Photocycloadditionen von 2-donorsubstituierten Propennitrilen an Cumarinderivate - Photocycloadditions of 2-donor substituted propenenitriles to coumarin derivatives
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.
Advisor:Prof. Dr. Dietrich Döpp
School:Universität Duisburg-Essen, Standort Essen
Source Type:Master's Thesis
Keywords:chemie gerhard mercator universitaet
Date of Publication:05/22/2001