1: 1.) ozone, dimethylsulfide, 2.) sodium borohydride / 1.) CH2Cl2, -78 deg C; 15 min, -20 deg C, 2.) ethanol, 0 deg C, 1h 2: pyridine / 24 h / in a refrigerator 3: 94 percent / sodium iodide / acetone / 4 h / Heating 4: n-BuLi / tetrahydrofuran / 1 h / -78 - 25 °C / variation of nucleophile, time, temperature and solvent View Scheme