methanesulfonyl chloride; triethylamine in dichloromethane T=-15°C; 1 h;

hydrogenchloride in 1,4-dioxane T=100°C; 6 h;

1: 90.6 percent / NaOMe / methanol / 1.) 1 h, -10 deg C, 2.) 16 h, room temperature 2: 86.4 percent / aq. KOH / ethanol / 1 h 3: 52.4 percent / Heating 4: 76.7 percent / p-TsOH / benzene / 4 h / Heating 5: 1.) n-BuLi / 1.) THF, -78 deg C, 30 min, 2.) THF, 4 h, -78 deg C 6: 20.9 percent / 0.2 N aq. HCl / dioxane / 6 h / 100 °C View Scheme

1: 93.2 percent / p-TsOH / 65 h / Heating 2: 1.) n-BuLi / 1.) THF, hexane, 1 h, -78 deg C, 2.) THF, 4 h, -78 deg C, 2.b) 30 min, room temperature 3: 43.4 percent / 0.2 N aq. HCl / dioxane / 24 h / Ambient temperature 4: 60.7 percent / NEt3, methansulfonsaeurechlorid / CH2Cl2 / 1 h / -15 °C View Scheme

1: 76.7 percent / p-TsOH / benzene / 4 h / Heating 2: 1.) n-BuLi / 1.) THF, -78 deg C, 30 min, 2.) THF, 4 h, -78 deg C 3: 20.9 percent / 0.2 N aq. HCl / dioxane / 6 h / 100 °C View Scheme

1: 1.) n-BuLi / 1.) THF, hexane, 1 h, -78 deg C, 2.) THF, 4 h, -78 deg C, 2.b) 30 min, room temperature 2: 43.4 percent / 0.2 N aq. HCl / dioxane / 24 h / Ambient temperature 3: 60.7 percent / NEt3, methansulfonsaeurechlorid / CH2Cl2 / 1 h / -15 °C View Scheme

1: 43.4 percent / 0.2 N aq. HCl / dioxane / 24 h / Ambient temperature 2: 60.7 percent / NEt3, methansulfonsaeurechlorid / CH2Cl2 / 1 h / -15 °C View Scheme

1: 41 percent / 0.2 N aq. HCl / dioxane / 6 h / 100 °C 2: 60.7 percent / NEt3, methansulfonsaeurechlorid / CH2Cl2 / 1 h / -15 °C View Scheme