Organocatalyst For Direct Aldol Reaction Research Articles

Cooperative catalysis of cellulose nanofiber and organocatalyst in direct aldol reactions

Cellulose nanofibers (CNFs) are finding a wide range of applications in the forthcoming sustainable society because of their carbon-neutral renewability and superior physicochemical properties. Here, we first show a cooperative organocatalysis by combining TEMPO-oxidized cellulose nanofiber (TOCN) and proline to enhance the catalytic efficiency in a direct aldol reaction. The yields of proline-catalyzed aldol products drastically increased in the presence of catalytically-inactive TOCN. This effect was also achieved by simply adding the TOCN to the reaction conditions where various proline analogues including structurally simple pyrrolidine and piperidine were used instead of proline. TOCN was superior to physically-pulverized CNF in the organocatalytic efficiency, and the nanofibrillation of cellulose microfibrils in reaction media was essential to induce the drastic enhancement in catalytic activity. The present finding will bring a new entry in the applications of CNFs, and open up a new phase in developing highly efficient molecular transformations in green chemical industries.

ChemInform Abstract: Enantiopure Azetidine‐2‐carboxamides as Organocatalysts for Direct Asymmetric Aldol Reactions in Aqueous and Organic Media.

Abstract A family of enantiopure azetidine-2-caboxamides was asymmetrically synthesized, and was examined as organocatalyst in direct aldol reactions. A well chosen chiral azetidine-2-caboxamide was found to smoothly catalyze the direct aldol reaction of various benzaldehydes with acetone in brine, and β-hydroxy ketones were produced with enantiomeric excess up to 96%. The reaction of benzaldehydes with cyclic ketones also led to the formation of anti-products in diastereomeric ratio up to 99:1 and enantiomeric excess up to 99%.

Polydopamine--an organocatalyst rather than an innocent polymer.

Polydopamine (PDA) is easily available by oxidation of dopamine and is widely used for persistent coatings of various materials. It is hitherto considered to be inert in many interesting biomedical and other applications. Results presented here, reveal an unexpected behavior of polydopamine as an organocatalyst in direct aldol reactions under mild conditions. Evidence was found for dual catalysis making use of amino and phenolic hydroxy groups found in PDA. Thus scientists must be aware that PDA is not an innocent polymer and can cause unwanted side effects in important applications, such as in biomedicine or as supports in catalysis.

Enantiopure azetidine-2-carboxamides as organocatalysts for direct asymmetric aldol reactions in aqueous and organic media

A family of enantiopure azetidine-2-caboxamides was asymmetrically synthesized, and was examined as organocatalyst in direct aldol reactions. A well chosen chiral azetidine-2-caboxamide was found to smoothly catalyze the direct aldol reaction of various benzaldehydes with acetone in brine, and β-hydroxy ketones were produced with enantiomeric excess up to 96%. The reaction of benzaldehydes with cyclic ketones also led to the formation of anti-products in diastereomeric ratio up to 99:1 and enantiomeric excess up to 99%.

Design, Synthesis and Catalytic Property of L-Proline Derivatives as Organocatalysts for Direct Aldol Reaction

A series of chiral prolinamide compounds with pyridine-2, 6-dicarboxylic acid moieties derived from L-proline have been designed and synthesized, their catalytic properties for direct asymmetric aldol reactions were also studied in this article. These catalysts gave the aldol product in high yield (87%) and high enantioselectivity, up to 85%, of the anti-structure at room temperature but gave disappointing results at a lower temperature or when additive was added. Conditions, including solvents, temperature and additives were screened for the reactions. Moreover, the influence of presence of water on yield and stereoselectivity was also discussed.

Various Polar Tripeptides as Asymmetric Organocatalyst in Direct Aldol Reactions in Aqueous Media

A series of tripeptide organocatalysts containing a secondary amine group and two amino acids with polar side chain units were developed and evaluated in the direct asymmetric intermolecular aldol reaction of 4-nitrobenzaldehyde and cyclohexanone. The effectiveness of short polar peptides as asymmetric catalysts in aldol reactions to attain high yields of enantio- and diastereoselective isomers were investigated. In a comparison, glutamic acid and histidine produced higher % ee and yields when they were applied as the second amino acid in short trimeric peptides. These short polar peptides were found to be efficient organocatalysts for the asymmetric aldol addition reaction in aqueous media.

ChemInform Abstract: Guanidinium‐Tagged Organocatalysts for Direct Aldol Reactions.

AbstractHexasubstituted guanidinium moieties are used as ionic liquid tags for organocatalysts [cf.

Guanidinium-tagged Organocatalysts for Direct Aldol Reactions

Hexasubstituted guanidinium moieties have been used as ionic liquid tags for organocatalyts for the first time. Such conjugates were obtained in the (S)-proline and (S)-pyrrolidine-2-ylmethyl series by alkylation reactions of pentasubstituted guanidines. The resulting guanidinium-tagged organocatalysts were applied to asymmetric direct aldol reactions providing high stereoselectivities and yields and good recyclability, and thus performed better than (S)-proline itself

Guanidinium-tagged Organocatalysts for Direct Aldol Reactions

Guanidinium-tagged Organocatalysts for Direct Aldol Reactions

Virtual screening prediction of new potential organocatalysts for direct aldol reactions

A support vector machine (SVM)-based virtual screening method is demonstrated as a rapid computational tool for the prediction of potential asymmetric organocatalysts for the direct aldol reaction. Our models show good accuracy at cross-validation and independent testing. Structure analyses of screening hits from the PubChem database revealed several new classes of compounds, including β-amino acids, diamines and hydrazides, as potential chiral organocatalysts.

Rationally designed 4-phenoxy substituted prolinamide phenols organocatalyst for the direct aldol reaction in water

A rationally designed 4-phenoxy substituted prolinamide phenols as an efficient hydrophobic organocatalyst for direct asymmetric aldol reaction in water has been developed. High yield (up to 99%), diastereoselectivity (up to 99:1), and enantioselectivity (up to 97%) were obtained under optimal condition. The influence of substituent groups on the reactivity of catalysts was studied in detail.

Pyrrolidine as an efficient organocatalyst for direct aldol reaction of trifluoroacetaldehyde ethyl hemiacetal with ketones

Pyrrolidine-catalyzed aldol reaction of trifluoroacetaldehyde ethyl hemiacetal ( 1) with ketones or aldehydes was described. In the presence of 20 mol % of pyrrolidine, the reaction proceeded smoothly at room temperature to afford the aldol products in good to excellent yields (up to 95%). Pyrrolidine showed a much higher catalytic activity than piperidine in the reaction with less reactive ketones. GC analysis clearly indicated that the catalyst and the enamine intermediates were kept at extremely low concentration during the reaction. Based on these observations, we suggested that formation of the enamine would be a rate-determining step for the catalytic aldol reaction. In addition, the asymmetric aldol reaction of 1 with cyclohexanone catalyzed by l-proline derivatives was also discussed.

Functionalized ionic liquids catalyzed direct aldol reactions

A series of functionalized ionic liquids (FILs) incorporated with chiral-pyrrolidine unit have been synthesized and tested as reusable organocatalysts for direct aldol reactions. FIL 1b in combination with acetic acid and water as additives could effectively catalyze direct aldol reactions of various ketone donors in high yields and the FIL catalyst was easily recycled and reused for six times with slight reduction in activity. Based on experimental observations as well as previous reports, we proposed that the reactions occurred via syn-enamine intermediate and the ionic-liquid moiety in the FIL provides some space shielding for the participating aldehyde acceptors that accounts for the modest enantioselectivities observed in the reactions.

(2S,5S)‐Pyrrolidine‐2,5‐dicarboxylic Acid, an Efficient Chiral Organocatalyst for Direct 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, please click on HTML or PDF.

(2 S,5 S)-Pyrrolidine-2,5-dicarboxylic acid, an efficient chiral organocatalyst for direct aldol reactions

Enantioselective aldol reaction of ketones with aldehydes catalyzed by (2 S,5 S)-pyrrolidine-2,5-dicarboxylic acid in the presence of an equal molar amount of Et 3N was described. By using the new chiral organocatalyst, the direct aldol condensation products were obtained in reasonable yields and up to 90% ee.

A Highly Efficient Organocatalyst for Direct Aldol Reactions of Ketones with Aldehydes.

ChemInformVolume 36, Issue 45 Preparative Organic Chemistry A Highly Efficient Organocatalyst for Direct Aldol Reactions of Ketones with Aldehydes. Zhuo Tang, Zhuo Tang Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this authorZhi-Hua Yang, Zhi-Hua Yang Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this authorXiao-Hua Chen, Xiao-Hua Chen Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this authorLin-Feng Cun, Lin-Feng Cun Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this authorAi-Qiao Mi, Ai-Qiao Mi Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this authorYao-Zhong Jiang, Yao-Zhong Jiang Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this authorLiu-Zhu Gong, Liu-Zhu Gong Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this author Zhuo Tang, Zhuo Tang Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this authorZhi-Hua Yang, Zhi-Hua Yang Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this authorXiao-Hua Chen, Xiao-Hua Chen Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this authorLin-Feng Cun, Lin-Feng Cun Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this authorAi-Qiao Mi, Ai-Qiao Mi Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this authorYao-Zhong Jiang, Yao-Zhong Jiang Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this authorLiu-Zhu Gong, Liu-Zhu Gong Chengdu Inst. Org. Chem., Chin. Acad. Sci., Chengdu 610041, Peop. Rep. ChinaSearch for more papers by this author First published: 11 October 2005 https://doi.org/10.1002/chin.200545028Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume36, Issue45November 8, 2005 RelatedInformation

A Highly Efficient Organocatalyst for Direct Aldol Reactions of Ketones with Aldedydes

L-proline amides derived from various chiral beta-amino alcohols that bear substituents with various electron natures at their stereogenic centers are prepared and evaluated for catalyzing the direct Aldol reaction of 4-nitrobenzaldehyde with acetone. Catalysts with strong electron-withdrawing groups are found to exhibit higher catalytic activity and enantioselectivity than their analogues with electron-donating groups. The presence of 2 mol % catalyst 4g significantly catalyzes the direct Aldol reactions of a wide range of aldehydes with acetone and butanone, to give the beta-hydroxy ketones with very high enantioselectivities ranging from 96% to >99% ee. High diastereoselectivity of 95/5 was observed for the anti Aldol product from the reaction of cyclohexanone, and excellent enantioselectivity of 93% ee was provided for anti Aldol product from the reaction of cyclopentanone.