Dichloromethane → 5-Pyridin-3-yl-thiophene-2-sulfonyl chloride

To a solution of 3-thiophen-2-yl-pyridine (0.355 g, 2.20 mmol) in 15 mL of THF at -78° C. is added n-BuLi (1.44 mL of a 1.6M solution in hexanes, 2.31 mmol). After stirring for 15 min, SO2 gas is bubbled through the solution for 30 min. The solution is then allowed to warm to room temperature and stirred overnight. The solution is concentrated to dryness and the resulting solid is suspended in 20 mL of hexane. Sulfuryl chloride (0.185 mL, 2.31 mmol) is added and the reaction mixture is stirred for 30 min then a small amount of methylene chloride is added and the mixture is stirred for another 30 min. The mixture is then concentrated to dryness and diluted with ethyl acetate and washed with saturated NaHCO3 (aq), water and brine. The organic layer is dried over MgSO4, filtered and concentrated to give a brown solid as the title product (0.452 g, 1.74 mmol) which is used in the subsequent step without further purification.