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Showing 1 to 20 of 71 for “"annulation"”.
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New oxy-dihydrofuran annulation methodology
… of 11 was addressed. A new oxydihydrofuran annulation methodology was developed following the above investigation. The addition of the lithium dienolate generated from ethyl 2-bromo-4-[(tert-butyldimethylsilyl)oxy]-butenoate 105 to aldehydes provided vinyloxiranes of type 127 as single …
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Synthesis of ipomeamarone via the [2+3] dihydrofuran annulation
… in an overall intermolecular [2+3] dihydrofuran annulation.
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Annulation strategies for the synthesis of azulenes and polycyclic nitrogen heterocycles
Highly convergent annulation strategies have been developed for the synthesis of azulenes and polycyclic nitrogen heterocycles. Specifically, substituted azulenes have been synthesized via a ring expansion-annulation strategy based on n-halo diazo ketones. The method employs the use of readily …
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Application of organosilanes in [3 + 2] annulation approaches to carbocyclic compounds
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1999.
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Total synthesis enabled by nickel-catalyzed transformations: Dearomative carboamination and methylenecyclopropane annulation
… of a nickel-catalyzed methylenecyclopropane annulation for the concise preparation of the core scaffold of ineleganolide. The current frontline synthesis towards the norditerpenoid and the final transformations remaining for its completion are described. Towards this end, we developed a novel …
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[4+1] cyclopentene annulation in the total synthesis of pentalenene type sesquiterpenes
The generality of the [4+1] cyclopentene annulation was demonstrated by the total synthesis of (±)-pentalenene and its C-9 epimer which were prepared in a stereocontrolled manner in analogy with the synthesis of (±)-isocomene, (±)-hirsutene and (±)-pentalenic acid. The key features of this …
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Synthesis of indoles via palladium-catalyzed annulation of aryl chlorides and internal alkynes
A palladium-catalyzed preparation of 2,3-disubstituted indoles from commercially available and relatively inexpensive reagents, o-chloroacetanilide and internal alkynes, is reported. The system is efficient in delivering 2,3-disubstituted indoles in good to excellent yield with a high level of …
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[4 + 1] annulation reactions of (trialkylsilyl)ketenes : synthesis of substituted indanones and cyclopentenones
… and heterocyclic compounds. A new [4 + 1] annulation strategy for the synthesis of substituted 2-indanones, based on the reaction of TAS-arylketenes with trimethylsilyl diazomethane, has been developed. In addition, a new class of carbenoid reagents for our previously reported [4 + 1] …
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Cascade Annulation and Ring-Opening Reactions of Castagnoli-Cushman-Derived Allylic and Benzylic Thiomorpholinonates
<p>Sulfur-containing compounds are prevalent in antibiotics, essential amino acids, bacterial RNA, food flavors, and enzymes. The divalent sulfur atom introduces a metabolic liability from a drug discovery standpoint. Indeed, it is quite telling that all the top ten best-selling drugs in 2012 …
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Intramolecular [4+1] pyrroline annulation as a general method for the synthesis of pyrrolizidine alkaloids
… the heteroatom equivalent of the carbenoid [4+1] annulation as a method or alkaloid synthesis. [See docment for associated image]
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Vinylcyclopropanation of enones in [2+3] cyclopentene annulation: application to the total synthesis of (-)-retigeranic acid
… corresponding cyclopentenes in an overall [2+3] annulation process. [see document for diagram of chemical compounds] The reactions of 161a with other electrophiles such as ketones, α,ß-unsaturated esters and α,ß-unsaturated aldehydes were also investigated. The possibility of asymmetric induction …
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Synthesis and rearrangements of vinylcyclopropanes in a [2+3] cyclopentene and oxycyclopentene annulation methodology approach to (-)- specionin
… to cyclopentenes in an overall [2+3] annulation sequence. During the course of these studies, a new rearrangement pathway of these vinylcyclopropanes to bridged [3.2.n] bicyclic systems was discovered thus establishing a new [3+4] annulation technology. The extension of the [2+3] …
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Intramolecular [4 + 2] cycloadditions of conjugated enynes with highly strained cyclic alkenes
… directed towards the development of a [4 + 3] annulation strategy for the synthesis of seven-membered carbocycles involving the intramolecular [4 + 2] cycloadditions of conjugated enynes with cyclopropenes. A new [4 + 4] annulation method has been developed for the synthesis of eight-membered …
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Development of Palladium-Catalyzed and Iodine-Mediated Formal [4+1] Annulation Protocols. Progress toward a New Fulvene-Based Organocatalytic Platform for Carbonyl α-Functionalization
… development of a new palladium-catalyzed [4+1] annulation protocol is described. This process involves an oxidative palladium-catalyzed intramolecular vinylcyclopropanation of dienyl beta-ketoesters followed by a magnesium iodide-mediated vinylcyclopropane-cyclopentene rearrangement. The …
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Total syntheses of (+̲)-Methyl cantabrenonate, (+̲)-Methyl epoxycantabronate, and (+̲)-Crinipellin B
… part of the thesis. Two methylenecyclopentane annulation sequences previously developed in our laboratories played key roles in the syntheses of (±)-13, (±)-14 and (±)-15. A new cyclopentenone annulation procedure was elaborated to assemble the last 5-membered ring of crinipellin B (15). The …
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Development of a Diastereoselective [4+2]-Annulation of Vinyl Carbodiimides With Chiral N-Alkyl Imines and Its Application to the Synthesis of the Batzelladine Alkaloids: Total Synthesis of (+)-Batzelladine a and (-)-Batzelladine D
A diastereoselective [4+2] annulation of vinyl carbodiimides with chiral N-alkyl imines has been developed to access the stereochemically rich anti-fused polycyclic guanidine cores of the batzelladine alkaloids. Application of this strategy, together with additional key steps such as a long-range …
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Cascade Transformations in Organic Synthesis: I. The Interception of Carbene Alkyne Metathesis Intermediates II. Photo-Activation of Hydrazones III. Organocatalyzed Cascade Conjugate Addition/Aldol Annulation of Organoboronates
… organocatalyzed tandem conjugate addition/Aldol annulation of organoboronates was discussed in the last chapter. A variety of nucleophiles showed good compatibility with heterocycles. In addition, the strength of boron enolate intermediates were examined by intercepting with various electrophiles.
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Studies toward Augmented Carbene/Alkyne Cascade Reactions and Ruthenium Catalysts for Propargylic Substition
… part describes an improvement of a Robinson annulation for the synthesis of aplykurodinone 1. Alkyne/cascade reactions are highly effective processes in organic chemistry, and they can provide complex molecules in a single synthetic method. Our approach is based on a rhodium-catalyzed …
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Synthesis of pyridines via [4 + 2] cycloadditions of vinylallenes with azadienophiles
… in organic synthesis. This thesis describes new annulation strategies for the synthesis of highly substituted pyridines that involve [4 + 2] cycloadditions of vinylallenes with azadienophiles. Part II of this thesis describes a unimolecular, formal [2 + 2 + 2] cycloaddition strategy for the …
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