Reactions of photoexcited coumarins and their thia analogues with captodative alkenes have been investigated, with special emphasis on the nature of the excited states and the specific influence of the substrates on regio- and stereoselectivity of the observed [2+2]-photocycloadditions. Aside of two coumarin thiones all coumarins investigated regioselectively add captodative alkenes at the pyranone moeity giving rise to head-to-tail [2+2]-photocycloadducts with donor-endo adducts as prevailing isomers. The observed regio- and stereoselectivities can be best explained if a 1,4-biradical is assumed as intermediate in the photocycloaddition.
| Identifer | oai:union.ndltd.org:DUETT/oai:DUETT:duett-05222001-100519 |
| Date | 22 May 2001 |
| Creators | Neubauer, Stefan |
| Contributors | Prof. Dr. Dietrich Döpp |
| Publisher | Gerhard-Mercator-Universitaet Duisburg |
| Source Sets | Dissertations and other Documents of the Gerhard-Mercator-University Duisburg |
| Language | German |
| Detected Language | English |
| Type | text |
| Format | text/html, application/pdf |
| Source | http://www.ub.uni-duisburg.de/ETD-db/theses/available/duett-05222001-100519/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. Hiermit erteile ich der Universitaet Duisburg das nicht-ausschliessliche Recht unter den unten angegebenen Bedingungen, meine Dissertation, Staatsexamens- oder Diplomarbeit, meinen Forschungs- oder Projektbericht zu veroeffentlichen und zu archivieren. Ich behalte das Urheberrecht[Tue May 22 09:59:55 2001] (eval 35): Bareword found where operator expected at (eval 35) line 2, near |
Page generated in 0.002 seconds