1: With triethylamine in methanol T=0 - 5°C; 2: With bis(trichloromethyl) carbonate in chloroform T=0°C; 4 h; Further stages.;

carbon disulfide; triethylamine in chloroform

chloroformic acid ethyl ester; triethylamine in chloroform 3.5 h; Ambient temperature; Yield given;

1: aq. NaOH / 24 h / 40 - 45 °C 2: ethyl chloroformate / H2O / 0.67 h / 35 - 40 °C View Scheme

1: 1.) KOH / 1.) dioxane, RT, 30 min., 2.) 4 deg C, 15 h 2: 2.22 g / K2CO3 / dimethylformamide / 1 h / 70 °C 3: 0.350 g / PPE / 1.5 h / 80 °C 4: 84 percent / dimethylformamide / Ambient temperature 5: 88 percent / KOH / 2-methyl-propan-2-ol; H2O / 1 h / 50 - 60 °C View Scheme

1: 1.) KOH / 1.) dioxane, RT, 30 min., 2.) 4 deg C, 15 h 2: 2.22 g / K2CO3 / dimethylformamide / 1 h / 70 °C 3: 0.350 g / PPE / 1.5 h / 80 °C View Scheme

1: 1.) KOH / 1.) dioxane, RT, 30 min., 2.) 4 deg C, 15 h 2: 2.22 g / K2CO3 / dimethylformamide / 1 h / 70 °C 3: 0.350 g / PPE / 1.5 h / 80 °C 4: 84 percent / dimethylformamide / Ambient temperature 5: 88 percent / KOH / 2-methyl-propan-2-ol; H2O / 1 h / 50 - 60 °C 6: 62 percent / KHCO3 / dimethylformamide / 5 h / Ambient temperature View Scheme

1: 1.) KOH / 1.) dioxane, RT, 30 min., 2.) 4 deg C, 15 h 2: 2.22 g / K2CO3 / dimethylformamide / 1 h / 70 °C 3: 0.350 g / PPE / 1.5 h / 80 °C 4: 84 percent / dimethylformamide / Ambient temperature View Scheme

1: 1.) sodium hydride / 1.) THF, RT, 1 h, 2.) THF, RT, 1 h 2: 67 percent / dimethylformamide / 2 h / Ambient temperature 3: diphenyl ether / 0.2 h / 250 °C 4: 90 percent / trifluoromethanesulfonic acid, trifluoroacetic acid, anisole / 2 h / Ambient temperature 5: 1.) sodium / 1.) ethanol, 0 deg C, 1,5 h, 2.) ethanol, RT, 3,5 h 6: 89 percent / conc. sulfuric acid / 1 h / 0 °C 7: sodium hydroxide, water / ethanol / 2 h / Heating 8: 73 percent / pyridine / 2 h / 100 °C View Scheme

1: 1.) sodium hydride / 1.) THF, RT, 1 h, 2.) THF, RT, 1 h 2: 67 percent / dimethylformamide / 2 h / Ambient temperature 3: diphenyl ether / 0.2 h / 250 °C 4: 90 percent / trifluoromethanesulfonic acid, trifluoroacetic acid, anisole / 2 h / Ambient temperature 5: 1.) sodium / 1.) ethanol, 0 deg C, 1,5 h, 2.) ethanol, RT, 3,5 h 6: 89 percent / conc. sulfuric acid / 1 h / 0 °C 7: sodium hydroxide, water / ethanol / 2 h / Heating 8: 73 percent / pyridine / 2 h / 100 °C View Scheme