Zircon PrVO₄: an efficient heterogeneous catalyst for tandem oxidative synthesis of 2,3-disubstituted quinoline derivatives

The current study addresses the usage of inherent redox couplets in PrVO4 crystallizing in a zircon-type structure for tandem oxidative transformation. Monophasic PrVO4, synthesized using a solution combustion synthesis method, showed a tetragonal zircon-type structure in its PXRD pattern (S.G. I4(1)/amd). The tetragonal symmetry of the zircon PrVO4 was also confirmed from electron microscopic and vibrational spectroscopic measurements. From XPS analysis, the existence of redox couplets Pr3+/Pr4+ and V4+/V5+ in PrVO4 was established. The catalytic utility of zircon PrVO4 for one-pot synthesis of 2,3-disubstituted quinolines through the oxidative tandem reaction of 2-aminobenzylalcohols with 1,3-dicarbonyl compounds has been demonstrated. This highly efficient method proceeds under molecular oxygen, tolerates different functional groups, and produces various substituted quinoline derivatives in good to excellent yields. The important features of the process are the easy workup, simple catalyst recovery, and reusability.