Add thionyl chloride to the water, cool to about 0-5°C, and add cuprous chloride. Fluoboric acid diazonium salt was added to the solution and reacted at 0-5°C overnight. The reaction solution was extracted with dichloromethane, combining the organic layers. The organic layer was washed once with saturated aqueous sodium bicarbonate solution, once with water, and finally once with saturated brine. The product was dried over anhydrous sodium sulfate and filtered, and the filtrate was concentrated to remove methylene chloride to obtain the product pyridine-3-sulfonyl chloride with a yield of 90.7%.
