General procedure for the synthesis of 1,2-bis(4-pyridyl)ethane and tirofiban impurity 90 from 4-methylpyridine: 4-methylpyridine (1.6 g, 17.18 mmol), powdered sulfur (275 mg, 8.59 mmol), and concentrated hydrochloric acid (12 M, 0.48 mL, 5.76 mmol) were mixed, heated to 120 °C and stirred for 24 hours. After completion of the reaction, the mixture was cooled to room temperature and extracted by adding dichloromethane (20 mL) and water. The organic phase was separated and purified by column chromatography (eluent: ethyl acetate/ethylamine = 97/2/1 to 90/7/3) to afford yellow solid 1,2-bis(4-pyridyl)ethane (520 mg, yield: 16%) and 4',4''-(propane-1,2,3-triyl)tripyridine (1.2 g, yield: 25%).
