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Showing 1 to 20 of 100 for “"CYCLOADDITIONS"”.
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Enantioselective nucleophile-catalyzed cycloadditions
… Two enantioselective phosphine-catalyzed [3+2] cycloadditions of allenoates are detailed in Chapter 2. A method for the asymmetric synthesis of cyclopentenes via a [3+2] cycloaddition of allenoates with enones is first discussed. This is followed by a report of our efforts to extend this [3+2] …
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Methodology and total synthesis enabled by cycloadditions
Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2023-09-01 without embargo terms
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The Total Synthesis of (-)-Detoxinine and (+)-Casuarine Using Tandem [4 + 2]/[3 + 2] Nitroalkene Cycloadditions and Cycloadditions of Nitroethylene
The first synthesis of (+)-casuarine, a pentahydroxy pyrrolizidine alkaloid of the alexine/australine subclass, is described. The key step is a tandem inter [4+2]/inter [3+2] nitroalkene cycloaddition involving an oxygenated nitroalkene, chiral vinyl ether, and vinyl silane dipolarophile, which …
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Synthesis of pyrrolizidine diols via azide-diene cycloadditions
The generality of the [4+1] annulation methodology in the context of natural product synthesis was demonstrated by extending its applicability to the heteroatom (nitrogen) case thus allowing access to the alkaloid field. This novel methodology involved the intramolecular union of a hypovalent …
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Cycloadditions to 1-azetines and 1-azetin-4-ones
… ring incorporating a C=N bond.1,3-Dipolar cycloadditions and [4+2] cycloadditions to the C=N bond of 1-azetines would yield bi-cyclic systems of related structure to the beta-lactam nucleus of beta-lactam antibitics.Thus, three 1-azetine systems (2-4) were prepared by alkylation of their …
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Explorations of Intramolecular [5+2] Cycloadditions of Ring-Constrained Vinylcyclopropanes
The first example of a [5+2] cycloaddition reaction wherein the olefin of the vinylcyclopropyl moiety is constrained in a carbocycle was explored, and possible reasons on the lack of reactivity of the substrate were studied. A simple model substrate was synthesized and subjected to cycloaddition …
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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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Intramolecular [4+2] cycloadditions of conjugated enynes : scope and mechanism
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1996.
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Synthesis of pyridines via [4 + 2] cycloadditions of vinylallenes with azadienophiles
… 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 synthesis of tricyclic pyridines based on intramolecular propargylic ene/imino Diels-Alder …
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Interfacial Nitrone 1,3-Dipolar Cycloadditions for Modification of Monolayer Protected Gold Nanoparticles
The ability to manipulate the interfacial environment of monolayer protected gold nanoparticles (MPNs) is critical for the understanding and development in their potential application. While various methods for the incorporation of functionality onto MPNs are available, many require tedious …
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Site-Specific Labelling of Nucleic Acids by Catalyst-Free 1,3-Dipolar Cycloadditions
… reactions. Both nitrile oxide-alkyne cycloadditions (NOAC) and strain-promoted azide-alkyne cycloadditions (SPAAC) were explored. The possiblitity for ‘pre-synthetic’ functionalisation was demonstrated using non-nucleosidic phorphoramidite building blocks generated by NOAC. Three …
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Isoxazole Linked siRNA Cholesterol Conjugates by Catalyst Free Nitrile Oxide/Alkyne Cycloadditions
… cholesterol conjugates by nitrile oxide/alkyne cycloadditions. Novel alkyne and oxime modified cholesterol derivatives were prepared and demonstrated to be efficient dipolarophiles and dipole precursors. Chapter 5 embraces the synthetic success discussed in chapters 3 and 4 and applies them to …
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Intramolecular Heterodiene (4+2) Cycloadditions of Nitrosoalkenes, Nitroalkenes, and Vinyl Nitrosonium Ions
Intramolecular 4+2 cycloadditions with three related heterodienes: nitrosoalkenes, vinyl nitrosonium ions, and nitroalkenes are discussed. An appraisal was made for each diene in terms of the ease of generation of the heterodiene, the ability to undergo facile cycloaddition, and the facility for …
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The total synthesis of salvilenon : intramolecular [4+2] cycloadditions of conjugated enzynes
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1994.
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Intramolecular [4 + 2] cycloadditions of conjugated enynes with highly strained cyclic alkenes
… 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 carbocycles involving cycloadditions of cyclobutenones with conjugated enynes.
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Synthesis of heterocyclic compounds via intramolecular [4+2] cycloadditions of conjugated enynes
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1997.
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Intermolecular [3+2] Cycloadditions of Imino-isocyanates to Access β-Amino Carbonyl Compounds
In modern synthetic organic chemistry, chemists are driven to develop efficient methods for important C-C and C-N bond formation reactions. The challenge lies with establishing new uses for readily available substrates. In this regard, the synthesis of β-aminocarbonyl compounds from alkenes remains …
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The Tandem Inter [4+2]/[3+2] Cycloadditions of Nitroalkenes: The Bridged-Mode
… Intramolecular $\lbrack 3 + 2\rbrack$ cycloadditions afforded stable nitroso acetals that were reduced using nickel boride to provide enantiomerically enriched aminocyclopentanes in good yields and high enantiomeric excess. Additionally, the Lewis acid employed in the $\lbrack 4 + …
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Development of Nickel and Zirconium Mediated Cycloadditions for the Synthesis of Substituted Pentacene
The regioselectivity of the [2+2+2] cycloaddition of nickel-benzynes and 1,3-diynes could be maintained when asymmetrically substituted 1,3-diynes were employed. The ability to incorporate an asymmetric 1,3-diyne into the oligoacene backbone provided substituents that could be differentiated in …
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