1: 98 percent / benzene; diethyl ether / 3 h / 10 - 15 °C 2: 76 percent / Li, liq. NH3, t-BuOH / tetrahydrofuran / 0.5 h / -55 - -50 °C 3: 92 percent / aq. HCl / acetone / 1 h / 25 °C 4: 91 percent / CrO3, H2SO4 / acetone / 0.17 h / 0 - 5 °C 5: 80.3 percent / TsOH*H2O, formic acid / 7 h / 50 - 60 °C View Scheme