1: 42 percent / chlorosulfonic acid / 0.33 h / 45 °C 2: 38 percent / KOH / dimethylsulfoxide; H2O / 2.5 h / 120 °C View Scheme

1: bromine / chlorosulfonic acid / 1 h / first in an ice bath then without it 2: bromine / chlorosulfonic acid / 144 h / in the dark; the reagents were added in three portions 3: 55 percent Chromat. / zinc / diethyl ether; acetic acid / 0.75 h / 0 °C / addition of zinc over 20 min at 0 deg C (care!) 4: 94 percent / 0.5 N KOH / tetrahydrofuran / 4.5 h / Ambient temperature View Scheme