1: 98 percent / Br2 / CH2Cl2; CCl4 / 3 h / 25 °C 2: 99 percent / NaH / tetrahydrofuran; paraffin / 1.) 0 deg C, 10 min; 0 to 25 deg C, 10 min, 2.) reflux, 2 h 3: 85 percent / p-TsOH, molecular sieves 4 Angstroem / toluene / 4 h / Heating 4: 48 percent / n-BuLi / tetrahydrofuran; hexane / 1.) 0 deg C, 10 min, 2.) reflux, 3 h View Scheme