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Identifier 000430875
Title Οργανοκαταλυόμενη παραγοντοποίηση 4-πυρρολιν-2-ονών, κυκλοπεντ-2-ενονών και 2-ενε-1,4-διονών με 2-ενάλες
Alternative Title Organocatalyzed derivatization of 4-pyrrolin-2-ones, cyclopent-2-enones and 2-ene-1,4-diones with 2-enals
Author Σοφιαδής, Εμμανουήλ Ν
Thesis advisor Βασιλικογιαννάκης, Γεώργιος
Reviewer Στρατάκης, Εμμανουήλ
Σμόνου, Ιουλία
Κατερινόπουλος, Χαράλαμπος
Νεοχωρίτης, Κωνσταντίνος
Δημάδης, Κωνσταντίνος
Σπύρος, Απόστολος
Abstract In this dissertation, three organocatalysed synthetic methodologies yielding complex and synthetically useful cyclic structures are described. A common feature of these methodologies is the use of small organic molecules as catalysts (organocatalysts) which facilitates the desired transformation with excellent regio-, diastereo- and enantioselectivity. Another common feature is the exploitation of the green and sustainable reagent, singlet oxygen, for the preparation of the precursors of the organocatalytic reactions. In Chapter 2, the first study of the reactivity of 4-pyrrolin-2-ones with 2-enals under iminium catalysis is presented. The reaction yields hifh value bicyclic lactams with high site, diastereo- and enantioselectivity through a one pot process. After having found the optimum reaction conditions, the scope of the reaction regarding 4-pyrrolin-2-ones and 2-enals was investigated. In every case, the reaction shows high site, diastereo- and enantioselectivity which was attributed to an ion-pair interaction in the transition state. The final products bear a chiral quaternary center and have the important skeleton of the ubiquitous pyrrolizidine alkaloids. In Chapter 3, the first double 4,4’-functionalization of cyclic-2-enones with 2- enals is presented. The reaction exploits iminium catalysis in order to activate the 2-enals resulting to a highly site-selective functionalization of cyclic-2-enones. The methodology has a divergent profile being able to form the corresponding dienes upon dehydration or the hydroxyl keto esters upon hydrogenation with excellent diastereoand enantioselectivity. Starting from essentially flat molecules, a rapid increase in molecular complexity takes place yielding 3-dimensional structures with up to 5 stereogenic centers. All the aforementioned transformations could be implemented as one pot processes showing good to very good yields. Lastly, further and highly selective derivatization of hydroxy keto esters is described which results in isomeric bicyclic lactones. In Chapter 4, an organocatalyzed cascade synthetic methodology is presented which exploits the multisite and multi-type reactivity of 2-ene-1,4-dione with 2-enals under iminium catalysis. The transformation yields high value cyclopentanones in a highly diastereo- and enantioselective manner. The 2-ene-1,4-dione was synthesized through a mild photoxygenation protocol utilizing singlet oxygen. Further derivatization of the cyclopentanones results in cis-hydrindane formation through an aldol-annulation process. The methodology exploits the sustainable nature (atomeconomy) and unique reactivity of the singlet oxygen to transform a furan nucleus (which can be derived from biomass) into a 2-ene-1,4-dione, which is itself an excellent candidate for cascade reactions. The organocatalyzed step uses a mixture of EtOH/H2O as a green solvent mixture in which the cascade process takes place leading to the final product. Many of the basic principles of the green chemistry are satisfied in the developed synthetic methodology including: catalysis, environmental friendly solvents, reduction of the intermediate compounds, atom economy, step economy etc.
Language Greek
Subject 2- ενάλες
4-pyrrolin-2- one
Cascade reactions
Singlet oxygen
Αλυσιδωτές διεργασίες
Οξυγόνο απλής κατάστασης
Σίλυλο δι- άρυλο προλινόλη
Issue date 2020-07-28
Collection   Faculty/Department--Faculty of Sciences and Engineering--Department of Chemistry--Doctoral theses
  Type of Work--Doctoral theses
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