Studies on the photocyclization reaction of 8‐styryl‐substituted coralyne derivatives

The photoreactivity of four 8‐styryl‐substituted coralyne derivatives was examined by UV/VIS‐ and 1 H‐NMR‐spectroscopy. Except for the dimethylamino‐substituted derivative, these cationic azoniaheterocyclic dyes undergo photocyclization that most likely proceeds through an initial E ‐ Z ‐isomerization of the double bond. Subsequent oxidation of the intermediates under aerobic conditions gave the pyrrolo‐annelated quinolizinium derivatives as final products, thus providing a useful synthetic route to polycyclic azoniahetarene derivatives. The 6‐(4‐chlorophenyl)‐substituted pyrroloquinolizinium derivative was isolated on a preparative scale, and the investigation of its photophysical properties revealed significantly red‐shifted absorption ( λ abs = 465–480 nm) and emission bands ( λ fl = 550–562 nm) in comparison to the parent coralyne and the styryl‐substituted derivatives.