Sulfamic acid-functionalized hydroxyapatite-encapsulated γ-Fe2O3 nanoparticles as a magnetically recoverable catalyst for synthesis of N-fused imidazole-quinoline conjugates under solvent-free conditions

Abstract

Novel conjugated imidazo[1,2-a]pyridine and imidazo[2,1-b]thiazol-quinoline derivatives were synthesized through a one-pot condensation reaction of 2-chloro-3-formyl-quinoline, isocyanides and various amidines in the presence of catalytic amounts of sulfamic acid-functionalized γ-Fe₂O₃ nanoparticles encapsulated by hydroxyapatite (denoted as [γ-Fe₂O₃-HAp-(CH₂)₃-NHSO₃H]) under solvent-free conditions. A series of N-fused 2-(2-chloro-quinolin-3-yl)-3-aminoimidazole derivatives were obtained in high to excellent yields using a mild and environmentally benign protocol by applying [γ-Fe₂O₃-HAp-(CH₂)₃-NHSO₃H] as an efficient magnetically recoverable Brønsted acid catalyst. It is notable that the catalyst could be easily recovered and reused without any significant loss of its performance and activity.