Direct Asymmetric Aldol Reaction Research Articles

Chitosan-supported cinchonine as an efficient organocatalyst for direct asymmetric aldol reaction in water

Chitosan-supported succinic anhydride-cinchonine (CTS-SA-CN) was synthesized via a two-step route with succinic anhydride as the linker. The catalyst was used to promote the direct asymmetric aldol reaction between cyclohexanone and a variety of aromatic aldehydes in aqueous medium. Aldol adducts were obtained in excellent yields (up to 99%) and good enantioselectivities (up to 96% ee). The CTS-SA-CN catalyst was successfully recycled simply by filtration after use, and was reused 5 times without any significant loss of activity.

ChemInform Abstract: A New Organocatalyst Derived from Abietic Acid and 4‐Hydroxy‐L‐proline for Direct Asymmetric Aldol Reactions in Aqueous Media.

AbstractThe new catalyst efficiently catalyzes the aldol reaction between aromatic aldehydes and ketones with only 1 mol% loading.

Redox Tuning of a Direct Asymmetric Aldol Reaction

Presented herein is a redox tuning strategy for asymmetric aminocatalysis with a designed chiral ferrocenophane. Under redox control, the ferrocenophane catalyst efficiently catalyzes the asymmetric aldol reaction at room temperature with excellent yield and good stereoselectivity. Moreover, the redox-active ferrocene moiety also served as phase-tag to facilitate catalyst recovery and reuse. The catalyst can be reused for five cycles without much loss of activity. Ferrocenium of the oxidized ferrocenophane was proposed to serve as Lewis acidic site, thus accounting for the stereo control.

Redox Tuning of a Direct Asymmetric Aldol Reaction

AbstractPresented herein is a redox tuning strategy for asymmetric aminocatalysis with a designed chiral ferrocenophane. Under redox control, the ferrocenophane catalyst efficiently catalyzes the asymmetric aldol reaction at room temperature with excellent yield and good stereoselectivity. Moreover, the redox‐active ferrocene moiety also served as phase‐tag to facilitate catalyst recovery and reuse. The catalyst can be reused for five cycles without much loss of activity. Ferrocenium of the oxidized ferrocenophane was proposed to serve as Lewis acidic site, thus accounting for the stereo control.

ChemInform Abstract: Chiral Room Temperature Ionic Liquids as Enantioselective Promoters for the Asymmetric Aldol Reaction.

AbstractChiral ionic liquids (CIL), derived from natural amino acids, are used as reaction media for direct asymmetric aldol reactions catalyzed by L‐proline.

Pepsin-catalyzed direct asymmetric aldol reactions for the synthesis of vicinal diol compounds

The catalytic promiscuity of pepsin from porcine gastric mucous was observed in catalysis of the direct asymmetric aldol reactions of aromatic aldehydes with acetones, which were substituted by hydroxy-, dihydroxy-, methoxy- and benzyloxy- for the synthesis of diol compounds in acetonitrile. This biocatalysis was also applicable to the aldol reactions of cyclic or hetereocyclic ketones with aromatic aldehydes. Yields of up to 87%, diastereoselectivities of up to >99/1 dr and enantioselectivities of up to 75% ee were achieved.

ChemInform Abstract: Construction of anti‐1,2‐Diols Bearing Chiral Tertiary Alcohol Moiety Using Free Hydroxyacetone as Aldol Donor by Imidazole‐Based Prolineamide Catalyst.

AbstractFor the first time a direct asymmetric aldol reaction of free hydroxyacetone and activated ketones is achieved by using the new title catalyst.

Highly Enantioselective Direct Asymmetric Aldol Reaction Catalyzed by 4,5‐Methano‐L‐proline

AbstractThe 4,5‐methano‐L‐proline was used as chiral organocatalysts in direct asymmetric aldol reactions. Under the optimal conditions, excellent enantioselectivities (up to 99% ee) were obtained with high chemical yields (up to 95%) for a series of aldehydes using only 5 mol% catalyst loading. To show the practicality of the method, the reaction was tested at a large scale. The reaction was complete in 16 h, and the aldol product was obtained in 86% yield and 93% ee.

Temperature-responsive hairy particle-supported proline for direct asymmetric aldol reaction in water

In this paper, three kinds of hairy particles with different brush structures were prepared and evaluated as chiral catalysts in the direct asymmetric aldol reaction.

Asymmetric organocatalysts supported on vinyl addition polynorbornenes for work in aqueous media

Proline-functionalized VA-PNBs behave as active, recoverable and reusable organocatalysts for the asymmetric direct aldol reaction in aqueous media.

Catalytic Asymmetric Direct Aldol Reaction of α-Alkyl Azlactones and Aliphatic Aldehydes.

An unprecedented highly diastereoselective and enantioselective aldol reaction of α-alkyl azlactones and aliphatic aldehydes was achieved with cinchona alkaloid catalysts. To our knowledge, this reaction provides the first useful catalytic asymmetric access toward β-hydroxy-α-amino acids bearing alkyl substituents, which are structural motifs embedded in many natural products.

Aerobic photooxidative direct asymmetric aldol reactions of benzyl alcohols using water as the solvent

We report an aerobic photooxidative direct asymmetric aldol reaction using water as the solvent.

Highly modular dipeptide-like organocatalysts for direct asymmetric aldol reactions in brine

The dipeptide-like organocatalysts have been developed for asymmetric aldol reactions in brine to achieve high yields and enantioselectivities with 1 mol% catalyst-loading.

Direct Asymmetric Aldol Reactions Promoted by (1R, 3S, 4S)‐2‐Aza‐bicyclo[2.2.1]heptane‐3‐carboxylic Acid as an Organocatalyst

Direct Asymmetric Aldol Reactions Promoted by (1<i>R</i>, 3<i>S</i>, 4<i>S</i>)‐2‐Aza‐bicyclo[2.2.1]heptane‐3‐carboxylic Acid as an Organocatalyst

Efficient synthesis of zirconium poly(styrene-phenylvinylphosphonate)phosphate-supported proline as a recyclable catalyst for direct asymmetric aldol reactions in water

A completely non-chromatographic and highly large-scale adaptable synthesis of zirconium poly(styrene-phenylvinylphosphonate)phosphate-supported l-proline (ZrPS-PVPA-Pr) has been developed in only three steps overall.

Alternating chiral selectivity of aldol reactions under the confined space of mesoporous silica.

The chiral selectivities were altered and high diastereo- and enantio-selectivities of the products were obtained in water medium without adding acid co-catalysts when a primary-tertiary diamine catalyst was immobilized on mesoporous SBA-15 to form a recyclable catalyst for the direct asymmetric aldol reaction of cyclohexanone with p-nitrobenzaldehyde.

ChemInform Abstract: Enantioselective Aldol Reactions of α,β‐Unsaturated Ketones with Trifluoroacetophenone Catalyzed by a Chiral Primary Amine.

Abstract Chiral primary amine catalyzed direct asymmetric aldol reactions of ketones with trifluoroacetophenone, afforded trifluoromethylated β-hydroxycarbonyl aldol products bearing a quaternary carbon stereogenic center in high yields (up to 93% yield) and with high to excellent enantioselectivities of up to 99% ee.

Pyrrolidine–diaminomethylenemalononitrile organocatalyst for solvent-free asymmetric direct aldol reactions

Pyrrolidine–diaminomethylenemalononitrile (pyrrolidine–DMM) organocatalyst has been an efficient reaction medium to promote asymmetric direct aldol reactions to afford the corresponding addition products in high yields with up to 99% ee under solvent-free conditions.

Direct asymmetric aldol reactions in aqueous media catalyzed by a β-cyclodextrin–proline conjugate with a urea linker

Covalently attaching proline to β-CD through a urea linkage resulted in the synthesis of a water-soluble chiral organocatalyst 1 in high yield. Catalytic asymmetric aldol condensations between aldehydes and acetone were carried out under water-containing conditions by using 5mol% of 1 as catalyst, and moderate to high yields and enantioselectivities (up to 99% ee) were achieved for a broad range of aldehydes. Substrate selectivity was also tested. Recycling experiments were performed to confirm good recyclability and reusability of the catalyst.

Chiral metal-organic frameworks bearing free carboxylic acids for organocatalyst encapsulation.

Two chiral carboxylic acid functionalized micro- and mesoporous metal-organic frameworks (MOFs) are constructed by the stepwise assembly of triple-stranded heptametallic helicates with six carboxylic acid groups. The mesoporous MOF with permanent porosity functions as a host for encapsulation of an enantiopure organic amine catalyst by combining carboxylic acids and chiral amines in situ through acid-base interactions. The organocatalyst-loaded framework is shown to be an efficient and recyclable heterogeneous catalyst for the asymmetric direct aldol reactions with significantly enhanced stereoselectivity in relative to the homogeneous organocatalyst.