Organocatalyst For Asymmetric Aldol Reaction Research Articles

2-Hydroxy-3-[( S)-prolinamido]pinanes as novel bifunctional organocatalysts for asymmetric aldol reactions in aqueous media

Novel ( S)-prolinamides with stereoisomeric 2-hydroxy-3-aminopinane units have been synthesized. In the presence of (1 R,2 R,3 S,5 R)-2-hydroxy-3-[( S)-prolinamido]pinane (5 mol %) cyclic ketones reacted with (hetero-)aromatic aldehydes in aqueous media to afford chiral aldols in high yields. The reaction had moderate to high diastereo- (dr up to 91/9) and enantioselectivities (up to 83% ee).

Proline-based dipeptides as efficient organocatalysts for asymmetric aldol reactions in brine

Simple N-proline-based dipeptides with two N–H groups in combination with 2,4-dinitrophenol (DNP) catalyze the direct asymmetric aldol reactions of aldehydes with a broad range of ketones to furnish the corresponding aldol products in high yields (up to 99%) and with high enantioselectivities (up to 97%) and diastereoselectivities (up to >99:1, anti/ syn) at room temperature and in brine.

N-Prolinylanthranilic acid derivatives as bifunctional organocatalysts for asymmetric aldol reactions

Several N-prolinylanthranilic acid derivatives were prepared and tested as bifunctional organocatalysts in the direct asymmetric aldol reaction of cyclohexanone with p-nitrobenzaldehyde. It was found that methyl substitution ortho to the carboxylic acid improves enantioselectivity, but substitution ortho to the anilide group does not. The catalyst derived from 2-amino-6-methylbenzoic acid was tested over a range of direct asymmetric aldol reactions and its overall performance is equal to or better than many of the known prolinamide catalysts in terms of yield, diastereoselectivity, and enantioselectivity.

Glucosamine-Based Primary Amines as Organocatalysts for the Asymmetric Aldol Reaction

Glucosamine derivatives have been synthesized starting from commercially available N-acetyl-D-glucosamine/glucosamine hydrochloride and have been employed successfully as efficient organocatalysts for the direct asymmetric aldol reaction between cyclohexanone and aryl aldehydes having diversified substituents. Furthermore, the anomeric effect of various groups present at the anomeric position on the catalytic activity of these organocatalysts was also studied.

Carbohydrate-derived alcohols as organocatalysts in enantioselective aldol reactions of isatins with ketones

The catalytic activity of carbohydrate-derived amino alcohols in the enantioselective aldol reaction of ketones with isatin and its derivatives has been examined for the first time. The carbohydrate-derived amino alcohols 5 were found to be efficient organocatalysts for asymmetric aldol reactions. A variety of isatins were used as substrates and the corresponding aldol products were obtained in high yields (up to 99%) and with moderate enantioselectivities (up to 75%).

ChemInform Abstract: Enantioselective Aldol Reaction Using Recyclable Montmorillonite‐Entrapped N‐(2‐Thiophenesulfonyl)prolinamide.

AbstractThienylsulfonylprolinamide (TSPA) immobilized on montmorillonite represents an efficient and recyclable organocatalyst for asymmetric aldol reactions.

A new ( S)-prolinamide modified by an ionic liquid moiety—a high performance recoverable catalyst for asymmetric aldol reactions in aqueous media

New prolinamide derivatives modified with ionic liquid moieties were synthesized and studied as organocatalysts in asymmetric aldol reactions in water. Aldol reactions between cycloalkanones or methylketones and aromatic aldehydes proceeded under studied conditions with high conversions (yields), diastereo- and enantioselectivities in the presence of a hydrophobic catalyst bearing a PF 6 anion (1–5 mol %). The procedure is scalable and the catalyst retained its diastereo- and enantioselectivity over at least four reaction cycles and its activity over at least three reaction cycles.

ChemInform Abstract: 2,4‐Dinitrophenol as an Effective Cocatalyst: Greatly Improving the Activities and Enantioselectivities of Primary Amine Organocatalysts for Asymmetric Aldol Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Hydroxy‐α‐Amino Acids Modified by Ionic Liquid Moieties: Recoverable Organocatalysts for Asymmetric Aldol Reactions in the Presence of Water.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

2,4-Dinitrophenol as an Effective Cocatalyst: Greatly Improving the Activities and Enantioselectivities of Primary Amine Organocatalysts for Asymmetric Aldol Reactions

Seven primary amine organocatalysts 1a-g were readily prepared from natural primary amino acids via two steps and then were used to catalyze the direct asymmetric aldol reaction, but they showed very poor enantioselectivities and activities. As an effective cocatalyst, 2,4-dinitrophenol (DNP) dramatically elevated the activities and enantioselectivities of these very inefficient primary amine organocatalysts. This remedial course to the very inefficient organocatalysts by selection and employment of the optimal cocatalyst was particularly cost-effective and environment-beneficial compared with de novo development of catalysts. The highest efficient organocatalytic system that was composed of 1f and DNP showed high enantioselectivities and good to high diastereoselectivities with a broad spectrum of seven ketones. The linear ketones and cyclopentanone got predominant syn products whereas cyclohexanone mainly gave anti products.

Hydroxy-α-amino acids modified by ionic liquid moieties: recoverable organocatalysts for asymmetric aldol reactions in the presence of water

New chiral ionic liquids bearing proline, serine or threonine moieties were synthesized. Compounds that contain 1-dodecylimidazolium or 4-(5- n-nonyl)-pyridinium cations and NTf 2 or PF 6 anions efficiently catalyze the asymmetric aldol reaction between aldehydes and ketones in the presence of water to generate aldols with high distereo- (up to 98:2) and enantioselectivity (up to >99% ee). 4-Hydroxyproline modified by the 4-(5- n-nonyl)-pyridinium hexafluorophosphate moiety retains its activity and selectivity over at least eight reaction cycles.

ChemInform Abstract: Merrifield Resin Supported Dipeptides: Efficient and Recyclable Organocatalysts for Asymmetric Aldol Reactions under Neat Reaction Conditions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Camphor‐Containing Organocatalysts in Asymmetric Aldol Reaction on Water.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Bimorpholines as Alternative Organocatalysts in Asymmetric Aldol Reactions

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Camphor containing organocatalysts in asymmetric aldol reaction on water

A new class of bifunctional organocatalysts were synthesized and proved to be effective in catalyzing aldol reaction on water with high to excellent diastereo- and enantioselectivities.

Structural constraints for C2-symmetric heterocyclic organocatalysts in asymmetric aldol reactions

Asymmetric aldol reactions were studied in the presence of heterocyclic bimorpholine- and bipiperidine-type organocatalysts. Bimorpholine derivatives were found to be more reactive and more selective in intramolecular, as well as intermolecular, reactions.

Prolinamides derived from aminophenols as organocatalysts for asymmetric direct aldol reactions

N-(2-Hydroxyphenyl)-prolinamides were synthesized with the aim to introduce an additional hydrogen bonding site to the prolinamide structure. These compounds were evaluated as organocatalysts for asymmetric aldol reactions between aromatic aldehydes and cyclohexanone. Very good yields, diastereoselectivities, and enantioselectivities were achieved in both organic solvents and water. The importance of the additional hydrogen bonding site was confirmed by comparative experiments with prolinamide derivatives without the hydroxyl group.

Bimorpholines as Alternative Organocatalysts in Asymmetric Aldol Reactions

Asymmetric organocatalytic aldol condensation is discussed on the basis of intramolecular and inter-molecular reactions. In addition to the widely used proline and its derivatives an application of the new type of the organocatalyst – bimorpholines in the above-mentioned reactions is described. The new catalyst has a unique C2-symmetric skeleton with four acceptor sites that makes it stereoselective and efficient. Small changes in the structure of the catalyst lead to a remarkable loss of selectivity.

4‐Substituted Prolines as Organocatalysts for Aldol Reactions.

AbstractFor Abstract see ChemInform Abstract in Full Text.

4-Substituted prolines as organocatalysts for aldol reactions

A series of 4-substituted prolines were prepared and evaluated as organocatalysts for asymmetric aldol reactions. Using (2 S,4 R)-4-camphorsulfonyloxy-proline, the aldol products were obtained in much higher enantiomeric excess in comparison to that observed using proline itself. In addition, the improved solubility of these new catalysts in organic solvents permits their use in lower sub-stoichiometric amounts compared to proline.