[Synthesis]
Step A: 1-Butylcyclopropanesulfonate Cyclopropanesulfonyl chloride (25 g, 178 mmol, 1 equivalent) was dissolved in excess n-BuOH (80 ml), and the reaction mixture was cooled to 0 °C. Pyridine (13.3 ml, 160 mmol, 0.9 equivalent) was then added dropwise. The mixture was slowly heated to room temperature and stirred for 36 hours. The solvent was removed under reduced pressure, and the resulting white solid was dissolved in chloroform. The organic phase was washed with water and brine, dried (MgSO4), and then concentrated to obtain an oil (24.5 g, 77%). Step B: Butyl 1-allylcyclopropane-1-sulfonate Butyl ester In a nitrogen atmosphere at -78°C, butyllithium (150 ml, hexane solution containing 2.5 M butyllithium, 404 mmol) was slowly added to a THF (500 ml) solution of 1-butylcyclopropane sulfonate (60 g, 337 mmol). After stirring for 15 minutes, THF (100 ml) containing allyl iodide (31 ml, 337 mmol) was added. The reaction mixture was stirred at -78°C for 2 hours and then at room temperature for 30 minutes. The evaporator was evaporated under reduced pressure, and the residue was extracted with dichloromethane. The extract was washed with water, dried (MgSO4), filtered, and the solvent was removed. The residue was purified by silica gel column chromatography (eluent: PE/EA = 10:1) to obtain a colorless oil of the title compound (50 g, yield: 68%). Step C: Potassium 1-Allylcyclopropane-1-sulfonate A mixture of dimethyl ether (DME, 350 ml) and water (350 ml) containing butyl 1-allylcyclopropane-1-sulfonate (50 g, 229 mmol) and potassium thiocyanate (23.4 g, 240 mmol) was heated under reflux overnight. The mixture was extracted with ethyl acetate, and the aqueous phase was evaporated under reduced pressure to obtain a crude product, which could be used in the next step without further purification. Step D: 1-Allylcyclopropanesulfonyl chloride A solution of potassium 1-allylcyclopropane-1-sulfonate (44 g, 220 mmol), thionyl chloride (500 ml), and DMF (5 ml) was heated under reflux for 1.5 hours. The eluent was evaporated under reduced pressure, and water was added slowly. The mixture was extracted with ethyl acetate, dried over MgSO₄, filtered, and concentrated under reduced pressure. The residue was purified by silica gel chromatography (eluent: PE/EA = 10:1) to obtain the title compound (33 g, 83%). |