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You searched for +publisher:"Dalhousie University" +contributor:("Ian R. Pottie"). Showing records 1 – 2 of 2 total matches.

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Dalhousie University

1. Moulins, Jonathan. Synthesis of Heterocycles via Chemoselective Geminal Acylation of 2-Methoxyoxazolidines, E/Z Isomerization in the Metathesis of Allyl Alcohol Derivatives with a First-Generation Ruthenium Catalyst, and Interception of Nazarov Reaction Intermediates of Allenyl Vinyl Ketones with Arenes.

Degree: PhD, Department of Chemistry, 2013, Dalhousie University

Heterocycles were prepared through the geminal acylation of 2-methoxyoxazolidines with 1,2-bis(trimethylsilyloxy)cyclobutene. It was found that when water was excluded from the standard reaction conditions, regioselectivity of the ring expansion step was reversed, resulting in preferential rupturing of the endocyclic C-O bond instead of the C-N bond. Further cyclization resulted in the generation of 6,5-fused ring systems. The aqueous procedure was found to be applicable to 1,2-bis(trimethylsilyloxy)cyclopentene, resulting in the analogous 6,6-fused ring systems, while the anhydrous procedure failed to promote ring expansion. Tricyclic 6,5,6-fused ring systems were obtained with meso-7,8-bis(trimethylsilyloxy)bicyclo[4.2.0]oct-7-ene using the anhydrous procedure, while the intermediate generated under aqueous conditions failed to undergo ring closing. Allylic alcohol derivatives were subjected to homodimerization in the presence of a first-generation ruthenium catalyst. Previous work suggested that thermodynamic equilibration to the E-isomer was not a significant process for first-generation catalysts. However, product E/Z ratios were, in general, observed to increase significantly over time. In addition, an atmosphere of ethylene promoted reversion to the terminal olefins, leading to rapid E/Z equilibration, albeit at the expense of yield. Brief exposure to ethylene over the course of reaction resulted in a high E/Z ratio in a moderate yield. A 6,6,5-fused ring system was synthesized via the tandem Nazarov cyclization-intramolecular Friedel-Crafts alkylation of the corresponding allenyl vinyl ketone. The presence of electron donating substituents on the arene, as well as a two-carbon tether linking the arene to the allenyl vinyl ketone, were crucial to the success of the reaction. The intermolecular trapping of an allenyl vinyl ketone with substituted arenes was also investigated. Trapping occurred primarily at the electronically preferred position a, while sterically encumbered substrates tended to trap preferentially at the less hindered position c. Surprisingly, 1,3,5-trisubstituted arenes trapped almost exclusively at position a, having overcome significant steric crowding, demonstrated by hindered rotation about the newly formed carbon-carbon bond. Advisors/Committee Members: Graham J. Bodwell (external-examiner), Mark Stradiotto (graduate-coordinator), Frances L. Cozens (thesis-reader), Ian R. Pottie (thesis-reader), Robert L. White (thesis-reader), D. Jean Burnell (thesis-supervisor), Not Applicable (ethics-approval), Not Applicable (manuscripts), Not Applicable (copyright-release).

Subjects/Keywords: Organic; Synthesis; Methodology

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Moulins, J. (2013). Synthesis of Heterocycles via Chemoselective Geminal Acylation of 2-Methoxyoxazolidines, E/Z Isomerization in the Metathesis of Allyl Alcohol Derivatives with a First-Generation Ruthenium Catalyst, and Interception of Nazarov Reaction Intermediates of Allenyl Vinyl Ketones with Arenes. (Doctoral Dissertation). Dalhousie University. Retrieved from http://hdl.handle.net/10222/37454

Chicago Manual of Style (16th Edition):

Moulins, Jonathan. “Synthesis of Heterocycles via Chemoselective Geminal Acylation of 2-Methoxyoxazolidines, E/Z Isomerization in the Metathesis of Allyl Alcohol Derivatives with a First-Generation Ruthenium Catalyst, and Interception of Nazarov Reaction Intermediates of Allenyl Vinyl Ketones with Arenes.” 2013. Doctoral Dissertation, Dalhousie University. Accessed July 09, 2020. http://hdl.handle.net/10222/37454.

MLA Handbook (7th Edition):

Moulins, Jonathan. “Synthesis of Heterocycles via Chemoselective Geminal Acylation of 2-Methoxyoxazolidines, E/Z Isomerization in the Metathesis of Allyl Alcohol Derivatives with a First-Generation Ruthenium Catalyst, and Interception of Nazarov Reaction Intermediates of Allenyl Vinyl Ketones with Arenes.” 2013. Web. 09 Jul 2020.

Vancouver:

Moulins J. Synthesis of Heterocycles via Chemoselective Geminal Acylation of 2-Methoxyoxazolidines, E/Z Isomerization in the Metathesis of Allyl Alcohol Derivatives with a First-Generation Ruthenium Catalyst, and Interception of Nazarov Reaction Intermediates of Allenyl Vinyl Ketones with Arenes. [Internet] [Doctoral dissertation]. Dalhousie University; 2013. [cited 2020 Jul 09]. Available from: http://hdl.handle.net/10222/37454.

Council of Science Editors:

Moulins J. Synthesis of Heterocycles via Chemoselective Geminal Acylation of 2-Methoxyoxazolidines, E/Z Isomerization in the Metathesis of Allyl Alcohol Derivatives with a First-Generation Ruthenium Catalyst, and Interception of Nazarov Reaction Intermediates of Allenyl Vinyl Ketones with Arenes. [Doctoral Dissertation]. Dalhousie University; 2013. Available from: http://hdl.handle.net/10222/37454

2. Marx, Vanessa. Development of the Interrupted Nazarov Cyclization of Allenyl Vinyl Ketones, with Application to the Total Synthesis of the Cyclooctane Natural Product Roseadione.

Degree: PhD, Department of Chemistry, 2011, Dalhousie University

The development of the interrupted Nazarov cyclization of allenyl vinyl ketones is presented. The intermediate oxyallyl cation, derived from an allenyl vinyl ketone, may be trapped efficiently by a divergent array of nucleophilic species generating functionalized cyclopent-2-enone products. Allenyl vinyl ketones are also a versatile source of cyclic molecules via a tandem reaction sequence terminated via reaction with acyclic dienes, cyclic dienes, aza-heterocycles, electron-rich alkenes, or styrenes by the formation of an additional ring by a [4 + 3] and/or [3 + 2] cyclization or by the formation of one additional carbon-carbon bond. The bicyclic compounds generated by these processes are densely substituted, and would be difficult to access as succinctly in other ways. The products of these interrupted Nazarov reactions generally reflect excellent regio- and stereoselectivity in the trapping reaction. In some instances, equilibrating conditions were shown to enhance the proportion of one product at the expense of another or to provide a different carbon skeleton. This process appears fairly general, and can be conducted with unsubstituted or alkyl, aromatic, or heteroaromatic allenyl vinyl ketones. The exceptional affinity of allenyl vinyl ketones to undergo interrupted Nazarov reactions is likely a result of the increased longevity of the intermediate oxyallyl cation, due in part to the increased resonance stabilization provided by the allene unit. The high regioselectivity noted in the trapping process was computationally and experimentally confirmed to be a result of a localization of the positive charge in the intermediate oxyallyl cation. The application of this recently developed methodology towards the synthesis of the natural product (+)-roseadione is also described. The tandem Nazarov/[4 + 3] cascade of allenyl vinyl ketones provides a unique manner in which to access the tricyclic core of this cyclooctanoid natural product, a molecule which, to date, has never been synthesized. Advisors/Committee Members: Dr. Louis Barriault (external-examiner), Dr. Mark Stradiotto (graduate-coordinator), Dr. David L. Jakeman (thesis-reader), Dr. Ian R. Pottie (thesis-reader), Dr. Laura Turculet (thesis-reader), Dr. D. Jean Burnell (thesis-supervisor), Not Applicable (ethics-approval), Not Applicable (manuscripts), Not Applicable (copyright-release).

Subjects/Keywords: Allenes; Allenyl Vinyl Ketones; Interrupted Nazarov Reactions; Oxyallyl Cations; [4 + 3] Cyclizations; [3 + 2] Cyclizations; Bicyclic Ring Systems; Eight Membered Ring Systems

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Marx, V. (2011). Development of the Interrupted Nazarov Cyclization of Allenyl Vinyl Ketones, with Application to the Total Synthesis of the Cyclooctane Natural Product Roseadione. (Doctoral Dissertation). Dalhousie University. Retrieved from http://hdl.handle.net/10222/13885

Chicago Manual of Style (16th Edition):

Marx, Vanessa. “Development of the Interrupted Nazarov Cyclization of Allenyl Vinyl Ketones, with Application to the Total Synthesis of the Cyclooctane Natural Product Roseadione.” 2011. Doctoral Dissertation, Dalhousie University. Accessed July 09, 2020. http://hdl.handle.net/10222/13885.

MLA Handbook (7th Edition):

Marx, Vanessa. “Development of the Interrupted Nazarov Cyclization of Allenyl Vinyl Ketones, with Application to the Total Synthesis of the Cyclooctane Natural Product Roseadione.” 2011. Web. 09 Jul 2020.

Vancouver:

Marx V. Development of the Interrupted Nazarov Cyclization of Allenyl Vinyl Ketones, with Application to the Total Synthesis of the Cyclooctane Natural Product Roseadione. [Internet] [Doctoral dissertation]. Dalhousie University; 2011. [cited 2020 Jul 09]. Available from: http://hdl.handle.net/10222/13885.

Council of Science Editors:

Marx V. Development of the Interrupted Nazarov Cyclization of Allenyl Vinyl Ketones, with Application to the Total Synthesis of the Cyclooctane Natural Product Roseadione. [Doctoral Dissertation]. Dalhousie University; 2011. Available from: http://hdl.handle.net/10222/13885

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