1: 81 percent / CrO3 / pyridine; CH2Cl2 / 1.5 h / Ambient temperature 2: 1.) 1.6 M n-BuLi / 1.) Et2O, room temp., 3 h; 2.) THF, reflux, 4 h 3: 71 percent / Na, liq. NH3 / tetrahydrofuran / 0.5 h 4: 75 percent / pyridine / 48 h / -20 °C 5: 90 percent / dibenzo-18-crown-6 / acetonitrile / a) room temp., 1 h; b) reflux, 18 h 6: tetrahydrofuran 7: 68 percent / 1 N HCl / Heating View Scheme