General procedure for the synthesis of 2-(imidazol-2-yl)pyridine from 2-(4,5-dihydro-1H-imidazol-2-yl)pyridine: a generalized method of [Mn(TPP)Cl]-catalyzed dehydrogenation of imidazolines with NaIO4 was used. All reactions were carried out at room temperature and air atmosphere in a 25 mL round bottom flask equipped with a magnetic stir bar. To a solution of CH3CN (5 mL) containing 2-imidazoline (1 mmol) and [Mn(TPP)Cl] (0.05 mmol), a solution of NaIO4 (2 mmol) in H2O (10 mL) was added. The reaction process was monitored by thin layer chromatography (TLC) (eluent: EtOAc/MeOH, 4:1). After completion of the reaction, water (30 mL) was added and the target product imidazole was extracted with CH2Cl2 (2 x 20 mL). After evaporation of the solvent, the imidazole derivative was obtained. The structure of the product was confirmed by infrared spectroscopy (IR) and 1H nuclear magnetic resonance (1H NMR) data.
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