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Showing 1 to 20 of 30 for “"Aldol reactions"”.
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Marcus Theory Applied To Acetal Cleavage And Aldol Reactions
… been determined for four hydroxide catalyzed aldol condensations at 25.0{dollar}spcirc{dollar}C in aqueous solution. The four reactions studied were acetone, acting as carbon acid, with {dollar}alpha,alpha,alpha{dollar}-trifluoroacetophenone and with p-nitroacetophenone, and …
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Chemoenzymatic aldol reactions : applications of a four-enzyme-catalytic cascade reaction
Contains fulltext : 100599.pdf (Publisher’s version ) (Open Access)
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Thiopyran route to polypropionates : simultaneous-two directional and enantiotopic group selective aldol reactions
The sequential aldol reactions of thiopyran derivatives 112 and 119 to rapidly generate hexapropionate building blocks in two carbon-carbon forming steps has been well studied within the Ward group. An extension of this strategy to generate non-racemic tetra- and hexapropionate fragments involved …
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Lewis Base Activation of Lewis Acids in Asymmetric Aldol Reactions of Silyl Ketene Acetals
… chiral phosphoramide catalyzed/SiCl 4 promoted aldol reaction of silyl ketene acetals and silyl dienol ethers with aldehydes. The weakly acidic species, silicon tetrachloride (SiCl 4), is activated by binding of a strongly Lewis basic chiral phosphoramide, leading to in situ formation of a …
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Studies in Asymmetric Catalysis: Lewis Base catalyzed/Lewis Acid Mediated Aldol Reactions of Ketone- and Amide Derived Nucleophiles
… catalyst for highly selective vinylogous aldol reactions between dienolates derived from a variety of alpha,beta-unsaturated carbonyl compounds to aldehydes. These reactions provided high levels of gamma-site selectivity for a variety of substitution patterns on the dienyl unit. Both …
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PART I: ALDOL REACTIONS OF 1,3-OXATHIOLAN-5-ONES. PART II: CAMPHOR AS A CHIRAL DIRECTING AGENT IN ALKYLATIONS OF GLYCINATES.
… only with very reactive alkylating agents.('2,3) Aldol reactions were more successful. 1,3-Oxathiolan-5-ones were reduced with lithium aluminum hydride to 2-mercaptoalcohols, which could be transformed into the 2-(methylthio)alcohols. Part II. Camphor imines of glycinates were prepared from …
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I Peptide isosteric replacement preparation using zinc-mediated chain extension-aldol reactions II Formal synthesis of (+)-Brefeldin A III Zinc-mediated chain extension reactions with substituted carbenoids
… chain extension and tandem chain extension aldol reactions with various aldehydes and ketones. An efficient diastereoselective synthetic route has been developed to approach a proposed inhibitor for HCMV (Human Cytomegalovirus) protease using this zinc-mediated tandem chain extension-aldol …
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Part 1. Lewis Base-Catalyzed Cross-Aldol Reactions of Aldehydes: Preparative and Mechanistic Studies. Part 2. Initial Studies on Lewis Base-Catalyzed Reactions of Silyl Ynol Ethers With Aldehydes
Chiral phosphoramide-catalyzed, enantioselective aldol additions of isobutyraldehyde-derived trichlorosilyl enol ether to aldehydes have been investigated. These aldol additions are general and provide beta-hydroxy aldehydes protected as dimethyl acetals in high yields albeit moderate …
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Lanthanide-Based Precatalysts For Carbon-Carbon Bond-Forming Reactions In Aqueous Media
… of biologically active compounds. The Mukaiyama aldol reaction is a Lewis-acid-catalyzed carbon-carbon bond-forming reaction that has the ability to produce optically active β-hydroxy carbonyls which can be found in many pharmaceuticals and natural products. Because of precatalyst instability …
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Use of organocatalysts in stereoselective organic synthesis
… first transformation involves enantioselective aldol reaction between 2-hydroxy-cyclobutanone with a selection of aromatic aldehyde. The results show that the 2-hydroxycyclobutanone is particularly amenable to solvent-free L-threonine-catalyzed direct aldol reactions with reasonable …
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ALDOL COUPLINGS OF CHIRAL FRAGMENTS WITH KINETIC RESOLUTION: SCOPE AND LIMITATIONS
… a synthetic strategy that involves the stepwise aldol reactions of 6 and 7a to rapidly access stereochemically complex tetrapropionate 8 and hexapropionate synthons 72 or 73. Coupling racemic 7a with any of the four enantioenriched diastereomers 8 with kinetic resolution (KR) is possible with …
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Synthese neuartiger Sulfoximine für die asymmetrische Metallkatalyse
… applicability in asymmetric phenyl transfer reactions onto aldehydes. Enantiomerically enriched diarylmethanols have been prepared by catalyzed asymmetric phenyl transfer reactions onto aromatic aldehydes with use of readily available beta-hydroxysulfoximines as catalysts. As the aryl source, …
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I. Selective Chlorination and Fluorination of Quinols II. Synthetic Study of Strongylophorine-26
… additions to enone, enolate alkylations, aldol reactions, cycloadditions, and rearrangements. Dienone-phenol rearrangement provides the asymmetric route since the stereocenters located in the six-membered ring of various cyclohexadienone were widely using in building larger chiral arrays …
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The Stetter reaction : synthesis of complex spiro Bis-indanes and studies on quaternary centre formation
… reaction, including two novel domino Stetter reactions and preliminary studies on quaternary center formation via the intermolecular Stetter reaction. The N-heterocyclic carbene (NHC) catalyzed domino Stetter-aldol-Michael dimerization of o-formyl chalcone derivatives 36 affords spiro …
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Investigations of transition state geometry in the intramolecular aldol reaction and the intramolecular reaction of allylsilanes with aldehydes
… influence the transition state geometry of the aldol reaction are described. Synthesis of two bicyclic model systems designed to study base-catalyzed intramolecular aldol reactions are reported, along with the effects that various metal counterions, solvents, and additives have on the …
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Development of an organo-and enzyme-catalysed cascade reaction
… combines organo- and enzyme-catalysis in an aldol/aldol cascade for the first time. The bicatalytic, three-component assembly involves two aldol reactions: an organocatalysed reaction and an aldol reaction catalysed by an aldolase. The feasibility of the one-pot reaction was evaluated by …
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Synthesis of Resveratrol and Its Analogs, Phase-Transfer Catalyzed Asymmetric Glycolate Aldol Reaction, and Total Synthesis of 8,9-Methylamido-Geldanamycin
… catalysts (PTC) were developed for glycolate aldol reactions to give differentially protected 1,2-diol products. Silyl enol ether of diphenylmethoxy-2,5-dimethoxyacetophenone reacted to generate benzhydryl-protected products. O-Allyl trifluorobenzyl cinchonium hydrodifluoride (20 mol %) …
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Organokatalytische Synthesen biologisch aktiver Naturstoffe : Totalsynthesen von Amaminol A und B und (+)-Mitsugashiwalacton sowie Synthesen 2,6-disubstituierter Tetrahydropyranen
… The preliminarily investigated selective nitroaldol reactions to generate the precursors of amaminol warrant further studies. In order to complete the synthesis by introducing the aminofunction, aminoacid derivatives from the chiral pool were used. Under optimised Masamune-Roush conditions a …
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