The study of enolate anions derived from [beta]-enaminoketones and their use in synthetic approaches to the mitomycin skeleton.
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| Format: | Thesis Book |
| Language: | English |
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[College Station, Tex.] :
Little,
1978.
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| Online Access: | Link to OAKTrust copy Link to ProQuest copy |
| Abstract: | Studies were directed towards the preparation of the pyrrolizidinoenone ring structure as a possible mitosane precursor. Early approaches focused on reactions of azabicyclic hexanes with β-chloroenones. Expansion of the expected intermediate bicyclo aziridinium enone salts had the potential of forming the pyrrolizidinoenone ring skeleton. Products were obtained which derived from nucleophilic capture of these quarternary intermediates by other nucleophiles present in the reaction media. An alternative approach required the preparation of enolate anions of halomethylpyrrolidine enaminoketones which could undergo intramolecular cyclization to form pyrrolizidine ring systems. For this purpose model studies were conducted to determine conditions controlling enolate formation at the α'- or γ-carbons of β-heteroatom substituted enones. Anions of these systems could be prepared by reaction of the substrates with lithium diisopropylamide under conditions of kinetic or thermodynamic control and examined spectroscopically using ¹³C-NMR. A parallel study involved the preparation of the same enolates of enaminoketones and vinylogous esters followed by quenching with benzyl bromide. Characterization of the alkylation products obtained indicated the site of proton abstraction was at either the α'- or γ-carbon of these enones. The α'- or γ-anions of these cyclic β-substituted enones could be obtained cleanly under conditions of kinetic or thermodynamic control except for the thermodynamically derived anion of 3-ethoxy-2-cyclo-hexenone which appeared to undergo intermolecular reactions. The preparation of anions of β-heteroatom substituted acyclic enones under kinetically controlled conditions resulted in a mixture of α'- or γ-anions, while under thermodynamic control the γ-anions of these enones could be prepared cleanly. The results of the alkylation study indicated the enolate precursors displayed the same characteristics as those observed spectroscopically. Based on these studies attempts were made to effect "B" ring closure by intramolecular nucleophilic displacement of halide ions of halomethylpyrrolidine enone adducts to generate pyrrolidinoenones and pyrrolidinoquinones. In each case alternative modes of reaction of these enolates were observed. |
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| Item Description: | Vita. "Major subject: Chemistry." |
| Physical Description: | xiv, 158 leaves : illustrations, graphs ; 28 cm |
| Bibliography: | Includes bibliographical references (leaves 121-123). |