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

Abstract

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.