Cu(II)-Promoted Cascade Synthesis of Fused Imidazo-Pyridine-Carbonitriles

A Cu­(II)-promoted
synthesis of an aza-fused N-heterocycle having
a benz-imidazopyridine scaffold is developed via an addition–cyclization
reaction followed by an Ullmann-type C–N coupling between o-iodoanilines and γ-ketodinitriles.
This protocol features a broad substrate scope, giving products in
32–84% yields. The compounds show excellent photoluminescence
properties having two absorption maxima in the region between 270–280
and 338–350 nm and emission maxima in the range of 502–533
nm. The HOMO–LUMO energy gap of 3.49–3.57 eV was determined
using Gaussian 09 at the B3LYP/6-31G (d, p) basis set level. We also
demonstrated a few postsynthetic modifications.