Untersuchungen zur Stereoselektion in einer Photo-Diels-Alder-Cycloaddition

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The photocycloadditions of 2-(dialkylamino)propenenitriles to 1-acetylnaphthalene in d6 benzene as solvent proceed with high directional selectivity by fast and photoreversible formation of [2+2]-cycloadducts (tetrahydrocyclobuta[a]naphthalenes) followed by a slower and photoirreversible formation of [4+2]-cycloadducts (1,4-dihydro-1,4-ethanonaphthalenes). With increasing duration of irradiation the product pattern is shifted towards a mixture of diastereomeric [4+2]-adducts in which the isomer with endo-orientation of the dialkylamino group in the ethano bridge is predominating. The endo-[4+2]-adduct of 2-(dipropylamino)-propenenitrile to 1-acetylnaphthalene was isolated in pure form, and its configuration was unambiguously corroborated by a single crystal X-ray structure analysis. Upon thermal activation it is converted in a small fraction via an intermediate biradical to the thermodyna-mically more stable exo-epimer before it is decomposed to the educts. Methyl 1-naphthoate reacts in the same way as 1-acetylnaphthalene but less efficiently.
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Dokumententyp:
Wissenschaftliche Abschlussarbeiten » Dissertation
Fakultät / Institut:
Fakultät für Chemie
Dewey Dezimal-Klassifikation:
500 Naturwissenschaften und Mathematik » 540 Chemie
Stichwörter:
Radicophilicity, Structure determination, Cycloreversion, NMR-spectroscopy, Photo-Diels-Alder addition, Cyanoenamines, Captodative substitution, Triplet state
Beitragende:
Prof. Dr. Döpp, Dietrich [Betreuer(in), Doktorvater]
Prof. Dr. Gärtner, Wolfgang [Gutachter(in), Rezensent(in)]
Sprache:
Deutsch
Kollektion / Status:
Dissertationen / Dokument veröffentlicht
Datum der Promotion:
25.01.2005
Dokument erstellt am:
25.01.2005
Dateien geändert am:
11.05.2010
Medientyp:
Text