Devaki Sadanam Venugopal, Hrishikesh (2024) Studies on selected organocatalytic vinylogous aldol, decarboxylative Mannich, and Gosteli-Claisen rearrangement reactions. Doctoral (PhD) thesis, Memorial University of Newfoundland.
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Abstract
Isatin-derived 3-hydroxy-2-oxindoles bearing a γ-butenolide moiety at the 3 position and isatin-derived spiropiperidinones are of interest due to their biological activities and potential applications in medicinal chemistry. The organocatalytic asymmetric direct vinylogous aldol reaction of N-methylisatins and γ-butenolides to provide 3-hydroxy-2-oxindole derivatives was developed. A series of N-diaminophosphoryl aminothiourea catalysts were synthesized, and their utility for the stereoselective formation of 3-hydroxy-2-oxindole derivatives was examined. Details of these studies are described in Chapter 1. The organocatalytic asymmetric decarboxylative Mannich reaction of isatin N-Boc imines and α,β-unsaturated β’-keto acids to synthesize βʹ-amino α,β-unsaturated enones, which are precursors of spiropiperidine-based oxindoles was developed. The use of a squaramide-based catalyst was found to be optimal, and it provided enantiomerically enriched βʹ-amino α,β-unsaturated enones in good yields. These βʹ-amino α,β-unsaturated enones were converted to isatin-derived spiropiperidinones by employing an intramolecular aza-Michael reaction. These studies are described in Chapter 2. The organocatalytic Gosteli-Claisen rearrangement of 2-t-butoxycarbonyl allyl vinyl ether to provide a functionalized quaternary stereocenter containing building block was investigated. A modular synthesis of several new, chiral cyclic phosphoramide-based thioureas, formamidines, and thiosemicarbazones was developed, and these phosphoramides were examined for their ability to catalyse the Gosteli-Claisen rearrangement. The results of these studies are described in Chapter 3.
| Item Type: | Thesis (Doctoral (PhD)) |
|---|---|
| URI: | http://research.library.mun.ca/id/eprint/16592 |
| Item ID: | 16592 |
| Additional Information: | Includes bibliographical references -- Restricted until September 30, 2025 |
| Keywords: | organocatalytic, vinylogous aldol, Mannich, Gosteli-Claisen, asymmetric |
| Department(s): | Science, Faculty of > Chemistry |
| Date: | June 2024 |
| Date Type: | Submission |
| Library of Congress Subject Heading: | Organochlorine compounds; Mannich reaction; Pharmaceutical chemistry; Asymmetric synthesis; Claisen rearrangement; Isatin; Oxindoles |
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