2,3-Diaminopyridine → 2-[1-(6-benzyl-4,5-dimethyl-pyridazin-3-yl)-piperidin-4-yl]-1H-imidazo[4,5-b]pyridine

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Reaction Conditions

Reaction Steps

To a solution of 1-(6-benzyl-4,5-dimethyl-pyridazin-3-yl)-piperidine-4-carboxylic acid (compound 26, 50 mg, 0.15 mmol) and 2,3-diaminopyridine (33 mg, 0.30 mmol) in CH2Cl2 (0.5 mL) is added polyphosphoric acid (1 mL). The mixture is concentrated to remove CH2Cl2. After being stirred at 150° C. for 1.5 h, the mixture is cooled to 25° C., diluted with water (10 mL), and basified by 10% aqueous solution of sodium hydroxide to pH˜8. The aqueous solution is extracted with CH2Cl2 (5×15 mL). The combined organic layers are concentrated and purified by HPLC (CH3CN/H2O: 22% 45% with 0.1% TFA) to give 2-[1-(6-benzyl-4,5-dimethyl-pyridazin-3-yl)-piperidin-4-yl]-1H-imidazo[4,5-b]pyridine (33.8 mg, 55%).

Provenance & Evidence