1: 64 percent / 60 percent aq. acetic acid / 0.5 h / 98 °C 2: 47 percent / p-toluenesulfonic acid / 1,2-dichloro-ethane / 70 °C 3: 93 percent / Amberlyst A-26 <OH(1-)> anion exchange resin, methanol / 5 h / Ambient temperature View Scheme