Influence de la geometrie de l'enolate sur la stereochimie de la condensation aldolique

Dubois, Jacques-Émile; Fellmann, Pierre

doi:10.1016/s0040-4039(00)72102-2

Cited by 68 publications

(17 citation statements)

References 10 publications

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“…For example, for trans-enolates, one might anticipate that transition state T2 might be destabilized relative to T1 by maximizing both R2 ÷-'-R1 and R2 ÷--L steric parameters. Both Dubois (8) and Heathcock (5) have demonstrated that, in part, enolate geometry correlates with product stereochemistry as predicted by this model. For lithium enolates, however, the correlation between enolate geometry and product stereochemistry is only high when the enolate ligand R1 approximates that of a tertiary butyl group.…”

Section: Enantioselective Aldol Condensationsmentioning

confidence: 71%

Chiral enolate design

Evans¹,

Takacs²,

McGee³

et al. 1981

Pure and Applied Chemistry

273

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The basic design features associated with the construction of chiral propionate enolates will be presented. It has been found that amide and imide enolates derived from -amino alcohols exhibit excellent levels of asymmetric induction in both alkylations and aldol condensations. For the aldol condensations metal structure was found to be of critical importance in the control of both threo-diastereoselection and chirality transfer. Both boron and zirconium enolates were found to be excellent substrates for the aldol process where >98% enantioselection was observed.

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Section: Enantioselective Aldol Condensationsmentioning

confidence: 71%

Chiral enolate design

Evans¹,

Takacs²,

McGee³

et al. 1981

Pure and Applied Chemistry

273

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“…The aldolic condensation [26][27][28][29] of furfural (F) on acetone (Ac) takes place in alkaline medium. It implies the generation of a carbanion obtained from abstraction of a proton in alpha of acetone carbonyl function and leads to the 4-(2-furyl)-3-buten-2-one (FAc).…”

Section: Aldolic Condensation Of Furfural On Acetonementioning

confidence: 99%

Stoichio-kinetic modeling and optimization of chemical synthesis: Application to the aldolic condensation of furfural on acetone

Fakhfakh¹,

Cognet²,

Cabassud³

et al. 2008

Chemical Engineering and Processing: Process Intensification

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The condensation reaction of furfural (F) on acetone (Ac) gives a high added value product, the 4-(2-furyl)-3-buten-2-one (FAc), used as aroma in alcohol free drinks, ice, candies, gelatines and other products of current life. This synthesis valorises the residues of sugar cane treatment since furfural is obtained by hydrolysis of sugar cane bagasse followed by vapor training extraction. In the face of numerous and complex reactions involved in this synthesis, it is very complicated to define the kinetic laws from exact stoichiometry. A solution allowing to cope the problem consists in identifying an appropriate stoichiometric model. It does not attempt to represent exactly all the reaction mechanisms, but proposes a mathematical support to integrate available knowledge on the transformation. The aim of this work is the determination of stoichiometric and kinetic models of the condensation reaction of furfural on acetone. Concentrations of reagents and products are determined by gas and liquid chromatography. Concentration profiles obtained at different temperatures are used to identify kinetic parameters. The model is then used for the optimization of the production of FAc. The interest of such tool is also shown for the scale up of laboratory reactor to a large scale. The anticipation of the reaction behaviour in large scale is crucial especially when the reactor presents important limitations of thermal exchange capacity.

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“…13 Although the cis enolate of 3-pentanone shows reasonably good erythro selectivity in its reaction with pivaldehyde (eq 7), the isomeric trans enolate is stereochemically indiscriminate (eq 8). 13 Although the cis enolate of 3-pentanone shows reasonably good erythro selectivity in its reaction with pivaldehyde (eq 7), the isomeric trans enolate is stereochemically indiscriminate (eq 8).…”

Section: Simple Diastereoselection; Erythro-threo Selectivitymentioning

confidence: 99%

“…It is a corollary of this hypothesis that trans enolates in which R' is large should give threo aldols, as is the case. 13 Seebach has pointed out that the idealized Zimmerman-Traxler transition state indicated in Scheme 1 neglects the fact that Li-0 bonds are rather long (approximately 1.95 A). It is likely that lithium enolates exist and react in ethereal solutions as aggregates.…”

Section: H Heathcockmentioning

confidence: 99%

The Aldol Condensation as a Tool for Stereoselective Organic Synthesis

Heathcock

1983

Current Trends in Organic Synthesis

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Influence de la geometrie de l'enolate sur la stereochimie de la condensation aldolique

Cited by 68 publications

References 10 publications

Chiral enolate design

Chiral enolate design

Stoichio-kinetic modeling and optimization of chemical synthesis: Application to the aldolic condensation of furfural on acetone

The Aldol Condensation as a Tool for Stereoselective Organic Synthesis

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