167404-32-2

1124-14-7

167404-32-2

1. 4-Bromocyclopropylbenzene (1.5 g, 4.9 mmol) was dissolved in anhydrous THF (30 mL) under nitrogen protection and cooled to -78 °C. Slowly n-butyllithium (1.9 M hexane solution, 5.4 mL, 9.7 mmol) was added and compound E (1.27 g, 6.3 mmol) was added after 45 min of reaction. After 2 hr of reaction, the cold bath was removed and the reaction mixture was allowed to warm slowly to room temperature over 45 min, followed by quenching the reaction with aqueous NH4Cl. EtOAc (30 mL) was added to dilute the reaction mixture and washed sequentially with brine (100 mL × 2). The organic layer was dried over Na2SO4 and concentrated to dryness. The crude product was purified by silica gel column chromatography (25% EtOAc/hexane) to afford compound F (545 mg, 27%). 2. Compound i (120 g, 1.0 mol) was dissolved in CH2Cl2 (1.2 L), HgO (6.0 g, 14.4 mmol) and K2CO3 (24.0 g, 0.17 mol) were added and cooled to -30 °C. Br2 (85.2 g, 1.1 mol) was added dropwise over 10 min and stirred for 4.5 h at -30 °C. The reaction mixture was washed sequentially with H2O (1 L) and brine (1 L) and the organic layer was dried over Na2SO4 and concentrated to dryness. The crude product was distilled under reduced pressure to give compound ii (103.8 g, 52%). 3. Compound ii (6.0 g, 30.5 mmol) was dissolved in anhydrous THF (30 mL) under the protection of nitrogen and cooled to -78 °C. N-butyllithium (1.75 M hexane solution, 17.4 mL, 30.5 mmol) was added slowly and stirred for 20 min before SO2 gas was passed into the reaction for 20 min. Slowly warmed to room temperature, CH2Cl2 (50 mL) and NCS (5.0 g, 37.4 mmol) were added and the reaction was carried out at room temperature overnight. The reaction mixture was washed with brine (100 mL x 2) and the organic layer was dried over Na2SO4 and concentrated to dryness. The crude product was purified by silica gel column chromatography (5% EtOAc/hexane) to afford compound II (3.65 g, 55%). 4. Compound iii (3.0 g, 13.8 mmol) and KF (2.4 g, 41.4 mmol) were added to a round bottom flask with acetone (50 mL) and water (30 mL) and stirred at room temperature overnight. After removing the solvent, CH2Cl2 (40 mL) was added and washed with brine (40 mL). The organic layer was dried over Na2SO4 and concentrated to dryness to give compound E (2.77 g, 100%).