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Aldol Reaction (aldol + reaction)
Kinds of Aldol Reaction Terms modified by Aldol Reaction Selected AbstractsEnhanced Activity and Stereoselectivity of Polystyrene-Supported Proline-Based Organic Catalysts for Direct Asymmetric Aldol Reaction in WaterEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 31 2009Michelangelo Gruttadauria Abstract Several polystyrene-supported proline dipeptides and a prolinamide derivative were prepared by thiol,ene coupling. These materials were used as catalysts for the direct asymmetric aldol reaction in water, and results compared with unsupported catalysts in water. Such an approach gave more active or stereoselective catalysts compared to the unsupported compounds, showing that our immobilization procedure may be useful to develop catalytic materials with enhanced performance. Moreover, these catalysts can be recovered and reused for at least nine times without loss of activity or can be easily regenerated when their activity has decreased. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Bismuth Triflate Catalyzed Mukaiyama Aldol Reaction in an Ionic LiquidEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2005Thierry Ollevier Abstract We have developed an efficient, bismuth triflate catalyzed Mukaiyama aldol reaction. The reaction proceeds rapidly and affords the corresponding ,-hydroxy carbonyl compound in moderate to very good yields (up to 92,%). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Mild Synthesis of ,-Amino-,,,-difluoro Ketones from Acylsilanes and Trifluoromethyltrimethylsilane in a One-Pot Imino Aldol Reaction,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2005Sylvain Jonet Abstract ,-Amino-,,,-difluoro ketones have been very conveniently prepared in a one-pot procedure from acylsilanes, trifluoromethyltrimethylsilane and imines. The key intermediate in this reaction is a difluoroenoxysilane. The Lewis acid promoted imino aldol reaction was performed with BF3·OEt2 or under very mild conditions using a catalytic amount of Yb(OTf)3. The reaction with chiral benzylimines occurred in good yield with 52,78,% de. Palladium-catalyzed hydrogenolysis furnished an unprotected ,-amino-,,,-difluoro ketone or a ,-amino-,,,-difluoro alcohol. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Enantioselective Aldol Reaction using Recyclable Montmorillonite-Entrapped N -(2-Thiophenesulfonyl)prolinamideADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Noriyuki Hara Abstract N -(2-Thiophenesulfonyl)prolinamide could be easily introduced into Montmorillonite by a simple ion-exchange reaction. The asymmetric aldol reactions between various isatins with acetone or acetaldehyde using a heterogeneous Montmorillonite-entrapped organocatalyst afforded products with high enantioselectivity. The catalyst was readily reusable without significant loss of catalytic activity or enantioselectivity. [source] Organocatalyzed Highly Enantioselective and anti -Selective Construction of ,-Butenolides through Vinylogous Mukaiyama Aldol ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 8 2010Ning Zhu Abstract The formation of chiral ,-butenolides has been achieved with good yields (up to 90%), high enantioselectivity (up to 91%) and diastereoselectivity (up to 9/1, anti -selective) through an organocatalyzed vinylogous Mukaiyama aldol reaction of 2-(trimethylsilyloxy)furan and aldehydes. A wide range of chiral ,-butenolides was obtained under mild conditions by this methodology. [source] A Novel Proline-Valinol Thioamide Small Organic Molecule for a Highly Enantioselective Direct Aldol ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Bing Wang Abstract A new prolinethioamide compound 4, prepared from readily available natural amino acid L -proline and amino alcohol L -valinol, has been found to be an active catalyst for the direct aldol reaction of various aldehydes with acetone, cyclohexanone or cyclopentanone at 0,°C. Using only 2,mol% loading of this organocatalyst, the reaction could give high enantioselectivity with up to 96% enantiomeric excess for the reaction of 2-nitrobenzaldehyde with acetone. And as for the cyclohexanone, the excellent diastereoselectivity (anti/syn: 99/1) and enantioselectivity (99% ee) could be achieved when reacted with 3-nitrobenzaldehyde in water in the presence of this thioamide 4. This structurally simple catalyst is a highly efficient prolinethioamide derivative, and the terminal hydroxy group in this catalyst is a primary alcohol which is different from the previously reported prerequisite secondary or tertiary alcohol of prolinamides. Our results suggest a new strategy in the design of diversiform organic catalysts for direct asymmetric aldol reactions and related transformations. [source] Asymmetric Aldol Reaction of Ketones with Alkenyl Trichloroacetates Catalyzed by Dibutyltin Dimethoxide and BINAP,Silver(I) Complex: Construction of a Chiral Tertiary Carbon CenterADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Akira Yanagisawa Abstract A novel aldol reaction of alkenyl trichloroacetates with ,-keto esters was realized by using dibutyltin dimethoxide as a catalyst, which was regenerated by the addition of methanol. The reaction was found to be remarkably accelerated by the addition of a catalytic amount of a bidentate phosphine,silver(I) complex. Use of the BINAP,silver triflate (AgOTf) complex as the chiral co-catalyst resulted in the formation of optically active aldol products possessing a chiral tertiary carbon with up to 93% ee. This catalytic method was further applied to the asymmetric reaction of diketene with methyl benzoylformate. [source] Elucidation of Architectural Requirements from a Spacer in Supported Proline-Based Catalysts of Enantioselective Aldol ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Kerem Goren Abstract In order to delineate the properties of the spacer architecture responsible for the strong positive dendritic effect exhibited by polymer-supported proline-based catalysts, we prepared two series of polystyrene-bound model catalysts. The first series was based on a linear and partially dendritic spacers (of reduced branching and valency) imitating the length of the second generation spacer, while the second series was based on the first generation dendron spacer with one functional (proline-terminated) and one non-functional arm. Comparative studies of the model and original (fully dendritic) catalysts in the asymmetric aldol reaction of aromatic aldehydes with acetone disclose the features characteristic to the dendritic architecture, such as proximity between the terminal catalytic units and enhanced branching, as crucial for inducing higher yield and enantioselectivity in catalysis. [source] Dendritic Amplification of Stereoselectivity of a Prolinamide-Catalyzed Direct Aldol ReactionISRAEL JOURNAL OF CHEMISTRY, Issue 1 2009Kazuhiko Mitsui Isomeric "compact" and "expanded" dendrimers functionalized with L -prolinamide catalytic units at the periphery were compared as catalysts to monomer controls in the organocatalytic direct aldol condensation. A positive dendritic effect that amplifies the stereoselectivity of the direct aldol condensation was observed for dendrimers 3 and 4, compared with lower molecular weight catalysts L -prolinani-lide 1 and G1 dendron 2. The difference in the compactness between 3 and 4 appears to have less impact on the stereoselectivity than the preorganized multivalency of the dendritic catalysts. [source] The Ion Tag Strategy as a Route to Highly Efficient Organocatalysts for the Direct Asymmetric Aldol ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Marco Lombardo Abstract The installation of an imidazolium tag via acetate connection to the C-4 of cis -4-hydroxy- L -proline provides a highly efficient catalyst for the direct asymmetric aldol reaction, that works in a remarkably low catalyst loading (0.1,mol%) affording TONs up to 930 in the case of electron-poor aromatic aldehydes with ee up to >99%. [source] New Simple Hydrophobic Proline Derivatives as Highly Active and Stereoselective Catalysts for the Direct Asymmetric Aldol Reaction in Aqueous MediumADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2008Francesco Giacalone Abstract New 4-substituted acyloxyproline derivatives with different hydrophobic properties of the acyl group were easily synthesized and used as catalysts in the direct asymmetric aldol reaction between cyclic ketones (cyclohexanone and cyclopentanone) and several substituted benzaldehydes. Reactions were carried out using water, this being the best reaction medium examined. Screening of these catalysts showed that compounds bearing the most hydrophobic acyl chains [4-phenylbutanoate and 4-(pyren-1-yl)butanoate] provided better results. The latter catalysts were successfully used in only 2 mol% at room temperature without additives to give aldol products in excellent stereoselectivities. These results demonstrate that derivatization of the proline moiety with the proper simple hydrophobic substituent in the 4-position can furnish highly active and stereoselective catalysts without the need of additional chiral backbones in the molecule. Finally, an explanation of the observed stereoselectivities in the presence of water is provided. [source] Efficient Heterogeneous Asymmetric Catalysis of the Mukaiyama Aldol Reaction by Silica- and Ionic Liquid-Supported Lewis Acid Copper(II) Complexes of Bis(oxazolines)ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2 2008S. Doherty Abstract Lewis acid complexes based on copper(II) and an imidazolium-tagged bis(oxazoline) have been used to catalyse the asymmetric Mukaiyama aldol reaction between methyl pyruvate and 1-methoxy-1-trimethylsilyloxypropene under homogeneous and heterogeneous conditions. Although the ees obtained in ionic liquid were similar to those found in dichloromethane, there was a significant rate enhancement in the ionic liquid with reactions typically reaching completion within 2,min compared with only 55,% conversion after 60,min in dichloromethane. However, this rate enhancement was offset by lower chemoselectivity in ionic liquids due to the formation of 3-hydroxy-1,3-diphenylbutan-1-one as a by-product. Supporting the catalyst on silica or an imidazolium-modified silica using the ionic liquid or in an ionic liquid-diethyl ether system completely suppressed the formation of this by-product without reducing the enantioselectivity. Although the heterogeneous systems were characterised by a drop in catalytic activity the system could be recycled up to five times without any loss in conversion or ee. [source] An Improved Protocol for the Direct Asymmetric Aldol Reaction in Ionic Liquids, Catalysed by Onium Ion-Tagged ProlinesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2007Marco Lombardo Abstract Two onium ion-tagged prolines, imidazolium bis(trifluoromethylsulfonyl)imide-substituted proline 6 and butyldimethylammonium bis(trifluoromethylsulfonyl)imide-substituted proline 7, were synthesised and their catalytic activity in the direct asymmetric aldol condensation was studied in ionic liquids. For the reaction of acetone with various aldehydes, using 5,% of the catalyst, the yields of the aldols varied between 50,85,% while the ee values were in the 80,85,% range. Other ketones were studied too, the yields obtained in those cases being in the 35,78,% range while the enantioselectivities varied between 75,94,%. [source] Asymmetric Direct Vinylogous Aldol Reaction of Furanone Derivatives Catalyzed by an Axially Chiral Guanidine Base,ANGEWANDTE CHEMIE, Issue 10 2010Hitoshi Ube Dr. Auf die Base kommt es an: Die erste hoch enantioselektive direkte vinyloge Aldolreaktion von dihalogenierten oder ,-Thio-substituierten Furanonen mit Aldehyden verwendet eine axialchirale Guanidin-Base als Katalysator. Die Reaktion bietet leichten Zugang zu enantiomerenangereicherten ,-substituierten Butenoliden. [source] ChemInform Abstract: Intramolecular Aldol Reaction of N-Acylated (2-Aminophenyl)-,-oxoacetic Acids: Rapid Access to Tri- and Tetracyclic 1,2-Dihydroquinolin-2(1H)-ones.CHEMINFORM, Issue 37 2010Malik Hellal Abstract All substrates are prepared following the sequence A)/B) shown for examples (III). [source] ChemInform Abstract: New Indenyl Phosphinooxazoline Complexes of Iron and Their Catalytic Activity in the Mukaiyama Aldol Reaction.CHEMINFORM, Issue 35 2010Matthew Lenze Abstract It is demonstrated that a new iron-indenyl PHOX complex is efficient for the title reaction of the 1-siloxy 1-methoxyethene with aromatic aldehydes. [source] ChemInform Abstract: Highly Enantioselective Synthesis of Tertiary Alcohols: C2 -Symmetric N,N,-Dioxide-Sc(III) Complex Promoted Direct Aldol Reaction of ,-Ketoesters and Diazoacetate Esters.CHEMINFORM, Issue 16 2010Fei Wang Abstract ChemInform 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. [source] ChemInform Abstract: Construction of Contiguous Tetrasubstituted Chiral Carbon Stereocenters via Direct Catalytic Asymmetric Aldol Reaction of ,-Isothiocyanato Esters with Ketones.CHEMINFORM, Issue 16 2010Tatsuhiko Yoshino Abstract ChemInform 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. [source] ChemInform Abstract: Merrifield Resin Supported Ionic Liquids/L-Proline as Efficient and Recyclable Catalyst Systems for Asymmetric Aldol Reaction.CHEMINFORM, Issue 14 2010Zuli Wang Abstract ChemInform 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. [source] ChemInform Abstract: Chiral Amine/Chiral Acid as an Excellent Organocatalytic System for the Enantioselective Tandem oxa-Michael,Aldol Reaction.CHEMINFORM, Issue 10 2010Shu-Ping Luo Abstract ChemInform 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. [source] ChemInform Abstract: Direct Catalytic Asymmetric Aldol Reaction of ,-Keto Esters with Formaldehyde Promoted by a Dinuclear Ni2 -Schiff Base Complex.CHEMINFORM, Issue 1 2010Shinsuke Mouri Abstract ChemInform 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. [source] ChemInform Abstract: The Ion Tag Strategy as a Route to Highly Efficient Organocatalysts for the Direct Asymmetric Aldol Reaction.CHEMINFORM, Issue 23 2009Marco Lombardo Abstract ChemInform 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. [source] ChemInform Abstract: N-Tosyl-(Sa)-binam-L-prolinamide as Highly Efficient Bifunctional Organocatalyst for the General Enantioselective Solvent-Free Aldol Reaction.CHEMINFORM, Issue 15 2009Gabriela Guillena Abstract ChemInform 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. [source] ChemInform Abstract: Protonated Arginine and Lysine as Catalysts for the Direct Asymmetric Aldol Reaction in Ionic Liquids.CHEMINFORM, Issue 10 2009Marco Lombardo Abstract ChemInform 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. [source] ChemInform Abstract: A Novel DNA-Catalyzed Aldol Reaction.CHEMINFORM, Issue 5 2009Gaojun Sun Abstract ChemInform 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. [source] ChemInform Abstract: Use of (S)-5-(2-Methylpyrrolidin-2-yl)-1H-tetrazole as a Novel and Enantioselective Organocatalyst for the Aldol Reaction.CHEMINFORM, Issue 21 2008Sok-Teng Tong Abstract ChemInform 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. [source] ChemInform Abstract: Organocatalytic Asymmetric Aldol Reaction of Ketones with Isatins: Straightforward Stereoselective Synthesis of 3-Alkyl-3-hydroxyindolin-2-ones.CHEMINFORM, Issue 5 2008Jia-Rong Chen Abstract ChemInform 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. [source] ,-Chloroacetone as a Donor in the BINAM-L-prolinamide-Organocatalyzed Aldol Reaction: Application to the Enantioselective Synthesis of ,,,-Epoxy Ketones.CHEMINFORM, Issue 48 2007Gabriela Guillena Abstract ChemInform 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. [source] Highly Enantioselective Organocatalytic Direct Aldol Reaction in an Aqueous Medium.CHEMINFORM, Issue 43 2007Vishnu Maya Abstract ChemInform 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. [source] Catalytic Enantioselective Alkylative Aldol Reaction: Efficient Multicomponent Assembly of Dialkylzincs, Allenic Esters, and Ketones Toward Highly Functionalized ,-Lactones with Tetrasubstituted Chiral Centers.CHEMINFORM, Issue 42 2007Kounosuke Oisaki Abstract ChemInform 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. [source] | |||||||||||||||||||||||||