Abstract
Tetraazafulvalenes can be cross-coupled (palladium-catalyzed)
with alkenes or acetylenes. Although Suzuki conditions fail, the
Heck and the Sonogashira methods are useful tools for functionalizing
tetraazafulvalenes. Starting from the tetraiodoaryl derivative 2b, four arylic iodine atoms could be replaced
by acrylic acid esters, various styrenes or cylohexenes thus furnishing
the new heterofulvalenes 4a-d. Under analogous conditions, the tetraaldehyde 4e could be obtained by employing allylic
alcohol as the coupling partner. Cross coupling reactions using
the Sonogashira method yielded a series of highly functionalized
tetraazafulvalenes 6a-p, 7a-d. In an analogous manner, deeply colored
pyrazino-fused tetraazafulvalenes 9a-c as well as imidazo-fused derivatives 10b-d,
which show strong fluorescence, were prepared. First steps towards
dendritic heterofulvalenes have been realized as illustrated by
the synthesis of derivative 6q.
Key words
arenes - cross-coupling - heterocycles - palladium - tetraazafulvalenes
