Asymmetric Aldol Reaction Of Acetone Research Articles

Highly Efficient Direct Asymmetric Aldol Reactions Catalyzed by a Prolinethioamide Derivative in Aqueous Media

AbstractL‐Prolinethioamide derivative 1c, prepared from the readily available natural amino acids L‐proline and L‐valine, was studied for the direct asymmetric aldol reaction of acetone with various aromatic aldehydes at 0 °C or room temperature. A loading of only 0.1–0.2 mol‐% of derivative 1c was employed in this catalytic system, and excellent enantioselectivities and yields (up to 98 % yield, >99 % ee) could be achieved in aqueous media.

ChemInform Abstract: Direct Asymmetric Aldol Reaction of Acetone with α‐Ketoesters Catalyzed by Primary—Tertiary Diamine Organocatalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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.

Direct asymmetric aldol reaction of acetone with α-ketoesters catalyzed by primary–tertiary diamine organocatalysts

Novel primary–tertiary diamine organocatalysts derived from l-serine were utilized to promote enantioselective aldol reaction of acetone with α-ketoesters. The desired products were obtained in high yields and with good to excellent enantioselectivities (up to 95% ee).

Chiral Diamine/Brønsted Acid Conjugates Confined in Mesoporous Silica as Catalyst for the Asymmetric Aldol Reaction

Abstract Chiral primary-tertiary diamine/Bronsted acid conjugates were selectively immobilized on the inner surface of mesoporous silica and used as catalyst for the asymmetric aldol reaction of acetone with various aldehydes. The catalyst showed modest reactivity and enantioselectivity and can be reused 6 times without loss of activity and enantioselectivity. As compared with silica gel as the support, an increase in ee value of the reaction product was observed with the SBA-15-immobilized organic catalyst. This was believed to be due to the confinement effect of the nanopores.

Direct asymmetric aldol reaction using MBHA resin-supported peptide containing l-proline unit

MBHA resin-supported tripeptide catalyst system containing l-proline unit has been developed for use in the direct asymmetric aldol reaction of acetone and aldehydes, which afford the corresponding products with satisfactory isolated yields and enantiomeric excesses.

Ionic liquid-supported proline as catalyst in direct asymmetric aldol reaction

Ionic-liquid-supported proline derivative was synthesized starting from L-proline and was used to catalyze direct asymmetric aldol reaction of acetone with aldehydes. The yield and optical purity of the condensation products, the corresponding β-hydroxy carbonyl compounds were comparable with those obtained under homogeneous conditions. Moreover, the catalyst can be reused for at least four times.

L‐Proline‐Catalyzed Asymmetric Direct Aldol Reaction of Heteroaromatic Aldehydes and Acetone: Improvement of Catalytic Efficiency in Ionic Liquid bmim [BF4

l‐proline in bmim [BF4] ionic liquid has been successfully used as an efficient and reusable catalyst for the direct asymmetric aldol reaction of acetone with different heteroaromatic aldehydes to afford higher selectivity of the aldol products with good enantioselectivity.

Asymmetric organocatalysis with glycosyl-β-amino acids: direct asymmetric aldol reaction of acetone with aldehydes

Direct asymmetric aldol reaction of acetone with aromatic aldehydes was achieved in good yields and high enantioselectivity using 5-amino-5-deoxy-β- l- ido-(α- d- gluco)-heptofuranuronic acids as a new class of organocatalysts.

An unexpected inversion of enantioselectivity in direct asymmetric aldol reactions on a unique L-proline/ γ-Al 2O 3 catalyst

L-proline adsorbed on γ-Al 2O 3 unexpectedly switches the enantioselectivity of the direct asymmetric aldol reaction of acetone with p-nitrobenzaldehyde from 68% ee ( R configuration for free L-proline catalyst) with 80% yield to 21% ee ( S configuration) with 78% yield. The inversion of enantioselectivity was also observed in the direct asymmetric aldol reactions of acetone with several other aromatic aldehydes catalyzed by the L-proline adsorbed on γ-Al 2O 3. This inversion phenomenon is found to be general for different types of amino acids adsorbed on γ-Al 2O 3. The hydroxyl groups on γ-Al 2O 3 are found to be involved in the inversion induction of enantioselectivity in these direct asymmetric aldol reactions.

New N-terminal prolyl-dipeptide derivatives as organocatalysts for direct asymmetric aldol reaction

A series of new N-terminal prolyl-dipeptide derivatives have been synthesized and evaluated as organocatalysts for the direct asymmetric aldol reaction of acetone with electron-deficient aromatic aldehydes. At room temperature, the presence of 10 mol % of catalysts 2 and 5 efficiently catalyzes the direct asymmetric aldol reaction to give the aldol adducts with modest to excellent enantiomeric excesses (ee) values, which are up to 96%.

Synthesis of a biphenyl-based axially chiral amino acid as a highly efficient catalyst for the direct asymmetric aldol reaction

A biphenyl-based axially chiral amino acid ( S)- 2 has been designed and synthesized. The new amino acid ( S)- 2 has been found to be a more efficient catalyst than ( S)- 1 in the direct asymmetric aldol reaction of acetone with aldehydes. For instance, the use of only 0.1 mol % of ( S)- 2 was sufficient to complete the reaction between acetone and 4-nitrobenzaldehyde, giving the corresponding aldol adduct in good yield with an excellent enantioselectivity.

Catalytic asymmetric methallylation of ketones with an (H8-BINOLate)Ti-based catalyst.

The first catalytic asymmetric methallylation of ketones is reported. The catalyst, which is generated from titanium tetraisopropoxide, H8-BINOL, 2-propanol, and tetramethallylstannane, reacts with ketones in acetonitrile to afford tertiary homoallylic alcohols in fair to excellent yields (55-99%) and fair to high enantioselectivities (46-90%). Ozonolysis of the resulting products provides access to chiral beta-hydroxy ketones, which are not readily prepared from direct asymmetric aldol reaction of acetone with ketones.

Design of a Binaphthyl‐Based Axially Chiral Amino Acid as an Organocatalyst for Direct Asymmetric Aldol Reactions

A novel and robust binaphthyl-based amino acid was designed and successfully applied to the direct asymmetric aldol reaction. In some cases, this catalyst leads to higher yields and selectivities than the well-known proline catalyst. For instance, the direct asymmetric aldol reaction of acetone with 4-nitrobenzaldehyde in the presence of the binaphthyl-based amino acid catalyst proceeded smoothly to give the aldol adduct in 82% yield with 95% ee. This catalyst was also found to catalyze effectively the reactions of cyclic or unsymmetrical ketones to give the corresponding aldol adducts with excellent diastereo- and enantioselectivities.

L-Proline catalysed asymmetric aldol reactions in PEG-400 as recyclable medium and transfer aldol reactions

l-Proline-catalysed direct asymmetric aldol reaction of acetone with various aldehydes in PEG-400 is described. Recycling of the catalyst and solvent (PEG) was possible up to ten runs without loss of catalyst activity. l-Proline was also found to be an efficient catalyst for the asymmetric transfer aldol reaction between various aldehydes and diacetone alcohol for the first time. Good yields and enantioselectivities were observed with both methods.

Direct asymmetric aldol reaction in aqueous media using polymer-supported peptide

PEG-PS resin-supported tripeptide/zinc chloride catalyst system has been developed for use in the direct asymmetric aldol reaction of acetone with aldehydes in aqueous media. The peptide catalyst could be separated from the reaction mixture by filtration, and was reusable at least five times without significant change in its activity and selectivity.