Step A: Synthesis of Butyl Cyclopropanesulfonate: Cyclopropanesulfonyl chloride (5 g, 35 mmol, 1 eq.) was dissolved in excess n-butanol (20 mL). The reaction mixture was cooled to -10 °C and pyridine (5.8 mL, 70 mmol, 2 eq.) was added slowly and dropwise. Subsequently, the mixture was gradually warmed to room temperature and stirred overnight. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure. The resulting white solid was dissolved in chloroform (CHCl3), and the organic phase was washed sequentially with water and saturated brine and dried over anhydrous magnesium sulfate (MgSO4). The organic phase was concentrated to give the oily product butyl cyclopropanesulfonate (4.8 g, 24.9 mmol, 71% yield). The product was characterized by 1H NMR (300 MHz, CDCl3): δ 4.25 (t, 2H), 2.46 (m, 1H), 1.74 (m, 2H), 1.45 (m, 2H), 1.25 (dd, 2H), 1.09 (dd, 2H), 0.93 (t, 3H).
