1: CrO3, conc. H2SO4 / H2O; acetone / 5 h / Ambient temperature 2: 78 percent / sodium methoxide / methanol / 4 h / Heating 3: 84 percent / bromine / methanol / 4 h / Ambient temperature 4: 66 percent / KOH / methanol / 1 h / 10 °C / other reagents; other temp.; other reaction time 5: 81 percent / triethylamine / CH2Cl2 / 2 h / 0 - 5 °C View Scheme