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Showing 1 to 20 of 51 for “"Ketene"”.
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Cycloadditions of ketene acetals with conjugated carbonyl compounds and chemistry of the resulting products
Contains fulltext : mmubn000001_027259145.pdf (Publisher’s version ) (Open Access)
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Lewis Base Activation of Lewis Acids in Asymmetric Aldol Reactions of Silyl Ketene Acetals
… 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 chiral silyl cation. This …
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Synthesis, study and application of silyl ketene imines in Lewis base catalyzed carbonyl addition
… carbons a range of disubstituted N-silyl ketene imines has been investigated as latent nucleophiles for additions to carbonyl compounds. In the presence of silicon tetrachloride and a catalytic amount of chiral bis-phosphoramide, N-silyl ketene imines underwent extremely rapid additions to …
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Studies in Asymmetric Catalysis: Lewis Base Catalyzed, Enantioselective Addition of Trimethylsilyl Cyanide, Trimethylsilyltrifluoromethane, and Glycolate-Derived Silyl Ketene Acetals to Aldehydes
… for the addition of glycolate-derived silyl ketene acetals to aldehydes. The sense of diastereoselectivty could be modulated by changing the size of the substituents on the silyl ketene acetals. In general, the trimethylsilyl ketene acetals derived from methyl glycolates with a large …
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Spectroscopic and theoretical studies of small molecules.
… is concerned with two contrasting molecules - ketene (H2CCO) and methylene chloride (CH2CI2). High resolution (~0.05cm-1) infrared studies of ketene were carried out and complete analyses performed to the A1 species vibrations v1-v4, allowing the determination of revised vibrational frequencies …
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Lewis Base Catalysis: I. Catalytic Enantioselective Aldol Additions of Methyl Trichlorosilyl Ketene Acetal to Ketones. II. Catalytic Enantioselective Alpha-Additions of Isocyanides to Aldehydes
The first catalytic, enantioselective alpha-addition reaction of isocyanides has been demonstrated with a SiCl4·bisbinaphthyldiamine phosphoramide catalyst. Good yields have been obtained with aromatic, heteroaromatic, conjugated non-aromatic and non-branched aliphatic aldehydes. Aromatic, …
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Cracking Meldrum's Acid: Lowering the Temperature
… incompatibilities is required. Utilisation of ketenes as a carbonyl source may be one such protocol. Ketenes are highly reactive intermediates that can be produced and reacted under the same reaction conditions, including at a neutral pH. Ketenes therefore present an attractive way to produce …
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Cracking Meldrum's Acid: Lowering the Temperature
… incompatibilities is required. Utilisation of ketenes as a carbonyl source may be one such protocol. Ketenes are highly reactive intermediates that can be produced and reacted under the same reaction conditions, including at a neutral pH. Ketenes therefore present an attractive way to produce …
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Scope and stereochemistry of carbon-carbon bond formation via addition of carbon nucleophiles to nitrones
… addition of Grignard reagents and silyl ketene acetals to acyclic and cyclic nitrones have been studied. A 4:1 selectivity favoring axial addition was observed in the reactions of cis-3,5-dimethyl-2,3,4,5-tetrahydropyridine N-oxide with both methyl and phenyl Grignard reagents and the …
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Asymmetric Lewis base catalysis: I. Lewis base catalyzed halogenation and development of an enantioselective bromocycloetherification reaction; II. enantioselective addition of silyl ketene imines to carbonyl electrophiles
Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2012-06-15T13:39:00Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 2 Thesis-6-12.docx: 11084823 bytes, checksum: 0609048b408ae3adf1f485e3a9dde5d3 (MD5) Burk_Matthew.pdf: 14255171 bytes, …
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Hydrophobization of Cellulose-Based Fibers for Packaging Applications with Alkyl Ketene Dimers (AKD) and Food-Grade Waxes via Supercritical Impregnation with Carbon Dioxide – Experimental and Thermodynamic Modeling Approaches
This modified material has applications in food packaging, where frequently water-repellant surfaces are required. This method is preferable to traditional coating methods because it sizes across the entire thickness of the substrate rather than just the surface and can be used for non-planar …
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Intramolecular Anodic Olefin Coupling Reactions: Synthesis Of Nitrogen- And Oxygen-Heterocycles
… the key step anodic coupling of an alcohol and a ketene dithioacetal. The key to the success of the oxidative cyclization reaction is the use of lithium methoxide as a base instead of the commonly used weak base, 2,6-lutidine. The synthesis demonstrates that a vinyl substituted ketene dithioacetal …
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Strategies for the synthesis of bioactive compounds: biomimetic approaches to the Salinosporamides and the hexadehydro-Diels-Alder reaction
… event involving an uncatalyzed intramolecular ketene-ketone [2+2] cycloaddition of an amidoketene precursor. We also propose a transition state that places the C2 substituent pseudo-equatorial, allowing for enhanced stereoselectivity during bis-cyclization. Enolate formation from a thioester …
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I. [2 +2] Cycloaddition and benzannulation of 2-iodoynamides and application to the construction of highly substituted indoles : II. Synthesis of furo[2,3-g]thieno[2,3-e]indole via a benzannulation strategy
… and regioselective [2 + 2] cycloaddition with ketene to produce cyclobutenones that are useful synthetic building blocks. Reaction of 2-iodoynamides and vinylketenes generated in situ from cyclobutenones proceeds via a pericyclic cascade mechanism to produce highly substituted 2-iodoanilines. …
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Keteneylidenetriphenylphosphorane as a Versatile C-2 Building Block Leading to Tetronic Acids with Potential Herbicidal and anti-HIV Activity
The cumulated ylide keteneylidenetriphenylphosphorane (Ph3PCCO) has shown great potential in the construction of heterocyclic compounds. The formation of heterocycles arises from the unique dipolar electronic structure of the cumulated ylide, which combines ylide and ketene properties. Upon …
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Synthesis of benzocarbazoles, indoloquinolines and indolonaphthridines from thermolysis of benzoenynyl ketenimines and carbodiimides
… are described. Like enyne-allene and enyne-ketene systems, these enyne-hetereocumulenes undergo cycloaromatization through two competing biradical mechanisms under thermal conditions and therefore could serve as potential DNA cleaving agents. The resultant nitrogen-containing hetereocyclic …
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New Methods for the Formation of Methyl Bearing Stereogenic Centers via Methylketene Dimerization and Free Radical Additions to Allyl Bromides
… been developed using: 1) dimerization of methylketene and 2) a free radical-based addition/elimination reaction involving allyl bromides. The first method, the asymmetric dimerization of methyl ketene, followed by an asymmetric aldol reaction and the appropriate functional group manipulations …
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Part I. Total Synthesis and Structural Revision of (±)-Tricholomalides A and B. Part II. Synthetic Studies towards (+)-Cortistatin A
… from a homo-Robinson annulation, followed by a ketene-olefin [2+2] cycloaddition to introduce the lactone ring. Then a Grignard-type reaction appended the isopropenyl moiety, and the synthesis of tricholomalides A and B was achieved. During the course of synthesis, the structures of …
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Thermochemistry and kinetic analysis on radicals of acetaldehyde + O2, allyl radical + O2 and diethyl and chlorodiethyl sulfides
… paths and kinetics in oxidation and pyrolysis. Ketene is one important product resulting from acetaldehyde oxidation; thus thermochemistry plus isomerization and conversion reactions of ketene are also analyzed. Enthalpies of formation are determined using isodesmic reaction analysis at the CBSQ …
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