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Showing 1 to 20 of 26 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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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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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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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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Towards incorporation of catalytic function into small folded peptide scaffolds
… environment and is able to modestly enhance aldol condensation and retro-aldol reactions. Finally, a new trimeric Apa oligomer structure is evaluated as a functional peptide scaffold. Initially, the structural requirements of the motif are explored through a series of sequence modifications. …
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Stereoselective synthesis of all-C quaternary stereocentres using non-enolisable 1,3-dialdehydes
… with allylation, hydroxyallylation and aldol reactions to give products containing two or three contiguous stereocentres, including an all-C quaternary stereocentre, with good stereocontrol. Interestingly it was found that the diastereoselection of monoaddition was different when the …
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