Aubele, Danielle L.
(2004)
Mechanistic and Stereochemical Studies of Photoinduced Electron Transfer Initiated Cyclization Reactions: The Role of Nitrogen. The Aqueous Prins Reaction and Efforts Towards the Total Synthesis of (+)-Dactylolide.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
A novel method for catalytic electron transfer initiated cyclization reaction for the formation of cyclic acyl aminals through a unique method of carbon-carbon ó-bond activation has been developed. This new cyclization strategy employs a potent electrophile, generated by a photoinitiated single electron oxidation of a homobenzylic amide or t-butyl carbamate, which reacts with an appended nucleophile allowing for the formation of cyclic acyl aminals. The Lewis acid-surfactant-combined catalyst (LASC) was employed in a novel method for effecting intramolecular Prins cyclization reactions in water. Acetals of 1,2 and 1,3 di- and tri- substituted alcohols with a tethered allyl silane have been converted to 2,6-syn-tetrahydropyrans. The LASCs are generated in situ by the addition of cerium nitrate to a solution of sodium dodecylsulfate and acetal in water. A heterogeneous reaction environment is created in which the acetal is trapped within the hydrophobic core of the immediately generated micelle. Intarmolecular Prins cyclization is catalyzed upon interaction of the acetal with Lewis acidic cerium cations located at the surface of the micelle. LASC mediated intramolecular Prins cyclization reactions are efficient, high yielding, and an environmentally benign method of generating 2,6-cis-tetrahydropyrans. A highly convergent route towards the total synthesis of the marine macrolide (+)-dactylolide is currently being pursued. The route involves the condensation of two highly functionalized segments of the molecule, an á,â-unsaturated aldehyde and a 1,3-syn-diol, to form a cyclic á,â-unsaturated acetal. Both enantiopure segments arise from vinylogous aldol reactions, providing the three necessary stereocenters. The key synthetic transformation involves intramolecular Prins cyclization of a cyclic á,â-unsaturated acetal with a pendent allylsilane to provide the 2,6-cis-disubstituted-4-methylenetetrahydropyran core of the molecule efficiently and stereoselectively. Other key transformations include a completely trans selective selenoxide-selenate [2,3] sigmatropic rearrangement and the selective oxidation of a primary allylic alcohol in the presence of a secondary alcohol with Dess-Martin periodinane.
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Details
| Item Type: |
University of Pittsburgh ETD
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| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
22 September 2004 |
| Date Type: |
Completion |
| Defense Date: |
18 August 2004 |
| Approval Date: |
22 September 2004 |
| Submission Date: |
18 August 2004 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
dactylolide; electron transfer; Prins |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-08182004-152551/, etd-08182004-152551 |
| Date Deposited: |
10 Nov 2011 20:00 |
| Last Modified: |
15 Nov 2016 13:49 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/9166 |
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