Excited state transformations of heterostilbenes: Pathways to polycyclic skeleta

For the past 40 years M. Šindler-Kulyk's group has been studying, among other things, excited state reactivity of various heteroaromatic analogues of o-vinylstilbenes, o-vinylstyryl- and o-phenylenedivinylene-aromatic heterocycles, simply called o-vinyl-heterostilbenes and di-heterostilbenes. A concise overview of this vast research is presented. To date furan, pyrrole, sydnone, thiophene, oxazole, and most lately pyridine nuclei were incorporated into the basic stilbene-type skeleton. The photochemistry of these compounds is of great importance as it gives a pathway to new polycyclic products that are taxing or even impossible to obtain via ground state synthetic organic chemistry approaches. It is also an interesting subject because of illustration of diverse photoproducts formed by introducing different substituents into the system, thereby changing the conformation and electronic distribution in the molecule. Star representatives of the group of polycycles that were obtained are the benzobicyclo[3.2.1]octadiene photoproducts, which might show promising biological activity.