Global ETD Search

1	Synthesis of 5-Substituted Isoxazolidines by [3 plus 2] Cycloaddition of Nitrones Generated in an Unusual Way from Nitrosobenzene and Styrene Kang, Jun Yong 20 January 2010 (has links) A new synthetic method toward 5-substituted isoxazolidines by [3 plus 2] cycloaddition of nitrones generated from nitrosobenzene and styrene was discovered. The formation of nitrones from nitrosobenzene and mono-substituted aromatic styrenes was demonstrated. The cycloaddition reactions between styrenes and nitrosobenzenes work well when a moderate excess of styrenes was employed. The labeling studies support that cleavage of the styrene double bond occurred and accounted for all the carbons in the starting materials and products. A [3 plus 2] dipolar cycloaddition is implicated by the available mechanistic data and allows for the rapid assembly of various substituted isoxazolidines directly from nitrosobenzenes, electron deficient alkenes, and styrene. [3+2] dipolar cycloaddition isoxazolidine nitrone
2	Novel Aza-Prins Cyclization and [3+2] Dipolar Cycloaddition Toward N-Heterocyclic Molecules and Studies Toward the Total Synthesis of Borrecapine Liu, Xiaoxi 01 January 2014 (has links) Highly functionalized 5 or 6-membered nitrogen-containing heterocyclic moieties are highly prevalent in pharmaceuticals reagents, alkaloid natural products, organocatalysts, as well as useful building blocks in organic synthesis. Novel approaches to synthesizing these structures are sought therefore to maximize their accessibility. Within the well-established organic synthesis artillery, electrocyclic reactions serve as the predominant strategy to construct pyrrolidine and piperidine analogues. In this dissertation, the first stereocontrolled assembly of indolizidines from 2-allylic proline esters by aza-Prins reaction, and endo-selective synthesis of highly functionalized 5-vinylic pyrrolidines from benzylic and allylic azomethine ylide using novel [3+2] dipolar cycloaddition are described. These methodologies then culminate in a formal synthesis of Borreria alkaloid, borrecapine, by using an unprecedented sulfonyl group substituted dipolarophile. Finally, new directions in our laboratory to make pyrrolidine scaffolds are included in the last chapter of this thesis. [3+2] dipolar cycloaddition aza-Prins camphorsulfonic acid formaldehyde sulfonyl vinyl pyrrolidine Chemistry
3	Cycloaddition dipolaire [3+2] à partir d'hétérocycles aromatiques N-aminés Perreault, Christian January 2008 (has links) Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal. Ylures de N-iminoquinolinium Azométhine imine Désaromatisation Catalyse Acide de Lewis Cycloaddition dipolaire-[3+2] Dipolarophile Auxiliaire chiral Informations mécanistiques Cycloadition dipolaire homo[3+2] N-Iminoquinolinium ylide Azinethine imine Dearomatization Catalysis Lewis acid [3+2] Dipolar cycloaddition Dipolarophile Chiral auxiliary Mechanistic insight Homo [3+2] dipolar cycloaddition
4	Cycloaddition dipolaire [3+2] à partir d'hétérocycles aromatiques N-aminés Perreault, Christian January 2008 (has links) Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal Ylures de N-iminoquinolinium Azométhine imine Désaromatisation Catalyse Acide de Lewis Cycloaddition dipolaire-[3+2] Dipolarophile Auxiliaire chiral Informations mécanistiques Cycloadition dipolaire homo[3+2] N-Iminoquinolinium ylide Azinethine imine Dearomatization Catalysis Lewis acid [3+2] Dipolar cycloaddition Dipolarophile Chiral auxiliary Mechanistic insight Homo [3+2] dipolar cycloaddition

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