Rapid Access to Benzimidazo[1,2‑a]quinoline-Fused Isoxazoles via Pd(II)-Catalyzed Intramolecular Cross Dehydrogenative Coupling: Synthetic Versatility and Photophysical Studies

An efficient and atom-economical palladium-catalyzed intramolecular cross dehydrogenative coupling (CDC) reaction has been developed for the construction of highly π-conjugated benzimidazo­[1,2-a]­quinoline-fused isoxazole scaffolds using molecular oxygen as sole oxidant. The approach portrayed wide substrate scope with good functional group tolerance and depicted a useful tool for the generation of fluorescence active compounds with high quantum yield. Synthetic versatility of the method via Fe-catalyzed reductive isoxazole ring cleavage toward pyridine, pyrimidine, pyrazole fused heteropolycyclic compounds has been showcase.