broad Utility Chiral Auxiliaries in Asymmetric Synthesis
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The scope of the readily available (4R,5S)-1,5-dimethyl-4-phenylimidazolidin-2-one (4) and its 4-cyclohexyl analogue 6 as practical, efficient chiral auxiliaries has been demonstrated.The enolate chemistry of their N-acyl derivatives exhibits features which recommend their use in asymmetric synthesis.The stereoselective boron-mediated aldol as well as alkylation and acylation results are presented.The steric control benefit derived by conversion of phenyl to cyclohexyl is highlighted. - Key Words: Imidazolidin-2-one, (4R,5S)-1,5-dimethyl-5-phenyl- or cyclohexyl- / (-)-Ephedrine / Stereoselective aldol / alkylation, acylation
- Drewes, Siegfried E.,Malissar, Dean G. S.,Roos, Gregory H. P.
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p. 2663 - 2674
(2007/10/02)
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- Chemistry of Ketene Acetals. Part 8. Stereochemistry of the Reaction of 1,1-Dimethoxypropene with Aldehydes
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The Lewis acid-catalysed (2+2)cycloadditions of 1,1-dimethoxypropene with various aldehydes RCHO have been studied.These reactions, which are supposed to proceed via dipolar intermediates, yield 2,2-dimethoxyoxetanes, the formation of which is reversible
- Hofstraat, Rob G.,Scheeren, Hans W.,Nivard, Rutger J. F.
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p. 561 - 564
(2007/10/02)
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