1: 92 percent / aq. HCl / acetone / 1 h / 25 °C 2: 91 percent / CrO3, H2SO4 / acetone / 0.17 h / 0 - 5 °C 3: 80.3 percent / TsOH*H2O, formic acid / 7 h / 50 - 60 °C View Scheme