J. Geenevasen, H. Cerfontain
Sep 2, 2010
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Recueil des Travaux Chimiques des Pays-Bas
Abstract
The photo-isomerization of (Z)-3-(6′,6′-dimethyl-2′-methylenecyclohexylidene)-1-propene [(Z)-3a] has been studied under conditions of triplet photosensitization, using benzophenone as sensitizer, and direct irradiation with λ 254 nm. Under the former conditions, only Z-E isomerization is observed leading to a photostationary state with {[Z]/[E]}pss = 1.77 and 1.50 for benzene and chloroform as the respective solvent. Upon direct irradiation, the primary products are (E)-3a, the tricyclodecene 11a and the bicyclooctene 12a, formed in an initial ratio of 9/2.0/1.0. The two polycyclic isomers 11a and 12a apparently result from the excited singlet state. NOE 1N NMR measurements illustrate hat (Z)-3a is present mainly in a s-transoid conformation.