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Showing 1 to 20 of 25 for “"enol ether"”.
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Oxocarbenium Ion and Alkene Metathesis Strategies for the Synthesis of Complex Cyclohexanes
… OCCs for non-cyclic oxocarbenium ions and enol-ether nucleophiles. These reactions were expected to give highly oxygenated cyclic enol ether precursors for carba- and C- pyranosides with trans 3,4-diols. However, in all cases, complex mixtures of products that suggested multiple deleterious …
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I. Solution Photochemistry of Camphor II. Synthesis and Solution Photochemistry of 2, 2-Dimethylcyclobutanone
… is also formed, while in n-heptane a bicyclic enol ether is formed instead of the acetal. Deuterium labelling experiments indicate that the acetal is formed by reaction of a bicyclic oxycarbene with ethanol, and that the enol ether is formed from this oxycarbene in part by reaction with …
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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
… 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 %) catalyzed the addition of the silyl enol ether to benzaldehyde to give aldol …
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Trifluoroethyl enol ethers, dienol ethers, and acetals: an investigation of their preparations, reactivities, and synthetic applications
… studied were trifluoroethoxy substituted ketals, enol ethers, and dienol ethers. The ketal and enol ether work involved developing methodology for the large scale preparation of these structures as well as studies detailing their behavior. For the TFE ketals, preparation involved an acid-catalyzed …
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Conjugate Additions and Transposition of the Allylic Alcohols of Enol Ethers of 1, 2-Cyclohexanedione.
<p>A variety of protected enolic forms of 1, 2-cyclohexanedione was prepared as substrates for conjugate addition studies using organocopper reagents. The sequence involved the enol ether preparation via the enolate, alkylation with an organometalic reagent, and oxidative rearrangement with …
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Nitroalkene (4+2) cycloadditions of achiral and chiral vinyl ethers. The stereochemical consequence of the Lewis acid promoter and studies toward the total synthesis of (+)-pretazettine
Chiral enol ether dienophiles derived from (1R,2S)-($-$)-2-phenylcyclohexanol and (R)-($-$)-2,2-diphenylcyclopentanol (($-$)-6 have been found to provide high levels of asymmetric induction in tandem inter (4+2) /intra (3+2) nitroalkene cycloadditions. Either enantiomeric series of tandem …
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Towards the Synthesis of the Oxaspirobicyclic Unit of Tetronothiodin
… a! non%selective! α%hydroxylation! of! a! silyl! enol! ether!moiety,! resulting! in! the! formation! of! a! mixture!of!two!diastereoisomers! in! a!5:3! ratio,! including! the!more!hindered! isomer!with! the! desired! stereochemistry! at! the! pro%spiro! centre! as! the! minor! adduct.! However,! …
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Biomimetic synthesis of natural products via reactions of ortho-quinone methides
… virgatolide B has been developed. A simplified enol ether was employed for the biomimetic [4+2] cycloaddition reaction to afford a simplified virgatolide B analogue. An isomerised compound containing a cis fused ring junction, thought to arise via a [4+2] cycloaddition of an ortho-quinone …
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Intramolecular (4+2) -Cycloadditions of Three Heterodienes: Nitrosoalkenes, Nitroalkenes, and Z-Alpha,beta-Unsaturated Aldehydes
… engaged in intramolecular cycloadditions with enol ethers and vinyl sulfides at ambient temperature. The yield and stereoselectivity of the tricyclic octahydronaphthalene (6-6)- and hexahydroindene (6-5)-oxazine cycloadducts varied. In the enol ether cases, the success of the cycloaddition …
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Investigation of the synthesis and thermal rearrangements of 1,2,3,4,5-Pentaphenyl-2,4,-Cyclopentadiene Alkyl Ethers
… 1,2,3,4,5-pentaphenyl-2,4-cyclopentadiene alkyl ethers was investigated. It was determined that the most efficient route to these ethers was not the most generally accepted route to ethers - the Williamson Reaction - but rather a solvolysis reaction between …
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Structure elucidation and studies relating to the synthesis of plasmalopentaene-12
The glycerol enol ether, fecapentaene-12, is a direct acting fecal mutagen that is formed in the lower portion of the gastrointestional tract by anaerobic bacteria. The biological precursor to fecapentaene-12 is a natural product of mammalian origin whose role in the etiology of colon cancer is …
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Continued Progress Towards Efficient Syntheses Of Cephalostatin North 1 Analogs
… is the process efficient synthesis of the a key enol ether intermediate as the gateway to the synthesis of 26,27-dihydroxy North 1 and other spiroketal analogs. The use of silyl triflates for tandem one pot kinetic resolution of diastereomers is also presented.</p>
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Synthesis and rearrangements of vinylcyclopropanes in a [2+3] cyclopentene and oxycyclopentene annulation methodology approach to (-)- specionin
The addition of lithium dienolate 130, formed from ethyl 2-bromocrotonate, to enones and aldehydes yielding vinylcyclopropanes and vinyloxiranes was optimized. Various methods, pyrolytic and nonpyrolytic, were examined for the rearrangement of the resulting vinylcyclopropanes to cyclopentenes in an …
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Studies relating to fecapentaene-12
The glyceryl enol ether fecapentaene-12 (FP-12) is a direct-acting mutagen that is formed by bacteria in the lower part of the gastrointestinal tract from a precursor of unknown structure. Two major unsolved questions concerning FP-12 are the structure of its precursor and the nature of its …
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Synthetic studies of heparan derivatives: Glycosyl couplings and post-glycosylative modifications
… donors with various acceptors. The 4’-enol ether can be modified by stereoselective epoxidation and ring opening by a dithiocarbamate auxiliary, which can be activated by copper(I) salts for carbon nucleophile addition with terminal L-<em>ido</em> configuration. We also explored …
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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
… 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 selectivities. Enantioselectivities are highly dependent on the …
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Marcus Theory Applied To Acetal Cleavage And Aldol Reactions
… of DMOP hydrolysis proceeding through an enol ether. This mechanism is neither predicted nor observed for TMOA hydrolysis. The specific acid catalyzed and uncatalyzed rate constants for hydrolysis are for DMOP k{dollar}rmsb{lcub}H+{rcub}=(2.5pm0.3)times10sp3 …
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Novel Organic Transformations Arising from Gold(I) Chemistry
… the intramolecular addition of silyl enol ether onto Au(I) activated alkynes, resulting in a 5-exo dig cyclization. The first part (Chapter 1) of this thesis discusses the development of a Au(I) catalyzed polycyclization reaction inspired by this transformation. The reaction …
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Synthesis and structure-activity relationships of ring D alkyl 19-norsteroids
… for alkylation experiments. Estrone 3-methyl ether was converted into the derived 17β-hydroxy 16-ketone by standard methods. This conversion involved the introduction of a 16α-hydroxyl group by bromination-hydrolysis, followed by base-mediated rearrangement of the hydroxy ketone to the …
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Synthesis and structure-activity studies of skeletally modified estradiol analogues
… the 13α-isomer, which underwent sequential silyl enol ether formation and dehydrosilylation into 3-methoxy-13α-estra-1,3,5(10), 15-tetraen-17-one, which failed to undergo conversion into the corresponding 3-methoxy-13α-estra-1,3 ,5( 10), 14, 16-pentaen-17-yl acetate required for cycloaddition …
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