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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
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Σοφιαδής, Εμμανουήλ Ν
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Thesis advisor
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Βασιλικογιαννάκης, Γεώργιος
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Reviewer
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Στρατάκης, Εμμανουήλ
Σμόνου, Ιουλία
Κατερινόπουλος, Χαράλαμπος
Νεοχωρίτης, Κωνσταντίνος
Δημάδης, Κωνσταντίνος
Σπύρος, Απόστολος
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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.
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Language |
Greek |
Subject |
2- ενάλες |
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2-enals |
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2-ene-1 |
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2-ενε-1,4-διόνες |
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4-diones |
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4-pyrrolin-2- one |
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4-πυρρολιν-2-όνες |
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Cascade reactions |
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Diarylsilylprolinol |
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Furans |
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Organocatalysis |
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Singlet oxygen |
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cyclopent-2-enone |
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Αλυσιδωτές διεργασίες |
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Κυκλοπεντ-2-ενόνες |
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Οξυγόνο απλής κατάστασης |
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Οργανοκατάλυση |
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Σίλυλο δι- άρυλο προλινόλη |
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Φουράνια |
Issue date |
2020-07-28 |
Collection
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School/Department--School of Sciences and Engineering--Department of Chemistry--Doctoral theses
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Type of Work--Doctoral theses
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Permanent Link |
https://elocus.lib.uoc.gr//dlib/f/d/7/metadata-dlib-1595503265-552222-6630.tkl
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Views |
629 |