Abstract:
We have developed a direct method for the
synthesis of polyring-fused imidazo[1,2-a]pyridines via a coppercatalyzed
annulation of electrophilic benzannulated heterocycles
with 2-aminopyridine and 2-aminoquinoline. From 3-nitroindoles
and 2-aminopyridine, we could synthesize tetracenes, viz., indolefused
imidazo[1,2-a]pyridines, and by starting from 2-aminoquinoline,
we could generate pentacenes, viz., indolo-imidazo[1,2-
a]quinolines. In addition, we could also extend the methodology
toward the synthesis of benzothieno-imidazo[1,2-a]pyridines
starting from 3-nitrobenzothiophene. Furthermore, the basic
photophysical properties of these synthesized heteroacenes were
evaluated.
