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Showing 1 to 20 of 38 for “"Ylide"”.
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Carbonyl ylide cycloadditions of dicobalt carbonyl complexes of propargylic aldehydes
The intermolecular, three-component carbonyl ylide cycloaddition of a diazo compound, aldehyde, and carbon-carbon multiple bond is a powerful method to construct five-membered oxygen heterocycles. An adjacent dicobalt hexacarbonyl cluster permits the expansion of the scope of this process to …
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Asymmetrische Synthese ausgehend von allylischen Sulfoximinen: neuartige Gamma-Aminosäuren und cyclische Aminosulfoxonium Ylide
… elucidation of new cyclic aminosulfoxonium ylides. Homoallylic sulfoximines were activated by N-methylation. Treatment with base induced a five-step one-pot domino reaction in the course of which two new ring systems were established stereoselectively. The proposed structures were confirmed …
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Rhodium(II)-Stabilized Vinylcarbenes: Synthetic Applications in Ylide, Cyclopropanation, and C-H Insertion Reactions
… methyl trans-styryldiazoacetate react with benzylideneaniline is described; the products of the cascade reaction are complex bicyclic pyrrolidines. An evaluation of reaction conditions for the formation of bicyclic pyrrolidine determined that slow addition of two equivalents of methyl …
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The Synthesis and Reactions of 2-Diazo-4,5-Bis(trifluoromethyl)imidazole, a Carbene Precursor to Stable Ylide and Hypervalent Compounds
… length of 1.089 A. It may be considered as an ylide of dinitrogen.
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Preparation of Pyridinium and Diaminocarbonium Barbituric Acid Ylides
… it was established that these compounds have a ylide-type structure with strong charge separation inside the molecule. 5-Ylide-pyridinium-methyl barbituric acid derivatives were investigated with the isolation of 4-dimethylamino-1-(2,4,6-trioxohexahydro- pyrimidin-5-ylide-methyl)-pyridinium as …
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An investigation of the chemistry of lithiotriphenylphosphineacetylmethylene
… under a nitrogen atmosphere at -78º. This ylide anion reacted selectively with alkyl halides to form γ-substituted 13-keto phosphonium ylides. Subsequent ionization of triphenylphosphine-(3-phenylpropionyl)methylene with n-butyllithium at -78° followed by alkylation produced …
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Efforts Toward the Total Synthesis of Asparagamine A
… approach utilizes an intramolecular azomethine ylide 1,3-dipolar cycloaddition reaction as the key step. Generation of the azomethine ylide species is achieved via sequential vinylogous amide O-sulfonylation and desilylation. Several strategies designed to construct the fully oxygenated …
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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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Keteneylidenetriphenylphosphorane as a 'C2O building block' in the synthesis of highly functionalised tetramic and tetronic acids
… was established by reaction of a phosphorus ylide (Ph3PCCO) with a variety of amino esters. A number of derivatives were prepared with varying substituents at the 3- and 5-positions of the nitrogen heterocycle. A general method for the preparation of highly functionalised furan-2-ones from …
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Mechanistic and Synthetic Studies of Oxidopyrylium Cycloaddition Reactions
… in these cycloadditions, the oxidopyrylium ylide, and factors to which it is influenced by. Previously our lab found that 3-hydroxy-4-pyrone-derived dimers can be used as ylide surrogates in cycloaddition reactions. We found through kinetic and computational work that this was occurring via …
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Synthetic Studies of the Rubellin Natural Products
… of a rearrangement reaction of reactive iodonium ylide intermediates. First described are select syntheses of complex anthraquinone monomers and dimers within the past 20 years. The scientific community has found deep interest in the anthraquinone class of compounds due to their therapeutic …
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I. Efforts Toward the Total Synthesis of the Stemofoline Alkaloids II. Preliminary Development of a Method to Prepare 1,2-Cis-2-Acetamido-2-Deoxyglycopyranoses
… cycloaddition of a non-stabilized azomethine ylide as a key step. These studies culminated in the first non-racemic synthesis of the fully-oxygenated tricyclic core of the stemofoline alkaloids. Furthermore, a novel synthetic method to prepare alpha-linked C2-acetamido glycoconjugates is …
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Construction of carbocycles via oxonium ylides generation and rearrangement: towards the synthesis of taxol
… carbocycles by tandem catalytic oxonium ylide generation and rearrangement. The novel method in which intramolecular reaction of metal carbenoids with α-vinyl ethers and subsequent [2,3]-rearrangement of the cyclic oxonium ylide intermediates has been used as a powerful strategy to …
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The synthesis and reactivity of functionalised alkyl transition metal complexes
… Two types of cationic products, namely the ylide complexes [CpM(CO)nCH₂L]+ or the disubstituted complexes [CpML₂(CO)n-l]+ (M = Fe, n = 2; M = W, n = 3) were obtained, depending on the halide (X), the ligand (L), the metal (M) and the solvent used. The variables X, L, M and the solvent used …
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A Nanosecond Laser Spectrophotometric and Product Investigation of the Chemistry of Fluorenylidene
Fluorenylidene has been generated by laser flash photolysis of diazofluorene in fluid solution. The chemistry of fluorenylidene has been studied in hexafluorobenzene, cyclohexane, cyclopropane, spiropentane, acetonitrile, and Freon 113 spectroscopically, and chemically by isolation and …
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ΣΥΝΘΕΣΗ ΚΑΙ ΜΕΛΕΤΗ ΤΩΝ ΙΔΙΟΤΗΤΩΝ ΝΕΩΝ ΙΩΔΟ-ΥΛΙΔΙΩΝ Β-ΔΙΣΟΥΛΦΟΝΩΝ
… IS TO STUDY THE CHEMICAL PROPERTIES OF IODONIUM YLIDES OF B-DISULFONES. I-YLIDES OF B- DISLFONES REACT WITH A LARGE VARIETY OF CLASSES OF ORGANIC COMPOUNDS UNDER THERMAL OR PHOTOCHEMICAL CONDITIONS. THE PRODUCTS ARE ISOLATED USUALLY BY COLUMN CHROMATOGRAPHY. WHEN AN IODONIUM YLIDE WAS HEATED OR …
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The Asymmetric Total Synthesis of Cephalotaxine
… cycloaddition of a non-stabilized azomethine ylide as the key steps. This work has resulted in an asymmetric total synthesis of cephalotaxine in 24 steps and 0.9% overall yield.
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Contributions to benzothiopyran chemistry
… comparable reactivity, reaction with phosphorus ylides occurs regiospecifically at the 3-position. The use of excess ylide promoted an a-ketol rearrangement and gave a stabilised ylide which has been characterised by Xray crystallography. 2,3-Dihydro-4H-[1]benzothiopyran-3-ones, the synthesis of …
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Activated Phosphate Reagents for the Synthesis of Functionalized Oligophosphates
… to generate a trimetaphosphate based phosphorus ylide capable of P–C bond formation through Wittig chemistry. Ring opening of these substituted trimetaphosphate products with hydroxides results in linear triphosphate derivatives. Adenosine and uridine 5′-tetra- and 5′-pentaphosphates were …
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